Selective Butene Formation in Direct Ethanol-to-C3+-Olefin Valorization over Zn-Y/Beta and Single-Atom Alloy Composite Catalysts Using in Situ-Generated Hydrogen

pubs.acs.org/acscatalysis

Research Article

Selective Butene Formation in Direct Ethanol-to‑C₃₊-Oleﬁn

Valorization over Zn−Y/Beta and Single-Atom Alloy Composite

Catalysts Using In Situ-Generated Hydrogen

Michael J. Cordon, Junyan Zhang, Stephen C. Purdy, Evan C. Wegener, Kinga A. Unocic,

Lawrence F. Allard, Mingxia Zhou, Rajeev S. Assary, Je ﬀ rey T. Miller, Theodore R. Krause, Fan Lin,

Huamin Wang, A. Jeremy Kropf, Ce Yang, Dongxia Liu, and Zhenglong Li *

Cite This: ACS Catal. 2021, 11, 7193 −7209

Read Online

sı

*

Metrics & More

Article Recommendations

Supporting Information

ACCESS

ABSTRACT: The selective production of C₃₊oleﬁns from renewable

feedstocks, especially via C₁and C₂platform chemicals, is a critical

challenge for obtaining economically viable low-carbon middle-distillate

transportation fuels (i.e., jet and diesel). Here, we report a multifunc-

tional catalyst system composed of Zn−Y/Beta and “single-atom” alloy

(SAA) Pt−Cu/Al₂O₃, which selectively catalyzes ethanol-to-oleﬁn (C₃₊,

ETO) valorization in the absence of cofed hydrogen, forming butenes as

the primary oleﬁn products. Beta zeolites containing predominately

isolated Zn and Y metal sites catalyze ethanol upgrading steps (588 K, 3.1

kPa ethanol, ambient pressure) regardless of cofed hydrogen partial

pressure (0−98.3 kPa H₂), forming butadiene as the primary product

(60% selectivity at an 87% conversion). The Zn−Y/Beta catalyst

possesses site-isolated Zn and Y Lewis acid sites (at ∼7 wt % Y) and Brønsted acidic Y sites, the latter of which have been previously

uncharacterized. A secondary bed of SAA Pt−Cu/Al₂O₃selectively hydrogenates butadiene to butene isomers at a consistent

reaction temperature using hydrogen generated in situ from ethanol to butadiene (ETB) conversion. This unique hydrogenation

reactivity at near-stoichiometric hydrogen and butadiene partial pressures is not observed over monometallic Pt or Cu catalysts,

highlighting these operating conditions as a critical SAA catalyst application area for conjugated diene selective hydrogenation at

high reaction temperatures (>573 K) and low H₂/diene ratios (e.g., 1:1). Single-bed steady-state selective hydrogenation rates,

associated apparent hydrogen and butadiene reaction orders, and density functional theory (DFT) calculations of the Horiuti−

Polanyi reaction mechanisms indicate that the unique butadiene selective hydrogenation reactivity over SAA Pt−Cu/Al₂O₃reﬂects

lower hydrogen scission barriers relative to monometallic Cu surfaces and limited butene binding energies relative to monometallic

Pt surfaces. DFT calculations further indicate the preferential desorption of butene isomers over SAA Pt−Cu(111) and Cu(111)

surfaces, while Pt(111) surfaces favor subsequent butene hydrogenation reactions to form butane over butene desorption events.

Under operating conditions without hydrogen cofeeding, this combination of Zn−Y/Beta and SAA Pt−Cu catalysts can selectively

form butenes (65% butenes, 78% C₃₊selectivity at 94% conversion) and avoid butane formation using only in situ-generated

hydrogen, avoiding costly hydrogen cofeeding requirements that hinder many renewable energy processes.

KEYWORDS: ethanol, butenes, butadiene, selective hydrogenation, catalysis, single-atom alloy, zeolite

accomplished over either Brønsted acid zeolites^6,7or metal

1. INTRODUCTION

oxides⁸⁻¹⁰with limited oleﬁn selectivities due to the formation

Eﬃcient catalytic upgrading of renewable feedstocks into

carbon-neutral transportation fuels remains critically important

for combating CO₂emissions, especially for producing long-

chain (C₈₊) hydrocarbons required for aviation and heavy-duty

of aromatics and paraﬃns,¹¹⁻¹³ethylene, oxygenates, or other

side products including CO₂.^14,15Therefore, a strong need

remains for an approach to selective C₃₊oleﬁn production for

diesel fuels. Bioethanol is a widely produced renewable

feedstock (∼86 million tons per year worldwide in 2018¹)

Received: March 11, 2021

Revised: April 29, 2021

Published: June 4, 2021

that can be valorized into key short-chain (C₃−C₆) oleﬁn

intermediates (e.g., propene,²1-butene, isobutene³), a class of

critical precursors for oligomerization into middle-distillate-

range hydrocarbons⁴and commodity chemical production.⁵

Direct conversion of ethanol to C₃₊oleﬁns is typically

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

7193

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Scheme 1. Proposed ETO Reaction Pathway Composed of ETB and Subsequent Butadiene Selective Hydrogenation to Form

a

Butene Isomers

a

H₂production and consumption events are highlighted in red. An additional ethanol provides the hydrogen source for the MPV reduction of

crotonaldehyde.

a

Scheme 2. Two-Bed Reactor Setup Composed of Independent ETB and Selective Hydrogenation (SH) Catalysts

a

Catalyst beds are in physical contact during reaction, with the distance here shown only to highlight key intermediates passing between catalyst

beds. Components labeled as “others” are products that are not typically observed to change signiﬁcantly by the choice of SH catalyst in the

absence of hydrogen cofeeding. Single-bed ethanol valorization studies were performed over Zn−Y/Beta without an SH catalyst (vide infra Section

3.1), and single-bed selective hydrogenation reactions were performed without an ETB catalyst (vide infra Section 3.3).

economically viable liquid renewable fuel generation without

signiﬁcant carbon losses, especially since carbon conversion

eﬃciency is a primary cost driver for renewable fuel

production.¹⁶

ETB catalysts typically possess multiple kinetically relevant

active sites for dehydrogenation and aldol condensation steps,

which are often derived from transition-metal and oxide

pairings²⁸such as metal-promoted MgO/SiO₂.²⁹⁻³²Zeolites

have also shown promising ETB reactivity through the

combination of Lewis acid sites formed through the

isomorphous substitution of framework Si centers with M⁴⁺

or M⁵⁺heteroatoms and transition-metal sites (e.g., Ag/Zr-

Beta,³³Cu-Ta/Beta,³⁴Zn/Hf-MFI³⁵), utilizing favorable

conﬁnement eﬀects in conjunction with dispersed active sites

to improve desired product selectivities. Recently, rare-earth

metals (e.g., Y) operating as Lewis acid sites within Beta zeolite

microporous environments have been investigated as aldol

condensation active sites and can catalyze the ETB reaction

pathway (603 K) when combined with transition metals (e.g.,

Zn).³⁶This suggests Zn−Y/Beta as an eﬀective ETB catalyst

within the larger ETO reaction pathway¹⁹to produce near-

stoichiometric butadiene and hydrogen partial pressures for

further catalyst upgrading.

Using butadiene as an intermediate, the ETO pathway

requires the selective hydrogenation of butadiene to form

butene. Butadiene selective hydrogenation reaction is generally

studied at lower temperatures (<423 K) and is often

performed with excessive amounts of hydrogen (H₂/BD >

15).³⁷Butane formation can be observed^37,38even at such mild

reaction temperatures and with H₂/BD ratios similar to those

observed in naphtha steam-cracking applications,³⁹situations

where the selective hydrogenation of acetylene to ethylene or

butadiene to butenes is necessary prior to downstream

operations. Traditional butadiene selective hydrogenation

catalysts include Cu/SiO₂,⁴⁰Pd/Al₂O₃,⁴¹and Pt-Ni/Al₂O₃,⁴²

while “single-atom alloy” (SAA)-supported metal catalysts

composed of dilute solid solutions of precious metals (e.g., Pd

or Pt) within transition-metal nanoparticles (e.g., Cu) have

Ethanol conversion to 1,3-butadiene (ETB) is an econom-

ically attractive reaction for selectively generating renewable C₄

monomers that can avoid the above-mentioned side product

formation¹⁷and can serve as an important step toward the

synthesis of butene-rich oleﬁns. Despite debates about the

speciﬁc mechanistic details, the general reaction network of

ETB (Scheme 1) consists of ethanol dehydrogenation, aldol

condensation, Meerwein−Ponndorf−Verley (MPV) reduction,

and dehydration to form 1,3-butadiene (butadiene, BD).¹⁸⁻²⁰

For an ideal reaction resulting in perfect ethanol-to-butadiene

selectivity, stoichiometric amounts of butadiene and hydrogen

are formed due to hydrogen generated from ethanol

dehydrogenation (Scheme 1). However, butadiene is not a

preferred C₄oleﬁn for middle-distillate fuel generation due to

its tendency for increased coke formation.²¹⁻²⁴Therefore, one

attractive approach is to directly utilize this in situ-generated

hydrogen for the selective hydrogenation of butadiene to

butenes without requiring cofed hydrogen, providing a single-

reactor approach for converting ethanol into a butene-rich

oleﬁn stream. Such ethanol-to-C₃₊-oleﬁn (ETO) valorization

without external hydrogen has not been reported in the

literature and oﬀers the beneﬁts of avoiding the operating and

capital costs associated with hydrogen purchase, storage,

downstream separation, and recycling. The grand challenge

of this ETO pathway is designing catalytic materials with active

sites for both high ETB reactivity and high butadiene selective

hydrogenation reactivity while mitigating butene hydrogena-

tion to butanes under stoichiometric hydrogen and butadiene

partial pressures and ETB reaction conditions (e.g., 573−673

K).²⁵⁻²⁷

7194

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

recently been studied as relevant selective hydrogenation

catalysts.^37,43,44Low-temperature (<423 K) butadiene selective

hydrogenation reactivity over Pt−Cu SAA catalysts has been

qualitatively correlated with the formation of hydrogen islands

around Pt centers through hydrogen adsorption, scission, and

subsequent adatom diﬀusion to proximal Cu centers;³⁷

however, their applicability for higher temperatures has not

been investigated and particularly not for near-stoichiometric

hydrogen and butadiene partial pressures.

scanning transmission electron microscopy (HAADF-STEM)

was performed to probe bulk metal distributions for both Zn−

Y/Beta and Al₂O₃-supported metal catalysts with character-

ization details reported in Section S.1.2. Transmission IR

spectra were collected on Zn- and Y-containing zeolite samples

after pyridine adsorption, and the measurement details are also

reported in Section S.1.2.

XAS experiments were performed in transmission mode at

the Zn and Y K edges (9.659 and 17.038 keV, respectively, for

zeolite samples) and at the Pt L₃edge and Cu K edge (11.564

and 8.9789 keV, respectively, for supported metal catalysts) on

the Materials Research Collaborative Access Team (MR-CAT)

bending magnet beamline at the Advanced Photon Source at

Argonne National Laboratory. For samples with low Pt

loading, the Pt L₃edge XAS experiments were performed in

ﬂuorescence mode at the MR-CAT insertion device line, 10-

ID. Detailed sample pretreatment, measurement procedures,

and data analysis methodologies are reported in Section S.1.2.

2.3. Gas-Phase Ethanol Conversion Studies. High

ethanol conversions for the two-bed reactor setup or single-

bed Zn−Y/Beta were measured using a vertically aligned

tubular quartz reactor (0.5″ OD) under ambient pressures.

Catalysts were pelletized, crushed, and sieved to retain particles

within 125 and 180 μm prior to being loaded into the reactor

(Scheme 2). Catalyst beds were placed between quartz wool

beds (Chemglass, 8−15 μm) with typical bed masses of 0.250

g for Zn−Y/Beta in the ﬁrst bed and 0.168 g of the desired

selective hydrogenation catalyst in the second bed, unless

otherwise stated. For single-bed operation, 0.250 g of Zn−Y/

Beta was loaded. Constant catalyst bed temperatures were

measured using a K-type thermocouple (Omega) positioned

within the ﬁrst catalyst bed. Catalysts were heated to 673 K

(0.0833 K s⁻¹) in a ﬂowing He (0.33 cm³s⁻¹, Airgas, UHP,

>99.999%) for 1 h, switched to pure H₂ﬂow (0.42 cm³s⁻¹,

Airgas, UHP, >99.999%) at 673 K for 0.5 h, and then switched

back to ﬂowing He while cooling to 588 K. Catalyst beds were

then exposed to relevant H₂and He gas ﬂow conditions (0.48

Here, this ETO reaction pathway is investigated for the ﬁrst

time using a two-bed reactor setup containing Zn−Y/Beta and

Pt- and/or Cu-containing supported metal catalysts (Scheme

2) to catalyze ethanol to butadiene and subsequent butadiene

selective hydrogenation, respectively, generating C₃₊oleﬁns

from ethanol alone without external hydrogen feeding. Both

catalysts are individually characterized using a suite of

spectroscopy and microscopy techniques including X-ray

absorption spectroscopy (XAS), pyridine-adsorbed trans-

mission IR spectroscopy, and scanning transmission electron

microscopy (STEM). Catalysts are tested in both single-bed

and two-bed conﬁgurations (588 K; Scheme 2) as a function of

cofed hydrogen partial pressures (0−98.3 kPa). Steady-state

reaction rates, apparent reaction order measurements, and

density functional theory (DFT) calculations are employed to

compare selective hydrogenation catalysts (SAA 0.1Pt6Cu/

Al₂O₃, 0.1Pt/Al₂O₃, 2Pt/Al₂O₃, and 6Cu/Al₂O₃) and inves-

tigate the unique kinetic capabilities of Pt−Cu ensemble sites

under near-stoichiometric hydrogen concentrations desired for

ideal ETO operations and negligible butane formation. These

combined experimental and computational results indicate the

ETO catalytic potential of the composite catalyst composed of

Zn−Y/Beta and SAA 0.1Pt6Cu/Al₂O₃utilizing stoichiometric

hydrogen partial pressures formed in situ and eliminating costly

hydrogen cofeeding and corresponding downstream hydrogen

separation and recycle steps in the middle-distillate-range

hydrocarbon generation processes.

2. EXPERIMENTAL METHODS

cm³s⁻¹, P_H= 0−101.3 kPa with balance He, preheated to 453

2

2.1. Catalyst Synthesis. Dealuminated Beta (deAl-Beta)

was obtained using a previously reported procedure,⁴⁵with

details shown in Section S.1.1. Zn−Y/Beta, Zn/Beta, and Y/

Beta samples were synthesized from the deAl-Beta support via

solid-state grinding. In a typical Zn−Y/Beta synthesis, 0.091 g

of zinc nitrate hexahydrate (Sigma-Aldrich, 97%) and 0.345 g

of yttrium nitrate hexahydrate (Sigma-Aldrich, 97%) pre-

cursors were ground with deAl-Beta for 0.25 h. The resulting

solids were heated in a tube furnace to 823 K (0.0167 K s⁻¹)

under airﬂow (10 cm³s⁻¹(g catalyst)⁻¹). Pt- and Cu-

containing supported metal catalysts were synthesized through

incipient wetness impregnation onto a γ-alumina (Al₂O₃)

support (Sinopharm Chemical Reagent Co., Ltd., 98.0%), with

details reported in Section S.1.1.

2.2. Catalyst Characterization. Powder X-ray diﬀraction

(XRD) patterns were measured on a PANalytical X-ray

diﬀractometer using a Cu Kα source (λ = 0.1542 nm, 45 kV,

40 mA). Diﬀraction patterns were collected from 4 to 40° at a

step size of 0.025° and a scan rate of 0.04° s⁻¹. N₂adsorption

isotherms (77 K) were collected using a Quantachrome

Autosorb iQ with detailed analysis information reported in

Section S.1.2. Bulk elemental compositions were measured via

inductively coupled plasma atomic emission spectroscopy

(ICP-AES) performed at Galbraith Laboratories, Inc. Aberra-

tion-corrected high-angle annular dark-ﬁeld imaging from

K). Liquid ethanol (EMD Millipore, >99%) was fed into the

heated gas mixture via a syringe pump (KD Scientiﬁc Legato

180) and vaporized prior to interacting with the catalyst beds.

No background reactions were detectable using only quartz

wool within the reactor. Products were separated and analyzed

via gas chromatography (Agilent 7820A) using a HP-PLOT-Q

column (30 m, 0.32 mm diameter, 20 μm ﬁlm) and both a

ﬂame ionization detector and a thermal conductivity detector.

Product identiﬁcation was performed using a gas chromato-

graph (GC, Agilent 6850) and mass spectrometer (Agilent

5975C) with known standards. The carbon balance for all of

the reactions is typically 92−96%. Deﬁnitions of ethanol

conversions, product yields, and selectivities are reported in

Section S.1.3.

Reaction rates for Zn- and Y-containing samples were

measured in the same setup as the high conversion

experiments. Catalyst weight, ethanol ﬂow rates, and carrier

gas ﬂow rates were adjusted to maintain a diﬀerential

conversion regime with ethanol conversion <5%. Typically,

0.05 g of catalyst was pelletized, crushed, and sieved to retain

particles within 125 and 180 μm and then diluted with 0.80 g

silicon carbide (SiC, Alfa Aesar, 120 grit). Ethanol ﬂow rates

were controlled via a syringe pump (1.07 mL h⁻¹) into Ar

(1.67 cm³s⁻¹, 588 K, 163 kPa total pressure).

7195

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figure 1. (A) Product formation rates from ethanol valorization (11.1 kPa ethanol in balance Ar, 163 kPa total pressure, 543 K, WSHV = 15.9 h⁻¹

over Zn/Beta and Zn−Y/Beta and 8.0 h⁻¹over Y/Beta, <5% conversion) to form butadiene (green), butenes (blue), ethylene (orange),

acetaldehyde (gray), and diethyl ether (purple) and (B) associated conversions (black) and product selectivities over Zn−Y/Beta, Zn/Beta, and Y/

Beta catalysts.

2.4. Butadiene Selective Hydrogenation Kinetic

Studies. Butadiene selective hydrogenation rates were

measured using a similar reactor setup as used for ethanol

upgrading but with only a single catalyst bed. Typically, 0.05 g

of catalyst (pelletized, crushed, and sieved to 125−180 μm)

was mixed with 0.70 g of SiC (Alfa Aesar, 120 grit) prior to

being loaded into the reactor between two quartz wool plugs.

Catalyst beds were pretreated to 673 K (0.0833 K s⁻¹) in 10%

H₂in balance Ar (UHP, Airgas, >99.999%, 0.83 cm³s⁻¹) for 1

h prior to cooling to 588 K. Gas ﬂow rates of H₂and Ar were

adjusted and butadiene (BD, Airgas, 3%, balance N₂) and a

methane internal standard (CH₄, Airgas, 1%, balance Ar) were

introduced to obtain a reference condition (F_total= 1.67 cm³

s⁻¹, P_H= 1.51 kPa, P_BD= 1.51 kPa, P_CH= 0.20 kPa).

Transient behavior was observed for at least 12−18 h over

each selective hydrogenation catalyst to provide suﬃcient data

to ﬁt initial and steady-state rate measurements at initial and

near-inﬁnite times on stream. Initial and steady-state rates

represent modeled regressions of transient proﬁles from a two-

site model with better ﬁtting results than a one-site model as

expected for complex materials with multiple active site

conﬁgurations. Reaction orders reﬂect rate measurements

after catalyst stabilization at H₂partial pressures between

0.76 and 2.99 kPa and butadiene partial pressures between

0.51 and 2.53 kPa, with reported rates reﬂecting the average of

1 h of data collection (3 data points, <5% deactivation during

kinetic measurements at each H₂/BD ratio). Flow composi-

tions were returned to the initial reference condition after each

reaction order measurement to ensure the reclamation of

steady-state reference rates. Product quantiﬁcation was

performed through an identical procedure to the ethanol

conversion setup prior to normalization by the methane

internal standard.

in face-centered cubic transition-metal nanoparticles⁵¹and was

represented by a ﬁve-layer slab (3 × 3). Studied surfaces

include a Cu(111) surface, a Pt(111) surface, and an SAA Pt−

Cu(111) surface, the latter of which reﬂects the substitution of

a single Pt atom into the Cu(111) surface. A 20 Å vacuum was

added between the two neighboring successive slabs for all of

the simulated surfaces. A Monkhorst−Pack k-point mesh⁵²of 3

× 3 × 1 (400 eV cutoﬀ energy) was used during structure

optimization, and the optimized structures were obtained when

changes in force were less than 0.02 eV Å⁻¹. The most stable

adsorption conﬁgurations reﬂect the lowest-energy structures

from several adsorption conﬁgurations. Transition states for

each reaction step were determined based on combined

climbing image nudged elastic band (CI-NEB)⁵³and dimer

methods.⁵⁴The vibrational frequencies of adsorbed butadiene,

1-butene, cis-2-butene, and trans-2-butene were computed on

each surface to estimate the thermodynamic properties. Only

the adsorbates were allowed to relax to accelerate the

vibrational frequency calculations. The binding energies

(BEs) of reaction intermediates, including butadiene, H₂, H

adatom, 1-butene, cis-2-butene, and trans-2-butene, were

calculated based on eq 1

2

4

*

BE_A*= E_A*− E − E_A

(1)

Here, BE_A*is the total energy of adsorbate species A, E* is the

total energy of the clean surfaces, and E_Ais the total energy of

gas A (e.g., butadiene, H₂, 1-butene, cis-2-butene, and trans-2-

butene). For gaseous H adatoms, the E_Awas approximated as

half of the total energy of H₂gas.

3. RESULTS

3.1. Ethanol Upgrading over Bimetallic Zn−Y/Beta. X-

ray diﬀraction patterns and micropore volumes determined

from N₂adsorption isotherms (77 K) collected on zeolite

samples after metal incorporation are consistent with the Beta

topology (Figures S.1 and S.2 and Table S.1). Inductively

coupled plasma atomic emission spectroscopy (ICP-AES)

measurements show no detectable Al presence within the Beta

support (Si/Al > 1300) and therefore negligible Al Brønsted

acid site densities. Zn and Y ICP-AES measurements indicate

2.5. DFT Methods. All of the calculations were carried out

using the Vienna ab initio simulation package (VASP)^46,47with

the van der Waals interaction (DFT-D3 correction)^48,49

included. Exchange−correlation energies were described

using the generalized gradient approximation (GGA) Per-

dew−Burke−Ernzerhof (PBE) functional.⁵⁰The closed-

packed (111) facet was generated to reﬂect a common facet

7196

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figure 2. XAS spectra collected on Zn- and Y-containing samples after pretreatment in ﬂowing He to 673 K, including Zn K edge XANES (A) and

EXAFS (B, k²weightings) spectra and Y K edge XANES (C) and EXAFS (D, k²weightings).

bulk metal loadings of 2.0 and 7.3 wt %, respectively, on

monometallic samples and are similar for Zn−Y/β (1.7 and 7.0

wt % Zn and Y, respectively; Table S.1).

formation are used to compare Zn−Y/Beta and Zn/Beta.

Measured dehydrogenation rates over Zn−Y/Beta and Zn/

Beta are similar, normalized per gram or per mol of Zn (1.0 ×

10⁻²and 1.1 × 10⁻²mol dehydrogenated EtOH (mol Zn)⁻¹

s⁻¹, respectively), which is consistent with negligible ethanol

dehydrogenation reactivity over Y centers in Y/Beta (1.2 ×

10⁻⁵mol EtOH (mol Y)⁻¹s⁻¹). Butadiene formation rates

over Zn−Y/Beta are 13× higher than over Zn/Beta at similar

Zn loadings, suggesting the catalytic need for Y sites or Zn−Y

ensemble sites for catalyzing the aldol condensation, MPV

reduction, and dehydration reaction network that converts two

acetaldehyde molecules into butadiene.

To probe the local environment of Zn and Y centers, XAS

measurements and HAADF-STEM analyses were performed

on the Zn- and Y-containing zeolite samples. Figure 2 shows X-

ray absorption near-edge structure (XANES) and extended X-

ray absorption ﬁne structure (EXAFS) spectra of the fresh Zn-

and Y-containing samples after dehydration at 673 K (EXAFS

ﬁts and Supporting Information in Tables S.2 and S.3 and

Figure 1 shows ethanol conversion rates measured over Zn−

Y/Beta, Zn/Beta, and Y/Beta catalysts (11.1 kPa EtOH in

balance Ar, 163 kPa total pressure, 543 K, weight hourly space

velocity (WHSV) = 15.9 g EtOH (g catalyst)⁻¹h⁻¹over Zn/

Beta and Zn−Y/Beta and WHSV = 8.0 g EtOH (g catalyst)⁻¹

h⁻¹over Y/Beta, <5% conversion) to probe the catalytic

necessity of both Zn and Y species. Zn/Beta predominantly

forms acetaldehyde, a key reactant for aldol condensation into

crotonaldehyde and subsequent butadiene formation (Scheme

1). Y centers within Y/Beta yield ethylene and diethyl ether

predominantly, indicating negligible dehydrogenation reactiv-

ity under these conditions and corroborating previous

observations at 623 K.¹⁹As the incorporation of both Zn

and Y centers produces quantiﬁable amounts of butadiene and

butenes over Zn−Y/Beta, apparent ethanol dehydrogenation

rates reﬂecting combined acetaldehyde, butadiene, and butene

7197

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figures S.3 −S.6). At the Zn K edge, the XANES edge energies

of Zn/Beta (9.6639 keV) and Zn−Y/Beta (9.6642 keV) are

close to that of ZnO (9.6633 keV), indicating predominantly

Zn²⁺centers in all three materials. The Zn K edge EXAFS

spectrum (Figure 2B) of ZnO shows two primary peaks

centered at 1.6 and 2.9 Å (phase-uncorrected distance)

reﬂecting Zn−O ﬁrst-shell scattering and Zn−Zn second-

shell scattering, respectively. A Zn−O scattering peak centered

at 1.5 Å (phase-uncorrected distance) is observed in the

EXAFS spectra of Zn/Beta and Zn−Y/Beta. Fitting gives

coordination numbers close to 4 at a similar distance to the

Zn−O bond in ZnO. Zn−Zn scattering is not observed in the

EXAFS of Zn/Beta or Zn−Y/Beta, indicating that Zn centers

are highly dispersed on the Beta supports and that large Zn

oxide nanoparticles are absent.

At the Y K edge, the XANES edge energies of Y/Beta

(17.0402 keV), Zn−Y/Beta (17.0399 keV), and Y₂O₃

(17.0402 keV) are all similar, indicating Y in the 3+ oxidation

state on all three materials. The EXAFS spectrum (Figure 2D)

of Y₂O₃shows scattering from Y−O at 1.8 Å (phase-

uncorrected distance) as well as two prominent peaks from

2.6 to 4.2 Å (phase-uncorrected distance), reﬂecting single and

multiple scatterings from Y in the second and third

coordination spheres. In contrast, Y/Beta and Zn−Y/Beta

have a Y−O peak with much lower intensity and a small

second-shell peak at a shorter distance compared to Y₂O₃.

Fitting the ﬁrst shell gave a coordination number of close to 4

for both catalysts with a distorted environment having two

short and two long Y−O bonds. In contrast, Y₂O₃is octahedral

as reﬂected in a much higher Y−O peak amplitude (Figure

2D). The lack of higher Y shell peaks on Y/Beta and Zn−Y/

Beta indicates the absence of signiﬁcant YO_xnanoparticles

occluded on the zeolite domains despite the relatively high Y

loading. HAADF-STEM images of Zn−Y/Beta (Figure S.7)

support the conclusions from EXAFS and show no discernible

Zn or Y oxide nanoparticles, suggesting the highly dispersed

nature of both Zn and Y on the zeolite support. Taken

together, monometallic Zn/Beta and Y/Beta and bimetallic

Zn−Y/Beta each consist of predominately isolated Zn²⁺and

Y³⁺centers on the Beta zeolite support.

The Lewis or Brønsted acidic properties of the dispersed Zn

and Y sites were probed using transmission IR. Figure 3

displays transmission IR spectra collected after pyridine

saturation of Zn−Y/Beta, Zn/Beta, Y/Beta, and deAl-Beta

materials. The spectrum collected after pyridine adsorption

onto the deAl-Beta parent material shows only minor peaks,

while adsorption onto Zn/Beta and Y/Beta gives rise to peaks

at 1491 and 1575 cm⁻¹and two distinct peaks each (1452 and

1612 cm⁻¹for Zn, 1445 and 1606 cm⁻¹for Y), reﬂecting

pyridine adsorbed onto Zn and Y sites, respectively. The four

distinct peaks match peaks for pyridine adsorption onto ZnO⁵⁵

and Y₂O₃,⁵⁶reﬂecting pyridine adsorbed onto Lewis acid sites.

These peaks centered around 1450 and 1610 cm⁻¹and the

shared peak centered at 1491 cm⁻¹reﬂect perturbed pyridine

deformation modes upon adsorption onto Lewis acid sites,⁵⁷

while the peak centered at 1575 cm⁻¹corresponds to

hydrogen-bonded pyridine.⁵⁸Peaks reﬂecting pyridine adsorp-

tion onto Zn sites in Zn/Beta match previous observations of

pyridine-bound Lewis acidic Zn species within the Beta zeolite

framework⁵⁹and, by extension, the peaks reﬂecting pyridine

adsorption onto Y sites in Y/Beta correspond to Lewis acidic Y

sites, as recently suggested elsewhere.⁶⁰The peaks centered at

1545 and 1637 cm⁻¹observed on Y-containing sites are

Figure 3. Transmission IR spectra on deAl-Beta and Zn- and Y-

containing Beta samples after pyridine saturation at 393 K.

reminiscent of previously assigned peaks for protonated

pyridine species⁶¹derived from interactions with Brønsted

acid sites. As these peaks reﬂecting protonated pyridine are

absent from the deAl-Beta parent spectra, these peaks reﬂect

the presence of pyridine-bound Brønsted acidic Y sites on both

Y/Beta and Zn−Y/Beta. This would be consistent with Y³⁺

centers embedded within the zeolitic framework that require a

nearby proton for charge balance. The spectrum collected on

the Zn−Y/Beta sample after pyridine saturation has all six

distinct peaks indicative of pyridine adsorbed onto Lewis acidic

Zn and Y species and Brønsted acidic Y sites as expected for a

sample containing both metals, yet the quantiﬁcation of

distinct Zn and Y active site densities is not possible due to the

lack of integrated molar extinction coeﬃcients (integrated peak

area ratios and total acid site densities from NH₃−TPD

measurements are given in Table S.4 with NH₃−TPD spectra

shown in Figure S.8). However, taking these observations

together with the XAS analyses, the Zn- and Y-containing Beta

zeolites studied here are composed of predominantly site-

isolated metal centers despite high metal loadings and consist

of Lewis acidic Zn sites and both Lewis and Brønsted acidic Y

sites, respectively. Notably, Brønsted acidic Y sites have not

been previously reported for Y sites within a zeolitic

framework.

This combination of Zn and Y sites on the Beta support is

capable of catalyzing ethanol valorization to butadiene and

butenes even in low conversion rate measurements (Figure 1),

suggesting its catalytic ETB potential at more industrially

relevant conversions. High conversion measurements from

pseudo-steady-state ethanol conversion over Zn−Y/Beta (3.1

kPa EtOH, balance He, 588 K, WHSV = 0.43 h⁻¹) show 87%

ethanol conversion with 60 and 14% selectivities to butadiene

and butene isomers (1-butene, cis-2-butene, and trans-2-

butene), respectively, along with smaller concentrations (3−

8%) of ethylene, propene, acetaldehyde, diethyl ether, and C₅₊

oleﬁns (product distribution and selectivity given in Figures

S.9 and S.10, respectively). Given the high butadiene

selectivity, the possibility of using Zn−Y/Beta as a single

ETO catalyst for both ETB and subsequent butadiene selective

hydrogenation to butene isomers was investigated by cofeeding

7198

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

hydrogen. Hydrogen cofeeding with ethanol (0−98.3 kPa H₂,

3.1 kPa EtOH in balance He) does not show discernible

diﬀerences in either the overall ethanol conversion or the

associated product distribution even when the carrier gas is

solely composed of hydrogen (Figure S.9). These high

conversion measurements suggest that Zn−Y/Beta alone

cannot eﬃciently catalyze the full ETO pathway (Scheme 1)

regardless of hydrogen partial pressure, necessitating additional

active sites for butadiene selective hydrogenation. These

selective hydrogenation active sites must catalyze selective

hydrogenation events at hydrogen and butadiene molar ratios,

reﬂecting gas compositions after interactions with Zn−Y/Beta

(∼1−65 H₂/BD ratio) and ideally maintaining high selective

hydrogenation reactivities at stoichiometric H₂/BD ratios, as

discussed next using SAA Pt−Cu-supported metal catalysts.

3.2. Multifunctional Catalyst Systems for ETO.

Supported metal catalysts consisting of dilute solid solutions

of precious metals (e.g., Pt, Pd) within larger domains of

transition metal centers (e.g., Cu) have catalytically relevant

reactivities for both low-temperature (<423 K) hydrogena-

tion^37,44and high-temperature (>573 K) dehydrogenation

reactions,⁶²suggesting that these materials may be relevant

butadiene selective hydrogenation catalysts at increased

reaction temperatures (>573 K). The selective hydrogenation

capabilities of these materials at ETB temperatures (>573 K)

are currently unknown though, and potential reaction concerns

include butane formation through complete butadiene hydro-

genation, minimal hydrogen coverages due to rapid hydrogen

desorption at higher temperatures, and limited reactivity at low

or stoichiometric H₂/BD ratios. To probe the usefulness of

SAA Pt−Cu materials as butadiene selective hydrogenation

catalysts within the proposed ETO reaction network (Scheme

1), hydrogen scission barriers, adsorption energies of relevant

butadiene, oleﬁn, and hydrogen surface species, and metal d-

band centers were calculated from DFT over Cu(111),

Pt(111), and Pt−Cu ensemble sites (reﬂecting a single Pt

site replacement into a Cu(111) surface) and are listed in

Table 1 (representative DFT images in Figure S.11).

over Pt centers in SAA materials are energetically stabilized to

similar extents on both Pt and Cu centers and, given low

diﬀusion barriers to and from neighboring Cu sites, suggest the

ready generation of hydrogen islands^37,63for utilization during

hydrogenation reactions. These minimal hydrogen scission

barriers are similar (0.05−0.06 eV) on Pt centers in Pt(111)

and Pt−Cu(111) ensemble sites, indicating that Pt centers can

eﬃciently catalyze the formation of hydrogen adatom species

necessary for most hydrogenation reaction mechanisms

regardless of Pt or Cu neighbors.

Both butadiene and butene isomer adsorption energies

decrease with decreasing d-band centers on all three

investigated surfaces, as expected for oleﬁn adsorption onto

transition metals.⁶⁴Butadiene adsorption is stronger on all

catalytic surfaces (by −0.3 to −1.1 eV) than investigated

butene surface species, presumably due to favorable binding

interactions for both CC bonds as butadiene adsorbs ﬂat

across multiple surface atoms in the absence of other nearby

bound molecules (Figure S.11). This adsorption conﬁguration

has previously been observed both computationally⁴⁴and

through sum frequency generation vibrational spectroscopy

measurements.⁶⁵Butadiene adsorption modes oppose those of

butene isomers composed of one CC bond coordinated to

surface sites and alkyl chain(s) raised oﬀ the surface, eﬀectively

yielding decreased butene adsorption strengths relative to

butadiene. Adsorption energies indicate more stable adsorption

on Pt(111) sites relative to Cu(111) for butadiene, butene

isomers, and hydrogen adatoms and are much more

pronounced for butadiene (∼−1.7 eV) and butene isomers

(∼−1.1 eV), indicating Pt centers as preferential oleﬁn binding

sites. These signiﬁcantly stronger adsorption interactions may

interfere with hydrogen adsorption and scission events over

Pt(111) centers despite having minimal hydrogen scission

barriers (0.05 eV) relative to those over Cu(111) (0.34 eV).

However, Pt sites within the SAA Pt−Cu(111) surface bind

butadiene more strongly (by ∼−0.4 eV) relative to Cu(111)

but more weakly (by ∼1.4 eV) relative to Pt(111) without

signiﬁcant changes in hydrogen adsorption strengths and

scission barriers, potentially balancing butadiene adsorption

with hydrogen adatom formation steps. Taking together the

adsorption energies and hydrogen scission barriers, Pt−Cu

ensemble sites preferentially adsorb butadiene and butene

isomers relative to hydrogen intermediates due to the presence

of Pt, limit butadiene adsorption strength through weaker

interactions with neighboring Cu atoms relative to Pt

neighbors seen on Pt(111), and maintain minimal hydrogen

scission barriers, suggesting that Pt−Cu SAA materials may be

relevant catalyst candidates for high-temperature (588 K)

butadiene selective hydrogenation.

Adsorption energies for all species investigated here are

strongest on Pt(111) surfaces and weakest on Cu(111)

surfaces. Similar hydrogen adatom adsorption energies onto

Cu(111) and SAA Pt−Cu(111) surfaces indicate that

hydrogen adatoms formed through hydrogen scission reactions

Table 1. DFT-Calculated Binding Energies (0 K) for

Butadiene, Hydrogen, and Butene Isomers onto Pt(111),

Cu(111), and SAA Pt−Cu(111) Dilute Solid Solution

Surfaces, Hydrogen Scission Barriers, and Pt and Cu d-Band

Centers

Guided by these computational observations, SAA

0.1Pt6Cu/Al₂O₃and related supported metal catalysts

containing Pt or Cu alone (0.1Pt/Al₂O₃, 2Pt/Al₂O₃, and

6Cu/Al₂O₃) were synthesized via incipient wetness impregna-

tion (IWI) of metal nitrate precursors onto a γ-alumina

support for use as catalyst candidates for butadiene selective

hydrogenation at relevant ETO conditions. ICP-AES results

indicate bulk metal compositions that match nominal IWI

solution concentrations on both monometallic materials (0.1%

Pt, 1.7% Pt, and 5.5% Cu on 0.1Pt/Al₂O₃, 2Pt/Al₂O₃, and

6Cu/Al₂O₃, respectively) and bimetallic 0.1Pt6Cu/Al₂O₃(0.1

and 5.9 wt % Pt and Cu, respectively). This equates to a 180:1

Cu/Pt molar ratio on 0.1Pt6Cu/Al₂O₃, indicating the potential

for dilute solid solutions of Pt within Cu domains. HAADF-

Compound

Cu(111) Pt(111) SAA Pt−Cu(111)

Binding

butadiene

H₂

H_adatom

1-butene

cis-2-butene

trans-2-butene

−1.27

−0.06

−0.35

−0.80

−0.74

−0.67

0.34

−2.93

−0.09

−0.58

−1.87

−1.82

−1.80

0.05

−1.52

−0.06

−0.38

−1.21

−1.17

−1.13

0.06

Energies (eV)

H₂Scission

Barriers (eV)

Cu d-band

Centers (eV)

Pt d-band

Centers (eV)

−2.23

−2.22

−2.06

−2.03

7199

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figure 4. XANES and EXAFS spectra including Pt L₃edge XANES (A) and EXAFS (B, k²weightings) spectra and Cu K edge XANES (C) and

EXAFS (D, k²weightings) collected on Pt- and Cu-containing supported metal samples. Samples were pretreated at 673 K (5 K min⁻¹) in ﬂowing

H₂and then cooled to room temperature in He prior to collecting XAS spectra.

STEM measurements show primarily isolated Pt centers

scattered throughout Cu domains, but Pt nanoparticles are

not observed (Figure S.12), suggesting the intimate mixing of

Pt and Cu species. In contrast, HAADF-STEM images of

0.1Pt/Al₂O₃and 2Pt/Al₂O₃show both isolated Pt centers and

Pt nanoparticles with higher Pt loadings correlating with

increased densities of Pt nanoparticles. HAADF-STEM images

of 0.1Pt6Cu/Al₂O₃and 6Cu/Al₂O₃suggest similar particle size

distributions with average particle sizes of 1−3 nm (Figure

S.12).

XAS measurements were performed at the Pt L₃and Cu K

edges to characterize the local structures of Pt and Cu in these

materials, as seen in Figure 4. XANES edge energies,

coordination numbers, and EXAFS ﬁtting parameters for Pt-

and Cu-containing materials are listed in Tables S.5 and S.6

and Figures S.13 −S.17. XANES spectra collected at the Pt L₃

edge on 0.1Pt6Cu/Al₂O₃after reduction at 673 K show a 0.4

eV edge energy increase over Pt foil and a concomitant

decrease in white line intensity, consistent with platinum

alloys. The corresponding EXAFS spectrum collected on

0.1Pt6Cu/Al₂O₃shows only a single R space peak, contrasting

the 3 R space peaks of the Pt foil reﬂecting ﬁrst-shell Pt−Pt

scattering. Based on the STEM analysis and the catalyst

composition, the spectrum was modeled using a Pt−Cu

scattering path. Fitting gives a coordination number of 8 at a

bond distance of 2.56 Å (Table S.6). This result shows that the

local environment of platinum in 0.1Pt6Cu/Al₂O₃consists

exclusively of copper. Additionally, the Pt−Cu bond distance is

equal to that of the Cu−Cu bond distance in pure copper,

which would be expected in a dilute solid solution alloy

following Vegard’s law. EXAFS ﬁts of the spectra collected on

0.1Pt/Al₂O₃and 2Pt/Al₂O₃also have unﬁlled ﬁrst-coordina-

tion spheres with 7.7 and 6.9 Pt neighbors, respectively.

Consistent with the small particle sizes suggested by the

coordination numbers, the Pt−Pt bond distances in 0.1Pt/

Al₂O₃and 2Pt/Al₂O₃are contracted to 2.70 and 2.68 Å,

7200

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figure 5. (A−D) Ethanol upgrading product distributions obtained through the two-bed catalytic system composed of Zn−Y/Beta followed by Pt-

and/or Cu-containing supported metal catalysts as a function of cofed hydrogen partial pressure at the reactor inlet (3.1 kPa EtOH, 0 (∼1 H₂/BD

ratio), 17.2 (∼12 H₂/BD), 50.7 (∼34 H₂/BD), or 98.3 (∼65 H₂/BD) kPa H₂in balance He, 588 K, 0.26 h⁻¹WHSV with respect to the two beds,

0.43 h⁻¹with respect to Zn−Y/Beta alone). Product distributions measured over 0.1Pt6Cu/Al₂O₃-PM reﬂect a physical mixture of Zn−Y/Beta and

0.1Pt6Cu/Al₂O₃into a single catalyst bed. Residual product distribution percentages reﬂect the remaining ethanol at a sub-100% conversion. Errors

in product distributions are 15% under these conditions. (E−H) Corresponding diﬀerences in observed product yields as a function of secondary

catalyst selection at each cofed hydrogen partial pressure. Diﬀerences reﬂect product yield percentages (normalized by ethanol conversion)

between each two-bed catalyst setup and the corresponding single-bed product stream over Zn−Y/Beta alone.

respectively, whereas bulk Pt has a Pt−Pt bond distance of

2.77 Å. EXAFS ﬁts (Figures S.16 and S.17) require Pt−O

scattering paths on both 0.1Pt/Al₂O₃and 2Pt/Al₂O₃(1.99 and

1.97 Å, respectively), indicating a subset of nonreduced Pt

sites. Pt−O scattering in the EXAFS is reﬂected in the XANES

as an increase in the edge energy and white line intensity

relative to the Pt foil (0.2−0.5 eV) and is suspected to

correlate with isolated Pt sites observed in STEM images

(Figure S.12) that cannot be readily reduced under the

conditions studied here.

XAS measurements collected at the Cu K edge on

0.1Pt6Cu/Al₂O₃and 6Cu/Al₂O₃describe the local environ-

ment of Cu centers within nanoparticles. Fits of single-shell

Cu−Cu scattering paths indicate coordination numbers of 7.3

and 7.2 on 0.1Pt6Cu/Al₂O₃and 6Cu/Al₂O₃, respectively, and

equivalent Cu−Cu bond lengths. This suggests similar metal

nanoparticle sizes between the two samples and, by extension,

similar bulk surface Cu site distributions. Coordination

numbers for Cu (7.3) and Pt (8) on 0.1Pt6Cu/Al₂O₃are

also similar as expected for metal centers evenly distributed

throughout occluded nanoparticles. These observations from

STEM and XAS suggest the formation of alloyed Pt−Cu

nanoparticles with single-site Pt centers distributed within the

Cu domains.

The catalytic capabilities of the SAA 0.1Pt6Cu/Al₂O₃

catalyst and the monometallic 0.1Pt/Al₂O₃, 2Pt/Al₂O₃, and

6Cu/Al₂O₃control materials were studied in conjunction with

Zn−Y/Beta for catalyzing the complete ETO reaction network

using a layered two-bed setup (Scheme 2), a strategy

commonly used to develop multifunctional catalysts for a

variety of reactions such as the Fischer−Tropsch synthesis of

syngas to liquid fuels⁶⁶or light oleﬁns.⁶⁷Figure 5 depicts

ethanol conversions and associated product distributions at 0,

17.2, 50.7, and 98.3 kPa of H₂(3.1 kPa EtOH in balance He,

588 K; more detailed product distributions and product

selectivities are shown in Figures S.18 −S.29) over the two-bed

catalyst system composed of Zn−Y/Beta and a selective

hydrogenation catalyst. Figure 5E−H also depicts product

yield diﬀerence plots normalized by ethanol conversion at each

measured hydrogen partial pressure to highlight product

distribution diﬀerences between each selective hydrogenation

catalyst relative to Zn−Y/Beta alone. Here, 17.2 kPa of cofed

hydrogen reﬂects similar hydrogen partial pressures for

acetylene selective hydrogenation within steam-cracking

product streams³⁹and low-temperature (313−383 K)

7201

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

butadiene hydrogenation studies over Cu and SAA Pt−Cu

catalysts.³⁷Product distributions formed at 588 K are

composed of a mix of butadiene, butenes (1-butene, trans-2-

butene, cis-2-butene), C_3,5+oleﬁns (predominantly propene,

pentenes, and hexenes), oxygenates (acetaldehyde and diethyl

ether), and other short-chain hydrocarbons (methane, ethane,

ethylene, and propane). Ethanol conversions are consistent

(above 80%) at all cofed hydrogen partial pressures and are

primarily due to interactions between ethanol and Zn−Y/Beta

(Figure S.9).

98.3 kPa hydrogen. Therefore, Pt centers within the Pt−Cu

domains are critical for butadiene selective hydrogenation at

low hydrogen and butadiene ratios characteristic of ETB outlet

streams (∼1.5 kPa each) and are primarily responsible for

complete butadiene conversion even at 17.2 kPa of cofed

hydrogen, catalyzing the ﬁnal reaction steps of the ETO

pathway (Scheme 2).

The combination of the bimetallic Zn−Y/Beta composed of

at least three distinctive active site types with the bimetallic

SAA 0.1Pt6Cu/Al₂O₃catalyst capable of catalyzing high-

temperature hydrogenation reaction at near-stoichiometric

hydrogen and butadiene partial pressures yields a butene-rich

C₃₊oleﬁn stream. These observations regarding the site and

structural properties of both catalysts, as well as the high

conversion product distributions, provide signiﬁcant evidence

of the potential industrial viability of the ETO pathway,

yielding desirable oleﬁn precursors for applications including

jet fuel production. To further probe the reactivities of these

hydrogenation catalysts, single-bed butadiene selective hydro-

genation kinetic measurements over Pt- and Cu-containing

catalysts are combined with DFT calculations to correlate the

unique catalytic behavior of alloyed Pt−Cu active site

ensembles with the observed product distributions in the

two-bed ETO measurements over 0.1Pt6Cu/Al₂O₃at the near-

stoichiometric H₂/BD ratio (Figure 5A).

3.3. Butadiene Selective Hydrogenation over Mono-

metallic and SAA Pt- and Cu-Containing Catalysts.

Butadiene hydrogenation rates obtained over SAA 0.1Pt6Cu/

Al₂O₃, 0.1Pt/Al₂O₃, 6Cu/Al₂O₃, and 2Pt/Al₂O₃catalysts were

measured at similar hydrogen and butadiene partial pressures

to those expected under high conversion ETB operations. With

3.1 kPa ethanol, an ETB reaction pathway with complete

ethanol conversion and perfect butadiene formation selectivity

generates a maximum of 1.55 kPa each of hydrogen and

butadiene (Scheme 1). Steady-state butene formation rates per

gram of catalyst (588 K, 1.51 kPa H₂, 1.51 kPa BD, 0.20 kPa

CH₄, SV_total= 100 cm³s⁻¹(g catalyst)⁻¹) over SAA 0.1Pt6Cu/

Al₂O₃are approximately 20×, 3×, and 0.6× higher than rates

over 0.1Pt/Al₂O₃, 6Cu/Al₂O₃, and 2Pt/Al₂O₃, respectively

(Table S.7), while reaction rates measured on the γ-alumina

support alone are not detectable (<10⁻⁷mol butenes (g

catalyst)⁻¹s⁻¹). Therefore, butadiene selective hydrogenation

events are catalyzed by both Cu and Pt sites. These results are

consistent with the observations from ETO experiments

(Figure 5A), where signiﬁcantly higher butene formation was

observed over SAA without hydrogen cofeeding when

compared with 0.1Pt/Al₂O₃or 6Cu/Al₂O₃. Selective hydro-

genation rates (per gram catalyst) over 0.1Pt6Cu/Al₂O₃are

slightly lower than those over 2Pt/Al₂O₃(∼20× Pt loading)

under purer ﬂow conditions established during single-bed

kinetic measurements but not during two-bed ETO reaction

measurements at stoichiometric H₂/BD ratios. This may

suggest that the Cu-free Pt/Al₂O₃catalysts suﬀer inhibition

caused by other compounds formed over the Zn−Y/Beta bed,

which includes water and other oxygenates (Scheme 2).

Steady-state reaction rates measured over 0.1Pt/Al₂O₃or

6Cu/Al₂O₃reﬂect minimum rates per mole of Pt or Cu,

respectively, to compare against rates measured over the SAA

catalyst. Here, dilute Pt incorporation within Cu domains

(∼180:1 mol Cu/mol Pt) is assumed to insigniﬁcantly aﬀect

Cu active site densities due to similar Cu particle sizes and bulk

Cu coordination between 6Cu/Al₂O₃and 0.1Pt6Cu/Al₂O₃

from Cu edge XAS measurements (Figure 4 and Table S.5).

Product distributions measured without cofed hydrogen at

588 K show an ∼3× higher butene yield over SAA 0.1Pt6Cu/

Al₂O₃than over any other selective hydrogenation catalysts

without observable butane formation (Figure 5A). Other Pt-

and Cu-containing catalysts display minimal diﬀerences in

butadiene and butene yields under identical conditions,

indicating that Pt or Cu species alone possess insuﬃcient

selective hydrogenation reactivity without hydrogen cofeeding

at ETO temperatures. Therefore, increased butadiene selective

hydrogenation over SAA 0.1Pt6Cu/Al₂O₃reﬂects increased

reactivity catalyzed by alloyed Pt−Cu ensemble sites relative to

Pt or Cu sites alone, which cannot be easily overcome by

increasing the bulk Pt loading (by 20× on 2Pt/Al₂O₃). This

increased reactivity is accomplished at stoichiometric hydrogen

concentrations generated in situ from ethanol dehydrogen-

ation, indicating the SAA Pt−Cu catalyst’s selective hydro-

genation eﬃcacy for the targeted ETO pathway (Scheme 2)

relative to other Pt- or Cu-containing catalysts studied here.

Further conversion of butadiene to butene isomers was

investigated by cofeeding hydrogen. At all three cofed

hydrogen partial pressures studied here (17.2, 50.7, and 98.3

kPa), no residual butadiene is observed over any Pt-containing

catalysts. Increased butene and subsequent butane yields are

derived from butadiene converted over Pt-containing catalysts

with saturated butane formation becoming more pronounced

with increasing hydrogen partial pressure. Increased saturated

butane yield with increasing cofed hydrogen partial pressure

occurs simultaneously with decreased ethylene and propene

selectivities (Figures S.26 −S.29) and increased C₁−C₃paraﬃn

formation, indicating that the observed hydrogenation

reactivity over Pt centers is indiscriminate over the range of

short-chain oleﬁn compounds as expected over Pt-containing

catalysts. Decreased butane and C₁−C₃paraﬃn formation are

observed over 0.1Pt6Cu/Al₂O₃relative to 2Pt/Al₂O₃(2.3×)

even under a 98.3 kPa hydrogen ﬂow, potentially reﬂecting the

decreased butene adsorption strength onto Pt−Cu ensemble

sites relative to Pt centers, as indicated in DFT calculations

(Table 1). Complete hydrogenation of butadiene to saturated

hydrocarbons reduces the desired C₃₊oleﬁn yield, indicating

the need for minimal or no external hydrogen cofeeding (near-

stoichiometric H₂/BD molar ratio) at ETO reaction temper-

atures for maximum C₃₊oleﬁn recovery.

The role of Pt−Cu ensemble sites can be further

investigated by comparing product distributions measured

over the SAA 0.1Pt6Cu/Al₂O₃and 6Cu/Al₂O₃catalysts. At all

hydrogen partial pressures, product distributions measured

over 6Cu/Al₂O₃show no butane formation, while minimal

changes in butene formation are observed at low hydrogen

partial pressures (0−17.2 kPa) relative to Zn−Y/Beta alone.

Residual butadiene conversion over 6Cu/Al₂O₃increases

directly with hydrogen partial pressure to form butene isomers

at high hydrogen partial pressures (50.7−98.3 kPa), but

complete butadiene conversion is still not observed even at

7202

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Figure 6. Steady-state combined butene formation rates (588 K, 100 cm³s⁻¹(g catalyst)⁻¹) collected over 0.1Pt6Cu/Al₂O₃(blue), 6Cu/Al₂O₃

(orange), 0.1Pt/Al₂O₃(black), and 2Pt/Al₂O₃(red) as a function of (A) butadiene partial pressure and (B) hydrogen partial pressure. Dashed lines

reﬂect linear regression best ﬁts.

The linear combination of steady-state rates of the 0.1Pt/Al₂O₃

and 6Cu/Al₂O₃catalysts remains signiﬁcantly lower than the

rate measured on 0.1Pt6Cu/Al₂O₃(Table S.7), indicating that

Pt−Cu ensemble sites have increased butadiene selective

hydrogenation reactivity relative to Cu domains or Pt sites

alone at low hydrogen partial pressures.

The larger apparent butadiene reaction order over 6Cu/Al₂O₃

relative to Pt-containing catalysts would then reﬂect a lower

coverage on active Cu sites due to 0.25−1.66 eV less favorable

butadiene binding enthalpies relative to Pt sites (Table 1).

Further, Pt sites embedded within Cu(111) surfaces or

Pt(111) also display increased butene adsorption enthalpies

relative to Cu sites alone, providing energetically favorable

binding sites for butene adsorption and subsequent hydro-

genation. The resulting butane formation would increase with

hydrogen partial pressure as observed during ETO experiments

(>17.2 kPa; Figure 5B−D) over Pt-containing catalysts.

The kinetic implications of Pt−Cu ensemble sites can be

evaluated by comparing the SAA catalyst with the mono-

metallic analogues using apparent reaction orders and DFT-

calculated adsorption enthalpies, hydrogen scission barriers,

and energy barriers through a commonly utilized Horiuti−

Polanyi reaction mechanism for selective hydrogenation.⁴⁴

Figure 6 shows steady-state butene formation rates as a

function of butadiene and hydrogen partial pressures for the

four hydrogenation catalysts studied here (isomer-speciﬁc

results are given in Figure S.30 and Table S.8). Butene

formation rates over both 0.1Pt6Cu/Al₂O₃and 0.1Pt/Al₂O₃

follow a nearly zero-order dependence on butadiene partial

pressure (0.1 and 0.3, respectively), while 2Pt/Al₂O₃has a

lower yet still approximately zero-order dependence (−0.2)

and 6Cu/Al₂O₃has a signiﬁcantly higher apparent order (0.7).

Assuming that butadiene selective hydrogenation follows a

Langmuir−Hinshelwood kinetic model over these catalysts as

previously modeled over other butadiene selective hydro-

genation catalysts (e.g., Pt(111), Pt₂Sn/Pt(111),⁶⁸and Pd/

Al₂O₃⁶⁹), diﬀerences in apparent butadiene reaction orders

most likely reﬂect diﬀerent coverages of reactive intermediate

species on each catalyst surface. Apparent butadiene reaction

orders decrease as calculated butadiene adsorption energies

become more negative (Table 1). These adsorption energies

indicate that bound butadiene species on kinetically relevant

active sites are adsorbed more strongly than hydrogen- or

butene-bound surface species and presumably yield higher

coverages. Butadiene-covered active sites would corroborate

the apparent zero-order butadiene dependence on Pt-

containing catalysts where butadiene adsorption is energeti-

cally favorable enough to completely saturate kinetically

relevant active sites and even becomes inhibitory as seen

through the negative apparent reaction order on 2Pt/Al₂O₃.

Apparent hydrogen reaction orders are approximately ﬁrst-

order over 0.1Pt6Cu/Al₂O₃(1.0), 0.1Pt/Al₂O₃(0.9), and

6Cu/Al₂O₃(0.8) and considerably higher (1.6) over 2Pt/

Al₂O₃. These apparent reaction orders and associated

increased butadiene selective hydrogenation rates with

increasing hydrogen partial pressure are consistent with the

increased butene and butane yields observed in the two-bed

system product distributions (Figures 5A−D and S.19 −S.22),

the largest of which is observed over 2Pt/Al₂O₃. These

apparent hydrogen reaction orders trend opposingly with

apparent butadiene reaction orders, which may reﬂect the

competitive adsorption of butadiene and hydrogen onto

kinetically relevant sites. Further, DFT calculations of Pt

centers embedded in both Cu and Pt nanoparticles show ∼0.3

eV lower hydrogen scission barriers than Cu sites alone,

indicating essentially barrierless formation of hydrogen

adatoms and matching previously reported observations over

Pt−Cu SAA materials.⁷⁰These lower hydrogen scission

barriers calculated over Pt sites then suggest the formation of

bound hydrogen adatom species on either Pt or neighboring

Cu centers as previously observed via scanning tunneling

microscopy on SAA Pt−Cu materials at 85 K.³⁷These

hydrogen adatom species would then be capable of facilitating

selective hydrogenation reactions with bound butadiene

species. Further, these Pt−Cu ensemble sites remain catalyti-

cally active signiﬁcantly longer than isolated Pt sites or small Pt

nanoparticles on 0.1Pt/Al₂O₃(Figure S.31) while limiting

inhibitory butadiene interactions seen through the negative

7203

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

apparent reaction order (and subsequently the higher hydro-

gen order) over 2Pt/Al₂O₃.

Taking the apparent ﬁrst-order hydrogen reaction orders

and nearly zero-order apparent butadiene reaction orders over

0.1Pt6Cu/Al₂O₃and 0.1Pt/Al₂O₃, a Horiuti−Polanyi reaction

mechanism can be proposed starting from a bound butadiene

intermediate to form 1-butene and trans-2-butene, matching

previous assertions.^44,71,72A detailed description is provided in

Section S.2.5 and Scheme S.1. Figure 7 shows DFT-calculated

energies throughout the investigated reaction mechanism

(Scheme S.1) over Cu(111), Pt(111), and SAA Pt−Cu(111)

surfaces reﬂecting 6Cu/Al₂O₃, 2Pt/Al₂O₃, and 0.1Pt6Cu/

Al₂O₃catalysts, respectively⁶²(calculated activation energies

and energy diﬀerences between elementary steps are listed in

Table S.9, and butadiene hydrogenation pathways to butane

through diradical intermediates (I3 and I4, Scheme S.1) are

shown in Figure S.32). The addition of two hydrogen adatoms

yields the formation of either butene isomers or two reduced

intermediate species (I3 and I4), the latter of which possesses

signiﬁcantly higher energies than 1-butene or trans-2-butene

and reﬂects signiﬁcantly less stable intermediates due to the

absence of conjugated bonds. These intermediates must then

undergo further hydrogenation to butane prior to desorption

from catalytic surfaces or isomerize into more stable butene

conﬁgurations, the latter of which may consist of signiﬁcant

activation energy barriers that were not investigated here.

After 1-butene or trans-2-butene formation, oleﬁn selectivity

for butenes relative to butane can be assessed by comparing

butene desorption energies with butene hydrogenation

activation energy barriers. Over Cu(111) and SAA Pt−

Cu(111) surfaces, butene isomer desorption energies are

lower than calculated activation energy barriers to form butane

(Table S.9), indicating a preference for butene desorption and

concomitant termination of the hydrogenation reaction. This

diﬀerence between desorption energy and butene hydro-

genation activation energy is larger over Cu(111) than over

SAA Pt−Cu(111). This corroborates observed product

distributions from two-bed measurements over 6Cu/Al₂O₃

and 0.1Pt6Cu/Al₂O₃, where negligible butane formation is

observed over both catalysts at near-stoichiometric H₂/BD

ratios but is never observed over 6Cu/Al₂O₃at all studied

hydrogen partial pressures (Figure 5). The limited diﬀerence

between butene desorption energy and hydrogenation

activation energy over SAA Pt−Cu(111) further corroborates

selective butene formation at the near-stoichiometric hydrogen

partial pressures in single- or two-bed measurements and could

explain the decreased butene selectivity with increasing

hydrogen partial pressures given the ﬁrst-order apparent

reaction order with respect to hydrogen partial pressure from

experimental measurements (Figure 6). These observations,

both experimental and computational, are inconsistent with

previously reported calculations indicating that selective

hydrogenation reactivities are similar over Cu(111) and Pt−

Cu(111) surfaces when accounting for relative surface

concentrations of Cu and Pt species.⁴⁴Similar computational

observations over Pt(111) indicate that butene hydrogenation

activation energy barriers are lower than butene desorption

energies (Table S.9). This suggests that hydrocarbon

selectivities should heavily favor butane formation over

Pt(111), as seen at all cofed hydrogen partial pressures (Figure

5). The above observations on Pt(111) and Cu(111) reﬂect

the potentially highest butane and butene selectivities,

respectively, while the reaction energy proﬁle over Pt−

Figure 7. Reaction coordinate diagrams reﬂecting butadiene selective

hydrogenation pathways to form 1-butene and trans-2-butene and

subsequent butene hydrogenation pathways to form butane over (A)

Cu(111), (B) Pt(111), and (C) Pt−Cu(111) surfaces. Distinct

pathways are depicted here using the designations presented in

Scheme S.1: butadiene → I2 → 1-butene → I6 → butane (black),

butadiene → I1 → trans-2-butene → I5 → butane (blue), and

butadiene → I1 → 1-butene → I5 → butane (red). Diagonal dashed

lines reﬂect desorption energies for bound butenes. Energy diﬀerences

and activation energies are listed in Table S.9.

Cu(111) contains Pt−Cu active site ensembles possessing

both higher hydrogenation reactivity than Cu sites alone and

energetic barriers that favor butene desorption over subsequent

butene hydrogenation to form butane.

7204

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

The energy diﬀerences between butene desorption and

hydrogenation phenomena should be treated generally for

comparing these Pt- and Cu-containing catalysts. Increased

temperatures will destabilize adsorbed species and decrease

desorption energies through entropic contributions, while

activation energies will generally be less aﬀected by temper-

atures for consistent most abundant surface intermediates and

kinetically relevant transition states. Therefore, energy diﬀer-

ences are maximized at 0 K and will decrease with increasing

temperatures, indicating that the selectivity toward butene

formation without overhydrogenation to butane should be

more pronounced at increased temperatures. The observed

trend favoring butene desorption relative to hydrogenation

over Cu(111), Pt−Cu(111), and Pt(111) is signiﬁcantly more

obvious with binding energies calculated at reaction temper-

atures (Table S.9) due to destabilized bound butene

intermediates (>1 eV higher binding energies). This trend

indicates that the butadiene hydrogenation reaction network

should favor butene desorption over further hydrogenation to

butane in order of Cu(111), Pt−Cu(111), and Pt(111) with

Pt(111) favoring further hydrogenation. This trend should

hold at all hydrogen partial pressures as observed in product

distributions from two-bed experiments but should shift

toward complete butadiene hydrogenation given high hydro-

gen partial pressures.

Taking the experimental and computational ﬁndings

together, overall butene formation rates over the Pt−Cu SAA

catalyst are higher than those measured over 6Cu/Al₂O₃or

0.1Pt/Al₂O₃at stoichiometric butadiene and hydrogen partial

pressures and are similar to rates over 2Pt/Al₂O₃yet with

signiﬁcantly lower Pt metal concentrations. Increased butene

formation rates relative to 6Cu/Al₂O₃indicate that incorpo-

rated Pt centers within Cu domains either generate additional

kinetically relevant active sites or shift the overall selective

hydrogenation reaction mechanism with an associated higher

reactivity. The former may occur by promoting nearby Cu

atoms through Cu−H adatom formation due to negligible

hydrogen scission barriers over Pt sites. These same Pt sites

generate energetically favorable butadiene or butene binding

sites while stabilizing butadiene to a far greater extent than

butene isomers. In either case, the incorporation of Pt centers

into Cu nanoparticle domains within the SAA catalytic material

generates active site ensembles capable of catalyzing selective

hydrogenation reactions at low relative hydrogen partial

pressures with rates that surpass those on monometallic Pt

or Cu catalysts. This combination of DFT calculations and

apparent kinetic measurements supports the selection of SAA

Pt−Cu materials as a critical catalytic component for the ﬁnal

ETO reaction steps, namely, the selective hydrogenation of

butadiene at stoichiometric hydrogen and butadiene partial

pressures (H₂/BD = 1). While Zn−Y/Beta containing

Brønsted acidic Y sites and Lewis acidic Zn and Y sites

catalyzes ETB conversion, the selective hydrogenation of

butadiene at low hydrogen partial pressures requires Pt−Cu

ensemble sites at stoichiometric hydrogen and butadiene

partial pressures and ETB-relevant reaction temperatures.

However, the applicability of this ETO pathway (achieved

over the two-bed composite catalyst of Zn−Y/Beta and SAA

0.1Pt6Cu/Al₂O₃) must be further demonstrated via optimizing

the selectivity of butene-rich C₃₊oleﬁns.

0.1Pt6Cu/Al₂O₃catalyst systems, many opportunities exist to

maximize butene and C₃₊oleﬁn selectivities at high ethanol

conversions (e.g., tuning active site distributions, space

velocities, and reaction temperatures). Since optimizing

product distributions toward speciﬁc oleﬁns is not the primary

goal of this work as noted by the singular elemental

composition of the multifunctional catalyst and the ﬁxed

reaction conditions, only a couple of small steps are explored

here to enhance the ETO pathway viability. As shown in

Figure 5A, ∼20% of the observed product distribution over the

composite Zn−Y/Beta and SAA 0.1Pt6Cu/Al₂O₃catalyst

system (∼88% conversion) is butadiene, indicating that butene

yields can be increased simply by balancing butadiene

formation with selective hydrogenation reactivity. As expected,

increasing the catalyst loading of SAA 0.1Pt6Cu/Al₂O₃to

equivalent catalyst loadings of Zn−Y/Beta and SAA 0.1Pt6Cu/

Al₂O₃yields increased butadiene conversion over SAA and

selectivity to butenes (54%) and C₃₊oleﬁns (65%) at slightly

higher ethanol conversions (95%; Figure S.33).

Stoichiometric H₂/BD ratios are necessary to avoid

overhydrogenation of butadiene to butane, as observed in

Figure 5 and DFT energy proﬁle calculations (Figure 7).

Positive apparent hydrogen reaction orders over SAA

0.1Pt6Cu/Al₂O₃indicate that selective hydrogenation reaction

rates can be further increased by increasing hydrogen partial

pressures. Increasing the ethanol partial pressure from 3.1 to

6.1 kPa over equivalent Zn−Y/Beta and SAA 0.1Pt6Cu/Al₂O₃

catalyst loadings maintains a consistent near-stoichiometric

H₂/BD ratio while yielding signiﬁcantly higher butene (65%)

and C₃₊(78%) selectivities at a similar ethanol conversion

(94%; Figure S.34). However, these product selectivities

remain relatively unoptimized due to no optimization of active

site distributions or other reaction conditions responsible for

side product formation. Further, these results are expected to

hold even when Zn−Y/Beta and 0.1Pt6Cu/Al₂O₃are

physically mixed into a single bed of composite catalyst

based on relatively small changes in nonoptimized product

distributions at all studied cofed hydrogen partial pressures

(Figure 5; 0.1Pt6Cu/Al₂O₃-PM).

Despite the need for further catalyst optimization, C₃₊oleﬁn

selectivities observed here at high ethanol conversions (>85%)

exceed other published ethanol valorization pathways (Figure

S.35 and Table S.11) such as ethanol to oleﬁns via an ethylene

intermediate over Brønsted acid zeolites, Guerbet coupling of

ethanol and subsequent dehydration to oleﬁn products, and

ethanol condensation to form isobutene or propene over oxide

materials (e.g., ZnZrO_x)⁵. The utility of this two-bed catalytic

system is process intensiﬁcation by performing cascade

reactions at a constant temperature and pressure despite the

presence of coproducts (e.g., water, oxygenates, ethylene).

Further, this two-bed composite Zn−Y/Beta and SAA

0.1Pt6Cu/Al₂O₃catalyst setup can operate without cofed

hydrogen, a signiﬁcant advantage from both process design and

economic perspectives.

4. CONCLUSIONS

Ethanol valorization to C₃₊oleﬁn (ETO) is a promising

reaction pathway for generating key oligomerization precursors

by leveraging butadiene as a critical intermediate. This ETO

pathway was investigated over a composite catalyst composed

of a bimetallic Zn−Y/Beta zeolite and SAA 0.1Pt6Cu/Al₂O₃-

supported metal catalyst, yielding a high C₃₊oleﬁn selectivity

(78% at 94% ethanol conversion, 588 K) without hydrogen

3.4. Preliminary ETO Reaction Pathway Optimization.

As minimal eﬀorts have been taken here to tune oleﬁn

distributions over the composite Zn−Y/Beta and SAA

7205

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

cofeeding. XAS measurements and HAADF-STEM images

identiﬁed the isolated nature of Zn and Y on the Beta zeolite

support despite the high Y loading (∼7 wt %) and isolated Pt

within Cu nanoparticles, while transmission IR spectra

collected after pyridine adsorption onto Zn−Y/Beta indicated

the presence of both Lewis acidic Zn and Y sites and previously

unreported Brønsted acidic Y centers, identifying various active

metal species to match with ETO kinetic measurements.

Bimetallic Zn−Y/Beta catalyzes the multistep formation of

butadiene from ethanol with the concomitant formation of

near-stoichiometric hydrogen partial pressures, while SAA

0.1Pt6Cu/Al₂O₃selectively hydrogenates butadiene to form

butene products at this stoichiometric H₂/BD ratio and ETB

reaction temperature over Pt−Cu ensemble sites. DFT

calculations indicate that increased selective hydrogenation

reactivity over Pt−Cu(111) surfaces combines low hydrogen

scission barriers and favorable butadiene binding energies with

preferential butene desorption energies relative to further

hydrogenation activation energies forming butane. Together,

this multifunctional catalyst enables direct bioethanol valor-

ization using only in situ-generated hydrogen to form butene-

rich C₃₊oleﬁn streams, which are readily oligomerized into

longer-chain oleﬁn products necessary for renewable jet fuel

production.

Laboratory, Oak Ridge, Tennessee 37830, United States;

orcid.org/0000-0002-9870-1029

Evan C. Wegener − Chemical Sciences and Engineering

Division, Argonne National Laboratory, Lemont, Illinois

60439, United States

Kinga A. Unocic − Center for Nanophase Materials Sciences,

Oak Ridge National Laboratory, Oak Ridge, Tennessee

37830, United States

Lawrence F. Allard − Material Science and Technology

Division, Oak Ridge National Laboratory, Oak Ridge,

Tennessee 37830, United States

Mingxia Zhou − Materials Science Division, Argonne National

Laboratory, Lemont, Illinois 60439, United States;

orcid.org/0000-0002-1896-1024

Rajeev S. Assary − Materials Science Division, Argonne

National Laboratory, Lemont, Illinois 60439, United States;

orcid.org/0000-0002-9571-3307

Jeﬀrey T. Miller − Department of Chemical Engineering,

Purdue University, West Lafayette, Indiana 47907, United

States; orcid.org/0000-0002-6269-0620

Theodore R. Krause − Chemical Sciences and Engineering

Division, Argonne National Laboratory, Lemont, Illinois

60439, United States

Fan Lin − Institute for Integrated Catalysis, Paciﬁc Northwest

National Laboratory, Richland, Washington 99354, United

States

Huamin Wang − Institute for Integrated Catalysis, Paciﬁc

Northwest National Laboratory, Richland, Washington

99354, United States; orcid.org/0000-0002-3036-2649

A. Jeremy Kropf − Chemical Sciences and Engineering

Division, Argonne National Laboratory, Lemont, Illinois

60439, United States

Ce Yang − Chemical Sciences and Engineering Division,

Argonne National Laboratory, Lemont, Illinois 60439,

United States

Dongxia Liu − Department of Chemical and Biomolecular

Engineering, University of Maryland, College Park, Maryland

20742, United States; orcid.org/0000-0001-8712-2219

ASSOCIATED CONTENT

■

sı

* Supporting Information

The Supporting Information is available free of charge at

https://pubs.acs.org/doi/10.1021/acscatal.1c01136.

XRD patterns, N₂adsorption isotherms, XAS ﬁtting

details and associated ﬁgures, STEM images, NH₃−TPD

spectra, additional product distributions and selectivity

plots, DFT-calculated adsorption images, additional

plots of butene formation rates as a function of

butadiene and hydrogen partial pressures, transient

butadiene selective hydrogenation proﬁles, DFT-calcu-

lated energy diﬀerences and activation energy barriers,

additional reaction coordinate diagrams, product dis-

tribution plots of preliminary optimization strategies,

and comparison of presented ETO pathway relative to

literature observations (PDF)

Complete contact information is available at:

https://pubs.acs.org/10.1021/acscatal.1c01136

Author Contributions

M.J.C. and J.Z. contributed equally. The manuscript was

written through contributions of all authors. All authors have

given approval to the ﬁnal version of the manuscript.

AUTHOR INFORMATION

■

Corresponding Author

Funding

Zhenglong Li − Manufacturing Science Division, Oak Ridge

National Laboratory, Oak Ridge, Tennessee 37830, United

States; orcid.org/0000-0001-8811-8625; Email: liz3@

ornl.gov

Microscopy research, K.A.U., M.J.C., J.Z., S.C.P., D.L., and

Z.L., were sponsored by the U.S. Department of Energy

(DOE), Oﬃce of Energy Eﬃciency and Renewable Energy

(EERE), Bioenergy Technologies Oﬃce (BETO), under

Contract DE-AC05-00OR22725 (ORNL) with UT-Battelle,

LLC, and in collaboration with the Chemical Catalysis for

Bioenergy (ChemCatBio) Consortium, a member of the

Energy Materials Network. Microscopy research was also

supported by the Center for Nanophase Materials Sciences

(CNMS), which is sponsored by the Scientiﬁc User Facilities

Division, Oﬃce of Basic Energy Sciences, U.S. DOE. MR-CAT

operations are supported by the DOE and the MR-CAT

member institutions. This research used resources of the

Advanced Photon Source, a U.S. DOE Oﬃce of Science User

Facility operated for the DOE Oﬃce of Science by Argonne

National Laboratory under Contract No. DE-AC02-

Authors

Michael J. Cordon − Manufacturing Science Division, Oak

Ridge National Laboratory, Oak Ridge, Tennessee 37830,

United States

Junyan Zhang − Manufacturing Science Division, Oak Ridge

National Laboratory, Oak Ridge, Tennessee 37830, United

States; Department of Chemical and Biomolecular

Engineering, University of Maryland, College Park, Maryland

20742, United States

Stephen C. Purdy − Department of Chemical Engineering,

Purdue University, West Lafayette, Indiana 47907, United

States; Neutron Scattering Division, Oak Ridge National

7206

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Nanosized Zn_xZr_yO_zMixed Oxides with Balanced Acid-Base Sites.

J. Am. Chem. Soc. 2011, 133, 11096−11099.

(10) Zhao, B.; Men, Y.; Zhang, A.; Wang, J.; He, R.; An, W.; Li, S.

Influence of Different Precursors on Isobutene Production from Bio-

Ethanol over Bifunctional Zn₁Zr₁₀O_xCatalysts. Appl. Catal., A 2018,

558, 150−160.

(11) Derouane, E. G.; Nagy, J. B.; Dejaifve, P.; Vanhooff, J. H. C.;

Spekman, B. P.; Vedrine, J. C.; Naccache, C. Elucidation of

Mechanism of Conversion of Methanol and Ethanol to Hydrocarbons

on a New Type of Synthetic Zeolite. J. Catal. 1978, 53, 40−55.

(12) Talukdar, A. K.; Bhattacharyya, K. G.; Sivasanker, S. HZSM-5

Catalysed Conversion of Aqueous Ethanol to Hydrocarbons. Appl.

Catal., A 1997, 148, 357−371.

(13) Galadima, A.; Muraza, O. Zeolite Catalysts in Upgrading of

Bioethanol to Fuels Range Hydrocarbons: A Review. J. Ind. Eng.

Chem. 2015, 31, 1−14.

(14) Nakajima, T.; Nameta, H.; Mishima, S.; Matsuzaki, I.; Tanabe,

K. A Highly-Active and Highly Selective Oxide Catalyst for the

Conversion of Ethanol to Acetone in the Presence of Water-Vapor. J.

Mater. Chem. 1994, 4, 853−858.

(15) Nishiguchi, T.; Matsumoto, T.; Kanai, H.; Utani, K.;

Matsumura, Y.; Shen, W. J.; Imamura, S. Catalytic Steam Reforming

of Ethanol to Produce Hydrogen and Acetone. Appl. Catal., A 2005,

279, 273−277.

(16) Hannon, J. R.; Lynd, L. R.; Andrade, O.; Benavides, P. T.;

Beckham, G. T.; Biddy, M. J.; Brown, N.; Chagas, M. F.; Davison, B.

H.; Foust, T.; Junqueira, T. L.; Laser, M. S.; Li, Z.; Richard, T.; Tao,

L.; Tuskan, G. A.; Wang, M.; Woods, J.; Wyman, C. E.

Technoeconomic and Life-Cycle Analysis of Single-Step Catalytic

Conversion of Wet Ethanol into Fungible Fuel Blendstocks. Proc.

Natl. Acad. Sci. U.S.A. 2020, 117, 12576−12583.

06CH11357. S.C.P. and J.T.M. were supported by the

National Science Foundation under Cooperative Agreement

No. EEC1647722. The computing resource was provided on

“BEBOP”, a computing cluster operated by the Laboratory

Computing Resource Center at Argonne National Laboratory.

M.Z. and R.S.A. acknowledge Computational Chemistry

Physics Consortium (CCPC), which is supported by the

Bioenergy Technologies Oﬃce of Energy Eﬃciency &

Renewable Energy. F.L. and H.W. were ﬁnancially supported

by the U.S. DOE, EERE, Bioenergy Technologies Oﬃce, and

part of this work was performed at the Paciﬁc Northwest

National Laboratory (PNNL), a multiprogram national

laboratory operated for DOE by Battelle Memorial Institute.

The views and opinions of the authors expressed herein do not

necessarily state or reﬂect those of the U.S. Government or any

agency thereof.

Notes

The authors declare the following competing ﬁnancial

interest(s): Patent application is pending for the inventor Z.L.

This manuscript has been authored in part by UT-Battelle,

LLC, under Contract DE-AC05-00OR22725 with the U.S.

Department of Energy (DOE). The U.S. government retains

and the publisher, by accepting the article for publication,

acknowledges that the U.S. government retains a nonexclusive,

paid-up, irrevocable, worldwide license to publish or reproduce

the published form of this manuscript, or allow others to do so,

for U.S. government purposes. DOE will provide public access

to these results of federally sponsored research in accordance

with the DOE Public Access Plan (http://energy.gov/

downloads/doe-public-access-plan).

(17) Makshina, E. V.; Dusselier, M.; Janssens, W.; Degreve, J.;

Jacobs, P. A.; Sels, B. F. Review of Old Chemistry and New Catalytic

Advances in the On-Purpose Synthesis of Butadiene. Chem. Soc. Rev.

2014, 43, 7917−7953.

(18) Sushkevich, V. L.; Ivanova, I. I. Mechanistic Study of Ethanol

Conversion into Butadiene over Silver Promoted Zirconia Catalysts.

Appl. Catal., B 2017, 215, 36−49.

ACKNOWLEDGMENTS

■

The authors acknowledge Dr. Meijun Li for additional

experimental assistance with the XRD analysis. The authors

also thank Shawn K. Reeves and Dr. Qianying Guo for

assistance with TEM work.

(19) Yan, T.; Dai, W.; Wu, G.; Lang, S.; Hunger, M.; Guan, N.; Li, L.

Mechanistic Insights into One-Step Catalytic Conversion of Ethanol

to Butadiene over Bifunctional Zn-Y/Beta Zeolite. ACS Catal. 2018,

8, 2760−2773.

REFERENCES

■

(20) Muller, P.; Burt, S. P.; Love, A. M.; McDermott, W. P.; Wolf,

̈

(1) Renewable Fuels Association. 2019 Ethanol Industry Outlook,

2019.

P.; Hermans, I. Mechanistic Study on the Lewis Acid Catalyzed

Synthesis of 1,3-Butadiene over Ta-BEA Using Modulated Operando

DRIFTS-MS. ACS Catal. 2016, 6, 6823−6832.

(2) Iwamoto, M. Selective Catalytic Conversion of Bio-Ethanol to

Propene: A Review of Catalysts and Reaction Pathways. Catal. Today

2015, 242, 243−248.

(3) Sun, J.; Wang, Y. Recent Advances in Catalytic Conversion of

Ethanol to Chemicals. ACS Catal. 2014, 4, 1078−1090.

(4) Adhikari, S. P.; Zhang, J.; Guo, Q.; Unocic, K. A.; Tao, L.; Li, Z.

A Hybrid Pathway to Biojet Fuel via 2,3-Butanediol. Sustainable

Energy Fuels 2020, 4, 3904−3914.

(5) Eagan, N. M.; Kumbhalkar, M. D.; Buchanan, J. S.; Dumesic, J.

A.; Huber, G. W. Chemistries and Processes for the Conversion of

Ethanol into Middle-Distillate Fuels. Nat. Rev. Chem. 2019, 3, 223−

249.

(6) Duan, C.; Zhang, X.; Zhou, R.; Hua, Y.; Chen, J.; Zhang, L.

Hydrothermally Synthesized HZSM-5/SAPO-34 Composite Zeolite

Catalyst for Ethanol Conversion to Propylene. Catal. Lett. 2011, 141,

1821−1827.

(7) Tsuchida, T.; Yoshioka, T.; Sakuma, S.; Takeguchi, T.; Ueda, W.

Synthesis of Biogasoline from Ethanol over Hydroxyapatite Catalyst.

Ind. Eng. Chem. Res. 2008, 47, 1443−1452.

(8) Bi, J.; Liu, M.; Song, C.; Wang, X.; Guo, X. C-2 −C-4 Light

Olefins from Bioethanol Catalyzed by Ce-Modified Nanocrystalline

HZSM-5 Zeolite Catalysts. Appl. Catal., B 2011, 107, 68−76.

(9) Sun, J.; Zhu, K.; Gao, F.; Wang, C.; Liu, J.; Peden, C. H. F.;

Wang, Y. Direct Conversion of Bio-Ethanol to Isobutene on

(21) Foley, B. L.; Johnson, B. A.; Bhan, A. Kinetic Evaluation of

Deactivation Pathways in Methanol-to-Hydrocarbon Catalysis on

HZSM-5 with Formaldehyde, Olefinic, Dieneic, and Aromatic Co-

Feeds. ACS Catal. 2021, 11, 3628−3637.

(22) Albright, L. F.; Marek, J. C. Mechanistic Model for Formation

of Coke in Pyrolysis Units Producing Ethylene. Ind. Eng. Chem. Res.

1988, 27, 755−759.

(23) Nguyen, N. T. T.; Matei-Rutkovska, F.; Huchede, M.;

Jaillardon, K.; Qingyi, G.; Michel, C.; Millet, J. M. M. Production

of 1,3-Butadiene in One Step Catalytic Dehydration of 2,3-

Butanediol. Catal. Today 2019, 323, 62−68.

(24) Wu, J.; Peng, Z.; Sun, P.; Bell, A. T. N-Butane Dehydrogen-

ation over Pt/Mg(In)(Al)O. Appl. Catal., A 2014, 470, 208−214.

(25) Larina, O. V.; Kyriienko, I. P.; Batakin, D. Y.; Vorokhta, M.;

Khalakhan, I.; Nychiporuk, Y. M.; Matolin, V.; Soloviev, S. O.; Orlyk,

S. M. Effect of ZnO on Acid-Base Properties and Catalytic

Performances of ZnO/ZrO₂-SiO₂Catalysts in 1,3-Butadiene

Production from Ethanol-Water Mixture. Catal. Sci. Technol. 2019,

9, 3964−3978.

(26) Da Ros, S.; Jones, M. D.; Mattia, D.; Pinto, J. C.; Schwaab, M.;

Noronha, F. B.; Kondrat, S. A.; Clarke, T. C.; Taylor, S. H. Ethanol to

1,3-Butadiene Conversion by Using ZrZn-Containing MgO/SiO₂

7207

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Systems Prepared by Co-Precipitation and Effect of Catalyst Acidity

Modification. ChemCatChem 2016, 8, 2376−2386.

genation of 1,3-Butadiene: A Combined DFT and Microkinetic

Modeling Study. J. Phys. Chem. C 2018, 122, 10883−10891.

(45) Harris, J. W.; Cordon, M. J.; Di Iorio, J. R.; Vega-Vila, J. C.;

Ribeiro, F. H.; Gounder, R. Titration and Quantification of Open and

Closed Lewis Acid Sites in Sn-Beta Zeolites That Catalyze Glucose

Isomerization. J. Catal. 2016, 335, 141−154.

(27) Zhu, Q.; Wang, B.; Tan, T. Conversion of Ethanol and

Acetaldehyde to Butadiene over MgO-SiO₂Catalysts: Effect of

Reaction Parameters and Interaction between MgO and SiO₂on

Catalytic Performance. ACS Sustainable Chem. Eng. 2017, 5, 722−733.

(28) Sushkevich, V. L.; Ivanova, I. I.; Ordomsky, V. V.; Taarning, E.

Design of a Metal-Promoted Oxide Catalyst for the Selective

Synthesis of Butadiene from Ethanol. ChemSusChem 2014, 7,

2527−2536.

(46) Kresse, G.; Hafner, J. Ab-Initio Molecular-Dynamics Simulation

of the Liquid-Metal Amorphous-Semiconductor Transition in

Germanium. Phys. Rev. B 1994, 49, No. 14251.

(47) Kresse, G.; Furthmuller, J. Efficiency of Ab-Initio Total Energy

Calculations for Metals and Semiconductors Using a Plane-Wave

Basis Set. Comput. Mater. Sci. 1996, 6, 15−50.

(48) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and

Accurate Ab Initio Parametrization of Density Functional Dispersion

Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010,

132, No. 154104.

(49) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping

Function in Dispersion Corrected Density Functional Theory. J.

Comput. Chem. 2011, 32, 1456−1465.

(50) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient

Approximation Made Simple. Phys. Rev. Lett. 1996, 77, No. 3865.

(51) Henry, C. R. Morphology of Supported Nanoparticles. Prog.

Surf. Sci. 2005, 80, 92−116.

(52) Methfessel, M.; Paxton, A. T. High-Precision Sampling for

Brillouin-Zone Integration in Metals. Phys. Rev. B 1989, 40, No. 3616.

(53) Henkelman, G.; Uberuaga, B. P.; Jonsson, H. A Climbing

Image Nudged Elastic Band Method for Finding Saddle Points and

Minimum Energy Paths. J. Chem. Phys. 2000, 113, 9901−9904.

(54) Henkelman, G.; Jonsson, H. A Dimer Method for Finding

Saddle Points on High Dimensional Potential Surfaces Using Only

First Derivatives. J. Chem. Phys. 1999, 111, 7010−7022.

(55) Hölderich, W. F.; Tjoe, J. Direct Hydrogenation of Aromatic

Carboxylic Acids to Their Corresponding Aldehydes with Zinc Oxide

Catalysts. Appl. Catal., A 1999, 184, 257−264.

(56) Keshavaraja, A.; Hegde, V. R.; Pandey, B.; Ramaswswamy, A.

V.; Kumar, P.; Ravindranathan, T. An Yttrium-Based Strong Lewis-

Acid for the Heterogeneous Catalysis of the Diels-Alder Reaction.

Angew. Chem., Int. Ed. 1995, 34, 2143−2145.

(57) Palomino, G. T.; Pascual, J. J. C.; Delgado, M. R.; Parra, J. B.;

Arean, C. O. FT-IR Studies on the Acidity of Gallium-Substituted

Mesoporous MCM-41 Silica. Mater. Chem. Phys. 2004, 85, 145−150.

(58) Connell, G.; Dumesic, J. A. The Generation of Bronsted and

Lewis Acid Sites on the Surface of Silica by Addition of Dopant

Cations. J. Catal. 1987, 105, 285−298.

(59) Orazov, M.; Davis, M. E. Catalysis by Framework Zinc in Silica-

Based Molecular Sieves. Chem. Sci. 2016, 7, 2264−2274.

(60) Qi, L.; Zhang, Y.; Conrad, M. A.; Russell, C. K.; Miller, J.; Bell,

A. T. Ethanol Conversion to Butadiene over Isolated Zinc and

Yttrium Sites Grafted onto Dealuminated Beta Zeolite. J. Am. Chem.

Soc. 2020, 142, 14674−14687.

(61) Hussein, G. A. M.; Gates, B. C. Surface and Catalytic Properties

of Yttrium Oxide: Evidence from Infrared Spectroscopy. J. Catal.

1998, 176, 395−404.

(62) Sun, G.; Zhao, Z.-J.; Mu, R.; Zha, S.; Li, L.; Chen, S.; Zang, K.;

Luo, J.; Li, Z.; Purdy, S. C.; Kropf, A. J.; Miller, J. T.; Zeng, L.; Gong,

J. Breaking the Scaling Relationship via Thermally Stable Pt/Cu

Single Atom Alloys for Catalytic Dehydrogenation. Nat. Commun.

2018, 9, No. 4454.

(63) Boucher, M. B.; Zugic, B.; Cladaras, G.; Kammert, J.;

Marcinkowski, M. D.; Lawton, T. J.; Sykes, E. C. H.; Flytzani-

Stephanopoulos, M. Single Atom Alloy Surface Analogs in Pd_0.18Cu₁₅

Nanoparticles for Selective Hydrogenation Reactions. Phys. Chem.

Chem. Phys. 2013, 15, 12187−12196.

(64) Norskov, J. K.; Abild-Pedersen, F.; Studt, F.; Bligaard, T.

Density Functional Theory in Surface Chemistry and Catalysis. Proc.

Natl. Acad. Sci. U.S.A. 2011, 108, 937−943.

(65) Krier, J. M.; Michalak, W. D.; Cai, X.; Carl, L.; Komvopoulos,

K.; Somorjai, G. A. Sum Frequency Generation Vibrational

Spectroscopy of 1,3-Butadiene Hydrogenation on 4 nm Pt@SiO₂,

(29) Angelici, C.; Meirer, F.; van der Eerden, A. M. J.; Schaink, H.

L.; Goryachev, A.; Hofmann, J. P.; Hensen, E. J. M.; Weckhuysen, B.

M.; Bruijnincx, P. C. A. Ex Situ and Operando Studies on the Role of

Copper in Cu-Promoted SiO₂-MgO Catalysts for the Lebedev

Ethanol-to-Butadiene Process. ACS Catal. 2015, 5, 6005−6015.

(30) Shylesh, S.; Gokhale, A. A.; Scown, C. D.; Kim, D.; Ho, C. R.;

Bell, A. T. From Sugars to Wheels: The Conversion of Ethanol to 1,3-

Butadiene over Metal-Promoted Magnesia-Silicate Catalysts. Chem-

SusChem 2016, 9, 1462−1472.

(31) Janssens, W.; Makshina, E. V.; Vanelderen, P.; De Clippel, F.;

Houthoofd, K.; Kerkhofs, S.; Martens, J. A.; Jacobs, P. A.; Sels, B. F.

Ternary Ag/MgO-SiO₂Catalysts for the Conversion of Ethanol into

Butadiene. ChemSusChem 2015, 8, 994−1008.

(32) Dastillung, R.; Cadran, N.; Jacquin, M.; Huyghe, R.; Fischer, B.

Process for Producing 1,3-Butadiene from a Feedstock Comprising

Ethanol. U.S. Patent US9776933B22013.

(33) Sushkevich, V. L.; Ivanova, I. I. Ag-Promoted ZrBEA Zeolites

Obtained by Post-Synthetic Modification for Conversion of Ethanol

to Butadiene. ChemSusChem 2016, 9, 2216−2225.

(34) Kyriienko, P. I.; Larina, O. V.; Soloviev, S. O.; Orlyk, S. M.;

Calers, C.; Dzwigaj, S. Ethanol Conversion into 1,3-Butadiene by the

Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn). ACS

Sustainable Chem. Eng. 2017, 5, 2075−2083.

(35) Wang, C.; Zheng, M.; Li, X.; Li, X.; Zhang, T. Catalytic

Conversion of Ethanol into Butadiene over High Performance

LiZnHf-MFI Zeolite Nanosheets. Green Chem. 2019, 21, 1006−1010.

(36) Dai, W.; Zhang, S.; Yu, Z.; Yan, T.; Wu, G.; Guan, N.; Li, L.

Zeolite Structural Confinement Effects Enhance One-Pot Catalytic

Conversion of Ethanol to Butadiene. ACS Catal. 2017, 7, 3703−3706.

(37) Lucci, F. R.; Liu, J.; Marcinkowski, M. D.; Yang, M.; Allard, L.

F.; Flytzani-Stephanopoulos, M.; Sykes, E. C. H. Selective Hydro-

genation of 1,3-Butadiene on Platinum-Copper Alloys at the Single-

Atom Limit. Nat. Commun. 2015, 6, No. 8550.

(38) Hu, C.; Sun, J.; Wang, D.; Peng, M.; Shao, M.; Zhu, Q.; Ma, D.

Hydrogen Diffusion Guided Design of Pt-Based Alloys for Inhibition

of Butadiene Over-Hydrogenation. ChemPhysChem 2019, 20, 1804−

1811.

(39) Godínez, C.; Cabanes, A. L.; Villora, G. Experimental Study of

the Selective Hydrogenation of Steam Cracking C-2 Cut. Front End

and Tail End Variants. Chem. Eng. Commun. 1998, 164, 225−247.

(40) Koeppel, R. A.; Wehrli, J. T.; Wainwright, M. S.; Trimm, D. L.;

Cant, N. W. Selective Hydrogenation of C-4-Alkynes over a Copper

on Silica Catalyst. Appl. Catal., A 1994, 120, 163−177.

(41) Pattamakomsan, K.; Suriye, K.; Dokjampa, S.; Mongkolsiri, N.;

Praserthdam, P.; Panpranot, J. Effect of Mixed Al₂O₃Structure

between Theta- and Alpha-Al₂O₃on the Properties of Pd/Al₂O₃in

the Selective Hydrogenation of 1,3-Butadiene. Catal. Commun. 2010,

11, 311−316.

(42) Lonergan, W. W.; Xing, X.; Zheng, R.; Qi, S.; Huang, B.; Chen,

J. G. Low-Temperature 1,3-Butadiene Hydrogenation over Supported

Pt/3d/Gamma-Al₂O₃Bimetallic Catalysts. Catal. Today 2011, 160,

61−69.

(43) Liu, J.; Shan, J.; Lucci, F. R.; Cao, S.; Sykes, E. C. H.; Flytzani-

Stephanopoulos, M. Palladium-Gold Single Atom Alloy Catalysts for

Liquid Phase Selective Hydrogenation of 1-Hexyne. Catal. Sci.

Technol. 2017, 7, 4276−4284.

(44) Yang, K.; Yang, B. Identification of the Active and Selective

Sites over a Single Pt Atom-Alloyed Cu Catalyst for the Hydro-

7208

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

ACS Catalysis

pubs.acs.org/acscatalysis

Research Article

Pd@SiO₂, and Rh@SiO₂Core-Shell Catalysts. Nano Lett. 2015, 15,

39−44.

(66) Sartipi, S.; Makkee, M.; Kapteijn, F.; Gascon, J. Catalysis

Engineering of Bifunctional Solids for the One-Step Synthesis of

Liquid Fuels from Syngas: A Review. Catal. Sci. Technol. 2014, 4,

893−907.

(67) Jiao, F.; Li, J.; Pan, X.; Xiao, J.; Li, H.; Ma, H.; Wei, M.; Pan, Y.;

Zhou, Z.; Li, M.; Miao, S.; Li, J.; Zhu, Y.; Xiao, D.; He, T.; Yang, J.;

Qi, F.; Fu, Q.; Bao, X. Selective Conversion of Syngas to Light

Olefins. Science 2016, 351, 1065−1068.

(68) Gautier, S.; Sautet, P. Coadsorption of Butadiene and

Hydrogen on the (111) Surfaces of Pt and Pt₂Sn Surface Alloy:

Understanding the Cohabitation from First-Principles Calculations. J.

Phys. Chem. C 2017, 121, 25152−25163.

(69) Alves, J. A.; Bressa, S. P.; Martinez, O. M.; Barreto, G. F.

Kinetic Study of the Selective Catalytic Hydrogenation of 1,3-

Butadiene in a Mixture of n-Butenes. J. Ind. Eng. Chem. 2012, 18,

1353−1365.

(70) Fu, Q.; Luo, Y. Catalytic Activity of Single Transition-Metal

Atom Doped in Cu(111) Surface for Heterogeneous Hydrogenation.

J. Phys. Chem. C 2013, 117, 14618−14624.

(71) Yan, H.; Lv, H.; Yi, H.; Liu, W.; Xia, Y.; Huang, X.; Huang, W.;

Wei, S.; Wu, X.; Lu, J. Understanding the Underlying Mechanism of

Improved Selectivity in Pd(1) Single-Atom Catalyzed Hydrogenation

Reaction. J. Catal. 2018, 366, 70−79.

(72) Feng, Y.; Zhou, L.; Wan, Q.; Lin, S.; Guo, H. Selective

Hydrogenation of 1,3-Butadiene Catalyzed by a Single Pd Atom

Anchored on Graphene: The Importance of Dynamics. Chem. Sci.

2018, 9, 5890−5896.

7209

https://doi.org/10.1021/acscatal.1c01136

ACS Catal. 2021, 11, 7193−7209

Article Doi

Selective Butene Formation in Direct Ethanol-to-C3+-Olefin Valorization over Zn-Y/Beta and Single-Atom Alloy Composite Catalysts Using in Situ-Generated Hydrogen

DOI: 10.1021/acscatal.1c01136

Source and publish data:

Authors:

Article abstract of DOI:10.1021/acscatal.1c01136

Full text of DOI:10.1021/acscatal.1c01136

Products guided by the article

R&D Labs maybe for 106-99-0

Relevant to this article

Hot Product