Impact of Alkali and Alkali-Earth Cations on Ni-Catalyzed Dimerization of Butene

Article abstract of DOI:10.1002/cctc.202000349

The presence of alkali (Na⁺ or Li⁺) or alkali-earth (Ca²⁺ or Mg²⁺) cations adjusting the acid-base properties on amorphous silica-alumina influences markedly the catalytic properties of supported Ni for 1-butene dimerization. The low concentration of Br?nsted acid sites on these catalysts reduces the double bond isomerization of butene and inhibits the formation of dimethylhexene as primary product. While the alkali and alkali-earth cations act as weak Lewis acid sites, only Ni²⁺ sites are catalytically active for dimerization of 1-butene. n-Octene and methylheptene are formed selectively as primary products; dimethylhexene is a secondary product. The open environment of the Ni²⁺ sites does not induce different reaction pathways compared to Ni²⁺ in the pores of zeolites.

Full text of DOI:10.1002/cctc.202000349

The European Society Journal for Catalysis
Supported by
Accepted Article
Title: Impact of alkali and alkali-earth cations on Ni-catalyzed
dimerization of butene
Authors: Andreas Ehrmaier, Laura Löbbert, Maricruz Sanchez-
Sanchez, Ricardo Bermejo-Deval, and Johannes Lercher
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To be cited as: ChemCatChem 10.1002/cctc.202000349
Link to VoR: https://doi.org/10.1002/cctc.202000349
01/2020

10.1002/cctc.202000349
ChemCatChem
FULL PAPER
Impact of alkali and alkali-earth cations on Ni-catalyzed
dimerization of butene
Andreas Ehrmaier[a], Laura Löbbert[a], Maricruz Sanchez-Sanchez[a], Ricardo Bermejo-Deval[a]*,
Johannes Lercher[a,b]
*
[a]
[b]
Lehrstuhl für Technische Chemie II, TU München, 85748 Garching, Germany
Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, United States
Corresponding address: Tel.: +49 89 289 13540; e-mail: ricardo.bermejo@tum.de, johannes.lercher@ch.tum.de
Supporting information for this article is given via a link at the end of the document
Abstract: The presence of alkali (Na+ or Li+) or alkali-earth (Ca2+ or
Mg2+) cations adjusting the acid-base properties on amorphous silica-
alumina influences markedly the catalytic properties of supported Ni
for 1-butene dimerization. The low concentration of Brønsted acid
sites on these catalysts reduces the double bond isomerization of
butene and inhibits the formation of dimethylhexene as primary
product. While the alkali and alkali-earth cations act as weak Lewis
acid sites, only Ni2+ sites are catalytically active for dimerization of 1-
butene. n-Octene and methylheptene are formed selectively as
primary products; dimethylhexene is a secondary product. The open
environment of the Ni2+ sites does not induce different reaction
pathways compared to Ni2+ in the pores of zeolites.
Results and Discussion
Synthesis and characterization of alkali and alkali earth
modified Ni/ASA catalysts
The concentration of Ni2+ and the respective co-cations are
compiled in Table 1. Amorphous silica-alumina was impregnated
with equal concentrations of Ni2+ and two different concentrations
of Na+, Ca2+, Li+, Mg2+. After calcination, NiO particles were
observed by XRD (Figure S1, S2). As derived from the width of
the XRD peaks, the average diameter of NiO particles increased
with increasing co-cation concentration. We hypothesize that the
well-dispersed co-cations interact stronger with ASA and so in
turn weaken the interaction between Ni2+ and ASA. This is
concluded to lead to a higher mobility of Ni2+ and, hence, to the
formation of larger NiO particles. Also on pure SiO2 larger NiO
particles were observed, highlighting the weak interactions
between the Ni2+ and silica. Transmission electron microscopy
(TEM) showed the formation of NiO particles, ranging from 10-
100 nm (Figure S3).
Introduction
The conversion of butenes from naphtha steam cracking is of high
[1]
interest to synthesize branched dimers, for gasoline additives
[1c], or into linear dimers [2], used as feedstock, e.g., for the
3]
production of PVC plasticizers.[1b, For the latter purpose, Ni
dispersed on amorphous silica-alumina (ASA) is used as a
catalyst, obtaining selectivities of approx. 60 % to linear and single
branched dimers (octene and methylheptene) and 40 % to
branched dimers (dimethylhexenes).[4]
The ASA support provides both Lewis and Brønsted acid sites,
enabling the dispersion and strong interaction of the Ni2+ cations.
They are the active sites for the dimerization of 1-butene,
following a Cossee-Arlman type mechanism.[5] However, isolated
Brønsted acid sites (BAS) catalyze the synthesis of branched
dimers, via the formation of secondary carbenium ions, as well as
by isomerization of 1-butene to 2-butene.[6]
Table 1. Loadings of Ni and the respective co-cations of the catalysts used in
this work. (Determined by AAS)
Catalyst
Ni conc.
[mmol g-1]
1.0
Co-cation conc.
[mmol g-1]
Ni/ASA
Ni-SiO2
1.0
1Na-Ni/ASA
1Ca-Ni/ASA
1Li-Ni/ASA
1Mg-Ni/ASA
2Na-Ni/ASA
2Ca-Ni/ASA
2Li-Ni/ASA
2Mg-Ni/ASA
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.7
1.1
1.4
0.8
2.3
2.5
2.8
2.9
Thus, high selectivity to linear octenes requires the elimination of
BAS via ion-exchange for alkali and alkali-earth cations.[7] This
step has shown to increase the selectivity in zeolite supported Ni2+
[5b, 8]
catalysts toward linear dimers with C3 or higher olefins.
The impregnation solely with Ni2+ cations decreased the BET
surface area of ASA from 645 to 403 m2/g (Figure S4, S5), the
micropore volume from 0.034 to 0.013 cm3/g and the mesopore
surface area from 689 to 422 m2/g. A minor relative decrease was
observed with respect to the Ni/ASA, with the co-cation
concentration (Figure S4 A and D), while the pore diameter
remained unchanged (Figure S4 B). The formation of larger NiO
particles in 2Li-Ni/ASA, together with lower BET surface area and
smaller mesopores, suggests a high dispersion of the Li cation on
the ASA support, blocking its pores.
However, the steric constraints in these catalysts has been
hypothesized to selectively stabilize the transition state of linear
dimers. [9] Thus, we decided to explore the role of the cations (in
their task to reduce Brønsted acidity) in the absence of pore
confinement. It is aimed to differentiate between intrinsic catalytic
properties of Ni2+ cations in the absence of Brønsted acid sites
without constraints of a microporous environment. The impact of
alkali and alkali-earth co-cations on a catalyst based on Ni2+
cations is explored, therefore, combining detailed acid-base
characterization and kinetic measurements.
1
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10.1002/cctc.202000349
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coordinatively bound to Lewis acid sites (LAS), while the band at
1454 cm-1 is attributed to pyridine adsorbed to Al3+ LAS (Al-LAS).
[10, 12]
The presence of Ni (Figure 1 B, top) hardly changed the total
concentration of pyridine bound to LAS and BAS (Figure S7), but
significantly influenced the nature of the Lewis acid sites. In
addition to the band at 1621 cm-1, a new band was observed at
1610 cm-1, indicative of sites with lower Lewis acid strength.[11a]
This band is assigned to pyridine coordinated to a Ni Lewis acid
site (Ni-LAS). A small shift was also detected from 1454 to 1450
cm-1. It is hypothesized that this is caused by the increase in
concentration of the weaker Ni-LAS. The adsorption of pyridine
on NiO/SiO2 (Figure 1 B, bottom) did not show coordinatively
adsorbed pyridine, indicating that pyridine adsorbs less strongly
on Ni-LAS. The SiO2 support does not possess LAS or BAS
detectable by adsorbed pyridine.
The co-impregnation of additional cations (Figure 1 A) led to minor
changes in the IR spectra. The 1621 cm-1 band, assigned to the
LAS of the ASA support (Al-Py), decreased in intensity. The band
at 1610 cm-1 (Ni-Py) assigned to the pyridine coordinated to Ni2+
cations did not change in intensity. However, an additional third
band in that region at lower wavenumbers was observed,
assigned to the interaction of pyridine with the co-cations. The
highest redshift was observed with the Na+ (19 cm-1), followed by
Ca2+, Li+ (being both of 10 cm-1) and Mg2+ (almost no red-shift).
The observed redshift is strongly correlated to the decrease in
Sanderson electronegativity of the different co-cations (Figure S8),
as following: Mg2+ (1.32), Ca2+(0.95), Li+(0.89) and Na+(0.84).[13]
In presence of co-cations the total acid site concentration was
significantly lower than on Ni/ASA (Figure 2). The concentration
of BAS decreased from 69 µmol/g with Ni/ASA to 0 µmol/g with
higher co-cation loading. Increasing concentrations of co-cations
decreased the concentration of LAS. The presence of alkali
cations (134 and 170 µmol/g with Na+ and Li+) had a stronger
impact than the presence of alkali earth cations (239 and 346
µmol/g with Ca2+ and Mg2+). Using the bands around 1600 cm-1 to
differentiate between Al-LAS and Ni-LAS (Figure 2, Table S1) it is
shown that in presence of Ni2+ almost 2/3 of the Lewis acidity was
associated with Ni sites. The increase in the concentration of co-
cations led to both a decrease in the concentration of both Al-LAS
and Ni-LAS. This suggests larger NiO particles in the presence of
the co-cations. A negligible concentration of BAS was observed
with all 2.5 mmol/g co-cation loaded samples, suggesting the full
exchange of the BAS protons by the alkali and alkali-earth cations.
Figure 1. IR spectra of pyridine adsorbed at T = 150 °C on Ni catalysts
containing ~2.5 mmol/g of different co-cations (A) and on co-cation free Ni/ASA
(B, top) as well as on the pure ASA support (B, middle) or on Ni-SiO2 (B, bottom).
Al-Py: pyridine adsorbed to Al LAS; Ni-Py: pyridine adsorbed to Ni LAS; M-Py:
pyridine adsorbed to co-cation LAS, B-Py: pyridine adsorbed to BAS; H-Py: H-
bonded pyridine.
The IR spectra of adsorbed pyridine were used to evaluate the
nature and concentration of acid sites (Figure 1, the 1.25 mmol/g
loaded samples are shown in Figure S6). Pyridine adsorption on
the parent ASA support (Figure 1 B, middle) led to the formation
of pyridinium ions with Brønsted acid sites (B-Py) at 1540 and
1637 cm-1.[10] In addition, pyridine hydrogen-bound to weak
hydroxyls was observed at 1575 cm-1 (H-Py).[10-11] The band at
1621 cm-1 is assigned to the 8a vibrational mode of pyridine
2
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Figure 2. Total concentrations of Lewis () and Brønsted () acid sites of 6 % Ni supported catalysts as a function of different concentrations of co-cations (A: Na-
Ni/ASA; B: Ca-Ni/ASA; C: Li-Ni/ASA; D: Mg-Ni/ASA), determined by deconvolution of the peaks at 1450 and 1540 cm-1, respectively. Additionally, the concentration
of Lewis acid sites is deconvoluted to Al-Lewis acid sites (Al-Py, , at 1621 cm-1), Ni-Lewis sites (Ni-Py, , at 1610 cm-1) and co-cation based Lewis acid sites (M-
Py, , at ~1600 cm-1).
variation in this process, except for a slight decrease in NiO
particle size (Figure S12).
Dimerization of 1-butene on supported Ni catalysts
The parent ASA was active in the dimerization of 1-butene,
A
forming only methylheptene and dimethylhexene. The catalyst
deactivated rapidly (Figure S9). In presence of Ni, the rates
increased from 0.12 to 3.17 molBut g-1 h-1, (Figure S9 and Figure
3) showing that the Ni2+ cations are highly active for dimerization.
Surprisingly, Ni-SiO2 was not active (Figure S10), suggesting that
the very large NiO particles are not active in 1-butene dimerization.
40
20
Figure 3 shows the conversion of 1-butene (Figure 3 A), as well
as the selectivity within the dimer fraction (Figure 3 B) for Ni/ASA.
The catalyst deactivated moderatrely, decreasing the conversion
from 36 % to 27 % within 15 hours. The selectivity to trimers and
tetramers was always below 20 % (Figure S11). The selectivity to
dimethylhexene (DMH) and methylheptene (MH) was similar
within the first hour (41 and 36 %, respectively). Over time on
stream (TOS), the selectivity to DMH decreased to 23 % and the
selectivity to MH increased to 52 %. The selectivity to n-octene
increased slightly from 18 to 21 %. The initial higher selectivity to
DMH and lower selectivity to MH and n-octene suggests the dimer
formation to be catalyzed by both Brønsted and Ni acid sites. The
proton catalyzed pathway occurs over a carbenium ion (Scheme
S1), and leads to the formation of branched dimers,[6b] as also
observed with the parent ASA (Figure S9). [14] The rapid change
in selectivity suggests that the BAS sites deactivate fast. To test
this hypothesis, the acid site concentration was measured after
the reaction (Figure 4) and the BAS concentration was found to
have decreased from 69 to 26 µmol/g. The Ni-LAS concentration
also decreased from 547 to 422 µmol/g, indicating that both BAS
and Ni-LAS were negatively affected by carbon deposits that
could be fully removed by calcination. X-ray diffraction analysis of
the sample before and after reaction did not indicate significant
0
B
Methylheptene
60
40
20
0
Dimethylhexene
Octene
Other C8
0
5
10
15
TOS / h
Figure 3. Conversion (A) and dimer selectivity (B) of dimerization of 1-butene
over a 6 % Ni / ASA supported catalyst (T = 160 °C, p = 50 bar, WHSV = 168 h-
1; MHSV = 12 molButene molBAS-1 s-1).
3
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The very low TOF of Na-Ni/ASA is attributed to a very low
concentration of Ni-LAS, the reasons for which is currently subject
of a separate investigation. Mg2+/ASA (without Ni, Figure S14) did
not show catalytic activity for 1-butene dimerization, leading to the
conclusion that alkali and alkali earth cations do not catalyze the
dimerization of 1-butene under the chosen reaction conditions.
Figure 5. Rate of butene dimerization as function of co-cation loading with 6 %
Ni on SiO2-Al2O3 (T = 160 °C, p = 50 bar, WHSVco-cation
= 6 h-1;
loaded catalysts
WHSVco-cation free catalyst = 1389 h-1).
0.2
Ca-Ni/ASA
Figure 4. A) IR spectra of adsorbed pyridine (1 mbar at 150 °C) and B)
concentration of acid sites of a 6 % Ni / ASA catalyst before and after performing
the dimerization reaction of 1-butene (T = 160 °C, 50 bar, WHSV = 168 h-1).
Na-Ni/ASA
Mg-Ni/ASA
Li-Ni/ASA
Impact of co-cations on Ni/ASA on 1-butene dimerization
0.1
Figure 5 shows that the dimerization rates decreased in the
presence of co-cations, i.e., from 3.17 molBut g-1 h-1 with Ni/ASA
to ~ 0.05-0.02 molBut g-1 h-1 (Figure S13). While a high deactivation
was observed with 2Li-Ni/ASA (70% within 7 hours), the other 2M-
Ni/ASA showed only minor deactivation (less than 10 % in 7
hours). Hence, a high dispersion of the Ni2+ cations on ASA and
the absence of Brønsted acid sites is required for high catalyst
stability. The reactivity decreased further with higher co-cation
loading, independent of the nature of the co-cations. This
dependence suggests on first sight that only BAS are active and
are gradually eliminated with higher concentration of alkali and
alkali-earth cations. On closer inspection one notes, however, that
the size of the NiO particles increases with co-cation
0
0
2
4
Co-cation loading / mmol g-1
Figure 6. Butene dimerization rate per Ni-Lewis acid sites over different co-
cation loaded catalysts with 6 % Ni on ASA (T = 160 °C, p = 50 bar, WHSV = 6
concentration (Figure S2), leading to
a reduction of the
h-1).
concentration of Ni-LAS that are hypothesized to be the
catalytically active sites, being Ni2+ cations at exchange positions
of the ASA support. Indeed, the rate normalized to the
concentration of Ni-LAS (TOF) increased with increasing co-
cation concentration (Figure 6) showing that the adjustment of the
acid-base properties of the support is beneficial. We tentatively
speculate that a higher base strength of the support and, hence,
a higher electron density at Ni-LAS (weaker Lewis acid strength)
is beneficial for the catalytic activity in 1-butene dimerization.
The selectivity to branched products (Figure 7) increased with
conversion in a subtly different manner in presence and absence
of co-cations. In their absence with Ni/ASA (Figure 7 A), initial
selectivities show that all three n-octene, methylheptene and
dimethylhexene are primary products that change non-linearly
with conversion. In the presence of co-cations (~2.5 mmol/g,
Figure 7 B) only n-octene and methylheptene are primary
products and dimethylhexene is a secondary product. While this
allows to conclude that the elimination of BAS also eliminates the
4
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direct formation of dimethylhexene, its rapid evolution with
conversion on co-cation modified Ni/ASA suggests the presence
of an alkali and alkali-earth cation catalyzed isomerization of 1-
butene. Considering, for example, the rates of isomerization for
2Mg-Ni/ASA and Ni/ASA (Figure S15), one notes a higher
isomerization/dimerization rate ratio in the presence of co-cations,
i.e., 0.3 for Ni/ASA and 6.0 for 2Mg-Ni/ASA, respectively. Indeed,
Mg on ASA (Mg/ASA) was active in butene isomerization,
demonstrating the catalytic activity of the co-cations. In the case
of Li-Ni/ASA, despite having NiO particles twice the size of the
other catalysts with similar co-cation loading, its catalytic
performance does not differ from the other catalysts, suggesting
the decrease in BAS concentration is the main driving force
changing catalytic activity.
transition state of butene dimers, especially those leading to the
formation of n-octene and methylheptene.
In the absence of BAS we hypothesize that 1-butene is dimerized
in a Cossee-Arlman type mechanism with the adsorption of 1-
butene on Ni-H and a subsequent insertion and coordination of
another butene molecule into the Ni-C bond.[2a, 15] Thereby, in the
formation of n-octene and methylheptene the initial adsorption
would take place as 1,2-insertion into the Ni-H (Scheme 1, left
pathway). The subsequent coordination of another 1-butene to
the Ni-C bond determines whether n-octene (by 2,1-insertion) or
methylheptene (by 1,2-insertion) is formed. The initial 2,1-
insertion of 1-butene leads to a branched dimer. Because
dimethylhexene is not a primary product in presence of alkali and
alkali earth cations, this route can be ruled out.
Scheme 1 Reaction pathways for the formation of the different products (octene,
methylheptene and dimethylhexene) with 1-butene and 2-butene catalyze by a
Ni-H from Cossee-Arlman site.
As isomerization of 1-butene into cis- and trans-2-butene is
occurring, the product 2-butene would adsorb via a 2,3-insertion
into the Ni-H, opening this pathway for dimerization (Scheme 1,
right pathway, red). This would also lead to the formation of
dimethylhexene by subsequent 2,3-insertion. The 2,1 insertion of
1-butene into the Ni-C (formed by 2-butene) results in this case in
a secondary pathway in the formation of methylheptene.
Figure 7. Selectivity of dimers as function of 1-butene conversion over co-cation
free Ni (6 wt%) supported catalyst (A) and different co-cation loaded Ni (6 wt%)
supported catalysts (B). T = 160 °C, p = 50 bar, WHSV A = 1388 h-1, WHSV B
=
Conclusion
6 – 50 h-1.
The catalytically active sites for 1-butene dimerization have been
identified as accessible Ni2+ on ASA (Ni-LAS). Ni2+ cations in NiO
supported on SiO2 have not been found to have sufficiently high
catalytic activity to lead to measurable conversions under the
present reaction conditions. The presence of alkali (Na+ or Li+)
and alkali-earth (Ca2+ or Mg2+) co-cations on Ni/ASA blocks BAS
that catalyze 1-butene dimerization. This is attributed to an
increase in the local base strength. As a negative side effect, the
particle size of the supported NiO particles increased, decreasing
the concentration of Ni2+ cations at exchange positions of the ASA
support active in butene dimerization. The alkali- and alkali earth
In the absence of steric constraints, the butene dimerization rates
and selectivity to linear dimers differ from the micro- mesoporous
environments. The butene dimerization rates for M-Ni/ASA were
almost an order of magnitude lower (0.05-0.015 molBut g-1 h-1) than
in our previous work with M-Ni/LTA (0.13-0.11 molBut g-1 h-1). In
addition, at 35% conversion selectivities below 10% to
dimethylhexene were observed with M-Ni/LTA within the C8
fraction, while with M-Ni/ASA selectivities to dimethylhexene were
around 35-40%. Therefore, we conclude that steric constraints
surrounding the active Ni site are able to better stabilize the
5
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10.1002/cctc.202000349
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cations increase the initial selectivity to n-octene and
methylheptene (x < 10%). The co-cations increase, however, also
the rate of 1-butene isomerization to 2-butene. In turn, this leads
to a rapid increase in the formation rate and selectivity to dimethyl
hexene. Thus, we conclude that alkali and alkali earth cations are
suitable to block BAS catalyzed dimerization of 1-butene, but their
ability to induce isomerization of 1-butene does not allow for
selective dimerization at higher conversions. Investigations to
eliminate this pathway by organic co-reactants (poisons) are
under way.
the bands at 1600 cm-1 region were fitted, assuming similar extinction
coefficients for all bands of LAS.
Catalytic reactions and kinetics. Catalytic tests were conducted in a
fixed bed PFR (id = 3.9 mm), connected to an online GC (Agilent HP 6890,
equipped with a 50 m HP-1 column). Prior to GC analysis, H2 was added
to the product stream, which is hydrogenated over a Pt/Al2O3 catalyst. A
mixture of 15 % i-butane and 85 % 1-butene is introduced by a syringe
pump (ISCO model 500 D), temperature is controlled by a Eurotherm 2416
and pressure is controlled using a Tescom backpressure regulator.
Prior to weighing, the catalyst was dried at 100 °C for 1 h. The catalyst bed
was diluted with SiC and fixed in the isothermal zone of the reactor. After
activation for 2 h at 450 °C (rate: 10 °C/min) in air, the system was purged
with N2 and pressurized to the desired pressure. Subsequently, the system
was flushed with the feed mixture (5 ml/min) for 2 min. After the desired
flow rate was set, temperature program and GC measurements were
started.
Experimental Section
Catalyst preparation. The catalysts were prepared by incipient wetness
impregnation (IWI) of an amorphous ASA support (Sigma-Aldrich, ASA
catalyst support, Si/Al = 5.5) material with the aqueous solutions
containing all the respective metal salts. The following metal salts were
used in the impregnation: Ni(NO3)2 (Sigma-Adlrich; > 97.0 %), Mg(NO3)2
(Sigma-Adlrich; > 99.0 %), Ca(NO3)2 (Merck; > 99.0 %), LiNO3 (Sigma-
Standard measurement conditions were at 160 °C and 50 bar with a flow
rate of butene mixture of 0.04 and catalyst loading of 200 mg to obtain a
WHSV of 6 g g-1 h-1. The space velocity was varied by changing the
catalyst loading and the feed flow rate. The reported
rates/conversion/selectivities were obtained after 1 hour on TOS.
Adlrich;
> 99.0 %), and NaNO3 (Sigma-Adlrich; > 97.0 %). The
concentration of the solution was tuned accordingly to the desired metal
concentration. The respective co-cation was mixed in the Ni containing
impregnation solution, resulting approximately in concentrations of 1
mmol/g Ni and/or ~1.25 mmol/g (nomenclature: 1X-Ni/ASA , X=Na, Li, Ca,
Mg) or ~2.5 mmol/g (nomenclature: 2X-Ni/ASA , X=Na, Li, Ca, Mg) of the
respective co-cations. After impregnation, the catalyst precursors were
dried overnight at 80 °C and subsequently calcined (8 h, rate: 5 °C/min, up
to 500 °C in air).
i-Butane is inert under reaction conditions applied, and was used as
internal standard for normalization of GC areas. Conversion, selectivity
and yields are calculated according to the following equations:
풏(풃풖풕풆풏풆)풊풏 − 풏(풃풖풕풆풏풆)풐풖풕
Characterization. Atomic absorption spectroscopic measurements (AAS)
were performed in a Solar M5 Dual Flame graphite furnace AAS from
ThermoFisher. After drying at 250 °C for 24 h, the samples were dissolved
in a mixture of HF and nitric acid and injected in the graphite furnace. A
previous calibration was applied to determine the concentration of each of
the metals.
푿 =
풏(풃풖풕풆풏풆)풊풏
|
|
흂풃풖풕풆풏풆
풏(풑풓풐풅풖풄풕)풐풖풕
푺 =
풏(풃풖풕풆풏풆)풊풏 − 풏(풃풖풕풆풏풆)풐풖풕 흂풑풓풐풅풖풄풕
|
|
풏(풑풓풐풅풖풄풕)풐풖풕 흂풃풖풕풆풏풆
X-ray diffraction measurements were performed in a PANalytical
Empyreal System diffractometer, equipped with a Cu- Kα radiation
source (Kα1 line of 1.54 Å; 45 kV and 40 mA)). The diffractograms were
measured by the usage of a sample spinner stage in a 2θ range between
5 ° and 70 ° (step size: 0.0131303/2 ) at ambient conditions.
The BET specific surface area and pore volume of the zeolite were
determined by N2 sorption. The isotherms were measured at liquid N2
temperature (77 K) using a PMI automatic sorptometer. The catalyst was
activated in vacuum at 473 K for 2 h before measurement. Apparent
surface area was calculated by applying the Brunauer-Emmett-Teller
(BET) theory with a linear regression between p/p0 = 0.01 – 0.15. The
micro- and mesopores were determined from the t-plot linear regression
for t = 5-6 Å.
풀 =
풏(풃풖풕풆풏풆)풊풏 흂풑풓풐풅풖풄풕
Other C8” are unspecified dimethylhexene and methylheptene isomers,
different from those shown in Scheme 1
Acknowledgements
J.A.L was supported by the U.S. Department of Energy (DOE),
Office of Science, Office of Basic Energy Sciences (BES),
Division of Chemical Sciences, Geosciences and Biosciences
(Transdisciplinary Approaches to Realize Novel Catalytic
Pathways to Energy Carriers, FWP 47319). RBD would like to
acknowledge the Humboldt foundation for the financial support.
The adsorption of pyridine was followed by IR in a Nicolet 5700 FT-IR
spectrometer, equipped with
a liquid N2 cooled detector. For the
measurement, a self-supporting wafer was loaded and activated at 450 °C
(rate: 10 °C/min) for 1 h in vacuum. After cooling down to 150 °C, pyridine
was equilibrated to 1 mbar for 30 min. Subsequently, the system was
evacuated for another 30 min, before measurements. Scans were taken
after activation and after outgassing at a resolution of 0.4 cm-1 with an
average of 250 scans per spectrum. For the calculation of the acid site
concentrations, molar extinction coefficients of 0.96 and 0.73 cm/µmol and
were used for the characteristic bands of 1450 cm-1 (Lewis) and 1540 cm-
1 (Brønsted),[16] respectively. For the deconvolution of the Lewis acid sites,
Keywords: Dimerization, Butene Isomerization, Nickel, Silica-
Alumina (ASA), Cossee-Arlman
[1]
a) G. C. Bailey, J. A. Reid, 1952; b) A. Behr, Z. Bayrak, S.
Peitz, G. Stochniol, D. Maschmeyer, RSC Advances 2015,
6
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10.1002/cctc.202000349
ChemCatChem
FULL PAPER
5, 41372-41376; c) S. Albrecht, D. Kießling, G. Wendt, D.
Maschmeyer, F. Nierlich, Chem. Ing. Tech. 2005, 77, 695-
709.
[2]
[3]
a) E. J. Arlman, J. Catal. 1964, 3, 89-98; b) P. Beltrame, L.
Forni, A. Talamini, G. Zuretti, Appl. Catal. A 1994, 110, 39-
48; c) K. Ziegler, E. Holzkamp, H. Breil, H. Martin, Angew.
Chem. 1955, 67, 541-547.
a) A. Brückner, U. Bentrup, H. Zanthoff, D. Maschmeyer, J.
Catal. 2009, 266, 120-128; b) J. Rabeah, J. Radnik, V.
Briois, D. Maschmeyer, G. Stochniol, S. Peitz, H. Reeker,
C. La Fontaine, A. Brückner, ACS Catalysis 2016, 6, 8224-
8228; c) F. Nadolny, B. Hannebauer, F. Alscher, S. Peitz,
W. Reschetilowski, R. Franke, J. Catal. 2018, 367, 81-94.
S. Raseev, Thermal and Catalytic Processes in Petroleum
Refining, Marcel Dekker, Inc., New York, 2003.
a) A. Ehrmaier, Y. Liu, S. Peitz, A. Jentys, Y.-H. C. Chin, M.
Sanchez-Sanchez, R. Bermejo-Deval, J. Lercher, ACS
Catalysis 2019, 9, 315-324; b) A. N. Mlinar, O. C. Ho, G. G.
Bong, A. T. Bell, ChemCatChem 2013, 5, 3139-3147.
a) N. Kumar, P. Mäki-Arvela, T. Yläsalmi, J. Villegas, T.
Heikkilä, A. R. Leino, K. Kordás, T. Salmi, D. Yu Murzin,
Microporous Mesoporous Mater. 2012, 147, 127-134; b) M.
L. Sarazen, E. Doskocil, E. Iglesia, J. Catal. 2016, 344, 553-
569.
a) H. S. Sherry, H. F. Walton, The Journal of Physical
Chemistry 1967, 71, 1457-1465; b) H. S. Sherry, Handbook
of Zeolite Science and Technology, Marcel Dekker, New
York 2003, 1007-1061; c) D. Amari, J.-L. Ginoux, L.
Bonnetain, Zeolites 1994, 14, 58-64.
[4]
[5]
[6]
[7]
[8]
a) A. N. Mlinar, S. Shylesh, O. C. Ho, A. T. Bell, ACS
Catalysis 2013, 4, 337-343; b) B. Nkosi, F. T. T. Ng, G. L.
Rempel, in Stud. Surf. Sci. Catal., Vol. 97 (Eds.: L.
Bonneviot, S. Kaliaguine), Elsevier, 1995, pp. 385-392; c)
B. Nkosi, F. T. T. Ng, G. L. Rempel, Appl. Catal. A 1997,
158, 225-241.
[9]
a) A. Ehrmaier, R. Bermejo-Deval, M. Sanchez-Sanchez, Y.
Liu, J. A. Lercher, S. Peitz, G. Stochniol, Vol. EP 3 366 643
A1 (Ed.: EPOrg), EVONIK Degussa GmbH, Technische
Universität München, 2018; b) A. Ehrmaier, S. Peitz, M.
Sanchez-Sanchez, R. Bermejo de Val, J. Lercher,
Microporous Mesoporous Mater. 2019, 284, 241-246.
G. Ertl, H. Knözinger, F. Schueth, J. Weitkamp, Handbook
of Heterogeneous Catalysis, Vol. 1, Wiley-VCH Verlag
GmbH & Co. KGaA, Weinheim, 2008.
a) C. Morterra, G. Magnacca, Catal. Today 1996, 27, 497-
532; b) H. Knözinger, H. Stolz, Fortschrittsberichte über
Kolloide und Polymere 1971, 55, 16-28; c) H. Stolz, H.
Knözinger, Kolloid-Zeitschrift und Zeitschrift für Polymere
1971, 243, 71-76.
[10]
[11]
[12]
a) M. Zaki, M. Hasan, F. Al-Sagheer, L. Pasupulety, In situ
FTIR Spectra of Pyridine Adsorbed on SiO2-Al2O3, TiO2,
ZrO2 and CeO2: General Considerations for the
Identification of Acid Sites on Surfaces of Finely Divided
Metal Oxides, Vol. 190, 2001; b) C. H. Kline, J. Turkevich,
The Journal of Chemical Physics 1944, 12, 300-309.
R. T. Sanderson, J. Chem. Educ. 1988, 65, 112.
[13]
[14]
M. L. Sarazen, E. Iglesia, Proceedings of the National
Academy of Sciences 2017, 114, E3900-E3908.
[15]
[16]
P. Cossee, J. Catal. 1964, 3, 80-88.
S. M. Maier, A. Jentys, J. A. Lercher, The Journal of
Physical Chemistry C 2011, 115, 8005-8013.
7
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FULL PAPER
Entry for the Table of Contents
The presence of alkali (Na+ or Li+) or alkali-earth (Ca2+ or Mg2+) cations adjusting the acid-base properties
on amorphous silica-alumina influences markedly the catalytic properties of supported Ni for 1-butene
dimerization. n-Octene and methylheptene are formed selectively as primary products; dimethylhexene
is a secondary product. The open environment of the Ni2+ sites does not induce different reaction pathways
compared to Ni2+ in the pores of zeolites.
Ni
Constant rate per
Ni Lewis acid site
Al
Al
Al
Al
Al
Al
Al
Al
Lewis acid sites
Metal oxide sites
Ni + Co-Cations
8
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