Improving 1,3-butadiene yield by Cs promotion in ethanol conversion

Article abstract of DOI:10.1016/j.apcata.2017.05.025

Gas phase conversion of ethanol into butadiene was studied over silica-supported ZnO, ZrO₂ and ZnO-ZrO₂ catalysts in a fixed-bed reactor. Surface active sites were characterised using a variety of techniques including temperature-programmed desorption (TPD) of NH₃ and CO₂ as well as Fourier transform infrared (FTIR) spectroscopy of adsorbed pyridine. An increased concentration of acid and base sites was found in the following order: ZnO?2?2. In addition, new acid and base sites were generated when alkaline metal promoters were introduced. Typical reaction products for all catalysts include acetaldehyde, butadiene, ethylene, propylene, butenes, diethyl ether and C₄ oxygenates. Compared to single oxide supported catalysts, a remarkable acid-base synergetic effect was observed on the binary oxides supported catalysts with or without alkali metal modification. The improved catalytic activity and selectivity can be attributed to the right balance between acid and base sites, minimising dehydration to ethylene while promoting dehydrogenation to acetaldehyde. Furthermore, the existence of acid-base pairs with the appropriate configuration and strength promotes the aldol condensation and Meerwein-Ponndorf-Verley (MPV) reduction efficiently.

Full text of DOI:10.1016/j.apcata.2017.05.025

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Accepted Manuscript
Title: Improving 1,3-butadiene yield by Cs promotion in
ethanol conversion
Authors: Pratap T. Patil, Dapeng Liu, Yan Liu, Jie Chang,
Armando Borgna
PII:
S0926-860X(17)30233-8
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2017.05.025
APCATA 16247
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
18-1-2017
14-5-2017
24-5-2017
Please cite this article as: Pratap T.Patil, Dapeng Liu, Yan Liu, Jie Chang, Armando
Borgna, Improving 1,3-butadiene yield by Cs promotion in ethanol conversion, Applied
Catalysis A, Generalhttp://dx.doi.org/10.1016/j.apcata.2017.05.025
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Improving 1,3-butadiene yield by Cs promotion in ethanol conversion
Pratap T. Patil#, Dapeng Liu#, Yan Liu, Jie Chang, Armando Borgna*
Institute of Chemical and Engineering Sciences (ICES), A*STAR (Agency for Science, Technology
and Research), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore
# These authors contributed equally to this work
*Corresponding author, E-mail address: armando_borgna@ices.a-star.edu.sg
Tel: (+65) 67963802, Fax: (+65) 6316-6182
Graphical Abstract
Base sites
Acid-base pairs
Acid sites
C4 oxygenates
60
40
20
0
Ethylene
MeCHO
Butadiene
100
80
60
40
20
0
T = 400oC, WHSV = 1
ZnO
ZrO2
ZnO-ZrO2 Cs2O-ZnO-ZrO2
1

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Highlights


Alkali promotion inhibits ethanol dehydration to ethylene
Only Cs promotion provides the appropriate balance of acid-base pairs to carry out the
condensation step effectively

Cs is the most promising alkali-metal promoter.

A single-pass 1,3-butadiene yield of 54.6 % can be obtained over 0.5Cs2O-1ZnO-5ZrO2/SiO2 Catalyst.
2

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1
Introduction
Due to growing concerns on depletion of petroleum resources and climate change resulting
from the consumption of petrochemicals and fuels, last few decades have witnessed a renewed
interest in converting biomass-derived feedstocks into value-added chemicals [1]. Currently bio-
ethanol is being produced abundantly through biomass fermentation and its increased
availability opens up new opportunities for the synthesis of renewable bulk chemicals [2, 3].
Therefore, it became highly attractive to develop heterogeneous catalytic systems to effectively
convert ethanol to 1,3-butadiene (BDE), one of the most important chemical intermediates in
the production of various polymers (e.g. styrene-butadiene rubber, car tiers and plastics) [3, 4].
Currently BDE is obtained as a by-product during steam cracking of naphtha to make ethylene,
where an expensive separation by extractive distillation is required [5]. Although the current low
oil price strongly benefit this route for BDE production, the trend of shifting to lighter feedstocks
such as shale gas will significantly decrease the BDE yield, thus making on-purpose BDE even
more attractive and necessary.
Catalytic production of BDE from ethanol can be achieved through either one-step process
developed by Lebedev or a two-step process based on Ostromislensky reaction, which were
already known since early twentieth century. However both processes were stopped after 1960s
due to the lack of competitiveness with petrochemical-based routes [6]. Early investigation by
Union Carbide revealed that tantalum oxide and zirconium oxide gave decent selectivity toward
butadiene during ethanol conversion. Mixed oxide systems, including MgO-SiO2, ZnO-Al2O3,
ZrO2-SiO2 and ZnxZryOz were and still are widely investigated for the Lebedev synthesis [7-13].
Recent progress on catalyst development for converting ethanol to BDE in one or two-steps has
3