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Recent Breakthroughs in the Conversion of Ethanol to Butadiene

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Recent Breakthroughs in the Conversion of Ethanol to Butadiene catalysts Review Recent Breakthroughs in the Conversion of Ethanol to Butadiene Guillaume Pomalaza 1, Mickaël Capron 1, Vitaly Ordomsky 1,2 and Franck Dumeignil 1,* 1 University Lille, CNRS, Centrale Lille, ENSCL, University Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France; [email protected] (G.P.); [email protected] (M.C.); [email protected] (V.O.) 2 Eco-Efficient Products and Processes Laboratory (E2P2L), UMI 3464 CNRS-Solvay, Shanghai 201108, China * Correspondence: [email protected]; Tel.: +33-(0)3-20-43-45-38 Academic Editor: Yu-Chuan Lin Received: 30 October 2016; Accepted: 6 December 2016; Published: 13 December 2016 Abstract: 1,3-Butadiene is traditionally produced as a byproduct of ethylene production from steam crackers. What is unusual is that the alternative production route for this important commodity chemical via ethanol was developed a long time ago, before World War II. Currently, there is a renewed interest in the production of butadiene from biomass due to the general trend to replace oil in the chemical industry. This review describes the recent progress in the production of butadiene from ethanol (ETB) by one or two-step process through intermediate production of acetaldehyde with an emphasis on the new catalytic systems. The different catalysts for butadiene production are compared in terms of structure-catalytic performance relationship, highlighting the key issues and requirements for future developments. The main difficulty in this process is that basic, acid and redox properties have to be combined in one single catalyst for the reactions of condensation, dehydration and hydrogenation. Magnesium and zirconium-based catalysts in the form of oxides or recently proposed silicates and zeolites promoted by metals are prevailing for butadiene synthesis with the highest selectivity of 70% at high ethanol conversion. The major challenge for further application of the process is to increase the butadiene productivity and to enhance the catalyst lifetime by suppression of coke deposition with preservation of active sites. Keywords: butadiene; ethanol; acetaldehyde; ETB; condensation; catalyst; oxide 1. Introduction 1.1. Scope of the Review 1,3-butadiene (butadiene, BD or C4H6) is essential to the production of numerous elastomers, such as styrene-butadiene rubber, polybutadiene, acrylonitrile-butadiene-styrene and others [1–3]. It is also used as a reagent in organic chemistry, particularly in Diels-Alder reaction [2]. At present, butadiene is predominantly extracted from the C4 steam cracker fractions [2]. Because the butadiene yield depends largely on the nature of the feedstock of the steam cracker, butadiene production is susceptible to market instability or trends in the petroleum industry, notably the emergent use of shale gas, which may lead to BD shortages [4]. The scarcity of greenhouse gas-emitting fossil fuel reserves is another long-term issue with the current butadiene production method, both in terms of commercial and environmental sustainability. These matters have recently renewed an interest in the century-old heterogeneous catalytic conversion of ethanol to butadiene in which gaseous ethanol is primarily transformed to BD over multifunctional materials. Scientific development in the production of ethanol from biomass, coupled with state subsidies and mandates, have greatly increased the global output and affordability of bioethanol. Due to its Catalysts 2016, 6, 203; doi:10.3390/catal6120203 www.mdpi.com/journal/catalysts Catalysts 2016, 6, 203 2 of 35 limited use as a fuel for combustion engines, an excess of bioethanol is expected. For this reason, it is believed that ethanol would make an ideal platform molecule for the synthesis of value-added Catalysts 2016, 6, 203 2 of 35 chemicals, namely butadiene [5]. A recent publication by Bell et al. has detailed the conditions under whichlimited theuse industrialas a fuel for use combustion of butadiene engines, from an bioethanol excess of bioethanol would reduce is expected. greenhouse For this gasreason, emissions; it is the keybelieved is believed that toethanol be the would use of make low-carbon an ideal emittingplatform ethanolmolecule sources for the [synthesis3]. Another of value case‐added study by Burla etchemicals, al. has outlinednamely butadiene that the [5]. conversion A recent publication of ethanol by and Bell acetaldehyde et al. has detailed into the butadiene conditions would under be profitablewhich under the industrial certain given use of circumstances; butadiene from butadienebioethanol would production reduce in greenhouse the Gulf coast gas emissions; of the USA the can be expectedkey is tobelieved be very to be profitable the use of as low long‐carbon as ethanol emitting remains ethanol below sources $3.0/gallon [3]. Another [ case6]. study by Burla et al. has outlined that the conversion of ethanol and acetaldehyde into butadiene would be profitable Despite having been successfully implemented in the past, it is recognized that productivity under certain given circumstances; butadiene production in the Gulf coast of the USA can be expected levels ofto currentbe very profitable ethanol-to-butadiene as long as ethanol technology remains are below not $3.0/gallon yet sufficient [6]. to insure economic viability [7]. To meet theDespite increasing having demand been successfully for BD in the implemented face of eventual in the scarcity, past, it is the recognized aim of the that ongoing productivity scientific researchlevels is to of improve current ethanol the performances‐to‐butadiene of technology the catalysts are not being yet developed.sufficient to insure economic viability In[7]. the To literature, meet the theincreasing ethanol-to-butadiene demand for BD (ETB)in the face reaction of eventual is referred scarcity, to by the different aim of the names ongoing due to the twoscientific processes research by which is to itimprove was historically the performances industrialized. of the catalysts The one-step being developed. process (or Lebedev process) refers to theIn direct the literature, gas-phase the ethanol conversion‐to‐butadiene of ethanol (ETB) to reaction butadiene is referred over active to by materials.different names The due two-step to processthe (or two Ostromislensky processes by which process) it was refers historically to the conversion industrialized. to butadiene The one‐ ofstep an process ethanol/acetaldehyde (or Lebedev gaseousprocess) mixture refers previously to the direct obtained gas‐phase by partial conversion dehydrogenation of ethanol to ofbutadiene ethanol. over Because active the materials. two processes The two‐step process (or Ostromislensky process) refers to the conversion to butadiene of an have been recognized to undergo the same reaction pathway, both can be studied conjointly. BD ethanol/acetaldehyde gaseous mixture previously obtained by partial dehydrogenation of ethanol. synthesisBecause through the two the one-stepprocesses process have been usually recognized results to inundergo the production the same reaction of acetaldehyde pathway, as both a byproduct can be of the reaction,studied conjointly. which has BD to synthesis be recycled through in the the system one‐step in process the case usually of implementation results in the production in an industrial of process.acetaldehyde Thus, even as in a thebyproduct one step of the process reaction, it is which necessary has to to be test recycled feeds in containing the system acetaldehydein the case of in order toimplementation assess the behavior in an industrial of the process. catalytic Thus, system even in in acetaldehyde-containingthe one step process it is necessary mixtures, to test however, feeds in lowercontaining amounts acetaldehyde compared to in the order two-step to assess process. the behavior of the catalytic system in acetaldehyde‐ Havingcontaining been mixtures, discovered however, more in than lower a century amounts ago, compared research to the on two the‐step ETB process. reaction is abundant, but scattered overHaving different been discovered time periods. more Fortunately,than a century the ago, dispersed research on literature the ETB reaction has been is abundant, summarized but in reviewscattered articles [over4,8– 10different]; the reader time periods. is referred Fortunately, to these publicationsthe dispersed forliterature details has concerning been summarized the history in of review articles [4,8–10]; the reader is referred to these publications for details concerning the history the reaction, its fundamental principles, including mechanistic and thermodynamic considerations, of the reaction, its fundamental principles, including mechanistic and thermodynamic considerations, the manythe many catalytic catalytic systems systems studied studied and and the the issues issues regarding the the design design of new of new catalysts. catalysts. Marked Marked by by thethe publication publication of of “Investigation “Investigation into into the the conversion conversion of ethanol of ethanol into 1,3 into‐butadiene” 1,3-butadiene” in 2011 by in Jones 2011 by Jones etet al. al. [ 11[11]] thethe pacepace of scientific scientific progress progress in inthe the field field of the of theethanol ethanol-to-butadiene‐to‐butadiene conversion conversion has has accelerated,accelerated, as illustrated illustrated in inFigure Figure 1, which1, which indicates indicates the number the numberof publications of publications on the ethanol on‐to
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