The Research Of Ethanol To 1,3-Butadiene Over Multifunctional Catalysts

The reserves of fossil energy are non-renewable and their use increases the amount of CO₂ emissions in the atmosphere,the environment is deteriorating.Therefore,it has become a research hotspot in the field of energy and chemical engineering to find alternative methods to convert fossil fuels such as petroleum into chemical substances.The selective bio-ethanol cascade transformation to hydrocarbons over multifunctional catalysts is a highly promising sustainable pathway to high-value chemicals and fuels,so it’s been studied extensively.The design of a catalyst to regulate the selectivity of bio-ethanol conversion is the alternative route of many researchers and needs to be further studied.In this work,MgO-SiO₂ catalysts with different zinc loadings were prepared and investigated for their Zn loading-dependent selectivity of the bio-ethanol transformation,moreover catalytic transformation of ethanol has been studied over the different loading-sequence of ZnNaZr catalysts,in which the following findings are believed to be significant to the general catalysis community and bio-ethanol transformation study:（1）MgO-SiO₂ composite catalysts with low ZnO loadings tend to show an enhanced efficiency for C-C bond coupling and exceptionally high selectivity to 1,3-butadiene whereas the high ZnO loadings favor the formation of acetaldehyde via dehydrogenation.Thorough analysis of characterization results via XRD,BET,IR,TPD,TGA and ²⁹Si MAS NMR indicates that ZnO loading influences the extent of MgO and SiO₂ interaction during preparation,and the surface acid-base chemistry,which were both found to correlate with the catalytic performance.This study proposes that the Mg-O-Si interfacial structure formed by the strong MgO and SiO₂ interaction at low ZnO loadings is of prime importance for the formation of 1,3-butadiene,benefiting from the desirable properties of balanced dehydrogenation and C-C bond coupling while excess ZnO loadings destroy the Mg-O-Si interfacial bonds over the MgO-SiO₂ composite catalysts,which are the key structures required for C-C bond growth.（2）Ethanol-TPD experiments were carried out over a chemisorption instrument coupled with mass spectrometry to explored the interaction of ethanol molecule with the surface of the ZnMgSi catalysts.Ethanol conversion studies demonstrated that the catalysts with smaller Zn loading tend to be selective for the specific cascade formation of 1,3-butadiene whereas the catalysts with higher Zn loading favor the acetaldehyde formation.On the other hand,the influence of ZnO on the acidic and basic sites on the catalyst surface was investigated by the IPA-TPD experiment,and the change of acid-base strength on the surface of ZnMgSi catalyst was determined.（3）A series of ZnNaZr catalysts of the different loading-sequence were prepared by impregnation method,and the catalysts were characterized and tested for their catalytic activity.These results show that the loading-sequence of Zn-Na（F）/Zr could improve the dispersion of Zn on Zr O₂ carrier and change the redox performance of the catalyst,thus the yield of 1,3-butadiene is increased.The loading-sequence is shown to be the key structure-selectivity indicator in this cascade bio-ethanol transformation,and exceptional control over the catalytic product selectivity by tuning the loading-sequence of metal oxide promoters.The purpose of this work is not only to investigate the effect of different ZnO loadings on the selectivity control of desirable products on ZnMgSi composite catalyst,but also to improve the fundamental understandings about the interfacial effect of mixed metal oxide catalysts on ethanol conversion,and provide a new idea for the design of efficient complex cascade reaction catalysts.