Effect Of The Polyethylene Glycols Medium On Catalytic Performance For The Ethanol Synthesis From Syngas In Slurry Reactor

Ethanol as a kind of high quality liquid fuel is considered to be one of the best alternative fuels, and has been widely used in the synthesis of raw materials as well as other applications. At present, synthesis of ethanol from syngas(CO+H2) is one of the important ways for cleaning utilization of coal resources. Also, it is a kind of promising synthetic industry, creating more economic value.The complete liquid-phase method was put forward by our group. It was used to prepare the Cu-based catalyst for CO hydrogenation reaction. During this process, we found that catalyst has higher selectivity of ethanol, but the reproducibility is poor. Our group used liquid paraffin as heat treatment medium and reaction medium in the previous work. Now with the green chemistry putting forward, the reaction medium has been attracted more and more attention as a research field. Thus, polyethylene glycol(PEG) was used as heat treatment medium and reaction medium in this paper. The effect of different molecular weight of polyethylene glycol medium, several molar ratios of Cu ZnAl and the cross reaction using PEG600 and liquid paraffin as medium on catalytic performances and catalyst structure were explored. The catalysts were characterized by powder X-ray diffraction(XRD), H2 temperature-programmed reduction(H2-TPR), temperature-programmed desorption of ammonia(NH3-TPD), N2 adsorption, X-ray photoelectron spectroscopy, temperature-programmed desorption of hydrogen(H2-TPD) and temperature-programmed desorption of carbon monoxide(CO-TPD), the conclusions are made as follows:1. When PEG was adopted as the slurry bed reaction medium, ethanol was an unexpected product over the C302 catalyst, and using PEG600 as reaction medium, the activity tests showed that ethanol selectivity reached up to 25.21%2. CuZnAl catalyst using PEG600 as heat treatment medium and reaction medium, whose molar ratio is 2:1:0.8, exhibited higher CO conversion and ethanol selectivity reached up to 33.49% and 35.49%.3. Catalysts prepared by complete liquid-phase technology using PEG600 and liquid paraffin as mediums in the cross reaction have different product distribution and catalyst structure. Activity tests further confirmed that ethanol was not produced by decomposition of polyethylene glycol, it was also found that the introduction of liquid paraffin could improve the catalyst stability, but it also suppressed the generation of ethanol.4. The Cu-Zn-Al catalyst with high ethanol selectivity has the following characteristics: the existence of anti-reducibility Cu+ in the catalyst is conductive to forming the synergy between Cu+ and Cu0; the existence of larger amount of weak acid on the catalyst surface; the Zn is enriched on the surface; Also, the bigger pore size of catalysts or the increase of pore size on catalysts in the process of reaction is conductive to the diffusion of reaction molecules in the pore canal and promoting the synthesis of ethanol.5. In this paper,the usage of PEG broadens the application field of complete liquid-phase technology and enriches preparation technique for catalyst Also the appearance of ethanol in product provides a new way of thinking for ethanol synthesis from syngas.