Study On The Effect Of Copper-zinc-aluminum Catalyst Pretreatment On Its Catalytic Hydrogenation To Methanol Performance

The continuous emission of carbon dioxide(CO2)has triggered a greenhouse effect that has seriously threatened the human living environment,and the fossil fuels on which human beings depend for their survival have been increasingly depleted with the development of society.Methanol has become an important substitute for non-renewable energy due to its importance in the chemical industry and its own use as a ring of high-quality clean energy.Therefore,the catalytic CO2 hydrogenation of methanol has become an effective way to utilize CO2 resources and produce renewable energy,and the development of efficient and stable catalysts to improve catalyst activity and methanol selectivity has become the top priority of the research.This paper treats the Cu-ZnO-Al2O3(CZA)catalyst to improve its catalytic performance in the CO2 hydrogenation to methanol reaction,treat it by formic acid,hydroxylamine hydrochloride and triethoxy(octyl)silane(TEOOS),and then regulate the valence state of Cu species in the catalyst and the interaction between Cu particles and various elements,prepare different catalysts,apply them to the study of catalytic CO2 hydrogenation to methanol.The specific research contents and results are as follows:(1)Formic acid pretreatment CZA catalyst:the use of formic acid and metal to form a formic acid chelate in the calcination process to release the reducing gas CO,and the redox reaction with Cu2+,thereby regulating the valence state of Cu element,and improving the interaction between the components in the catalyst,increasing the medium and strong alkaline site of the catalyst,the investigation found that under the reaction conditions of 200℃,3.0 Mpa,when HCOOH/Cu=0.8,the CO2 conversion rate was 6.7%and the CH3OH selectivity was 76.3%,at which time the highest methanol yield was obtained 5.1%.And after 48 h of the reaction,the catalyst activity is still active,indicating that it has good stability.(2)Hydroxylamine hydrochloride pretreatment CZA catalyst:Using hydroxylamine hydrochloride as reducing agent,CZA catalyst was prepared by precipitation reduction method.Through XRD,BET,SEM,H2-TPR,XPS,CO2-TPD,TGA,N2O titration and other characterization,it was found that hydroxylamine hydrochloride treatment increased the specific surface area of copper and copper dispersion of the catalyst,and with the increase of the amount of hydroxylamine hydrochloride.Cu2+in the catalyst is gradually reduced to Cu+.The reduction temperature of catalyst gradually moved to low temperature,indicating that hydroxylamine hydrochloride treatment is helpful to the reduction of catalyst.In addition,the adsorption capacity of CO2 on the catalyst also increased.The catalytic activity evaluation results showed that compared with CZA catalyst,the CO2 conversion and CH3OH selectivity were improved.(3)TEOOS treatment of CZA catalyst After the TEOOS treatment,the catalyst has obvious hydrophobic properties,on the one hand,it can isolate the water molecules generated in the reaction in time and accelerate the production of methanol.On the other hand,it can prevent water from trapping on the surface of the catalyst and protect the catalyst from the poisoning of the water produced by the reaction.XRD,BET and SEM were characterized on the prepared catalysts,and the results showed that the structure of the catalysts did not change before and after the modification,indicating that the hydrophobic modification had no effect on the structure of the catalysts.Its properties were explored by H2-TPR,XPS,CO2-TPD,TGA,FTIR,and N2O titration.The results of the activity evaluation showed that the CO2 conversion rate of the hydrophobic CZA-T catalyst was higher and the selectivity change was smaller,but the total methanol yield was improved.