Experimental Research On Direct Ethanol Synthesis From Syngas

The usage of syngas as raw material gas to obtain ethanol(EtOH)from dimethyl ether(DME)and methyl acetate(MA)has attracted extensive attention and research by researchers,and is considered to be a promising ethanol synthesis process route.However,the existing technology requires a multi-stage reaction to obtain ethanol,and the process flow is pretty complicated.In this thesis,the catalyst was multi-functionalized,and the reactions of syngas to dimethyl ether,dimethylation of dimethyl ether to methyl acetate and hydrogenation of methyl acetate to ethanol were successfully coupled to produce ethanol directly and efficiently.The main conclusions are as follows:1.The SiO2/Al2O3 ratio of mordenite(HMOR)is the important factor determining the catalytic performance of syngas to ethanol.The results show that HMOR-20(SiO2/Al2O3=20)has the highest reaction activity under the experimental conditions of 1.0-5.0 MPa,473-513 K and 3000 mL/(g h)space velocity.The conversion of CO is 6.50%and the selectivity of ethanol is 50.10%.When SiO2/Al2O3>20,the acid content of HMOR decreases with the increase of Si/Al,and correspondingly the reaction activity decrease gradually.When SiO2/Al2O3=10,HMOR is not conducive to the overall reaction because of the appearance of other zeolite crystalline phases.Although HMOR-20 has highest activity,the catalyst deactivates rapidly as the reaction proceeds.Coke deposition is the main cause of catalyst deactivation.Further research results show that selective regulation of Al atom placement in different channels and inhibition of HMOR growth along the C axis can improve the anti-coking performance of the catalyst,thereby improving the stability of the catalyst,but the stability still needs to be further improved.2.The metal ion modification can effectively improve the catalytic activity of the catalyst.The addition of Zn shortens the induction period of HMOR-20 reaction from 8 h to 2 h,the CO conversion rate increases to 7.40%,and the ethanol selectivity reaches 69.40%.However,Zn-HMOR-20 was still rapidly deactivated.After 12 h of continuous reaction,the CO conversion rate decreased to 5.68%,and the selectivity of ethanol decreased to 30.0%.Pyridine modification can effectively improve the stability of Zn-HMOR-20.At 200 h of continuous reaction,the catalytic activity of Py-Zn-HMOR-20 remained stable,the CO conversion rate was more than 7.0%,and the ethanol selectivity was also maintained at~50%.Py-Zn-HMOR-20 has good stability even after high temperature heat treatment at 300 ℃.The characterization results show that pyridine can occupy the acidic sites of HMOR molecular sieves(especially in the 12-ring channel),thereby improving the anti-carbon deposition performance of the catalyst and effectively improving the stability of the catalyst.