Study On Molecular Sieve Catalyst From Dimethyl Ether To Ethanol

In recent years,with the rapid development of social economy,the energy consumption mainly based on fossil resources has been increasing,which has brought about serious energy shortage and environmental pollution.Syngas is carbonylated with dimethyl ether,and then methyl acetate is hydrogenated to synthesize ethanol,which is a new technology for ethanol production.The key to realizing this technology is the development of dimethyl ether carbonylation catalyst and methyl acetate hydrogenation catalyst.In this paper,hydrothermal and sol-gel method were used to prepare molecular sieve catalysts for dimethyl ether carbonylation and methyl acetate hydrogenation,respectively.The effects of platinum-copper bimetals and soft templating agents on the structure of mordenite molecular sieve and dimethyl ether carbonylation performance,and the performance of silver-copper bimetal-supported all-silicon molecular sieve methyl acetate hydrogenation reaction were studied.The characterization of Ar adsorption,XRD,NH3-TPD,SEM,TPO,XPS,EDS mapping,HRTEM,GC-MS and nuclear magnetic resonance were carried out.The mordenite molecular sieve catalyst was prepared by hydrothermal synthesis method for dimethyl ether carbonylation reaction.The Cu additive was loaded by ion exchange method,and then the addition of Pt was loaded by dipping method.The effect of the addition of Pt and Cu bimetal on the carbonylation performance of mordenite dimethyl ether was studied.NH3-TPD results showed that the addition of Cu could introduce active sites of medium acids and effectively enhanced the interaction between the active components and the molecular sieve.HRTEM and EDS mapping results showed that the addition of Pt improved the dispersion of Cu on the catalyst surface,which made CuO easier to be reduced and enhanced the catalytic activity.DRIFTS and Py-IR results showed that the interaction of Pt and Cu increased the amount of Br(?)nsted acid of the 8-membered ring,thereby improving the catalytic activity.The H on the 12-membered ring of the molecular sieve was replaced by metal,and the amount of acid was reduced,thereby reducing carbon deposition.Comparing with other modified catalysts,the 1Pt/Cu-MOR catalyst with the addition amount of Pt and Cu is 1 wt%and 2 wt%showed the highest activity at 200?,1.0 MPa,2400 ml/(g·h)space velocity,and the conversion of dimethyl ether and selectivity to methyl acetate were 86.0%and 96.0%,respectively.The hierarchical porous mordenite molecular sieve catalyst was prepared by adding n-butylamine and polyacrylamide soft template agent in the hydrothermal synthesis process.The results of Ar low temperature adsorption and desorption showed that the addition of a suitable amount of soft template agent increased the specific surface area and pore size of the catalyst.NH3-TPD and Py-IR results showed that the addition of soft template agent increased the amount of strong acid and reduced the amount of acid in the 12-membered ring.HRTEM and SEM results showed that the addition of a suitable amount of soft template agent formed more mesopores,improved the diffusion of reactants and intermediate products,reduced carbon deposition and improved the stability of the catalyst.27Al MAS NMR and 29Si MAS NMR showed that the addition of soft template induced the molecular sieve to form more framework aluminum,which increased the active acid site of the catalyst and enhancesd the catalytic activity.The HMS all-silicon molecular sieve was prepared by the sol-gel method,and the bimetallic catalyst supported by Ag and Cu was prepared by the co-precipitation method for methyl acetate hydrogenation reaction.TEM and EDS mapping results showed that the synergy between Ag and Cu bimetallic improved the dispersion of metal particles on the catalyst surface,increased the metal active site,and formd copper-silver bimetallic nanoparticles,making CuO difficult to be reduced to Cu.The more Cu+ speices improved the adsorption performance of the catalyst for methyl acetate and methoxy groups,and improved the catalyst's reactivity.When Cu and Ag were added at 20 wt%and 1 wt%,respectively,CulAg/HMS catalyst had the highest hydrogenation activity of methyl acetate,at 250?,3.0 MPa,H2/MA=20(mol/mol),liquid hourly space velocity of 1.6 h-1,and the conversion rate of methyl acetate and ethanol selectivity were 94.4%and 88.5%,respectively.The mordenite molecular sieve catalyst treated with sodium hydroxide alkali solution was used in the dimethyl ether carbonylation reaction.The results of Ar low temperature adsorption and desorption indicated that the treatment of alkali solution with appropriate concentration increased the specific surface area of catalyst and the pore volume of mesoporous.The results of NH3-TPD and DRIFTS indicated that the alkali-treated mordenite molecular sieve had more strong acid,increased the amount of Bronsted acid,and improved the catalytic activity of the catalyst.TEM results showed that the catalysts treated with alkaline solution of appropriate concentration had more mesopores.In the hydrothermal synthesis process,triethylamine and tetraethylammonium hydroxide were added to prepare a nano-MORdenite molecular sieve catalyst,which was used for the dimethyl ether carbonylation reaction.The results of Ar low temperature adsorption and desorption showed that the addition of double template agent increased the specific surface area of the catalyst.NH3-TPD results showed that the addition of double template agent increased the strong acid active site of the catalyst and increased the activity of the catalyst.TEM and SEM results showed that the addition of dual templates reduced the catalyst particle size,improved the diffusion of reactants and intermediate products,and improved the stability of the catalyst.