Preparation And Catalytic Performance Of Carbon Aerogels Supported Copper Catalysts For The Dimethyl Carbonate Synthesis

The catalytic activity,selectivity and stability are three important parameters of catalyst performance.Therefore,the development of catalysts with high activity,high selectivity and high stability has always been the key issue in the field of catalysis.Catalyst support is one of the important factors influencing the catalytic performance,the dispersion,size and chemical structure of the active sites can be improved by changing the type of catalyst support and modifying its physical and chemical properties,so as to improve the catalytic performance.Carbon material as catalyst support has the characteristics of surface chemical properties and texture properties and easily controlled.Therefore,it has potential applications in the field of catalysis.In this paper,activated carbon aerogels?ACAs?supported Cu nanoparticles catalysts?Cu/ACAs?were prepared by the sol-gel method,chemical activation of potassium hydroxide?KOH?,and wet impregnation for the DMC synthesis by vapor phase oxidative carbonylation of methanol.The influence of the molar ratio of resorcinol to anhydrous sodium carbonate?R/C?and KOH activation on the physical and chemical properties of carbon aerogels have been investigated.In the meanwhile,the relationship between catalyst support of ACAs and Cu species in the presence of oxygen-containing groups?OCGs?was further analyzed by the density functional theory?DFT?.The specific contents summarized as the following:1.The textural properties of CAs can be controlled by varying the R/C molar ratio.When R/C molar ratio increased from 100 to 900,the pore size of CAs increased gradually,meanwhile,there are more and more mesopores formed within CAs.CAs with the R/C molar ratio of 500 was chosen as catalyst support because of its corresponding catalyst performs the best catalytic activity,and the DMC space time yield?STYDM C?was 226.8 mg/?g·h?,attributed to the pore structure is beneficial to the transport of the molecules during the reaction progress.2.KOH activation effectively improve the texture properties of CAs.During the activation process,the specific surface area and pore volume of ACAs increased gradually with the increasing KOH/CAs mass ratio from 0 to 4.However,both of the two parameters decreased when the KOH/CAs mass ratio up to 6,mainly due to excessive KOH leading to the collapse of the ACAs structure.3.Chemical activation of KOH not only makes remarkable influence on the textural characteristics of ACAs,but also increases the amount of the OCGs on the ACAs surface,including C=O,COOH,and OH.The higher KOH/CAs mass ratio is,the more surface OCGs will be created,which lead to the interaction between the interaction between the carbon support and the copper species.DFT calculation results manifest that enrichment in C=O group on the surface of the catalyst support makes the binding energy between the catalyst support and the copper nanoparticles be as high as 900.9 kJ mol^-1.The strong interaction promotes the formation of small particle size of copper nanoparticles,improve the activity of copper surface area,thus improving the catalytic activity.4.After the optimization of preparation conditions,the optimal catalytic performance of Cu/ACAs was obtained when KOH/CAs mass ratio is 4.Under the condition of T = 120 °C,P = 1.5 MPa,CH3 OH flow rate = 0.056 mL·min-1,n?O₂?: n?CO?= 1:11,gas hourly space velocity?GHSV?= 4600 h^-1,methanol conversion?CCH3OH?and STYDM C are 2.5% and 338.7 mg/?g·h?,respectively.