Preparation Of Mesoporous MOR Zeolites And The Study On Their Carbonylation Performance

The carbonylation reaction is an effective means to prepare oxygenates and achieve the growth of low carbon compound chains.In recent years,the research of ethanol synthesis through dimethyl ether heterogeneous carbonylation-reduction by molecular sieves has attracted much attention and affirmation.The method has obvious advantages over the conventional homogeneous carbonylation reaction which based on noble metal-halogen additives in many aspects such as catalyst,reactor and product separation.Numerous studies have shown that mordenite(MOR)zeolites have high catalytic activity and target product selectivity for dimethyl ether carbonylation.In order to solve the problem of fast deactivation and low mass transfer efficiency of existing MOR zeolites,this paper started from the preparation and post-treatment modification of MOR zeolites to prepare high specific surface area MOR zeolites with mesoporous structure.The carbonylation performance of the catalyst was evaluated by a miniature fixed bed reactor.The structure of the MOR molecular sieve catalyst was characterized by XRD,BET and SEM.The acid center of MOR was characterized by NH3-TPD,and the carbon deposition of deactivated catalyst was studied by TPO and TG.By correlating the carbonylation reaction performance with the characterization data,the following results were obtained:Firstly,a series of MOR zeolites were prepared by alkali treatment.The results have shown that the number of acid centers in the alkali-treated MOR zeolites is reduced,the specific surface area and the mesoporous pore volume are increased,which is beneficial to mass transfer and reduction of carbon deposition.The stability and catalytic activity of the carbonylation reaction are improved.Secondly,a series of MOR zeolites were synthesized using carbon microspheres as hard template.The experimental results have shown that the series A MOR zeolites have better carbonylation performance.Compared with the reference sample,the catalytic activity of series A MOR zeolites is significantly improved,and the stability is increased.Finally,this paper explored the regeneration method of deactivated MOR zeolites,and the zeolites regenerated by “stepwise burning off carbon method” can basically restore to the activity of fresh catalyst.Repeatedly “reaction-regeneration” studies have shown that as the number of reaction increases,the reaction induction period is prolonged,the peak activity of the catalyst is slightly decreased,and the stability is gradually increased.