SAPO-34 molecular sieves as the catalysts were widely used for the process of methanol to olefin(MTO). The micropores of SAPO-34 molecular sieves only allow small molecules to diffuse in and out of the pore channels,and limit the diffusion of reactant molecules in pores of the catalyst crystal structure,which increases mass transfer resistance and prevents the reactant from reaching the active sites. The catalysts activities are decreased. In addition,the resultants are not easy to come out from the microporous structure,resulting in coke form due to excessive reaction. Using polyethylene glycol(PEG) as the mesopore-generating agent and triethylamine (TEA ) as the template,multi-porous SAPO-34 molecular sieves were obtained via hydra-thermal sythesis. Under the condition of n(Si):n(Al)=0. 20, n(PEG):n(Al)=0. 20,n(TEA):n(Al)=1. 5 and crystallization time 48 h,the as-prepared 0. 20P48-SAPO molecular sieve possessed better physicochemical properties. Compared with SAPO-34 molecular sieve,the specific surface area and pore size of 0. 20P48-SAPO molecular sieve were greatly enhanced. The increase of surface active site amounts was helpful to improve the catalytic activity. The best catalyst 0. 20P48-SAPO was evaluated in a fixed bed reactor. The results showed that the selectivity to proplene of 42% and methanol conversion of 91% were achieved. The catalyst possessed good stability and could be regenerated. The activity of the regeneration catalyst was comparable to that of fresh catalyst. The selectivity to proplene of 43% and methanol conversion of 90% were attained.%SAPO系列分子筛广泛应用于甲醇制烯烃(MTO)过程,SAPO分子筛的微孔结构仅允许小分子物质进出孔道,限制了反应物在催化剂晶体结构孔道中的扩散,增加了反应物扩散到活性位点的阻力,降低催化剂活性.此外,生成物不易从微孔结构扩散出来,导致过度反应生成积炭.采用聚乙二醇(PEG)作为导向剂,三乙胺(TEA)为模板剂,制备多级孔结构分子筛,在n(Si):n(Al)=0.20、介孔导向剂加入量n(PEG):n(Al)=0.20、模板剂加入量n(TEA):n(Al)=1.5和晶化时间为48 h条件下制备的分子筛0.20 P48-SAPO具有良好的物化性质,比表面积和孔径比单一孔结构SAPO-34分子筛大幅提升,表面活性位点数量增加,有利于提高催化活性.微型固定床反应器评价结果表明,甲醇转化率为91%,丙烯选择性为42%;催化剂热稳定性良好,可以进行再生,再生后活性与新鲜催化剂相当,甲醇转化率为90%,丙烯选择性为43%.
展开▼
