Sapo - 34 On The Study Of Methanol To Olefins Reaction

Methanol-to-Olefins(MTO), has centralized the world’s attention for its potentiality in taking the place of petroleum to produce light olefins. The key issue for the MTO reaction is to develop a new catalyst with excellent catalytic performance. SAPO-34molecular sieve has turned out to be a superiorcatalyst for the MTO reaction, due to its high activity and high selectivity to olefins. Nevertheless, SAPO-34is known to suffer rapid deactivation and long induction time. In this thesis, we summarized the recent researches of SAPO-34are focused on the optimizations of the reaction conditions, the catalyst’s regeneration, as well as the elementary modifications, intending to bring about a higher selectivity, a longer life span, a shorter induction time.1. Explore appropriate MTO reaction conditions over SAPO-34MTO reaction over SAPO-34with different temperature, space velocity, and concentration of the methanol was studied in a fixed bed reactor. It is shown that the optimized reaction conditions are T=420℃; LHSV=1.25h-1; Ptotal=1atm. MeOH:H2O=1:5(w:w). Under the above reaction conditions, the conversion of methanol is100%, while olefins selectivity is up to90%, life time about9.5hours, while no obvious induction period is observed.2. In situ regeneration of deactivated SAPO-34In situ decoke with different temperature, air space velocity and water vapor space velocity were studied.2g complete deactivated SAPO-34were treated with two methods:(1)460or480℃, saturated water vapor containing air80ml/min (stream space velocity about0.1h-1) for8hours and (2)420℃, air80ml/min, water (space velocity about5h-1) for8hours. Result of NH3-TPD、XRD and TGA, exhibit that almost all the coke was elimined and catalytic activity was regenerated. 3. Preparation, characterization and catalytic performance of supported X/SAPO-34(X=P and metal) catalysts.Elements of P、Mn、Co、Ni、Zn and Ga were selected as promoters to modify SAPO-34catalyst for MTO reaction. In the study, the suitable amount of modification is0.1%,0.1%Co、0.08%Mn and0.08%Co dual metal modification exhibit good results, extended the catalytic life for four hours, improve olefins selectivity to82.6%while reaction0.5hours, and shorten the induction period.