摘要
以三乙胺-四乙基氢氧化铵为复合模板剂,合成了不同硅含量的SAPO-34分子筛,并采用XRD、NH3-TPD、以及29Si MASNMR等方法对其进行了表征,最后考察了不同硅含量SAPO-34分子筛催化转化氯甲烷制取乙烯、丙烯的反应性能。结果表明：硅铝比在0.10-0.80时,均能合成规整的SAPO-34立方晶粒;硅铝比低于0.05或高于1.00时,易伴随形成片状和无定形晶相。当硅铝比为0.6时,SAPO-34的结晶度最大,微孔比表面积为588m^2/g,微孔体积为0.267cm^3/g。硅铝比从0.05到0.60逐渐增大时,SAPO-34酸强度和酸数目明显增多,继续增大硅铝比,酸强度增强,弱酸数目减少。在T=425℃、氯甲烷WHSV=2.73h^-1时,对所合成SAPO-34分子筛催化氯甲烷的反应性能进行了评价,随硅铝比增大,SAPO-34的酸性增强,氯甲烷的初始转化率逐渐升高,然而二次反应加剧致使乙烯丙烯选择性略有下降。
SAPO-34 molecular sieves with different Si contents were synthesized and used as catalysts for conversion of chloromethane to light olefins. The influences of different Si amounts on crystalline structures,morphology features,textural properties and acidity of SAPO-34 samples were characterized with XRD,NH3-TPD,and29Si MASNMR. Uniform SAPO-34 cubic crystals could be formed when ratio of Si/Al was in the range of 0.10—0.80. When ratio of Si/Al was 0.6,relative crystallinity of SAPO-34 sample was the highest,microporous specific surface area was 588m^2/g,and microporous volume was 0.267cm^3/g. NH3-TPD results showed that when ratio of Si/Al was gradually increasing from 0.05 to 0.60,acid strength and acid amount were obviously enhanced,and acid strength was increasd with decreasing weak acid amounts when ratios of Si/Al was increased from 0.60 to 1.0. When conversion of chloromethane to light olefins was performed over SAPO-34 catalysts at 425℃,activity and stability of SAPO-34 catalysts were gradually improved with increasing ratio of Si/Al while selectivities of propene and ethene were slightly decreasing due to aggravated secondary reactions.
出处
《化工进展》
EI
CAS
CSCD
北大核心
2015年第2期413-418,共6页
Chemical Industry and Engineering Progress
