The Development Of Catalyst For The Skeletal Isomerization Of N-butene

Isobutylene is a kind of crucial chemical raw material,which has a wide application prospect in the chemical,energy and materials industries.The skeletal isomerization process of n-butene has the advantages of sufficient source of raw materials,low cost,simple process flowsheet and no environmental pollution,etc.,which can be used to cope with the shortage of isobutylene resources.Therefore,this process has broad prospects for development.In this paper,the SAPO-11 kind of molecular sieve catalyst was studed in detail,and the influences of the raw materials,crystallization conditions and the molar ratio of raw materials on the synthesis of SAPO-11 kind of molecular sieve were investigated.The research results demostrated that the acidic silica sol could be used as the silica source,the pseudo-boehmite could be used as aluminum source,the orthophosphoric acid could be used as the phosphorus source,di-n-propylamine and diisopropylamine could be used as template agent,the SAPO-11 kind of molecular sieve with relatively pure and no impurity phase was synthesized under the conditions of 200?crystallization temperature,24 hours crystallization time with the molar ratio of the raw material for Si O₂:Al₂O₃:P₂O₅:M:H₂O=0.2:1.0:1.0:0.9:50.0.The relative crystallinity of the synthesized SAPO-11 kind of molecular sieve was high to 125.05%.The characterization results showed that the particles of synthesized SAPO-11 kind of molecular sieve were cuboid with uniform size,but few heterocrystals and amorphous materials.The acidity of the synthesized SAPO-11 kind of molecular sieve was less than that of the commercial ZSM-35 kind of molecular sieve,but slightly stronger than that of the commercial SAPO-11 kind of molecular sieve.After extrusion molding,the synthesized SAPO-11 kind of molecular sieve was used to catalyze the skeletal isomerization reaction of n-butene.The experimental result illustrated that the synthesized SAPO-11 kind of molecular sieve exhibited the good catalytic performance under the conditions of 0.1 MPa,400°C and 8 h^-1.Compared with the commercial ZSM-35 kind of molecular sieve,the synthesized SAPO-11 kind of molecular sieve had higher selectivity of isobutylene and activity stability,and there were no obvious"climbing period"for the selectivity and yield of isobutylene.The acidity of the synthesized SAPO-11 kind of molecular sieve was slightly stronger than that of the commercial SAPO-11 kind of molecular sieve.Therefore,the conversion of n-butene and the yield of isobutylene of the synthesized SAPO-11 kind of molecular sieve were slightly higher than the commercial SAPO-11kind of molecular sieve.For the synthesized SAPO-11 kind of molecular sieve,the n-butene conversion,the selectivity and yield of isobutylene was 41.7%,88.1%and36.7%,respectively after 5 hours of reaction.The effect of binder on the catalytic performance of the synthesized SAPO-11 kind of molecular sieve was investigated.The results demonstrated that the addition of the SB powder into the synthesized SAPO-11 kind of molecular sieve woud lead to a slight reduction in the selectivity of isobutylene,but could increase the conversion of n-butene and the yield of isobutylene.Therefore,the SB powder could be used as a binder for the extrusion molding of SAPO-11 kind of molecular sieve,and the extrusion molding of SAPO-11 kind of molecular sieve catalyst could be used into catalysis the skeletal isomerization of n-butene.