Sapo-31 Molecular Sieve Synthesis And Catalytic Organic Alkane Hydroisomerization Reaction

In this paper, SAPO-31 molecular sieves with different acid properties were synthesized by hydrothermal method. The acid and structure properties were inspected by means of XRD, FT-IR, SEM, N2 absorption, NH3-TPD,29Si NMR. The effect of reaction temperature,pressure and metal loading on hydroisomerization of n-decane was investigated to optimize the technological conditions. The effect of the silica content, the type of template agent and the distribution of template ratio between DPA and DBA on the influence of structure, acid properties and catalytic performance of SAPO-31 molecular sieve were also investigated. Selectivity to isomerized and cracked reaction products was influenced by both the acid properties of Pd-SAPO-31 and Pd loading in the catalysts.The effect of structure, morphology and acid property was influenced by gel composition.The template agent and silica source were dipropylamine and tetraethylorthosilicate, changing the H2O content could realize the transformation of SAPO-31 into SAPO-41.The optimal catalytic performance of n-decane hydroisomeration on SAPO-31 catalyst using dibutylamine as a template. Under the optimun reaction condition,that is,reaction temperature is 340℃, pressure is 2 MPa, WHSV=2.5 h-1, H2 velocity is 120 ml/min, the conversion of n-decane and the seletivity for decane isomers are 85.28% and 78.12%, for 3 h.By changing the ratio of DPA and DBA, the acidic and catalytic properties of SAPO-31 molecular sieve can be modulated. SAPO-31 molecular sieve(DPA/DBA ratio=1:1, SiO2/Al2O3=0.5) showed high catalytic activity and high selectivity of decane isomers.