Pt/Hβ临氢异构化催化剂及其还原条件研究

STUDY ON Pt/Hβ HYDROISOMERIZATION CATALYST AND ITS REDUCTION CONDITIONS

以不同硅铝比的Hβ分子筛为载体负载Pt制备Pt/Hβ异构化催化剂。采用低温N_2吸附-脱附和XRD,NH_3-TPD,Py-IR,TEM等方法对催化剂进行表征,在10mL固定床微型反应器(微反)上对不同硅铝比Hβ分子筛制备的Pt/Hβ催化剂和不同还原条件下催化剂的临氢异构化性能进行了评价。结果表明:Hβ分子筛硅铝比对催化剂酸性质和孔结构性质影响明显,随着硅铝比增大,总酸量、中强酸量和B酸量减少,比表面积和孔体积减小,正己烷的转化率增大而异构化率和二甲基丁烷选择性减小;当硅铝比为25时,Pt/Hβ催化剂的异构化性能最好。还原温度和还原压力主要影响催化剂上Pt的粒径大小及其分布,在350℃和0.75MPa条件下还原后,Pt晶粒的平均粒径最小且分布均匀,有利于Pt/Hβ异构化催化剂的活性金属和酸性的匹配,正己烷转化率为81.16%,异构化率为82.89%,二甲基丁烷选择性为25.58%。

The Pt/Hβ isomerization catalysts were prepared by using Hβzeolite with different silica-alumina ratio as the carrier and loaded with Pt.The Pt/Hβ catalysts were characterized by N2adsorption-desorption,XRD,NH3-TPD,Py-IR and TEM.And the isomerization performance of the prepared catalysts was evaluated in a10mL fixed-bed micro-reactor.The results showed that the silica-alumina ratio of Hβzeolite has a significant effect on the acidity and pore structure of the catalyst.With the increase of silica-alumina ratio,while the total acid,medium strong acid and Br nsted acid sites,and the specific surface area and pore volume decrease,which improve the conversion rate of n-hexane and inhibit the isomerization and dimethylbutane selectivity.ThePt/Hβcatalyst with silica-alumina ratio of 25 has the best isomerization performance.Reduction temperature and pressure mainly affects the size and distribution of Pt on the catalyst.At a reduction temperature of350℃and a pressure of 0.75 MPa,the average particle size of Pt is the smallest and uniformly distributed,which is beneficial to improve the metallicity and acid matching degree of the catalysts,and the best isomerization results is obtained with the n-hexane conversion rate of 81.16%,isomerization rate of 82.89%,dimethylbutane selectivity of 25.58%.