Investigation Of Isomerization Of N-Heptane Over Supported HPAs Catalysts

Isomerization of alkane is a very important process in petroleum refining industry on enhancing octane number of gasoline,improving qualitity of oil products and decreasing environment pollution.In the recent years,this process has faced great challenge with the increasing demand for middle distillates and the more stringent environmental protection.Therefore,exploiting the novel hydroconversion catalyst with open pore structure is of great significance in petroleum industry.Mesoporous molecular sieves represented by MCM-41 with high surface area,mild acidity and adjustable pore size in the range of 2-10 nm, has captured the attention of many researchers in the field of catalysts,supports and adsorbents,especially in the field of large molecular reactions.Heteropolyacid used as solid acid catalyst,which is higher than usual inorganic acid in strength.Solid heteropolyacid has the features of homogeneous catalytic reaction with its special structure of hexagonal cages and its certain vacuity among heteropolyacid anions,which make smaller polar molecules enter into heteropolyacid body ainai,so as to form a false liquid phase.The existence of heteropolyacid catalytic action with bulk types and surface types make the reaction occurred on not only the surface but also the whole internal of the catalysts.Therefore,this kind of catalyst usually shows higher catalytic activity and selectivity.Though heteropolyacid has excellently catalytic performance,it is difficult to prepare the catalyst because of the small size(10nm),and it is also difficult to operate with the higher resistance.We usually load the heteropolyacid on the surface of support in order to increase the surface area in practical application.Mesoporous molecular sieves MCM-41 was prepared using water-heat synthesis in this paper, the catalyst was loaded with Ni and SiW12 by impregnation. And it was rearched on mesoporous molecular catalyst Ni-SiW12/MCM-41 and the effects of different preparation conditions,reduction conditions and reaction conditions on the conversion and isomerization selectivity of n-heptane with a fixed bed continuous flow micro reactor. The samples were characterized using XRD,BET surface area and Py-IR Profiles.The results showed that the very high activity and selectivity can be achieved when calcine temperature is 400℃, H2 reduction temperature is 400℃, flow rate of H2 is 40mL/min, content of Ni and SiW12 is 4% and 30%,and reaction temperature is 300℃. Conversion of n-heptane and isomerization selectivity to i-heptane can reach 18.5% and 74%.