The Preparation Of The New Isomerization Catalysts And Their Evaluation In Hydroisomerization Of Long-chain Paraffins

In recent years, to improve the octane number of gasoline, People have done a lot of research on small alkanes such as C4-C7. However, research on long-chain alkanes which numbers of carbon atom higher than10is very important to improve the cetane number of diesel fuel and the viscosity-temperature of lubricating oil. Hydroisomerization of long-chain alkanes is a bifunctional process requiring metal as well as acid sites. ZSM-22, L/MCM-41, L and SAPO-11was selected as catalyst supports to research the influence on the hydroisomerization results of different support acidity. Impregnation, ion exchange and precipitation was applied to load Pt with SAPO-11molecular sieve as the catalyst support, the loaded amount of Pt were0.4%wt,0.5%wt,0.6%wt and0.7%wt. Catalysts were prepared in different preparation conditions such as calcination temperature, calcination time and reduction temperature, then tested in hydroisomerization process to research the influence on the results of the different catalysts. SEM, TEM, XRD and TPD were used to characterizatize the structure, acidity, morphology of catalysts.According to the results of the experimentation, due to its unique10-membered ring, one-dimensional channel, the suitable acid strength and acidity, Pt/SAPO-11show the best hydroisomerization performance.In this paper. we separately use impregnation, ion exchange and precipitation to prepare Pt/SAPO-11, then Pt/SAPO-11was tested in hydroisomerization precess of n-dodecane. The result show that the catalyst prepared by impregnation has the best hydroisomerization performance.The hydroisomerization results show that the optimum preparation conditions were the Pt loading amount0.4%wt, calcination temperature550℃, calcination time3h, reduction temperature400℃. The hydroisomerization of n-dodecane catalyzed by Pt/SAPO-11was studied, and tested the effects of reaction temperature, reaction pressure, WHSV and hydrogen hydrocarbon molar ratio on the hydroisomerization behavior. The optimal reaction conditions were:reaction temperature340℃, reaction pressure2MPa, WHSV1h-1, hydrogen hydrocarbon ratio of15. At above contions， the conversion of dodecane is89.79%, the selectivity of isomerization and monobranched paraffins is95.47%and73.63%, the yield of isomers is84.69%.The hydroisomerization of n-hexadecane catalyzed by Pt/SAPO-11was studied. The optimal reaction conditions were:reaction temperature360℃, reaction pressure1.5MPa, WHSV1h-1, hydrogen hydrocarbon ratio of15. At above contions, the conversion of n-hexadecane is92.70%, the selectivity of isomerization and monobranched paraffins is92.94%and49.95%, the yield of isomers is86.16%. According to the distribution of the products of n-hexadecane and n-dodecane hydroisomerization, we can deduce that the pore mouth and key-lock catalysis may be the best theory to explain the hydroisomerization of long-chain paraffins.