Study On The Isomerization Of N-Octane On ZSM-22 Catalyst

Hydroisomerization of n-alkanes to their branched isomers is one of the important processes in the modern petroleum refining industry that has been widely applied in producing high-octane gasoline. In particular, with the ever-increasing demand for high-octane gasoline due to the rapid development of the automobile industry, searching for catalysts to isomerize C5-C8 n-alkanes of low octane rating into multi-branched isomers of high octane rating has been the subject of many investigations around the world.As an acidic carrier of bifunctional catalysts, ZSM-22 with a one-dimensional 10-membered-ring channel system of 0.44 nm 0.55 nm has shown its advantages in n-alkane isomerization due to its distinct pore structure and acidity. The study is aiming at searching for optimum condition for catalytic performance of isomerization of n-octane on ZSM-22 catalysts, including catalyst preparation and reaction conditions.The main contents of this thesis are as follows:1. Isomerization of n-octane on Pt/ZSM-22 catalyst was maintained at 40.32% yield of isomerization products under the conditions of 583 K,3.0 MPa, volumetric H2/n-octane ratio 300, and weight hour space velocity (WHSV) 0.7 h-1. Further, effects of reduction time and reaction pressure for catalyst were investigated, it was found that reduction time 8h, reaction pressure 3 MPa were optimal conditions.2. Isomerization of n-octane on Pt-P/ZSM-22 catalyst was maintained at 53.82% yield of isomerization products under the conditions of 593 K,3.0 MPa, volumetric H/2/n-octane ratio 200, and weight hour space velocity (WHSV) 1.05 h-1. Further, the stability of this catalyst was investigated, it has a good stability in 110h.3. Effects of different modification methods for catalysts were investigated by two series of ZSM-22 catalysts, it was found that the impact of the times of ammonium exchanged, the sequence of water vapor passivation and phosphorus modification treatment on Pt-P/ZSM-22 catalyst is biggest. The catalysts were compared by using three evaluation methods, it was found that different evaluation methods get the different conclusions.