Research Of Octane Isomerization Over Tungsten Based Catalysts

The demand for the petroleum is increasing with the continuous high-speed development of Chinese economy. Consumption of gasoline is increasing over the speed of 2% every year, More and more severe emission pollutions are caused by this.As one of the main routes to produce high-octane gasoline blending components in the crude oil refining industry, alkanes isomerization has drawn much attention throughout the world because it can greatly improve the gasoline quality. For alkanes isomerization, one of the key issues is to develop catalysts with higher activity and higher stability, which has been widely pursued due to its importance both in academic research and in industrial utilization.The objective of our work is to investigate the isomerization of n-octane over tungsten oxide based catalysts. The effects of the preparation and reaction conditions on the conversion and isomerization selectivity of n-octane were studied carefully. The main contents of the thesis were discussed as follows:(1) It was found that the WOx catalyst obtained by H2 reduction at 525℃in a period of 6 hours exhibited a better catalytic activity with the reaction temperature 300℃, WHSV 1.759 h-1. The conversion of n-octane reached 60.21%. The physicochemical properties of catalysts were measured by XRD and BET technique, and the characterized result showed that the active phase of WOx catalyst for n-octane hydroisomerization could be considered WO2. This catalytic behavior was interpreted using the participation of a bifunctional mechanismone on the WO2. By reduction the surface area obviously increased. The catalyst showed the mesoporous character(2) It was indicated that catalytic activity of WOx catalyst for n-octane isomerization was markedly enhanced and the reduction temperature was reduced by incorporation of Ni in the catalyst. It was found that an overall conversion of nearly 62.15% could be achieved on Ni-WOx catalysts, when the calcination temperature was 800℃, the Ni content was 2%, the reduction temperature was 500℃, the reaction temperature was 275℃. The conversion of n-octane on 2%Ni-WOx catalysts was much high than on the WOx catalyst. the selectivity of n-octane on Ni-WOx catalysts was lower than on the WOx catalyst. Characterized studies showed that the active phase of 2%Ni-WOx catalyst for n-octane hydroisomerization could be considered WO2. This catalytic behavior was interpreted using the participation of mechanism: a bifunctional one on the WO2 phase. Incorporation of Al,Zn,Cr,Cu,Co,Mo,Cd to the catalysts did not enhanced the catalytic activity for n-octane isomerization.(3) n-octane isomerization on the WOx/SiO2 catalyst was studied. The WOx/SiO2 catalyst shows lower catalytic activity than bulk WOx catalyst, which can be explained by the interaction between the support and WO3 in WOx/SiO2 catalyst, the conversion of n-octane on the WOx/SiO2 catalyst was only about 3%.