Study On Hydrodewaxing Catalysts Of Lubricating Oils

This paper sdudied on the preparation of the hydrodewaxing catalyst and its modidication with the extruding and impregnation method. With hydrocracking tail oil as the feedstock, the catalytic effect of several catalysts were evaluated on the fixed bed reactor and the process conditions were also investigated.Study of the preparation of the catalyst showed that the amount of nitric acid solution had significant impact on the mouldling of the catalyst and the smoonth level of the catalyst surface. The nitric acid solution in the concentration range of 1.5-6% had little effect on the crystal structure of ZSM-5, but the 6% nitric acid solution might weakly dissolve the moleculer sieve. The calcination temperature and calcination time had significant effect on the mechanical strength of the catalyst, but they didn’t have much influence on the specific suface area and pore volume. Higher calcination temperature and longer calcination time could increase the mesopore size.XRD pattern indicated that elements loaded on the ZSM-5/Al₂O₃ support was highly dispersed. BET results showed that catalyst supports loaded with small amounts of modification elements（below 5%） possessed smaller specific surface area and pore volume, but it couldn’t change much. However, the pore structure data of catalyst modified by Mg decreased obviously. The results of the mechanical strength showed that catalyst modified by Ca and Mg possessed larger mechanical strength than other catalysts.Results of the fixed bed reaction showed that the cracking activity of the hydrodewaxing catalyst could be decreased by increasing the loading amount of Ni, adopting ZSM-5 with larger Si/Al ratio, reducing the proportion of ZSM-5 in the catalyst and modifying the catalyst with Ca and Mg. The craking activity could be increased with the aluminum hydroxide dry glue as the binder in the prepared catalyst or modifying the catalyst with P and Zn. Lube oil produced by different catalyst possessed rather different condensation point under low reaction temperature. However, when the reaction temperature increased to a certain value, lube oils produced by different catalysts（except the catalyst modified by Mg） could all reach a condensation point of-40℃ at which point the yield of the lube oil was relatively low. While the condensation point and yield of the lube oil produced with catalyst modified by Mg didn’t change much with the increase of temperature which indicated that catalyst modified by Mg possessed stable catalytic property.Research of the process condition showed that the reaction temperature and space velocity had great influence on the yield, the condensation point and the viscosity index of the lube oil. These properties descreased as the temperature increased and become stable when the reaction temperature reached to a certain value. These properties increased with the increase of the space velocity. While the hydrogen/oil ratio didn’t have much influence on these properties.Two catalysts with good catalytic effect were selected out in this paper: The 1%Ca modified catalyst could reach a condensation point of-17℃, yield of 72% and viscosity index of 83 at reaction temperature of 310℃, space velocity of 3.0 h-1, hydrogenation/oil ratio of500. The 1%Mg modified catalyst could reach a condensation point of-15℃, yield of 73.5% and viscosity index of 87 at temperature of 320℃, space velocity of 3.0 h-1, hydrogenation/oil ratio of 500.