| 摘要 |
LUBRICANT PRODUCTION PROCESS A process for producing lubricant oils of low pour point and high viscosity index by partial dewaxing of a lubricant base stock by isomerization dewaxing followed by a selective dewaxing step. The isomerization dewaxing step is carried out using a large pore, high silica zeolite dewaxing catalyst such as high silica .gamma. or zeolite beta which isomerizes the waxy components of the base stock to less waxy branch chain isoparaffins. The severity is controlled to effect only a partial removal of the waxy components. Further removal of the waxy components is effected during a subsequent dewaxing step which selectively removes of the more waxy n-paraffin components, leaving the branched chain isoparaffins which contribute to a high VI in the product. The selective dewaxing step may be either a solvent, e.g., MEK dewaxing operation or a catalytic dewaxing, preferably using a highly shape selective zeolite such as ZSM-22 or ZSM-23. Isomerization dewaxing may be controlled to effect a net increase in the content of isoparaffins and because of the selective nature of the solvent dewaxing step, this increased isoparaffins concentration may be retained, producing a product of high VI. The pour point of the feedstock is preferably reduced by isomerization dewaxing to a value which is no lower than 6.degree.C and preferably no lower than 12.degree.C, above the target pour point for the products. Generally, this will entail a reduction of at least 6.degree.C and preferably at least 12.degree.C in the pour point of the feed. |
