Patent ID: 7261806

Claim:
A process to prepare a base oil starting from a slack wax containing feedstock by (a) contacting the slack wax containing feedstock in the presence of hydrogen and under process conditions that include an operating temperature in the range of from 290° C. to 370° C. and a total pressure in the range of from 20 bar to 100 bar with a sulphided hydrodesulphurisation catalyst comprising nickel and tungsten on an acid amorphous silica-alumina carrier; and yielding an effluent, wherein in the preparation of the sulphided hydrodesulphurisation catalyst nickel and tungsten are deposited onto the acid amorphous silica-alumina carrier by means of impregnation using a chelating agent, and wherein the acid amorphous silica-alumina carrier has an n-heptane cracking test value in the range of from 310° C. to 360° C., wherein the n-heptane cracking test value is obtained by measuring the temperature at which 40 wt % of n-heptane is converted when contacted, under standard test conditions, with a catalyst consisting of said carrier and 0.4 wt % platinum, and wherein the sulphided hydrodesulphurisation catalyst has a hydrodesulphurisation activity greater than 30%, wherein the hydrodesulphurisation activity is expressed as the yield in weight percentage of C 4 -hydrocarbon cracking products when thiophene is contacted with the catalyst under standard hydrodesulphurisation conditions, wherein the standard hydrodesulphurisation conditions consist of contacting a hydrogen-thiophene mixture with 200 mg of a 30-80 mesh catalyst at 1 bar and 350° C., wherein the hydrogen rate is 54 ml/min and the thiophene concentration is 6 vol % in the mixture, and wherein the total pore volume of the sulphided hydrodesulphurisation catalyst is above 0.4 ml/g; and (b) performing a pour point reducing step on the effluent of step (a) to obtain the base oil, wherein the base oil has a content of polyaromatic compounds of less than 10 mmol/100 grams.