Process for the preparation of a lubricating base oil

A process for the preparation of a lubricating base oil product having a pour point below -20.degree. C. and a viscosity index above 130 which comprises catalytically dewaxing in the presence of hydrogen and a dewaxing catalyst comprising a composite crystalline aluminum silicate obtained by maintaining an aqueous starting mixture comprising one or more silicon compounds, one or more aluminum compounds, one or more compounds of metals group 1a of the Periodic Table of Elements and an organic nitrogen compound at an elevated temperature for a period of time until a composite aluminum silicate has formed and subsequently separating the crystalline aluminum silicate from the mother liquor, wherein the various compounds are present in the starting mixture within the following molar ratios:

• RN:R.sub.4 NY=6-3000
• SiO.sub.2 :R.sub.4 NY=200-10,000
• SiO.sub.2 :Al.sub.2 O.sub.3 =60-250
• SiO.sub.2 :
• compounds of metals of group 1a<10, and
• H.sub.2 O:SiO.sub.2 =5-65,
• wherein RN represents a pyridine and R.sub.4 NY represents an organic quaternary ammonium compound, at conditions comprising a temperature of 200.degree. to 450.degree. C. and at a space velocity of 0.1 to 5.0 kg/l.catalyst.h, a hydrogen (partial) pressure of 10 to 200 bar and a hydrogen/feedstock ratio of 100 to 2000 Nl/kg, a hydrocrackate comprising a slack wax mineral oil fraction containing 50 to 95% wt wax and having a kinematic viscosity at 100.degree. C. of, at the greatest, 10 mm.sup.2 /s, and recovering said lubricating base oil product having said pour point below -20.degree. C. and said viscosity index above 130.