TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process Details: The hydro-dehydrogenating element is an element from groups VIB or VIII. The group VIB element is more preferably Mo and/or W, and the group VIII element is a noble metal, more preferably Pt and/or Pd. The treated charges have at least 50 vol/% of compounds boiling above 340 degrees C. The operating conditions for a hydrofinishing stage, following the catalytic deparaffination stage, are 200-450 degrees C, 0.1-25 MPa and VVH of 0.05-30 hour-1. The charge is submitted to a pre-treatment of hydroisomerization-hydroconversion and the effluent is conveyed to the deparaffination stage. The hydro-isomerization is preceded by a hydrorefining stage, the latter being followed by an intermediate separation. The effluent from the catalytic hydrodeparaffination is partly conveyed to a hydrofinishing catalyst. The preferred process comprises the stages(a) the charge to be treated is separated (D1) into a light fraction 3 of boiling point less than 380 degrees C and a residual fraction 4;(b) the light fraction, optionally hydrotreated (HDT), is submitted to hydroisomerization (HISM);(c) the heavy fraction is submitted to hydrocracking (HCK) in the presence of H2 then submitted to distillation (D2) to produce a light fraction (13) and heavy fraction (10);(d) the mixture form hydroisomerization is fractionated (D3) along with (13) to obtain middle distillates of good cold properties, high cetane indices and reduced emission of pollutant products; and(e) the heavy fraction from (D2) is submitted to a deparaffination stage (DWX) to obtain an isomerized liquid, after separation of volatile products, usable as a high quality base lubricant.The deparaffination operation is as claimed by the invention. EXAMPLE - Two deparaffination catalysts were compared, C1 (conforming) and C2 (non-conforming) to the invention.    Catalyst C1 was obtained from a synthesized ZBM-30 zeolite (in the presence of triethylenetetramine) and was calcined at 550 degrees C in air for 12 hours. The H-ZBM-30 zeolite (Si/Al = 45) was mixed with an SB3 alumina gel and formed into extrudates then calcined at 500 degrees C for 2 hours. The content of H-ZBM-30 was 80%. The extrudates were then dry impregnated with an aqueous Pt salt Pt(NH3)42+ 2OH- to give a Pt content of 0.52%.    Catalyst C2 was prepared from a zeolite ZBM-30 synthesized in the presence of hexamethylenediamine as structurant . This was calcined and mixed with SB3 alumina as before and the extrudates obtained calcined to give a H-ZBM-30 content of 80%.The support was then dry impregnated with the aqueous Pt salt to give a Pt content of 0.53%.    The two catalysts were compared in trials using a paraffin charge from a Fischer-Tropsch synthesis which was distilled to produce a 370 degrees C+ cut having the following characteristics: Initial boiling point = 356 degrees C; 95% boiling point = 631 degrees C; flow point = +83 degrees C; and density = 0.789 . The test unit consisted of an up-flow fixed bed reactor into which 80 ml of catalyst were introduced .The catalyst was first reduced under H2 at 10 MPa, then the charge injected. The total pressure was 10 MPa, H2 flow rate 1000 l H2/l of injected charge, VVH 1.1 hour-1 and reaction temperature 340 degrees C. After reaction, the effluents were fractionated into light products (petrol and middle distillates) and residue(370 degrees C+).    The results obtained were as follows:    C1 catalyst: yield of 370 degrees C+ fraction = 36.1%; flow point = -9 degrees C; viscosity index = 145; viscosity at 100 degrees C = 5.5 cSt.    C2 catalyst: yield of 370 degrees C+ fraction = 35.95%; flow point = -3 degrees C; viscosity index = 141; viscosity at 100 degrees C = 5.6 cSt.    The results indicated a better quality of oil obtained with the C1 (invention) catalyst.