Process for the conversion of a paraffinic feedstock
View Patent ↗The disclosure relates to the conversion of a paraffinic feedstock that comprises at least 50 wt % of compounds boiling above 370° c. and which has a paraffin content of at least 60 wt %, an aromatics content of below 1 wt %, a naphthenic content below 2 wt %, a nitrogen content of below 0.1 wt % The process includes: a) subjecting the paraffinic feedstock to a hydroprocessing step to obtain an at least partially isomerized feedstock; and b) separating the at least partially isomerized feedstock into one or more middle distillate fractions and a first residual fraction. Step (a) is carried out by contacting the paraffinic feedstock with a first catalyst having hydrocracking and hydroisomerizing activity and then with a second catalyst having hydrocracking and hydroisomerizing activity. The second catalyst is more active in hydroisomerization and less active in hydrocracking than the first catalyst.
1. A process for the conversion of a paraffinic feedstock that comprises at least 50 wt % of compounds boiling above 370° C. and which has a paraffin content of at least 60 wt %, an aromatics content of below 1 wt %, a naphthenic content below 2 wt %, a nitrogen content of below 0.1 wt %, and a sulphur content of below 0.1 wt %, the process comprising:
a) subjecting the paraffinic feedstock to a hydroprocessing step to obtain an at least partially isomerised feedstock;
b) separating the at least partially isomerised feedstock into one or more middle distillate fractions and a first residual fraction,
wherein step a) is carried out by contacting the paraffinic feedstock with a first catalyst having hydrocracking and hydroisomerising activity and then with a second catalyst having hydrocracking and hydroisomerising activity, wherein the second catalyst is a silica-bound, ammonium hexafluorosilicate-treated Pt/ZSM-12 catalyst which is more active in hydroisomerisation and less active in hydrocracking than the first catalyst.
2. A process according to claim 1 , wherein the first catalyst comprises a Group VIII noble metal supported on an amorphous acidic carrier.
3. A process according to claim 1 , further comprising:
c) subjecting at least part of the first residual fraction to vacuum distillation to obtain a distillate base oil fraction and a second residual fraction.
4. A process according to claim 3 , wherein the second residual fraction is recycled to step a).
5. A process according to claim 3 , wherein the process further comprises:
d) subjecting the distillate base oil fraction obtained in step c) to a catalytic dewaxing step to obtain dewaxed base oil fraction.
6. A process according to claim 1 , wherein the paraffinic feedstock is derived from a Fischer Tropsch process.
7. A process according to claim 1 , wherein step a) is carried out in a reactor comprising the first catalyst above the second catalyst in a stacked bed configuration.
8. A process according to claim 1 , wherein the ratio of volume of the first catalyst and volume of the second catalyst is at least 1.0.
9. A process according to claim 8 , wherein ratio of volume of the first catalyst and volume of the second catalyst is in the range of from 1.5 to 10.
10. A process according to claim 2 , wherein the amorphous acidic carrier of the first catalyst is silica-alumina.
11. A process according to claim 1 , wherein the Group VIII noble metal of the first catalyst is platinum.
12. A process according to claim 11 wherein the first catalyst comprises platinum supported on a silica-alumina carrier.
13. A process according to claim 1 wherein step a is performed such that both catalysts are operated at a temperature deviating no more than 20° C. from each other.