Process For The Conversion Of A Paraffinic Feedstock (Shell)

CATEGORY: PARAFFINS
Process For The Conversion Of A Paraffinic Feedstock (Shell)
United States Patent Application 20160251583
JANSSEN; Andries Hendrik ;   et al.   September 1, 2016
Applicant: SHELL OIL COMPANY
Abstract
The invention relates to a process for the conversion of a paraffinic feedstock that comprises at least 50 wt % of compounds boiling above 370.degree. 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 more active in hydroisomerisation and less active in hydrocracking than the first catalyst.
FIELD OF THE INVENTION
[0001] The invention relates to a process for the conversion of a paraffinic feedstock, in particular for the conversion of a paraffinic feedstock derived from a Fischer-Tropsch synthesis process.
BACKGROUND TO THE INVENTION
[0002] It is known to prepare one or more middle distillate fractions such as for example kerosene or gasoil and a base oil precursor or a base oil from a Fischer-Tropsch derived feedstock.
[0003] In WO02/076027 for example, is disclosed a process wherein two or more lubricating base oil grades and a gas oil are obtained by hydrocracking/hydroisomerising a C5+ Fisher-Tropsch product over a catalyst comprising platinum supported on a silica-alumina carrier prepared from amorphous silica-alumina and separating the product thus obtained in one or more gasoil fractions and a base oil precursor fraction. After performing a pour point reducing step, for example catalytic dewaxing, to the base oil precursor fraction, the base oil precursor fraction is separated into two or more base oil grades.
[0004] In WO2009/080681 is disclosed a process to prepare a gas oil and a base oil from a Fischer-Tropsch derived feedstock, wherein the feedstock is subjected to a hydroprocessing step to obtain an isomerised feedstock, separating the isomerised feedstock by means of distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction, recycling at least part of the heavy distillate fraction to the hydroprocessing step and reducing the pour point of the residual fraction by means of catalytic dewaxing to obtain the base oil.
[0005] There is, however, still a need for improvement of middle distillate products and base oils from paraffinic feedstocks, such as Fischer-Tropsch derived feedstocks, in particular with respect to the cold flow properties of the base oil and/or middle distillate products.
SUMMARY OF THE INVENTION
[0006] It has now been found that by using two different catalysts in series in the hydrocracking/hydroisomerising of a paraffinic feedstock, in particular a Fischer-Tropsch derived feedstock, wherein both catalysts have hydrocracking and hydroisomerising activity and the second catalyst is more active in hydroisomerisation and less active in hydrocracking compared to the first catalyst, a product is obtained from which lubricating base oils with improved cold flow properties can be prepared. Moreover, one or more middle distillate fractions with improved yield and/or cold flow properties can be obtained.
[0007] Accordingly, the present invention relates to a process for the conversion of a paraffinic feedstock that comprises at least 50 wt % of compounds boiling above 370.degree. 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: [0008] a) subjecting the paraffinic feedstock to a hydroprocessing step to obtain an at least partially isomerised feedstock; [0009] 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 more active in hydroisomerisation and less active in hydrocracking than the first catalyst.
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