Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2001-05-16
2003-06-10
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S171000, C208S027000, C208S111100, C208S110000, C208S112000, C208S109000, C208S108000, C502S060000
Reexamination Certificate
active
06576120
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for the catalytic dewaxing of a hydrocarbon feed comprising waxy molecules by contacting the hydrocarbon feed under catalytic dewaxing conditions with a catalyst composition comprising metallosilicate crystallites, a binder and a hydrogenation component. With the term comprising used in this specification is meant comprising at least meaning that also other components may be present in, for example the catalyst composition or hydrocarbon feed.
BACKGROUND OF THE INVENTION
Such a process is described in EP-A-185448. This patent publication discloses a process for the manufacture of lubricating oils in which a hydrocarbon feedstock is subjected to catalytic dewaxing in the presence of a catalyst composition consisting of ZSM-22, an alumina binder and platinum. The catalyst was prepared by impregnating an extrudate consisting of 65 wt % ZSM-22 and 35 wt % alumina resulting in a catalyst containing 0.57 wt % of platinum.
There is a continuous effort in the field of catalytic dewaxing of improving the yield and the viscosity index (VI) of the lubricating obtained by said process. Furthermore efforts are made to provide a catalytic dewaxing process which can compete with solvent dewaxing processes in respect of for example oil yield and viscosity index at the same pour point specification. Solvent dewaxing is a difficult to operate semi-continuous process. Being able to replace a solvent extraction process by a catalytic dewaxing process is therefore desirable.
SUMMARY OF THE INVENTION
The object of the invention has been achieved when the weight ratio of the metallosilicate crystallites and the binder is between 5:95 and 35:65.
It has been found that with the present process a high yield of base oil product can be obtained at the same weight hourly space velocity. This implies that with a lower amount of metallosilicate crystallites more dewaxing selectivity is achieved. Furthermore it results in that the catalyst employed in the process according to the invention is cheaper than the prior art catalysts because less of the relatively more expensive metallosilicate crystallites is used in the catalyst composition. An additional advantage is that the gas make is lower with the present process.
WO-A-9617902 describes a catalyst composition for the catalytic dewaxing comprising of a aluminosilicate zeolite material and a binder in amounts from 80:20 to 20:80 by weight and typically from 80:20 to 50:50 zeolite:binder.
EP-A-304251 describes a catalytic dewaxing process in which preferably a catalyst composition is used without a binder. The catalyst used in the experiments is a nickel on ZSM-5 catalyst without a binder.
DETAILED DESCRIPTION OF THE INVENTION
By catalytic dewaxing is here meant a process for decreasing the pour point of lubricating base oil products by selectively converting the components of the oil feed which impart a high pour point to products which do not impart a high pour point. Products which impart a high pour point are compounds having a high melting point. These compounds are referred to as waxes. Wax compounds include for example high temperature melting normal paraffins, iso-paraffins and mono-ringed compounds. The pour point is preferably reduced by at least 10° C. and more preferably by at least 20° C. The hydrocarbon oils to be used as feed in the process according to the present invention will thus contain waxy molecules which impart an undesirable high pour point. Small amounts of these compounds can strongly influence the pour point. The feed will suitably contain between about 1% and up to 100% of these waxy compounds.
Suitable hydrocarbon oil feeds to be employed in the process according to the present invention are mixtures of high-boiling hydrocarbons, such as, for instance, heavy oil fractions. It has been found particularly suitable to use vacuum distillate fractions derived from an atmospheric residue, i.e. distillate fractions obtained by vacuum distillation of a residual fraction which in return is obtained by atmospheric distillation of a crude oil, as the feed. The boiling range of such a vacuum distillate fraction is usually between 300 and 620° C., suitably between 350 and 580° C. However, deasphalted residual oil fractions, including both deasphalted atmospheric residues and deasphalted vacuum residues, may also be applied. If the vacuum distillate fractions contain substantial amounts of sulphur- and nitrogen-containing contaminants, for example, having sulphur levels up to 3% by weight and nitrogen levels up to 1% by weight, it may be advantageous to treat this feedstock to a hydrodesulphurisation and hydrodenitrogenation step prior to the catalytic dewaxing process according to the present invention.
Examples of feeds having relatively high amounts of waxy compounds are synthetic waxy raffinates (Fischer-Tropsch waxy raffinates), hydrocracker bottom fractions (hydrowax), i.e. those fractions having an effective cutpoint of at least 320° C., preferably at least 360° C. and slack waxes obtained from the dewaxing of hydro-processed or solvent refined waxy distillates. These feeds have a wax content of at least 50% by weight, preferably at least 80% by weight and more preferably at least 90% by weight. These feeds are used to prepare lubricating base oils having viscosity indices (VI) above 120 and particularly above 135.
Prior to the catalytic dewaxing process according to the invention the vacuum distillate fraction or any other sulphur or nitrogen containing feedstock is preferably treated to a hydrotreating step in order to reduce the concentration of sulphur and/or nitrogen in the feed. The hydrotreating step preferably involves contacting the feed with hydrogen in the presence of a suitable catalyst. Such catalysts are known in the art and in principle any hydrotreating catalyst known to be active in the hydrodesulphurisation and hydrodenitrogenation of the relevant hydrocarbon feeds may be used. Suitable catalysts, then, include those catalysts comprising as the non-noble Group VIII metal component one or more of nickel (Ni) and cobalt (Co) in an amount of from 1 to 25 percent by weight (%wt), preferably 2 to 15% wt, calculated as element relative to total weight of catalyst and as the Group VIB metal component one or more of molybdenum (Mo) and tungsten (W) in an amount of from 5 to 30% wt, preferably 10 to 25% wt, calculated as element relative to total weight of catalyst. These metal components may be present in elemental, oxidic and/or sulphidic form and are supported on a refractory oxide carrier. The refractory oxide support of the first stage catalyst may be any inorganic oxide, alumino-silicate or combination of these, optionally in combination with an inert binder material. Examples of suitable refractory oxides include inorganic oxides, such as alumina, silica, titania, zirconia, boria, silica-alumina, fluorided alumina, fluorided silica-alumina and mixtures of two or more of these. In a preferred embodiment an acidic carrier such as alumina, silica-alumina or fluorided alumina is used as the refractory oxide carrier. The refractory oxide support may also be an aluminosilicate. Both synthetic and naturally occurring aluminosilicates may be used. Examples are natural or dealuminated zeolite beta, faujasite and zeolite Y. From a selectivity point of view it is preferred to use the dealuminated form of these zeolites. A preferred aluminosilicate to be applied is alumina-bound, at least partially dealuminated, zeolite Y.
Catalytic dewaxing conditions are known in the art and typically involve operating temperatures in the range of from 200 to 500° C., suitably from 250 to 400° C., hydrogen pressures in the range of from 10 to 200 bar, suitably from 15 to 100 bar, more suitably from 15 to 65 bar, weight hourly space velocities (WHSV) in the range of from 0.1 to 10 kg of oil per liter of catalyst per hour (kg/l/hr), suitably from 0.2 to 5 kg/l/hr, more suitably from 0.5 to 3 kg/l/hr and hydrogen to oil ratios in the range of from 100 to 2,000 liters of hydrogen per liter of
Creyghton Edward Julius
Crijnen-Van Beers Maria Barbara Hendrica
Darnanville Jean-Paul
Duprey Eric
Huve Laurent Georges
Arnold Jr. James
Griffin Walter D.
Shell Oil Company
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