Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2002-01-15
2004-05-11
Nguyen, Cam N. (Department: 1754)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111010, C208S111050, C208S111100, C208S111200, C208S112000, C502S084000, C502S241000, C502S242000, C502S246000, C502S247000, C502S248000, C502S254000, C502S255000, C502S256000, C502S257000, C502S258000, C502S259000, C502S260000, C502S261000, C502S262000, C502S263000, C502S407000, C502S415000, C502S439000
Reexamination Certificate
active
06733657
ABSTRACT:
This invention relates to a catalyst that comprises at least one silica-alumina, at least one hydro-dehydrogenating element, generally selected from among the metals of group VIB and group VIII of the periodic table (preferably molybdenum and tungsten, cobalt, nickel and iron) and optionally at least one oxide-type binder. The catalyst can also optionally contain at least one element that is selected from the group P, B, Si and optionally at least one element of group VIIA (group 17 of halogens), such as, for example, fluorine, and optionally at least one element of group VIIb (manganese, ruthenium, for example).
This invention also relates to the use of said catalyst for the hydrocracking of hydrocarbon feedstocks such as petroleum fractions, fractions that are obtained from carbon containing aromatic and/or olefinic and/or naphthenic and/or paraffinic compounds, whereby said feedstocks can contain nitrogen and/or oxygen and/or sulfur in the form of organic compounds and optionally heavy metals.
PRIOR ART
The hydrocracking of heavy petroleum fractions is a very important refining process that makes it possible to produce, from excess heavy feedstocks that cannot be readily upgraded, lighter fractions such as gasolines, jet fuels and light gas oils that the refiner seeks to adapt his production to the structure of the demand. Some hydrocracking processes make it possible also to obtain a greatly purified residue that can constitute an excellent base for oils. Relative to the catalytic cracking, the advantage of catalytic hydrocracking is to provide middle distillates, jet fuels and gas oils of very good quality. The gasoline that is produced has an octane number that is much lower than the one that is obtained from catalytic cracking.
The catalysts that are used in hydrocracking are all of the bifunctional type combining an acid function with a hydrogenating function. The acid function is provided by large-surface substrates (150 to 800 m
2
.g
−1
generally) that have a superficial acidity, such as halogenated aluminas (chlorinated or fluorinated in particular), combinations of boron and aluminum oxides, silica-aluminas and zeolites. The hydrogenating function is provided either by one or more metals of group VIII of the periodic table, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by a combination of at least one metal of group VI of the periodic table, such as molybdenum and tungsten and at least one metal of group VIII.
The balance between the two acid and hydrogenating functions is the basic parameter that governs the activity and the selectivity of the catalyst. A weak acid function and a strong hydrogenating function provide catalysts that are not very active but that work at a temperature that is generally high (greater than or equal to 390-400° C.) and at a low feed volumetric flow rate (the VVH that is expressed by volume of feedstock to be treated per unit of volume of catalyst and per hour is generally less than or equal to 2) but endowed with a very good selectivity of middle distillates. Conversely, a strong acid function and a weak hydrogenating function provide active catalysts but exhibit less favorable selectivities of middle distillates (jet fuels and gas oils). The search for an improved catalyst will therefore be centered on a judicious choice of each of the functions to adjust the activity/selectivity pair of the catalyst.
In the substrates that are not very acidic, the family of silica-aluminas is found. Many hydrocracking catalysts with a silica-alumina base are combined either with a metal of group VIII or, preferably when the contents of heteroatomic poisons of the feedstock to be treated exceed 0.5% by weight, a combination of metal sulfides of groups VIB and VIII).
Patent EP-666894-B2 teaches us that the use of a catalyst that comprises a hydrogenation component that is supported by a silica-alumina having a macroporosity (pore diameter of greater than 100 nm) that varies from 5% to 50% of the total pore volume, a total pore volume that fluctuates from 0.6 ml/g to 1.2 ml/g and an alumina content that is located in the range of 5 to 75% by weight makes it possible, in the presence of hydrogen, to treat particular feedstocks so as to obtain lubricating base oils that have a viscosity number of greater than 135. The hydrocarbon feedstock is selected from among (i) sludges, (ii) synthetic paraffin waxes and (iii) feedstocks that are obtained from a paraffinic crude that contains at least 30% by weight of wax or paraffin and that has at least 80% by weight of compounds that boil above 300° C. and at most 30% by weight of compounds that boil above 540° C.
The research work carried out by the applicant on many acidic solids and on the hydrogenating active phases led him to discover that, in a surprising way, selectivities of middle distillates (kerosene+ gas oil) that are higher than with the catalysts that contain a silica-alumina and that are known in the prior art are obtained with the catalyst according to the invention. Furthermore, very advantageously, this catalyst makes it possible to obtain higher gas oil selectivities than those of kerosene. Said catalyst comprises at least one particular silica-alumina, optionally at least one binder (generally porous, such as alumina), at least one element of group VIB of said classification (such as chromium, molybdenum or tungsten, preferably molybdenum or tungsten), even more preferably tungsten, optionally an element of group VIII (i.e., an element that is selected from the group that consists of: Fe, Ru, Os, Co, Rh, Ir, Nl, Pd, Pt, preferably iron, cobalt or nickel), optionally at least one element that is selected from the group that is formed by P, B and Si (preferably B and/or Si), optionally one element of group VIIA (and preferably fluorine) and optionally at least one element of group VIIB (and preferably manganese, ruthenium).
It was possible to observe that in hydrocracking, this catalyst has an activity that is at least equal and a middle distillate selectivity that is greater relative to the catalytic formulas that are known from the prior art.
DETAILED DESCRIPTION OF THE INVENTION
The invention has as its object a catalyst that comprises at least one hydro-dehydrogenating element (preferably deposited on the substrate), and a substrate that comprises (or preferably is constituted by) at least one silica-alumina, whereby said silica-alumina has the following characteristics:
a content by weight of silica SiO
2
of between 10 and 60%, preferably between 20 and 60%, and even more preferably between 30 and 50% by weight,
an Na content that is less than 300 ppm by weight and preferably less than 200 ppm by weight,
a total pore volume of between 0.5 and 1.2 ml/g that is measured by mercury porosimetry,
whereby the porosity of said silica-alumina is as follows:
i/ The volume of mesopores whose diameter is between 40 Å and 150 Å and whose mean diameter varies between 80 and 120 Å represents between 30 and 80% of the total pore volume that is defined above and preferably between 40 and 70%.
ii/ The volume of the macropores, whose diameter is greater than 500 Å and preferably between 1000 Å and 10,000 Å, represents between 20 and 80% of the total pore volume and preferably between 30 and 60% of the total pore volume, and even more preferably the volume of the macropores represents at least 35% of the total pore volume.
A specific surface area that is greater than 200 m
2
/g and preferably greater than 250 m
2
/g.
The following measurements have also been carried out on the silica-alumina:
The diffractograms of the silica-aluminas of the invention, obtained by x-ray diffractions, correspond to a mixture of the silica and alumina with a certain evolution between gamma alumina and the silica based on the SiO
2
content of the samples. In these silica-aluminas, a less well crystallized alumina relative to the alumina by itself is observed,
The spectra of the NMR of
27
Al of the silica-aluminas show two solid masses
Benazzi Eric
Cseri Tivadar
Euzen Patrick
Roy-Auberger Magalie
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Nguyen Cam N.
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