Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2000-05-18
2002-05-14
Griffin, Steven P. (Department: 1754)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111300, C208S111350, C502S064000, C502S066000, C502S074000, C502S079000
Reexamination Certificate
active
06387246
ABSTRACT:
This invention relates to a catalyst that contains at least one matrix, a partially amorphous Y zeolite, optionally at least one hydro-dehydrogenating metal, preferably selected from the group that is formed by the metals of group VIB and group VIII of the periodic table, optionally at least one element that is selected from the group that is formed by phosphorus, boron and silicon, optionally at least one element of group VIIA, and optionally at least one element of group VIIB. The invention also relates to the use of this catalyst in hydroconversion, in particular hydrocracking of the hydrocarbon feedstocks and very particularly for obtaining high viscosity oils that have viscosity numbers (VI) that are greater than 95-100, preferably between 95-150 and more particularly between 120-140.
The catalyst can also be used in hydrorefining hydrocarbon feedstocks.
The hydrocracking of heavy petroleum fractions is a very important refining process that makes it possible to produce, starting 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. Certain hydrocracking processes make it possible also to obtain a greatly purified residue that can constitute excellent bases for oils. Relative to the catalytic cracking, the advantage of the catalytic hydrocracking is to provide middle distillates, jet fuels and gas oils of very good quality. The gasoline that is produced has a much lower octane number than the one that is obtained from the catalytic cracking.
The catalysts that are used in hydrocracking are all of bifunctional type that link an acid function to a hydrogenating function. The acid function is provided by large-surface substrates (generally 150 to 800 m
2
·g
−1
) that have a surface acidity, such as halogenated aluminas (in particular chlorinated or fluorinated), combinations of boron oxides and aluminum oxides, amorphous silica-aluminas and zeolites. The hydrogenating function is provided either by one or several metals of group VIII of the periodic table, or by a combination of at least one metal of group VIB of the periodic table and at least one metal of group VIII.
The balance between the two acid and hydrogenating functions is the basic parameter that controls the activity and the selectivity of the catalyst. A weak acid function and a strong hydrogenating function provide catalysts that are not very active and that work at a temperature that is generally high (greater than or equal to 390° C.) and at a low feed volumetric flow rate (the VVH 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 h
−1
) but provided with very good selectivity of middle distillates. Conversely, a strong acid function and a weak hydrogenating function provide catalysts that are active but that have less favorable selectivities of middle distillates. The search for a suitable catalyst will therefore be centered on a judicious choice of each of the functions for adjusting the activity/selectivity pair of the catalyst.
Thus, one of the great advantages of the hydrocracking is to exhibit a great flexibility at various levels: flexibility with regard to the catalysts used, which brings about flexibility of the feedstocks that are to be treated and with regard to products that are obtained. An easy parameter to control is the acidity of the substrate of the catalyst.
The conventional catalysts for catalytic hydrocracking, for the large majority, consist of weakly acidic substrates, such as amorphous silica-aluminas, for example. These systems are used more particularly for producing middle distillates of very good quality and also oil bases when their acidity is very weak.
The family of amorphous silica-aluminas is found in slightly acid substrates. Many catalysts of the hydrocracking market have a silica-alumina base combined either with a metal of group VIII or, preferably when the heteratomic poison contents of the feedstock to be treated exceed 0.5% by weight, with a combination of sulfides of the metals of groups VIB and VIII. These systems have very good selectivity in middle distillates, and the products that are formed are of good quality. These catalysts, for the less acidic among them, can also produce lubricating bases. The drawback of all of these catalytic systems with an amorphous substrate base is their weak activity, as mentioned.
The catalysts that comprise the FAU-structural-type Y zeolite or the beta-type catalysts have a higher catalytic activity than those of the amorphous silica-aluminas but have higher selectivities in light products.
Hydrotreatment takes on increasing importance in the practice of refining with the growing necessity to reduce the amount of sulfur in the petroleum fractions and to convert heavy fractions into lighter fractions that can be upgraded as fuels. This results in, on the one hand, the growing demand for fuels that requires converting increasingly rich imported crude oils into heavy fractions and into heteroatoms, including nitrogen and sulfur, and, on the other hand, specifications that are imposed on the contents of sulfur and aromatic compounds in various countries for commercial fuels. This upgrading involves a relatively significant reduction of the molecular weight of the heavy components, which can be obtained with, for example, cracking reactions.
The current processes for catalytic hydrorefining use catalysts that can promote the main reactions that are useful for exploiting heavy fractions, in particular the hydrogenation of the aromatic cores (HAR), hydrodesulfurization (HDS), hydrodenitrating (HDN) and other hydroeliminations. Hydrorefining is used to treat feedstocks such as gasolines, gas oils, vacuum gas oils, residues under conditions of atmosphere or a vacuum that may or may not be deasphalted. For example, cracking and catalytic hydrocracking processes are indicated for the pretreatment of the feedstocks. The nitrogen-containing heterocyclic compounds that are encountered in the heavy fractions act as poisons with very marked toxicity for the cracking or hydrocracking catalysts. Consequently, the denitrating of the catalytic hydrocracking feedstocks constitutes one of the possible means for improving the overall yield of these processes, and it is then desirable to reduce as much as possible the nitrogen content of the feedstocks before cracking them. At least one hydrorefining stage is usually integrated into each of the known diagrams for upgrading heavy petroleum fractions.
In the prior art, the zeolites used for the preparation of hydrocracking catalysts are characterized by several magnitudes like their SiO2/Al203 framework molar ratio, their crystalline parameter, their pore distribution, the specific surface area, their sodium ion uptake capacity, or else their capacity for adsorption of water vapor. Thus, the above patents of the applicant (French Patents FR-A-2,754,742 and FR-A-2,754,826) use a zeolite whose crystalline parameter is between 24.15 and 24.38 &Lgr; (1 &Lgr;=0.1 nm), the SiO2/Al203 framework molar ratio between 500 and 21, the sodium content less than 0.15% by weight, the sodium ion uptake capacity greater than 0.85 g of Na/100 g of zeolite, the specific surface area greater than 400 m2/g, the adsorption capacity of the water vapor greater than 6%, and 1 to 20% of the pore volume is contained in the pores with a diameter of between 20 and 80 Å.
U.S. Pat. No. 4,857,170 describes the use in hydrocracking of a modified zeolite with a crystalline parameter that is less than 24.35 Å but on whose degree of crystallinity there is no effect from the modifying treatments.
Moreover, the prior art shows that an effort has always been made to maintain crystalline fractions (or degree of crystallinity) and high peak rates in the zeolites that are used.
The research work that is carried out by the applicant on numerous zeolites and microporous solids led him to discove
Benazzi Eric
Chaigne Frederic
Cseri Tivadar
Deves Jean-Marie
Kasztelan Slavik
Griffin Steven P.
Ildebrando Christina
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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