Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2000-05-18
2002-06-11
Griffin, Steven P. (Department: 1754)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111300, C208S111350, C208S058000, C208S059000, C502S064000, C502S065000, C502S074000, C502S079000
Reexamination Certificate
active
06402936
ABSTRACT:
This invention relates to a catalyst of hydrocarbon feedstocks, whereby said catalyst comprises at least one partially amorphous Y zeolite, at least one metal of group VB, preferably niobium, at least one oxide-type amorphous or poorly crystallized matrix, optionally at least one metal that is selected from group VIB and group VIII of the periodic table, preferably molybdenum and tungsten, cobalt, nickel and iron. The matrix of the catalyst also optionally contains at least one element that is selected from the group P, B, and Si and optionally at least one element of group VIIA (group 17 of the halogens), such as, for example, fluorine.
This invention also relates to the processes for preparation of said catalyst, as well as its use for hydrocracking hydrocarbon feedstocks such as the petroleum fractions, whereby the fractions that are obtained from carbon contain aromatic compounds, and/or olefinic compounds and/or naphthenic compounds and/or paraffinic compounds, whereby said feedstocks optionally contain metals and/or nitrogen and/or oxygen and/or sulfur. The invention also relates to the use of the catalyst for 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 an excellent base 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, 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 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) 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 catalysts that comprise, for example, a beta-type zeolite have a higher catalytic activity than those of the amorphous silica-aluminas, but they have higher selectivities in light products. In the prior art, the zeolites used for the preparation of hydrocracking catalysts are characterized by several magnitudes like their SiO2/Al
2
O
3
framework molar ratio, their crystalline parameter, their pore distribution, their 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 Ä, the SiO
2
,Al
2
O
3
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 Ä.
In all of the cases of the prior art, the zeolites that are used have high crystalline fractions (or degree of crystallinity) and high peak rates.
Furthermore, simple sulfides of elements of group VB have been described as components of hydrorefining catalysts of hydrocarbon feedstocks, such as, for example, the niobium trisulfide in U.S. Pat. No. 5,294,333. Mixtures of simple sulfides that comprise at least one element of group VB and an element of group VIB also have been tested as components of hydrorefining catalysts of hydrocarbon feedstocks, such as, for example, in U.S. Pat. Nos. 4,910,191 or 5,275,994.
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, vacuum gas oils, residues under conditions of atmosphere or a vacuum that may or may not be deasphalted. For example, catalytic cracking and hydrocracking processes are indicated for the treatment of 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 designs known for upgrading heavy petroleum fractions.
The research work that is carried out by the applicant on numerous zeolites and microporous solids and on hydrogenating active phases led him to discover that, surprisingly enough, selectivities of middle distillates (kerosene+gas oil) that are h
Benazzi Eric
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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