Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Sulfur or compound containing same
Reexamination Certificate
1999-05-05
2001-12-11
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Sulfur or compound containing same
C502S200000, C502S219000, C502S221000, C502S306000, C502S325000, C502S337000
Reexamination Certificate
active
06329314
ABSTRACT:
This invention relates to a process for activation of a catalyst that is used in particular in the hydroconversion stage in hydrocracking units of petroleum feedstocks, the catalyst that is obtained by this process and its use in hydroconversion.
The hydrocracking process of heavy petroleum fractions is a very important refining process that makes it possible to produce lighter fractions such as gasolines, jet fuels and light gas oils from excess heavy feedstocks that cannot be readily upgraded. Such feedstocks are sought by refiners to adapt their production to the demand.
Relative to the catalytic cracking process, the advantage of the catalytic hydrocracking process is to provide middle distillates, jet fuels and gas oils of very good quality. By contrast, the gasoline that is produced has a lower octane number than that that is obtained from catalytic cracking.
The hydrocracking process thus exhibits great flexibility at various levels: flexibility at the level of the catalysts that are used, which generates a flexibility of the feedstocks that are to be treated and thus makes it possible to obtain a variety of products.
The different stages of the hydrocracking process are carried out in the presence of hydrogen. This process makes possible the conversion of middle or heavy distillates and optionally residues that are deasphalted (atmospheric or vacuum) into gasolines, jet fuels and gas oils, whereby the selection of the conversion is determined based on geographic and seasonal needs of the markets. The hydrocracking process can also be used for obtaining light hydrocarbons (propane and butanes) or oil bases for engines with enhanced viscosimetric qualities. Relative to the catalytic cracking process, the hydrocracking process makes it possible to convert heavy fractions into light products that are more readily upgraded but under very different conditions. The hydrocracking process is carried out at relatively low temperatures (350° C. to 450° C.) and under a high hydrogen partial pressure (2.5 to 30 MPa). According to the nature of the feedstocks that are to be treated, desired products and performance levels of catalysts, several process diagrams (flow sheets) have been designed.
The process diagrams can be divided into two categories: the so-called “one stage” or else “without intermediate separation” or else “series flow” process diagram and the so-called “two stage” or else “with intermediate separation” process diagram.
In the “one stage” process, the feedstock is previously hydrotreated on a catalyst to carry out reactions of hydrodesulfurization, hydrodenitrating, hydrogenation of aromatic compounds as well as optionally hydroconversion. The effluents of this stage including gases are then admitted on a second (or several) catalyst that is much more acidic and that more particularly carries out hydroconversion reactions.
In the “two stage” process, an intermediate separation is initiated between the hydrotreatment stage and the hydroconversion stage, whose purpose is to eliminate the hydrogen sulfide (H
2
S) and ammonia (NH
3
) to “protect” the hydroconversion catalyst from deteterious partial pressures of H
2
S and NH
3
. The advantages of one or the other of the diagrams depends strongly on the required flexibility and the characteristics of the feedstock.
Regardless of the type of process, two sections are always distinguished:
a high-pressure section that comprises one or more furnaces that are intended to heat the feedstock and the hydrogen, one or more reactors, one or more heat exchangers, a condenser, a gas-liquid separator, a recycling compressor and one or more make-up compressors;
a low-pressure section that ensures the stabilization and the fractionation of reaction products.
The petroleum fractions that are to be treated are heavy fractions such as vacuum distillates, deasphalted or hydrotreated residues. These heavy fractions preferably consist of at least 80% by volume of compounds whose boiling points are greater than 350° C. and preferably between 350° C. and 580° C. (i.e., they correspond to compounds that contain 15 to 40 carbon atoms). These heavy fractions also generally contain heteroatoms, such as sulfur and nitrogen. Relative to the weight of the feedstock, the nitrogen content is generally between 1 and 5000 ppm by weight, the sulfur content is generally between 0.01 and 5% by weight, and the total content of metals, which are typically vanadium, nickel, and arsenic, is less than 200 ppm. The conditions of the hydroconversion reaction such as temperature, pressure, hydrogen recycling rate, and hourly volumetric flow rate are very variable based on the nature of the feedstock, the quality of the desired products, and installations that the refiner uses.
A hydrocracking unit often uses several types of catalysts.
Generally, the catalysts that are located at the top are optimized to carry out the reactions of the hydrotreatment stage. The—first stage—hydrotreatment catalyst(s) comprises a matrix that contains at least one metal that has a hydro-dehydrogenating function, preferably this matrix contains alumina, and preferably this matrix does not contain zeolite. Said matrix can also contain silica, silica-alumina, boron oxide, magnesia, zirconia, titanium oxide or a combination of these oxides. The hydro-dehydrogenating function of this matrix is ensured by at least one metal or metal compound of group VIII of the periodic table (Handbook of Chemistry and Physics, 76th Edition, 1995-1996) such as in particular nickel and cobalt. The hydro-dehydrogenating function of this matrix can also be ensured by a combination of at least one metal or metal compound of group VI of the periodic table, in particular molybdenum and tungsten, and at least one metal or metal compound of group VIII, in particular cobalt and nickel. The total concentration of oxides of metals of groups VI and VIII is between 5 and 40% by weight and preferably between 7 and 30% by weight relative to the weight of the finished catalyst, whereby the ratio by weight that is expressed in terms of metal (or metals) of group VI to metal (or metals) of group VIII is between 1.25 and 20 and preferably between 1.5 and 10.
The expressions “element of the group” and “metal of the group” will be used equally in this description.
In addition, this catalyst can contain phosphorus, and the phosphorus content, expressed in diphosphorus pentoxide P
2
O
5
concentration in the finished catalyst, is generally at most 15%, preferably between 0.1 and 15% by weight and still more preferably between 0.15 and 10% by weight relative to the catalyst.
The catalysts that are used in the hydroconversion stage are all of the bifunctional type that combine an element that contains an acid function with an element that contains a hydrogenating function. The acid function is provided by large surface substrates (150 to 800 m
2
·g
−1
generally) that exhibit surface acidity. The acid substrates that are generally selected are halogenated aluminas (chlorinated or fluorinated in particular), combinations of boron and aluminum oxides, amorphous 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 chromium, molybdenum and tungsten and at least one metal of group VIII.
The balance between the 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 low-activity catalysts that work at a generally high temperature (greater than or equal to 390° C.), and at a low feed volumetric flow rate (the VVH that is expressed by volume of the feedstock that is to be treated per unit of volume of catalyst and per hour is generally less than or equal to 2) but are endowed with very good selectivity in middle distillates. Conversely, a strong acid fu
Harle Virginie
Kasztelan Slavik
Marchal-George Nathalie
Mignard Samuel
Griffin Steven P.
Ildebrando Christina
Institu Francais du Petrole
Millen White Zelano & Branigan P.C.
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