Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
1998-10-20
2001-01-16
Dunn, Tom (Department: 1754)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111300, C208S111350, C502S064000, C502S066000, C502S074000, C502S079000
Reexamination Certificate
active
06174429
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst for hydrocracking feedstocks that contain hydrocarbon, whereby said catalyst comprises at least one metal from group VIB (group 6 according to the new notation of the periodic table: Handbook of Chemistry and Physics, 76th Edition, 1995-1996), preferably molybdenum and tungsten, and optionally at least one metal from group VIII (groups 8, 9 and 10) of said classification, preferably cobalt, nickel and iron, combined with a substrate that comprises an amorphous or poorly crystallized porous alumina matrix and a non-dealuminated zeolite Y that has a crystalline parameter that is greater than 2,438 nm. The alumina matrix of the catalyst contains phosphorus and optionally at least one element from group VIIA (group 17 of halogens) and in particular fluorine.
This invention also relates to the process for preparation of said catalyst, as well as its use for hydrocracking of feedstocks that contain hydrocarbon, such as petroleum fractions and carbon-derived fractions that contain sulfur and nitrogen in the form of organic compounds, whereby said feedstocks optionally contain metals and/or oxygen.
BACKGROUND OF THE INVENTION
The conventional hydrocracking of petroleum fractions is a very important refining process that makes it possible to produce, from excess heavy feedstocks that contain hydrocarbon, fractions that are lighter than gasolines, jet fuels, and light gas-oils that the refiner seeks in order to adapt production to demand. Compared to catalytic cracking, the advantage of catalytic hydrocracking is to provide middle distillates, jet fuels, and gas-oils of very good quality.
The catalysts that are used in conventional hydrocracking are all of the bifunctional type that combine an acid function with a hydrogenating function. The acid function is provided by substrates with large surface areas (generally 150 to 800 m
2
g
−1
) that have a surface acidity, such as the 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 from group VI of the periodic table, such as chromium, molybdenum, and tungsten and at least one metal from group VIII that is preferably not a noble metal.
The balance between the acid function and the hydrogenating function is the main parameter that controls the activity and 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 volumetric flow rate at low feed rate (VVH expressed by volume of feedback to be treated per unit of volume of catalyst and per hour is generally less than or equal to 2) but that have good selectivity for middle distillates. Conversely, a strong acid function and a weak hydrogenating function provide catalysts that are very active but have poor selectivity for middle distillates. Furthermore, a weak acid function is less sensitive to deactivation, in particular by nitrogenous compounds, than a strong acid function. The challenge therefore is to select judiciously each of the functions in order to adjust the activity/selectivity pair of the catalyst.
The low-acidity substrates generally consist of amorphous or poorly crystallized oxides. The low-acidity substrates include the family of amorphous silica-aluminas. Some of the catalysts on the hydrocracking market consist of silica-alumina combined with a combination of sulfides of the metals of groups VIB and VIII. These catalysts make it possible to treat feedstocks that have high contents of heteroatomic poisons, sulfur, and nitrogen. These catalysts have very good selectivity for middle distillates; they are very resistant to the strong nitrogen content, and the products that are formed are of good quality. The drawback of these catalytic systems with an amorphous substrate base is their low activity.
The substrates that have strong acidity generally contain a dealuminated zeolite, for example of the dealuminated Y type or USY (Ultra Stable Y zeolite), combined with a binder, for example alumina. Some catalysts on the hydrocracking market consist of dealuminated zeolite Y and alumina, which is combined either with a metal from group VIII or with a combination of sulfides of the metals of groups VIB and VIII. These catalysts are preferably used for treating feedstocks whose contents of heteroatomic poisons, sulfur, and nitrogens are less than 0.01% by weight. These systems are very active, and the products that are formed are of good quality. The drawback to these catalytic systems with a zeolite substrate base is their selectivity for middle distillates, which is not quite as good as that of catalysts with an amorphous substrate base and very high sensitivity to nitrogen content. These catalyst can tolerate only low nitrogen contents in the feedstock, generally less than 100 ppm by weight.
SUMMARY OF THE INVENTION
The applicant has discovered that, to obtain a hydrocracking catalyst that has a good level of activity and good stability based on feedstocks with high nitrogen content, it is advantageous to combine an acidic amorphous oxide matrix of the alumina type and doped with phosphorus and optionally at least one element from group VIIA and in particular fluorine with a very acidic zeolite Y that is not fully dealuminated.
Zeolite that is not fully dealuminated is defined as a zeolite Y with a faujasite structure (Zeolite Molecular Sieves Structure, Chemistry and Uses, D. W. BRECK, J. WILLEY and Sons 1973). The crystalline parameter of this zeolite may have decreased in value due to the extraction of aluminum from the structure of framework during preparation, but the overall SiO
2
/Al
2
O
3
ratio has not changed since the aluminum has not been extracted chemically. Such a zeolite that is not fully dealuminated therefore has a silicon and aluminum composition that is expressed by the overall SiO
2
/Al
2
O
3
ratio that is equivalent to the starting non-dealuminated zeolite Y. This zeolite Y that is not fully dealuminated may be in hydrogen form or may be at least partially exchanged with metallic cations, for example with cations of alkaline-earth metals and/or cations of rare earth metals of atomic numbers 57 to 71 inclusive. A zeolite that is lacking in rare earths and alkaline-earths will be preferred, likewise for the catalyst.
The zeolite that is not fully dealuminated may be obtained by any treatment that does not extract the aluminum from the sample, such as, for example, treatment with water vapor, treatment by SiCl
4
etc.
The catalyst of this invention generally contains, in % by weight relative to the total mass of the catalyst, at least one metal that is selected from the following groups and with the following contents:
1 to 40%, preferably 3 to 45% and even more preferably 5 to 30% of at least one metal from group VIB,
and/or,
0.1 to 30%, preferably 0.1 to 25% and even more preferably 0.1 to 20% of at least one metal from group VIII, whereby the catalyst also contains:
1 to 99%, preferably 10 to 98% and even more preferably 15 to 95% and at least one amorphous or poorly crystallized alumina matrix,
0.1 to 80%, or else 0.1 to 60% and preferably 0.1-30%, indeed 0.1-20% and even 0.1-12%, of at least one zeolite Y that is not fully dealuminated with a crystalline parameter that is greater than 2,438 nm,, an overall SiO
2
/Al
2
O
3
molar ratio that is less than 8, a framework SiO
2
/Al
2
O
3
molar ratio that is calculated according to the so-called Fichtner-Schmittler correlation (in Cryst. Res. Tech. 1984, 19, K1) that is less than 21 and greater than SiO
2
/Al
2
O
3
overall.
0.1 to 20%, preferably 0.1 to 15% and even more preferably 0.1 to 10% of phosphorus,
and optionally,
0 to 20%, preferably 0.1 to 15%, and even more prefer
George-Marchal Nathalie
Kasztelan Slavik
Mignard Samuel
Dunn Tom
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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