Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
1999-05-05
2003-02-25
Silverman, Stanley S. (Department: 1754)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S111010, C208S111300, C208S111350, C502S064000, C502S066000, C502S074000, C502S073000
Reexamination Certificate
active
06524470
ABSTRACT:
The present invention relates to a catalyst for use in converting hydrocarbon-containing feeds, in particular for hydrocracking hydrocarbon-containing feeds, said catalyst comprising at least one hydro-dehydrogenating metal, for example, selected from metals from group VIB and VIII (group 6 and groups 8, 9 and 10 in the new periodic table notation: Handbook of Chemistry and Physics, 76
th
edition, 1995-1996, inside front cover), at least one porous amorphous or low crystallinity matrix (generally an oxide) and at least one beta zeolite preferably dealuminated. The catalyst also contains at least one promoter element deposited on the catalyst and selected from the group formed by boron, silicon and phosphorous. The catalyst also optionally contains at least one group VIIA element (group 17, the halogens), in particular fluorine, and optionally at least one group VIIB element such as manganese, technetium or rhenium.
The present invention also relates to processes for preparing said catalyst, and to its use in converting hydrocarbon-containing feeds such as petroleum cuts and cuts from coal. In particular, the invention relates to hydrocracking hydrocarbon-containing feeds containing, for example, aromatic and/or olefinic and/or naphthenic and/or paraffinic compounds, said feeds possibly containing metals and/or nitrogen and/or oxygen and/or sulphur.
Hydrocracking is gaining in importance in refining as the need to convert heavy fractions into lighter fractions which can be upgraded as fuels increases. This results from the increasing demand for fuels. Such upgrading involves a relatively large reduction in the molecular weight of the heavy constituents which can, for example, be achieved through cracking reactions.
The catalytic hydrocracking process uses catalysts containing a hydrogenating, desulphurising and denitrogenating function provided by the active phase based on transition metals, and an acidic function, generally provided by the amorphous matrix or a zeolite, or a mixture thereof. A good hydrocracking catalyst will be constituted by a properly adjusted hydrogenating function and acidic function. Hydrocracking is used to treat feeds such as vacuum gas oils, atmospheric or vacuum residues, which may or may not be deasphalted. Hydrocracking can produce highly purified lighter cuts, i.e., with a low sulphur, nitrogen and metals content.
Increasing the activity and selectivity of hydrocracking catalysts is thus important. One means consists of acidifying the matrix without poisoning the activity of either the transition-metal based hydrogenating phase or the cracking activity of the zeolite-based acidic phase.
The catalyst of the invention comprises at least one beta zeolite which is at least partially in its hydrogen form. The term “beta zeolite” means zeolites with a BEA structure type as described in the “Atlas of Zeolite Structure Types”, W. M. Meier, D. H. Olson and Ch. Baerlocher, 4
th
revised edition, 1996. Elsevier.
Normally, beta zeolites with a total silicon/aluminium (Si/Al) atomic ratio of more than about 10 are preferably used, more preferably beta zeolites with an Si/Al ratio in the range 10 to 200, and still more preferably in the range 10 to 150. These beta zeolites with the Si/Al ratios defined above can be obtained through synthesis preferably or by using any post-synthesis dealumination technique known to the skilled person.
Preferred dealuminated bêta zeolites show atomic ratios Si/Al in the range 10 to 100, advantageously 20 to 70 and referably 25 to 55.
The first (preferred) method, direct acid attack, comprises a first calcining step carried out in dry air, at a temperature which is generally in the range 450° C. to 550° C. which eliminates the organic structuring agent present in the micropores of the zeolite, followed by a step in which the zeolite is treated with an aqueous solution of a mineral acid such as HNO
3
or HCl or an organic acid such as CH
3
CO
2
H. This latter step can be repeated as many times as is necessary to obtain the desired degree of dealumination. Between these two steps, one or more ion exchange steps can be carried out using at least one NH
4
NO
3
solution, to at least partially and preferably almost completely eliminate the alkaline cation, in particular sodium. Similarly, at the end of the direct acid attack dealumination step, one or more ion exchange steps may be carried out using at least one NH
4
NO
3
solution to eliminate residual alkaline cations, in particular sodium.
In order to obtain the desired Si/Al ratio, the operating conditions must be correctly selected; the most critical parameters in this respect are the temperature of the treatment with the aqueous acid solution, the concentration of the latter, its nature, the ratio between the quantity of acid solution and the mass of the treated zeolite, the treatment period and the number of treatments carried out.
Dealumination can also be achieved using chemical dealuminating agents such as (by way of non exhausting examples) silicon tetrachloride (SiCl
4
), ammonium hexafluorosilicate [(NH
4
)
2
SiF
6
], and ethylenediaminetetra-acetic acid (EDTA), including its mono and disodium forms. These reactants can be used in solution or in the gaseous phase, for example in the case of SiCl
4
.
The second method, heat treatment (in particular using steam, by steaming)+acid attack, comprises firstly calcining in dry air at a temperature which is generally in the range 450° C. to 550° C. to eliminate the organic structuring agent no occluded in the micropores of the zeolite. The solid obtained then undergoes one or more ion exchanges using at least one NH
4
NO
3
solution, to eliminate at least a portion, preferably practically all, of the alkaline cation, in particular sodium, present in the cationic position of the zeolite. The zeolite obtained then undergoes at least one framework dealumination cycle comprising at least one heat treatment which is optionally and preferably carried out in the presence of steam, at a temperature which is generally in the range 500° C. to 900° C., and followed by at least one acid attack using an aqueous solution of a mineral or organic acid as defined above. The conditions for calcining in the presence of steam (temperature, steam pressure and treatment period), also the post-calcining acid attack conditions (attack period, concentration of acid, nature of acid used and the ratio between the volume of the acid and the mass of zeolite) are adapted so as to obtain the desired level of dealumination. For the same reason, the number of heat treatment—acid attack cycles can be varied.
In a variation of this second method, the acid attack step, i.e., treatment using a solution of an acid, can be replaced by treatment with a solution of a chemical dealuminating compound such as those cited above, for example, namely silicon tetrachloride (SiCl
4
), ammonium hexafluorosilicate [(NH
4
)
2
SiF
6
], ethylenediaminetetra-acetic acid (EDTA), including its mono and disodium forms.
The framework dealumination cycle, comprising at least one heat treatment step, optionally and preferably carried out in the presence of steam, and at least one attack step carried out on the zeolite in an acid medium, can be repeated as often as is necessary to obtain the dealuminated zeolite having the desired characteristics. Similarly, following the heat treatment, optionally and preferably carried out in the presence of steam, a number of successive acid attacks can be carried out using different acid concentrations.
In a variation of this second calcining method, heat treatment of the zeolite containing the organic structuring agent can be carried out at a temperature which is generally in the range 500° C. to 850° C., optionally and preferably in the presence of steam. In this case, the steps of calcining the organic structuring agent and dealuminating the framework are carried out simultaneously. The zeolite is then optionally treated with at least one aqueous solution of a mineral acid (for example HNO
3
or HCl) or an organic acid (for
Benazzi Eric
George-Marchal Nathalie
Kasztelan Slavik
Ildebrando Christina
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Silverman Stanley S.
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