Catalyst comprising a phyllosilicate containing boron and/or...

Details Catalyst comprising a phyllosilicate containing boron and/or... Catalyst comprising a phyllosilicate containing boron and/or...

2001-05-08

2003-03-04

Dunn, Tom (Department: 1725)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Cracking

C208S110000, C208S111010, C208S111350

Reexamination Certificate

active

06527945

ABSTRACT:

The present invention relates to a catalyst comprising at least one metal selected from metals from group VIB and/or 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), associated with a support comprising at least one porous amorphous or low crystallinity oxide type matrix and at least one clay selected from the group formed by 2:1 octahedral phyllosilicates and trioctahedral 2:1 phyllosilicates. The catalyst support comprises at least one promoter element which is boron and/or silicon, optionally phosphorous, optionally at least one group VIIA element (group 17, the halogens), in particular fluorine, and optionally at least one group VIIB element.
The present invention also relates to processes for preparing said catalyst, and to its use for hydrocracking hydrocarbon-containing feeds such as petroleum cuts and cuts from coal. The feeds contain 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 invention thus relates to a catalyst for hydrocracking hydrocarbon-containing feeds. The catalyst contains at least one metal selected from group VIB and group VIII of the periodic table. The catalyst also comprises at least one clay selected from the group formed by dioctahedral 2:1 phyllosilicates and trioctahedral 2:1 phyllosilicates such as kaolinite, antigorite, chrysotile, montmorillonite, beidellite, vermiculite, talc, hectorite, saponite, or laponite. The catalyst preferably contains a dioctahedral 2:1 phyllosilicate synthesised in a fluoride medium and optionally bridged, said phyllosilicate preferably having a large interplanar spacing. The catalyst also comprises at least one amorphous or low crystallinity matrix acting as a binder. The catalyst is characterized in that it also comprises boron and/or silicon, optionally phosphorous, optionally at least one group VIIA element, preferably fluorine, and optionally at least one group VIIB element, for example manganese, technetium or rhenium.
The catalyst has a higher hydrocracking activity than that of prior art catalytic formulae based on clay. Without wishing to be bound to a particular theory, it appears that this particularly high activity of the catalysts of the present invention is due to the acidity of the catalyst being reinforced by the presence of boron and/or silicon, in particular on the matrix, which causes an improvement in the hydrocracking properties compared with catalysts in routine use.
More precisely, the present invention provides a catalyst comprising at least one dioctahedral 2:1 phyllosilicate, which is optionally bridged. When it is bridged, the interplanar spacing is at least 2.0×10
−9
m and comprises struts based on at least one compound selected from the group formed by SiO
2
, Al
2
O
3
, TiO
2
, ZrO
2
and V
2
O
3
, or any combination thereof.
The interplanar spacing d
001
of the dioctahedral 2:1 phyllosilicates of the invention (preferably previously prepared in a fluoride medium in the presence of HF acid and/or another source of fluoride ions) is preferably at least 2.0×10
−9
m, more preferably at least 2.65×10
−9
m, more preferably more than 2.8×10
−9
m and still more preferably still at least 3.3×10
−9
m, and generally 6.0×10
−9
m or less, preferably 5.0×10
−9
m. The interplanar spacing, represented by d
001
, represents the sum of the thickness of a sheet and the space between the sheets. This value can be directly obtained using a conventional orientated powder X ray diffraction method.
Dioctahedral 2:1 phyllosilicates are minerals which are formed by layering elementary sheets. Although the chemical bonds between the elements of the phyllosilicate structure are ionocovalent, they will be assumed to be ionic, to simplify the description.
From a representation where the O
2−
ions are in a plane in contact with each other, it is possible to produce a plane with a hexagonal cavity, termed the hexagonal plane, by withdrawing alternate O
2−
ions from a row of two O
2−
ions.
The structure of a dioctahedral 2:1 phyllosilicate can be simply represented by arrangements of hexagonal planes of O
2−
ions and compact planes of O
2−
and OH ions. The OH ions fill the cavities in the hexagonal planes of O
2−
ions.
Superimposition of two compact planes sandwiched by hexagonal planes defines an octahedral layer (O) between two tetrahedral layers (T) giving the sheet denomination TOT.
Such an arrangement, also termed 2:1, defines a plane of octahedral cavities located in the octahedral layer between two planes of tetrahedral cavities, one in each tetrahedral layer. Each tetrahedron has one O
2−
ion in common with the octahedral layer and each of the three other O
2−
ions is shared with another tetrahedron in the same tetrahedral layer.
The crystalline lattice is thus constituted by 6 octahedral cavities each having 4 tetrahedral cavities either side. In the case of a phyllite constituted by the elements Si, Al, O, H, such an arrangement corresponds to the ideal formula Si
g
(Al
4
•
2
)O
20
(OH)
4
. The tetrahedral cavities contain the element silicon, and the octahedral cavities contain the element aluminium but in this case one octahedral cavity in three is empty (•). Such an assembly is electrically neutral. Usually, the half-cell is used, with formula
Si
4
(Al
2
•)O
10
(OH)
2
The tetrahedral element silicon can be substituted by trivalent elements such as aluminium or gallium or iron (Fe
3+
). Similarly, the octahedral element aluminium can be substituted by:
the trivalent elements cited above, or a mixture of those elements;
divalent elements, for example magnesium.
These substitutions result in an overall negative charge in the structure. This necessitates the existence of exchangeable compensating cations located in the space between the sheets. The thickness of the space between the sheets depends on the nature of the compensating cations and their hydration. This space is also capable of accepting other chemical species such as water, amines, salts, alcohols, or bases.
The existence of —OH groups causes thermal instability due to a dehydroxylation reaction with equation:
2−OH→-O-+H
2
O.
In this respect, and without wishing to be bound to a particular theory, it can be considered that the introduction of the element fluorine into the structure during synthesis in place of the O—H groups produces phyllosilicates with greatly improved thermal stability.
The preferred phyllosilicates of the invention are dioctahedral 2:1 phyllosilicates the charac

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