Catalyst comprising at least a hydrogenation metal component...

Details Catalyst comprising at least a hydrogenation metal component... Catalyst comprising at least a hydrogenation metal component...

1997-05-06

2002-01-01

Preisch, Nadine (Department: 1764)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Cracking

C208S108000, C208S109000, C208S111350, C208S111300, C208S137000, C208S138000, C208S112000, C502S084000, C502S074000, C502S080000

Reexamination Certificate

active

06334947

ABSTRACT:

The invention pertains to a catalyst at least comprising a hydrogenation metal component and a synthetic clay. Said catalyst is particularly suitable for hydroprocessing hydrocarbon feeds. The term “hydroprocessing” in this context encompasses all processes in which a hydrocarbon feed is reacted with hydrogen at elevated temperature and elevated pressure. These processes include hydrodesulphurisation, hydrodenitrogenation, hydrodemetallisation, hydrode-aromatisation, hydro-isomerisation, hydrodewaxing, hydrocracking, and hydrocracking under mild pressure conditions, which is commonly referred to as mild hydrocracking.
Clays are layered silicates, also known as phyllosilicates. They are composed of a stack of elemental clay platelets. The individual clay platelets are composed of a central layer of octahedrally coordinated metal ions interlinked by means of oxygen ions. On either side of this octahedral layer there is a layer of tetrahedrally coordinated metal ions, with oxygen ions serving to link the tetrahedrally coordinated metal ions both to one another and to the octahedral layer. In addition to oxygen atoms interlinking metal ions, the clay structure contains hydroxyl groups.
To have a neutral octahedral layer, the metal ions present in that layer will have to provide a total charge of 6+ for every three octahedral cavities. This can be achieved by filling two out of every three octahedral cavities with trivalent metal ions, e.g., aluminium ions, or by filling all octahedral cavities of each set of three with divalent metal ions, e.g., magnesium ions. This gives two types of octahedral layers, viz. trioctahedral layers, which have three (divalent) cation site occupancy, and dioctahedral layers, which have two (trivalent) cation site occupancy. In dioctahedral layers one third of the octahedral sites between the oxygen atoms remains unfilled.
A neutral tetrahedral layer requires that the tetrahedral cation have a tetravalent charge. In general, the cation will be Si
4+
.
When lower valency cations are substituted for higher valency cations in the clay platelet structure, the clay platelet is negatively charged. This phenomenon is known as isomorphous substitution. For instance, in the octahedral layer divalent metal ions such as magnesium, zinc or nickel may be substituted for trivalent metal ions such as aluminium. The clays formed in this fashion are called montmorillonites. Alternatively, in a trioctahedral layer monovalent metal ions such as lithium may be substituted for divalent metal ions, resulting in so-called hectorites. In the tetrahedral layer trivalent metal ions, e.g., aluminium atoms, may be substituted for the silicon atoms. In the case of a clay with a trioctahedral layer, such a substitution will give a saponite, for a clay with a dioctahedral layer the result will be a beidellite.
The negative charge generated by isomorphous substitution is counterbalanced by the incorporation of hydrated cations, also known as counter-ions, into the space between the clay platelets. Generally, these cations are incorporated in the hydrated form, causing the clay to swell. For this reason clays with negatively charged clay platelets are also known as swelling clays. It is because of this negative charge that swelling clays are advantageous for use in catalysts. For, they can act as solid acids.
The use of clays in hydroprocessing catalysts is known as such, e.g., from EP-A 0 246 906. In this publication hydroprocessing catalysts are described which contain a natural clay where hydrogenation metals have been substituted for the counter-ions.
GB 1 528 982 describes a hydroprocessing catalyst containing a Group VIB metal disulphide with a hexagonal crystal structure on a layered support, e.g., a clay.
However, the known clay-containing catalysts do not always provide satisfactory results when hydrocarbon feeds are reacted with hydrogen, int. al., because insufficient clay mineral is accessible to the feed and it is not possible to fully regulate the clays' properties.
The Catalyst According to the Invention
It has now been found that an exceptionally favourable hydroprocessing catalyst is obtained by the incorporation therein of a clay satisfying certain conditions with regard to the diameter and the degree of stacking of the clay platelets. The catalyst according to the invention at least comprises a hydrogenation metal component and a clay, with the average diameter of the clay platelets not exceeding 1 micron and the average degree of stacking of the clay platelets not exceeding 20 sheets per stack. The two parameters are easily determined by means of transmission electron microscopy. Furthermore, the clay platelets have to be negatively charged. Neutral clay platelets, i.e., clay platelets which have not been subject to isomorphous substitution, are catalytically inactive.
Because there are restrictions to the diameter and the degree of stacking of the clay platelets, their surface area is readily accessible to the feed, giving a very active catalyst.
The average diameter of the clay platelets is not more than 1 micron, and is preferably between 1 nm and 0.5 micron, more preferably in the range of 1 nm to 0.1 micron, most preferably in the range of 1 to 50 nm. The average degree of stacking of the clay platelets is not more than 20 platelets per stack, preferably not more than 10 platelets per stack, more preferably not more than 5 platelets per stack, and most preferably not more than 3 platelets per stack. The lower limit, needless to say, is constituted by unstacked clay platelets, which have a “degree of stacking” of 1. As regards isomorphous substitution, at least 0.1 atomic %, as compared with the neutral clay mineral of the cations, can be replaced by cations of a lower valency. Preferably, at least 1 atomic %, more preferably at least 5 atomic %, of the cations in the clay platelets is replaced by cations of a lower valency. In the octahedral layer, preferably not more than 50 atomic % of the metal ions is replaced by ions of a lower valency as compared with the neutral situation, more preferably not more than 30 atomic % is replaced. In the case of the tetrahedral layer, preferably not more than 30 atomic % of the tetravalent metal ions present is replaced by metal ions of a lower valency, more preferably not more than 15 atomic %. Isomorphous substitution may occur only in the octahedral layer, only in the tetrahedral layer, or in both layers. In this context the term isomorphous substitution also refers to the removal of cations without the incorporation into the lattice of replacement cations, by which vacancies are produced. It will be clear that this removal also generates negative charges.
The trivalent ions in the octahedral layer preferably are aluminium, chromium, cobalt (III), iron (III), manganese (III), titanium (III), gallium, vanadium, molybdenum, tungsten, indium, rhodium, and/or scandium. The divalent ions in the octahedral layer preferably are magnesium, zinc, nickel, cobalt (II), iron (II), manganese (II), copper (II) and/or beryllium, and the monovalent ions preferably are lithium ions.
The tetravalent ions in the tetrahedral layer preferably are silicon, titanium (IV), and/or germanium, for which may be substituted trivalent ions preferably selected from aluminium, borium, gallium, chromium, iron (III), cobalt (III), and/or manganese (III). A portion of the hydroxyl groups present in the clay platelets may be replaced by fluorine if so desired.
Clays suitable for use in the catalyst according to the invention include clays with a composition as given in the following table:
Octahedral
Tetrahedral
layer
layers
Al,
Mg
Si
Al,
Mg,
Si,
Al
Mg
Si,
Al
Al,
Ni
Si
Mg,
Li
Si
Mg,
Ni
Si,
Al
Al,
Mo
Si,
Al
Al,
Co
Si
Al,
Co
Si,
Al
Co
Si,
Al
Co,
Li
Si
Mg,
Co
Si,
Al
As was stated earlier, it is of vital importance to the catalyst according to the invention that the clay platelets be negatively charged. This can be effected simply by ensuring that metal ions of a lower valency than is required for the neutral state are incorporated into the oct

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