Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,... – Using transition metal-containing catalyst
Reexamination Certificate
1999-08-11
2001-08-21
Yildirim, Bekir L. (Department: 1764)
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
Using transition metal-containing catalyst
C585S276000, C208S144000, C208S145000, C208S950000
Reexamination Certificate
active
06278034
ABSTRACT:
This invention relates to the hydrogenation of hydrocarbons, in particular long chain hydrocarbon. More particularly, the invention relates to a process for hydrogenating long chain hydrocarbon, and to a catalyst suitable for use in the process.
According to a first aspect of the invention, there is provided a process for hydrogenating long chain hydrocarbon, which process comprises
continuously feeding a feedstock comprising long chain hydrocarbon into a slurry bed comprising a slurry of catalyst particles in a slurrying liquid, with the slurry bed being contained in a reaction zone and the feedstock entering the reaction zone at a low level;
continuously feeding a hydrogenation component into the slurry bed, also at a low level;
allowing the hydrogenation component to react with the feedstock, thereby to hydrogenate the feedstock, as the feedstock and hydrogenation component pass upwardly through the slurry bed;
withdrawing hydrogenation long chain hydrocarbon from the reaction zone at a high level, as a hydrogenation product; and
withdrawing any excess hydrogenation component from the reaction zone at a high level.
By ‘long chain hydrocarbon’ is meant hydrocarbons which are in the liquid phase at the operating conditions of the reaction zone.
While the feedstock can, at least in principle, comprise any hydrogen deficient or unsaturated long chain hydrocarbon, the Applicant believes that it may, in particular, comprise a wax fraction. The wax fraction may, more particularly, be that obtained as a product when a syntheses gas is subjected to Fischer-Tropsch reaction conditions. Typically, such a wax fraction may comply with the following: hydrocarbon molecules containing more than 20 carbon atoms; and a congealing point exceeding 90° C.
The feedstock may be in the form of a liquid. In the case where the feedstock is a Fischer-Tropsch derived wax fraction which is normally solid or at least non-fluid at ambient temperature, the feedstock may be at an elevated temperature at which it is fluid. The feedstock may thus be at a temperature between 100° C. and 350° C.
The rate at which the feedstock is fed into the reaction zone will depend on the composition and colour of the feedstock, but may be such as to provide a weight hourly space velocity of at least 0.5, typically about 3.0.
The hydrogenation component is preferably in gaseous form, and may be a hydrogen gas stream or a gas stream rick in hydrogen. The gas stream may be fed into the reaction zone at such a rate that its superficial velocity through the slurry bed is at least 1 cm/s; however, the superficial gas velocity through the slurry bed is preferably at least 5 cm/s.
The gas stream may thus enter the reaction zone through a gas distributor, sparger pipes or the like located at said low level in the reaction zone, with the slurry bed located above and around the gas distributor. The feedstock may then enter the reaction zone in the slurry bed below or immediately above the gas distributor.
The slurrying liquid will, at the bottom of the slurry bed, comprise a mixture of unhydrogenation and hydrogenation long chain hydrocarbons, with the slurrying liquid composition varying as it passes up the slurry bed. Thus, at the point or zone where the hydrogenation product is withdrawn from the slurry bed; the slurrying liquid will comprise mainly hydrogenation long chain hydrocarbons.
The reaction zone may thus be provided by a slurry bed reactor with the gas distributor thus located in or near the bottom of the reactor. A hydrogen feed line will also lead into the bottom of the reactor, eg be connected to the distributor, as will a feedstock flow line. The reactor will then be operated so that a slurry bed/gas interface is located some distance from the top of the reactor, ie so that a gas head or vapour space is provided above the slurry bed. An excess hydrogen gas withdrawal line will then lead form a gas outlet at the top of the reactor so that it is in communication with the head space. A hydrogenation product withdrawal line will lead from the reactor at a level below the level of the interface.
The gas velocity in the vapour space between the slurry bed/gas interface and the gas outlet should be low enough to avoid significant entrainment of slurry or slurry components in the outlet gas. Typically, this can be equal to the superficial gas velocity at the top of the slurry bed, to avoid complicating the reactor design by having to adjust the reactor diameter above the top of the bed. A typical gas velocity in the vapour space is therefore of at least 5 cm/s.
The concentration of the catalyst particles in the slurry bed may be between 10 mass % and 50 mass %, based on the total slurry bed mass. The slurry bed may be maintained at a temperature between 180° C. and 300° C., while the reaction zone may be maintained at a pressure between 10 atmospheres and 50 atmospheres.
Separation of the hydrogenation product from the catalyst particles of the slurry bed can be effected either internally in the reactor or externally thereof, using any suitable particle separation system such as a decanter, hydrocyclone or filter.
Excess hydrogen withdrawn from the top of the reactor can naturally be recycled to the gas distributor. The excess hydrogen may then typically be cooled to below 70° C., recompressed, and reheated to above 100° C., prior to being reintroduced into the reactor.
The reactor walls may be heated by means of a steam jacket in order to control the reactor temperature. For large reactors, it is expected that steam pipes, located inside the reactor, may be used.
The catalyst particles may have a size distribution between 1 and 250 microns, preferably between 30 and 170 microns. The catalyst should preferably not degrade to smaller particle sizes to any significant extent over extended periods of time. For example, less than 10% of particles below 30 microns should preferably be produced during a three month period of operation of the reactor; some variations hereof may be acceptable depending on reactor design, product value, feedstock cost and the cost of catalyst replacement.
Preferably, the catalyst may be that obtained by
(i) subjecting a slurry, comprising a particulate alumina or silica carrier, a nickel compound as an active component and a solvent for the active component, to a sub-atmospheric pressure environment, thereby to impregnate the carrier with the active component;
(ii) drying the impregnated carrier in a sub-atmospheric pressure environment; and
(iii) calcining the dried impregnated carrier, thereby to obtain a hydrogenation catalyst suitable for use in the hydrogenation process.
Thus, according to a second aspect of the invention, there is provided a process for the preparation of a hydrogenation catalyst suitable for use in a hydrogenation reaction of long chain hydrocarbons, the process comprising
(i) subjecting a slurry, comprising a particulate alumina or silica carrier, a nickel compound as an active component and a solvent for the active component, to a sub-atmospheric pressure environment, thereby to impregnate the carrier with the active component;
(ii) drying the impregnated carrier in a sub-atmospheric pressure environment; and
(iii) calcining the dried impregnated carrier, thereby to obtain a hydrogenation catalyst suitable for use in a hydrogenation reaction of long chain hydrocarbons.
Still further, according to a third aspect of the invention, there is provided a process for the preparation of a hydrogenation catalyst suitable for use in a hydrogenation reaction of long chain hydrocarbons, the process comprising
(i) preparing a particulate alumina or silica carrier;
(ii) forming a slurry of the particulate alumina or silica carrier, a nickel compound as an active component and a solvent for the active component;
(iii) subjecting the slurry to a sub-atmospheric pressure environment, thereby to impregnate the carrier with the active component;
(iv) drying the impregnated carrier in a sub-atmospheric pressure environment; and
(v) calcining the dried impregnated carrier, thereby to obtain a h
Espinoza Rafael Luis
Harding Samantha
Labuschagne Johan
Steynberg André Peter
(Sasol Technology (Proprietary) Limited)
Ladas & Parry
Yildirim Bekir L.
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