Process for selective hydrogenation of unsaturated compounds

Details Process for selective hydrogenation of unsaturated compounds Process for selective hydrogenation of unsaturated compounds

1998-10-30

2001-07-03

Myers, Helane (Department: 1764)

Chemistry of hydrocarbon compounds

Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...

Hydrocarbon is contaminant in desired hydrocarbon

C585S259000, C585S260000, C585S261000, C585S262000, C585S500000, C585S501000, C208S134000, C208S138000

Reexamination Certificate

active

06255548

ABSTRACT:

The present invention relates to a novel process for selective hydrogenation of acetylenic or dienic compounds, in particular those contained in cuts from processes for cracking in the presence of a catalyst comprising at least one support, at least one metal from group VIII of the periodic table, and at least one additional element M selected from the group formed by germanium, tin, lead, rhenium, gallium, indium, gold, silver and thallium. The catalyst can also contain a further metallic element such as an alkali or alkaline-earth metal and/or a metalloid such as sulphur and/or a halogen or a halogen-containing compound.
Catalyst formulations used in processes for converting hydrocarbons have been the subject of a very large number of studies. Patents and publications which demonstrate that the addition of promoters to a base metal improves the quality of catalysts exist in large numbers.
For selective hydrogenation catalysts, catalysts comprising, in addition to a support, a metal such as palladium, nickel or platinum and at least one additional metal M (French patent FR-A-2 495 605) such as tin, germanium, lead, rhenium, gallium, indium, gold or silver have long been known. Such catalysts, known as bimetallic catalysts, perform better as regards activity and/or selectivity than that of catalysts containing only the principal metal (palladium, platinum or nickel).
Such elements are added in different forms such as mineral salts or organometallic compounds. The manner in which such modifiers are introduced is not unimportant as it dictates the properties of the catalyst to a great extent. Thus a metal M is advantageously introduced using an organometallic compound of that metal M. Such a technique for introducing a metal M has been described in the Applicant's U.S. Pat. No. 4,548,918. Metal M is introduced in the form of at least one organometallic compound selected from the group formed by complexes, in particular carbonyl, or polyketone complexes of metals M and metal hydrocarbyls of metal M such as alkyls, cycloalkyls, aryls, metal alkylaryls and metal arylalkyls.
Introducing additional metal M in the form of an organometallic compound leads to more effective catalysts but necessitates the use of an organic solvent. The impregnating solvent described in U.S. Pat. No. 4,548,918 is selected from the group formed by oxygen-containing organic solvents containing 2 to 8 carbon atoms per molecule, paraffin, naphthene or aromatic hydrocarbons essentially containing 6 to 15 carbon atoms per molecule, and halogen-containing oxygen-containing organic compounds containing 1 to 15 carbon atoms per molecule. Such solvents can be to used alone or mixed together.
In the present invention we have discovered that particularly effective catalysts can be prepared by introducing metal M in the form of an organometallic complex which is soluble in an aqueous solvent. This represents a considerable advance as regards ease of use during manufacture of the catalyst. Using large quantities of organic solvents has many disadvantages as regards safety (flammability, toxicity) and as regards costs.
The support for the catalyst of the invention comprises at least one refractory oxide which is generally selected from oxides of metals from groups IIA, IIIA, IIIB, IVA or IVB of the periodic table such as oxides of magnesium, aluminium, silicon, titanium, zirconium or thorium, used alone or mixed together or mixed with oxides of other elements from the periodic table. Charcoal can also be used.
Alumina constitutes the preferred support, the specific surface area of which is advantageously in the range 5 to 400 m
2
per gram, preferably in the range 5 to 100 m
2
per gram.
In addition to a support, the catalyst of the invention includes:
a) at least one group VIII metal selected from nickel, palladium, platinum, rhodium, ruthenium and iridium. Palladium, nickel and platinum are preferred.
The percentage by weight is in the range 0.01% to 50%, preferably in the range 0.05% to 1% if the metal is a noble metal and in the range 5% to 30% if the metal is nickel.
b) at least one additional element M selected from the group formed by germanium, tin, lead, rhenium, gallium, indium, silver, gold and thallium. Tin, germanium, silver and gold are preferred elements. The percentage by weight is in the range 0.01% to 10%, preferably in the range 0.02% to 5%. In some cases, at least two of the metals from this group can be used at once.
The catalyst can also contain 0.1% to 3% by weight of an alkali or alkaline-earth metal such as potassium or sodium and/or 0.01 % to 2% by weight of an element such as sulphur.
The catalyst can be prepared using different procedures for impregnating the support and the invention is not limited to any specific impregnation procedure. When several solutions are used, intermediate drying and/or calcining steps can be carried out.
The additional element M can be introduced during production of the support. One method, for example, consists of blending the moist powdered support with catalyst precursors and then forming and drying.
The group VIII metal, additional metal M, optional alkali or alkaline-earth metal, optional halogen or halogen-containing compound, and optional metalloid, can be introduced simultaneously or successively. In accordance with the invention, the characteristic feature of contact with the organometallic element M is that it is introduced in an aqueous solvent.
The precursor of element M can be selected from the group formed by halogen-containing compounds, hydroxides, oxides, carbonates and carboxylates of organometallic compounds of element M, this list not being limiting in nature. These compounds comprise at least one carbon-M bond. The precursor for element M can also be selected from compounds with general formula (R
1
)
x
M(R
2
)
y
where x+y=the valency of metal M and where R
1
is selected from the group formed by alkyl, cycloalkyl, aryl, alkylaryl and arylalkyl functions, and R
2
is a function with formula C
a
H
b
R′
c
, where R′ represents a hydroxide, carboxylate, PO
3
H or SO
3
H function.
In one preparation technique in accordance with the invention, the catalyst is obtained by impregnating the support using an aqueous or organic solution of at least one group VIII metal compound, the volume of the solution preferably being in excess with respect to the retention volume of the support, or equal to that volume. The impregnated support is then filtered, optionally washed with distilled water, then dried and cacined in air, normally between 110° C. and about 500° C., then reduced in hydrogen at a temperature which is normally in the range about 20° C. to about 600° C., preferably between about 50° C. and about 450° C. The product obtained is then impregnated with an aqueous solution of a compound of tin, germanium, lead, rhenium, gallium, indium, gold, silver or thallium. Particularly advantageously, an aqueous solution of a carboxylate compound of tin is used, for example tributyl tin acetate.
After leaving the support impregnated with the group VIII metal in contact with the solution containing at least one compound of element M for several hours, the product is filtered, optionally washed with water, then dried. The operation is normally completed by calcining between 300° C. and 600° C., preferably in a stream of fair for several hours.
In a further technique in accordance with the invention, the catalyst is obtained by impregnating using an aqueous solution of at least one compound of said metal M, the volume of the solution preferably being equal to the retention volume of the support, more preferably in excess with respect to that volume. Particularly advantageously, an aqueous solution of a tin carboxylate compound is used. After leaving the solid in contact with the impregnating solution for several hours, the product is then dried. The final step is usually calcining between 300° C. and 600° C., preferably in a stream of air for several hours. The solid obtained is then impregnated using an aqueous or organic solutio

Affiliated with

Also associated with

Rating

Process for selective hydrogenation of unsaturated compounds does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for selective hydrogenation of unsaturated compounds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for selective hydrogenation of unsaturated compounds will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2518969