Catalyst and process for purifying streams of materials

Details Catalyst and process for purifying streams of materials Catalyst and process for purifying streams of materials

2000-11-30

2001-08-21

Griffin, Walter D. (Department: 1764)

Chemistry of hydrocarbon compounds

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

Hydrocarbon is contaminant in desired hydrocarbon

C585S260000, C585S259000, C585S258000, C208S301000, C208S302000

Reexamination Certificate

active

06278033

ABSTRACT:

The present invention relates to a catalyst and a process for removing alkynes, dienes, monounsaturated hydrocarbons and/or oxygen from streams of materials.
In many different chemical processes, a stream of materials is reacted over one or more catalysts to produce reaction products. An example of such a process is the polymerization of olefins such as ethylene or propylene over metallocene catalysts to give the corresponding polyolefin.
The catalysts used in such processes are in most cases sensitive to certain impurities, known as catalyst poisons which if they come into contact with the catalyst in excessive quantities adversely affect its properties such as activity, selectivity or operating life. In general, active centers of the catalyst are occupied by the catalyst poison and are thus no longer available for catalyzing the desired reaction. When using catalysts, care therefore has to be taken that the feed streams with which the catalysts are brought into contact do not carry any catalyst poisons or at most that amount of catalyst poisons which, at an economically justifiable outlay for the removal of catalyst poisons, makes it possible for the catalyst to be operated economically satisfactorily in respect of selectivity, activity and operating life. Known catalyst poisons for many metallic catalysts are, for example, sulfur, arsenic and antimony.
Some impurities which are present in feed streams do not permanently damage the catalyst used but lead to undesirable secondary reactions and thus reduce, for example, the product quality. An example of such impurities are alkynes in olefins in metallocene-catalyzed olefin polymerization which adversely affect the important product properties such as molecular weight distribution, the stereospecificity of the polymerization or the stability of the polymer products. Such problems can of course also occur in uncatalyzed reactions.
As a rule, therefore, a feed stream goes through a purification process before being used in a reaction in order to remove impurities which would cause problems in the reaction concerned. Numerous purification processes of this type are known, for example scrubbing with various solvents, processes for adsorption of impurities on adsorbents such as zeolites or activated carbon, or processes in which undesirable impurities are removed from a stream by means of membranes.
For example, U.S. Pat. No. 4,861,939 teaches a process for removing arsenic from naphtha, in which the naphtha is largely freed of arsenic-containing compounds by contact with an adsorbent comprising nickel oxide and nickel.
Processes in which catalysts are used to purify streams of materials are rarer and are usually restricted to the removal of a few specific impurities in specific streams. The hydrogenative desulfurization of hydrocarbons over CoO/MoO
3
— or NiO/MoO
3
catalysts at from 350 to 450° C. and subsequent absorption of the hydrogen sulfide formed, the high- or low-temperature reaction of carbon monoxide with water over FeO/Cr
2
O
3
— or CoO/MoO
3
catalysts to form carbon dioxide and hydrogen and the methanization of CO and CO
2
using hydrogen over nickel catalysts are the best known processes and are general text book knowledge.
Oil & Gas Journal, October 1994 issue, pages 50 to 55, describes the “Triple P” or “Propylene Polishing Process” of Fina Research FA, Feluy, Belgium. This process is used to remove sulfur-containing compounds, arsine and stibine, oxygen, CO and CO
2
as well as hydrogen from propylene in order to produce highly pure propylene for polymerization. The process utilizes a specific adsorbent which is not disclosed in detail for the adsorbtive removal or all impurities apart from hydrogen; this adsorbent additionally acts as catalyst for the hydrogenation of propene with hydrogen and thus removes the hydrogen catalytically.
U.S. Pat. No. 3,420,618 teaches a process for removing acetylene, ethylene and oxygen from a synthesis gas stream by hydrogenation over a catalyst comprising palladium on an aluminum oxide support.
In a paper presented by D. J. Artrip, C. Herion and R. Meissner at the “MetCon '93”, session four, May 27, 1993, in Houston, Tex., USA, a four-stage process for removing various impurities from olefin streams for polymerization reactions was disclosed. In this process, arsenic- and sulfur-containing compounds are adsorbed on an adsorbent comprising copper oxide and zinc oxide in a first step. In a second step, acetylene and dienes are hydrogenated to olefins over a palladium-containing catalyst after addition of an amount of hydrogen sufficient to hydrogenate them. In the third process step, oxygen present is removed over a metallic copper catalyst. In the fourth and last process step, residual carbon monoxide which is still present is converted into carbon dioxide over a copper oxide catalyst and any remaining hydrogen is likewise oxidized to water.
The patent application DE 19710762.1 (equivalent: PCT EP98/01469) teaches a process for purifying streams of materials in not more than three process steps, in which a palladium- and silver-containing catalyst on an SiO
2
-containing catalyst support is used in the first purification stage to remove alkynes, dienes, monounsaturated hydrocarbons and/or oxygen from streams of materials.
DE-A 31 19 850 teaches the use of a catalyst comprising from 0.05 to 0.5% by weight of palladium and from 0.05 to 1% by weight of silver on a silicon dioxide support having a BET surface area of from 10 to 200 m
2
/g for the selective hydrogenation of butadiene in a C
4
fraction. Specific embodiments of this catalyst are those having a weight ratio of silver to palladium of from 0.7:1 to 3:1 and from 1:1 to 2.5:1.
JP-A 60-248237 discloses a process for producing a catalyst support having a high proportion of macropores. EP-A 653 243 teaches a process for producing catalysts whose active composition is essentially present in mesopores and macropores.
In view of the great importance of purified streams of materials in industrial chemistry, there is still a need for new and improved gas purification processes.
It is an object of the present invention to find a catalyst and a purification process by means of which alkynes, dienes, monounsaturated hydrocarbons and/or oxygen can be removed from streams of materials in a simple manner without having to accept the disadvantages of the known catalysts and processes. It is a particular object of the present invention to find a catalyst which is largely resistant to sulfur-, arsenic- and/or antimony-containing catalyst poisons and a process by means of which alkynes, dienes, monounsaturated hydrocarbons and/or oxygen can be removed in a simple manner from streams contaminated with sulfur-, arsenic- and/or antimony-containing catalyst poisons.
We have found that this object is achieved by a catalyst comprising, in its active composition, from 0.05 to 1.0% by weight of at least one metal or compound of a metal of the 10th group of the Periodic Table of the Elements and from 0.05 to 1.0% by weight of at least one metal or compound of a metal of the 11th group of the Periodic Table of the Elements, with the weight ratio of the metal of the 11th group to the metal of the 10th group being from 0.95 to 1.05, and, as support, an SiO
2
-containing catalyst support having a BET surface area of from 2 to 400 m
2
/g, wherein at least 20% of the total pore volume of the catalyst is made up by pores having a diameter greater than 100 nanometers.
Furthermore, we have found a process for removing alkynes, dienes, monounsaturated hydrocarbons and/or oxygen from streams of materials by hydrogenation, which comprises reacting the stream comprising alkynes, dienes, monounsaturated hydrocarbons and/or oxygen with hydrogen in the presence of the catalyst of the present invention.
The catalyst of the present invention displays, in particular, a very high tolerance to sulfur-, arsenic- and/or antimony-containing catalyst poisons in the feed, which makes it possible for it to be used in an economically satisfactory manner in a process for t

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