Chemistry: fischer-tropsch processes; or purification or recover – Group viii metal containing catalyst utilized for the...
Reexamination Certificate
1999-09-03
2001-05-22
Peselev, Elli (Department: 1623)
Chemistry: fischer-tropsch processes; or purification or recover
Group viii metal containing catalyst utilized for the...
C568S863000
Reexamination Certificate
active
06235797
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to catalysts having ruthenium disposed on a rutile support, catalytic systems containing such catalysts and at least one organic compound in water, and methods that use these catalysts in the hydrogenation of organic compounds in the aqueous phase.
BACKGROUND OF THE INVENTION
Hydrogenation reactions typically involve the reaction of hydrogen gas with an organic compound to produce a hydrogenated organic compound. Hydrogenation reactions are important in a variety of chemical processes including the production of fuels and the conversion of sugars to the corresponding polyalcohols. Despite generally favorable thermodynamics, there is a large kinetic barrier that slows the reaction of hydrogen gas with many unsaturated and heteronuclear organic compounds. To speed the reactions, it is necessary to add a catalyst, such as a metal. The metals that catalyze hydrogenations are usually expensive, and therefore it is common practice to increase the reactive surface area by distributing the metals over the surface of a support, thus forming a supported metal catalyst.
In addition to a supported metal catalyst, many commercial hydrogenations also require the use of organic solvents that dissolve the organic compounds and promote contact with the solid catalyst. Organic solvents, however, are often toxic and can present problems in storage, transportation, and disposal. Thus it would be desirable to avoid the use of organic solvents in hydrogenation reactions.
Instead of organic solvents, it would be desirable to use water to dissolve the organic compounds and promote contact with a solid catalyst. Furthermore, some organic compounds, such as sugars, are more soluble in water than in organic solvents. Thus, in many cases it would be advantageous to conduct hydrogenations in the presence of water, i.e., in the aqueous phase. On the other hand, many existing catalysts are not appropriate for aqueous phase reactions because they do not provide optimal conversion efficiency and yield. Moreover, in applications outside the laboratory, catalysts should remain active after weeks or months of processing; however, in aqueous phase processing conditions, the catalytic activity of existing catalysts becomes degraded or destroyed.
Some catalysts designed for aqueous phase hydrogenation reactions have been disclosed in prior patents. For example, Boyers in U.S. Pat. No. 2,868,847 discloses examples in which hydrogenations were carried out over catalysts of ruthenium on carbon or ruthenium on alumina. Arena, in U.S. Pat. Nos. 4,380,679, 3,380,680, 4,413,152, and 4,503,274, discloses aqueous phase hydrogenations of various carbohydrates over a catalyst supported on carbonaceous pyropolymer, alpha-alumina, titanated alumina, and gamma-alumina, respectively. In U.S. Pat. No. 4,487,980, Arena discloses aqueous phase hydrogenations and an aqueous phase hydrogenation catalyst comprising ruthenium and a titania-containing support. Arena analyzed leaching from a titania-bentonite material and studied the aqueous phase hydrogenation of glucose to sorbitol. Arena did not disclose the stability of the catalyst and did not disclose a rutile-containing catalyst.
Ruthenium on titania catalysts have long been known for catalyzing non-aqueous phase reactions. For example, Arcuri et al., in U.S. Pat. No. 4,567,205, disclose a ruthenium on titania catalyst for use in Fischer-Tropsch catalysis in which carbon monoxide and hydrogen gas are reacted to produce hydrocarbons. Arcuri et al. used rhenium in the catalyst to improve activity maintenance in Fischer-Tropsch conditions. Arcuri et al. state that the rhenium:ruthenium weight ratio ranges from about 10:1 to about 1:10. Arcuri et al. also state that the titania support is preferred to have a rutile:anatase ratio of at least 2:3 and found that under Fischer-Tropsch conditions, a rutile:anatase ratio of 2:1 demonstrated superior activity maintenance as compared to ratios of 1.2:1 and 30:1.
Ongoing research at Battelle Pacific Northwest Division has produced numerous discoveries in the area of low temperature catalytic gasification of wet industrial wastes. Elliott et al. have tested various types of supports in high pressure, hot water and found that supports such as &ggr;- and &dgr;-alumina and alumina-borate were unstable, but various other commercial supports such as titania and zirconia were reported to be relatively stable—see Low Temperature Catalytic Gasification of Wet Industrial Wastes, FY 1991-1992 and FY 1993-1994, pages B16-17 and 23, 25, respectively. Elliott et al., in U.S. Pat. No. 5,814,112, disclose a nickel/ruthenium catalyst on a porous support for aqueous phase reactions. It is suggested that the porous support could be alumina, titania in the rutile form, zirconia in the monoclinic form, granulated carbon, böhmite, or a commercial G1-80 catalyst.
Despite considerable efforts, there remains a need for aqueous phase hydrogenation catalysts that maintain catalytic activity for extended periods of time under hydrogenation conditions. There also exist needs for aqueous phase hydrogenation catalysts that exhibit excellent conversion efficiencies, high selectivities, operability at low temperatures, and/or high processing rates.
SUMMARY OF THE INVENTION
The present invention provides a catalyst that has an active metal on a titania support. The active metal includes ruthenium and the titania is more than 75% rutile as measured by x-ray diffraction. Additionally, the catalyst is essentially nickel- and rhenium-free.
In a second aspect, the invention provides a catalytic system that includes a catalyst, at least one organic compound, and water. The catalyst is essentially nickel-free and includes ruthenium on a titania support, where the titania is more than 75% rutile as measured by x-ray diffraction.
In another aspect, the invention provides a method of hydrogenating an organic compound in the aqueous phase in which a feedstock contacts hydrogen in a catalytic system. The feedstock comprises at least one organic compound in water.
It is an object of the invention to provide a hydrogenation catalyst that is stable under aqueous phase operating conditions. It is another object of the invention to provide for the hydrogenation of organic compounds. Another object of the invention is to produce a hydrogenated product stream with extremely low levels of dissolved metal atoms. It is a further object to provide a catalyst that is essentially without nickel. It is yet another object of the invention to provide a catalyst that is essentially without rhenium. Other objects of the invention include the provision of hydrogenation reactions that possess excellent conversion efficiencies, high yields, operability at low temperatures, and/or high processing rates.
Although titania can occur in amorphous, brookite, anatase and rutile crystal structures, we have discovered that rutile is superior to the other forms as a support for ruthenium-catalyzed hydrogenations. The ruthenium on rutile catalyst provides numerous advantages that could not have been predicted prior to the present invention. These advantages include: enhanced stability as demonstrated by maintenance of catalytic activity after extended operating times; high conversion percentages at high processing rates and/or low temperatures; and high yields of desired hydrogenated products. Moreover, these desirable properties can be achieved without the use of modifying metals such as nickel or rhenium.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a catalyst that has an active metal on a titania support. The active metal includes ruthenium and the titania is more than 75% rutile as measured by x-ray diffraction. Additionall
Elliot Douglas C.
Frye, Jr. John G.
Wang Yong
Werpy Todd A.
Battelle (Memorial Institute)
May Stephen R.
Peselev Elli
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