Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2001-05-30
2003-08-26
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S180000, C502S182000, C502S185000, C502S305000, C502S339000, C502S345000, C502S527240
Reexamination Certificate
active
06610628
ABSTRACT:
BACKGROUND OF THE INVENTION
Industrial hydrogenation reactions are often performed by using finely divided powdered slurry catalysts in stirred-tank and reactors. These slurry phase reaction systems are inherently problematic in chemical process safety, operability and productivity. The finely divided, powdered catalysts are often pyrophoric and require extensive operator handling during reactor charging and filtration. By the nature of their heat cycles for start-up and shut-down, slurry systems promote co-product formation which can shorten catalyst life and lower yield to the desired product.
An option to the use of finely divided powder catalysts in stirred reactors has been the use of pelleted catalysts in fixed bed reactors. While this reactor technology does eliminate much of the handling and waste problems, a number of engineering challenges have not permitted the application of fixed bed reactor technology to the hydrogenation of many organic compounds. Controlling the overall temperature rise and temperature gradients in the reaction process has been one problem. A second problem is that in fixed bed packed reactors there is a significant pressure drop due to the high flow rates required for hydrogenation. A third problem is that liquid-gas distribution is problematic thus often leading to poor conversion and localized concentration gradients. A fourth problem is that the product water phase in a two liquid phase system tends to block access of the reactant to the active catalyst sites and thereby decrease the reaction rate or, in the alternative, result in inconsistent reaction rates.
Monolith catalytic reactors are an alternative to fixed bed reactors and have a number of advantages over conventional fixed bed reactors. These reactors have low pressure drop which allow them to be operated at higher gas and liquid velocities. These higher velocities of gas and liquids promote high mass transfer and mixing and the parallel channel design of a monolith inhibits the coalescence of the gas in the liquid phase.
Monolith catalytic reactor development has been an ongoing process in an effort to enhance catalytic activity and catalyst life. Exposure of the catalytic metal in the monolith catalytic reactor to the reactants is necessary to effect good reaction rates. However, efforts to enhance exposure of the catalytic metal often are at odds with enhancing adhesion of the metal to the monolith substrate. Embedding the catalytic metal in a coating applied to the surface of the monolith may result in greater adhesion of the catalytic metal but also reduces catalytic activity.
The following articles and patents are representative of catalytic processes employing monolith catalysts and processes in chemical reactions including the hydrogenation of nitroaromatics and other organic compounds.
Hatziantoniou, et al. in “The Segmented Two-Phase Flow Monolithic Catalyst Reactor. An Alternative for Liquid-Phase Hydrogenations”, Ind. Eng. Chem. Fundam., Vol. 23, No.1, 82-88 (1984) discloses the liquid phase hydrogenation of nitrobenzoic acid (NBA) to aminobenzoic acid (ABA) in the presence of a solid palladium monolithic catalyst. The monolithic catalyst consisted of a number of parallel plates separated from each other by corrugated planes forming a system of parallel channels having a cross sectional area of 1 mm
2
per channel. The composition of the monolith comprised a mixture of glass, silica, alumina, and minor amounts of other oxides reinforced by asbestos fibers with palladium metal incorporated into the monolith in an amount of 2.5% palladium by weight. The reactor system was operated as a simulated, isothermal batch process. Feed concentrations between 50 and 100 moles/m
3
were cycled through the reactor with less than 10% conversion per pass until the final conversion was between 50% and 98%.
Hatziantoniou, et al. in “Mass Transfer and Selectivity in Liquid-Phase Hydrogenation of Nitro Compounds in a Monolithic Catalyst Reactor with Segmented Gas-Liquid Flow”, Ind. Eng. Chem. Process Des. Dev., Vol. 25, No.4, 964-970 (1986) discloses the isothermal hydrogenation of nitrobenzene and m-nitrotoluene dissolved in ethanol using a monolithic support impregnated with palladium. The authors report that the activity of the catalyst is high and therefore mass-transfer is rate determining. Hydrogenation was carried out at 590 and 980 kPa at temperatures of 73 and 103° C. Again, less than 10% conversion per pass was achieved. Ethanol was used as a cosolvent to maintain one homogeneous phase.
U.S. Pat. No. 6,005,143 discloses a process for the adiabatic hydrogenation of dinitrotoluene in a monolith catalyst employing nickel and palladium as the catalytic metals. A single phase dinitrotoluene/water mixture in the absence of solvent is cycled through the monolith catalyst under plug flow conditions for producing toluenediamine.
U.S. Pat. No. 4,743,577 discloses metallic catalysts which are extended as thin surface layers upon a porous, sintered metal substrate for use in hydrogenation and decarbonylation reactions. In forming a monolith, a first active catalytic material, such as palladium, is extended as a thin metallic layer upon a surface of a second metal present in the form of porous, sintered substrate. The resulting catalyst is used for hydrogenation, deoxygenation and other chemical reactions. The monolithic metal catalyst incorporates catalytic materials, such as, palladium, nickel and rhodium, as well as platinum, copper, ruthenium, cobalt and mixtures. Support metals include titanium, zirconium, tungsten, chromium, nickel and alloys.
U.S. Pat. No. 5,250,490 discloses a catalyst made by an electrolysis process for use in a variety of chemical reactions such as hydrogenation, deamination, amination and so forth. The catalyst is comprised of a noble metal deposited, or fixed in place, on a base metal, the base metal being in form of sheets, wire gauze, spiral windings and so forth. The preferred base metal is steel which has a low surface area, e.g., less than 1 square meter per gram of material. Catalytic metals which can be used to form the catalysts include platinum, rhodium, ruthenium, palladium, iridium and the like.
EPO 0 233 642 discloses a process for the hydrogenation of organic compounds in the presence of a monolith-supported hydrogenation catalyst. A catalytic metal, e.g., Pd, Pt, Ni, or Cu is deposited or impregnated on or in the monolith support. A variety of organic compounds are suggested as being suited for use and these include olefins, nitroaromatics and fatty oils.
There is a report by Delft University, in Elsevier Science B.V., Preparation of Catalysts VII, p. 175-183 (1998) that discloses a carbon coated ceramic monolith where the carbon serves as a support for catalytic metals. Ceramic monolith substrates were dipped in furfuryl alcohol based polymer forming solutions and allowed to polymerize. After solidification the polymers were carbonized in flowing argon to temperatures of 550° C. followed by partial oxidation in 10% O
2
in argon at 350° C. The carbon coated monolith substrate typically had a surface area of 40-70 m
2
/gram.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to an improved process for the hydrogenation of an immiscible mixture of an organic reactant in water. The two phase immiscible mixture can result from the generation of water during the hydrogenation reaction itself or, by the addition of water to the reactant prior to contact with the catalyst or to the reactor. The improvement resides in effecting the hydrogenation of a two phase immiscible mixture of organic reactant in water in a monolith catalytic reactor comprised of a monolith support and a catalytic metal and having from 100 to 800 cells per square inch (cpi). This is accomplished by passing a two phase immiscible mixture of organic reactant in water through the reactor at a superficial velocity of from 0.1 to 2 m/second in the absence of a cosolvent for the two phase immiscible mixture.
The invention also relates to an improved monolith support comprised of a
Machado Reinaldo Mario
Nordquist Andrew Francis
Waller Francis Joseph
Wilhelm Frederick Carl
Air Products and Chemicals Inc.
Gourley Keith D.
Wood Elizabeth D.
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