Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
2000-05-23
2003-04-15
Dunn, Tom (Department: 1725)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S063000, C502S064000, C502S073000, C502S077000, C502S177000, C502S200000, C502S242000, C502S247000, C502S258000, C502S260000, C502S325000, C502S332000, C502S338000, C502S349000, C502S350000, C502S351000, C502S353000, C502S354000, C502S355000
Reexamination Certificate
active
06548440
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention (Technical Field)
The present invention relates to catalysts in mesoporous structures.
2. Background Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
The following references discuss silica and/or catalyst chemistry: “The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties, and Biochemistry,” R. K. Iler, Wiley, New York, 1979; “Attrition-Resistant Porous Particles Produced by Spray-Drying,” H. E. Bergna, Characterization and Catalyst Development: An Interactive Approach, American Chemical Society, 1989, 55-64; “Ordered Mesoporous Molecular-Sieves Synthesized by a Liquid-Crystal Template Mechanism,” Kresge, et al.,
Nature
, 1996, vol. 359, 710; “Activation of Precipitated Iron Fischer-Tropsch Catalysts,” Shroff, et al.,
J. Catalysis
, 1995, vol. 156, 185; “Mesoporous Silica Synthesized by Solvent Evaporation: Spun Fibers and Spray-Dried Hollow Sphere,” Bruinsma, et al.,
Chem. Mater
., 1997, vol. 9, 2507; “Aerosol-Assisted Self-Assembly of Mesostructured Spherical Nanoparticles,” Lu, et al.,
Nature
, 1999, vol. 398, 223; and “Measuring the Strength of Slurry Phase Heterogeneous Catalysts,” Pham, et al., Powder Technol., 1999, vol. 103, 95.
The present invention pertains to, for example, a slurry phase Fischer-Tropsch (F-T) synthesis, a process used to convert energy reserves of coal and natural gas into liquid transportation fuels. At present, F-T synthesis is being practiced in South Africa for converting coal-derived syngas (CO+H
2
) into hydrocarbon waxes which are subsequently processed to the desired product slate.
CO+2H
2
→—CH
2
—+H
2
O
The preferred reactor type for F-T synthesis is a slurry phase bubble column reactor (SBCR) for F-T synthesis, which provides improved heat and mass transfer and operational simplicity in terms of catalyst loading and discharge. The catalyst commonly used for F-T synthesis is iron or cobalt. A potential disadvantage in using a SBCR involves the attrition of catalysts. Attrition becomes a problem with the F-T process when heavy waxy products are produced, and separation becomes difficult between the wax and nano-sized catalyst particles. The filter system can become plugged by the nano-particles, slowing down the recovery of liquid reaction products. Development of attrition-resistant iron catalysts is an urgent need for catalytic processes that operate in a liquid phase, and where separation of the catalyst from viscous liquid products is required. Several approaches have been proposed for the preparation of attrition-resistant catalytic materials.
U.S. Pat. No. 4,677,084 (“'084 patent”) discloses a process for making attrition-resistant catalysts, catalyst precursors and catalyst supports. The slurry consists of a catalyst material in an aqueous silicic acid solution that is spray-dried to form porous microspheres, having diameters ranging from 30 microns to 300 microns (1 micron equals 1×10
−6
meters). According to the '084 patent, the relative amounts of particles and silicic acid are chosen so that the weight of the silica formed ranges from 3% to 15% of the total weight of particles and silica. The '084 patent further states that the spray-dried microspheres are calcined to sinter and generate the catalyst. A calcination temperature is used that is below a temperature that is deleterious to the catalyst. The '084 patent discloses attrition resistance measurements of the catalyst material, measured using a device where the catalyst is exposed to a high velocity gas jet.
A reference authored by H. Bergna that appears in Proc. Of the American Chemical Society symposium on Characterization and Catalyst Development, 1989, p. 55, (“Bergna reference”) discloses embedding of catalyst particles in a continuous framework or skeleton of a hard and relatively inert material to enhance attrition resistance. The approach of the Bergna reference requires that the fraction of the hard phase volume approach 50% to form an attrition-resistant continuous framework within the grain pores. The Bergna reference also discloses use of sub-colloidal or very small colloidal particles capable of coalescing or sintering to form a hard eggshell thereby conferring a degree of attrition resistance with smaller amounts (10%) of a hard phase (silica). In this particular case, the silica must be distributed on the periphery of the particles, which is achieved by ensuring the following two conditions: (i) that the silica does not agglomerate during spray drying and (ii) that the silica particles migrate easily to the surface.
U.S. Pat. No. 5,221,648 discloses a process for making highly mesoporous catalytic cracking catalysts, particularly catalysts useful in fluidized catalytic cracking operations. Attrition resistance of these catalysts is measured in terms of the Davison Index, which is well known to practitioners in the field of catalysis.
U.S. Pat. No. 5,352,645 (“'645 patent”) discloses a process for making relatively strong, non-agglomerated porous uniform silica microspheres ranging in size from 1.0 microns to 50 microns. According to the '645 patent, the microspheres are useful as catalytic supports in fluid bed and slurry applications, particularly in the catalytic process for the direct synthesis of hydrogen peroxide. The '645 patent also discloses use of an aqueous sol of colloidal silica that is mixed with a soluble additive selected from ammonium citrate or urea, and subsequently spray-dried to form silica microspheres. The spray-dried powder is calcined to remove any organic residues and sintering of the primary particles is performed to develop strength and porosity. The '645 patent discloses an attrition test that is performed by vibrating a mixture of the material in question and a granular alumina grinding medium in a heavy duty orbital sander. The particle size distribution of the material, separated from the grinding medium, is then analyzed using a Microtrac Model 158705 Analyzer, a typical particle size analyzer known in the art of particle size analysis.
U.S. Pat. No. 4,572,439 discloses a process for providing a rapid treatment for materials to be used in catalytic processes. Acoustical energy is applied to a slurry consisting of the material in question. After separating the aftrition-resistant particles from the liquid medium, the frangible particles are disintegrated to a fine powder and are separated from the liquid by filtration. The fines are agglomerated to suitably sized particles, and recycled to be slurried with the untreated material to be subjected to the attrition treatment.
U.S. Pat. No. 5,442,012 discloses a process for making encapsulated micro-agglomerated core/shell additives for PVC blends. A first core/shell impact modifier and a second core/shell processing aid are prepared separately by emulsion polymerization. The polymer particles are then admixed in emulsion form. The core/intermediate shell polymer particles are agglomerated, followed by sequential emulsion polymerization to form an encapsulating shell of hard polymer. This final shell can encapsulate more than one particle.
U.S. Pat. No. 5,633,217 discloses a process for making a high strength catalyst, catalyst support or adsorber, which makes use of silicone resin as an inorganic binder precursor dissolved in a cost-effective, non-flammable solvent.
The methods and materials disclosed and/or proposed in the aforementioned references for preparing attrition resistant catalysts fall short for preparing catalysts that are subject to phase transformations during use. For example, as disclosed in the Shroff et al.,
J. Catal
.,
Datye Abhaya K.
Pham Hien N.
Dunn Tom
Ildebrando Christina
Myers Jeffrey D.
Science & Technology Corporation @ UNM
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