Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Patent
1982-07-26
1985-01-01
Davis, Curtis R.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
502258, 502263, 502300, 502325, 502349, 502355, 502527, 423245, B01J 3500
Patent
active
044916400
DESCRIPTION:
BRIEF SUMMARY
This invention relates to catalysts for use in low-temperature catalytic combustion burners, a process for producing the same and such a burner having the catalyst.
Low-temperature catalytic combustion burners are so adapted that a combustible gas is fed, singly or as admixed with air, to a catalyst from behind and reacted with oxygen supplied to and spread over the front side of the catalyst upon coming into contact with the oxygen on the catalyst which has activity to effect complete oxidation, whereby the gas is burned with autogenous heat at a low temperature without flaming. Such burners are relatively free from fire hazards, are least likely to release harmful gases such as NOx and CO, radiates a large amount of heat relative to the fuel input, are uniform in the temperature of the combustion catalyst surface and permit stabilized combustion under low load. Because of these advantages, they are useful for domestic, commercial and industrial uses. However, conventional low-temperature catalytic combustion burners for burning town gas and like fuels containing methane have various problems in respect of combustion efficiency, the durability and cost of the catalyst, etc. and still remain to be improved for actual use, although those for burning LPG are generally satisfactory.
Accordingly the main object of the present invention is to provide a catalyst for combustion at low temperatures which is durable, economical and outstanding in combustion efficiency when used for burning methane-containing fuels such as town gas.
Other objects and features of the invention will become apparent from the following description.
The above objects can be fulfilled by a low-temperature combustion catalyst comprising a layer of an inorganic fiber having fine pores and rhodium deposited in the layer in an amount of 0.1 to 3% based on the weight of the layer.
Our research has revealed that when rhodium, one of the platinum group metals, is used as an active component of catalysts for combustion at low temperatures, the metal exhibits a behavior distinctly different from that of the other platinum group metals, e.g. platinum and palladium. The invention has been accomplished based on this finding.
For the catalysts of the type described, there is the need to use a carrier or support which retains the catalytically active metal effectively, gives a suitable shape and strength to the catalyst, is low in specific heat, permits smooth diffusion of gases and has high resistance to heat. The support to be used for the catalyst of this invention is a layer or low-density mat which is made of an inorganic fiber having fine pores. Useful inorganic fibers are those of polycrystalline metallic oxides. Examples of preferred fibers are alumina, zirconia, titania, thoria, alumina-silica and zirconia-silica fibers have a specific surface area of about 5 to 200 m.sup.2 /g, a pore volume of about 0.005 to 0.3 cm.sup.3 /g and a diameter of about 3 to 10 .mu.m. More specific examples of such fibers include an alumina fibers, "Saffil", of standard grade which is a commercial product of Imperial Chemical Industries Ltd. U.K. This fiber is a long fiber composed of at least 95% of intermediate Al.sub.2 O.sub.3 and less than 5% of SiO.sub.2 and containing a small amount of recrystallization preventing material. The fiber has a diameter of about 3 .mu.m, a specific surface area of about 150 m.sup.2 /g, a pore volume of about 0.2 cm.sup.3 /g, tensile strength of about 100 kg/mm.sup.2 and such high heat resistance that no change occurs in its porous structure even at 1000.degree. C. Because of its properties, the alumina fiber is usable as a catalyst support in the form of a mere layer or mat having a bulk density of about 0.02 to about 0.1 g/cm.sup.3 without the necessity of using any binder.
According to the present invention, it is essential to use rhodium as a catalytically active metal for the catalyst. Although platinum belongs to the same platinum group metals as rhodium, platinum, if used, acts to oxidize the sulfur in fuel gases to SO.sub.3
REFERENCES:
patent: 3198240 (1965-08-01), Keith et al.
patent: 3632709 (1972-01-01), Hayes et al.
patent: 3799796 (1974-03-01), Hunter
patent: 3843561 (1974-10-01), Sobel
patent: 3956185 (1976-05-01), Yagi et al.
patent: 3990995 (1976-11-01), McArthur
patent: 4111848 (1978-09-01), Torii et al.
patent: 4177168 (1979-12-01), Denny et al.
patent: 4183829 (1980-01-01), Adachi et al.
Anderson et al., "Catalytic Oxidation of Methane", Industrial and Engineering Chemistry, vol. 53, No. 10, Oct. 1961, pp. 809-812.
Radcliffe et al., "Diffusive Catalytic Combustors", Journal of the Institute of Fuel, Dec. 1975, pp. 208-214.
Chikazawa Akio
Noda Chikako
Okamura Setsuo
Sadamori Hiroki
Davis Curtis R.
Osaka Gas Company Limited
Prezlock Cynthia A.
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