RU2010597C1 - Catalyst for deep oxidation of hydrocarbons - Google Patents

Abstract

FIELD: combustion of fuel. SUBSTANCE: highly active catalyst lights up catalytic heater in no more than 1 min. Operating catalytic heater produces no toxic compounds in discharged gases. Catalyst for deep oxidation of hydrocarbons contains cobalt, copper and chromium oxides with platinum added, applied to a fibrous, e. g. silicic, carrier in the form of a mat in the following ratio of components, wt. -% : copper oxide, 2-4; chromium oxide, 8-11; cobalt oxide, 4-8; platinum, 0.006-0.01; carrier, the balance. EFFECT: reduced lighting-up time of catalytic heater. 2 tbl

Description

 The invention relates to catalysts for the deep oxidation of gaseous fuels and can be used in catalytic heaters operating on a propane-butane mixture or other hydrocarbons, which are necessary in a number of sectors of the economy, as well as for heating industrial, domestic and residential premises.

 For the deep oxidation of hydrocarbons are various catalysts - metals, simple and complex oxide systems. Metal catalysts for the deep oxidation of hydrocarbons, as a rule, are platinum group metals [1] deposited on various supports: aluminum and silicon oxides, heat-resistant fibrous materials. It should be noted that in terms of activity, universality of action, which ensures reliability and completeness of oxidation, as well as a significantly lower ignition temperature, platinum catalysts are undoubtedly better. The disadvantages include instability to poisons, and most importantly, platinum is scarce and very expensive. Nevertheless, platinum or its analogues are included in the composition of the catalysts intended for use in domestic or residential premises, and its content is 0.05-7 wt. % [2-5].

 It is known that of the transition metal systems, the most active catalysts for deep oxidation are mixed oxide compounds of the spinel type (cobaltites, chromites, ferrites). Their main disadvantage is the high ignition temperature, which makes it impossible to use them in heating devices intended for domestic and residential premises.

 The most common methods for preparing catalysts is the coprecipitation of active components or their deposition on an inert carrier [6,7].

A known method in which the granules of aluminum oxide is impregnated with a solution of copper dichromate, followed by drying and calcination at 700 ^about [8]. The disadvantages of this method are not sufficiently strong adhesion of the particles of the active mass of the catalyst to the carrier and the inability to give the catalyst a certain shape, which excludes its use in catalytic heat sources.

 The closest in technical essence and the achieved result is a cobalt-chromium-iron catalyst supported on silica fiber for the deep oxidation of hydrocarbons [9].

The cobalt-chrome-iron oxide catalyst is prepared by a single impregnation of a silica support at room temperature with an aqueous solution containing salts of all the elements that make up the catalyst. Pre-determine the moisture capacity of the silica carrier per 1 g of the plate. A weighted amount of the plate is immersed in a solution, the amount of which is determined by the moisture capacity of this plate, containing the active components of the catalyst in amounts that provide the required composition of the catalyst. After soaking the total solution silica plate was dried at ¹¹⁰ ° C for 5-6 hours with rapid withdrawal of evolved water vapor. After drying, the catalyst is calcined at 550-600 ^C for 1 hour. With vigorous retraction degradation products in the purified stream of heated air.

Get a catalyst containing: chromium oxide, cobalt, iron, deposited on a silica carrier, respectively, in wt. %: Cr ₂ O ₃ 5-6; Co ₃ O ₄ 2-12; Fe ₂ O ₃ 5-15.

The disadvantages of this catalyst are:
a long ignition time of the catalyst, which is more than 10 minutes, that is, during this time, the conversion of hydrocarbon fuel is on average 50%, and this, in turn, does not allow the use of this catalyst in heaters for domestic and residential premises;
during its preparation, a significant amount of nitrogen oxides is released, emitted into the atmosphere. So, in the preparation of 1 kg of the finished catalyst, 155 l of gaseous nitrogen oxides, which are toxic products, are released.

 The aim of the invention is to increase the activity of the catalyst, as a result of which the ignition time should be no more than 1 min, as well as improving working conditions and environmental protection by eliminating toxic impurities in the exhaust gases.

 This goal is achieved in that the catalyst for the deep oxidation of hydrocarbons, including chromium and cobalt oxides on a fibrous carrier, additionally contains platinum and copper oxide in the following ratio of components, wt. %: chromium oxide 8-11; cobalt oxide 4-8; copper oxide 2-4; platinum 0.01; carrier rest.

The cobalt-copper-chromium oxide catalyst is prepared by impregnating once a single excess of the fibrous support at room temperature with an aqueous solution containing salts of copper, cobalt and chromium. To remove excess solution, the catalyst plate is squeezed using rollers. The catalyst was dried at 25 + 5 ^C for 8-12 h. By increasing the temperature of drying air and Organizations intense suction tough crust is formed on the catalyst surface. Next, on both surfaces of the catalyst applied irrigation solution of chloroplatinic acid and dried again at 25 + 5 ^C 4-6 h. The catalyst was then calcined at 550-600 ^C for 4 hours to form the mixed non-stoichiometric spinel cobalt chromite and copper chromite .

 The tests of the catalysts were carried out both in laboratory conditions at the test bench, and in real conditions during the operation of the catalyst in catalytic heaters of various designs. During the tests, the temperature of the onset of the reaction, the ignition time, the maximum temperature on the surface of the catalyst during operation of the heater, and the process of conversion of gaseous fuel were measured. The flue gases were periodically analyzed for carbon dioxide and carbon monoxide by chromatographic methods.

PRI me R 1. Mullite-siliceous felt in the form of a mat, a thickness of 15 mm and a mass of 80 g is impregnated at room temperature with 450 ml of a solution containing 17.6 g of basic carbonate, 4.5 g of basic carbon dioxide, chromium trioxide 25 g. The catalyst is drained and dried on rollers at a temperature of 25 + 5 ^{° C} for 12 hours. The catalyst was dried at applied irrigation 8 ml of a 1% solution of chloroplatinic acid. The catalyst was again dried and then calcined at 550 ^{° C} for 4 hours.

The resulting catalyst has a composition, wt. %: cobalt oxide 8; copper oxide 4; chromium oxide (Cr ₂ O ₃ ) 10; platinum 0.006, the rest is the carrier. According to x-ray phase analysis, the catalyst has the structure of a mixed cobaltchrome and copperchrome spinel.

PRI me R 2. Mats made of superthin glass fiber (MB-STB) are impregnated at room temperature with 400 ml of a solution containing 17.6 g of basic carbon dioxide, 4.5 basic carbon dioxide, 23 g of chromium trioxide. After impregnation, the catalyst plate is carefully squeezed out and dried at 25 + 5 ^о С for 8-12 hours. Next, 1.5 ml of a 1% solution of platinum chloride hydrochloric acid is applied to the irrigation catalyst and again dried at 25 + 5 ^о С, 4-6 h and calcined at 550 ^about 4 hours

 The resulting catalyst has the following composition, wt. %: chromium oxide 11; cobalt oxide 6; copper oxide 3, platinum 0.01, the rest of the media. According to x-ray phase analysis, the catalyst has a mixed spinel structure.

 PRI me R 3. Mats MB-STV, impregnated with a solution containing carbon dioxide 11.2 g of cobalt, 2.8 g of copper, 16 g of chromium oxide. 2 ml of a 1% solution of platinum chloride hydrochloric acid is applied by irrigation. The resulting catalyst has the following composition, wt. %: chromium oxide 8; cobalt oxide 4; copper oxide 2; platinum 0.008; the rest is media. The data of the catalysts are given in table. 1.

PRI me R 4 (for comparison, the known method). A catalyst sample was prepared in accordance with (9). A silica slab weighing 13.0 g is impregnated with 143 ml of an aqueous solution containing 5.57 g of cobalt nitrate, 7.26 g of iron nitrate and 5.32 g of chromium nitrate. The catalyst was then dried at ¹¹⁰ ° C for 5-6 hours and calcined at ⁶⁰⁰ ° C for 1 hour in a heated air stream (composition 1). The resulting catalyst contains, by weight. %: cobalt oxide 8.5; iron oxide 8.5; chromium oxide 6.0; the rest is silica carrier.

 PRI me R 5 (for comparison, a known method). A catalyst sample was prepared in accordance with (9). A silica board weighing 13.0 g is impregnated with 143 ml of an aqueous solution containing 7.86 g of cobalt nitrate, 4.27 g of iron nitrate, and 5.33 g of chromium nitrate. Then dried and calcined according to example 4. The composition of the obtained catalyst, wt. % cobalt oxide 12.2; iron oxide 5.0; chromium oxide 6.0; silica carrier rest (composition 2).

 The prepared catalysts were tested on a test bench during the oxidation of gaseous fuels. The results are presented in table. 2 for comparison with samples of known catalysts.

 (56) Trim D. L. Catalytic Combustion-Applied Catalysis, 1983, v. 7, p. 249-282.

 Patent 659005, Switzerland, cl. In 01 J 23/42, published. 1986.

 Patent N 2821510, USA, cl. In 01 J, published, 1958.

 PCT Application 83/01017, CL In 01 J 35/00, published. 1982.

 Patent 3956185, USA, 01 J 29/06, published. 1983.

 Kadenatsi B. M., Shibanova M. D. / In the book. "Deep catalytic oxidation of hydrocarbons", (series "Problems of Kinetics and Catalysis" v. 18), M.: Nauka, 1981, 200 pp.

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 USSR author's certificate N 533391, cl. B 01 J 37/00, publ. 1976.

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Claims (1)

A CATALYST FOR DEEP OXIDATION OF HYDROCARBONS, containing chromium and cobalt oxides on a fibrous, for example, silica carrier, characterized in that, in order to reduce the ignition time and improve working conditions and environmental protection, it additionally contains copper oxide and platinum in the following ratio of components, wt. %:
Chromium oxide 8 - 11
Cobalt oxide 4-8
Copper oxide 2 - 4
Platinum 0.006 - 0.01
Specified Media Else

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