RU1796243C - Method for production of palladium catalyst on activated carbon for low-temperature oxidation of hydrogen and carbon monoxide - Google Patents

Abstract

Usage: the product is a palladium catalyst on activated carbon (CT) is obtained by impregnating hydroxylated activated carbon with a solution of the palladium dichlorobisdimethyl-formamide complex, reduction by adding hydrazine chloride to the reaction mixture during heating, washing and drying. Characteristic CT: increased activity. 1 tab.

Description

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The invention relates to the preparation of metal catalysts for the low temperature oxidation of hydrogen and carbon monoxide.

The widespread use of palladium catalysts for the purification of air flows and liquid-phase systems poses the problem of both increasing their specific activity and improving cooking methods. One way is to increase the chemical uniformity of the surface of the carrier to create conditions for uniform distribution of the active metal over its surface.

Section 3 describes the use of catalysts APK-2 and PTP-0.5 for air purification from impurities of hydrogen, deuterium and tritium. At a concentration of hydrogen in a mixture with air of 0.15%, the maximum degree

Oxidation of 98% at APC-2 was achieved at 90 ° C, and at PTP-0.5, 92% at 110 ° C. The authors of the article recommend these catalysts with 1 and 2% palladium content, respectively, for purification from hydrogen impurities at 80-100 ° С, however, all these catalysts do not oxidize hydrogen, which is present as an impurity in air or oxygen when its content is less than 1 vol.% and room temperature.

In the article, the authors propose the use of a carbon-containing support impregnation to prepare the catalyst to saturate its surface with an active metal compound overnight at room temperature from a solution of tetrachloropalladium acid in the presence of an excess of free hydrochloric acid. The recovery was carried out in a stream of hydrogen,

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saturated with formaldehyde vapor. The disadvantages of the aforementioned method include the following: the use of hydrochloric acid for the preparation of an impregnating solution, which is undesirable because of the possibility of interaction with the padding material and the corrosion of the equipment; Complicated reduction conditions using hydrogen saturated with formaldehyde vapor at a temperature of 100-110 ° C; the relative duration of the impregnation processes (day) and recovery (5-6 hours).

The catalysts obtained according to the described method oxidize hydrogen at room temperature, but with a palladium content of 7-10% and a hydrogen concentration in air of 4%, which indicates insufficient catalyst activity, v;

Closest to the technical nature of the invention is the application method described in the French patent. ; : In order to achieve uniform distribution of the active metal over the surface of the support, the authors introduce the active metal into the pores of the support in the form of a suspension containing solid oxides, hydroxides and basic metal salts, the alkaline medium necessary to obtain a solid phase is provided by incorporation of the suspension; -v: rf

zii compounds of type

gi by heating the mixture to a temperature of 100-250 ° C. The latter compound hydrolyzes upon heating, giving one of the products a weak base.

As for palladium, it is converted to the metallic state by the subsequent reduction of its hydroxides with hydrogen at 400 ° C.

The purpose of the invention is to increase the activity of the catalyst.

This goal is achieved by the fact that in the known method, activated carbon is used as a carbon-containing support, which is pre-hydroxylated, and palladium is deposited by sorption of its dichlorobisdimethylformamide-horo complex compound from an aqueous solution, followed by reduction with hydrazine chloride when heated in a water bath.

A significant difference of the proposed method is that for the adsorption of palladium onto the support, an aqueous solution of palladium dichlorobisdimethylformamide with various concentrations is used as the initial solution.

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providing the desired palladium content in the catalyst, which increases the activity of the latter.

Catalyst preparation process

illustrated by the following examples.

Example 1 A palladium dichlorobysdimethylformamide neutral complex compound was prepared by dissolving palladium chloride in dimethylformamide to saturation. The solution filtered from the insoluble residue is treated with ether and the desired compound precipitates. After filtration, the product is dried in air;;: v,.

Preparation of a solution of dimethylformamide complex of the palladium complex: a solution with a content of 0.5% palladium by weight is prepared by adding 0.1775 g of the complex to 50 cm3 of water, followed by bringing the volume of the solution to 100 cm,:;

Preparation of a catalyst containing 0.5% palladium by weight: .30 cm of a freshly prepared solution of palladium dichlorobisdimethylformamide was added to the measured amount of sorbent 1.0t. The selected ratio between the amount of carrier and the concentration of the solution provides the sorption process at a ratio of T: W 1: 3, which provides

prlnbe absorption of palladium from solution in

Within a few hours. For translation

. palladium in metallic state in the same

-; the container with the carrier containing the sorbed complex was doubled in comparison with the stoichiometric amount of hydrazine chloride. The recovery was carried out in a boiling water bath for 2 hours. After washing with water until the reaction to the chloride ion disappeared and drying at 105 ° M

the catalyst is ready to use.

Analogously to example 1, catalysts were prepared with a palladium content of 0.7; 1,2; 1.8; 2.0 wt.% .- Data on the activity of the obtained catalysts are given in the table.; In the French patent, data on palladium content, oxidation temperature and palladium catalyst activity are not given.

Catalytic activity was studied in a flow unit. Test conditions: granule size 2.5-3.5 mm; catalyst bed height 3.0 cm; the cross section of the catalyst bed is 0.8 cm2; catalyst bed volume

2.4 cm3; the feed rate of the gas mixture into the reactor of 0.8 l / min; specific speed 1.0 l / min cm2; temperature conditions 20-300 ° С; humidity of vapor-gas flow 60-65%; carbon monoxide concentration of 0.2-4 vol. %

The catalytic activity was characterized by the degree of conversion of carbon monoxide, which is the ratio of the concentration of carbon dioxide, which is the ratio of the concentration of carbon dioxide in the gas stream behind the catalyst bed to the concentration of carbon dioxide corresponding to the complete oxidation of carbon monoxide. . .

A significant advantage of the proposed catalyst is the invention. Method of producing a palladium catalyst on activated carbon for low-temperature oxidation of hydrogen and carbon monoxide by impregnating activated carbon with a solution of a compound of palladium with dimethylformamide, followed by reduction by heating, washing

a significant increase in its activity, compared with used, with the same palladium content. The use of a catalyst prepared by the proposed method for removing traces of hydrogen from liquid catalite showed that its efficiency is 5 times higher than that of a known catalyst. In addition, the use of a catalyst for the oxidation of carbon monoxide at 160-180 ° C reduces the ignition temperature of the catalyst by 20-30 ° C.

drying and drying, in order to obtain a catalyst with increased catalyst activity, the carbon is hydroxylated before impregnation, the dichlorobis dimethylformamide complex is used as a palladium compound and reduction is carried out by adding hydrazine chloride to the reaction mixture.