SU906936A1 - Method of catalyting cleaning of gases from nitrogen oxides - Google Patents

Description

one

The invention relates to the catalytic purification of gases, in particular nitrogen oxides,

A known method of purification of process and waste gases of the chemical industry from nitrogen oxides by various reducing agents (H, CO, CH / (or their mixtures) on catalysts containing platinum group metals. The process is carried out at volumetric rates of 8-20 thousand. 700750С. The average consumption of the reducing gas exceeds the stoichiometric value by 10-30% 1

The disadvantage of this method is the high process temperature and the high consumption of the reducing gas.

The closest to the proposed invention in its technical essence and the achieved result is a method of catalytic purification of gases from nitrogen oxides by hydrogenation of nitrogen oxides in the presence of a palladium-hydrogen catalyst on a U-carrier. The process is carried out at elevated temperature with an excess hydrogen-reducing gas 2 a

The disadvantage of this method is high temperature in the process, increased consumption of reducing gas, the formation of ammonia and other harmful substances.

The aim of the invention is to reduce the consumption of the reducing gas and to increase the degree of purification

This goal is achieved by the fact that according to the method of catalytic gas purification from nitrogen oxides by hydrogenation of nitrogen oxides in the presence of a palladium catalyst on a U-Al20j carrier in the atmosphere of a hydrogen reducing gas, palladium catalysts are used.

20 lyser on a carrier of a mixture of ff-AI Oj and calcium oxide, and the cleaning process is carried out with a volume ratio of oxidative and reducing 3 components Ig: (NOx + Oj) (l, 05-1.1): 1.0 and 250 -350 ° C. In addition, the oxygen content in the purified gas is maintained in the range of 1.0-1.8 vol. D. In this case, the process is carried out with a volumetric gas velocity equal to 6-12 thousand c. Example. The experiments were carried out at the facility of the weak nitric acid plant of the Rustavi chemical plant. The catalyst was palladium, the content of 1 palladium was 0.3, the carrier was f-AljOj and CaOc. The volume of the catalyst. 50 ml. The composition of the initial mixture, OBD: NOx 0,2-0,5; Og 2-i, 5; And 2, -5.5; the rest is nitrogen. The volume ratio is 1: 1.1. Table 1 shows the data on the effect of the oxygen content in the purified gas on the degree of conversion N0; at W 12 thousand h-, t As can be seen from the data of Table 1, the most favorable for carrying out the process of hydrogenation of nitrogen oxides are the conditions when the residual oxygen content is up to 1, 8 o 6%, i.e. when the conditions are met, at which approximately hydrogenation of oxygen and above is achieved. Table 2 shows data on the effect of temperature on the degree of hydrogenation or NOx at. W 12 thousand. H, the content of 02 in the purified gas to 1, 5 1.8 about. and t 150-350 ° C. According to the data of Table 2, in the experimental conditions, the temperature range should be considered to be 2 0-350 ° C. Table 3 shows the data on the ali-40 of the space velocity for the degree of hydrogenation of nitrogen oxides at t 300 ° C and the oxygen content in the gas up to 1,) 8 OBD Thus, from the data in Tables 1 - 3 it can be concluded that the optimal conditions for the process of hydrogenation of nitrogen oxides with hydrogen are the space velocities of the initial mixture of 6 to 12 thousand hours and the temperature range 250-350 ° C. in the purified gas should be maintained up to 1.3-1.8 vol. At the same time, the degree of hydr Calibration of nitrogen oxides with hydrogen is 90-98 °. Under similar conditions, when using a palladium catalyst on an alumina carrier without calcium oxide, the degree of hydrogenation of nitrogen oxides with hydrogen does not exceed. it5-70. Carrying out the process in an oxidizing environment eliminates the formation of an adverse ammonia substance, and using a supported catalyst from a mixture of - Aj Oj and CaO enhances the adsorption of oxides and hydrogen and to a lesser extent oxygen on the surface of the catalyst. With a volume ratio of oxidizing and reducing components Hj: (NOx + 02) (1.05-1,):, 0, Oy is burned and 90-98 hydrogenation of nitrogen oxides occurs. Incomplete oxygen oxidation reduces the heat load on the catalyst. Using the proposed method allows the process to be carried out at elevated temperatures; halve the consumption of hydrogen and eliminate the formation of harmful by-products, such as ammonia. T a b l and c

Continuation of table 1

3.2 3.5

w

2.6 3.8 3, 2.1

1.7 3.0

Table 3

79069368

claim 2 Method according to claim 2. The method of catalytic purification of a city in a purified gas is supported by gases from nitrogen oxides by hydrogenation in the range of 1.0-1.8 v. D. vania oxides of nitrogen in the presence of 5 3 "The method according to nl, o tl and h of palladium catalyst on the carrier so u and with the fact that the process is carried out

le. 5 Al20j in a gas-re-growth atmosphere — with a gas flow rate equal to

Novi tel-hydrogen, I distinguish-6-12 thousand hours. u and so that, in order to reduce

consumption of reducing gas and higher sources of information, degrees of purification, fatigue-less-used copper catalyst taken into account during the examination. 1. Thomas H, AljOj industrial catalys and calcium oxides, attic processes and effective purification processes are carried out with the volume-lizatoro M, Mir, 1973, p. 187th ratio of oxidizing and voi-15189.

flush components H2: (NOx + 2. Patent of England N 871755,

Og) (1, 05-1,1): 1.0 and 250-3504.kl. C 1 A, published 19b1.

This is what the content of kis

Claims (2)

Claim 1. Thomas C. Industrial catalytic processes and effective catalysts "And", Mir, 1973, p. 187 15 189. 1. The method of catalytic purification of gases from nitrogen oxides by hydrogenation of nitrogen oxides in the presence of a palladium catalyst on a carrier. y-AlgOj in an atmosphere of a reducing gas-hydrogen, characterized in that, in order to reduce the consumption of a reducing gas and increase the degree of purification, a palladium catalyst on a support of a mixture of U-A1j0 ₃ and calcium oxide is used, and • the cleaning process is carried out with a volumetric the ratio of oxidizing and reducing components of H ₂ : (ΝΟχ + 10 ₂ ) = (1.05-1.1): 1.0 and 250-350 ° C. 2 o The method of pop, 1, distinguishing with the fact that the oxygen content in the purified gas is maintained in the range of 1.0-1.8 vol. L. 5 3 “The method according to claim 1, which is characterized in that the process is carried out 'at a gas volumetric velocity of 6-12 thousand hours ¹ . ¹⁰ sources of information taken into account during the examination 2. England Patent No. 871755, cl. C 1 A, published 1961.