RU2039006C1 - Method of nitrogen monoxide producing, catalyst for nitrogen monoxide producing and a method of catalyst preparing for nitrogen monoxide producing - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: nitrogen monoxide is produced by reduction of 0.3-15 wt.-% nitric acid with hydrogen on the catalyst containing platinum, platinum (II) sulfide and Pt (IV) oxide on the graphite-carrier at the following ratio of components, wt.-% platinum 0.252-0.320; platinum (II) sulfide 0.125-0.188; platinum (IV) oxide 0.050-0.070, and carrier the rest. Method is carried out both in batch-operated and continuous regime. Process of nitric acid reduction is ceased at its concentration below 0.3 wt.-% and catalyst requires activation by thermal treatment. At concentration of nitric acid above 15% reduction process is carried out but part of platinum is transferred to the solution from the catalyst surface. EFFECT: increased yield of nitrogen monoxide, decreased nitrogen-containing impurities, enhanced activity of catalyst. 4 cl, 2 tbl

Description

 The invention relates to the catalytic production of nitric monoxide with high selectivity and can be used in the electronics industry, as well as to find application for the processing of dilute aqueous solutions of nitric acid, which are incidentally formed in the production of hydroxylamine sulfate and nitric acid.

The closest to the claimed one of the attainable result is a method for catalytic reduction of nitrogen monoxide with ammonia superheated to a temperature of 250-270 ^{° C} nitric acid vapor with a concentration of 35-80 wt. on a platinum catalyst [1]
However, this method does not provide a sufficiently high yield of nitrogen monoxide, and the resulting nitrogen monoxide is contaminated with other nitrogen-containing impurities.

Closest to the claimed method for producing a catalyst, the technical essence is a method for producing a platinum catalyst in the form of platinum supported on graphite and modified with sulfur for catalytic hydrogen reduction of oxygen nitrogen compounds to hydroxylamine, according to which Pt (IV) in aqueous solution is converted by weak reduction into Pt ( II), and then with a stronger reducing agent Pt (II) in Pt (0) with simultaneous deposition on electrode graphite, moreover, the activity and selectivity of the catalyst are set by introducing osoderzhaschih compounds in an amount of up to 25 at. in relation to platinum [2]
The advantage of this method is its low cost, due to the use of platinum as a raw material in an amount not exceeding 0.5 wt. In addition, the method provides a catalyst with stable activity and selectivity.

 A disadvantage of the known method of preparation of the catalyst is the low activity of the obtained catalyst and the reaction of hydrogenation of nitric acid to nitrogen monoxide and significant contamination of the product with nitrogen-containing impurities, since the resulting nitrogen monoxide is hydrogenated on this catalyst further to hydroxylamine, ammonia and diazate oxide.

 The purpose of the invention is to increase the yield of nitrogen monoxide, to reduce the content of nitrogen-containing impurities in it, and to obtain a catalyst with increased activity.

This goal is achieved by the fact that nitrogen monoxide is obtained by reducing 0.3-15 wt.% Nitric acid with hydrogen on a catalyst containing platinum, platinum (II) sulfide and Pt (IV) oxide on a graphite carrier, in the following ratio of components, wt. Platinum 0.252-0.320 Platinum (II) sulfide 0.125-0.188 Platinum (IV) oxide 0.050-0.070 Carrier Other
The method of producing NO is carried out both in batch and continuous mode. When the concentration of nitric acid is below 0.3 wt. the process of its reduction is terminated and the catalyst requires activation by heat treatment. At a concentration of nitric acid above 15%, the reduction process proceeds, but part of the platinum passes into the solution from the surface of the catalyst.

The catalyst is prepared by impregnating the graphite support with a solution of platinum chloride, followed by reduction in platinum (IV) in an acidic aqueous solution to platinum and converting platinum to sulfide form when treated with a sulfur-containing compound. The resulting solid catalyst product is filtered off and washed with water. Then the product is additionally treated with 1-15 wt.-Nitric acid at a temperature of 60-90 ^about C for 0.5-2 hours

PRI me R 1. 10.6 g of Platinum chloride with a platinum content (IV) of 37.6 wt. dissolved in 17.5 ml of distilled water. 60 ml of distilled water are poured into a stirred reactor, 800 g of a dry carrier (powdered electrode graphite) are sprinkled with stirring. The suspension is heated in the reactor to 85-90 ° ^C. The reactor was then added chloroplatinic acid solution was prepared, poured in 80.5 ml of an aqueous 35 wt. solution of HCl and 19 ml of an aqueous (60 wt.%) solution of nitric acid and add 500 ml of distilled water. The reactor temperature was maintained at 85-90 ^C. The resulting mixture was neutralized by addition of, preventing strong foaming, 55 g of Na ₂ CO _3. The rate of addition of 2 g per min. The pH of the solution in this case reaches 2. Then, by adding 5 g of Na ₂ CO _{3, the} pH of the solution is adjusted to 3.2-3.5, after which 40 g of sodium acetate are added until a pH of 5.5 is reached. In the resulting buffer solution, platinum (IV) is reduced in Pt (II) with sodium dithionite, which is introduced in the form of an aqueous solution containing 1.2 g of sodium dithionite, 17.5 ml of water and 0.1 g of Na ₂ CO ₃ (the last component is necessary to stabilize the solution). The flow rate of the solution is 0.5 ml per min. The translation of Pt (IV) into Pt (II) proceeds according to the reaction:
3PtCl ₄ + Na ₂ S ₂ O ₄ + H ₂ O _ → 3PtCl ₂ + Na ₂ SO ₄ + 6HCl + H ₂ SO ₄
(1) The completeness of the conversion of Pt (IV) to Pt (II) is controlled by a qualitative reaction with potassium iodide. To give certain characteristics to the catalyst (activity and selectivity), sodium dithionite is additionally introduced, linking part of platinum (up to 25 at.) To platinum sulfide:
3PtCl ₂ + 4Na ₂ S ₂ O ₄ + 4H ₂ O _ → 3Pt + 4Na ₂ SO ₄ + 6HCl + H ₂ SO ₄
(2) Then, 60 ml in wt% formic acid are added to the reactor and Pt (II) in Pt (0) is reduced within 5-6 hours by the reaction:
PtCl ₂ + HCOOH _ → Pt + 2HCl + CO ₂
(3) Platinum and platinum sulfide are deposited on a support. The suspension is cooled and the solid catalyst is filtered off. Then washed on the filter with water until neutral wash water. The catalyst is further modified by oxygen, subjecting it to a heat treatment at ⁸⁰ ° C for 1 h in 3-prefecture mas. aqueous solution of nitric acid. The composition of the catalyst before and after heat treatment is given in table. 1. It also shows data for other specific examples of the preparation of the catalyst according to the invention under other heat treatment conditions and according to the prototype.

Nitrogen monoxide is obtained at ⁹⁰ ° C in a laboratory reactor of 500 ml equipped with a stirrer. 10 g of a platinum catalyst and 250 ml of a 0.3-15 wt% aqueous solution of nitric acid are charged into the reactor. The concentration of nitric acid in the reactor is maintained by the constant addition of a portion of fresh acid as it is activated. In the lower part of the reactor serves 6.6 nm ³ / h of electrolytic hydrogen. From the upper part of the reactor, a gas phase containing nitrogen monoxide, diazot oxide and hydrogen is removed. The yield of nitrogen monoxide in terms of the spent nitric acid is 99.1%. The composition of the gas phase is shown in Table 2, which also shows data for other specific examples of the implementation of the method for producing NO according to the invention.

 As can be seen from the data table. 1 and 2, during the heat treatment in the range of nitric acid concentrations of 1-15 wt. not found a significant effect of the concentration of nitric acid (ceteris paribus) on the properties of the resulting catalyst. The nitric acid concentration is below 0.8 ms. not sufficient to obtain an active catalyst, since under these conditions it is not modified sufficiently by oxygen.

 Heat treatment with nitric acid with a concentration of 0.8-1.0 wt. leads to a workable catalyst, but this requires a longer time and temperature, in addition, the activity of such a catalyst is lower than when processed in the range of 1-15 wt.% nitric acid.

 When the concentration of nitric acid is above 15 wt. the dissolution of platinum becomes noticeable, which leads to its loss and a change in the composition and properties of the catalyst.

Heat treatment condition corresponding to 0.4 hours, even at ⁸⁰ ° C or 1 hour ^at 50 ° C is insufficient for the modification of the catalyst with oxygen. The content of platinum (IV) oxide in these samples is at the level of the prototype (0.02-0.025 wt.), Which was not subjected to heat treatment.

These samples, as well as the catalyst of the prototype, do not show activity in the reaction of reduction of nitric acid to nitrogen monoxide. Heat treatment time of 0.5 hours and a temperature of 60 ^{° C} is sufficient for obtaining an active catalyst sample. The content of platinum (IV) oxide is increased to 0.055 wt. An increase in the heat treatment time above 1 h is impractical since it does not affect the properties of the catalyst. Raising the temperature of heat treatment time can be reduced, but the properties of the catalyst it has practically no effect, and about 100 ^{° C} is reached the boiling point of the aqueous solution.

 This invention allows to prepare a more active than in the prototype, a catalyst for producing nitrogen monoxide. The output of NO is 99.1-99.8% against 94.1% of the prototype. The content of nitrogen-containing impurities in the finished product is 3-10 times less than in the prototype. In addition, the invention allows the use of dilute solutions of nitric acid, which are wastes of the chemical industry.

Claims (1)

 1. A method of producing nitric monoxide by reducing nitric acid on a catalyst containing platinum, platinum (II) sulfide and platinum (IV) oxide on a graphite carrier, characterized in that, in order to increase the yield of nitrogen monoxide and reduce the content of nitrogen-containing impurities in it , in the process using 0.3 to 15 wt .- nitric acid, the recovery is carried out with gaseous hydrogen on a catalyst containing these components in the following ratio, wt. Platinum 0.252 0.320
Platinum (II) sulfide 0.125 0.188
Platinum (IV) oxide 0.055 0.070
Media Else
2. A catalyst for producing nitrogen monoxide containing platinum, platinum (II) sulfide and platinum (IV) oxide on a graphite carrier, characterized in that, in order to increase the activity of the catalyst, it contains components in the following ratio, wt. Platinum 0.252 0.320
Platinum (II) sulfide 0.125 0.188
Platinum (IV) oxide 0.055 0.070
Media Else
3. A method of preparing a catalyst for producing nitrogen monoxide by impregnating a graphite support with a solution of platinum chloride, followed by reduction in platinum (IV) in an acidic aqueous solution into platinum and converting platinum into a sulfide form by treatment with a sulfur-containing compound, followed by filtration and washing of the solid catalyst product, characterized in that, in order to obtain a catalyst with increased activity, the catalyst product is additionally treated with 1 to 15 wt.% solution of nitrogen acid 60 minutes at 90 ^o C for 0.5 2 hours and the process is carried out at the following component ratio, catalyst wt. Platinum 0.252 0.320
Platinum (II) sulfide 0.125 0.188
Platinum (IV) oxide 0.055 0.070
Media Else

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