Catalyst for oxidation of molecular nitrogen

 

(57) Abstract:

The invention concerns a catalyst composition for oxidation of molecular nitrogen him oxygen compounds. The inventive catalyst contains as a main component (75-96,5%) cheap and non-deficient oxide of iron (III) and optionally oxides of metals selected from the group comprising aluminum, chromium, magnesium, vanadium, cerium, cesium, calcium, bismuth, boron, lanthanum, titanium, copper, barium, zirconium, manganese, cadmium, yttrium, strontium, molybdenum, gallium. The invention reduces the cost of production of nitrogen oxides by reducing the cost of the catalyst without compromising its quality.

The invention relates to compositions of catalysts intended for the oxidation of molecular nitrogen him oxygen compounds.

The formed oxides of nitrogen are used to obtain other compounds of nitrogen, mainly in the production of nitric acid.

Currently in the industry oxides of nitrogen are obtained mainly through the oxidation of ammonia with oxygen to nitric oxide (II) catalysts at 800 - 900oC [1].

The disadvantage of this method is a multistage process, ispolzovaniem receipt of nitrogen oxides from nitrogen and oxygen in a plasma furnace, surface of which is coated with a catalyst for accelerating the reaction of interaction of nitrogen and oxygen [2].

As catalysts for use molybdenum trioxide (MoO3) and tungsten trioxide (WO3).

The output of nitric oxide in the process is 2 - 4% vol.

The disadvantage of this method is the high temperature oxidation of molecular nitrogen (3000 - 3500 K) and use as catalysts oxides of rare metals.

Closest to the claimed technical essence and the achieved effect is the catalyst according to the patent [3].

The essence of the method lies in the fact that molecular nitrogen nitrous gases oxygen oxidizes nitrogen compounds to nitrogen oxides on the net platinum catalysts and oxide catalysts based heat-resistant and rare metals such as cobalt, Nickel, iron and others, or mixtures thereof, at temperatures of 500 - 700oC.

The disadvantage of this method is the oxidation of nitrogen expensive and scarce metals.

The aim of the present invention is to reduce material and energy costs for the production of nitrogen oxides by reducing starlogo nitrogen compounds bound nitrogen is used catalyst, containing a heat-resistant oxide of the metal oxide iron (III) and optionally oxides of metals selected from the group comprising aluminum, chromium, magnesium, vanadium, cerium, cesium, calcium, bismuth, boron, lanthanum, titanium, copper, barium, zirconium, manganese, cadmium, yttrium, strontium, molybdenum, gallium, in the following ratio, wt.%:

iron oxide (III) 75-96,5

oxides of metals selected from the above group, the rest of it.

The hallmark of the claimed catalyst is content as a main component (up to 96.5%) cheap and non-deficient oxide of iron (III). Moreover, the physico-chemical and physico-mechanical properties of the catalyst is not particularly limited against similar properties of the prototype.

The range of content introduced additives (promoters) to the main component selected from considerations of the conservation of its high selectivity and activity for the oxidation of molecular nitrogen while maintaining the high performance of its physico-chemical properties.

Example 1. The prepared catalyst for the oxidation of molecular nitrogen composition, wt.%: Fe2O3-76,0; Zn - 16,0; Bi2O3to 8.0.

Used for the preparation of crystallic the 26H2O - 587 g

Bi(NO3)39H2O - 191,3 g

Nitrates were mixed and heated to decomposition to oxides of the metals. The resulting mass is kept at 500oC for 3 hours, alloy preformed and then progulivali at 700oC.

Testing activity conducted on the industrial liaison office of the production of non-concentrated nitric acid (d=2.9 m).

The apparatus was placed the catalytic system of the 2 catalysts:

stage 1 - Pt-net (a catalyst for the oxidation of ammonia by oxygen),

2nd level - oxide catalyst of the above composition for the oxidation of molecular nitrogen.

Load the ammonia-air mixture in the 1st stage was 10573 m3per hour when the content 10,15% vol. ammonia (dry gas).

After the conversion of ammonia to 1-St stage ( = 96,4%) of the total volume of gas was 10841 m3per hour with NO content 1034,5 m3/hour.

In hot nitrous gas is introduced, the flow of the gas mixture with an oxidant in the total number of 2656,2 m3per hour when the oxygen content of the nitrogen compounds 125,85 m3/hour.

The amount of oxide catalyst was 0.7 m3that provided the volumetric rate is3per hour, 15,86% vol.

N2- 9104,3 m3per hour, 64,45% vol.

O2- 1092,8 m3/h, 8,10% vol.

HNO3- 125,3 m3per hour, 0,93% vol.

NO - 1034,5 m3per hour, 7,66% vol.

Total - 13497,7 m3per hour, about 100,000.%

The gas passed through the layer of oxide catalyst, where the reaction proceeded:

2HNO3+N2=3NO+NO2+H2O (1)

4HNO3=4NO2+2H2O+O2. (2)

Coming out of the reactor gas had the composition:

H2O - 2203,0 m3per hour, 16,18%

N2- 9048,6 m3per hour, 66,44%

O2- 1096,4 m3per hour, 8,04%

NO2- 70,1 m3per hour, 0,52%

NO - 1201,7 m3per hour, 8,82%

Total - 13619,9 m3per hour, 100.00% of

The temperature of the nitrous gases on the layer of catalyst was decreased from 800oC to 500 - 520oC.

The mass balance calculations of the contact node and process indicators was carried out on the computer on the basis of the flow rate of the gas flow and chemical analyses of bound nitrogen compounds in them.

From pulpwood volumes of gases introduced into the reactor, and the output from this it follows that the net increase of nitrogen compounds due to the oxidized molecular nitrogen was calculated based on

< / BR>
Moreover, the utilization of vapor HNO3pillar is because part of the ammonia is lost to the 1st stage, turning in nitrogen ( = 96,4). Taking into account this factor, the increase of nitrogen compounds on the 2nd stage reaction is

< / BR>
Example 2. Similarly indicated in example 1, the prepared catalyst containing, wt.%: Fe2O3- 95; CeO2- 2,75; CuO - 1,25; Cs2O - 1,0.

Tests of this sample of catalyst was also carried out in industrial conditions described in example 1.

The gas flow through the main course (ABC) is V = 11790 m3/HR to 10.09% NH3and the conversion of ammonia to NO - 92%. Temperature conversion 800 - 810oC, the pressure is atmospheric. For lateral entry (before the second layer of catalyst) - 4576 m3per hour when the vapor content HNO3298,6 m3/hour.

The mixture of these two streams before catalyst stage II:

H2O - 3962,0 m3per hour, 23,77% vol.

N2- 10080,6 m3/hours of 60.50% vol.

O2- 1227,6 m3per hour, 7,37% vol.

HNO3- 298,6 m3per hour, 1,79% vol.

NO - 1094,4 m3per hour, to 6.57% vol.

Total - 16663,2 m3per hour, about 100,00.%

After passing through the catalyst layer and the reactions of oxidation of N2the composition of the gas mixture is as follows:

H2O - 4111,3 m3per hour, 24,26.%

N2- 9 NO - 1479,8 m3per hour, 8,73% vol.

Total - 16951,5 m3per hour, about 100,00.%

The balance of the volumes of gases net increase of nitrogen compounds was 10.9%, and the degree of use of vapor HNO3was the reaction of (1) 86,04%, according to reaction (2) 13,96%.

Temperature conversion decreased from 780 - 800-490 - 500oC.

Example 3. According to the mode described in example 1, the prepared catalyst composition: 90% Fe2O3; 5% CaO and 5% ZrO2.

A sample of the catalyst was tested under laboratory conditions. In a reactor made of quartz glass (d=25 mm) load the prepared sample of the catalyst grain diameter of 2 to 3 mm in the amount of 40 cm3.

The required temperature in the reaction zone was provided by external heating of the furnace.

From above through the cylinder apparatus was fed a stream of air, in the amount of 300 l/h. He before the layer of catalyst mixed with the second, lateral gas stream with an oxidant (acidic nitrogen compounds) in the amount of 113,7 l/h. The mixed stream is passed through the catalyst bed with falling temperatures 640 - 500oC.

On the basis of measurements of air flow and content analysis vapors HNO3to the catalyst and the nitrogen oxide after him rasschityvaet:

H2O - 4,9 l/h, 1,19%

N2- 319,9 l/h, 77,33%

O285,1 l/h 20,56%

HNO3- 3.8 l/h 0,92%

NO - 0 l/h, 0

Total - 413,7 l/h, 100.00% of

The composition of the gas mixture at the outlet of the device (after catalyst):

H2O - 6,8 l/h, 1,63%

N2- 319,0 l/h, 76,48%

O2- 85,5 l/h, 20,51%

NO2- 2,8 l/h, 0,68%

NO - 2,9 l/h, 0,70%

Total - 417,0 l/h, 100.00% of

Net gains of nitrogen compounds is

< / BR>
The degree of excess of HNO3according to reaction (1) to 51.3%, according to reaction (2) of 48.7%.

Example 4. A sample of the catalyst prepared in accordance with example 1, contained Fe2O3- 92,0%; MgO - 7,5%; V2O5of 0.5% was used in the laboratory conditions described in example 3.

The composition of the mixture of gases to catalyst:

H2O - 5,88 l/h, 1,42%

N2- 319,95 l/h, 77,01%

O2- 85,05 l/h, 20,47%

HNO3- 4,55 l/h, 1,10%

NO - 0, 0

Total - 415,43 l/h, 100.00% of

The gas at the outlet of the apparatus was composed of:

H2O - 8,15 l/h, 1,94%

N2- 318,95 l/h, 76,06%

O2- 85,69 l/h, 20,43%

NO2- 3.55 l/h 0,85%

NO - 2,99 l/h, 0,71%

Total - 419,33 l/h, 100.00% of

The increase of nitrogen compounds is

< / BR>
The degree of Pribram is Lisa samples off-gas vapor content HNO3not found. This applies both to industrial and laboratory conditions.

The proposed catalyst may be used for oxidation of molecular nitrogen him oxygen compounds under atmospheric and elevated pressure in the presence of nitrogen oxides, ammonia, water vapor and oxygen in the quantitative limits that are limited by the possibility of chemical reactions between them and the vapors of nitric acid or their degradation products.

Literature

1. M M Karavaev, A. P. Zasorin, N. F. Kleschev. Catalytic oxidation of ammonia, M., Chemistry, 1983, 231.

2. Application France N 2451888, C 01 B 21/20, 21/40, the company Electricite de France, Appl. 21.03.79, publ. 21.11.80.

3. RF patent N 2070865 from 27.12.96, priority 19.07.95.

Catalyst for oxidation of molecular nitrogen compounds bound nitrogen under atmospheric and elevated pressure containing heat-resistant iron oxide (III), and optionally, a metal oxide, characterized in that as an additional metal oxides using metal oxides selected from the group comprising aluminum, chromium, magnesium, vanadium, cerium, cesium, calcium, bismuth, boron, lanthanum, titanium, copper, barium, zirconium, manganese, cadmium, yttrium, strontium, molybdenum,different from the above-mentioned groups - The rest

 

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