LT3146B - Catalyst for oxidation of exaust nitrosated gases and processing them - Google Patents

Abstract

Nitrous gas pollutants oxidation accelerant - calcium hydrosilicate C-S-H (1) is designed for the catalytic oxidation of small concentrations of NO, present in nitrous gas pollutants, and for the removal of formed NO2 by absorption. It can be applicable for neutralization of chemistry, energetic and other industry pollutants being discharged into the atmosphere.The oxidation of nitrous gas pollutants takes place at a temperature of 50-150 degrees C using the accelerant synthetic calcium hydrosilicate C-S-H (1), which eliminates the water steam effect, blocking the active surface of the accelerant. The synthetic accelerant - calcium hydrosilicate C-S-H (1) - also has 1-1.5 of molecule of the water of zeolithic tone in its structure and is synthesized from the waste of AIF3 production and industrial lime, when the molar ratio of initial compound CaO and SiO2 is C/S = 0,8; the temperature is 90-95 degrees C and the duration is 3 hours.Nitrous gas pollutants can be oxidised with the offered accelerant when the temperatures are quite low (50-150 degrees C) and the power input is small for the thermal activation of the process and for production of the synthetic accelerant.

Description

The proposed catalyst-CSH (I) type calcium silicate (C = CaO, S = _SiO2 H = H ₂ O) is given nitrous gas emissions in low concentrations of NO by catalytic oxidation and isolating the NO ₂ removal of the sorption process and can be applied to chemical , energy and other industrial plants to decontaminate the atmosphere.

Oxidation of NO to NO ₂ can be carried out using catalysts: silica gel activated carbon, anhydrous calcium aluminates, etc. [(SU Aut No. 1 Oxide Adsorption and Crystalline Aluminosilicates, Synthetic Sodium Zeolites, and 1725991, and Logak LG Catalytic Oxidation of Low Percent Nitrogen Monoxide Nitrogen by Synthetic Mordenite, Dr. Dissertation Autoreferate, Kazan, 1972 (in Russian)). catalysts contain catalytic components such as oxides of platinum, titanium, tin, nickel, molybdenum, copper and other metals.The disadvantage of these catalysts is that the catalysts used are deactivated under the influence of water and / or nitric acid vapors, as nitrous gases usually there is water vapor.

The closest proposed catalysts are zeolitic anhydrous aluminosilicates with a silicate modulus of 40 to 700 (SU aut'.l. No. 1433486) used for the purification of NO _X oxides. Disadvantages of these catalysts are the high thermal energy required for the synthesis, the additional soaking of the aluminosilicates in the urea solution for 1 hour, followed by drying and heating of the gas passing through the column to 6080 ° C.

SUMMARY OF THE INVENTION The object of the present invention is to increase the efficiency of the catalytic oxidation of NO to NO ₂ in a wet gas environment and to reduce the energy required for the process.

The objective is achieved by oxidation of NO with the use of synthetic catalyst-C-S-H (I) type calcium hydrosilicate, which eliminates the action of water vapor at 50-150'C on the active surface of conventional catalysts.

The proposed synthetic catalysts-calcium hydrosilicates-C-S-H (I) contain 1-1.5 molecules of water in their structure, which prevents the adsorption of water vapor in the wet nitrous gas onto the active surface of the catalyst and deactivates it. Catalyst is synthesized from low-cost materials: A1F-, industrial waste and industrial lime at 90-95'C for 3 hours, so the cost of preparing it is many times that of a catalyst.

smaller by another. analogous example

From a premix of industrial lime and A1F-. production waste at a molar ratio of C / S = 0.8, V / K = 10, synthesis temperature of 90 C and duration of 3 hours. Its flow rate is 50 1 / h, the humidity data are given in Table 1.

Catalyst-C-S-H The resulting sorbent 1-2 mm thermostated 14 mm column through which oxide (0.6% NO)

4mg / l

Get the table

Calcium hydrosilicate catalyst, compared to CuO on a - A1 ₂ O ₃ carrier in the case of non - dried nitrosated gas with O ₂ concentration of 21% and NO - 0.6%.

Yesterday Catalyst NO oxidation degree No. name nis,% at temperatures 50 ° C 150 ° C 250 ° C 350 ° C 1. C-S-H (I) type calcium hydrosilicate 38 37 36 35 2. CuO / a - A1 ₂ O ₃ 15th 22nd 38 43

According to these data, the hydrosilicate catalyst is about 3 times more efficient than the supported CuO / a - Al ₂ O ₃ catalyst in the temperature range of 50-150 ^u C.

At temperatures below, it is inappropriate to run due to the influence of the coefficient.

for 50 ° C negative

NO oxidation is a temperature example. For the comparison, the degree of oxidation of NO is determined under the same conditions using a CuO catalyst on a - Al ₂ O _{3 support} and an empty sorbent column for dry and moist nitrous gas. The data obtained is shown in the figure. The curves presented show that the efficiency of the calcium hydrosilicate catalyst is practically unchanged with increasing temperature, i.e., the temperature coefficient is practically equal to one unit and only after reaching about 250 ° C does the supported catalyst equal the efficiency with the _z hydrosilicate. Noteworthy is the low efficiency of the supported catalyst CuO / a - Al ₂ O _{3 in the} temperature range of 50-150 ° C and the influence of the sorbent column walls on the oxidation process: increasing the temperature in the empty sorbent column increases the oxidation rate. In the proposed process, the NO range specified in the NO medium is relevant because it requires minimal energy consumption to evaporate the water droplets in the nitrous gas and can be achieved by utilizing low-potential heat resources. Therefore, the proposed process is most effective in the range of 50-150 ° C, with a concentration of nitrosome gas of less than 1% and using a synthesized catalyst-calcium hydrosilicate.

Calcium Hydrosilicate C-S-H has the required properties

I) synthesized from aluminum fluoride production waste with active SiO _; . and chemical SiCs-57, 41%, A1F -.- 12, 13%, F = 3.42%, moisture loss on heating-32.04% for industrial fluoride production wastes. Composition of industrial lime: CaO-83.22%, MgO-2, 18%, CaCO -, = 8, 74%, containing significant lime. Composition of aluminum

17.3%, chemical hydrated water - 4.72% C-S-H (I) with low alkalinity

Calcium hydrosilicates of the type can be obtained from these materials by comparison surfaces.

Previous studies have shown that aluminum fluoride production wastes can significantly intensify the synthesis of low-base calcium hydrosilicates and carry them out at atmospheric pressure. In order to prepare a catalyst with potentially greater comparative surface adsorption properties, the synthesis of hydrosilicates was carried out at temperatures of 80-95'C by changing the molar CaO / SiO _; . ratio (C / S) of 0.8 to 1.2 and maintaining water-solids ratio (V / K) of 10.

The test data and properties of the synthesis products are shown in Table 2.

irf

The data in Table 2 show that at the duration of the 1-hour isothermal synthesis product, the unreacted Ca (OH) ₂ and CSH (I) type calcium hydrosilicates remain in the semi-amorphous state. By extending the synthesis time to 3 hours, the resulting products are free of lime at a C / S ratio of 0.8 to 1.0. Increasing the C / S of the mixture to 1.2, even after 3 hours of synthesis, leaves unreacted Ca (OH) ₂ . Furthermore, the extension of the initial mixture of the C / S of 0.8 to 1.2 and at the duration of the synthesis of 3 S h maximum _level. value obtained at C / S = 0.8 and synthesis temperature 90 ° C. Increasing C / S can lead to the formation of highly basic calcium hydrosilicates (a C ₂ S hydrate, hillebrandite) with crystals thousands of times larger than CSH (I), resulting in a marked reduction in the comparative surfaces of the synthesis products. By increasing the duration and temperature of the fusion isothermal period, the fine-fiber CSH (I) recrystallizes into large plaque calcium hydrosilicate tartrate.

Thus, as can be seen from the data in Table 2, the synthesis products obtained from the initial mixture having a C / S = 0.8 at a synthesis temperature of 90-95 ° C and an isothermal period of 3 hours should exhibit the best catalytic properties.

Compared to the prototype, the present invention improves the efficiency of the oxidation process of nitrous gas emissions and reduces energy consumption by a factor of 2 to 3, in addition to using low-cost and non-deficient materials for catalyst synthesis.

table

Synthesis conditions and properties of hydrosilicate catalysts

Yesterday No. Synthesis conditions Properties of Synthesis Products tempe- will circle ra C CaO / SiO ₂ duration h sworn nose pulling ram, PH not- reactive cool CaO volume% compare surface Slyg m ² / g crystalline phases mineral composition 1 80 O 00 1 12.45 1, 89 - C ₃ AH ₆ , CaF ₂ , Ca (0 H) ₂ 2 3 10.73 - 12, 69 C ₃ AH ₆ , CaF ₂ 3 6th 10.25 - - C ₃ AH ₆ , CaF ₂ 4 o 1-1 1 12.45 4.75 - C ₃ AH ₆ , CaF ₂ , Ca (0 H) ₂ 5 3 12.40 2.11 39.49 C ₃ AHg, CaF ₂ , Ca (0H) ₂ 6th 6th 10.95 - - C ₃ AH ₆ , CaF ₂ 7th 1.2 1 12.45 6, 99 - C ₃ AH _ę, CaF _2, Ca (OH) ₂ 8th 3 12.45 5, 70 33, 65 C ₃ AH ₆ , CaF ₂ , Ca (OH) ₂ 9th 6th 11, 95 0.73 C ₃ AHg, CaF ₂ , Ca (0 H) ₂ 10th 90 0.8 1 10.92 0.23 - C + AHg, CaF ₂ , Ca (OH) ₂ 11th 3 9.85 - 50.82 C ₃ AH ₆ , CaF ₂ , C-S-H (I) 12th 6th 9.80 - - C ₃ AH ₆ , CaF ₂ , C-S-H (I) 13th O I-i 1 12.45 3.01 - C ₃ AH ₆ , CaF ₂ , Ca (0 H) ₂ 14th 3 10, 75 - 35.05 C / AHg, CaF ₂ , C-S-H (I)

Yesterday

No.

Synthesis conditions

Properties of Synthesis Products Temperature C

CaO /

SiO ₂

1.2

0.8 duration h aqueous extract, pH

10.15

12.45

11.80

10, 90

9.00 unresponsive

CaO content% relative surface Mineral composition of crystalline phases of Slyg m ² / g

C3AH5, CaF ₂ , CSH (I) tobermorite

6.66

1.20

45.26

35.00

C ₃ AH ₆ , CaF ₂ , Ca (OH) ₂ C / AHg, CaF ₂ , Ca (OH) ₂ C _{3 A} H 5, CaF ₂ , Ca (OH) ₂

C3AH5, CaF ₂ ,

C-S-H (I)

C3AH «= 3CaO. A1 ₂ O ₃ .6H, 0

Claims (1)

DEFINITION OF INVENTION A catalyst for the catalytic oxidation of nitrous gas at 50 to 150 ° C, characterized in that the catalyst is a synthetic calcium hydrosilicate having a CaO / SiO ₂ molar ratio of 0.8 and having a structure of 1 to 1.5 molecules of zeolite-type water. 2. A process for the preparation of the oxidation catalyst for nitrous gas emissions according to claim 1, characterized in that the calcium hydrosilicate catalyst, CS-H (I), is synthesized from A1F-. industrial waste and industrial lime in the molar amount of CaO / SiO ₂ in the initial mixture 15 ratio of 0.8, synthesis temperature 90-95 ^u C, and duration Temperature dependence of NO oxidation j NO2 on various types of catalysts.