RU2050194C1 - Method for preparation of molded vanadium-titanium catalyst for cleaning gases - Google Patents

Abstract

FIELD: catalytic chemistry. SUBSTANCE: method for preparation of molded vanadium-titanium catalyst for cleaning gases includes simultaneous mixing of titanium dioxide with binder and powder or solution of vanadium salts, molding, drying at room temperature, calcination at 450-500 C. Process is conducted with the following quantitative composition of components, mas. vanadium pentoxide 5-20; binder 2-80; the balance, titanium oxide. Binder is used in form of calcium sulfate and/or aluminium sulfate, or mixture of calcium and magnesium sulfates. The binder is produced in situ in reaction of compounds of calcium and magnesium, or aluminium, or calcium and aluminium with stoichiometric quantity of sulfuric acid. Binder is used in form of aluminium hydroxide with subsequent sulfation of calcined catalyst in Klaus apparatus in the presence of oxygen-containing mixture at 250-450 C, or gypsum plaster, or calcium sulfate in form of wastes, e.g. of production of pentaerythrite by neutralization of sulfonic acid with lime milk, or mixture of sulfates with compound of calcium, or calcium and magnesium, or aluminium, or calcium and aluminium which produce in situ sulfates with addition of stoichiometric amount of sulfuric acid, or mixture of gypsum plaster and quicklime which produce calcium sulfate when stoichiometric amount of sulfuric acid is added. Titanium dioxide is used in form of anatase structure, or hydrated titanium dioxide which gives anitase in hat treatment, or titanium dioxide produced by vapor-phase hydrolysis of titanium tetrachloride, or by hydrolysis of alkoxy chloride compounds of titanium, or by thermal hydrolysis of byproducts of hydrometallurgical production of titanium tetrachloride and vanadium oxide, or calcined at 111-500 C titanium dioxide, or preliminarily frozen hydrated titanium dioxide at temperature of minus 5 to minus 60 C. EFFECT: higher efficiency. 11 cl, 3 tbl

Description

 The invention relates to a method for preparing stable and mechanically strong molded catalysts based on vanadium and titanium oxides. The catalysts can be used for gas purification, namely, for the production of elemental sulfur according to the Klaus method, the oxidation of hydrogen sulfide by molecular oxygen, as well as for the hydrolysis of carbon sulfide and selective reduction of nitric oxide with ammonia or hydrogen sulfide.

 As a review of the scientific and patent literature shows, the currently known industrial catalysts of the Klaus process based on aluminum and titanium oxides become inactive and unstable with a high oxygen content in the gas mixture (≈2% vol) due to progressive sulfation.

 Catalysts based on vanadium oxide with the addition of bismuth, copper or with preliminary carbonization of the carrier are more stable and active in this process.

 The most effective and oxygen-stable catalysts for the Claus process are catalytic systems based on titanium and vanadium oxides with the possible addition of antimony.

The most common method for producing molded vanadium-titanium catalyst is the method of pre-forming titanium dioxide followed by impregnation with vanadium salts. It is known that the preparation of molded titanium dioxide in its pure form is difficult and the formation of TiO ₂ often uses the addition of metatitanic acid, silica gel, high molecular weight substances, alkaline earth metal sulfates as binders.

Known methods for increasing the strength of TiO ₂ granules by pre-applying it in the form of a suspension or solution on molded ceramic, metal and other carriers, followed by drying, calcination and impregnation of the second component. A known method of producing vanadium-titanium-antimony catalysts of the Claus process in the presence of oxygen, which consists in sequentially impregnating the carrier (Al ₂ O ₃ , SiO ₂ , Al ₂ O ₃ SiO ₂ ) with active components or in impregnating the molded mass of some active components with an aqueous solution of another component , or in a mixture of the active components and the carrier, followed by molding [1]
The disadvantage of this cooking method is the high intra-diffusion inhibition in the contact grain, which leads to a significant decrease in activity due to a sharp decrease in the degree of surface utilization during the transition to large catalyst grains, as well as insufficient mechanical strength of the calcined catalyst.

, что обусловливает снижение активности при переходе от зерна 1 0,5 мм к зерну 3 мм с 97 до 38% Испытания активности проведены при 250^оС, объемной скорости 72000 ч^-1 и составе реакционной смеси, об. H₂S 2; SO₂ 1; O₂ 1; H₂O 20, остальное гелий. В этих же условиях катализатор по предлагаемому способу имел на зерне 3 мм активность, составляющую 74,5%
Известен способ приготовления формованного ванадий-титанового катализатора для получения элементарной серы и сероводородсодержащих газов в присутствии кислорода [2] заключающийся в смешении диоксида титана в виде геля или ксерогеля с раствором оксалата ванадила с распылительной сушкой и последующим смешением с раствором полиэтиленоксида и связующим, состоящим из золя SiO₂ и раствора оксалата ванадила. Отношение Si и V в связующем составляет 6 2,9. Полученную в смесителе пасту формуют, сушат и прокаливают при 450 500^оС. Способ приготовления катализаторов позволяет увеличить активность катализатора в диффузионной области, однако обладает рядом существенных недостатков.Hereinafter, the sulfur activity in the Klaus reaction is understood to mean the degree of conversion of hydrogen sulfide to elemental sulfur (X _S ,), referred to the equilibrium degree of conversion calculated for the same conditions (X _S ^∞ %). A sample containing 9.95% V ₂ O ₅ 40% TiO ₂ 50% SiO ₂ 0.05% Sb ₂ O ₄ obtained by mixing powders of titanium dioxide, silica gel, antimony oxide and a solution of vanadyl sulfate, followed by molding, drying, drying and stepwise calcination up to 450 ^about C, has a crushing strength along the generatrix of P _about 9.2 kg / cm ² when the diameter of the handle is 4 mm With a total pore volume of 0.59 cm ³ / g, 30% of the pore volume have a diameter earlier than 100

That causes the decrease in activity in going from one grain to grain of 0.5 mm to 3 mm from 97 to 38% of the activity tests performed at 250 ^{° C,} space velocity of 72000 h ^-1 and composition of the reaction mixture, vol. H ₂ S 2; SO ₂ 1; O ₂ 1; H ₂ O 20, the rest is helium. Under the same conditions, the catalyst according to the proposed method had an activity of 74.5% on 3 mm grain
A known method of preparing a molded vanadium-titanium catalyst for producing elemental sulfur and hydrogen sulfide-containing gases in the presence of oxygen [2] consists in mixing titanium dioxide in the form of a gel or xerogel with a solution of vanadyl oxalate with spray drying and subsequent mixing with a solution of polyethylene oxide and a binder consisting of sol SiO ₂ and vanadyl oxalate solution. The ratio of Si to V in the binder is 6 2.9. The resulting paste is molded in a mixer, dried and calcined at 450 500 ^o C. A method for preparing catalysts increases the activity of the catalyst in the diffusion region, but has a number of significant drawbacks.

The main significant disadvantage of this method is the low mechanical strength of the catalyst after step calcination in oxygen. So, for obtained by extrusion of a ring with a diameter of 15 mm, a height of 15 mm with a wall thickness of 3 4 mm, the crushing strength along the generatrix is 3 4 kg / cm ² . A stepwise rise in temperature is necessary when calcining samples according to the method [2] in order to avoid cracking of granules. The second significant disadvantage of the method is the insufficiently high activity of the catalyst, since the SiO ₂ binder, covering part of the surface of the catalyst, does not have catalytic activity in this process. In addition, a sophisticated technology that requires special stages of preparing silica gel, polyethylene oxide, as well as joint spray drying of a VOC ₂ O ₄ solution and hydrated titanium dioxide.

 Closest to the proposed method for the preparation of vanadium-titanium catalysts is the method [3] in which the catalysts are designed for gas purification, namely for the complete oxidation of hydrogen sulfide, sulfur and / or organosulfur compounds in the exhaust gases of the Claus process to sulfur dioxide.

Catalysts contain:
1) titanium dioxide or its mixture with oxides of silicon and zirconium;
2) sulfate of one of the alkaline earth metals;
3) at least one of the following elements or their oxides: Cu, Ag, Zn, Cd, Y, lanthanides, V, Cr, Mo, W, Ni, Mn, Fe, Co, Rh, Ir, Pd, Pt, Sn, Bi.

The content of titanium oxide or its mixture with SiO ₂ or ZrO ₂ is in the range of 60 99% and the content of alkaline earth metal sulfate (preferably CaSO ₄ ) is from 1 to 40 wt.% Of the total mass of the catalyst.

The atomic ratio of catalytically active elements to elements in the carrier, i.e., Ti or (Ti + Si) or to (Ti + Zr), is from 5 ˙ 10 ^-5 to 0.1, i.e. in the case of vanadium-titanium catalysts, based on V ₂ O ₅ in the finished catalyst is limited to 0.003 to 10.6 wt.

 The prototype catalyst can be prepared in one of the following ways.

1. A method of forming elements on the basis of TiO ₂ prepared from powder slabokristallicheskogo and / or amorphous TiO ₂ with the addition of the components of the molding is subjected to drying and calcination in the range of 300 900 ° ^C. Then shaped element sequentially impregnated with aqueous solutions of compounds containing sulfate ion, and solutions of substances containing an alkaline earth cation, so that an alkaline earth metal sulfate is formed within the in situ element. As substances containing SO ₄ ^-2 -ion, use, for example, ammonium sulfate, hydroxylamine sulfate, sulfuric acid. Alkaline earth cation-introducing compounds are water-soluble salts, for example, nitrates, chlorides, acetates. After drying and calcination, a new impregnation with a catalytically active element follows, for example, an aqueous solution of NH ₄ VO ₃ with a new drying and calcination at 300 900 ^about C.

Method 2. According to this method, titanium dioxide and either alkaline earth metal sulfate or substances containing separately the alkaline earth element cation and sulfate anion are mixed. After molding, drying and calcining, the catalytically active substance (NH ₄ VO ₃ ) is impregnated, dried again and calcined. The compounds introducing alkaline earth cations are the same as those in method 1, i.e. are water soluble salts, for example nitrates, acetates, chlorides. The same applies to source compounds of the sulfate anion.

Method 3. Use titanium dioxide obtained by sulfuric acid opening of ilmenite and containing, after hydrolysis, filtration and drying, the sulfate anion in the form of H ₂ SO ₄ , titanium or titanyl sulfate and basic salts. In this method, it is possible either to form titanium dioxide with successive impregnations with solutions containing an alkaline earth element and vanadium, or mixing with an alkaline earth element, molding, drying, calcining and impregnating a compound of vanadium with drying and calcination.

Method 4 Preparation of a catalyst according to the prototype is molded paste mixed composition containing TiO ₂ and alkaline earth element, followed by drying and sulfating a mixture of SO ₂ gas and O ₂ at 250 ⁵⁵⁰ C. The sample was then re-dried if necessary, then impregnated its aqueous solution of a compound of a catalytically active element (NH ₄ VO ₃ ), followed by drying and calcination.

The method of preparation of vanadium-titanium catalysts of the prototype has a number of significant disadvantages. The most significant disadvantage is the low activity of the obtained catalysts in the Claus reaction. Thus, at a temperature of 250 ^{° C} and space velocity 72000 h ^-1 at the grain diameter of 3 mm, the conversion H ₂ S to sulfur was 62.4% compared with the activity of the catalyst in the best of the method equal to 76.0% The composition of the feed mixture in conditions of comparison included vol. H ₂ S 2; SO ₂ 1; O ₂ 1, H ₂ O 20, the rest is helium. The catalysts are also less active in the reduction reactions of nitric oxide with ammonia and hydrogen sulfide than the catalysts of the proposed method. Thus, at a temperature of 250 ^{° C,} space velocity of 36000 h ^-1 and composition of the starting mixture 0,24% NO, 0,33% NH _3, 2% O _2, balance helium, the degree of conversion of nitric oxide to nitrogen on the catalyst prior art is 52 , 8% versus 64% on the catalyst of the invention. At a temperature of 250 ^{° C,} space velocity of 650,000 h ^-1, and the composition of the initial mixture, vol. NO 0.3; H ₂ S 0.5; SO ₂ 0.2; the rest is helium, the degree of conversion of nitric oxide to nitrogen and hydrogen sulfide to sulfur was 40.4 and 43.1% on the catalyst according to the prototype versus 46.4 and 46.9% on the catalyst according to the proposed method, respectively.

The catalyst according to the method of the prototype 10% V ₂ O ₅ 9.45% CaSO ₄ 80.55% TiO ₂ was prepared according to example 12 [3] A paste of hydrated titanium dioxide (metatitanic acid) obtained by sulfuric acid opening of ilmenite contained sulfate ion in relation to to TiO ₂ equal to 0.08. The paste was mixed with an aqueous solution of calcium nitrate in the ratio of Ca / Ti 0,033 (example 5 of the prototype). After drying at 150 ° ^C the powder is mixed with water and extrusion molded cuttings diameter of 4 mm, which were dried at ¹¹⁰ ° C and calcined at 400 ^C. The sample at this stage contains 10.5 wt preparation. CaSO ₄ and has a crushing strength along the generatrix of 14.0 kg / cm ² and a specific surface area of 110 m ² / t. The sample according to Example 12, the prototype, is impregnated with an aqueous solution of NH ₄ VO ₃ based on the 10% V ₂ O ₅ in the finished product, dried for 12 hours at 110 ^C and calcined for 4 hours at 450 ^C. The lower the catalyst activity of the prototype than the proposed method, apparently, is associated with a small degree of surface utilization and heterogeneous distribution of the active component when impregnated with a solution of NH ₄ VO ₃ in comparison with the proposed method using the method of mixing the components.

The second significant disadvantage of the prototype method is the partial cracking of the extrudate during the impregnation with a solution of NH ₄ VO ₃ and the low mechanical strength of the catalyst obtained from the prototype in comparison with the catalyst according to the method of the invention. So, the strength of the catalyst according to the prototype was 12 kg / cm ² for a shank with an extrudate ⌀ 4 mm and 20 kg / cm ² with an extrudate ⌀ 3 mm against a maximum strength of 75 kg / cm ² on the best (in strength) catalyst of the invention with an extrudate diameter 4 mm The catalyst ring with a diameter of 15 mm at a height of 15 mm and a wall thickness of 3 4 mm cannot be obtained by the prototype method due to the low strength. The crushing strength along the generatrix of the indicated ring according to the method of the invention is from 5 to 14 kg / cm ² .

 The third significant drawback of the known method is the complexity, laboriousness and energy intensity, since all variants of the method require two or even three times drying and calcination of the samples, while the proposed method of preparation includes only the steps of a single drying, i.e. drying at room temperature, and calcining.

 The fourth significant disadvantage of the prototype method is the possible presence of toxic products in the exhaust gases during drying and calcining, such as nitrogen oxides when using alkaline earth metal nitrates and ammonium metavanadate, and hydrogen chloride when using alkaline earth metal chlorides. To create a non-waste technology based on the prototype method, the development of additional methods for purification of exhaust gases is required, which makes the technology more expensive.

 Thus, the known methods for the preparation of vanadium-titanium molded catalysts do not allow both high activity in the Claus process occurring in the presence of oxygen and high strength of the shaped elements after calcination, i.e. Do not provide high quality product. Low mechanical strength and high hydraulic resistance of the catalyst layer, which is in the form of cuttings or balls, makes it difficult to use the catalyst obtained by the prototype method in a fixed-bed reactor.

 The aim of the invention is to increase the activity and mechanical strength of vanadium-titanium catalysts, as well as simplifying the method of their preparation.

The catalysts obtained by the method of the invention contain, by weight. vanadium based on V ₂ O ₅ 5 20; a binder (based on CaSO ₄ or CaSO ₄ + MgSO ₄ or CaSO ₄ + + Al ₂ (SO ₄ ) ₃ or Al ₂ (SO ₄ ) ₃ 2 80; the rest is titanium dioxide.

This goal is achieved by the method of preparing molded vanadium-titanium catalysts, which consists in mixing calcined and dried titanium dioxide powder, including hydrated, with a powder, suspension or aqueous solution of a binder with the addition of powder or an aqueous solution of vanadium salt and then molding rings into cuttings , blocks and other shaped elements, drying at room temperature and calcining in a stream of air at 450 500 ^about C for 2 4 hours with the formation of stable and active vanadium-titanium compounds inertia.

As a binder can be used:
1) calcium sulfate powder, including building gypsum, as well as a powder or aqueous solution of any calcium compounds with a stoichiometric amount of sulfuric acid necessary for the formation of calcium sulfate;
2) a mixture of calcium sulfate powder or gypsum with a powder or aqueous solution of other calcium compounds with a stoichiometric amount of H ₂ SO ₄ necessary for the formation of calcium sulfate from these compounds;
3) a mixture of gypsum and quicklime, which gives calcium sulfate when stoichiometric amounts of sulfuric acid are added;
4) pentaerythritol production waste, which is a product of the neutralization of sulfonic acid by milk of lime;
5) a mixture of powders of calcium sulfate and magnesium sulfate, as well as a mixture of powders or aqueous solutions of any compounds of calcium and magnesium with a stoichiometric amount of sulfuric acid necessary for the formation of calcium sulfate and magnesium, respectively;
6) aluminum sulfate powder, as well as a powder or aqueous solution of any aluminum compound with a stoichiometric amount of sulfuric acid necessary for the formation of aluminum sulfate;
7) a mixture of powders of calcium sulfate and aluminum sulfate, as well as a mixture of powders or aqueous solutions of any compounds of calcium or aluminum with a stoichiometric amount of sulfuric acid necessary for the formation of calcium sulfate and aluminum sulfate, respectively;
8) aluminum hydroxide, which sulfation occurs after mixing with the titanium and vanadium compounds, molding, drying and calcining the reaction mixture via characteristic of the Claus process, but additionally containing oxygen at temperatures of 250 450 ° ^C. For example, the sulphated mixture may comprise about . H ₂ S 2; SO ₂ 1; O ₂ 1; H ₂ O 20; the rest is nitrogen.

Hereinafter, hydrated titanium dioxide is understood to mean compounds with the general formula Ti (OH) _y O _x , where x + y / 2 2, including ortho and metatitanic acids.

The main characteristics of the catalysts prepared by the proposed method were the activity and sulfur selectivity determined during the operation of the catalyst in the Klaus reaction and the oxidation of hydrogen sulfide by molecular oxygen, the activity of carbon sulfide in the COS hydrolysis reaction, as well as the activity in the selective reduction reactions of nitric oxide with ammonia or hydrogen sulfide. The duration of the catalysts was 24 hours. The table. 1, the values of activity and sulfur selectivity are the ratio of the observed values to the equilibrium ones. For all the obtained catalysts, the mechanical strength of cuttings, rings, or blocks by crushing along the generatrix (P _o , kg / cm ² ) was also determined. The measurements were carried out on a PPS-3 device.

The essence of this method of preparing a vanadium-titanium catalyst is as follows. A suspension, paste or powder of titanium dioxide, including hydrated, is obtained by liquid-phase or vapor-phase hydrolysis of TiCl ₄ , by hydrolysis of alkoxychloride compounds of the type TiCl _4-n (OR) _n , where n 0-4, an alkyl radical, by sulfuric acid opening of ilmenite, as well as by thermohydrolysis of titanium-containing vanadium waste products such as raffinate or secondary distillate. Before drying the hydrated titanium dioxide suspension may be frozen at temperatures in the range of (5 to 60) ° ^C. The titanium dioxide was dried at ¹¹⁰ ° C using a spray dryer "Anhydro", type dryer "Spin" or oven to a constant moisture content. Available heat treatment of titanium dioxide in the range of 111 500 ° ^C. The calcium sulphate, gypsum plaster, production waste of pentaerythritol, and a mixture of calcium sulfate or calcium magnesium and aluminum sulfate or aluminum, or insoluble compounds of these metals (oxides, hydroxides) is dried at a temperature as necessary 110 200 ^about C and after grinding in a ball or disk mill is mixed with titanium dioxide in a kneading machine for 30 minutes Then, powder or an aqueous solution of a vanadium salt (e.g., VOSO ₄ , VOC ₂ O ₄ ) is gradually added to the kneading machine with stirring. If it is necessary to introduce a sulfate ion with an aqueous solution of a vanadium salt, sulfuric acid is added in a stoichiometric amount to form calcium, magnesium or aluminum sulfates, respectively. In the case of using water-soluble compounds of calcium, magnesium or aluminum (nitrates, chlorides, acetates), titanium dioxide in a kneading machine is mixed with an aqueous solution of the corresponding salt and the stoichiometric amount of sulfuric acid necessary for the formation of the corresponding sulfate. If necessary, the mixture is dried and mixed in a kneading machine with an aqueous solution of vanadium salt.

To improve the porous structure at the mixing stage, pore-forming additives, such as, for example, polyethylene oxide, cellulose, can be introduced. The resulting mixture is continued to mix for 10 30 minutes, after which it is molded in the form of granules with a diameter of 4 mm, rings with a diameter and height of 15 13 mm with a wall thickness of 3 4 mm or in the form of other shaped elements. Forming elements provyalivayut at room temperature for 10 15 hours, and then calcined in flowing air in a muffle furnace 2 to 4 hours at 450 500 ^o C. Selection of binders as calcium sulfate, a mixture of magnesium sulfate and calcium or aluminum sulphate or a mixture of calcium sulphate and aluminum due to their chemical and thermal stability under conditions of catalysis, inertness and low coefficient of linear expansion, which simplifies the preparation technology, allowing calcination of air-dried samples immediately at 450 500 ^about C.

The binder content in the calcined catalyst can vary within wide limits from 2 to 80 wt. as shown in the examples. A lower binder content leads to a loss of strength of the shaped elements, while a higher binder content leads to a loss in the ability of the catalyst to efficiently hydrolyze carbon sulfide. The choice of the content of the active component V ₂ O ₅ in the catalyst due to the fact that the introduction of less than 5 wt. V ₂ O ₅ leads to the production of a low activity catalyst. The use of the content of V ₂ O ₅ over 20 wt. irrational due to the rise in price of the catalyst. The choice of the temperature of sulfation of the catalyst in the reaction mixture (250 450 ^about C) when used as a binder of aluminum hydroxide is determined by the maximum speed of this process under these conditions, as well as the possibility of sulfation directly in the Claus apparatus in the presence of O ₂ in the process conditions. The minimum calcination temperature is limited to titanium dioxide drying temperature ^of 110 C and a maximum resistance of titanium dioxide to a transition of anatase to rutile. It is shown that the presence of 10 wt. Rutile mixed with anatase in a vanadium-titanium catalyst leads to a rapid loss of activity in the Claus reaction. Thus, at 250 ^{° C} in a mixture of. H ₂ S 2; SO ₂ 1; O ₂ 1; H ₂ O 20; the rest is helium, in 12 hours the activity decreases from 37 to 27%. The temperatures of preliminary freezing of hydrated titanium dioxide are determined by the actual conditions of winter transportation and storage of the paste. It is known that when the hydrated titanium dioxide refreezing irreversible changes hydroxyl coatings, as well as the specific surface of the sample dried at the standard temperature of 110 ° ^C.

In the case of the preparation of the catalysts according to the method of [2], preliminary freezing of the titanium dioxide paste to (5 60) ^° C leads to the formation of a fragile extrudate that crumbles already at the drying stage. In the method of the prototype [3] the use of pre-subjected to freezing paste of titanium dioxide leads to a significant decrease in the strength of the final product to 8 10 kg / cm ² .

Thus, the hallmarks of the proposed method from the prototype are:
a) the use of the method of preparation of vanadium-titanium catalysts, which consists in the simultaneous mixing of components using calcium sulfate, a mixture of calcium and magnesium sulfates, aluminum sulfate or a mixture of calcium and aluminum sulfates directly introduced or formed in situ as binders;
b) the ability to prepare catalysts in a wide range of component concentrations (5 to 20 wt. V ₂ O ₅ , 2 to 80 wt. binder, the rest is titanium dioxide), using the minimum number of stages: mixing, molding, drying, calcination;
c) the use of hydrated titanium dioxide as a raw material, previously frozen at a temperature of (5 60) ^o C, or calcined in the range 111 500 ^o C;
d) sulfation of the catalyst directly in a Claus apparatus at 250 ⁴⁵⁰ ° C in a mixture of H ₂ S, SO _2, O ₂ and H ₂ O, when used as a binder of aluminum hydroxide.

Preparation of elemental sulfur by oxidation of hydrogen sulphide with sulfur dioxide, oxygen or a mixture thereof carried out in a thermostatted flow installation fixed bed at atmospheric pressure within a temperature range of 200 350 ° ^C. The catalyst was performed similarly tested in COS hydrolysis, while the presence of a mixture of H ₂ S, H ₂ O, O ₂ , CO ₂ . In the tests, the composition of the mixture, the space velocity, and the temperature were varied. The composition of the initial and final mixture was controlled by gas chromatography. A comparison of the catalysts prepared by the proposed method with the catalyst by the prototype method was carried out under the same conditions.

100% где С_cos ^o, C

, C

начальные, а С_cos ^к, C

, C

конечные объемные концентрации указанных газов.The degree of conversion of sulfur compounds to elemental sulfur (X _S ) was determined by the formula:
X _s

100% where C _cos ^o , C

, C

initial, and С _cos ^к , C

, C

final volumetric concentrations of these gases.

100% Степень превращения сероводорода в присутствии cos рассчитывали по формуле:
X

100% а селективность по сере определяли отношением
C_s

100%
Активности катализаторов по сере, серооксиду углерода и селективность по сере, приведенные в табл. 1, даны в отношении к равновесным величинам, рассчитанным для этих условий.The degree of conversion of carbon _sulfide (X _cos ) by the hydrolysis reaction was determined by the formula:
X _cos

100% The degree of conversion of hydrogen sulfide in the presence of cos was calculated by the formula:
X

100% and sulfur selectivity was determined by the ratio
C _s

100%
The activity of the catalysts for sulfur, carbon sulfide and selectivity for sulfur are given in table. 1 are given in relation to equilibrium values calculated for these conditions.

Recovery ammonia oxide in oxygen mixtures in the presence of hydrogen sulfide or sulfur dioxide was performed in a robust glass reactor with an internal diameter of 6 mm and a fixed bed of vanadium-titanium catalyst at atmospheric pressure and a temperature of 250 ^C. The composition of the initial and final mixtures were analyzed by gas chromatography. The entire gas supply system was thermostated at 130 ^o C.

где C

конечная концентрация NH₃ в эксперименте со смесью, содержащей NH₃ и O₂; C

конечная концентрация NH₃ в эксперименте со смесью, содержащей NH₃, NO и O₂. Концентрации NH₃ и O₂ в обоих экспериментах одинаковы. С_NO ^o начальная концентрация NO, об.The degree of conversion of nitric oxide in the reduction reaction with ammonia was determined by the formula:
X _NO

where c

final concentration of NH ₃ in an experiment with a mixture containing NH ₃ and O ₂ ; C

final concentration of NH ₃ in an experiment with a mixture containing NH ₃ , NO, and O ₂ . The concentrations of NH ₃ and O _{2 are the} same in both experiments. With _NO ^{o the} initial concentration of NO, vol.

100%
X

=

·100% где С_NO ^o, C

начальные, С_NO ^к, C

конечные концентрации NO и H₂S соответственно.The degree of conversion of nitric oxide and hydrogen sulfide to sulfur in the reaction of NO reduction with hydrogen sulfide was determined respectively by the formula:
X _NO

100%
X

=

100% where C _NO ^o , C

initial, C _NO ^to , C

final concentrations of NO and H ₂ S, respectively.

The invention is illustrated by examples 1 to 14 and table. 1 3. In the table. 1 in the same conditions compared activity and selectivity for sulfur and activity for the hydrolysis of CoS for catalysts prepared by the prototype method and the proposed method. A comparison of the activity in the Klaus processes and the oxidation of hydrogen sulfide by oxygen and a mixture of SO ₂ and O ₂ was carried out on a catalyst grain of 3 mm at a volumetric rate of the mixture of 72000 h ^-1 . Comparison under hydrolysis of CoS was carried out on a catalyst grain of 3 mm at a space velocity of 3600 h ^-1 .

In the table. 2 under the same conditions, the activity of vanadium-titanium catalysts prepared according to the prototype method and the proposed method in the reduction reaction of nitric oxide with ammonia in the presence of oxygen, sulfur dioxide and water vapor are compared. The volumetric rate of the reaction mixture was 360,000 h ^-1 with a grain size of the catalyst of 0.5 0.25 mm

In the table. 3 also, under the same conditions, the activity of vanadium-titanium catalysts obtained by the method of the invention and the prototype method in the reduction reaction of nitric oxide with hydrogen sulfide is compared. The space velocity in these experiments was 650,000 h ^-1 with catalyst grain sizes of 0.5 0.25 mm.

PRI me R 1. For the preparation of 100 g of catalyst composition 5% V ₂ O ₅ ; 30% CaSO ₄ and 65% TiO ₂ charge 159.6 g of paste metatitanic acid (hydrated titanium dioxide) obtained sulfuric acid ilmenite opening and having a humidity of 60% The paste was dried at ¹¹⁰ ° C in a spray dryer "Anhydro". Humidity paste and powder is determined by maintaining the sample in an oven at ¹¹⁰ ° C for 12 hours. To the resulting powder in a kneader, 30 g of calcium sulfate produced as pentaerythritol production waste with neutralizing a sulphonic acid solution of calcium hydroxide and dried at 140 ¹⁶⁰ C. To the kneading machine add 5.97 g of vanadyl sulfate VOSO ₄ ˙ 3H ₂ O grade analytical grade. and the components of the mixture are mixed for 30 minutes, after which 58 ml of distilled water are added and stirring is continued for another 15 minutes. The resulting paste is transferred to a metal syringe and molded cuttings with a diameter of 4 mm The extrudate was dried at room temperature to the air-dry state of 12 15 hours and calcined in a muffle in flowing air at 450 500 ^o C for 2 hours.

As shown in the table. 1, the resulting catalyst has a higher crushing strength along the generatrix (24.5 kg / cm ² ) and activity in the Klaus reaction in the presence of water vapor in the complex mode (2% H ₂ S, 1% SO ₂ , 1% O ₂ , 20% H ₂ O, the rest is helium) than the catalyst according to the prototype method.

Example 2. To prepare 100 g of a catalyst with a composition of 20% V ₂ O ₅ , 2% CaSO ₄ , 78 TiO ₂ , take hydrated titanium dioxide (calculated on 78 g of TiO ₂ ) obtained by hydrolysis of titanium tetrachloride at pH 7 and ⁷⁰ ° C in the presence of NH ₄ OH and dried after filtration at 110 ° ^C. The titanium dioxide are mixed in a kneader with 1.1 g of calcium hydroxide and stirred brand ch.d.a powders for 30 minutes, then gradually add an aqueous solution containing 1.45 g of concentrated sulfuric acid (in terms of anhydrous) and 34 g of vanadyl oxalate. Vanadyl oxalate was prepared by reacting 20 g of vanadium pentoxide mark "h" with an aqueous solution containing 41.6 g of H ₂ C ₂ O ₄ O ₂ ˙ 2H mark "h", at 40 ° ^C. After stirring for 15 minutes the paste 20 is molded in the form of cuttings with a diameter of 4 mm, dried in air and calcined for 4 hours at 450 500 ^about C. In the table. 1 shows that the calcined sample has a strength of 15.0 kg / cm ² and surpasses the prototype catalyst in activity in the oxidation reaction of hydrogen sulfide and in mixed mode.

PRI me R 3. To prepare 100 g of the catalyst with a composition of 10% V ₂ O ₅ , 80% CaSO ₄ , 10% TiO contribute 80 g of calcium sulfate grade to the kneading machine. after appropriate drying and 12.3 g of hydrated titanium dioxide. The hydrated titanium dioxide was prepared by hydrolysis of titanium ethoxychloride in the presence of NH ₄ OH at room temperature, and after filtration dried at 110 ° ^C.

The powders are mixed for 30 minutes, after which an aqueous solution containing 11.94 g of VOSO ₄ ˙ 3H ₂ O grade analytical grade grade is gradually introduced into the kneading machine. Stirring is continued for another 15 to 20 minutes and then ⌀ 4 mm cuttings, rings with a diameter of 15 mm and honeycomb blocks 24 x 24 x 40 mm in size with a wall thickness of 3 mm are formed by extrusion. After drying and calcining at 450 500 ^about C, as can be seen from the table. 1, the catalyst in the form of cuttings, rings and blocks has a strength of 30, 9.5 and 12 kg / cm ^2, respectively, and activity in the oxidation of hydrogen sulfide by oxygen in the presence of water vapor, as well as in a difficult mode, exceeding the activity of the prototype catalyst.

Example 4. Similar to examples 1 3. The difference is that the catalyst composition of 15% V ₂ O ₅ , 27% CaSO ₄ , 3% MgSO ₄ , 55% TiO receive, using as raw material for titanium dioxide containing 16.06 grams of vanadyl oxalate vapor 21 and the hydrolysis product of TiCl ₄ at 450 ° ^C. The binder used powdery mixture of magnesium and calcium oxides in a weight ratio of 1 11. After mixing the powders for 30 minutes in a kneader, an aqueous solution gradually introduced , 8 g of H ₂ SO ₄ (calculated on anhydrous). Water cooling is added to the kneading machine and stirring is carried out for 15 to 20 minutes. Obtained after calcination, the catalyst has a maximum strength in the series of catalysts according to the proposed method, comprising 75 kg / cm ² . The activity of this catalyst in the Klaus reaction, the complex mode and the hydrolysis of carbon dioxide exceeds the activity of the prototype catalyst.

PRI me R 5. The catalyst composition of 15% V ₂ O ₅ , 30% CaSO ₄ , 55% TiO ₂ receive analogously to example 1. The difference lies in the use as a binder of building gypsum brand G-6. As a solution of the active component, a solution of vanadyl oxalate obtained according to example 2 containing 0.2% polyethylene oxide, based on the total weight of the mixture, is introduced into the kneading machine. The finished catalyst has a strength of 27 kg / cm ² and activity in the mixed mode, exceeding the activity of the catalyst of the prototype.

PRI me R 6. To prepare 100 g of the catalyst composition of 15% V ₂ O ₅ , 5% Al ₂ (SO ₄ ) 3, 80% TiO take 98 g of metatitanic acid obtained by sulfuric acid dissection of ilmenite and dried previously at 110 ^about C (see example 1). As a binder, 5 g of aluminum sulphate grade are introduced into the kneading machine. calculated on anhydrous and after stirring for 30 minutes, an aqueous solution containing 25.5 g of VOC ₂ O _{4 is} gradually poured. A method of obtaining vanadyl oxalate is shown in example 2. Further preparation of the catalyst is similar to example 1. The resulting catalyst, as can be seen from example 6, table. 1, has a high strength of 37 kg / cm ² and activity in the mixed mode (250 ^about C, 2% H ₂ S, 1% SO ₂ , 1% O ₂ , 20% H ₂ O), exceeding the activity of the catalyst of the prototype.

PRI me R 7. Obtaining a catalyst with a composition of 10% C ₂ O ₅ , 30% Al ₂ (SO ₄ ) ₃ , 60% TiO ₂ analogously to example 6. The difference lies in the fact that AlOOH aluminum hydroxide is used as a binder. After molding, wilting and calcination at 450 500 ^o C catalyst was charged to a Claus reactor and treated in a mixture containing 2% H ₂ S, 1% SO _2, 1% O _2, 20% H ₂ O, balance helium, gradually raising the temperature from 250 to 450 ^about C for 12 hours. The strength of the finished catalyst is 37.9 kg / cm ² . Its activity in complex mode is higher than the activity of the catalyst of the prototype.

PRI me R 8. The catalyst composition of 15% V ₂ O ₅ , 10% Al ₂ (SO ₄ ) ₃ , 10% CaSO ₄ , 65% TiO ₂ obtained analogously to example 6. The difference is that as a binder make a mixture of calcium sulfate and aluminum hydroxide. The vanadium compound (vanadyl sulfate) is introduced in the form of an aqueous solution containing 8.6 g of H ₂ SO ₄ calculated on the anhydrous basis for the formation of aluminum sulfate. When mixing the components in a kneading machine, water cooling may be activated. The finished catalyst after calcination has a strength of 53 kg / cm ² and exceeds the activity of the prototype catalyst in complex mode.

 The following are examples of the preparation of catalysts, the compositions of which are beyond the concentration of the proposed method.

Example 9. A catalyst with a composition of 4% V ₂ O ₅ , 30% CaSO ₄ , 66% TiO _{2 was} obtained analogously to Example 1. The difference was the use of a smaller amount of vanadyl sulfate (4.8 g). As can be seen from the table. 1, the finished catalyst containing 4 wt. V ₂ O ₅ had a lower activity in the complex mode of the Claus process than the catalyst of the prototype.

PRI me R 10. The catalyst composition of 15% V ₂ O ₅ , 1% CaSO ₄ , 84% TiO ₂ obtained analogously to example 1. The difference lies in the use of a small amount of CaSO ₄ binder obtained by mixing calcium hydroxide and sulfuric acid. The finished catalyst has more activity in the complex mode of the Claus process than the catalyst of the prototype, however, the strength of the obtained catalyst is unsatisfactory.

Example 11. A catalyst with a composition of 15% V ₂ O ₅ , 81% CaSO ₄ , 4% TiO _{2 is} obtained by mixing powders of dried hydrated titanium dioxide obtained by sulfuric acid opening of ilmenite, gypsum grade G-6 with the addition of an aqueous solution of vanadyl sulfate . The finished catalyst after shaping, wilting and calcination at 450 ^{500 °} C had a high strength and activity in a complex mode, but active in the hydrolysis reaction, the QoS on this catalyst was lower than for the catalyst of the prior art.

 The following are examples of the preparation of catalysts by the proposed method using them in the processes of reduction of nitric oxide with ammonia and hydrogen sulfide.

PRI me R 12. The catalyst composition of 15% V ₂ O ₅ , 30% CaSO ₄ , 55% TiO ₂ obtained by mixing powders of pre-frozen metatitanic acid, gypsum and calcium oxide in the form of quicklime with the addition of sulfuric acid. A paste of metatitanic acid obtained by opening sulfuric acid ilmenite, frozen at a temperature of -35 ^about C and kept for 2 days. The paste was then dried with a spray dryer "Anhydro" at ¹¹⁰ ° C and in an amount of 67.4 g was placed in a kneader. At the same time, 15 g of gypsum G-6 and 6.18 g of quicklime are added thereto and the powders are mixed for 30 minutes. An aqueous solution was added to the kneading machine, containing 25.5 g of vanadyl oxalate and 10.8 g of H ₂ SO ₄ , calculated as anhydrous, and continued to mix for 15 to 20 minutes. After molding using metallic syringe through a die of 4 mm, wilting and calcination at 450 500 ^o C, the catalyst flowing air has a strength of 44 kg / cm ² and the activity in the reduction of nitrogen ammonia oxide in the presence of oxygen, as well as SO ₂ and water vapor higher than on the prototype catalyst (table. 2).

The comparison is carried out at a temperature of 250 ^about With the volumetric velocity of the mixture 360,000 h ^-1 on the catalyst fraction of 0.5 0.25 mm

PRI me R 13. The catalyst composition of 15% V ₂ O ₅ , 30% CaSO ₄ , 55% TiO ₂ receive analogously to example 12. The differences are that the hydrated titanium dioxide obtained by sulfuric acid opening of ilmenite, dried at 110 ^about C and calcined at 500 ^about C for 4 hours. As a binder, a mixture of calcium sulfate (15 g) and calcium oxide is used with the addition of 10.8 g of H ₂ SO ₄ based on anhydrous to the solution of vanadyl oxalate. The finished catalyst has a strength of 30.6 kg / cm ² and is superior in activity to the prototype catalyst in the reduction reaction of nitric oxide with hydrogen sulfide (Table 3). The comparison is carried out at a temperature of 250 ^about C and a space velocity of the mixture of 650,000 h ^-1 on the grain of the catalyst of 0.5 0.25 mm

PRI me R 14. The catalyst composition of 15% V ₂ O ₅ , 30% CaSO ₄ , 65% TiO ₂ is prepared per 100 g of the finished product as follows. Metatitanic acid is obtained by thermohydrolysis of waste hydrometallurgical production of titanium tetrachloride and vanadium oxide. Secondary distillate and raffinate containing titanium tetrachloride were mixed in a ratio of 1 30 and after thermal hydrolysis, neutralizing with calcium hydroxide, washing and filtration was dried at ¹¹⁰ ° C in an oven for 12 hours. 106 g of the dried powder containing 9 atomic% calcium, mixed in a kneading machine with an aqueous solution containing 25.5 g of vanadyl oxalate and 21.6 g of H ₂ SO ₄ calculated on anhydrous. After 15 to 20 minutes of mixing, the paste is formed into an extrudate with a diameter of 4 mm and a tube with an external diameter of 13 mm, a height of 13 mm and a thickness of 3 4 mm. Durability and the extrudate crush tube along the generatrix for provyalennogo were calcined at 450 and ⁵⁰⁰ ° C, respectively 33 and 14 kg / cm ^2. The activity of the catalyst in the reduction reaction of nitric oxide with hydrogen sulfide exceeds the activity for the catalyst of the prototype.

As can be seen from the above examples, the proposed method for the preparation of a molded oxygen-resistant vanadium-titanium catalyst containing calcium, calcium and magnesium, aluminum, or calcium and aluminum sulfates as a binder can significantly increase the strength and activity of sulfur and hydrolysis of CoS catalysts in the process of obtaining elementary sulfur from hydrogen sulfide-containing gases in the presence of oxygen, as well as activity in the reduction of nitric oxide with ammonia or hydrogen sulfide. In addition, the proposed method of preparation allows to obtain catalysts that have a number of useful qualities that are not achieved when preparing the catalysts by other methods, namely:
high mechanical strength of the catalysts, which allows to produce various shaped elements by the proposed method;
high thermal stability of the catalysts, allowing calcining the catalysts immediately at 450 500 ^about C, without using a stepwise temperature rise;
high and stable activity of the catalysts both in the presence of oxygen in the Claus reaction, and in the presence of SO ₂ in the reaction of NO reduction with ammonia;
high productivity of catalysts in the diffusion region of the bond with an optimal porous structure;
the suitability of the proposed method for the preparation of the catalyst in the case of a low specific surface area of the initial titanium dioxide, including in the case of varieties of raw materials previously frozen or calcined to 500 ^° C;
the simplicity and cost-effectiveness of the proposed method, requiring only one-time calcination of the catalyst and using such cheap raw materials as pentaerythritol production waste, hydrometallurgical production waste, gypsum, lime;
the possibility of obtaining a vanadium-titanium catalyst by an environmentally friendly method when using vanadyl oxalate as a vanadium raw material, which gives only carbon dioxide during calcination;
the suitability of the method for producing catalysts for various gas purification processes, such as the Claus process, oxidation of hydrogen sulfide, hydrolysis of CoS, reduction of nitric oxide with ammonia or hydrogen sulfide.

Claims (10)

1. A METHOD FOR PREPARING A FORMED VANADIUM-TITANIUM CATALYST FOR GAS CLEANING, comprising reacting titanium dioxide, a compound of vanadium and a calcium sulfate binder or any calcium compound that gives sulfate when reacted with sulfuric acid in situ, drying, calcining, characterized in that of obtaining a catalyst with increased activity, mechanical strength and simplification of the technology, the interaction is carried out by simultaneously mixing titanium dioxide with a binder and a powder or a solution of vanadium salt I followed by molding, drying at room temperature and calcination at 450 500 ^o C and the process is carried out at a ratio of components providing the following content in the catalyst by weight. Vanadium Pentoxide 5 20
Binder 2 80
Titanium dioxide
2. The method according to claim 1, characterized in that as a binder use calcium sulfate and / or aluminum or a mixture of calcium sulfates and magnesium.  3. The method according to claim 2, characterized in that they use a binder obtained in situ by the interaction of compounds of calcium and magnesium or aluminum, or calcium and aluminum with a stoichiometric amount of sulfuric acid. 4. The method according to claim 1, characterized in that aluminum hydroxide is used as a binder, followed by sulfation of the calcined catalyst in a Claus apparatus in the presence of an oxygen-containing mixture at 250 450 ^o C.  5. The method according to claim 1, characterized in that the binder used is gypsum or calcium sulfate obtained in the form of waste, for example, in the production of pentaerythritol by neutralizing sulfonic acid with milk of lime.  6. The method according to PP. 1 to 3, characterized in that as a binder use mixtures of the corresponding sulfates with compounds of calcium or calcium and magnesium, or aluminum, or calcium and aluminum, which give in situ sulfates when stoichiometric amounts of sulfuric acid are added.  7. The method according to claim 1, characterized in that as a binder use a mixture of gypsum and quicklime, which gives calcium sulfate when adding a stoichiometric amount of sulfuric acid.  8. The method according to PP. 1 to 7, characterized in that they use titanium dioxide of anatase structure or a hydrated form of titanium dioxide, which gives anatase during heat treatment.  9. The method according to claim 8, characterized in that titanium dioxide is obtained by vapor-phase hydrolysis of titanium tetrachloride, or by hydrolysis of titanium alkoxychloride compounds, or by thermo-hydrolysis of by-products of the hydrometallurgical production of titanium tetrachloride and vanadium oxide. 10. The method according to PP. 1 to 8, characterized in that using calcined at 111 500 ^o With titanium dioxide. 11. The method according to PP. 1 to 8, characterized in that use is pre-frozen in the range of 5 -60 ^o With hydrated titanium dioxide.

Images