RU2255805C2 - Heterogeneous catalyst for oxidation of inorganic and/or organic compounds on polymer carrier - Google Patents

Abstract

FIELD: oxidation catalysts.

SUBSTANCE: invention relates to manufacture of heterogeneous catalysts for the processes of liquid-phase oxidation of inorganic and/or organic compounds, including sulfur-containing ones, with air oxygen. Invention provides heterogeneous catalyst containing (i) active component (15-50%) on polymer carrier, namely polyethylene, polypropylene, polystyrene or another polymer, said active component being variable-valence metal oxides and/or hydroxides, or spinels, and additionally (ii) modifying additive (0.5-20%), namely organic bases and/or heteropolyacids, and/or carbon-containing material.

EFFECT: increased catalytic activity.

2 cl, 5 tbl, 6 ex

Description

The invention relates to the production of heterogeneous catalysts for liquid-phase oxidation of inorganic (sulfur, nitrogen, phosphorus, etc.) and organic (surfactants, phenols, oil products, etc.) compounds with atmospheric oxygen.

These catalysts can be used in the energy, oil refining, petrochemical, chemical, pulp and paper, mining and other industries for local catalytic wastewater treatment, absorption and catalytic treatment of gas emissions, biological treatment and catalytic wastewater treatment, for catalytic disinfection of water in industry and utilities, as well as in some technological processes, for example, the catalytic oxidation of sodium sulfide I white liquor, the catalytic process intensification oxygen-alkaline bleaching and others.

Known heterogeneous catalyst on a carrier - high pressure polyethylene (LDPE) containing pyrite cinder - 40-50%. This catalyst has high activity in the oxidation processes of sulfur, organosulfur and organic compounds, but does not provide the selectivity of the process / 1 /.

Known heterogeneous supported catalyst - LDPE, containing manganese oxide 23-25%, chromium oxide 3-5%, molybdenum oxide 5-7% and nickel oxide 3-5%, intended for use in the process of biochemical wastewater treatment / 2 /. The catalyst has a low activity and selectivity.

The closest to the achieved result is a heterogeneous catalyst on a LDPE carrier containing a pyrite cinder of 40-50%, cobalt phthalocyanine - 0.5-1.0%. The specified catalyst has a high selectivity in the oxidation processes of sulfur, organic and organosulfur compounds, but it provides low activity, causing a long contact time of the cleaning process, and requires relatively large structures and operating costs / 3 /.

To eliminate these drawbacks, a catalyst is proposed which contains oxides and / or hydroxides and / or spinels of metals of variable valency as an active component, and, in addition, a modifying additive, which uses organic bases and / or heteropoly acids, and / or carbon-containing material on a carrier of polyethylene, polypropylene or polystyrene, or another polymer with the following content of catalyst components, mass fraction in%:

active ingredient 15-50

modifying additive 0.5-20

carrier rest

Distinctive features of the proposed catalyst are:

- the composition of the active component, which is a composition of oxides and / or hydroxides, and / or spinels of metals of variable valency;

- the presence in the composition of the modifying additive, which is used as an organic base and / or heteropoly acids, or carbon-containing material;

- along with the known carrier - LDPE, it is possible to use other polymers, in particular polystyrene, polypropylene.

The proposed catalyst, in comparison with the prototype, is more active in the process of liquid-phase oxidation of inorganic and organic compounds (oil products, fatty acids, alcohols, aldehydes, ketones, phenol and its homologues and their oxidation products), nitrogen, phosphorus, sulfur and carbon-containing compounds (hydrogen sulfide, sulfides, sulfites, mercaptans, sulfur dioxide, nitrogen oxides, heptyl and its decomposition products, carbon monoxide, etc.) and microflora disinfection in a wide range of initial concentrations at pH 7-12. This is the basis for the use of a catalyst in the processes:

- wastewater treatment and gas emissions by liquid phase oxidation and catalytic oxidation to carbon dioxide, sulfur dioxide and water;

- biocatalytic wastewater treatment;

- adsorption-catalytic treatment and purification of wastewater and drinking water;

- disinfection of wastewater and drinking water;

- oxidation of sodium sulfide white liquor.

The use of thermally more stable carriers makes it possible to increase the operating temperature range of the catalyst, which expands the possibilities of using the catalyst and simplifies its operation. In addition, the introduction of a modifying additive in the carrier allows you to get the catalyst in the form of granules of the desired shape. Changing the composition of the active component and introducing a modifying additive into the composition of the catalyst allows you to change the Z-potential of the surface, thereby increasing the overall activity of the catalyst in redox processes and giving the catalyst surface additional specific properties - high retention capacity for suspended impurities and antibacterial activity are acquired, etc. e. the scope is significantly expanded.

Catalytic activity is closely related to the adsorption activity of the catalyst surface. A preliminary stage of catalysis is the adsorption of oxygen molecules and an oxidizable substance (substrate) on the surface of the catalyst. In this case, the adsorbed oxygen molecules and the substrate, especially in the presence of polar groups, are in a certain way oriented towards the surface of the catalyst. Emerging surface compounds are characterized by increased reactivity. The increase in reactivity is due to the nature of the intermediate interaction of the reacting substances with the catalyst.

The surface of the catalyst, due to the composition of the active component, the hydrophobic properties of the carrier and the introduction of a modifying additive, has a more specific ability to adsorb oxygen compared to the prototype both from the liquid phase and from air during aeration of the liquid phase. The concentration of oxygen (in activated form) on the surface of the catalyst significantly exceeds its concentration in the liquid phase. Moreover, the total oxygen content in the liquid phase in the presence of a catalyst is significantly higher than in the absence of a catalyst under the same aeration conditions.

The active sites of the Me complex catalyst are capable of reversibly oxygenating in aqueous solutions and activating coordinated O ₂ in the inner sphere of the metal ion by transferring the electron density from the central metal ion to O ₂ . As a result, oxygen acquires the properties of superoxide ions O ₂ ^- and O ^{2 -} or peroxide ion O ₂ ^2- .

An increase in the reactivity of coordinated molecular oxygen by metal ions of a catalyst can be reduced to either facilitating a thermodynamically favorable four-electron transfer with a decrease in the total redox potential of the oxygen reduction reaction:

O ₂ + 4H ⁺ + 4e ^- → 2H ₂ O,

equal to 1.23 V, or to a significant decrease in the activation energy of free triplet O ₂ molecules, after translating them into a singlet state after coordination, which facilitates reactions with singlet substrate molecules.

It is also possible to use a catalyst in some technological processes, for example, the catalytic oxidation of sodium sulfide of white liquor in order to obtain a polysulfide cooking solution in pulp and paper industry, as well as in pulp bleaching processes.

Formation on the surface of the catalysts in the form of activated oxygen superoxide ions O ₂ ^- and O ^2-, or peroxide ion O ^2- ₂ causes also the antibacterial activity of the catalysts, which used water disinfection processes. The resulting superoxide ions interact with water to form H ₂ O ₂ and radical ions of the composition HO ₂ ^• , HO ^• . These radical ions have a significantly higher rate of diffusion into the cells of microorganisms through cell membranes and are more active in reactions with enzymes inside cells compared to molecular oxygen. After the termination of the contact of water with the surface of the catalyst, the radical ions are rapidly neutralized as a result of their recombination.

The catalytic disinfection process is carried out by filtering water through a catalyst bed. It was found that for effective and sustainable disinfection of drinking water, it is enough after catalytic treatment to perform additional chlorination at a chlorine flow rate of 0.05-0.10 mg / dm ³ . With this disinfection technology, a 10-15-fold reduction in chlorine consumption is achieved depending on the initial water quality. In addition, the presence of free chlorine in purified water due to the interaction of the latter with the radical ions HO ₂ ^• and HO ^• with the formation of HOCl is excluded. The presence of HOCL allows you to increase the exposure time of the disinfecting agent.

Due to the newly acquired specific surface properties, the catalyst also has a high absorption (retention) ability with respect to suspended impurities. Due to this, the catalyst can be used in wastewater post-treatment processes by the filtering method, while providing COD post-treatment due to oxidation of organic impurities, as a catalyst, and post-treatment according to suspended solids, while working as an adsorbent due to specific surface properties; and, in addition, providing disinfection by coli index from 10 ⁶ -10 ⁷ individuals / dm ³ to 10 ³ individuals / dm ³ .

The introduction of a modifying additive into the active component ensures a strong fixation of the active component in the catalyst mass, which provides stable activity for a long time, and also increases the plasticity of the catalyst mass during molding, and as a result, high quality of the catalyst is observed in terms of granulation composition and density and mechanical indicators durability. Mechanical wear of the carrier on the surface of the catalyst granules during operation does not lead to a loss of activity, because the inner layers of the catalyst granules come into operation. The service life of the proposed catalyst ranges from 3 to 7 years, depending on the parameters of the catalytic process: temperature, pH, amount of air supplied, etc. If necessary, the catalyst can be made in the form of granules of any size, Rashig rings, etc.

Example 1

The catalyst composition (mass fraction in%):

active component 40

modifying additive 10

carrier 50

manufactured by the following technology

The active component, which is a mixture of oxides and / or hydroxides and / or spinels of metals of variable valency (i.e., this catalyst is multifunctional and provides oxidation of organic, sulfur and nitrogen compounds), is pre-dried at a temperature of 110 ° C for 4 hours and grinding in a ball mill for 2 hours.

The mixture of the active component and the carrier - LDPE, the formation of catalyst granules is carried out on an industrial thermoplastic apparatus for granulation with a minimum mixer load of 60 kg.

The mixing of the catalyst components is carried out in a high-temperature mixer, which is included in the kit of the thermoplastic apparatus, at the melting temperature of the carrier polymer. The polymer carrier is loaded into the mixer — high pressure polyethylene — in an amount of 30.0 kg (50%) and a modifying additive (heteropoly acid) in an amount of 6.0 kg (10%) and mixed at a temperature of 118-122 ° C for 30- 35 minutes Then add the active ingredient in an amount of 24.0 kg (40%). Stirring is continued for another 30-60 minutes. After mixing, the resulting mass is automatically fed into a screw extruder, where it is formed into granules using special dies. For research, catalyst samples were prepared in the form of spherical granules 10-12 mm in size.

In a similar manner, a series of samples of polyfunctional polymer catalysts is prepared that provides oxidation of organic, sulfur and nitrogen compounds (the active base contains oxides and / or hydroxides of metals of variable valency). The catalysts of this series contain components (active base, modifying additive and carrier) in various mass ratios - the compositions of the samples are presented in table. 1. Among them there are samples characterized by a large and lower content of the active base and modifying additives than provided by the present invention, No. 1-7, 13, 14, 20, 21, 27, 28, 34, 35, 41-47.

Example 2

Test the mechanical strength of the granules obtained in example 1, samples of polymer catalysts. The compressive strength of granules is determined according to GOST 473.6-77. The test results for the samples are presented in table. 1. An analysis of the results shows that when the content of the active base is more than 50% (sample No. 42-47) or a modifying additive more than 20% (sample No. 6, 13, 20, 27, 34, 41), a decrease in the mechanical strength of the granules catalyst. That is, the introduction of an active base or modifying additive in an amount greater than that provided by the present invention leads to a decrease in the mechanical strength of the granules.

Example 3

Test the activity of samples of the polymer catalyst in the process of oxygen oxidation of sulfide, methyl mercaptide, sulfite ions and the amount of organic compounds in solutions in laboratory conditions. When oxidizing according to the proposed method, the catalysts obtained in examples 1 and 2 were used, with the exception of those that were rejected according to the results of mechanical strength tests in example 2.

The experiments are carried out on real sulfide wastewater of Angarsk Petrochemical Company OJSC (ANKhK OJSC) with sulfide ions content of 900-1200 mg / dm ³ (pH 10.2-11.0), COD 1200-1500 mgO / dm ³ . Also in the experiments using model solutions containing methyl mercaptide ions 200-350 mg / DM ³ (pH 9.5-10.0) and sodium sulfite 800-950 mg / DM ³ (pH 8.0-8.5). Model solutions are prepared by adding methyl mercaptan and sodium sulfite in distilled water in calculated amounts to obtain a given concentration. The pH of the model solutions was adjusted by adding a 10% NaOH solution. To obtain a solution containing all three of these components, an additive of methyl mercaptan and sodium sulfite in the calculated amounts is introduced into real sulfide wastewater with a content of sulfide ions of 900-1200 mg / dm ³ and a COD of 200-1500 mgO / dm ³ .

The concentration of H ₂ S and mercaptans in the initial and oxidized waters is determined by the potentiometric method according to GOST 22985-75, the concentration of sulfites by the iodometric method and COD by the titrimetric method PND F 14.1.2.100-97 described in / 4 /. The oxidation process according to the proposed method is carried out in a batch laboratory reactor. Each catalyst sample was loaded into the laboratory reactor in layers, between which restrictive grids were installed, which ensured good mass transfer.

The volume fraction of the catalyst sample in the oxidation reactor is 50% (including free volume). Air is supplied to the reactor from below using a dispersant. The oxidation process of sulfur and organic compounds is carried out at the following parameters: temperature - 90 ° C; pressure - 0.3 MPa; specific air consumption - 10 m ³ / m ³ , oxidation time - 5 minutes

An analysis of the results of testing the activity of the samples shows that all samples of polymer catalysts with an active base content of 15-50% and a modifying additive of 0.5-20% have activity in the oxidation of sulfide ions - at least 99.5%, methyl mercaptide ions - not less than 99.9%, sulfite ions - at least 99.5%, COD - at least 90.0%.

With a decrease in the amount of the active component of less than 15% and a modifying additive of less than 0.5%, a decrease in the activity of samples in all components below the indicated level is noted — arr. No. 1-5, 7, 14, 21, 28, 35. Table 2 presents the results of tests of the activity of samples of the proposed catalyst of optimal composition.

Example 4

Test the activity of samples of polymer catalysts in the process of absorption-catalytic gas purification from SO ₂ , H ₂ S, mercaptans. When oxidizing according to the proposed method, the catalysts obtained in examples 1 and 2 were used, with the exception of those that were rejected according to the results of mechanical strength tests in example 2.

Testing the activity of the proposed catalyst for the purification of gases from sulfur compounds is carried out on real gas mixtures (TPP-10) in a continuous reactor in the film mode of the absorption-catalytic process. The absorbent, which is used as water, is fed into the reactor from above, gas in countercurrent flow from below. The activity of the catalyst is evaluated by the degree of purification of the gas mixture from sulfur compounds; for this, the concentration of compounds in the gas mixture at the inlet and outlet of the oxidation reactor is determined.

The concentration of H ₂ S and mercaptans is determined by the potentiometric method according to GOST 22985-75, by the SO ₂ method described in (4).

Below are the parameters of the process of absorption and catalytic oxidation of sulfur oxide, sulfides, mercaptans in a gas at the indicated initial concentrations.

Concentration, g / l:

sulfur oxide 0.01-4.5

hydrogen sulfide 0.01-3.0

mercaptans 0.01-2.5

absorbent pH 7.1-8.2

Temperature, C 60-80

Pressure, MPa atmospheric

Specific air consumption, l / l 10.5-50

Absorbent consumption, l / l 0.2-1.0

Contact time gas: catalyst, from 0.8-1.5

The ratio of the consumption of absorbent to gas consumption 0,00015

Gas velocity, m / s 0.14

The concentration of oxygen in the gas,% 10

An analysis of the results of testing the activity of the samples shows that all samples of polymer catalysts with an active base content of 15-50% and a modifying additive of 0.5-2% have an activity of 99.9% in the process of oxidation of sulfur oxide, and at least 99.7% in hydrogen sulfide, mercaptans - not less than 99.9%. Moreover, samples of ceramic catalysts are more active in comparison with samples of polymer catalysts of the same composition. With a decrease in the amount of the active component (less than 15%) and the modifying additive (less than 0.5%), a decrease in the activity of the samples for all components below the indicated level — arr. No. 1-5, 7, 14, 21, 28, 25.

Table 3 presents the test results of the activity of the samples of the proposed catalyst of optimal composition.

Example 5

Test the activity of samples of polymer catalysts prepared according to Example 1 in the process of biocatalytic wastewater treatment (with the exception of samples that were rejected in terms of mechanical strength in Example 2).

Testing of catalyst samples on a polymer carrier is carried out in a laboratory biocatalytic reactor, which simulates a two-stage bioreactor, which is two vinyl-plastic cylindrical columns, into which purified wastewater with free-floating activated sludge is poured in an amount of 1.5 g / dm ³ and metal mesh containers are lowered, which load the catalysts on a polymer carrier. In the container load samples of the catalysts in an amount corresponding to the ratio of catalyst: wastewater = 1: 75. The oxidation is carried out in static mode at a temperature of 18-22 ° C. The process of biocatalytic wastewater treatment is carried out in two stages:

Stage 1 - wastewater mixed with activated sludge is poured into the first column and oxidized for 4 hours with aeration with air at a specific flow rate of 8.0 m ³ / m ³ ;

Stage 2 - after the first stage of oxidation, the waste water is transferred from the first oxidation column to the second and oxidation immediately begins under anaerobic conditions with mechanical stirring also for 4 hours.

For the experiments using real wastewater entering the biological treatment plant (BF) of ANKhK OJSC, with a COD concentration of 190-215 mgO / dm ³ , ammonium nitrogen 20-30 mg / dm ³ , nitrites 4-6 mg / dm ³ , nitrates 25-35 mg / dm ³ , phenols 18-22 mg / dm ³ , petroleum products 8-15 mg / dm ³ , SAS 0.7-1.2 mg / dm ³ , hydrogen sulfide 3.0-5.0 mg / dm ³ , as well as biocenoses formed in the process of adaptation of activated sludge to the wastewater of BFW of ANKhK OJSC.

An analysis of the activity test results shows that all samples of polymer catalysts with an active base content of 15-50% and a modifying additive of 0.5-20% have high activity in the process of biocatalytic purification: 99.9-100% for hydrogen sulfide, 99 for ammonium nitrogen , 5-100%, nitrites - 79-82%, nitrates - 80-82%, COD - 96-98%.

With a decrease in the amount of the active component of less than 15% and a modifying additive of less than 0.5% (samples No. 1-5, 7, 14, 21, 28, 35), there is a decrease in the efficiency of the cleaning process for all indicators.

The results of testing the activity of samples of polymer catalysts in the process of biocatalytic purification by components: hydrogen sulfide, ammonium nitrogen, nitrites, nitrates and COD are presented in table 4.

Example 6

Test the effectiveness of the proposed method for producing a polysulfide cooking liquor using samples of catalysts prepared according to example 1.

The experiments are carried out on real white sulfate liquor used for sulfate pulping at OJSC “Baikal Pulp and Paper Mill”, of the following composition:

The total alkalinity of 105.0-117.0 g / DM ³ units. Na ₂ O;

NaOH 76.0-78.0 g / dm ³ units Na ₂ O;

Active alkalinity 95.0-108.0 g / dm ³ units. Na ₂ O;

Sulfide 24-35%;

Sulfur thiosulfate 0.8-1.3 g / DM ³ units Na ₂ O;

Polysulfide sulfur 0.4-0.5 g / dm ³ units Na ₂ O;

Suspended impurities Not more than 80 g / dm ³ .

The process of obtaining a polysulfide cooking solution according to the proposed method is carried out in a batch laboratory reactor. Each catalyst sample is loaded into the laboratory reactor in layers, between which restrictive meshes are installed. The volume fraction of the catalyst sample in the oxidation reactor is 50% (including the free volume of the catalyst). The feed of white liquor and air into the reactor is carried out by direct flow from the bottom of the reactor using a dispersant, which provides good mass transfer of the gas and liquid phases.

The process of oxidation of white liquor is carried out at the following parameters: temperature 80-85 ° C; specific air consumption 8 m ³ / m ³ , oxidation time (fictitious) - 15 minutes

The experiments are carried out without preliminary purification of white liquor from suspended impurities. The efficiency of the oxidation process is evaluated by the following indicators:

- the degree of oxidation of sodium sulfide;

- the concentration of polysulfides in oxidized liquor;

- selectivity of the oxidation process.

The content of sulfide and polysulfide sulfur is determined by the methods described in / 4 /. The results of testing the effectiveness of the proposed method for producing polysulfide liquor on samples of a polymer catalyst are shown in table 5. Analysis of the results of testing the activity of the samples shows that all samples of a polymer catalyst with an active base content of 15-50% and a modifying additive of 0.5-20% provide: oxidation state sodium sulfide - not less than 73%, the concentration of polysulfide sulfur in oxidized liquor - not less than 6.5 g / dm ³ and the selectivity of the process is not less than 70%. These indicators are achieved using white sulfate liquor of low sulfide content - 29-31%. Moreover, samples of ceramic catalysts are more active in comparison with samples of polymer catalysts of the same composition. Polysulfide liquor with these indicators is the most suitable for polysulfide pulping.

With a decrease in the amount of the active component of less than 15% and a modifying additive of less than 0.5%, a decrease in the activity of samples in all components below the indicated level is noted — arr. No. 1-5, 7, 14, 21, 28, 35.

The above examples show that the use of the proposed catalyst in industry, due to its higher activity, will increase the efficiency of wastewater treatment and gas emissions, reduce the size of technological devices and the consumption of catalyst, auxiliary products (steam, air), electricity.

The introduction of a modifying additive in the carrier optimizes the manufacturing process of the granular catalyst and allows one to obtain catalyst samples on different media: low-melting - PVD and thermally more stable - polypropylene and polystyrene. In processes where a temperature of 40-90 ° C is used and there is no danger of emergency overheating of the catalyst, the use of LDPE catalysts is appropriate. In processes such as the purification of sulfur-alkaline wastewater from the oil refining process and the oxidation of sodium sulfide white liquor in order to obtain polysulfide liquor, the use of catalysts on more thermally stable carriers is more acceptable. Here, at high initial concentrations of sulfur compounds, in order to achieve a sufficient process speed and reduce the overall dimensions of the oxidation column and catalyst consumption, the oxidation is carried out at a temperature of 95-120 ° C at an overpressure in the column.

In the case of LDPE, an improvement in the quality of the finished catalyst in terms of mechanical strength leads to an increase in the service life of the catalyst by 20-30% compared to samples made without the use of a modifying additive.

Thus, the proposed polymer-supported catalyst provides the greatest efficiency in the purification of gases and water for a wide range of ingredients, which is not available for all known similar catalysts.

Claims (2)

1. A heterogeneous catalyst for the oxidation of inorganic and / or organic compounds on a polymer carrier, containing an active component on a polymer carrier, characterized in that the catalyst contains oxides and / or hydroxides and / or spinels of metals of variable valence as an active component and an additional modifying additive , which use organic bases, and / or heteropoly acids, and / or carbon-containing material in the following content of catalyst components, wt.%: Active ingredient 15-50 Modifying additive 0.5-20 Media Else 2. The heterogeneous catalyst according to claim 1, characterized in that polypropylene, polystyrene or another polymeric carrier are also used as a polymer carrier.