RU2252208C1 - Method for utilization of chlorine-containing waste - Google Patents

Abstract

FIELD: chemistry, in particular utilization of chlorine-containing waste.

SUBSTANCE: claimed method includes passing of organochlorine compound vapors blended with oxygen-containing reaction gaseous mixture through catalyst layer providing oxidation of starting organochlorine compounds. Said catalyst represents geometrically structured system from microfibers with length of 5-20 mum. Catalyst has active centers which are characterized by presence of absorption band in absorbed ammonia IR-spectrum with wave number ν = 1410-1440 cm^-1; contains platinum group metal as active ingredient; and glass fiber carrier. Said carrier in NMR²⁹Si-spectrum has lines with chemical shifts of -100±3 ppm (Q³-line) and -110±3 ppm (Q⁴-line) in integral intensity ratio of Q³/Q⁴ = 0.7-1.2; in IR-spectrum it has hydroxyl absorption band with wave number ν = 3620-1440 cm^-1 and half-width of 65-75 cm^-1; has specific surface, measured by BET using argon thermal absorption: S_Ar = 0.5-30 m²/g; surface area, measured by alkali titration: S_Na = 10-250 m²/g, wherein S_Na/S_Ar = 5-30.

EFFECT: selective oxidation of starting organochlorine compounds to safe and easily utilizing substances without toxic by-product formation.

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Description

The invention relates to the field of chemistry, and in particular to methods for the disposal of chlorine-containing waste, and can be used to clean gaseous and liquid emissions from toxic organochlorine impurities, primarily chlorohydrocarbons.

A known method for the disposal of chlorine-containing compounds, including the homogeneous oxidation of organochlorine compounds with atmospheric oxygen in a lined furnace at a temperature of at least 600 ° C (US Patent No. 4018879, priority from 06/21/76, publ. 19.04.77, IPC C 01 B 7/00 )

The disadvantage of this method is the low efficiency of the conversion of the original chlorine-containing waste into non-toxic or easily utilizable compounds (HCl, H ₂ O and CO ₂ ), as well as the formation of a significant amount of hazardous oxidation by-products (elemental chlorine, CO, phosgene, dioxins, nitrogen oxides).

Known methods for the disposal of organochlorine wastes based on the oxidation of organochlorine impurities in the presence of a catalyst. In particular, methods are known including the use of catalysts based on zirconium, vanadium, manganese, cobalt or cerium oxides, as well as at least one of the platinum group metals (US Patent No. 5578283, priority from 12.30.94, publ. 26.11.96, IPC C 01 B 7/00), based on transition metals deposited on a zeolite carrier (US Patent No. 3989806, priority 10.02.75, publ. 02.11.76, IPC C 01 B 7/02), based on carbon-containing carriers ( US Patent No. 5344630, priority dated 06/28/91, published on 09/06/94, IPC B 01 J 8/02, C 01 B 7/01) and on the use of alkaline vanadium salts (US Patent No. 5075273, priority from 11.28.89, published on 12.24.91, IPC B 01 J 21/04, B 01 J 21/08, B 01 J 23/04, B 01 J 21/08).

The use of these catalysts increases the overall efficiency of the oxidation of organochlorine impurities, however, the formation of harmful oxidation by-products is also possible. In addition, a common disadvantage of the known known methods is the low stability of said catalysts and their rapid deactivation, which practically excludes the possibility of their industrial use.

A known method for the joint catalytic oxidation of organic and organochlorine impurities, comprising passing a reaction gas mixture of organochlorine impurities with oxygen in series through two catalyst beds, the first of which uses a catalyst based on a carrier with low acidity, and in the second a catalyst based on a carrier with high acidity ( US patent No. 5451388, priority dated 01/21/94, publ. 09/19/95, IPC B 01 D 50/00, B 01 D 53/00). The use of such a combination of catalysts provides highly efficient oxidation of both organic and organochlorine impurities, while significantly reducing the number of harmful by-products (CO, phosgene, dioxins, nitrogen oxides).

The disadvantage of this method is that its implementation does not exclude the undesirable formation of difficult to utilize and highly toxic elemental chlorine.

Closest to the proposed one is a method comprising passing the vapors of organochlorine compounds in the composition of an oxygen-containing reaction gas mixture through a catalyst bed providing oxidation of the initial organochlorine compounds (US Patent No. 4423024, priority from 05/26/82, publ. 12/27/83, IPC 01 B 21 / 20, C 01 V 7/01). The high selectivity of the catalytic oxidation of organochlorine impurities in hydrogen chloride, water and carbon dioxide without the formation of harmful side impurities in the known method is achieved through the use of catalysts based on acid-resistant zeolite molecular sieves.

The disadvantages of this method are the insufficiently high stability of zeolite catalytic systems in the presence of water vapor, which leads to their rapid deactivation and limited service life, as well as their relatively low catalytic activity.

The authors were tasked with developing a method for the disposal of chlorine-containing wastes that provides high efficiency for the oxidation of organochlorine impurities in HCl, H ₂ O and CO ₂ without the formation of elemental chlorine and other harmful and difficult to recycle impurities (CO, phosgene, dioxins, etc.), while ensuring high stability and high catalyst performance.

The problem is solved in that in a method for the disposal of organochlorine compounds, including the passage of organochlorine vapor in the composition of an oxygen-containing reaction gas mixture through a catalyst bed that oxidizes the initial organochlorine compounds, a catalyst is used, which is a geometrically structured system of microfibers with a diameter of 5-20 microns, having active centers, which are characterized in the IR spectra of adsorbed ammonia by the presence of an absorption band from the waves numbers in the range ν = 1410-1440 cm ^-1 , containing the active component, which is one of the metals of the platinum group, and a glass fiber carrier, characterized by the presence in the NMR spectrum of ²⁹ Si lines with chemical shifts of -100 ± 3 ppm. (line Q ³ ) and -110 ± 3 ppm. (line Q ⁴ ) with a ratio of the integrated intensities of the lines Q ³ / Q ⁴ 0.7-1.2, in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of ν = 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1 , having a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g, surface area measured by the method of alkaline titration, S _Na = 10-250 m ² / g at a ratio of S _Na / S _Ar = 5-30. The active component of the catalyst may be at least one of the metals of the platinum group, in particular platinum. The fiberglass catalyst carrier can be structured in the form of either a non-woven or pressed material such as cotton wool or felt, or filaments with a diameter of 0.5-5 mm, or a woven material of threads with weaving such as satin, canvas, lace with a mesh diameter of 0.5-5 mm .

The technical effect of the proposed method lies in the possibility of effective selective oxidation of the starting organochlorine compounds to easily utilizable (hydrogen chloride) and harmless (carbon dioxide, water) substances without the formation of harmful side impurities (elemental chlorine, phosgene, CO, dioxins, etc.). Moreover, the method is characterized by improved technical and economic characteristics due to the increased activity of the catalyst, its stability and high resistance to deactivation, including in the presence of water vapor.

To dispose of organochlorine compounds, a reaction mixture containing at least a pair of these organochlorine compounds and oxygen is passed through a catalyst bed containing the active component and a glass fiber carrier, and the IR spectra of adsorbed ammonia on the specified catalyst have characteristic absorption bands with wave numbers in the ν range = 1410-1440 cm ^-1 , and at least one of the metals of the platinum group, in particular platinum, is used as the active component. The presence of these bands in the IR spectra of adsorbed ammonia is an unambiguous evidence of the presence of specific active centers on the catalyst surface that provide high selectivity for the oxidation of organochlorine impurities in HCl, H ₂ O, and CO ₂ without the formation of elemental chlorine and other harmful and difficult to utilize impurities (CO, phosgene, dioxins, etc.), as well as high activity and stability of the catalyst. The creation of such centers can be carried out by purposefully modifying the surface of the catalyst in various ways at the stage of its preparation.

For the implementation of the method using a catalyst formed in the form of flexible, permeable to the flow of the reaction mixture, fiberglass structures made in the form of woven or pressed materials. This structuring simplifies the placement and fixing of the catalyst layer in the catalytic reactor and prevents the entrainment of microfibers of the catalyst with the reaction stream.

Utilization of organochlorine compounds according to the described method provides a high selectivity for the oxidation of the starting organochlorine compounds to easily utilizable (hydrogen chloride) and harmless (carbon dioxide, water) substances without the formation of harmful side impurities (elemental chlorine, phosgene, CO, dioxins, etc.). The only chlorine-containing reaction product - hydrogen chloride - can be easily disposed of as a valuable industrial product - salable hydrochloric acid. The catalyst is characterized by increased activity, stability and high resistance to deactivation, including in the presence of water vapor. At the same time, mechanical stability of the catalyst layer is ensured, which allows one to create various types of catalyst layers (axial, radial, etc.) and arrange the catalytic reactor in any geometric orientation (vertically, horizontally, etc.), which significantly increases manufacturability and extends the application of the method.

Example 1

Dichloroethane is recycled, for which dichloroethane vapors are mixed with air (the volume concentration of dichloroethane is 3.5%) and passed through a catalyst bed. The catalyst contains a glass fiber carrier (structured in the form of a woven material) and an active component (platinum), and during preparation the catalyst is modified so that the IR spectra of adsorbed ammonia on the specified catalyst have characteristic absorption bands with wave numbers in the range of ν = 1410-1440 cm ^-1 . At a temperature of 500 ° C and a volumetric feed rate of the reaction mixture of 18 thousand hour ^-1 , a complete conversion of dichloroethane to hydrogen chloride, water vapor and carbon dioxide is achieved. Other oxidation products (products of incomplete oxidation, elemental chlorine, CO, phosgene, dioxins) are not detected at all when the analysis sensitivity threshold is not higher than 1 ppm. The experiment under these conditions for 6 hours shows the absence of a decrease in the activity and selectivity of the catalyst.

The use of a similar unmodified catalyst (which does not have these bands in the IR spectra of adsorbed ammonia) leads to the formation of significant quantities of undesirable by-products (chlorovinyl, CO). The use of other known catalysts is also associated with the formation of undesirable by-products, in addition, they undergo severe deactivation in these conditions.

Example 2

Chlorobenzene and butyl chloride are disposed of under similar conditions. At temperatures of 400 ° C, their complete conversion to hydrogen chloride, water vapor and carbon dioxide is achieved. The formation of other oxidation products, as well as catalyst deactivation, was not detected.

Example 3

Dichloroethane, chlorobenzene or butyl chloride is recycled, as in Example 1, but the vapors of these compounds are mixed with air containing 3.1% water vapor, and then passed through a layer of fiberglass catalyst. Throughout the specified range, the introduction of water vapor does not lead to a change in the activity of the catalyst and the composition of the resulting reaction products.

Example 4

The same as in example 1, but using a catalyst in which the glass fibers are structured in the form of a non-woven pressed felt. Results similar to those described are achieved.

Claims (3)

1. The method of disposal of organochlorine compounds, comprising passing the vapors of organochlorine compounds in the composition of the oxygen-containing reaction gas mixture through a catalyst bed that provides oxidation of the starting organochlorine compounds, characterized in that they use a catalyst, which is a geometrically structured system of microfibers with a diameter of 5-20 microns, having active centers that are characterized in the IR spectra of adsorbed ammonia by the presence of an absorption band with wave numbers in azone ν = 1410-1440 cm ^-1, containing an active component which is one of the platinum group metals, and glass fiber support, characterized by the presence in the ²⁹ Si NMR spectrum of lines with chemical shifts -100 ± 3 ppm (line Q ³ ) and -110 ± 3 ppm. (line Q ⁴ ) with a ratio of the integrated intensities of the lines Q ³ / Q ⁴ from 0.7 to 1.2, in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of ν = 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1 having a specific surface area measured by the BET method for thermal desorption of argon, s _Ar = 0.5-30 m ² / g, surface area measured by the method of alkaline titration, S _Na = 10-250 m ² / g at a ratio of S _Na / S _Ar = 5-30. 2. The method according to claim 1, characterized in that the active component of the catalyst is platinum. 3. The method according to claims 1 and 2, characterized in that the glass fibers of the catalyst are structured in the form of either non-woven or pressed material such as cotton wool or felt, or material woven from threads with a diameter of 0.5-5 mm.