阅读说明：本技术 氯化氢光催化氧化制备氯气的方法及装置 (Method and device for preparing chlorine by hydrogen chloride photocatalytic oxidation ) 是由 王农跃 沙艳松 章冬霞 李斌 于 2019-11-27 设计创作，主要内容包括：本申请涉及氯化氢催化氧化领域,公开了一种氯化氢光催化氧化制备氯气的方法及装置,本申请通过将反应器分隔为光照射区和无光区,所述光照射区能够被光辐射到,而无光区不能够被光辐射到,所述光的波长为150nm～278nm中的任一值或范围,所述光照射区和无光区之间的气体能够流通,从而有效避免产物气体在光照条件下继续发生逆光解,提高产率。(The application relates to the field of hydrogen chloride catalytic oxidation, and discloses a method and a device for preparing chlorine through hydrogen chloride photocatalytic oxidation, and the application separates a reactor into a light irradiation area and a no light irradiation area, wherein the light irradiation area can be irradiated by light, the no light irradiation area can not be irradiated by light, the wavelength of light is any value or range from 150nm to 278nm, and gas between the light irradiation area and the no light irradiation area can circulate, so that the product gas is effectively prevented from continuously generating reverse photolysis under the light irradiation condition, and the yield is improved.)

1. A process for the photocatalytic oxidation of hydrogen chloride to chlorine, characterized in that a hydrogen chloride-containing gas stream and an oxygen-containing gas stream for oxidizing the hydrogen chloride-containing gas stream are supplied to a reactor, and hydrogen chloride and oxygen react under light irradiation conditions to form a mixture comprising at least chlorine and water, the reactor being divided into a light irradiation zone which can be irradiated with light and a non-light irradiation zone which cannot be irradiated with light, gas being allowed to pass between the light irradiation zone and the non-light irradiation zone, and the wavelength of the light being any value or range from 150nm to 278 nm.

2. The process for the photocatalytic oxidation of hydrogen chloride to chlorine according to claim 1, wherein the wavelength of the light is any value or range from 240nm to 278 nm.

3. The process for preparing chlorine by photocatalytic oxidation of hydrogen chloride according to claim 1 or 2, wherein the water produced by the reaction and chlorine gas are liquefied while the hydrogen chloride and oxygen gas are kept in a gaseous state, and liquid chlorine and liquid water are discharged from the reactor.

4. The process for preparing chlorine by photocatalytic oxidation of hydrogen chloride according to any one of claims 1 or 2, wherein the water produced by the reaction is liquefied while the chlorine, hydrogen chloride and oxygen remain in a gaseous state, and the liquid water is discharged from the reactor.

5. The method for preparing chlorine gas by photocatalytic oxidation of hydrogen chloride according to any one of claims 1 or 2, wherein a series process of n-stage reactors is adopted, each stage reactor is divided into a light irradiation zone and a no light zone, water in the 1 st to (n-1) th stage reactors is liquefied and discharged from the reactors, chlorine gas, hydrogen chloride and oxygen gas are kept in a gas state, and the chlorine gas, the hydrogen chloride and the oxygen gas are sequentially fed from the previous stage reactor to the next stage reactor, so that the chlorine gas in the n-stage reactor is liquefied, the hydrogen chloride and the oxygen gas are kept in a gas state, wherein n is greater than or equal to 2, and preferably n is 3-5.

6. The method for preparing chlorine gas by photocatalytic oxidation of hydrogen chloride according to any one of claims 1 or 2, wherein the feed gas temperature of hydrogen chloride and oxygen is any value or range from 0 ℃ to 50 ℃; preferably, the temperature of the feed gas of the hydrogen chloride and the oxygen is any value or range of 20-30 ℃.

7. The process for preparing chlorine by photocatalytic oxidation of hydrogen chloride according to any one of claims 1 or 2, characterized in that the temperature of the light irradiation zone is in the range of 0 ℃ to 200 ℃, preferably in the range of 20 ℃ to 140 ℃.

8. The process for preparing chlorine by photocatalytic oxidation of hydrogen chloride according to claim 1, wherein the feed gas is introduced directly into the light irradiation zone.

9. An apparatus for preparing chlorine by photocatalytic oxidation of hydrogen chloride, comprising a reactor provided with a gas feed port, a liquid discharge port, and a gas discharge port, wherein a light source is provided inside the reactor, and the reactor is partitioned into a light irradiation region capable of being irradiated with light and a non-light irradiation region incapable of being irradiated with light by a gas-permeable and non-light-permeable structure, and wherein gas can flow between the light irradiation region and the non-light irradiation region.

10. The apparatus for the photocatalytic oxidation of hydrogen chloride for producing chlorine according to claim 9, wherein the structure that is permeable to air and impermeable to light is a louver structure; or the double-layer plate structure is characterized in that the inner layer plate and the outer layer plate of the double-layer plate are both provided with staggered holes; or a structure composed of a material which is air-permeable and light-proof.

Technical Field

The application relates to the field of hydrogen chloride catalytic oxidation, in particular to a method and a device for preparing chlorine through hydrogen chloride photocatalytic oxidation.

Background

Chlorine is an important chemical product and raw material, and is mainly applied to the fields of polyvinyl chloride, MDI, TDI, methane chloride, synthetic rubber, silicon materials, chlorofluorocarbons, building materials, medicines and the like. The utilization rate of chlorine element is about 50% in the production process, and the hydrogen chloride gas with the same volume is usually produced as a byproduct. The problem of the out-route of a large amount of byproduct hydrogen chloride becomes a common problem which restricts the sustainable development of the industry related to chlorine. The byproduct hydrogen chloride is made into chlorine and is put into the production chain again, so that a circular economic reaction system of chlorine element can be constructed.

The byproduct hydrogen chloride is converted into chlorine mainly through 3 typesThe process method is realized by an electrolytic method, a direct oxidation method and a catalytic oxidation method. The electrolysis method has the defects of high energy consumption, high impurity content of products and the like, and is not developed. The direct oxidation method is to use a strong oxidant such as NO₂、SO₃Or HNO₃/H₂SO₄The mixed acid as an oxidant directly oxidizes hydrogen chloride, has complex equipment, high product separation difficulty and relatively high energy consumption, and cannot be popularized. The typical process of the catalytic oxidation method mainly comprises a Deacon process, and compared with an electrolysis method and a direct oxidation method, the catalytic oxidation method has the advantages of low energy consumption, simplicity and easiness in operation, high per pass conversion rate and the like, and is widely considered to be the method which is most easy to realize industrialization at present. However, the catalytic oxidation method has a high reaction temperature, which often causes the activity of the catalyst to be reduced and the service life to be shortened, so that the catalyst needs to be replaced frequently, and the cost is high.

In order to be able to lower the reaction temperature and to allow the reaction to proceed towards the product end, WO2017194537a1 provides for heterogeneous photocatalytic oxidation of hydrogen chloride by UV radiation, producing a gas mixture composed of at least hydrogen chloride, oxygen and optionally other minor constituents, and passing it over a solid photocatalyst comprising at least one photoactive material, such as a transition metal or a transition metal oxide or a semiconductor material, and initiating the reaction on the surface of the catalyst by the action of UV radiation in a selective energy range. In this method, the hydrogen chloride conversion rate can reach 90% or more, but a solid photocatalyst is required.

RU2253607 continuously feeds a reaction mixture of air and hydrogen chloride to a flow type reactor to form an activation zone, wherein the hydrogen chloride is oxidized with oxygen at a temperature ranging from 25 to 30 ℃, the activation zone is formed by irradiating the reaction mixture in a specific region of the reactor with a mercury high pressure quartz lamp having a volumetric irradiation density of (10-40). times.10 at a pressure of not more than 0.1MPa^-4W/cm³. JPS5973405 irradiates with pulsed coherent light, gaseous hydrogen chloride is caused to pass through a photochemical reaction in the presence of oxygen and/or air to generate chlorine gas, or coherent light and incoherent light are alternately used or pulsed irradiation of coherent light is performed during irradiation with incoherent light. WO2006132561A1 production of chlorine by continuously supplying a gaseous mixture containing hydrogen chloride and oxygen in a flow-through reaction zone and oxidizing the hydrogen chloride by oxygen to form a target product, as oxygen for oxidizing the hydrogen chloride, having a wavelength of 165-270 nm and a density of (10-40). 10^-4W/cm³Is activated with ultraviolet irradiation, the pressure is kept at not more than 0.1MPa, or oxygen is activated under current irradiation of accelerated electrons having an energy of 100keV to 2 MeV.

The existing technology for oxidation by using photocatalytic hydrogen chloride can obtain higher conversion rate, but the feeding speed and pressure must be strictly controlled, and the heat balance of the reaction process is disturbed by overhigh or overlow feeding speed or pressure change, so that the conversion rate of the hydrogen chloride is obviously reduced. In the industrial production process, the realization of a larger conversion rate still has considerable difficulty and higher cost.

Disclosure of Invention

The present inventors have completed the present application in view of the above-mentioned shortcomings of the prior art. The application provides a method for preparing chlorine by photocatalytic oxidation of hydrogen chloride, which takes light as a catalyst and realizes high hydrogen chloride conversion rate by separating a reactor.

The inventor researches and discovers that the prior art hydrogen chloride photocatalytic oxidation method is difficult to realize industrialization, and has the main problem that H-Cl bond energy is larger than Cl-Cl bond energy, when hydrogen chloride is excited by using a light source irradiation method and the like to generate oxidation reaction, the product chlorine gas is also excited by light to generate hydrolysis reverse reaction with water, so that the chlorine gas is converted into raw material gas to influence the yield of the product.

Therefore, the application relates to a method for preparing chlorine by hydrogen chloride through photocatalytic oxidation, which adopts the following specific technical scheme: providing a hydrogen chloride-containing gas stream and an oxygen-containing gas stream for oxidizing the hydrogen chloride-containing gas stream into a reactor, reacting hydrogen chloride with oxygen under light irradiation conditions to produce a mixture comprising at least chlorine and water, the reactor being partitioned into a light irradiation zone and a non-light irradiation zone, the light irradiation zone being capable of being irradiated by light and the non-light irradiation zone being incapable of being irradiated by light, gas being communicable between the light irradiation zone and the non-light irradiation zone, the light having a wavelength of any one of or in the range of 150nm to 278 nm.

The inventors have further studied and found that when the energy of light irradiation causes only the activation of HCl without causing the activation of oxygen, the photocatalytic oxidation reaction of hydrogen chloride can not only occur, but also the reaction speed is faster and the yield is higher than when both hydrogen chloride and oxygen are activated. Accordingly, in one embodiment of the present application, the wavelength of the light is any value or range from 240nm to 278 nm.

Further, the water produced by the reaction and chlorine gas are liquefied while hydrogen chloride and oxygen gas are kept in a gaseous state, and liquid chlorine and liquid water are discharged from the reactor. The skilled person will understand how to select a suitable pressure and temperature to liquefy chlorine and water, while the hydrogen chloride and oxygen remain in a gaseous state, and separate the liquid chlorine from the liquid water to obtain chlorine.

In a preferred embodiment of the present application, the water produced by the reaction is liquefied, while the chlorine, hydrogen chloride and oxygen remain in gaseous form, and the liquid water is discharged from the reactor. The skilled person will understand how to select a suitable pressure and temperature to liquefy the water, while the chlorine, hydrogen chloride and oxygen are still in a gaseous state, and separate the chlorine, hydrogen chloride and oxygen to obtain chlorine, which can be recycled in the reactor.

In a particularly preferred embodiment of the present application, a series process flow of n-stage reactors is adopted, each reactor is divided into a light irradiation zone and a no light zone, water in the 1 st to (n-1) th stage reactors is liquefied and discharged from the reactor, chlorine, hydrogen chloride and oxygen are still kept in a gas state, the chlorine in the n-stage reactor is liquefied from the previous stage reactor and enters the next stage reactor, and the hydrogen chloride and the oxygen are still kept in a gas state, wherein n is more than or equal to 2, preferably, n is 3-5.

The hydrogen chloride and the oxygen can enter the reactor again after being discharged from the reactor for recycling, and the implementation mode is more favorable for reducing energy consumption.

The inventors have found that, after the reactor is partitioned into a light irradiation region and a light non-irradiation region, the gas in the light non-irradiation region is not irradiated with light and thus is not photolyzed, so that the photocatalytic back reaction of the product can be reduced.

Preferably, the temperature of the feed gas of hydrogen chloride and oxygen is any value or range of 0-50 ℃. In some preferred aspects of the present invention, the feed gas temperature of hydrogen chloride and oxygen is 0 to 10 ℃, 0 to 20 ℃, 0 to 30 ℃, 0 to 40 ℃, 10 to 20 ℃, 10 to 30 ℃, 10 to 40 ℃, 10 to 50 ℃, 20 to 30 ℃, 20 to 40 ℃, 20 to 50 ℃, 30 to 40 ℃, 30 to 50 ℃ or 40 to 50 ℃.

Preferably, the temperature of the light irradiation region is in any value or range between 0 ℃ and 200 ℃. In some preferred aspects of the present invention, the temperature of the light irradiation region is in the range of 0 to 50 ℃, 0 to 100 ℃, 0 to 150 ℃, 50 to 100 ℃, 50 to 150 ℃, 50 to 200 ℃, 100 to 150 ℃, 100 to 200 ℃ or 150 to 200 ℃, and particularly preferably, the temperature of the light irradiation region is in the range of 20 ℃ to 140 ℃.

Preferably, the hydrogen chloride and the oxygen directly enter the light irradiation region.

The process of the present invention may be carried out continuously or batchwise, preferably continuously.

In all embodiments of the present invention it is preferred that the feed volume ratio of said hydrogen chloride gas containing stream (calculated as pure hydrogen chloride) to said oxygen containing stream for oxidizing the hydrogen chloride gas stream (calculated as pure oxygen) is 4: 1.

The hydrogen chloride-containing gas stream described herein can be a hydrogen chloride-containing gas stream in the form of a by-product from the related industry production, such as the production of isocyanates, the production of acid chlorides, the chlorination of aromatics, and the like. The hydrogen chloride gas containing stream in the form of a by-product may be a hydrogen chloride gas containing stream in the form of a treated by-product or a hydrogen chloride gas containing stream in the form of a by-product directly from the relevant industry without any treatment. The hydrogen chloride-containing gas stream in the form of a byproduct can contain a small amount or no other impurity gases which have no influence on the photocatalytic oxidation of hydrogen chloride and are also derived from related industries according to different sources. The amount of other impurity gases is determined by the nature of the associated industry. Those skilled in the art will appreciate that the so-called off-gas hydrogen chloride produced in the relevant industry may be a suitable feedstock for the present application.

The oxygen-containing gas stream described herein may be pure oxygen or another oxygen-containing gas (e.g., air).

When the water in the reactor is liquefied, a part of hydrogen chloride, chlorine and oxygen enter the condensed water in a small amount and can be separated by a simple distillation method, and the separated gas can be recycled to enter the reactor to continuously participate in the reaction. Similarly, when the water and chlorine gas in the reactor are liquefied, a part of hydrogen chloride and oxygen gas also enter the condensate in small quantity, and can be separated by a simple distillation method, and the separated gas can be recycled into the reactor to continuously participate in the reaction.

The present application relates, in another aspect, to an apparatus for producing chlorine by photocatalytic oxidation of hydrogen chloride, comprising a reactor provided with a gas feed port, a liquid discharge port, and a gas discharge port, the reactor being internally provided with a light source and being partitioned into a light irradiation region and a light-less region by a structure that is gas-permeable and light-impermeable, the light irradiation region being capable of being irradiated with light and the light-less region being incapable of being irradiated with light, the gas between the light irradiation region and the light-less region being capable of flowing.

In a preferred embodiment of the present application, the air-permeable, light-impermeable structure is a louver structure.

In an embodiment of the present application, the structure that is air permeable and light-tight is a double-layer plate structure, and staggered holes are formed in the inner layer plate and the outer layer plate of the double-layer plate, so that the reactor is air permeable and light-tight, and is separated.

In one embodiment of the present application, the air-permeable and light-impermeable structure refers to a structure made of an air-permeable and light-impermeable material, such as an expanded polytetrafluoroethylene film.

Preferably, the liquid discharge port is arranged at the bottom of the reactor, a concave liquid collecting area is arranged at the bottom of the reactor, and the concave liquid collecting area is directly connected with the discharge port. The liquid formed in the reactor is firstly collected in the sunken liquid collecting area and then discharged from the discharge hole.

In a particularly preferred embodiment of the present application, the reactor of the hydrogen chloride photocatalytic oxidation device is a tubular structure and comprises a bent part, one side of the bent part is provided with a light source to form a light irradiation area, and the other side is provided with no light source to form a no light area; preferably, the bending angle of the bent portion is 180 degrees. By utilizing the particularity of the tubular structure, the reactor is divided into a light irradiation area and a no light area without additionally arranging a structure which is permeable to air and not permeable to light.

In a preferred embodiment of the present application, the hydrogen chloride photocatalytic oxidation apparatus, the light irradiation region and the no light region are composed of two separate members connected by a pipe, one of the members is provided with a light source to constitute the light irradiation region, and the other member is provided without a light source to constitute the no light region. The gas between the light irradiation region and the no light region is circulated through the duct. For example, the component provided with the light source is a reactor, and the component without the light source is a cooler, wherein the cooler can be provided as required and is a water cooler or a chiller, or a chiller is further connected behind the water cooler to liquefy the chlorine.

Further, the outer surface of the reactor is provided with a jacket layer. The jacket layer is provided with a heat transfer medium inlet and a heat transfer medium outlet, as will be appreciated by those skilled in the art. It is also possible to provide jackets or other heat exchange devices in the light irradiation region and the non-light-irradiated region, respectively, so as to better control the temperatures of the light irradiation region and the non-light-irradiated region. When the light irradiation area and the non-light irradiation area need to control different temperatures, the structure which is permeable to air and not permeable to light is preferably made of heat insulation materials or is additionally provided with a heat insulation layer. Preferably, the light source is provided in an elongated shape.

Preferably, the gas feed port is provided in the light irradiation region.

The liquid discharge port pipeline is connected with the storage tank.

Preferably, a preheater is arranged on the pipeline where the gas feed inlet is located.

Compared with the prior art, the method has the following beneficial effects:

(1) by dividing the reactor into a special light irradiation area and a no light area, the product gas can be prevented from being continuously photolyzed under the light irradiation condition;

(2) through certain pressure and temperature conditions, partial product gas is directly liquefied and then discharged out of the reactor, so that the reaction balance can be promoted to be carried out towards the direction of generating the product;

(3) the method has mild reaction conditions, uses the photocatalyst, has the advantages of cleanness, environmental protection and the like, and is suitable for industrialization;

(4) the method has the advantages of low investment, easy production capacity and no special requirements on the size and the height-diameter ratio of the reactor.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a hydrogen chloride photocatalytic oxidation apparatus according to example 1 of the present application;

FIG. 2 is a schematic view of the air permeable, light impermeable structural component of FIG. 1;

FIG. 3 is a schematic view showing a hydrogen chloride photocatalytic oxidation apparatus according to example 3 of the present application;

FIG. 4 shows a hydrogen chloride photocatalytic oxidation apparatus according to example 4 of the present application;

FIG. 5 shows a hydrogen chloride photocatalytic oxidation apparatus according to example 6 of the present application;

FIG. 6 shows a hydrogen chloride photocatalytic oxidation apparatus according to example 7 of the present application;

reference signs mean: 1-reactor, 2-light irradiation zone, 3-no light zone, 4-gas permeable and light impermeable structure, 5-gas inlet, 6-liquid outlet, 7-storage tank, 8-jacket, 9-light source, 10-gas outlet, 11-1 st stage reactor, 12-2 nd stage reactor, 13-3 rd stage reactor, 14-4 th stage reactor, 15-water cooler of 4 th stage reactor, 16-deep cooler of 4 th stage reactor, 17-pressure pump, 18-water storage tank, 141-light irradiation zone of 4 th stage reactor.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.