CN101347723A - A catalyst for low-temperature catalytic combustion elimination of chlorinated aromatic hydrocarbons - Google Patents

Abstract

The invention discloses a catalyst for low-temperature catalytic combustion and elimination of volatile chlorinated aromatic hydrocarbons. The catalyst is mainly composed of alumina carrier and its supported rare earth oxide and transition metal oxide, wherein the transition metal element is Cu , Fe, V, Mn, Mo, Co, W, and the rare earth oxide is one or more of lanthanum oxide, cerium oxide, neodymium oxide, and gadolinium oxide. The invention has high catalytic activity, no by-product formation, no secondary pollution, strong chlorine poisoning resistance and long catalyst life, and is especially suitable for low-temperature catalytic combustion to eliminate halogen-containing organic compounds, especially volatile chlorine-containing aromatic hydrocarbon pollution things.

Description

A catalyst for low-temperature catalytic combustion elimination of chlorinated aromatic hydrocarbons

technical field

The invention belongs to the technical field of catalytic combustion environmental protection, and in particular relates to a transition metal-rare earth composite oxide catalyst and a preparation method thereof for the low-temperature catalytic combustion elimination of volatile chlorinated aromatic hydrocarbons, and provides a method for A method for completely catalytic combustion to eliminate volatile chlorinated aromatic hydrocarbon pollutants in the environment.

Background technique

Environmental pollution, especially the increasing air pollution, is one of the most concerned issues in the 21st century. In addition to SOx, NOx, ozone, and hydrocarbons, dioxins (polychlorinated dibenzo-p-dioxins, PCDDs) have persistent pollution to the environment. The harm of dioxin-like compounds is not only to human health, but also to cause lasting and cumulative effects on biological systems, and to destroy atmospheric ozone. In the International Treaty of the United Nations Environment Program, dioxin-like compounds are listed as the first persistent and most toxic organic pollutants. One of the sources of dioxin-like compounds is produced by the polychlorination of polychlorinated aromatic hydrocarbons, and more is produced by the combination of solid carbon, oxygen, and chlorine sources. During the incineration of municipal solid waste (MSW), in the presence of a chlorine source and a catalyst, the combustion process of organic compounds involves the generation of dioxins. A part of dioxin is discharged into the atmosphere in the form of waste gas, and a part is discharged into the atmosphere in the form of fine solid particles attached to flue gas. The key component of producing dioxin-chlorine source mainly comes from the solid waste of chlorine-containing compounds, the bleaching process of wood pulp by chlorine-based oxidants, the heat treatment of chlorine-containing compounds and the industrial waste of metal recovery process, large-scale chlor-alkali Industrial waste and municipal solid waste produced in the process of preparing vinyl chloride by oxychlorine method in industry. Since the above-mentioned process of producing and using chlorine-containing compounds is related to the national economy and people's livelihood of our country at this stage, the discharge of solid wastes that produce a large amount of dioxin precursors is inevitable.

In recent years, the comprehensive management of volatile organic compounds (VOCs) has received more and more attention. Methods such as thermal combustion, catalytic combustion, and adsorption are common methods for eliminating these pollutants. However, thermal combustion needs to be carried out at a higher temperature (1000°C), and the energy consumption is large; and this method may also lead to more toxic Dioxins (Dioxins) pollutants in the treatment of chlorinated hydrocarbons, such as polychlorinated dioxins. Benzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF). As one of the commonly used methods for organic pollutants, the adsorption method is not ideal for the treatment of low-concentration pollutants, and its adsorption efficiency is extremely low. For the elimination of volatile chlorinated aromatic hydrocarbons, a variety of novel methods have recently been proposed, such as biological treatment, photocatalytic degradation, hydrodechlorination, etc. However, these methods either have technical defects or high processing costs. Most of them are in the state of laboratory research, and it is difficult to realize industrialization and industrialization.

Catalytic combustion to eliminate pollution of organic compounds is an energy-saving, economical and effective treatment method. Compared with thermal combustion, it has the advantages of low combustion temperature, short residence time, small reactor required, and less secondary pollution. Therefore, catalytic combustion has been widely used in the elimination of VOCs.

The catalytic combustion of chlorinated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, and dioxin is mainly used in the waste gas treatment of waste incinerators. The research work and technology development in this direction are concentrated in Japan. Representative patents include Jpn. Kokai Tokkyo Kobo JP2001286729 A2, Jpn. Kokai Tokkyo Koho JP 2001286730 A2, Jpn. Combustion with fuel gas and air. The main catalyst active components are transition metals and noble metals, and the carriers are SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ . Although noble metal catalysts have high activity, they are prone to chlorine poisoning; non-precious metal catalysts have strong anti-poisoning ability, but low selectivity, and often produce polychlorobenzene.

The authorized patents for the catalytic combustion of partially chlorinated aromatic hydrocarbons include:

[1] Nawama, Junichi; Moriya, Yoshifumi; Suzuki, Tadashi; Kuchino, Kunikazu, Jpn. Kokai Tokkyo Kobo JP 2002219364A2

[2] Kiyono, Kenichi; Uchida, Masaaki; Adachi, Kentaro; Nishii, Kazuhiro, Jpn.KokaiTokkyo Koho JP 2001286729A2

[3] Kiyono, Kenichi; Uchida, Masaaki; Adachi, Kentaro; Nishii, Kazuhiro, Jpn.KokaiTokkyo Kobo JP 2001286730A2

[4] Kajikawa, Osamu; Wang, Hsiang Sheng; Kawase, Noboru; Maeda, Takeshi, Jpn. KokaiTokkyo Koho JP 2001009284A2.

[5] Kiyono, Kenichi; Uchida, Masaaki; Adachi, Kentaro; Nishii, Kazuhiro, Jpn.KokaiTokkyo Koho JP 2001286734A2

[6]Moriya, Yoshifumi; Nawama, Junichi; Tokumitsu, Shuzo, Jpn.Kokai Tokkyo Koho JP2001327869A2

These patent works mainly use transition metals as active components to catalytically burn and purify dioxins in waste incinerators.

The catalysts used for the catalytic combustion elimination of the above-mentioned chlorinated volatile hydrocarbons all have more or less shortcomings, such as low catalytic combustion activity, polychlorinated hydrocarbons are produced during the catalytic combustion process, which is easy to cause secondary pollution, and the catalyst activity group points are easily lost, and the catalyst life is short.

Contents of the invention

The purpose of the present invention is to disclose a transition metal-rare earth composite oxide catalyst for low-temperature catalytic combustion elimination of volatile chlorinated aromatic hydrocarbons and a preparation method thereof. This type of catalyst has high catalytic activity, no by-product formation, no secondary pollution, strong resistance to chlorine poisoning, and long catalyst life. It is especially suitable for catalytic combustion to eliminate halogen-containing organic compounds, especially volatile chlorine-containing aromatic hydrocarbon pollutants. .

The invention provides a catalyst for low-temperature catalytic combustion elimination of volatile chlorinated aromatic hydrocarbons. The catalyst is mainly composed of alumina carrier and its loaded rare earth oxide and transition metal oxide, wherein the transition metal element oxide It is composed of one or more of copper oxide, iron oxide, vanadium oxide, manganese oxide, molybdenum oxide, cobalt oxide, and tungsten oxide. The preferred transition metal oxides are copper oxide, iron oxide, and manganese oxide; the rare earth oxide is lanthanum oxide , cerium oxide, neodymium oxide, gadolinium oxide or one or more of them, and the preferred rare earth oxides are lanthanum oxide and cerium oxide. The transition metal content is 10-18wt% (oxide content), preferably 14-18wt%; the rare earth oxide is 1-10%, preferably 2-4wt.%; the alumina content is 80%.

The transition metal oxide and rare earth composite oxide catalyst supported by alumina support is prepared by sol-gel method, the precursor of transition metal oxide is selected from nitrate, oxalate, acetate, carbonate; the precursor of rare earth oxide The body is selected from nitrates of rare earths, and the precursor of alumina is selected from aluminum nitrate.

The invention provides a method for catalytic combustion and elimination of volatile chloroaromatic hydrocarbon compounds in the environment. The present invention provides following technical routes:

In the presence of a catalyst, the air used as an oxidant is brought into the reactor, so that the volatile chlorine-containing aromatic hydrocarbons are completely burned and converted into carbon dioxide, hydrogen chloride and chlorine under the action of the catalyst. The tail gas after catalytic combustion treatment can be absorbed by dilute alkali solution (acid gas such as hydrogen chloride/chlorine gas) and then vented.

The reaction pressure is 0.1-1Mpa, preferably 0.1-0.5Mpa, especially 0.1Mpa, close to normal pressure, and the temperature is 150-450°C, preferably 250-400°C, especially 400°C.

The amount of catalyst used must be enough to convert volatile chlorine-containing aromatic hydrocarbons into carbon dioxide and hydrogen chloride in the presence of air. Generally, the concentration of volatile chlorine-containing aromatic hydrocarbons in the exhaust gas is 0.05-5vol%. The amount of waste gas treated by a gram of catalyst is 10-30L per hour.

The catalyst provided by the invention has the characteristics of simple preparation process, low price, high catalytic activity, strong chlorine poisoning resistance, and long life; the technical route is convenient and practical, and can be widely used in papermaking, pharmaceuticals, tanning, washing and chemical industry waste gas Catalytic combustion elimination of volatile chlorinated aromatic hydrocarbon pollutants.

Detailed ways

Example 1

Commercially available 4.1g cerium nitrate (Ce(NO ₃ ) ₃ 6H ₂ O), 4.3g lanthanum nitrate (La(NO ₃ ) ₃ 6H ₂ O), 680.4g aluminum nitrate (Al(NO ₃ ) ₃ . 6H ₂ O) was put into 40.9g of manganese nitrate (Mn(NO ₃ ) ₂ ) 50wt% aqueous solution, and deionized water was added to make the volume of the solution reach 350ml, dissolved at room temperature, and then 100g of citric acid was added and dissolved. Place the solution in a constant temperature water bath at 80°C and stir for 6-7 hours; then put it in a drying oven at 110°C for 12 hours, move it to a roasting furnace, and program the temperature in the air atmosphere, 4.2°C per minute, rising to 550°C, After 5 hours of heat preservation, a 17.6% Mn ₂ O ₃ -1.2% CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst can be obtained. Tablet crushing 20-40 mesh particles, ready to use.

The 16% Fe ₂ O ₃ -2% CeO ₂ -2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst prepared by the method of Example 1 is Example 2.

The 16% Mn ₂ O ₃ -2% CeO ₂ -2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst prepared by the method of Example 1 is Example 3.

The 17.6% Mn ₂ O ₃ -1.2% CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst prepared in Example 1 was calcined at 650° C. for 5 hours to obtain Example 4.

The 17.6% Mn ₂ O ₃ -1.2% CeO ₂ -].2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst prepared in Example 1 was calcined at 750° C. for 5 hours to obtain Example 5.

Example 6

Put commercially available 8.2g cerium nitrate (Ce(NO ₃ ) ₃ 6H ₂ O), 680.4g aluminum nitrate (Al(NO ₃ ) ₃ 6H ₂ O) into 40.9g manganese nitrate (Mn(NO ₃ ) ₂ ) 50wt% aqueous solution, add deionized water to make the volume of the solution reach 350ml, dissolve at room temperature, add 100g citric acid, and make it dissolve. Place the solution in a constant temperature water bath at 80°C and stir for 6-7 hours; then put it in a drying oven at 110°C for 12 hours, move it to a roasting furnace, and program the temperature in the air atmosphere, 4.2°C per minute, rising to 550°C, The 17.6% Mn ₂ O ₃ -2.4% CeO ₂ -80% Al ₂ O ₃ catalyst can be obtained by keeping the temperature for 5 hours.

The 16%NiO-4% _CeO2-80 % _Al2O3 catalyst prepared by the _method of Embodiment 6 is Embodiment 7.

The 16% Co ₂ O ₃ -4% CeO ₂ -80% Al ₂ O ₃ catalyst prepared by the method of Example 6 is Example 8.

Example 9

Catalyst activity evaluation was carried out in a fixed bed reactor. The chlorobenzene combustion activity tests of all catalysts were carried out in a U-shaped quartz micro-reactor (inner diameter 6 mm), the amount of catalyst was 200 mg, and the temperature was automatically controlled by a K-type thermocouple. Chlorobenzene is injected into the vaporization chamber by the 100 series KDS120 micro-injection pump of Stoelting Company in the United States, and then mixed with air and then enters the reactor for combustion. The total flow is controlled by a mass flow meter, the concentration of chlorobenzene is controlled at 0.1vol%, the amount of exhaust gas treated per gram of catalyst per hour is 15L, and the linear velocity of gas passing through the reactor is 120m/h. Reaction pressure is 0.1Mpa, and the relation of the conversion ratio of chlorobenzene and reaction temperature is shown in Table 1, and T _10% , T _50% , T _98% in Table 1 are respectively when conversion ratio reaches 10%, 50%, 98%. the desired reaction temperature. The main reaction products are carbon dioxide, hydrogen chloride and trace amounts of chlorine.

Table 1 Catalytic combustion performance of chlorobenzene on different catalysts

Catalyst T _10% (°C) T _50% (°C) T _98% (°C) Example 1 103 185 260 Example 2 185 275 456 Example 3 112 189 263 Example 4 128 211 282 Example 5 253 311 415 Example 6 129 272 329 Example 7 136 271 532 Example 8 195 276 523

Example 10

The concentration of polychlorobenzene is controlled at 0.1-0.3%, the rest is air, and the amount of waste gas treated per gram of catalyst per hour is 10L. The catalytic combustion performance of the catalyst of Example 1 to polychlorobenzene is investigated, and the results are shown in Table 2.

The catalytic combustion activity of polychlorinated benzene on the catalyst of table 2 embodiment 1

  Chlorinated aromatics T _10% (°C) T _50% (°C) T _98% (°C)  Dichlorobenzene 122 236 292 Trichlorobenzene 128 250 340   Tetrachlorobenzene 141 275 360

The results show that the 17.6%Mn ₂ O ₃ -2.4%CeO ₂ -80%Al ₂ O ₃ catalyst has good catalytic combustion performance for different types of polychlorobenzene.

Example 11

Change the concentration of chlorobenzene, control the moisture concentration in the air at 0.45-1vol.%, the amount of waste gas treated per gram of catalyst per hour is 20L, the reaction pressure is 0.3-0.5Mpa, and the temperature is 17.6% Mn ₂ O ₃ -1.2% The catalytic combustion performance of different concentrations of chlorobenzene was investigated on the CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst, and the results are shown in Table 3.

Table 3 Catalytic combustion performance of different concentrations of chlorobenzene on 17.6%Mn ₂ O ₃ -1.2%CeO ₂ -1.2%La ₂ O ₃ -80%Al ₂ O ₃ catalysts

The results show that the 17.6% Mn ₂ O ₃ -1.2% CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst has good catalytic combustion performance for low concentration of chlorobenzene. It can be seen that the catalyst of the present invention can be widely used in the catalytic combustion elimination of volatile chlorine-containing aromatic hydrocarbons with different concentrations (including low concentration and high concentration).

Example 12

Change the amount of exhaust gas per gram of catalyst per hour, the reaction pressure is 0.1Mpa, the concentration of chlorobenzene is 0.1vol%, and air is used as the oxidizing gas. On the catalyst of Example 1, different space velocity p-chlorobenzene The effect of catalytic combustion performance, the results are shown in Table 4.

Table 4 Effect of space velocity on catalytic combustion performance of 17.6%Mn ₂ O ₃ -1.2% CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalyst

Example 13

In the reaction device of Example 9, the amount of exhaust gas treated per gram of catalyst per hour is 20 L, and chlorobenzene is used as a volatile chlorine-containing aromatic hydrocarbon compound, and the reaction temperature is 400 ° C to examine 17.6% Mn ₂ O ₃ -1.2% Activity stability of CeO ₂ -1.2% La ₂ O ₃ -80% Al ₂ O ₃ catalysts in reaction atmosphere. The results showed that after 200 hours of reaction, the conversion rate of chlorobenzene was greater than 98%, and no polychlorobenzene was detected in the reaction product. This point is especially important for the industrial application of catalytic elimination of chlorine- _containing volatile aromatic hydrocarbons, indicating that _the 17.6 _{% Mn2O3-1.2} % _CeO2-1.2 % _La2O3-80 % _Al2O3 catalyst is industrially easy The catalytic treatment of volatile chlorine-containing aromatic hydrocarbons has great application prospects.

Claims (4)

1. one kind is used for the catalyst that the easy-to-volatile chloroarene low-temperature catalytic burning is eliminated, this catalyst mainly is made of the rare earth oxide and the transition metal oxide of alumina support and load thereof, wherein transition metal oxide is one or several formation of cupric oxide, iron oxide, vanadium oxide, manganese oxide, molybdenum oxide, cobalt oxide, tungsten oxide, and preferred transition metal oxide is cupric oxide, iron oxide, manganese oxide; Rare earth oxide is one or several formation of lanthana, cerium oxide, neodymia, oxidation Gadolinium, and preferred rare earth oxide is lanthana, cerium oxide.The content of transition metal oxide is 10～18wt%, is preferably 14～18wt%; Rare earth oxide is 1～10%, is preferably 2～4wt.%; Alumina content is 80%.

2. the described Preparation of catalysts method of claim 1 is characterized in that: the transition metal oxide of alumina support load and rare earth oxide catalyst adopt the citric acid collosol and gel to make, and the rare earth oxide presoma is selected from the nitrate of rare earth; The presoma of transition metal oxide is selected from nitrate, oxalates, acetate, carbonate; The presoma of aluminium oxide is selected from aluminum nitrate.

3. the described Preparation of catalysts method of claim 2, it is characterized in that: rare earth nitrades, transition metal salt and the aluminum nitrate of metering are mixed, are dissolved in a certain amount of deionized water, add citric acid then, this solution places 80 ℃ constant temperature water bath to stir 6～7h; Put into 110 ℃ the dry 12h of drying box then, move in the roaster, temperature programming in air atmosphere, 4.2 ℃ of per minutes are raised to 550 ℃, are incubated 5h, promptly get the transition metal oxide and the rare earth oxide catalyst of the described alumina load of claim 2.

4. the low-temperature catalytic burning that is widely used in industrial waste gas, refuse, waste water easy-to-volatile chloroarene according to the described catalyst that is used for the elimination of easy-to-volatile chloroarene low-temperature catalytic burning of claim 1 is eliminated, especially the chloride arene pollutant of the effumability in the industrial waste gas.