WO2019076090A1

WO2019076090A1 - Supported vocs catalytic combustion catalyst and preparation method therefor

Info

Publication number: WO2019076090A1
Application number: PCT/CN2018/094516
Authority: WO
Inventors: 李俊华; 李兵; 彭悦; 陈建军; 刘帅
Original assignee: 清华大学
Priority date: 2017-10-17
Filing date: 2018-07-04
Publication date: 2019-04-25
Also published as: CN107570163A; CN107570163B

Abstract

A supported VOCs catalytic combustion catalyst and a preparation method therefor. The catalyst uses a cordierite ceramic as a carrier, a ternary solid solution Cex-Zry-Ti(1-x-y)-O2 with a three-dimensional porous cellular skeleton structure as a coating, and a composite oxide consisting of Co and Ce as a catalytic active component. The preparation method comprises: first, coating a pretreated carrier with a ternary solid solution with the three-dimensional porous cellular skeleton structure by using a complexing dipping method; then, preparing a cobalt-cerium composite oxide by using an in-situ spontaneous combustion synthesis method, dipping the carrier into a precursor solution, forming a stable cage-shaped structure by combining lone pair electrons of an organic template agent and vacant orbits of metal ions, and synthesizing a precursor of the active components on the surface in situ.

Description

Supported VOCs catalytic combustion catalyst and preparation method thereof

Technical field

The invention belongs to the technical field of air pollution control technology and environmental protection catalytic material, and particularly relates to a catalytic VOCs catalytic combustion catalyst and a preparation method thereof.

Background technique

Volatile organic waste gases (VOCs) are one of the main causes of haze, atmospheric photochemical smog, greenhouse effect and ozone layer damage. They are mainly from petrochemical, fine chemical, textile printing, spraying, packaging and printing, pharmaceutical and pesticide manufacturing. Exhaust gases emitted in the production process of electronics and other industries bring great harm to the ecological environment and human health. According to incomplete statistics, the annual emissions of industrial VOCs in China are about 12 million tons in 2010. It is estimated that by 2020, the annual emissions of industrial VOCs in China will reach 25 million tons, which will exceed the combined value of developed countries such as Europe and the United States. In the face of the increasingly serious environmental pollution situation, the government's emission restrictions on VOCs are becoming more and more strict. In September 2013, the State Council issued the “Air Pollution Prevention and Control Action Plan” (“Atmosphere Ten”), pointing out that it is necessary to promote the control of volatile organic compounds pollution, and implement volatile organic compounds in petrochemical, organic chemical, surface coating, packaging and printing industries. Remediation. In June 2015, the Ministry of Finance, the National Development and Reform Commission, and the Ministry of Environmental Protection jointly issued the “Vacuum Measures for Volatile Organic Pollutant Charges”, which requires the polluting fees of VOCs to be collected for the petrochemical and packaging printing industries. The new Air Pollution Prevention and Control Law, which was implemented in January 2016, is the first to include VOCs in the scope of supervision, which has a legal basis for VOCs governance. In summary, VOCs will become the focus of the government's attention in the air pollution control industry during the 13th Five-Year Plan period.

Among the many technologies for processing VOCs at home and abroad, catalytic combustion technology has become the mainstream technology and development direction for processing VOCs. It uses the catalyst to completely burn the organic exhaust gas at a lower light-off temperature and emits a large amount of heat to achieve self-heating of the reaction. Compared with other treatment technologies, catalytic combustion has the advantages of wide application range, low light-off temperature, low energy consumption, high efficiency, no secondary pollution, and high-efficiency catalyst is the core of the catalytic combustion technology.

In the VOCs catalyst system, noble metal catalysts have been widely used in VOCs treatment processes due to their high catalytic activity and low light-off temperature. However, due to the shortage of precious metal resources and high prices, the research hotspots in recent years mainly focus on the oxides of transition metal and rare earth metal complexes. The composite oxides show good catalytic activity, and the process is optimized and rationally doped. The catalytic properties of the composite oxide catalyst are superior to those of other single metal oxide catalysts, as well as loading onto a suitable support. However, the research on it is focused on powdered catalysts, but the research on supported catalysts, especially the ones that can be finally applied to the industry, is only in the experimental stage, and the preparation process is complicated. The shortcomings of expensive materials can not truly achieve industrialized mass production. The traditional load-type preparation technology still faces many difficulties to overcome in terms of particle size, structure control, and high dispersion. Therefore, it is necessary to continuously explore a new type of supported catalyst preparation technology, and to prepare an industrialized size catalyst with suitable particle size, structure controllability and high dispersion with simple process technology and low price, so that it can be practically applied to working conditions. The key problems to be solved in the research of composite oxides. A four-component catalyst as described in the invention of the patent CN1462648B, which has mild operating conditions and low cost, greatly reduces the reaction temperature and improves the activity compared with the prior art non-precious metal catalyst, but the preparation process is complicated and is not suitable for expansion. produce. Patent CN101015806A discloses a wire mesh type catalytic combustion catalyst and a preparation and application thereof, which have high mechanical energy and high activity, but the active components are generally unevenly distributed and easily fall off. Patent CN101439290A discloses a honeycomb ceramic type perovskite catalytic combustion catalyst and a preparation and application thereof. The catalyst coating slurry composition is complex, the coating surface is lower than the surface, and multiple coating is required, which easily causes the coating to fall off.

Summary of the invention

In order to overcome the above disadvantages of the prior art, an object of the present invention is to provide a supported VOCs catalytic combustion catalyst and a preparation method thereof, wherein the active component of the catalyst is uniformly dispersed, between the carrier and the coating, and between the active component and the coating layer. The high-strength combination of structure has the characteristics of low light-off temperature, high conversion efficiency, high temperature resistance and low price, and can be widely used for VOCs purification treatment.

In order to achieve the above object, the technical solution adopted by the present invention is:

A supported VOCs catalytic combustion catalyst, wherein the catalyst comprises a cordierite ceramic as a carrier, and the coating is coated with a coating and an active component from the inside to the outside in a carrier, the coating being a ternary solid solution having a three-dimensional porous honeycomb skeleton structure, The molecular formula is Ce _x -Zr _y -Ti _1-xy -O ₂ , and the active component is a cobalt ruthenium composite oxide. The mass percentage of the coating and the active component loading is respectively based on the mass of the carrier. 5% to 10% and 5% to 20%.

In Ce _x -Zr _y -Ti _1-xy -O ₂ , 0 < x < 1, 0 < y < 1, and x + y < 1.

In the cobalt-cerium composite oxide, the molar ratio is Ce/Co = 0.01 to 1.

The invention also provides a preparation method of the supported VOCs catalytic combustion catalyst, comprising the following steps:

(1) Carrier pretreatment

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _x -Zr _y -Ti _1-xy -O _{2 of} three-dimensional porous honeycomb skeleton structure is prepared by complex impregnation method, and a mixed solution of cerium salt, zirconium salt and titanium is prepared by adding a complexing agent, and a complexing agent is added. The kettle is cooked in a water bath to form a sol, and then the cordierite ceramic carrier is placed in a sol, taken out to dry, dried, and calcined to obtain a Ce _x -Zr _y -Ti _1-xy -O ₂ coating modified ruthenium. Bluestone ceramic carrier;

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide is prepared by in-situ auto-ignition synthesis method, and a mixed solution of a certain concentration of cobalt salt, strontium salt and organic templating agent is prepared, and after being completely dissolved by stirring, Ce _x -Zr _y -Ti _{1-xy is prepared.} The -O ₂ coating modified cordierite carrier is immersed in the solution, taken out after being saturated with the immersion, naturally dried and aged, heated and dried by a programmed temperature, and promotes the combination of the lone pair of electrons and the metal ions in the organic template. Forming a stable cage structure, realizing the in-situ synthesis of the active component precursor on the surface, high-temperature baking, preparing uniform dispersion of the active component, high-strength combination of the carrier and the coating, and the structure between the active component and the coating catalyst.

In the step (1), the carrier pretreatment method is as follows:

The cordierite honeycomb ceramic carrier is taken, immersed in a 5-20 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 1 h to 4 h, washed with water under ultrasonic assistance until the solution is neutral, dried, calcined, and set aside.

During the pretreatment of the carrier, the drying temperature is 80 to 100 ° C, and the baking condition is 400 to 550 ° C, 0.5 to 1 h;

In the preparation process of the catalyst coating, the drying temperature is 80-120 ° C, and the baking condition is 400-650 ° C, 2-6 h;

During the preparation of the active component of the catalyst, the high temperature calcination condition is 450 to 750 ° C for 2 to 6 hours.

During the preparation of the active component of the catalyst, the conditions of temperature-programmed heating and drying are: 5 ° C / min to 200 - 250 ° C, and the temperature is maintained for 0.5 ~ 2 h.

In the steps (2) and (3), the cerium salt is one or more of cerium nitrate, cerium chloride and cerium acetate. In the step (2), the zirconium salt is zirconium nitrate and zirconium oxychloride. And one or more of zirconium acetate, the titanium source is titanium titanyl oxalate and/or titanium sulfate, and the complexing agent is one or more of citric acid, glycine and acrylamide, and the step (3) The cobalt salt is one or more of cobalt nitrate, cobalt oxychloride and cobalt acetate, and the organic templating agent is a polyhydroxy organic acid.

The polyhydroxy organic acid is one or more of malic acid, citric acid, and oxalic acid.

Compared with the prior art, the preparation process of the invention is simple, the preparation raw materials are easy to obtain, the cost is low, the active component is evenly distributed and has strong binding force with the carrier, is not easy to fall off and crack, and can be maintained under high airspeed airflow and thermal shock. It has high activity and wide application range, and can be widely used in industrial VOCs purification.

DRAWINGS

1 is an SEM spectrum of a Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst in Example 1.

2 is a performance test chart of a Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst in Example 1.

Detailed ways

The following is a specific embodiment of the present invention. The preparation method of a supported VOCs catalytic combustion catalyst according to the present invention is further described, but the scope of protection of the present invention is not limited to these examples. Any changes or equivalents that do not depart from the inventive concept are included in the scope of the present invention.

Example 1

A method for preparing a catalytic VOCs catalytic combustion catalyst, the steps are as follows:

(1) Carrier pretreatment

The cordierite honeycomb ceramic carrier was taken, immersed in a 5 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 4 hours, and washed with water under ultrasonic assistance until the solution was neutral, dried at 100 ° C, calcined at 550 ° C for 1 h, and set aside.

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _0.8 -Zr _0.1 -Ti _0.1 O _{2 of the} three-dimensional porous honeycomb skeleton structure was prepared by complex impregnation method. Prepare 0.56moL/L lanthanum nitrate, 0.07moL/L zirconium nitrate, 0.07moL/L titanium sulfate and 0.14moL/L citric acid mixed solution, cook in a water bath to make it sol, then place the cordierite carrier in the sol. In the middle, it was taken out to dry, dried at 100 ° C, and calcined at 650 ° C for 2 h to obtain a Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ coating modified cordierite support with a loading of 5%.

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide was prepared by in-situ autoignition synthesis method, and 2.1kL/L lanthanum nitrate, 0.7moL/L cobalt nitrate and 0.28moL/L oxalic acid mixed solution were prepared. After being completely dissolved by stirring, Ce _0.8 -Zr _{0.1 was prepared.} -Ti _0.1 O ₂ coating modified cordierite carrier is immersed in the solution, taken out after immersion saturation, naturally dried and aged, programmed to heat and dry 5 ° C / min to 250 ° C, heat preservation 0.5 h, 500 ° C high temperature roasting 6h, a Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst with a loading of 20% was prepared.

Referring to Fig. 1, it can be seen that the active component is uniformly distributed on the surface of the carrier, the particle size is uniform, and the structure between the carrier and the coating, the active component and the coating layer is achieved with high strength.

Referring to Fig. 2, it was found that the Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst was subjected to a stability test for 60 days. The catalysts were tested under different airspeed, type and concentration reaction conditions, and the catalytic performance was maintained. After 60 days of continuous testing, the catalytic combustion conversion rate was maintained above 95.0%, showing good catalytic stability. The trend of activity decline.

Example 2

(1) Carrier pretreatment

The cordierite honeycomb ceramic carrier was taken, immersed in a 20 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 1 h, washed with water under ultrasonic assistance until the solution was neutral, dried at 80 ° C, calcined at 550 ° C for 1 h, and set aside.

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _0.5 -Zr _0.4 -Ti _0.1 O _{2 of the} three-dimensional porous honeycomb skeleton structure was prepared by the complex impregnation method. Prepare 0.35moL/L lanthanum acetate, 0.28moL/L zirconium nitrate, 0.07moL/L titanium sulfate and 0.07moL/L glycine mixed solution, cook in a water bath to make it sol, then place the cordierite carrier in the sol. The mixture was dried, dried at 80 ° C, and calcined at 400 ° C for 6 h to obtain a Ce _0.5 -Zr _0.4 -Ti _0.1 O ₂ coating modified cordierite support having a loading of 5%.

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide was prepared by in-situ autoignition synthesis method, and 1.4kL/L lanthanum nitrate, 1.4moL/L cobalt acetate and 0.56moL/L citric acid mixed solution were prepared. After being completely dissolved by stirring, Ce _0.5 -Zr was prepared. _0.4- Ti _0.1 O ₂ coating modified cordierite carrier is immersed in the solution, taken out after saturation, naturally dried and aged, programmed to heat and dry 5 ° C / min to 250 ° C, heat preservation 0.5 h, 550 ° C high temperature After calcination for 4 h, a Co-Ce-O _x /Ce _0.5 -Zr _0.4 -Ti _0.1 O ₂ /cordierite catalyst with a loading of 20% was prepared.

Example 3

(1) Carrier pretreatment

The cordierite honeycomb ceramic carrier was taken, immersed in a 10 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 2 hours, and washed with water under ultrasonic assistance until the solution was neutral, dried at 100 ° C, calcined at 400 ° C for 1 h, and set aside.

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _0.1 -Zr _0.8 -Ti _0.1 O _{2 of the} three-dimensional porous honeycomb skeleton structure was prepared by the complex impregnation method. Prepare 0.14moL/L lanthanum nitrate, 1.12moL/L zirconium acetate, 0.14moL/L titanium sulfate and 0.28moL/L acrylamide mixed solution, cook in a water bath to make it sol, then place the cordierite carrier in the sol. In the middle, it was taken out to dry, dried at 120 ° C, and calcined at 500 ° C for 4 h to obtain a Ce _0.1 -Zr _0.8 -Ti _0.1 O ₂ coating modified cordierite support having a loading of 10%.

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide was prepared by in-situ autoignition synthesis method, and 0.70LL/L lanthanum nitrate, 0.21moL/L cobalt nitrate and 0.28moL/L malic acid mixed solution were prepared. After being completely dissolved by stirring, Ce _0.8 -Zr was prepared. _{0.1 -} Ti _0.1 O ₂ coating modified cordierite carrier is immersed in the solution, taken out after saturation, naturally dried and aged, programmed to heat and dry 5 ° C / min to 250 ° C, heat preservation 0.5 h, 500 ° C high temperature After calcination for 6 h, a Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst with a loading of 20% was prepared.

Example 4

(1) Carrier pretreatment

The cordierite honeycomb ceramic carrier was taken, immersed in a 15 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 2 hours, and washed with ultrasonic aid until the solution was neutral, dried at 100 ° C, calcined at 450 ° C for 1 h, and set aside.

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _0.1 -Zr _0.8 -Ti _0.1 O _{2 of the} three-dimensional porous honeycomb skeleton structure was prepared by the complex impregnation method. Prepare a mixed solution of 0.14moL/L lanthanum nitrate, 1.12moL/L zirconium acetate, 0.14moL/L titanium oxalate oxalate and 0.28mol/L citric acid, cook in a water bath to make it sol, and then add cordierite. The carrier was placed in a sol, taken out and dried, dried at 120 ° C, and calcined at 500 ° C for 4 h to obtain a Ce _0.1 -Zr _0.8 -Ti _0.1 O ₂ coating modified cordierite support having a loading of 10%.

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide was prepared by in-situ autoignition synthesis method, and 0.35 moL/L lanthanum nitrate, 1.05 moL/L cobalt nitrate, and 0.28 moL/L malic acid mixed solution were prepared. After being completely dissolved by stirring, Ce _0.8 -Zr was prepared. _{0.1 -} Ti _0.1 O ₂ coating modified cordierite carrier is immersed in the solution, taken out after saturation saturation, naturally dried and aged, programmed to heat and dry 5 ° C / min to 250 ° C, heat preservation 0.5 h, 550 ° C high temperature After calcination for 6 h, a Co-Ce-O _x /Ce _0.8 -Zr _0.1 -Ti _0.1 O ₂ /cordierite catalyst with a loading of 10% was prepared.

Example 5

(1) Carrier pretreatment

The cordierite honeycomb ceramic carrier was taken, immersed in a 15 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 1 h, washed with water under ultrasonic assistance until the solution was neutral, dried at 100 ° C, calcined at 500 ° C for 1 h, and set aside.

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce _0.4 -Zr _0.4 -Ti _0.2 O _{2 of the} three-dimensional porous honeycomb skeleton structure was prepared by the complex impregnation method. Prepare a mixed solution of 1.12moL/L lanthanum nitrate, 1.12moL/L zirconium acetate, 0.56moL/L titanium sulfate and 0.28moL/L complexing agent (0.14moL/L citric acid and 0.14moL/L glycine), and cook in water bath. It is made into a sol shape, then the cordierite carrier is placed in a sol, taken out and dried, dried at 120 ° C, and calcined at 500 ° C for 4 h to obtain a Ce _0.1 -Zr _0.8 -Ti _0.1 O ₂ coating with a loading of 20%. Layer modified cordierite carrier.

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide was prepared by in-situ autoignition synthesis method, and 0.35 moL/L lanthanum nitrate, 1.05 moL/L cobalt nitrate, 0.28 moL/L polyhydroxy organic acid (0.14 moL/L citric acid and 0.14 moL/) were prepared. After the mixed solution of L oxalic acid is completely dissolved by stirring, the cordierite carrier modified by Ce _0.4 -Zr _0.4 -Ti _0.2 O ₂ coating is immersed in the solution, and after being immersed and saturated, it is taken out, naturally dried and aged, and programmed to be heated. Drying 5 ° C / min to 250 ° C, holding 0.5 h, 550 ° C high temperature roasting for 6 h, prepared a loading of 10% Co-Ce-O _x /Ce _0.4 -Zr _0.4 -Ti _0.2 O ₂ / cordierite catalyst.

Claims

A supported VOCs catalytic combustion catalyst, characterized in that the catalyst comprises a cordierite ceramic as a carrier, and the coating is coated with a coating and an active component from the inside to the outside in a carrier, the coating being a three-dimensional porous honeycomb skeleton structure. A ternary solid solution having a molecular formula of Ce x -Zr y -Ti 1-xy -O 2 , the active component being a cobalt ruthenium composite oxide, based on the mass of the support, the mass of the coating and the active component loading The fractional content is 5% to 10% and 5% to 20%, respectively.
The supported VOCs catalytic combustion catalyst according to claim 1, wherein in the Ce x -Zr y -Ti 1-xy -O 2 , 0 < x < 1, 0 < y < 1, x + y < 1.
The supported VOCs catalytic combustion catalyst according to claim 1, wherein the cobalt ruthenium composite oxide has a molar ratio of Ce/Co = 0.01 to 1.
A method of preparing a supported VOCs catalytic combustion catalyst according to claim 1, comprising the steps of:

(1) Carrier pretreatment

(2) Preparation of catalyst coating

The three-dimensional solid solution Ce x -Zr y -Ti 1-xy -O 2 of three-dimensional porous honeycomb skeleton structure is prepared by complex impregnation method, and a mixed solution of cerium salt, zirconium salt and titanium is prepared by adding a complexing agent, and a complexing agent is added. The kettle is cooked in a water bath to form a sol, and then the cordierite ceramic carrier is placed in a sol, taken out to dry, dried, and calcined to obtain a Ce x -Zr y -Ti 1-xy -O 2 coating modified ruthenium. Bluestone ceramic carrier;

(3) Preparation of catalyst active component

The active component cobalt ruthenium composite oxide is prepared by in-situ auto-ignition synthesis method, and a mixed solution of a certain concentration of cobalt salt, strontium salt and organic templating agent is prepared, and after being completely dissolved by stirring, Ce x -Zr y -Ti 1-xy is prepared. The -O 2 coating modified cordierite carrier is immersed in the solution, taken out after being saturated with the immersion, naturally dried and aged, heated and dried by a programmed temperature, and promotes the combination of the lone pair of electrons and the metal ions in the organic template. Forming a stable cage structure, realizing the in-situ synthesis of the active component precursor on the surface, high-temperature baking, preparing uniform dispersion of the active component, high-strength combination of the carrier and the coating, and the structure between the active component and the coating catalyst.
The method for preparing a supported VOCs catalytic combustion catalyst according to claim 4, wherein in the step (1), the carrier pretreatment method is as follows:

The cordierite honeycomb ceramic carrier is taken, immersed in a 5-20 wt% nitric acid solution, heated to boiling, taken out after heat treatment for 1 h to 4 h, washed with water under ultrasonic assistance until the solution is neutral, dried, calcined, and set aside.
A method of preparing a supported VOCs catalytic combustion catalyst according to claim 5, wherein

During the pretreatment of the carrier, the drying temperature is 80 to 100 ° C, and the baking condition is 400 to 550 ° C, 0.5 to 1 h;

In the preparation process of the catalyst coating, the drying temperature is 80-120 ° C, and the baking condition is 400-650 ° C, 2-6 h;

During the preparation of the active component of the catalyst, the high temperature calcination condition is 450 to 750 ° C for 2 to 6 hours.
The method for preparing a supported VOCs catalytic combustion catalyst according to claim 4 or 6, wherein in the preparation of the active component of the catalyst, the conditions of temperature-programmed heating and drying are: 5 ° C / min to 200 - 250 ° C , heat preservation 0.5 ~ 2h.
The method for preparing a supported VOCs catalytic combustion catalyst according to claim 4, wherein in the steps (2) and (3), the cerium salt is one or more of cerium nitrate, cerium chloride and cerium acetate. In the step (2), the zirconium salt is one or more of zirconium nitrate, zirconium oxychloride and zirconium acetate, and the titanium source is titanium titanyl oxalate and/or titanium sulfate, and the complexing agent is One or more of citric acid, glycine and acrylamide. In the step (3), the cobalt salt is one or more of cobalt nitrate, cobalt oxychloride and cobalt acetate, and the organic template is polyhydroxyl. Organic acid.
The method for preparing a supported VOCs catalytic combustion catalyst according to claim 8, wherein the polyhydroxy organic acid is one or more of malic acid, citric acid and oxalic acid.