CN114700083A - A kind of composite catalyst for low concentration VOC and preparation method thereof - Google Patents

Abstract

The invention provides a composite catalyst for low-concentration VOC, comprising a carrier and a coating, the coating is arranged on the carrier, and the loading amount is 100-250 g/L; the raw material components used in the coating include: Active component and modifier, the mass ratio of the active component and modifier is 1:1-4:1; the active component includes copper oxide and manganese oxide; the modifier is modified γ ‑ Alumina. The present invention also provides a method for preparing the composite catalyst, including step S1, preparing modified γ-alumina; step S2, preparing coating slurry; and step S3, preparing the composite catalyst. The composite catalyst prepared by the invention has low cost, is not easy to be poisoned and deactivated, and has low catalytic temperature.

Description

A kind of composite catalyst for low concentration VOC and preparation method thereof

technical field

The invention relates to the technical field of volatile organic gas purification, in particular to a composite catalyst for low-concentration VOC and a preparation method thereof.

Background technique

In the atmosphere, the concentration value of low-concentration volatile organic gas (hereinafter referred to as VOC) generally does not exceed 2000 mg/Nm ³ . Most of the existing catalysts for treating VOC are precious metal catalysts, and their active components are mainly composed of platinum/palladium, and the active component content is as high as 500-2000 mg/L. Although this type of precious metal catalyst can handle high and low concentrations of VOCs, its active components, platinum/palladium, are rare precious metals and are expensive, resulting in high usage costs for customers. In addition, impurities such as P and organosilicon are contained in VOCs, which can easily lead to the poisoning of the active components platinum/palladium and the loss of catalytic activity.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a composite catalyst for low-concentration VOC and a preparation method thereof, which are used to solve the problems of high cost and easy poisoning and deactivation of noble metal catalysts. The specific technical solutions are as follows:

A composite catalyst for low-concentration VOC, comprising a carrier and a coating, the coating is arranged on the carrier, and the loading is 100-250 g/L; the raw material components used in the coating include active components and A modifier, the mass ratio of the active component to the modifier is 1:1-4:1; the active component includes copper oxide and manganese oxide; the modifier is modified γ-alumina.

In some embodiments, the mass ratio of the copper oxide to the manganese oxide is 1:3-3:1.

In some embodiments, the raw material components used in the modification of the modified γ-alumina include strontium nitrate solution, yttrium nitrate solution and γ-alumina; the strontium nitrate solution, yttrium nitrate solution and γ-oxide The mass ratio of aluminum is 0.5:0.5:150-2:5:150.

In some embodiments, the mass fraction of the strontium nitrate solution is 30%-60%; the mass fraction of the yttrium nitrate solution is 40%-65%.

In some embodiments, the carrier is a ceramic carrier or an iron-chromium-aluminum alloy carrier; the porosity of the ceramic carrier or the iron-chromium-aluminum alloy carrier is 200-400 mesh.

A preparation method of a described composite catalyst for low-concentration VOC, comprising the steps:

Step S1, preparation of modified γ-alumina

First, weigh the required mass of γ-alumina, add the required mass of strontium nitrate solution and yttrium nitrate solution, and stir for 2-4 hours; secondly, add a thickening agent and continue stirring for 20-25 hours; then, dropwise add pH Adjusting the pH of the agent to 10-11 to obtain a pre-formulation; finally, drying and calcining the pre-formulation to obtain modified γ-alumina;

Step S2, prepare coating slurry

Weigh the required quality of modified γ-alumina and active components and add them into water, and after stirring for 1-3 hours, ball-mill to a D90 of 20-25 μm to obtain a coating slurry;

Step S3, preparing composite catalyst

The coating slurry with the required loading amount is coated on the carrier, and the composite catalyst is prepared after drying and calcining.

In some embodiments, in step S1, the thickening agent is hydroxymethyl cellulose, and its usage amount is 0.08-0.12 times that of γ-alumina; the pH adjusting agent is sodium hydroxide solution; the The drying temperature is 110-120°C; the roasting temperature is 550-650°C, and the roasting time is 4.5-5.5h.

In some embodiments, in step S3, the drying temperature is 140-160° C.; the roasting temperature is 500-600° C., and the roasting time is 3.5-4.5 h.

Apply the technical scheme of the present invention, at least have the following beneficial effects:

(1) The composite catalyst for low-concentration VOC described in the present invention adopts the active components copper oxide and manganese oxide to have a relatively high specific surface area, reaching more than 150 m ² /g, which is beneficial to the adsorption, reaction and reaction of low-concentration VOC. In addition, the active component occupies a high proportion, which increases the number of active sites of the composite catalyst, which is beneficial to improve the chance of low-concentration VOC contacting the active site; moreover, the cost of the active component is much lower than that of the precious metal platinum/ Palladium greatly reduces the cost of the composite catalyst, and the active components copper oxide and manganese oxide are resistant to impurities such as P and silicone contained in VOC, which greatly reduces the possibility of poisoning and deactivation. The invention adopts the modified γ-alumina, which can greatly improve the high temperature resistance stability and oxidation performance of the composite catalyst, thereby improving the catalytic oxidation performance of the composite catalyst, facilitating the improvement of the conversion rate of organic waste gas and realizing the purification effect. The setting of the loading on the coating of the invention enhances the adsorption of low-concentration VOCs on the composite catalyst coating, and improves the mass transfer efficiency. The composite catalyst prepared by the invention is suitable for the treatment of low-concentration VOC, can reduce the catalytic temperature and save energy.

(2) The preparation method of the composite catalyst for low-concentration VOC described in the present invention has the advantages of simplified steps, convenient operation, easy control of parameters, and easy popularization.

Detailed ways

The technical solutions in the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the protection scope of the present invention.

Example 1:

A composite catalyst for low-concentration VOC, comprising a carrier and a coating, the coating is arranged on the carrier, and the loading is 100-250 g/L; the raw material components used in the coating include active components and A modifier, the mass ratio of the active component to the modifier is 3:1; the active component includes copper oxide and manganese oxide; the modifier is modified γ-alumina.

The mass ratio of the copper oxide to the manganese oxide is 1:3.

The raw material components used in the modification of the modified γ-alumina include strontium nitrate solution, yttrium nitrate solution and γ-alumina; the mass ratio of the strontium nitrate solution, yttrium nitrate solution and γ-alumina is 1.2 :3.5:150.

The mass fraction of the strontium nitrate solution is 45%; the mass fraction of the yttrium nitrate solution is 50%.

The carrier is a ceramic carrier (dimensions are 150mm×150mm×50mm), and its porosity is 400 meshes.

A preparation method of a described composite catalyst for low-concentration VOC, comprising the steps:

Step S1, preparation of modified γ-alumina

First, weigh 150 g of γ-alumina, add 1.2 g of strontium nitrate solution and 3.5 g of yttrium nitrate solution, and stir for 3 h; secondly, add 18 g of thickener (specifically, hydroxymethyl cellulose), and continue to stir for 24 h; then, Add pH adjuster (specifically, sodium hydroxide solution, with a mass fraction of 30%) dropwise to pH 11 to obtain a pre-formulation; finally, the pre-formulation is dried at 120° C. and calcined at 600° C. for 5 hours to obtain a modified γ-alumina;

Step S2, prepare coating slurry

100g of modified γ-alumina and 300g of active components were weighed and added to 1250g of water, and after stirring for 2h, ball-milled to a D90 of 25 μm to obtain a coating slurry;

Step S3, preparing composite catalyst

225g of the coating slurry was uniformly coated on the carrier, dried at 150°C and calcined at 550°C for 4 hours to obtain a composite catalyst.

Example 2:

Different from Example 1, in step S1, the amount of the strontium nitrate solution is 4g, the amount of the yttrium nitrate solution is 8g, and the amount of the thickener is 15g.

Example 3:

Different from Example 1, in step S2, the amount of the modified γ-alumina is 300 g, and the amount of the active component is 100 g.

Example 4:

Different from Example 1, in step S1, the amount of the strontium nitrate solution is 4g, the amount of the yttrium nitrate solution is 8g, and the amount of the thickener is 15g; in step S2, the modified γ-oxidation The amount of aluminum is 300g, and the amount of the active component is 100g.

Example 5:

Different from Example 1, in step S1, the amount of the strontium nitrate solution is 3g, and the amount of the yttrium nitrate solution is 6g; in step S2, the amount of the modified γ-alumina is 200g, the active group The dosage is 200g.

Comparative Example 1:

Take 400 g of unmodified γ-alumina and add it to 1250 g of water, and after stirring for 2 hours, ball-mill to a D90 of 25 μm to obtain a coating slurry; add platinum nitrate solution and stir until uniform, wherein the quality of platinum nitrate is relative to the final prepared The dosage of 1L finished precious metal catalyst is 659mg; the coating with a net content of 112.5g is uniformly coated on the carrier (specifically, a ceramic carrier (size is 150mm×150mm×50mm) with a porosity of 400 meshes by quantitative coating technology. ), dried at 150 °C, and then calcined at 550 °C for 4 h to obtain the finished precious metal catalyst.

Comparative Example 2:

Take 350g of unmodified γ-alumina and 50g of copper oxide and add it to 1250g of water, and after stirring for 2 hours, ball-mill to D90 of 25 μm to obtain a coating slurry; add platinum nitrate solution and stir until uniform, wherein the mass of platinum nitrate is relative to The amount of the final prepared 1L finished precious metal catalyst is 659mg; the coating with a net content of 112.5g is uniformly coated on the carrier (specifically a ceramic carrier (size is 150mm×150mm×50mm), and its pores are uniformly coated by quantitative coating technology. 400 mesh), drying at 150 °C, and then calcining at 550 °C for 4 h to obtain the finished precious metal catalyst.

Comparative Example 3:

350g of unmodified γ-alumina, 25g of copper oxide and 25g of manganese oxide were added to 1250g of water, and after stirring for 2 hours, ball-milled to a D90 of 25 μm to obtain a coating slurry; a platinum nitrate solution was added, and stirred until uniform. The mass of platinum is 659 mg relative to the final preparation of 1 L of finished precious metal catalyst; the coating with a net content of 112.5 g is uniformly coated on the carrier (specifically, a ceramic carrier (size is 150 mm × 150 mm × 50 mm) using quantitative coating technology. ) with a porosity of 400 mesh), drying at 150 °C, and then calcining at 550 °C for 4 h to obtain a finished precious metal catalyst.

Comparative Example 4:

Take 400 g of strontium nitrate (3.2 g in mass) modified γ-alumina and add it to 1250 g of water, and after stirring for 2 hours, ball mill to a D90 of 25 μm to obtain a coating slurry; add platinum nitrate solution and stir until uniform. The mass of the final prepared 1L finished precious metal catalyst is 659mg; the coating with a net content of 112.5g is uniformly coated on the carrier (specifically, a ceramic carrier (size is 150mm×150mm×50mm) by quantitative coating technology. , its porosity is 400 mesh), drying at 150 °C, and then calcining at 550 °C for 4 h to obtain the finished precious metal catalyst.

Comparative Example 5:

Take 350 g of strontium nitrate (2.8 g in mass) modified γ-alumina, 25 g of copper oxide and 25 g of manganese oxide and add them to 1250 g of water, and after stirring for 2 hours, ball-mill to D90 of 25 μm to obtain a coating slurry; add platinum nitrate solution, Stir until uniform, wherein, the quality of platinum nitrate is 659mg relative to the consumption of the final 1L finished product precious metal catalyst prepared; Adopt quantitative coating technology to uniformly coat the coating with a net content of 112.5g on a carrier (specifically a ceramic carrier ( The size is 150mm×150mm×50mm), and its porosity is 400 mesh), drying at 150°C, and then calcining at 550°C for 4 hours to obtain the finished precious metal catalyst.

The composite catalysts prepared in Examples 1-5 and the precious metal catalysts prepared in Comparative Example 1 were subjected to fresh state catalytic performance experiments and aging state catalytic performance experiments, respectively. The experimental process is as follows:

1) Fresh state catalytic performance experiment

From the composite catalysts prepared in Examples 1-5 and the precious metal catalysts prepared in Comparative Example 1, 100 samples of equal quality were taken, and were not aged for fresh catalytic performance experiments. The test conditions are as follows: 200ppm propylene, 10% (volume fraction) O ₂ , 5% (volume fraction) H ₂ O, the balance gas is N ₂ , the reaction temperature is room temperature -300°C, and the space velocity is 20000h ^-1 .

2) Aged state catalytic performance experiment

From the composite catalysts prepared in Examples 1-5 and the precious metal catalyst prepared in Comparative Example 1, 100 samples of equal quality were taken, and after aging treatment, an aging catalytic performance experiment was carried out, wherein the aging conditions were: The samples were placed in an aging test chamber at 650°C for thermal aging for 24h. The test conditions are the same as 1).

Through 1)-2) experimental tests, the temperature of T ₅₀ (representing the temperature when the conversion rate of reactant propylene reaches 50%) and sample T ₁₀₀ (representing the temperature when the conversion rate of reactant propylene reaches 100%) of the corresponding sample is obtained, specifically The results are shown in Table 1.

Table 1

It can be known from the data in Table 1 that, compared with Comparative Examples 1-5, the composite catalyst prepared in Examples 1-5 of the present invention has a lower catalytic temperature when T ₅₀ and T ₁₀₀ are completed. This shows that the composite catalyst prepared by the present invention has better catalytic oxidation performance.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. a composite catalyst for low-concentration VOC, characterized in that, comprising a carrier and a coating, the coating is arranged on the carrier, and the loading is 100-250g/L; The components include active components and modifiers, and the mass ratio of the active components to the modifiers is 1:1-4:1; the active components include copper oxide and manganese oxide; the modifiers are modified Sexual gamma-alumina. 2. The composite catalyst for low-concentration VOC according to claim 1, wherein the mass ratio of the copper oxide to the manganese oxide is 1:3-3:1. 3. The composite catalyst for low-concentration VOC according to claim 2, wherein the raw material components used in the modification of the modified γ-alumina include strontium nitrate solution, yttrium nitrate solution and γ- Alumina; the mass ratio of the strontium nitrate solution, the yttrium nitrate solution and the γ-alumina is 0.5:0.5:150-2:5:150. 4. The composite catalyst for low-concentration VOC according to claim 3, wherein the mass fraction of the strontium nitrate solution is 30%-60%; the mass fraction of the yttrium nitrate solution is 40%-65% %. 5. The composite catalyst for low-concentration VOC according to claim 4, wherein the carrier is a ceramic carrier or an iron-chromium-aluminum alloy carrier; the porosity of the ceramic carrier or the iron-chromium-aluminum alloy carrier is 200 -400 mesh. 6. a preparation method for the composite catalyst of low concentration VOC as described in any one of claim 3-5, is characterized in that, comprises the steps: Step S1, preparation of modified γ-alumina First, weigh the required mass of γ-alumina, add the required mass of strontium nitrate solution and yttrium nitrate solution, and stir for 2-4 hours; secondly, add a thickening agent and continue stirring for 20-25 hours; then, dropwise add pH Adjusting the pH of the agent to 10-11 to obtain a pre-formulation; finally, drying and calcining the pre-formulation to obtain modified γ-alumina; Step S2, prepare coating slurry Weigh the required quality of modified γ-alumina and active components and add them into water, and after stirring for 1-3 hours, ball-mill to a D90 of 20-25 μm to obtain a coating slurry; Step S3, preparing composite catalyst The coating slurry with the required loading amount is coated on the carrier, and the composite catalyst is prepared after drying and calcining. 7. The preparation method according to claim 6, characterized in that, in step S1, the thickener is hydroxymethyl cellulose, and its usage amount is 0.08-0.12 times that of γ-alumina; the pH The regulator is sodium hydroxide solution; the drying temperature is 110-120°C; the roasting temperature is 550-650°C, and the roasting time is 4.5-5.5h. 8. The preparation method according to claim 6, wherein in step S3, the drying temperature is 140-160°C; the roasting temperature is 500-600°C, and the roasting time is 3.5-4.5°C h.