CN109999892A - A kind of glycol-modified CO2The preparation method and application of reforming catalyst - Google Patents

Abstract

The invention discloses a preparation method and application of an ethylene glycol modified _CO2 reforming catalyst, and belongs to the field of waste gas treatment technology and environmental protection catalysis environment. First, a metered amount of Ni(NO ₃ ) ₂ ·6H ₂ O (the total mass of the carrier and the active component Ni is 100%, and the mass percentage of the active component Ni in the catalyst is 10%) is added to ethylene glycol (EG) In the solution, stir until completely dissolved to obtain a transparent solution; then add the weighed MCM-41 molecular sieve carrier into the obtained transparent solution, dipping to obtain a mixed slurry; the above-mentioned mixed slurry is placed in an oil bath pot, and the oil bath is steamed. drying to obtain a dry powder; drying in an oven to obtain a catalyst precursor; air roasting to obtain an ethylene glycol-modified 10% Ni/MCM‑41‑EG catalyst. The catalytic activity of the catalyst prepared by the method is obviously improved, and the process is simple, easy to operate and low in cost.

Description

A kind of preparation method and application of ethylene glycol modified CO2 reforming catalyst

technical field

The invention belongs to the field of _CO2 reforming methane reaction, and in particular relates to a preparation method and application of an ethylene glycol modified _CO2 reforming catalyst.

Background technique

With the depletion of oil resources and the increasingly serious environmental pollution, the development and utilization of clean and cheap fuel resources have received widespread attention from all countries. Carbon dioxide reforming methane can simultaneously utilize the two greenhouse gases _CH4 and _CO2 , and generate _H2 and CO2 syngas to further carry out the Fischer-Tropsch reaction and reduce the pressure caused by the energy crisis. Therefore, in recent years, carbon dioxide reforming methane received extensive attention.

Chinese patent CN 105709724A discloses a magnesium-aluminum oxide solid solution-supported ruthenium methane dry reforming catalyst and a preparation method thereof. The mass percentage content of Ru in the catalyst is 0.5%-4wt%, and the catalyst is prepared by calcining and impregnating magnesium-aluminum layered composite hydroxide as a precursor. Although the catalyst has good stability, its preparation process is cumbersome and the content of precious metals is high. For carbon dioxide reforming methane, catalysts with noble metals as active components show better catalytic performance, but the reserves of noble metals are limited and expensive. Therefore, Ni-based catalysts with catalytic activity comparable to noble metal catalysts have received extensive attention in recent years. . However, the main problem that hinders its industrialization is the deactivation of the catalyst caused by carbon deposition and sintering. Therefore, improving the carbon deposition resistance of nickel-based catalysts and preparing new reforming catalysts with high activity and strong stability are the current research in this field. Focus.

Chinese patent CN 106944067A discloses a preparation method of a catalyst for methane carbon dioxide reforming to syngas. The catalyst uses Ni as an active component and silica as a carrier, and is prepared from raw materials such as nickel nitrate, sodium silicate and dilute nitric acid through simple precipitation, aging, washing, drying, grinding, reduction and other steps. The catalyst prepared by this method is used for reforming reaction and exhibits good catalytic performance, but its preparation process is long and time-consuming.

He et al. (CO ₂ reforming of methane to syngas over highly-stable Ni/SBA-15 catalysts prepared by P123-assisted method[J]. International journal of hydrogen energy, 2016, 41(3): 1513-1523.) used surface active P123 was used to prepare carrier SBA-15, and then P123 was added with nickel nitrate aqueous solution to co-impregnate SBA-15, water bath, drying and calcination to obtain Ni/SBA-15 catalyst with high reforming activity and stability. However, the price of surfactant P123 and the preparation cost of carrier SBA-15 are relatively expensive. Muhammad Awais Naeem et al. (Syngas Production from Dry Reforming of Methane over Nano Ni Polyol Catalysts International Journal of Chemical Engineering and Applications, 2013 Vol. 4(5): 315-320) used ethylene glycol, PVP and aqueous nickel nitrate to co-impregnate nanoparticles, Nickel colloid is formed under alkaline conditions, and the catalyst is obtained after rotary distillation, washing, drying and roasting, which has high reforming activity and stability, but the preparation process is relatively complicated.

Although the catalysts prepared by the above-mentioned patent methods and literature methods have obtained better reaction performance of carbon dioxide reforming to syngas, there are still problems such as high cost, complicated preparation process, and difficulty in industrialization. Therefore, the research on nickel-based reforming catalysts with simple preparation process, low cost and excellent performance is an urgent need for industrial application. In the conventional impregnation method, which is simple and easy to operate, alcohols are modified to prepare a supported Ni/MCM-41 catalyst, and the influence of alcohols on the structure and reforming catalytic activity of the nickel-based catalyst supported by the mesoporous molecular sieve carrier is studied. Rarely reported.

The design idea of this patent is to prepare a supported Ni-based catalyst with highly dispersed active components. Firstly, the mesoporous molecular sieve MCM-41 with high specific surface area is used as the carrier to support the active component Ni, in order to improve the dispersion of catalytic activity and reduce the particle size; in the preparation process, different alcohols are introduced for modification to further increase the catalytic activity The interaction between the components and the carrier enhances the adsorption capacity of the catalyst for carbon dioxide, thereby improving the catalytic activity and stability of the catalyst. Therefore, we first prepared Ni/MCM-41 catalysts with different loadings of active components, optimized the content of active components, and its initial activity was higher than that of the low specific surface area catalyst 10%Ni/Al ₂ O ₃ . However, the stability of 10%Ni/MCM-41 catalyst is not good, indicating that the interaction between the active component Ni and MCM-41 is relatively weak. After consulting a large number of literatures and preliminary exploration, alcohols with different carbon chain numbers and hydroxyl numbers were introduced to enhance and modify the catalyst. Therefore, methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol and glycerol were screened to modify the catalyst. It was thought that glycerol has a polyol hydroxyl group, which can significantly enhance its adsorption of CO ₂ . The activity and stability of the catalyst increased, but the results were the opposite of what was expected. Ethanol, n-propanol, n-butanol and ethylene glycol showed better catalytic activity in the modification process. The initial activity of the reaction is good, is the stability the same? Therefore, we compared their stabilities and found that the stability of different alcohols after modification was significantly different, and the best one was ethylene glycol modification. Next, we further explored the influence of drying methods (conventional oil bath drying and rotary distillation drying) and roasting atmosphere (air roasting and nitrogen roasting). We thought that rotary distillation and nitrogen roasting could improve the catalytic activity of the catalyst, but the results were unsatisfactory. . Therefore, the simple and easy-to-operate conventional drying and air roasting were finally selected. To further improve the catalytic activity, we optimized the impregnation volume and impregnation time of ethylene glycol.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method and application of an ethylene glycol modified CO ₂ reforming catalyst. The method has the advantages of simple process, easy operation and low cost. The reforming catalyst prepared by ethylene glycol modification significantly improved the catalytic activity and stability of the catalyst. Compared with the unmodified 10% Ni/MCM-41, the methane conversion rate at 750°C was 85.38% (improved). 18.87%), the carbon dioxide conversion was 91.00% (15.18% increase), and the CO yield was 83.87% (8.65% increase). The stability evaluation for 30h showed that after the reaction for 30h, the deactivation rate of the catalyst to _CH4 conversion was 16.18%. For achieving the above object, the technical scheme adopted in the present invention is as follows:

A preparation method of an ethylene glycol-modified _CO reforming catalyst comprises the following steps:

a. Add the metered amount of Ni(NO ₃ ) ₂ ·6H ₂ O (the total mass of the carrier and the active component Ni is 100%, and the mass percentage of the active component Ni in the catalyst is 10%) into ethylene glycol (EG ) solution, stirring until completely dissolved to obtain a transparent solution;

b, adding the measured MCM-41 molecular sieve carrier to the transparent solution obtained in step a, and dipping to obtain a mixed slurry;

c, place the mixed slurry of step b in an oil bath pot, and evaporate to dryness in the oil bath to obtain dry powder;

d. The powder obtained in step c is dried in an oven to obtain a catalyst precursor;

e. The catalyst precursor obtained in step d is calcined to obtain a 10% Ni/MCM-41-EG catalyst modified with ethylene glycol.

According to the above scheme, the different kinds of alcohols are methanol, ethanol, ethylene glycol, n-propanol, isopropanol, n-butanol and glycerol.

According to the above scheme, in order to achieve better carbon dioxide reforming reaction activity and stability, it is preferred that the alcohols be added as ethylene glycol.

According to the above scheme, the impregnation volume is 10ml-40ml.

According to the above scheme, in order to achieve better carbon dioxide reforming reaction performance, the volume of alcohols is preferably 30ml.

According to the above scheme, the soaking time is 45min-720min.

According to the above scheme, in order to achieve better carbon dioxide reforming reaction performance, the preferred immersion time is 45min.

According to the above scheme, the drying methods are conventional oil bath drying and rotary distillation drying.

According to the above scheme, in order to achieve better carbon dioxide reforming reaction performance, the preferred drying method is conventional oil bath drying.

According to the above scheme, the firing atmosphere is air and nitrogen.

According to the above scheme, in order to achieve better carbon dioxide reforming reaction performance, the preferred firing atmosphere is air.

According to the above scheme, the carrier is MCM-41 molecular sieve.

According to the above scheme, the total mass of the carrier and the active component Ni is 100%, and the mass fraction of the active component Ni in the catalyst is 10%.

Compared with the prior art, the present invention has the following advantages:

(1) The ethylene glycol modified catalyst of the present invention is used for the CH ₄ /CO ₂ reforming reaction, and the catalytic activity of the catalyst is significantly improved compared with that of the nickel-based catalyst without alcohol modification. At 750° C. , the methane conversion rate, carbon dioxide conversion rate, and CO yield can reach up to 85%, 92%, and 86%, respectively, which are 20%, 17%, and 11% higher than the conventional 10% Ni/MCM-41 catalyst, respectively. . The stability evaluation for 30h showed that after the reaction for 30h, the deactivation rate of the catalyst to _CH4 conversion was 16.18%.

(2) The preparation method is simple in process, and the preparation conditions are easy to operate and control.

Description of drawings

FIG. 1 is a test chart of catalytic performance of catalysts prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Example 6 and Example 7.

Figure 2 shows the catalytic performance of catalysts prepared in Example 1, Example 9, Example 10, and Example 11

3 is a test chart of catalytic performance of catalysts prepared in Example 1, Example 4, Example 12, Example 13, Example 14 and Example 15.

4 is a test chart of the catalytic performance of the catalysts prepared in Example 1, Example 4 and Example 16.

FIG. 5 is a test chart of the catalytic performance of the catalysts prepared in Example 1, Example 4 and Example 17. FIG.

FIG. 6 is a graph showing the stability test of catalysts prepared in Example 1, Example 3, Example 4, Example 5 and Example 7. FIG.

FIG. 7 is a characterization diagram of H ₂ -TPR of catalysts prepared in Example 1 and Example 4. FIG.

Detailed ways

The present invention is further described below through some embodiments, but the present invention is not thereby limited.

Example 1 Preparation of 10% Ni/MCM-41 catalyst

Add 0.991g Ni(NO ₃ ) ₂ ·6H ₂ O to 30ml of distilled water and stir to dissolve, add 1.8g MCM-41 molecular sieve carrier, soak for 45min at room temperature, evaporate the above mixed slurry in a water bath at 110°C, and dry at 110°C 12h, calcined at 550℃ for 4h in air atmosphere, 10%Ni/MCM-41 catalyst was prepared.

Evaluation of catalysts

The activity evaluation of the catalyst was carried out in a self-made continuous flow fixed bed reactor. The reaction tube is a quartz tube with an inner diameter of 6 mm and a length of 33 cm. The reaction temperature is measured by a thermocouple placed in the middle of the reaction tube, and a temperature-programmed controller is used to control the reaction temperature. The gas flow was controlled by a mass flow meter, the space velocity was 36000ml/(g ^cat ·min), the reaction temperature was 500°C-800°C, and samples were taken every 50°C. On-line detection was performed with a gas chromatograph. The catalytic performance curves of the catalysts at different temperature points are shown in Figure 1. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

Example 2-8, compared with Example 1, the difference is the type of alcohol, and other processes are the same as Example 1. The details are as follows: add 0.991g Ni(NO ₃ ) ₂ ·6H ₂ O to 30ml of different alcohols, stir and dissolve, add 1.8g MCM-41 molecular sieve carrier, and soak for 45min at room temperature. Dry in a water bath or oil bath at a certain temperature, oven at 110°C overnight, and calcined at 550°C for 4 hours in an air atmosphere to obtain a 10% Ni/MCM-41-EG-X catalyst. The catalyst treatment parameters of Examples 2 to 8 are shown in Table 1.

Evaluation of catalysts

According to the evaluation method of Example 1, the catalytic performance curves of the catalyst at different temperature points are shown in Figure 1. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

Examples 9-11, compared with Example 1, the difference is the volume of ethylene glycol impregnation, other processes are the same as Example 1. The details are as follows: add 0.991g Ni(NO ₃ ) ₂ ·6H ₂ O into ethylene glycol of different volumes and stir to dissolve, add 1.8g MCM-41 molecular sieve carrier, soak for 45min at room temperature, then add the above mixed slurry to oil at 160°C Evaporate to dryness in a bath, oven at 110°C overnight, and calcinate at 550°C for 4 hours in an air atmosphere to obtain a 10% Ni/MCM-41-EG(X) catalyst. The catalyst treatment parameters of Examples 9-11 are shown in Table 1.

Evaluation of catalysts

According to the evaluation method of Example 1, the catalytic performance curves of the catalyst at different temperature points are shown in Figure 3. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

In Examples 12-15, compared with Example 1, the difference is the ethylene glycol impregnation time, and other processes are the same as those in Example 1. The details are as follows: add 0.991g Ni(NO ₃ ) ₂ ·6H ₂ O to 30ml of ethylene glycol and stir to dissolve, add 1.8g MCM-41 molecular sieve carrier, and soak the above mixed slurry in an oil bath at 160°C after soaking for different times at room temperature Evaporate to dryness, oven at 110°C overnight, and calcinate at 550°C for 4 hours in an air atmosphere to obtain a 10% Ni/MCM-41-EG-Xmin catalyst. The catalyst treatment parameters of Examples 12-15 are shown in Table 1.

Evaluation of catalysts

According to the evaluation method of Example 1, the catalytic performance curves of the catalyst at different temperature points are shown in Figure 3. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

Example 16, compared with Example 1, differs in the drying method, and other processes are the same as those in Example 1. The details are as follows: add 0.991g Ni(NO ₃ ) ₂ ·6H ₂ O to 30ml of ethylene glycol and stir to dissolve, add 1.8g MCM-41 molecular sieve carrier, soak at room temperature for 45min, rotate the above mixed slurry in a rotary evaporator Distilled to dryness, oven 110°C overnight, calcined at 550°C for 4h in air atmosphere, to obtain 10% Ni/MCM-41-EG-Rotary distillation catalyst. The catalyst treatment parameters of Example 16 are shown in Table 1.

Evaluation of catalysts

According to the evaluation method of Example 1, the catalytic performance curves of the catalyst at different temperature points are shown in Figure 2. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

Example 17, compared with Example 1, differs in the firing atmosphere, and other processes are the same as Example 1. The details are as follows: add 0.991g of Ni(NO ₃ ) ₂ ·6H ₂ O to 30ml of ethylene glycol and stir to dissolve, add 1.8g of MCM-41 molecular sieve carrier, soak for 45min at room temperature, and steam the above mixed slurry in an oil bath at 160°C Dry, oven at 110 °C overnight, and calcined at 550 °C under nitrogen atmosphere for 4 h to obtain 10% Ni/MCM-41-EG-N ₂ catalyst. The catalyst treatment parameters of Example 17 are shown in Table 1.

Evaluation of catalysts

According to the evaluation method of Example 1, the catalytic performance curves of the catalyst at different temperature points are shown in Figure 3. The conversions and CO yields of _CH4 and _CO2 at 750 °C are shown in Table 1.

The specific catalyst treatment parameters and activity evaluation results are shown in Table 1:

Stability evaluation of catalysts

The stability evaluation of the catalyst was carried out in a self-made continuous flow fixed bed reactor. The reaction tube is a quartz tube with an inner diameter of 6 mm and a length of 33 cm. The reaction temperature is measured by a thermocouple placed in the middle of the reaction tube, and a temperature-programmed controller is used to control the reaction temperature. The gas flow was controlled by a mass flow meter, the space velocity was 36000ml/(g ^cat ·min), the reaction temperature was 700°C, the first day was 8h, the second day was 11h, and the third day was 11h, for a total of 30h. On-line detection was performed with a gas chromatograph. The catalytic performance curves of the catalysts prepared in Example 1, Example 3, Example 4, Example 5 and Example 7 at different time points are shown in FIG. 6 .

The specific catalyst stability evaluation results are shown in Table 2:

H ₂ -TPR characterization

In Figure 7, both catalysts showed obvious reduction peaks. Compared with the nickel-based catalyst modified with ethylene glycol, the reduction peak shifted to high temperature, indicating that the addition of ethylene glycol enhanced the interaction between the active component Ni and the support in the catalyst. interaction between.

Claims (13)

1. the preparation method and application of a ethylene glycol modified _CO reforming catalyst, it is characterised in that the method comprises the following steps: a. Add the metered amount of Ni(NO ₃ ) ₂ ·6H ₂ O (the total mass of the carrier and the active component Ni is 100%, and the mass percentage of the active component Ni in the catalyst is 10%) into ethylene glycol (EG ) solution, stirring until completely dissolved to obtain a transparent solution; b, adding the measured MCM-41 molecular sieve carrier to the transparent solution obtained in step a, and dipping to obtain a mixed slurry; c, place the mixed slurry of step b in an oil bath pot, and evaporate to dryness in the oil bath to obtain dry powder; d. The powder obtained in step c is dried in an oven to obtain a catalyst precursor; e. The catalyst precursor obtained in step d is calcined to obtain an ethylene glycol modified 10% Ni/MCM-41-EG catalyst. 2. The preparation method of the ethylene glycol-modified CO ₂ reforming catalyst according to any one of claims 1, wherein the carrier is MCM-41 molecular sieve. 3. The preparation method of the ethylene glycol modified _CO reforming catalyst according to any one of claims 1-2, characterized in that, taking the total mass of the carrier and the active component Ni as 100%, in the catalyst The mass percentage of active component Ni is 10%. 4 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the alcohols are ethylene glycol (EG). 5 . 5 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the impregnation volume of the alcohols is 10-40 ml. 6 . 6 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the impregnation volume of the alcohols is 30 ml. 7 . 7 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the immersion time of the alcohols is 45-720 min. 8 . 8 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the immersion time of the alcohols is 45 min. 9 . 9. the preparation method of the ethylene glycol modified _CO reforming catalyst according to any one of claims 1-8, is characterized in that, the drying mode of described alcohols is conventional oil bath drying and rotary distillation dry. 10 . The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to claim 1 , wherein the drying method of the alcohols is conventional oil bath drying. 11 . 11. The preparation method of the ethylene glycol-modified CO ₂ reforming catalyst according to any one of claims 1-10, wherein the calcination atmosphere of the alcohols is air and nitrogen. 12. The method for preparing an ethylene glycol-modified CO ₂ reforming catalyst according to any one of claims 1-11, wherein the calcination atmosphere of the alcohols is air. 13. The application of the CO ₂ reforming catalyst for ethylene glycol modification according to any one of claims 1 to 12 in CO ₂ /CH ₄ reforming reaction.