WO2013166653A1

WO2013166653A1 - Method for preparing ni-mg/al2o3 catalyst

Info

Publication number: WO2013166653A1
Application number: PCT/CN2012/075184
Authority: WO
Inventors: 刘姣; 余剑; 许光文
Original assignee: 中国科学院过程工程研究所
Priority date: 2012-05-08
Filing date: 2012-05-08
Publication date: 2013-11-14

Abstract

The present invention relates to a method for preparing a Ni-Mg/Al₂O₃ catalyst, the method comprising the steps of: 1) preparing an acid solution I and a basic solution II, wherein the acid solution I comprises an active component raw material, an aid raw material and a metal cation raw material corresponding to a carrier, the basic solution II comprises an anion raw material corresponding to the carrier, the two solutions being mixed to carry out a precipitation reaction, forming a basic reaction condition of a pH value of more than 8, and producing a catalyst precursor; (2) placing the catalyst precursor obtained in step 1) into a high-pressure reaction kettle to carry out a hydrothermal reaction, so as to obtain a catalyst slurry; and 3) washing, filtering and drying the catalyst slurry obtained in step 2) and then baking same to form a catalyst. The method for preparing a catalyst according to the present invention overcomes the disadvantages present in conventional co-precipitation methods such as non-uniformity, low strength, a wide range of change in the pH value during the hydrothermal process, causing difficulty in controlling the process, and high requirements for the material of reaction kettles, etc., and has features such as simplicity and ease of control of the reaction process, good repeatability, low costs, and a low requirement for equipment, etc.

Description

Method for preparing Ni-Mg/AhO. Cuihua agent

The invention relates to the technical field of cross-linking of catalysts and inorganic synthetic chemistry. In particular, the present invention relates to a method for preparing a Ni-Mg/Al ₂ O ₃ catalyst. Background technique

China's coal resources are relatively abundant. For a long time, coal has occupied a major position in China's primary energy consumption structure. Compared with technologies such as coal-based methanol, coal-made dimethyl ether, and direct coal liquefaction, coal-based alternative natural gas has high energy efficiency (more than 60%), low water consumption per unit of heat, low C0 ₂ emissions, and high waste heat utilization rate. Produce high temperature and high pressure steam). Relying on this, if coal is used as raw material to produce substitute natural gas through the methylation reaction, it not only meets the development direction of clean and efficient utilization of coal, but also can be effectively utilized in Xinjiang and Inner Mongolia through pipeline transportation and pressure regulating gas distribution for industrial and civil use. Rich coal resources in remote areas.

The key to the synthesis process of syngas is the development of new high-efficiency catalysts. There are many mature processes and catalysts for the catalytic conversion of a small amount of carbon monoxide into a formazan in a hydrogen-rich atmosphere at home and abroad, and there are related patent reports on coke oven gas, water gas and semi-water gas methylation catalyst. The patents CN1121898 and CN101185892 respectively studied the formazanization catalyst for purifying the ammonia synthesis process and a small amount of CO in the fuel cell raw material gas, wherein the concentration of CO is usually not more than 1%; the patents CN101391218 and CN102259003 report on the methylation of coke oven gas. Catalysts, in which coke oven gas has a high content of formazan (23-27%) and a low CO content, usually 5-8%. The above-mentioned formazanization catalyst and the complete methylation catalyst required for the coal-to-gas project have great differences in performance requirements, and cannot meet the needs of the synthetic gas-methylation process.

Since the 1970s, domestic research and patent technology reports on complete methylation catalysts for syngas have increased. CN101468311 and CN102114425 have used the impregnation method to prepare coal-to-gas methylated Ni/A1 ₂ ₃ catalysts, but such catalysts are usually used. It is only suitable for operation at lower temperature and normal pressure, and sintering and deactivation occur at higher temperatures. CN102029162 Developed a synthesis gas for high temperature and high pressure, fully methylated Ni/Al ₂ by coprecipitation method. 0 ₃ -Zr0 ₂ catalyst, which is a common process for industrially synthesizing powder materials on a large scale, but in the process of coprecipitation, the addition of a precipitant to the solution from the outside causes partial unevenness of the precipitant, thereby preventing precipitation. It occurs uniformly throughout the solution, and thus the catalyst produced by the method has some heterogeneity. Hydrothermal method refers to the formation of a high temperature and high pressure environment in a special sealed reactor using water as a medium by heating the reactor. Under this condition, the agglomeration between the precursor particles is destroyed. At the same time, the particles themselves are dissolved in the hydrothermal medium, and different ion aggregates are formed by hydrolysis and polycondensation. When the concentration of the ion aggregates is relatively saturated with respect to the crystals having less solubility, the crystal nuclei are precipitated. As the crystallization process progresses, the concentration of ionic aggregates in the hydrothermal medium again becomes lower than the solubility of the precursor, so that the dissolution of the precursor continues. Repeatedly, as long as the hydrothermal reaction time is long enough, the precursor will completely dissolve and at the same time generate corresponding grains. The catalyst particles synthesized by the method have high purity, small particle size and uniform distribution, complete grain development, and easy control of crystal form. The reaction and crystal growth can be effectively controlled by adjusting factors such as pH value, reaction temperature, pressure and time.

The patents CN102029161, CN101716513 and CN101716513 all adopt a homogeneous precipitation method to prepare a completely methylated Ni-based catalyst by hydrothermal chemical synthesis process, which firstly mixes the metal salt solution to be precipitated with an excess of water-soluble slow-release alkali (urea, etc.). Pre-form a very uniform system, and then react in a high-pressure hydrothermal kettle. By controlling the temperature of the reactor, the precipitant is slowly decomposed, and the pH of the solution is gradually increased to make the precipitation proceed slowly. Uniform catalyst, high purity and crystallization, good high temperature and hydrothermal stability, but because the precipitant is slowly decomposed, the pH of the solution gradually changes from acidic to alkaline during the reaction. The requirement is high, and the amount of precipitating agent added is affected by various factors such as hydrothermal temperature, reaction time, stirring, etc., and actual industrial production is difficult. Therefore, it is very meaningful to develop a new preparation method of completely formazed Ni-Mg/Al ₂ O ₃ catalyst. Summary of the invention

In order to solve the above problems, the present invention provides a process for preparing a Ni-Mg/Al ₂ O ₃ catalyst. The preparation method of the Ni-Mg/Al ₂ O ₃ catalyst of the invention comprises the following steps:

1) preparing an acidic solution I, an alkaline solution II, wherein the acidic solution I comprises a raw material raw material, an auxiliary raw material and a metal cation raw material corresponding to the carrier, and the alkaline solution II comprises an anionic raw material corresponding to the carrier, and the two solutions are mixed. Precipitation reaction occurs to form an alkaline reaction environment having a pH of 8 or higher to form a catalyst precursor;

2) transferring the catalyst precursor obtained in the step 1) into a high pressure reaction vessel for hydrothermal treatment and aging to obtain a catalyst slurry;

3) The catalyst slurry obtained in the step 2) is washed, filtered, dried and calcined to form a catalyst. A method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to the present invention, step 1) maintaining a precipitation reactor The reaction temperature is 40-90 ° C, and at the same time, by strengthening the mass transfer and heat transfer between the liquid and liquid, such as the strong micro-mixing of the opposite impact of the two solutions, creating a high and uniform supersaturation environment in the precipitation reactor, The two solutions are reacted rapidly to achieve the preparation of the nanocatalyst precursor.

Two-way fluid impact, the intense mutual movement and shearing between the streams from different directions promotes the microscopic mixing of the reactants on the molecular scale, forming a very high instantaneous supersaturation in the reaction zone, and the supersaturation height Uniform, at this time, the rate of nucleation is much larger than the rate of nucleation, a large number of nucleus precipitates, the concentration of reactant molecules decreases rapidly, and no more molecules in the solution accumulate on the nucleus, limiting the increase of nucleation. The extent of the nucleus is also conducive to the stability of the surface.

According to the preparation method of the Ni-Mg/Al ₂ O ₃ catalyst of the present invention, the acidic solution I is a nitrate solution of nickel, magnesium or aluminum, and the nitrate solution may also be an oxalate of nickel, magnesium or aluminum. A solution in which a carbonate or a basic carbonate is dissolved by nitric acid. The alkaline solution is a NaA10 ₂ solution.

Meanwhile, in the present invention, when the hydrothermal method is used to treat the acid-base pairing to form the catalyst precursor, the high-pressure vessel is filled with the wear-resistant balls of different particle size grades, and the ball-milling refinement in the aging process of the pre-precipitation body is realized, thereby forming a uniform size and shape. The appearance of the particles.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst of the present invention, wherein the precipitation aging process can be carried out continuously or intermittently. In batch operation, the two solutions are first reacted in a precipitation reactor to form a catalyst precursor, and after the reaction is completed, transferred to a high pressure reactor for hydrothermal treatment and aging; during continuous operation, the catalyst precursor is controlled by setting a feed flow rate. The residence time in the reactor, the precipitated precursor overflows into the high pressure reactor, and the hydrothermal aging time of the catalyst precursor in the reactor is modulated by changing the size and internal components of the high pressure reactor.

According to the preparation method of the Ni-Mg/Al ₂ O ₃ catalyst of the present invention, the step 2) the reaction temperature in the high pressure reactor is 100-220 ° C, the reaction time is 4-24 hours, and the reaction pressure is equal to the catalyst at the reaction temperature. The saturated vapor pressure of the precursor.

The increase of reaction temperature is beneficial to the desolvation of the growth element on the crystal surface, surface diffusion, etc., to promote crystal growth and crystal form conversion; reaction time is the kinetic factor of hydrothermal reaction, reflecting the speed of hydrothermal reaction. As the hydrothermal reaction temperature increases and the reaction time prolongs, interactions occur between the crystal grains. Some grain sizes decrease or even disappear, and some grain sizes increase. The macroscopic result is that when the reaction time is constant, the water is hot. The higher the reaction temperature, the larger the grain size, the wider the particle size distribution range, and the longer the reaction temperature, the longer the hydrothermal reaction time increases, the grain size increases, and the particle size distribution range increases. By optimization, the preferred hydrothermal reaction temperature of the present invention is from 100 to 220 ° C and the reaction time is from 4 to 24 hours.

A method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to the present invention, characterized in that, step 3) drying The latter product is calcined at 500-800 ° C for 4-10 hours to form a catalyst. One of the features of the present invention is that a spinel having high temperature stability is obtained as a catalyst carrier by an acid-base pairing-hydrothermal composite method, and the calcination process is an important step to ensure the formation of such a high temperature stable compound. If the calcination temperature is too high, the content of such compounds in the catalyst will be too high, resulting in a decrease in the number of active sites of the catalyst, difficulty in later reduction, and low calcination temperature, which is disadvantageous for the formation of such high-temperature stable compounds. Therefore, the preferred calcination temperature of the present invention is from 500 to 800 °. .

The catalyst prepared by the preparation method of the Ni-Mg/Al ₂ O ₃ catalyst of the invention is suitable for the high temperature and high pressure methylation process of the synthesis gas obtained by coal gasification; the catalyst has good use in the range of 350-650 ° C Catalytic activity and stability.

The present invention provides a simple preparation method for an excellent catalyst for carbon monoxide methylation, and particularly provides an inexpensive, highly efficient, high hydrothermal stability catalyst preparation method for syngas formation.

The preparation method of the Ni-Mg/Al ₂ O ₃ catalyst provided by the invention has the advantages that the preparation process of the catalyst is simple and easy to control, the repeatability is good, the cost is low, and the equipment requirements are low. DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a simplified flow chart showing a process for preparing a Ni-Mg/Al ₂ O ₃ catalyst of the present invention.

Fig. 2 is a graph showing the comparison of the formazanization activity of the catalyst A obtained in Example 1 of the present invention and the catalyst C obtained in Comparative Example 1.

Fig. 3 is a graph showing the comparison of the formazanization activity of the catalyst B obtained in Example 2 of the present invention and the catalyst D obtained in Comparative Example 2.

Figure 4 is a TEM (TEM) of Catalyst B obtained in Example 2 of the present invention.

Fig. 5 is a graph showing the comparison of the methylation activity of the catalysts E, F, G and H obtained in Example 4 of the present invention. Fig. 6 is a graph showing the stable operation performance of the catalyst B obtained in Example 2 of the present invention under high pressure.

Fig. 7 is a graph showing the heat-stable operation performance of the catalyst B obtained in Example 2 of the present invention under high pressure. detailed description

The invention is further described in detail below with reference to the preferred embodiments of the present invention, but it should not be construed that the scope of the present invention is limited to the following examples. In the following examples, the percentage of gas involved is in mole percent.

Example 1 Preparation of Catalyst A

(1) Preparation of solution I: Weigh 3.965 g Μ(Ν0 ₃ ) ₂ ·6Η ₂ 0, 19.295 g Mg(N0 ₃ ) ₂ '6H ₂ 0, 29.846 g Α1(Ν0 ₃ ) ₃ ·9Η ₂ 0, dissolved in 200 mL of deionized water;

(2) Preparation of solution II: Weigh 29.298 g of NaA10 ₂ and dissolve it by adding 200 mL of deionized water;

(3) Solution I reacts with solution II in a countercurrent in the precipitation reactor at a precipitation temperature of 40. C, pH is 8;

(4) The precipitated catalyst precursor is hydrothermally treated and aged in a high pressure reactor at a hydrothermal temperature of 220 ° C for 4 hours;

(5) The precipitate was filtered, washed with deionized water until neutral, and then washed twice with 500 mL; after drying, the sample was calcined at 500 ° C for 4 hours under N ₂ atmosphere to form a catalyst. The obtained catalyst composition was 5% NiO-15% MgO-80% Al ₂ O ₃ , and the calcined catalyst was ground and crushed, and 20-40 mesh powder was taken for activity evaluation.

The activity was evaluated by using a Φ16 mm quartz tube fixed bed reactor with a catalyst loading of 1.5 g and reduction with H ₂ at 500 °C for 4 hours; the raw material gas ratio was H ₂ :CO:N ₂ =3:l:l, The reaction space velocity is 12000 NmL-g- ¹ -!!- ¹ , the operating pressure is normal pressure, and the reaction temperature is 350-650 °C. The results are shown in Fig. 2.

Example 2 Preparation of Catalyst B

(1) Preparation of solution I: Weigh 15.8476 g Μ(Ν0 ₃ ) ₂ ·6Η ₂ 0, 19.2774 g Mg(N0 ₃ ) ₂ '6H ₂ 0, 16.1042 g Α1(Ν0 ₃ ) ₃ ·9Η ₂ 0, add Dissolved in 300 mL of deionized water;

(2) Preparation of solution II: Weigh 26.4228 g of NaA10 ₂ and dissolve it by adding 200 mL of deionized water;

(3) Solution I reacts with solution II in a countercurrent in the precipitation reactor at a precipitation temperature of 90. C, pH is 12;

(5) The precipitate was filtered, washed with deionized water until neutral, and then washed twice with 500 mL; after drying, the sample was placed in a muffle furnace and calcined at 500 ° C for 10 hours to form a catalyst. The obtained catalyst composition was 20% NiO-15% MgO-65% Al ₂ O ₃ , and the calcined catalyst was ground and crushed, and 20-40 mesh powder was taken for activity evaluation.

The activity was evaluated by using a Φ16 mm quartz tube fixed bed reactor with a catalyst loading of 1.5 g and reduction with H ₂ at 500 °C for 4 hours; the raw material gas ratio was H ₂ :CO:N ₂ =3:l:l, The reaction space velocity is 12000 NmL-g- ¹ -!!- ¹ , the operating pressure is normal pressure, and the reaction temperature is 350-650 °C. The results are shown in Fig. 3.

After the powder having a particle diameter of 100 mesh or less was ultrasonically dispersed, the surface analysis of the catalyst B was carried out by a transmission electron microscope of JEM-2100. The results are shown in Fig. 4, wherein the average particle diameter of MO was 15 nm. Stability evaluation of Catalyst B: (1) Under high pressure, a stainless steel fixed bed reactor of Φ12 mm was used, the catalyst loading amount was 1.5 g, and it was reduced by H ₂ at 500 °C for 4 hours; the raw material gas ratio was H ₂ : CO :N ₂ =3:l:l, the reaction space velocity is 780 mL'g-^h- The reaction temperature is 500 °C, the reaction pressure is 2.5 MPa, and the reaction time is 20 hours. The results are shown in Fig. 6. Catalyst B thermal stability evaluation: 012mm stainless steel fixed bed reactor, catalyst loading 1.5g, reduction at 500 °C for 4 hours; raw material gas ratio H ₂ : CO: N ₂ = 3: l: l The reaction space velocity was 780 mL_g- - the catalyst was reacted at 650 ° C for 6 h, and the activity of the catalyst at 350-650 ° C before and after the reaction was compared. The results are shown in Fig. 7.

Comparative Example 1 Preparation of Catalyst C

(1) Preparation of solution I: Weigh 3.965 g Μ(Ν0 ₃ ) ₂ ·6Η20, 19.295 g Mg(N0 ₃ ) ₂ -6H ₂ 0, 29.846 gAl(N0 ₃ )3'9H ₂ 0, add 200 mL Ionic water dissolution;

(3) Solution I and solution II are reacted in a precipitation reactor by coprecipitation, the precipitation temperature is 40 ° C, the pH is 8, and the precipitation is maintained for 4 hours after the end of the precipitation;

(4) The precipitate was filtered, washed with deionized water until neutral, and then washed twice with 500 mL; after drying, the sample was calcined at 500 ° C for 4 hours under N ₂ atmosphere to form a catalyst.

The obtained catalyst composition was 5% NiO-15% MgO-80% Al ₂ O ₃ , and the calcined catalyst was ground and crushed, and a powder of 20-40 mesh was taken for activity evaluation.

The activity was evaluated by using a Φ16 mm quartz tube fixed bed reactor with a catalyst loading of 1.5 g and reduction at 3 °C for 4 hours at 500 °C. The feed gas ratio was H ₂ :CO:N ₂ =3:l:l, the reaction The airspeed is 12000 NmL-g- ¹ -!!- ¹ , the operating pressure is normal pressure, and the reaction temperature is 350-650 °C. The results are shown in Figure 2.

Comparative Example 2 Preparation of Catalyst D

(3) Solution I and solution II are reacted in a precipitation reactor by coprecipitation, the precipitation temperature is 90 ° C, the pH is 12, and the precipitation is maintained for 6 hours after completion;

(4) The precipitate was filtered, washed with deionized water until neutral, and then washed twice with 500 mL; after drying, the sample was placed in a muffle furnace and calcined at 500 ° C for 10 hours to form a catalyst.

The obtained catalyst composition is 20% NiO-15% MgO-65% Al ₂ O ₃ , and the calcined catalyst is ground. Broken, take 20-40 mesh powder for activity evaluation.

The activity was evaluated by a Φ16 mm quartz tube fixed bed reactor with a catalyst loading of 1.5 g and a reduction of 3⁄4 at 500 °C for 4 hours. The feed gas ratio was H ₂ :CO:N ₂ =3:1 : l , the reaction The airspeed is 12000 NmL-g- ¹ -!!- ¹ , the operating pressure is normal pressure, and the reaction temperature is 350-650 °C. The results are shown in Figure 3.

Example 3 Preparation of Catalysts E, F, G, H

(1) Preparation of solution I: Weigh 23.771 g Ni(N0 ₃ ) ₂ -6H ₂ 0, 12.852 g Mg(N0 ₃ ) ₂ '6H ₂ 0, 11.149 g Al(N0 ₃ ) ₃ -9H ₂ 0, add Dissolved in 200 mL of deionized water;

(2) Preparation of solution II: Weigh 25.610 g of NaA10 ₂ and dissolve it by adding 200 mL of deionized water;

(3) Solution I reacts with solution II in a countercurrent collision in a precipitation reactor at a precipitation temperature of 40 Å. C, pH is 10;

(4) The precipitated catalyst precursor is hydrothermally treated and aged in a high pressure reactor at a hydrothermal temperature of 100 ° C for 24 hours;

(5) Filter the precipitate, wash it with deionized water until neutral, and then wash it twice with 500 mL; after drying, the sample is divided into four parts and placed in a muffle furnace, and calcined at 500, 600, 700, 800 °C. The catalyst is formed in an hour. The obtained catalyst composition was 30% NiO-10% MgO-60% Al ₂ O ₃ , and the calcined catalyst was ground and crushed, and 20-40 mesh powder was taken for activity evaluation.

The activity was evaluated by using a Φ16 mm quartz tube fixed bed reactor with a catalyst loading of 1.5 g and reduction with H ₂ at 500 °C for 4 hours; the raw material gas ratio was H ₂ : CO: N ₂ = 3: l : l , The reaction space velocity is 12000 NmL-g- ¹ -!!- ¹ , the operating pressure is normal pressure, and the reaction temperature is 450-650 °C. The results are shown in Fig. 5.

Example Experimental results show:

As can be seen from Fig. 2 and Fig. 3, the present invention adopts a Ni-Mg/Al ₂ O ₃ catalyst prepared by an acid-base pairing-hydrothermal composite method (Examples 1, 2), whether it is a high active component content or a low activity. The component content and the catalyst all showed higher methylation activity than the coprecipitation method (Comparative Examples 1, 2).

It can be seen from Fig. 5 that the Ni-Mg/Al ₂ O ₃ catalyst prepared by the acid-base pairing-hydrothermal composite method of the invention can maintain a high A at the calcination temperature of 500, 600, 700, 800 °C. The deuteration activity, while at the experimental temperature range, the calcination catalyst at 500 °C showed high CH ₄ selectivity, close to the thermodynamic equilibrium under the experimental conditions.

It can be seen from Fig. 6 that the Ni-Mg/Al ₂ O ₃ catalyst prepared by the acid-base pairing-hydrothermal composite method can maintain a certain activity under the reaction conditions, has good stability, and is close to the experimental conditions. Balance the data.

It can be seen from Fig. 7 that the present invention adopts the acid-base pairing-hydrothermal composite method to obtain Ni-Mg/Al ₂ 0 _{3 .} The thermal stability of the catalyst is good.

The results of the above related experiments show that the catalyst prepared by the acid-base pairing-hydrothermal composite method provided by the invention has the advantages of good catalytic activity and high stability, and is a kind of synthetic gas with low cost and practical application prospect. Deuteration catalyst.

Claims

Rights request

A method for preparing a Ni-Mg/Al ₂ O ₃ catalyst, the method comprising the steps of:

3) The catalyst slurry obtained in the step 2) is washed, filtered, dried and calcined to form a catalyst.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to claim 1, wherein the reaction temperature of the step 1) is 40-90 ° C, and the two solutions are subjected to a precipitation reaction by a counter-impact.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to claim 1, wherein the reaction temperature of the autoclave in step 2) is 100-220 ° C, and the reaction time is 4-24 hours. The pressure is the saturated vapor pressure of the catalyst precursor at the reaction temperature.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to claim 1, wherein the step 3) is calcined at a temperature of 500 to 800 ° C and the calcination time is 4 to 10 hours.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to claim 1, wherein the acidic solution I is a nitrate, oxalate, carbonate and carbon of nickel, magnesium or aluminum. A nitrate solution formed by dissolving the acid salt in nitric acid.

The method for preparing a Ni-Mg/Al ₂ O ₃ catalyst according to claim 1, wherein the alkaline solution is a NaA10 ₂ solution.