CN110586064B - Lithium-doped zirconium oxide loaded indium oxide catalyst and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of supported oxide catalysts, and discloses a lithium-doped zirconia supported indium oxide catalyst, a preparation method and application thereof, wherein the catalyst is prepared by bulk phase doping of zirconia by lithium atoms through a coprecipitation method to obtain a carrier, and indium oxide particles are uniformly loaded on a lithium-doped monoclinic zirconia carrier; during preparation, firstly, adding lithium and zirconium precursors by a coprecipitation method, and precipitating, drying and roasting to obtain a lithium-doped monoclinic zirconia carrier; and then loading indium oxide on the carrier by a wet impregnation method, and drying and roasting again to obtain the final catalyst. The catalyst prepared by the invention is suitable for the reaction of preparing methanol by hydrogenating carbon dioxide, the lithium-doped zirconium oxide is used as a carrier, and the indium oxide is used as an active component, so that the conversion rate of carbon dioxide of more than 10 percent and the selectivity of methanol of about 90 percent are realized, and the catalyst has the characteristics of simple structure, convenient preparation and low operation pressure, and simultaneously, the series of catalysts also keep long-term stability.

Description

A lithium-doped zirconia-supported indium oxide catalyst and its preparation method and application

technical field

The invention belongs to the technical field of supported oxide catalysts, and specifically relates to a lithium-doped zirconia-supported indium oxide catalyst and a preparation method thereof, and the application of the catalyst to efficiently generate methanol in carbon dioxide hydrogenation.

Background technique

At present, a large amount of carbon dioxide emitted by industrial production has caused a serious global greenhouse effect, which has destroyed the earth's environment and the sustainable development of human beings. Therefore, research on carbon dioxide emission reduction and conversion utilization technologies has become an urgent problem to be solved. The carbon dioxide hydrogenation technology developed by using solar photolysis of water to produce hydrogen is not only conducive to reducing the concentration of carbon dioxide in the atmosphere, but also can generate high-efficiency fuels such as carbon monoxide, methane, methanol, dimethyl ether, ethanol, and hydrocarbons, which are convenient for storage and storage. transportation. Among them, the generation of methanol is relatively easy in terms of thermodynamics and kinetics, and methanol is the raw material for the preparation of gasoline and diesel oil and C ₂ -C ₄ higher olefins through methanol to olefins, and is also an important factor for the preparation of many fine chemicals such as medicines, cosmetics, and polyesters. Raw materials; in addition, methanol is a clean and efficient high-calorie fuel that can be used as a gasoline additive, so the catalytic conversion of carbon dioxide into methanol products has received more attention.

Due to the stable chemical properties of _CO2 and difficult activation, the conversion rate of this reaction is generally low, and the formation of methanol is an exothermic reaction. Thermodynamically, low temperature is beneficial to the production of methanol but not conducive to the activation of carbon dioxide. Therefore, it is necessary to select an appropriate reaction temperature. And design efficient catalysts; on the other hand, carbon monoxide and methanol are two accompanying products in the hydrogenation reaction of carbon dioxide, both have similar intermediates, and the reaction occurs on the same catalytic site, resulting in the two The selectivity is not high; therefore, how to design an efficient catalyst for kinetic control to promote _CO2 activation conversion and adjust product selectivity, so as to obtain methanol efficiently is an urgent problem to be solved.

At present, the widely researched catalyst for methanol synthesis is copper-zinc-aluminum catalyst, which has a high conversion rate of carbon dioxide, but the selectivity of methanol is only about 60%, and the subsequent separation steps are costly; in addition, metal copper is easy to The sintering deactivation reduces the reaction stability. The oxide catalyst represented by indium oxide can achieve 90% methanol selectivity, which can reduce the cost of the subsequent separation process. At the same time, the oxide has a stable high-temperature structure and is not easy to deactivate, so it has attracted more and more attention. According to reports, there are several regulatory pathways to enhance methanol yield in _CO2 hydrogenation that are generally accepted as follows. One is to adjust the particle size of the oxide particles on the supported oxide catalyst; the other is to adjust the electronic properties and adsorption properties of carbon dioxide at the interface between the active oxide and the support by changing the type of support, so as to achieve the purpose of changing the product distribution. The above two methods, due to the complex structure of the catalyst and the unclear reaction site, make the preparation method complex and difficult to repeat, and are also susceptible to environmental factors. Indium oxide-based catalysts are widely used in carbon dioxide hydrogenation reactions. How to further improve the catalyst so that it has stronger _CO2 activation ability and longer time stability, especially higher methanol selectivity is the research focus of _CO2 hydrogenation.

Contents of the invention

The present invention aims to solve the technical problems of poor selectivity (<60%) of single products such as methanol and poor catalytic stability of traditional copper-based catalysts in the hydrogenation reaction of carbon dioxide, and provides a lithium-doped zirconia-supported indium oxide Catalyst and its preparation method, and its application in carbon dioxide hydrogenation. By doping lithium element into the zirconia support, monoclinic zirconia with single pure phase is obtained, and then indium oxide is supported on the monoclinic zirconia On the carrier, the carbon dioxide conversion rate of more than 10% and the selectivity of methanol of about 90% are realized, and the catalyst can realize the stability of more than 20h at the same time.

In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

A lithium-doped zirconia-supported indium oxide catalyst, comprising lithium-doped monoclinic zirconia (xLi-ZrO ₂ ), the lithium-doped monoclinic zirconia (xLi-ZrO ₂ ) is prepared by co-precipitation method It is prepared by doping zirconia with lithium atoms in a bulk phase, and the molar doping amount of lithium ions in the lithium-doped monoclinic zirconia is x=5-10%; the lithium-doped monoclinic zirconia is uniformly Indium oxide particles are loaded, and the mass percentage of the indium oxide to the lithium-doped monoclinic zirconia is 6-10%.

Further, the lithium-doped monoclinic zirconia is a carrier, and the indium oxide is a catalytically active component.

Further, the particle size range of the lithium-doped monoclinic zirconia is 50-100 nanometers.

Further, the particle size range of the indium oxide particles is 8-15 nanometers.

A preparation method of the lithium-doped zirconia-supported indium oxide catalyst, the method is carried out according to the following steps:

(1) Zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and lithium nitrate (LiNO ₃ ) are dissolved in deionized water in proportion according to the value of x to form a mixed solution with a concentration of 0.2-1M/L. The mixed solution is heated to 50-90°C;

(2) Stir the mixed solution obtained in step (1) continuously, and add concentrated ammonia water (NH ₃ ·H ₂ O, mass concentration 22-25%) dropwise to the mixed solution until the pH value of the mixed solution reaches 8-10 ;

(3) After aging the mixed solution obtained in step (2) at 50-90°C for 1-3h, centrifuge the obtained suspension, wash it, and dry it in vacuum; then roast it at 300-500°C for 2-6h to obtain xLi _-ZrO2 carrier, x=5-10%, wherein x represents the molar doping amount of lithium ions in lithium-doped monoclinic zirconia;

(4) Dissolve indium nitrate hydrate (In(NO ₃ ) ₃ ·H ₂ O) in deionized water to form a solution with a concentration of 0.4-1M/L, and add the solution dropwise onto the prepared xLi-ZrO ₂ carrier , to ensure that the mass fraction of supported indium oxide is 6-10%; after ultrasonic treatment, drying, and then calcination at 300-500°C for 4-6h, to obtain In ₂ O ₃ /xLi-ZrO ₂ catalyst, x=5-10 %.

Further, the speed of dripping concentrated ammonia water in step (2) is 20-50 drops/minute.

Further, the vacuum drying temperature in step (3) is 80-100°C, and the time is 8-12h.

Further, in step (4), the ultrasonic treatment time is 1-3 h, the vacuum drying temperature is 80-100° C., and the time is 8-12 h.

An application of the lithium-doped zirconia-supported indium oxide catalyst is used for hydrogenation of carbon dioxide to prepare methanol.

Further, follow the steps below:

(1) performing tableting and granulation treatment on the lithium-doped zirconia-supported indium oxide catalyst;

(2) The granular catalyst prepared above is subjected to a high-pressure continuous reaction in a reaction gas at a reaction temperature of 250-350° C.

The beneficial effects of the present invention are:

The present invention takes indium oxide-supported zirconia as the main component, and can prepare a series of zirconia-supported indium oxide-based catalysts of different crystal forms by changing the doping amount of lithium element (Li).

On the one hand, a small amount of Li-doped zirconia carrier ZrO ₂ (Li:Zr=5:95-10:90) presents a granular structure, and zirconia is mainly monoclinic; the monoclinic zirconia and indium oxide There is a strong electronic interaction between the two, that is, zirconium oxide can transfer electrons to indium oxide, and electron-rich indium oxide is conducive to the activation of carbon dioxide and the carbon-oxygen bond break. Therefore, the catalyst obtained by supporting indium oxide on monoclinic zirconia, such as In ₂ O ₃ /5Li-ZrO ₂ , has a good effect on carbon dioxide hydrogenation reaction, the conversion rate of carbon dioxide is higher than 10%, and the selectivity of methanol It reaches 88%, and has good stability.

On the other hand, after studying the structure and catalytic performance of the catalyst outside the optimal Li doping range, it was also found that the zirconia support ZrO ₂ without Li doping and excess Li (Li:Zr>20:80) doped Miscellaneous zirconia supports, such as: 40Li-ZrO ₂ (Li:Zr=40:60), although it also presents a granular structure, its crystal structure is mainly tetragonal, and the energy band between tetragonal zirconia and indium oxide The structure does not match, so there is no electronic interaction, so the In ₂ O ₃ /ZrO ₂ and In ₂ O ₃ /40Li-ZrO ₂ catalysts obtained after the carrier is loaded with indium oxide can only hydrogenate carbon dioxide under low pressure conditions. It has a general effect, specifically, the methanol selectivity is only about 60%, which is far lower than that of the indium oxide catalyst supported by monoclinic zirconia, which further proves that the monoclinic zirconia support is the key to the improvement of methanol selectivity.

It can be seen that with the addition of Li, the crystal form of zirconia transforms from tetragonal to monoclinic, but when the Li doping amount is too much, the crystal form of zirconia transforms into tetragonal again. Indium oxide catalysts supported by different crystal forms of zirconia have different catalytic performances in the hydrogenation reaction of carbon dioxide due to the different interactions between oxides. Among them, whether it is carbon dioxide conversion rate or methanol selectivity, monoclinic zirconia-supported Indium oxide is significantly stronger than tetragonal zirconia-supported indium oxide. During the hydrogenation reaction of carbon dioxide, the methanol yield and the proportion of monoclinic zirconia in the catalyst support show a positive correlation, indicating that the monoclinic zirconia The interaction between zirconia and indium oxide does promote the activation of carbon dioxide during the reaction and favors the formation of methanol. At the same time, because the amount of indium oxide is small, the toxicity is small, and carbon dioxide can be hydrogenated to produce methanol through a simple method under relatively low pressure, it has certain industrial significance.

Description of drawings

Figure 1 is a graph showing the product distribution and carbon dioxide conversion rate versus time for the In ₂ O ₃ /5Li-ZrO ₂ catalyst prepared in Example 1 to catalyze carbon dioxide hydrogenation (280°C, 30bar, space velocity=3h ^-1 , CO ₂ / N ₂ /H ₂ =1/1/3);

Figure 2 is a diagram showing the change of methanol selectivity and carbon dioxide conversion rate with the reaction temperature when the indium oxide-based catalysts prepared in Examples 1, 26, 29, and 30 catalyze the hydrogenation of carbon dioxide (225-350 ° C, 30 bar, space velocity = 3h ^{- 1} , CO ₂ /N ₂ /H ₂ =1/1/3);

Fig. 3 is a diagram showing the variation of methanol yield with reaction temperature when indium oxide-based catalysts prepared in Examples 1, 26, 29, and 30 catalyze carbon dioxide hydrogenation (225-350°C, 30bar, space velocity=3h ^-1 , CO ₂ /N ₂ /H ₂ =1/1/3);

Fig. 4 is the X-ray diffraction pattern of the indium oxide-based catalyst prepared by embodiment 1, 26, 29, 30;

Fig. 5 is the surface Raman spectrum of the indium oxide-based catalysts prepared in Examples 1, 26, 29, and 30.

Detailed ways

The present invention will be described in further detail below through specific examples. The following examples can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

Example 1

(1) Take 3.0g zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and 0.03g lithium nitrate (LiNO ₃ ) and add them to 50ml deionized water (the molar doping amount of lithium is 5%), the formed solution The concentration is 0.2M/L, the above solution is heated to 80°C, and left to stir;

(2) Add concentrated ammonia water (NH ₃ ·H ₂ O, concentration 22-25%) to the mixed solution of zirconium oxychloride and lithium nitrate in (1) drop by drop at a rate of 20 drops/min, and keep stirring Down until the pH value of the mixed solution reaches 9, stop dripping;

(3) Stand for aging reaction at 80°C for 2 hours, centrifuge the obtained suspension and wash it four times with deionized water; dry the obtained solid in an oven at 80°C for 12 hours; dry the obtained solid in air at 300°C Calcined for 4h to obtain 5Li-ZrO ₂ zirconia carrier.

(4) Dissolve 0.21g of indium nitrate hydrate (In(NO ₃ ) ₃ ·H ₂ O) in deionized water to form a solution with a concentration of 0.7M/L, and add the solution dropwise to 1g of (3) to obtain 5Li-ZrO ₂ zirconia carrier (the mass fraction of loaded indium oxide is 8%), after 2h ultrasonic treatment.

(5) The solid obtained in (4) was dried in a vacuum oven at 80°C for 12h, and then calcined in air at 300°C for 4h to obtain a series of In ₂ O ₃ /5Li-ZrO ₂ catalysts.

(6) compressing the above-mentioned powder catalyst into 20-40 purpose granular catalysts;

(7) Put 0.2g of the catalyst after tableting into the fixed-bed reactor, feed N ₂ , press to 30bar, and switch to reaction gas when the reaction temperature reaches 280°C, wherein the molar ratio of carbon dioxide and hydrogen is 3:1, The balance gas is nitrogen (CO ₂ =10ml/min, H ₂ =30mL/min, N ₂ =10mL/min), and the reaction space velocity based on carbon dioxide is 3h ^-1 .

Catalyst activity is represented by produced methanol (mL/min) and selectivity, and the product selectivity is calculated by the following formula:

Conversion rate:

Optional:

Among them, F _CO2,in represents the volume flow rate of carbon dioxide at the reactor inlet, F _CO2,out represents the gas volume flow rate of carbon dioxide at the reactor outlet, i represents the reaction products, including CH ₄ and CO, and n represents the carbon dioxide contained in these substances carbon number.

The reaction product was analyzed online by gas chromatography, and the relationship between product rate and selectivity and time is shown in Table 1 and accompanying drawing 1.

Table 1, the product selectivity of different reaction times

It can be seen from Table 1 and Figure 1 that the In ₂ O ₃ /5Li-ZrO ₂ catalyst has high activity and good stability, and the reaction data basically does not change after 5 hours of reaction.

Example 2:

Adopt the method for embodiment 1 to react, and its difference is only that the concentration of the mixed solution in step (1) is 0.5M/L.

Example 3:

Adopt the method for embodiment 1 to react, and its difference is only that the concentration of the mixed solution in step (1) is 1M/L.

Example 4:

The method of Example 1 was adopted for the reaction, the only difference being that the heating temperature of the mixed solution in step (1) and the aging temperature in step (3) were 50° C.

Example 5:

The method of Example 1 was adopted for the reaction, the only difference being that the heating temperature of the mixed solution in step (1) and the aging temperature in step (3) were 90° C.

Embodiment 6:

Adopt the method for embodiment 1 to react, and its difference is only that step (2) mixed solution pH value finally reaches 8.

Embodiment 7:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the pH value of step (2) mixed solution finally reaches 10.

Embodiment 8:

Adopt the method for embodiment 1 to react, and its difference is only that the aging time of mixed solution in step (3)) is 1h.

Embodiment 9:

The method of Example 1 was adopted to react, the only difference being that the aging time of the mixed solution in step (3) was 3h.

Example 10:

Adopt the method for embodiment 1 to react, and its difference is only that the drip rate of the strong ammoniacal liquor of step (2) is 30 drops/min.

Example 11:

Adopt the method for embodiment 1 to react, and its difference is only that the rate of addition of the strong ammoniacal liquor of step (2) is 50 drops/min.

Example 12:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that step (3) and step (5) drying temperature are 90 ℃.

Example 13:

Adopt the method for embodiment 1 to carry out reaction, and its difference is that step (3) and step (5) drying temperature are all 100 ℃.

Example 14:

Adopt the method for embodiment 1 to react, and its difference is only that the drying time of step (3) and step (5) is 8h.

Example 15:

Adopt the method for embodiment 1 to react, and its difference is only that step (3) and step (5) drying time are 10h.

Example 16:

Adopt the method for embodiment 1 to react, and its difference is only that the roasting temperature of step (3) and step (5) is 400 ℃.

Example 17:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the roasting temperature of step (3) and step (5) is 500 ℃.

Example 18:

Adopt the method for embodiment 1 to react, and its difference is only that the roasting time of step (3) is 2h.

Example 19:

Adopt the method for embodiment 1 to react, and its difference is only that the roasting time of step (3) is 6h.

Example 20:

Adopt the method for embodiment 1 to react, and its difference is only that the concentration of the indium nitrate solution of step (4) is 0.4M/L.

Example 21:

Adopt the method for embodiment 1 to react, and its difference is only that the concentration of the indium nitrate solution of step (4) is 1M/L.

Example 22:

The reaction was carried out using the method of Example 1, the only difference being that the mass of indium nitrate (In(NO ₃ ) ₃ ·H ₂ O) used in step (4) was 0.16 g, and the mass fraction of supported indium oxide was 6%.

Example 23:

The reaction was carried out using the method of Example 1, the only difference being that the mass of indium nitrate (In(NO ₃ ) ₃ ·H ₂ O) used in step (4) was 0.26 g, and the mass fraction of supported indium oxide was 10%.

Example 24:

Adopt the method of embodiment 1 to react, and its difference is only that the ultrasonic time of step (4) is 1h.

Example 25:

Adopt the method of embodiment 1 to react, and its difference is only that the ultrasonic time of step (4) is 3h.

Example 26:

The method of Example 1 was used for the reaction, the only difference being that in step (1), only 3.2 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) was dissolved in 50 ml of deionized water.

Example 27:

Adopt the method for embodiment 1 to react, its difference is only to get 2.9g zirconium oxychloride (ZrOCl ₂ 8H ₂ O) and 0.04g lithium nitrate (LiNO ₃ ) of step (1) and join in 50ml deionized water (lithium's Molar doping is 7.5%).

Example 28:

Adopt the method for embodiment 1 to react, its difference is only to get 2.8g zirconium oxychloride (ZrOCl ₂ 8H ₂ O) and 0.06g lithium nitrate (LiNO ₃ ) in step (1) and join in 50ml deionized water (lithium's Molar doping is 10%).

Example 29:

Adopt the method for embodiment 1 to react, its difference is only to get 2.5g zirconium oxychloride (ZrOCl ₂ 8H ₂ O) and 0.12g lithium nitrate (LiNO ₃ ) of step (1) and join in 50ml deionized water (lithium's Molar doping is 20%).

Example 30:

Adopt the method for embodiment 1 to react, its difference is only to get 1.9g zirconium oxychloride (ZrOCl ₂ 8H ₂ O) and 0.24g lithium nitrate (LiNO ₃ ) in step (1) and join in 50ml deionized water (lithium's Molar doping is 40%).

Example 31:

Adopt the method for embodiment 1 to react, and its difference is only that the roasting time of step (5) is 5h.

Example 32:

Adopt embodiment 1 method to react, its difference is only that the roasting time of step (5) is 6h.

Example 33:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the reaction temperature of step (7) is 225 ℃.

Example 34:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the reaction temperature of step (7) is 250 ℃.

Example 35:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the reaction temperature of step (7) is 300 ℃.

Example 36:

Adopt the method for embodiment 1 to carry out reaction, and its difference is only that the reaction temperature of step (7) is 350 ℃.

Example 37:

The reaction was carried out using the method of Example 26, the difference being that the reaction temperature in step (7) was 225°C.

Example 38:

The reaction was carried out using the method of Example 26, the difference being that the reaction temperature in step (7) was 250°C.

Example 39:

The reaction was carried out using the method of Example 26, the difference being that the reaction temperature in step (7) was 300°C.

Example 40:

The reaction was carried out using the method of Example 26, the difference being that the reaction temperature in step (7) was 350°C.

Example 41:

The reaction was carried out using the method of Example 29, the difference being that the reaction temperature in step (7) was 225°C.

Example 42:

The reaction was carried out using the method of Example 29, the difference being that the reaction temperature in step (7) was 250°C.

Example 43:

The reaction was carried out using the method of Example 29, the difference being that the reaction temperature in step (7) was 300°C.

Example 44:

The reaction was carried out using the method of Example 29, the difference being that the reaction temperature in step (7) was 350°C.

Example 45:

The reaction was carried out using the method of Example 30, the difference being that the reaction temperature in step (7) was 225°C.

Example 46:

The reaction was carried out using the method of Example 30, the difference being that the reaction temperature in step (7) was 250°C.

Example 47:

The reaction was carried out using the method of Example 30, the difference being that the reaction temperature in step (7) was 300°C.

Example 48:

The reaction was carried out using the method of Example 30, the difference being that the reaction temperature in step (7) was 350°C.

Example 49:

The reaction was carried out using the method of Example 1, the only difference being that the volume space velocity of carbon dioxide in step (7) was 1h ^-1 .

Example 50:

The reaction was carried out using the method of Example 1, the only difference being that the volume space velocity of carbon dioxide in step (7) was 5h ^-1 .

Example 51:

The reaction was carried out using the method of Example 1, the only difference being that the volume space velocity of carbon dioxide in step (7) was 10h ^-1 .

Example 52:

Adopt the method for embodiment 1 to react, its difference is only, get 3.2g zirconium oxychloride (ZrOCl _{8H 2} O) of step (1) and join 50ml deionized water, the carbon dioxide volume space velocity of step (7) is 1h ^-1 .

Example 53:

Adopt the method for embodiment 1 to react, its difference is only, get 3.2g zirconium oxychloride (ZrOCl _{8H 2} O) of step (1) and join 50ml deionized water, the carbon dioxide volume space velocity of step (7) is 5h ^-1 .

Example 54:

Adopt the method for embodiment 1 to react, its difference is only, get 3.2g zirconium oxychloride (ZrOCl _{8H 2} O) of step (1) and join 50ml deionized water, the carbon dioxide volume space velocity of step (7) is 10h ^-1 .

Example 55:

Adopt the method for embodiment 1 to react, and its difference is, get 1.9g zirconium oxychloride (ZrOCl _{8H 2} O) and 0.24g lithium nitrate (LiNO ) of step (1) and join _50ml deionized water, step ( 7) The volumetric space velocity of carbon dioxide is 1h ^-1 .

Example 56:

Adopt the method for embodiment 1 to react, and its difference is, get 1.9g zirconium oxychloride (ZrOCl _{8H 2} O) and _0.24g lithium nitrate (LiNO ) of step (1) and join 50ml deionized water, step ( 7) The volumetric space velocity of carbon dioxide is 5h ^-1 .

Example 57:

Adopt the method for embodiment 1 to react, and its difference is, get 1.9g zirconium oxychloride (ZrOCl _{8H 2} O) and _0.24g lithium nitrate (LiNO ) of step (1) and join 50ml deionized water, step ( 7) The volumetric space velocity of carbon dioxide is 10h ^-1 .

Regarding the results and data of the above examples, the activity data during the reaction for 4 hours were used for comparison to investigate the influence of different parameters on the reaction performance of the catalyst. Except for the conditions specified below, our catalyst can be prepared by changing the above conditions, and the performance in carbon dioxide hydrogenation reaction is similar.

(1) The influence of the molar doping amount of lithium on the catalyst reactivity, see Table 2. Reaction condition is the same as embodiment 1,26,27,28,29,30.

Table 2. Effect of different Li doping amounts on carbon dioxide hydrogenation activity

Li:Zr CO₂ conversion rate (%) Methanol selectivity (%) 0 5.2 72 5:95 12 88 7.5:92.5 12 88 10:90 11 86 20:80 8.5 77.4 40:60 6.3 61.6

It can be seen from Table 2 that when the molar doping amount x of lithium ions is 5-10%, the series of lithium-doped zirconia-supported indium oxide catalysts all show good carbon dioxide hydrogenation activity and methanol selectivity. property, that is, the molar doping amount of lithium ions x=5-10% is the optimal doping amount.

(2) The influence of the molar doping amount of lithium on the catalyst reactivity and the crystal form of zirconia, see the accompanying drawings 2, 3, 4, and 5 of the table. Reaction condition is the same as embodiment 1,26,29,30.

It can be seen from Fig. 2 and Fig. 3 that in the range of 225-350°C in the hydrogenation reaction temperature of carbon dioxide, with the increase of the molar doping amount of Li (5-40%), the conversion of carbon dioxide and the selectivity of methanol have a significant difference. The yield of methanol decreases gradually while the selectivity of carbon monoxide gradually increases; at the optimum reaction temperature of 280℃, the selectivity of methanol decreases from 86% of In ₂ O ₃ /5Li-ZrO ₂ to In ₂ O ₃ /40Li -61% of ZrO ₂ , the carbon monoxide selectivity increased from 12% of In ₂ O ₃ /5Li-ZrO ₂ to 39% of In ₂ O ₃ /40Li-ZrO ₂ . The reaction performance of all samples can be maintained for at least 5 hours without decreasing, indicating that the catalyst has good stability.

It is worth noting that the zirconia without Li doping is still in the tetragonal crystal form, and the conversion rate of carbon dioxide and methanol selectivity are not high; a small amount of Li doping (molar doping amount 5-10%) can make the zirconia crystal form Turning to the monoclinic crystal form, the catalytic performance (methanol selectivity) is significantly improved. As shown in FIG. 4 , when the molar doping amount of lithium in the zirconia carrier is 5%, the lithium-doped zirconia bulk phase completely exhibits a monoclinic crystal form. As shown in Fig. 5, when the molar doping amount of lithium in the zirconia carrier is 5%, the surface of the lithium-doped zirconia completely exhibits monoclinic crystal. It can be seen that as the Li doping amount continues to increase (the molar doping amount is 10-40%), the bulk phase crystal form of zirconia presents a transition from monoclinic to tetragonal, and at the same time, the surface crystal form also presents a the same trend of change.

(3) The influence of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /5Li-ZrO ₂ , see Table 3. Reaction condition is the same as embodiment 1,33,34,35,36.

Table 3. Effect of reaction temperature on carbon dioxide hydrogenation activity

Reaction temperature (°C) CO₂ conversion rate (%) Methanol selectivity (%) 225 4 99.3 250 5 95 280 12 86 300 16 46.8 350 26 19.2

It can be seen from Table 3 that as the reaction temperature increases, the conversion rate of carbon dioxide hydrogenation increases significantly, that is, the reaction activity gradually increases; for In ₂ O ₃ /5Li-ZrO ₂ The change is very sensitive. As the reaction temperature increases, the methanol selectivity gradually decreases, while the carbon monoxide selectivity gradually increases; see accompanying drawing 3, when the reaction temperature is 280°C, the methanol yield reaches the maximum.

(4) The influence of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /ZrO ₂ , see Table 4. Reaction condition is the same as embodiment 26,37,38,39,40.

Table 4. Effect of reaction temperature on carbon dioxide hydrogenation activity

Reaction temperature (°C) CO₂ conversion rate (%) Methanol selectivity (%) 225 2 100 250 3.7 83 280 5.2 72 300 10.9 34 350 twenty two 3

It can be seen from Table 4 that as the reaction temperature increases, the conversion rate of carbon dioxide hydrogenation increases significantly, that is, the reaction activity gradually increases; for the In ₂ O ₃ /ZrO ₂ catalyst, the product selectivity changes very much with the reaction temperature Sensitive, as the reaction temperature increases, the methanol selectivity gradually decreases, while the carbon monoxide selectivity gradually increases. When the reaction temperature is 280 ° C, the methanol yield reaches the maximum, but there is still a certain amount of carbon monoxide produced at this time; At any reaction temperature, the methane selectivity of In ₂ O ₃ /ZrO ₂ is lower than that of In ₂ O ₃ /5Li-ZrO ₂ .

(5) The influence of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /20Li-ZrO ₂ , see Table 5. The reaction conditions are the same as in Examples 29, 41, 42, 43, and 44.

Table 5. Effect of reaction temperature on carbon dioxide hydrogenation activity

Reaction temperature (°C) CO₂ conversion rate (%) Methanol selectivity (%) 225 3.8 100 250 4.6 87.9 280 8.1 77.4 300 12.1 42 350 25 12

It can be seen from Table 5 that as the reaction temperature rises, the conversion rate of carbon dioxide hydrogenation increases obviously, that is, the reaction activity gradually increases; for In ₂ O ₃ /20Li-ZrO ₂ High, the methanol selectivity gradually decreases, while the carbon monoxide selectivity gradually increases; see Figure 3, when the reaction temperature is 280 ° C, the methanol yield reaches the maximum, at any reaction temperature, In ₂ O ₃ /20Li- The methane selectivity of ZrO ₂ is lower than that of In ₂ O ₃ /5Li-ZrO ₂ .

(6) The influence of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /40Li-ZrO ₂ , see Table 6. Reaction condition is the same as embodiment 30,45,46,47,48.

Table 6. Effect of reaction temperature on carbon dioxide hydrogenation activity

Reaction temperature (°C) CO₂ conversion rate (%) Methanol selectivity (%) 225 2.3 92 250 3.4 80.4 280 6.3 61.6 300 10.9 30.8 350 22.9 6

It can be seen from the table that as the reaction temperature increases, the conversion rate of carbon dioxide hydrogenation increases obviously, that is, the reaction activity gradually increases; for the In ₂ O ₃ /40Li-ZrO ₂ catalyst, as the reaction temperature , the selectivity of methanol gradually decreases, while the selectivity of carbon monoxide gradually increases; see Figure 3, when the reaction temperature is 280°C, the yield of methanol reaches the maximum value, at any reaction temperature, In ₂ O ₃ /40Li-ZrO The methane selectivity of ₂ is lower than that of In ₂ O ₃ /5Li-ZrO ₂ .

As shown in Figure 2, the conversion rate of the three samples is consistent with the trend of the product distribution as the reaction temperature changes, but the difference in product selectivity between them is very obvious, and this difference generally exists with the temperature change and does not change.

(7) The influence of carbon dioxide volume space velocity on the catalytic activity of the catalyst, see Table 7. Reaction condition is the same as embodiment 1,49-57.

Table 7. Effect of carbon dioxide volume space velocity on catalytic activity

It can be seen from the table that with the increase of the volume space velocity of carbon dioxide, the conversion rate of carbon dioxide decreases continuously, but the selectivity of methane and carbon monoxide remains basically unchanged, and the space velocity 1h ^-1 and 3h ^-1 have little difference, so the best The volumetric space velocity of carbon dioxide is 3h ^-1 .

(8) The influence of the calcining temperature in the step (3) and the step (5) on the catalytic activity of the catalyst. Reaction condition is the same as embodiment 1,16,17.

When the calcination temperature is 300-400℃, the catalytic performance of In ₂ O ₃ /5Li-ZrO ₂ remains unchanged, and its crystal form is still monoclinic, but when the calcination temperature is >400℃, 5Li-ZrO ₂ oxidizes The monoclinic crystal structure of the zirconium support will be destroyed, and the carbon dioxide conversion rate and methanol selectivity of the corresponding catalyst In ₂ O ₃ /5Li-ZrO ₂ will also drop sharply.

(9) The influence of other factors on the catalytic activity of the catalyst.

Tests have proved that under the experimental conditions, that is, the concentration of the mixed solution of zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and lithium nitrate (LiNO ₃ ) is 0.2-1M/L, the heating temperature and aging temperature of the mixed solution Keep it at 50-100°C, add concentrated ammonia water dropwise until the pH value of the mixed solution is in the range of 8-10; aging time 1-3h, roasting time 2-6h, the xLi- _ZrO2 carrier obtained is in crystal form, particle size, There is no obvious difference in surface structure and other aspects;

In addition, the solution concentration (0.4-1M/L) of different hydrated indium nitrate (In(NO ₃ ) ₃ ·H ₂ O), the mass fraction of loaded indium oxide (6-10%); the time of ultrasonic treatment (1- 3h), the drying temperature and time have no obvious effect on the structure and catalytic performance of the obtained In ₂ O ₃ /xLi-ZrO ₂ catalyst.

Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are only illustrative and not restrictive. Those of ordinary skill in the art Under the enlightenment of the present invention, without departing from the purpose of the present invention and the scope of protection of the claims, personnel can also make specific changes in many forms, and these all belong to the protection scope of the present invention.

Claims (8)

1. A lithium-doped zirconia-supported indium oxide catalyst, characterized in that, it is used for the hydrogenation of carbon dioxide to prepare methanol; it comprises lithium-doped monoclinic zirconia, and the lithium-doped monoclinic zirconia is obtained by co-precipitation It is prepared by doping zirconia with lithium atoms in a bulk phase, and the molar doping amount of lithium ions in the lithium-doped monoclinic zirconia is x=5-10%; the lithium-doped monoclinic zirconia Indium oxide particles are evenly loaded on the surface, and the mass percentage of the indium oxide in the lithium-doped monoclinic zirconia is 6-10%; The particle size range of the lithium-doped monoclinic zirconia is 50-100 nanometers; the particle size range of the indium oxide particles is 8-15 nanometers; and obtained according to the following method: (1) dissolving zirconium oxychloride octahydrate and lithium nitrate in deionized water in proportion according to the value of x to form a mixed solution with a concentration of 0.2-1M/L, and heating the mixed solution to 50-90°C; (2) constantly stirring the mixed solution obtained in step (1), and adding concentrated ammonia water dropwise to the mixed solution until the pH value of the mixed solution reaches 8-10; (3) After aging the mixed solution obtained in step (2) at 50-90°C for 1-3h, centrifuge the obtained suspension, wash it, and dry it in vacuum; then roast it at 300-400°C for 2-6h to obtain xLi _-ZrO2 carrier, x=5-10%, wherein x represents the molar doping amount of lithium ions in lithium-doped monoclinic zirconia; (4) Dissolve hydrated indium nitrate in deionized water to form a solution with a concentration of 0.4-1M/L, and add the solution dropwise to the prepared xLi-ZrO ₂ carrier to ensure that the mass fraction of the loaded indium oxide is 6-10 %; Ultrasonic treatment, drying, and then roasting at 300-500°C for 4-6h to obtain In ₂ O ₃ /xLi-ZrO ₂ catalyst, x=5-10%. 2 . The lithium-doped zirconia-supported indium oxide catalyst according to claim 1 , wherein the lithium-doped monoclinic zirconia is a carrier, and the indium oxide is a catalytically active component. 3. a preparation method as described in any one of claim 1-2 lithium doped zirconia supported indium oxide catalyst, it is characterized in that, the method is carried out according to the following steps: (1) dissolving zirconium oxychloride octahydrate and lithium nitrate in deionized water in proportion according to the value of x to form a mixed solution with a concentration of 0.2-1M/L, and heating the mixed solution to 50-90°C; (2) constantly stirring the mixed solution obtained in step (1), and adding concentrated ammonia water dropwise to the mixed solution until the pH value of the mixed solution reaches 8-10; (3) After aging the mixed solution obtained in step (2) at 50-90°C for 1-3h, centrifuge the obtained suspension, wash it, and dry it in vacuum; then roast it at 300-400°C for 2-6h to obtain xLi _-ZrO2 carrier, x=5-10%, wherein x represents the molar doping amount of lithium ions in lithium-doped monoclinic zirconia; (4) Dissolve hydrated indium nitrate in deionized water to form a solution with a concentration of 0.4-1M/L, and add the solution dropwise to the prepared xLi-ZrO ₂ carrier to ensure that the mass fraction of the loaded indium oxide is 6-10 %; Ultrasonic treatment, drying, and then roasting at 300-500°C for 4-6h to obtain In ₂ O ₃ /xLi-ZrO ₂ catalyst, x=5-10%. 4. The preparation method of a lithium-doped zirconia-supported indium oxide catalyst according to claim 3, characterized in that the rate of adding concentrated ammonia water dropwise in step (2) is 20-50 drops/min. 5 . The preparation method of a lithium-doped zirconia-supported indium oxide catalyst according to claim 3 , characterized in that the vacuum drying temperature in step (3) is 80-100° C. and the time is 8-12 hours. 6. the preparation method of a kind of lithium-doped zirconia supported indium oxide catalyst according to claim 3, is characterized in that, the time of ultrasonic treatment in step (4) is 1-3h, and the temperature of vacuum drying is 80-100 ℃, the time is 8-12h. 7. An application of the lithium-doped zirconia-supported indium oxide catalyst according to any one of claims 1-2, characterized in that it is used for hydrogenation of carbon dioxide to prepare methanol. 8. the application of a kind of lithium-doped zirconia supported indium oxide catalyst according to claim 7, is characterized in that, carries out according to the following steps: (1) performing tableting and granulation treatment on the lithium-doped zirconia-supported indium oxide catalyst; (2) The granular catalyst prepared above is subjected to a high-pressure continuous reaction in a reaction gas at a reaction temperature of 250-350° C.

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