CN110586064A - 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 and a preparation method and application thereof. The catalyst is prepared by bulk doping zirconia with lithium atoms by a co-precipitation method. The carrier is obtained, and the indium oxide particles are uniformly loaded on the lithium-doped monoclinic zirconia carrier; during preparation, lithium and zirconium precursors are firstly added by a co-precipitation method, and the lithium-doped monoclinic oxide is obtained by precipitation, drying and roasting. Zirconium carrier; then indium oxide is supported on the carrier by a wet impregnation method, and the final catalyst is obtained after drying and calcining again. The catalyst prepared by the invention is suitable for the hydrogenation of carbon dioxide to methanol reaction, takes lithium-doped zirconia as a carrier and indium oxide as an active component, realizes a carbon dioxide conversion rate of more than 10% and a methanol selectivity of about 90%, and has a structural Simple, easy to prepare and low operating pressure, this series of catalysts also maintain long-term stability.

Description

A kind of lithium-doped zirconia supported indium oxide catalyst and preparation method and application thereof

technical field

The invention belongs to the technical field of supported oxide catalysts, and in particular relates to a lithium-doped zirconia supported indium oxide catalyst, a preparation method thereof, and an 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 global environment and sustainable development of human beings. Therefore, research on carbon dioxide emission reduction and transformation and utilization technologies has become an urgent problem to be solved. The carbon dioxide hydrogenation technology developed by the use of solar photo-splitting water for hydrogen production is not only conducive to reducing the concentration of carbon dioxide in the atmosphere, but also generates efficient fuels such as carbon monoxide, methane, methanol, dimethyl ether, ethanol, and hydrocarbons, which are convenient for storage and storage. transportation. Among them, it is easier to generate methanol in terms of thermodynamics and kinetics, and methanol is the raw material for the preparation of gasoline and diesel and C ₂ -C ₄ higher olefins through methanol to olefins, and it is also an important material for the preparation of many fine chemicals such as medicine, cosmetics, polyester, etc. 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 to methanol products has received more attention.

Due to the stable chemical properties of CO ₂ and the difficulty of 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 methanol production but not conducive to the activation of carbon dioxide. Therefore, it is necessary to select an appropriate reaction temperature. and designing efficient catalysts; on the other hand, carbon monoxide and methanol are two concomitant products in the hydrogenation of carbon dioxide, both have similar intermediates, and the reaction occurs at the same catalytic site, resulting in The selectivity is not high; therefore, how to design high-efficiency catalysts for kinetic control to promote _CO2 activation conversion and adjust the product selectivity, so that methanol can be efficiently obtained is an urgent problem to be solved.

At present, the widely studied catalyst for methanol synthesis is copper-zinc-aluminum catalyst, which has a high conversion rate of carbon dioxide, but the methanol selectivity is only about 60%, and the cost of subsequent separation steps is very high; Sintering inactivation, so that the reaction stability decreased. 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 high-temperature structure of the oxide is stable and not easy to be deactivated, so it has attracted more and more attention. Several regulatory pathways have been reported that are generally accepted to improve methanol yields for _CO hydrogenation. 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 carrier by changing the type of the carrier, 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 complicated and difficult to repeat, and are easily disturbed by environmental factors. Indium oxide-based catalysts are widely used in carbon dioxide hydrogenation reactions. How to further improve the catalyst to make it have stronger _CO2 activation ability and longer stability, especially higher methanol selectivity is the research focus of _CO2 hydrogenation.

SUMMARY OF THE INVENTION

The invention aims to solve the technical problems of poor selectivity (<60%) of a single product 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 preparation method thereof, and application in carbon dioxide hydrogenation, by doping lithium element into zirconia carrier, monoclinic zirconia of single pure phase is obtained, and then indium oxide is supported on monoclinic zirconia On the carrier, the carbon dioxide conversion rate of more than 10% and the methanol selectivity of about 90% are realized, and the catalyst can realize the stability of more than 20h.

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

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

Further, the lithium-doped monoclinic zirconia is used as a carrier, and the indium oxide is used as 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, and the The mixed solution is heated to 50-90℃;

(2) stirring the mixed solution obtained in step (1) continuously, and adding 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 and wash the obtained suspension, vacuum dry; then calcinate at 300-500°C for 2-6h to obtain xLi - ZrO ₂ support, x = 5-10%, where x represents the molar doping amount of lithium ions in lithium-doped monoclinic zirconia;

(4) Dissolve hydrated indium nitrate (In(NO ₃ ) ₃ ·H ₂ O) in deionized water to form a solution with a concentration of 0.4-1 M/L, and drop the solution 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 calcining at 300-500 ° C for 4-6 h, the In ₂ O ₃ /xLi-ZrO ₂ catalyst is obtained, x=5-10 %.

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

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

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

An application of the lithium-doped zirconia supported indium oxide catalyst for preparing methanol by hydrogenation of carbon dioxide.

Further, follow the steps below:

(1) subjecting the lithium-doped zirconia supported indium oxide catalyst to tablet granulation;

(2) The particulate 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:

In the present invention, indium oxide-supported zirconia is used as the main component, and a series of zirconia-supported indium oxide-based catalysts with different crystal forms can be prepared by changing the doping amount of lithium element (Li).

On the one hand, a small amount of Li-doped zirconia support ZrO ₂ (Li:Zr=5:95-10:90) exhibits a granular structure, and zirconia is mainly monoclinic; the difference between monoclinic zirconia and indium oxide The energy band structure is matched, and the two have strong electronic interaction, that is, zirconia can transfer electrons to indium oxide, while electron-rich indium oxide is beneficial to the activation of carbon dioxide and the breaking of carbon-oxygen bonds. Therefore, the catalyst obtained by the monoclinic zirconia supported by indium oxide, such as In ₂ O ₃ /5Li-ZrO ₂ , has a good effect on the hydrogenation of carbon dioxide, the carbon dioxide conversion rate is higher than 10%, and the methanol selectivity up to 88% with 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 was doped with excess Li (Li:Zr>20:80). The heterozygous zirconia support, for example: 40Li-ZrO ₂ (Li:Zr=40:60) also has a granular structure, but 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 support 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 monoclinic zirconia supported indium oxide catalyst, which further proves that the monoclinic zirconia support is the key to improving the methanol selectivity.

It can be seen that the crystal form of zirconia is transformed from tetragonal to monoclinic with the addition of Li, but when the amount of Li doping is too large, the crystal form of zirconia is transformed to tetragonal again. Indium oxide catalysts supported by zirconia with different crystal forms have different catalytic performances in carbon dioxide hydrogenation due to the different interactions between oxides. Whether it is carbon dioxide conversion or methanol selectivity, monoclinic zirconia supported catalysts have different catalytic performances. Indium oxide is obviously stronger than indium oxide supported by tetragonal zirconia. During the hydrogenation reaction of carbon dioxide, the methanol yield is positively correlated with the proportion of monoclinic zirconia in the catalyst support, indicating that the monoclinic The interaction between the zirconia and indium oxide indeed promotes the activation of carbon dioxide during the reaction and favors the formation of methanol. At the same time, due to the small amount of indium oxide, low toxicity, and the ability to hydrogenate carbon dioxide to produce methanol by a simple method under relatively low pressure, it has certain industrial significance.

Description of drawings

Fig. 1 is a graph showing the distribution of products obtained by the catalytic carbon dioxide hydrogenation of the In ₂ O ₃ /5Li-ZrO ₂ catalyst prepared in Example 1 and the change of carbon dioxide conversion rate with time (280° C., 30 bar, space velocity=3h ⁻¹ , CO ₂ / N ₂ /H ₂ =1/1/3);

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

Fig. 3 is a graph showing the variation of methanol yield with reaction temperature when the indium oxide-based catalysts prepared in Examples 1, 26, 29, and 30 catalyze carbon dioxide hydrogenation (225-350° C., 30 bar, 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 in Examples 1, 26, 29, and 30;

FIG. 5 shows the Raman spectra of the surfaces of the indium oxide-based catalysts prepared in Examples 1, 26, 29, and 30. FIG.

Detailed ways

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

Example 1

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

(2) Concentrated ammonia water (NH ₃ ·H ₂ O, concentration 22-25%) was added dropwise to the mixed solution of zirconium oxychloride and lithium nitrate of (1) at a rate of 20 drops/min, stirring continuously. down until the pH value of the mixed solution reaches 9, stop dripping;

(3) Aging reaction at 80°C for 2h, centrifuging the obtained suspension and washing four times with deionized water; drying the obtained solid in an oven at 80°C for 12h; drying the obtained solid in air at 300°C After calcination for 4h, 5Li-ZrO ₂ zirconia support was obtained.

(4) 0.21 g of hydrated indium nitrate (In(NO ₃ ) ₃ ·H ₂ O) was dissolved in deionized water to form a solution with a concentration of 0.7 M/L, and the solution was added dropwise to (3) with a mass of 1 g to obtain The 5Li-ZrO ₂ zirconia carrier (the mass fraction of supported indium oxide is 8%) was ultrasonically treated for 2h.

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

(6) tableting the above-mentioned powdered catalyst into a granular catalyst of 20-40 meshes;

(7) 0.2g of the catalyst after tableting is loaded into the fixed-bed reactor, N ₂ is introduced, punched to 30bar, and when reaching a reaction temperature of 280°C, it is switched to a reaction gas, wherein the molar ratio of carbon dioxide and hydrogen is 3:1, The equilibrium gas was nitrogen (CO ₂ =10 ml/min, H ₂ =30 mL/min, N ₂ =10 mL/min), and the reaction space velocity based on carbon dioxide was 3 h ⁻¹ .

The catalyst activity is expressed as methanol produced (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 , CO, n represents the carbon number.

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

Table 1. Product selectivity at 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 is basically unchanged after 5 hours of reaction.

Example 2:

The method of Example 1 was used to carry out the reaction, except that the concentration of the mixed solution in step (1) was 0.5M/L.

Example 3:

The method of Example 1 is used to carry out the reaction, and the difference is only that the concentration of the mixed solution in step (1) is 1M/L.

Example 4:

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

Example 6:

Adopt the method of embodiment 1 to react, and its difference is only in that step (2) mixed solution pH value finally reaches 8.0.

Example 7:

The method of Example 1 was used to carry out the reaction, and the difference was only that the pH value of the mixed solution in step (2) finally reached 10.

Example 8:

The reaction was carried out by the method of Example 1, the only difference being that the aging time of the mixed solution in step (3)) was 1 h.

Example 9:

The reaction was carried out by the method of Example 1, except that the aging time of the mixed solution in step (3) was 3h.

Example 10:

Adopt the method of embodiment 1 to carry out the reaction, and its difference is only that the dripping rate of the concentrated ammonia water of step (2) is 30 drops/min.

Example 11:

Adopt the method of embodiment 1 to carry out the reaction, and its difference is only that the drip rate of the concentrated ammonia water of step (2) is 50 drops/min.

Example 12:

The reaction was carried out by the method of Example 1, and the difference was only that the drying temperature of step (3) and step (5) were both 90°C.

Example 13:

The reaction was carried out by the method of Example 1, and the difference was only that the drying temperature of step (3) and step (5) were both 100°C.

Example 14:

The method of Example 1 was adopted to carry out the reaction, and the difference was only that the drying time of step (3) and step (5) were both 8h.

Example 15:

The method of Example 1 was adopted to carry out the reaction, and the only difference was that the drying time of step (3) and step (5) were both 10h.

Example 16:

The method of Example 1 was used to carry out the reaction, and the difference was only that the calcination temperature of step (3) and step (5) were both 400°C.

Example 17:

The reaction was carried out by the method of Example 1, and the difference was only that the calcination temperature of step (3) and step (5) were both 500°C.

Example 18:

Adopt the method of embodiment 1 to carry out the reaction, and its difference is only that the calcination time of step (3) is 2h.

Example 19:

Adopt the method of embodiment 1 to carry out the reaction, and its difference is only that the calcination time of step (3) is 6h.

Example 20:

The method of Example 1 is used for the reaction, and the difference is only that the concentration of the indium nitrate solution in step (4) is 0.4M/L.

Example 21:

The method of Example 1 is used for the reaction, and the difference is only that the concentration of the indium nitrate solution in step (4) is 1M/L.

Example 22:

The method of Example 1 was used for the reaction, except 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 method of Example 1 was used for the reaction, except that the mass fraction 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:

The method of Example 1 was used to carry out the reaction, except that the ultrasonic time in step (4) was 1 h.

Example 25:

The method of Example 1 was used to carry out the reaction, except that the ultrasonic time of step (4) was 3h.

Example 26:

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

Example 27:

The method of Example 1 was used for the reaction, except that in step (1), 2.9 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.04 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water (lithium The molar doping level is 7.5%).

Example 28:

The method of Example 1 was used to carry out the reaction, except that in step (1), 2.8 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.06 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water (lithium The molar doping amount is 10%).

Example 29:

The method of Example 1 was used to carry out the reaction, except that in step (1), 2.5 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.12 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water (lithium The molar doping level is 20%).

Example 30:

The method of Example 1 was used to carry out the reaction, except that in step (1), 1.9 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.24 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water (lithium The molar doping level is 40%).

Example 31:

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

Example 32:

The method of Example 1 is adopted to carry out the reaction, and the difference is only that the calcination time of step (5) is 6h.

Example 33:

The method of Example 1 was used to carry out the reaction, except that the reaction temperature in step (7) was 225°C.

Example 34:

The method of Example 1 was used to carry out the reaction, and the only difference was that the reaction temperature of step (7) was 250°C.

Example 35:

The method of Example 1 was used to carry out the reaction, and the only difference was that the reaction temperature of step (7) was 300°C.

Example 36:

The method of Example 1 was used to carry out the reaction, and the only difference was that the reaction temperature of step (7) was 350°C.

Example 37:

The method of Example 26 was used for the reaction, with the difference that the reaction temperature in step (7) was 225°C.

Example 38:

The method of Example 26 was used for the reaction, with the difference that the reaction temperature in step (7) was 250°C.

Example 39:

The method of Example 26 was used for the reaction, with the difference that the reaction temperature in step (7) was 300°C.

Example 40:

The method of Example 26 was used for the reaction, with the difference that the reaction temperature in step (7) was 350°C.

Example 41:

The method of Example 29 was used for the reaction, with the difference that the reaction temperature in step (7) was 225°C.

Example 42:

The method of Example 29 was used for the reaction, with the difference that the reaction temperature in step (7) was 250°C.

Example 43:

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

Example 44:

The method of Example 29 was used for the reaction, with the difference that the reaction temperature in step (7) was 350°C.

Example 45:

The method of Example 30 was used for the reaction, with the difference that the reaction temperature in step (7) was 225°C.

Example 46:

The method of Example 30 was used for the reaction, with the difference that the reaction temperature in step (7) was 250°C.

Example 47:

The method of Example 30 was used for the reaction, with the difference that the reaction temperature in step (7) was 300°C.

Example 48:

The method of Example 30 was used for the reaction, with the difference that the reaction temperature in step (7) was 350°C.

Example 49:

The method of Example 1 was used for the reaction, except that the carbon dioxide volume space velocity in step (7) was 1 h ^-1 .

Example 50:

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

Example 51:

The method of Example 1 was used for the reaction, except that the carbon dioxide volume space velocity in step (7) was 10 h ^-1 .

Example 52:

Adopt the method of embodiment 1 to react, the difference is only in that in step (1), 3.2g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) is added to 50ml of deionized water, and the carbon dioxide volume space velocity in step (7) is 1h ^-1 .

Example 53:

Adopt the method of embodiment 1 to react, the difference is only in that in step (1), 3.2g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) is added to 50ml of deionized water, and the carbon dioxide volume space velocity in step (7) is 5h ^-1 .

Example 54:

Adopt the method of embodiment 1 to react, the difference is only in that in step (1), 3.2g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) is added to 50ml of deionized water, and the carbon dioxide volume space velocity in step (7) is 10h ^-1 .

Example 55:

The method of Example 1 was used for the reaction, and the difference was that in step (1), 1.9 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.24 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water, and step ( 7) The carbon dioxide volume space velocity is 1 h ^-1 .

Example 56:

The method of Example 1 was used for the reaction, and the difference was that in step (1), 1.9 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.24 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water, and step ( 7) The carbon dioxide volume space velocity is 5h ^-1 .

Example 57:

The method of Example 1 was used for the reaction, and the difference was that in step (1), 1.9 g of zirconium oxychloride (ZrOCl ₂ ·8H ₂ O) and 0.24 g of lithium nitrate (LiNO ₃ ) were added to 50 ml of deionized water, and step ( 7) The carbon dioxide volume space velocity is 10 h ^-1 .

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

(1) The influence of the molar doping amount of lithium on the reactivity of the catalyst is shown in Table 2. The reaction conditions are the same as those in Examples 1, 26, 27, 28, 29, and 30.

Table 2. Effects 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 of lithium ions is x=5-10%, this series of lithium-doped zirconia supported indium oxide catalysts all show better carbon dioxide hydrogenation activity and methanol selection. , 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 reactivity of the catalyst and the crystal form of zirconia, see Tables 2, 3, 4, and 5 in the accompanying drawings. The reaction conditions are the same as those in Examples 1, 26, 29, and 30.

It can be seen from Fig. 2 and Fig. 3 that in the range of carbon dioxide hydrogenation reaction temperature of 225-350 °C, with the increase of the molar doping amount of Li (5-40%), the carbon dioxide conversion rate and methanol selectivity are also related. The yield of methanol gradually decreased while the selectivity of carbon monoxide gradually increased. At the optimum reaction temperature of 280℃, the selectivity of methanol decreased from 86% of In ₂ O ₃ /5Li-ZrO ₂ to In ₂ O ₃ /40Li -61% of ZrO ₂ , the carbon monoxide selectivity is improved from 12% of In ₂ O ₃ /5Li-ZrO ₂ to 39% of In ₂ O ₃ /40Li-ZrO ₂ . The reactivity of all samples could be maintained for at least 5 hours without degradation, indicating that the catalysts had good stability.

It is worth noting that the undoped zirconia is still tetragonal, and the carbon dioxide conversion rate and methanol selectivity are not high; a small amount of Li doping (5-10% molar doping) 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 type. 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 a monoclinic crystal type. It can be seen that with the continuous increase of the Li doping amount (the molar doping amount is 10-40%), the bulk crystal form of zirconia shows a transition from monoclinic to tetragonal, and at the same time, the surface crystal form also shows the same trend of change.

(3) The effect of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /5Li-ZrO ₂ is shown in Table 3. The reaction conditions are the same as those in Examples 1, 33, 34, 35 and 36.

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

Reaction temperature (℃) 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 with the increase of reaction temperature, the conversion rate of carbon _{dioxide hydrogenation} increases significantly, that is, the reaction activity increases gradually; The change is very sensitive. As the reaction temperature increases, the methanol selectivity gradually decreases, while the carbon monoxide selectivity gradually increases; referring to Figure 3, when the reaction temperature is 280 °C, the methanol yield reaches the maximum value.

(4) The effect of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /ZrO ₂ is shown in Table 4. The reaction conditions were the same as those in Examples 26, 37, 38, 39 and 40.

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

Reaction temperature (℃) 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 with the increase of the reaction temperature, 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 is very dependent on 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 value, but a certain amount of carbon monoxide is still produced at this time; The methane selectivity of In ₂ O ₃ /ZrO ₂ is lower than that of In ₂ O ₃ /5Li-ZrO ₂ at any reaction temperature.

(5) 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 those in Examples 29, 41, 42, 43 and 44.

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

Reaction temperature (℃) 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 with the increase of the reaction temperature, the conversion rate of carbon dioxide hydrogenation increases significantly, that is, the reaction activity gradually increases; for the In ₂ O ₃ /20Li-ZrO ₂ catalyst, with the increase of the reaction temperature 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 value, 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 .

(VI) Influence of carbon dioxide hydrogenation reaction temperature on the catalytic activity of In ₂ O ₃ /40Li-ZrO ₂ , see Table 6. The reaction conditions are the same as those in Examples 30, 45, 46, 47 and 48.

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

Reaction temperature (℃) 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 with the increase of the reaction temperature, the conversion rate of carbon dioxide hydrogenation increases significantly, that is, the reaction activity gradually increases; for In ₂ O ₃ /40Li-ZrO ₂ catalyst, with the increase of the reaction temperature , the methanol selectivity gradually decreases, while the carbon monoxide selectivity gradually increases; referring to Figure 3, when the reaction temperature is 280 °C, the methanol yield reaches the maximum value, and 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 and product distribution of the three samples are consistent with the trend of changing reaction temperature, but the difference in product selectivity between them is very obvious, and this difference is universal with temperature change and does not change.

(7) The effect of carbon dioxide volume space velocity on the catalytic activity of the catalyst is shown in Table 7. The reaction conditions are the same as those in Example 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 volumetric space velocity of carbon dioxide, the conversion rate of carbon dioxide continues to decrease, but the selectivity of ^methane and carbon ^monoxide is basically unchanged. The carbon dioxide volume space velocity is 3h ^-1 .

(8) Influence of the calcination temperature in step (3) and step (5) on the catalytic activity of the catalyst. The reaction conditions are the same as those in Examples 1, 16 and 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 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.

It has been proved by experiments 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 are 0.2-1M/L. Keep at 50-100 ℃, add concentrated ammonia water dropwise until the pH value of the mixed solution is in the range of 8-10; the aging time is 1-3h, and the calcination time is 2-6h, the obtained xLi-ZrO ₂ carrier is in the crystal form, particle size, There is no significant difference in surface structure, etc.;

In addition, different solution concentrations of hydrated indium nitrate (In(NO ₃ ) ₃ ·H ₂ O) (0.4-1M/L), mass fraction of loaded indium oxide (6-10%); ultrasonic treatment time (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 with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. Under the inspiration of the present invention, without departing from the scope of the present invention and the protection scope of the claims, personnel can also make many specific transformations, which all fall within the protection scope of the present invention.

Claims (10)

1. a lithium-doped zirconia supported indium oxide catalyst is characterized in that, comprising lithium-doped monoclinic zirconia, and the lithium-doped monoclinic zirconia is carried out by co-precipitation method on zirconia with lithium atoms. prepared by bulk doping, the molar doping amount of lithium ions in the lithium-doped monoclinic zirconia is x=5-10%; the lithium-doped monoclinic zirconia is uniformly loaded with indium oxide particles, The mass percentage of the indium oxide in the lithium-doped monoclinic zirconia is 6-10%. 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 . 3 . The lithium-doped zirconia supported indium oxide catalyst according to claim 1 , wherein the lithium-doped monoclinic zirconia has a particle size range of 50-100 nanometers. 4 . 4 . The lithium-doped zirconia supported indium oxide catalyst according to claim 1 , wherein the particle size of the indium oxide particles ranges from 8 to 15 nanometers. 5 . 5. A method for preparing a lithium-doped zirconia supported indium oxide catalyst according to any one of claims 1-4, wherein the method is carried out according to the following steps: (1) zirconium oxychloride octahydrate and lithium nitrate 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, and the mixed solution is heated to 50-90 ° C; (2) stirring the mixed solution obtained in step (1) continuously, 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 and wash the obtained suspension, vacuum dry; then calcinate at 300-500°C for 2-6h to obtain xLi - ZrO ₂ support, x = 5-10%, where 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 drop the solution onto the prepared xLi-ZrO ₂ carrier to ensure that the mass fraction of supported indium oxide is 6-10 %; after ultrasonic treatment and drying, and then calcined at 300-500° C. for 4-6 h to obtain In ₂ O ₃ /xLi-ZrO ₂ catalyst, x=5-10%. 6 . The method for preparing a lithium-doped zirconia-supported indium oxide catalyst according to claim 5 , wherein in step (2), the rate of dripping concentrated ammonia water is 20-50 drops/min. 7 . 7 . The method for preparing a lithium-doped zirconia-supported indium oxide catalyst according to claim 5 , wherein the vacuum drying temperature in step (3) is 80-100° C. and the time is 8-12 h. 8 . 8 . The method for preparing a lithium-doped zirconia supported indium oxide catalyst according to claim 5 , wherein the time of ultrasonic treatment in step (4) is 1-3h, and the temperature of vacuum drying is 80-100 ℃. 9 . ℃, the time is 8-12h. 9. An application of the lithium-doped zirconia supported indium oxide catalyst according to any one of claims 1 to 4, characterized in that it is used for the hydrogenation of carbon dioxide to prepare methanol. 10. the application of a kind of lithium-doped zirconia supported indium oxide catalyst according to claim 9, is characterized in that, carry out according to the following steps: (1) subjecting the lithium-doped zirconia supported indium oxide catalyst to tablet granulation; (2) The particulate catalyst prepared above is subjected to a high-pressure continuous reaction in a reaction gas at a reaction temperature of 250-350°C.