CN104117361A - Copper-based catalyst by use of thorium as assistant for methanol synthesis and preparation method thereof - Google Patents

Abstract

The invention discloses a copper-based catalyst for methanol synthesis with thorium as an auxiliary agent and a preparation method thereof, relating to a copper-based catalyst for methanol synthesis. The catalyst contains oxides of Cu, Zn, Al and Th, and the content is 0.1%-2% of thorium oxide, 25%-75% of copper oxide, 20%-55% of zinc oxide, and the balance is aluminum oxide. Prepared by co-precipitation method. It can improve the pore size, activity and heat resistance of methanol synthesis catalyst. Compared with the catalyst without adding thorium oxide, the catalyst with 0.2%-0.5% thorium oxide additive has a pore diameter expanded from 6.91nm to 8.65-8.74nm, the initial activity is increased by 15%-18%, and the activity after heat resistance is increased by 7. % ~ 13%. The method of doping with thorium oxide is simple and the amount of doping is small.

Description

Copper-based catalyst for methanol synthesis with thorium as auxiliary agent and preparation method thereof

technical field

The invention relates to a copper-based catalyst for methanol synthesis, in particular to a copper-based catalyst for methanol synthesis with thorium as an auxiliary agent and a preparation method thereof.

Background technique

Methanol is an important organic chemical raw material, widely used in pesticides, medicines, dyes, coatings and national defense industries. With the development of science and technology and the change of energy structure in the world today, it has become a trend to use methanol as a new source of petrochemical raw materials. The synthesis of methanol from synthesis gas has been industrialized. At present, the medium and low pressure gas phase method is widely used in the world to synthesize methanol, and the catalysts used are mainly mixed oxides of copper, zinc and aluminum. However, due to the large heat release in the synthesis of methanol, it is easy to cause the deactivation of the copper-based catalyst and shorten the service life of the catalyst. When synthesizing methanol with low _CO2 -containing synthesis gas, if Cu-Zn-Al three-way catalyst is still used, due to the strong reducibility of the reaction raw material gas, the Cu ⁺ catalytically active species is easily reduced to Cu ⁰ and lead to problems such as catalyst deactivation. How to improve the thermal stability of copper-based catalysts and prolong their service life is a problem of concern. This patent uses the principle of ion doping valence state compensation method to stabilize the valence state of Cu ⁺ species on the surface of the catalyst, and adds a small amount of metal ions Th ⁴⁺ with higher valence state to the Cu-Zn-Al three-component low-pressure methanol synthesis catalyst to produce A Cu-Zn-Al-Th methanol synthesis catalyst is obtained, and the catalyst has good catalytic activity and heat resistance.

Chinese patent CN1810357A discloses a methanol catalyst which is obtained by coprecipitating Cu, Zn, Al, Li nitrate mixed solution and Na ₂ CO ₃ solution. The doping of Li makes the catalyst applicable to a wider range, not only for low CO ₂ synthesis gas, but also for high CO ₂ synthesis gas, and it still maintains a high level when the proportion of CO ₂ is 27%. activity and selectivity. Li Congming, Xingdong Yuan and Kaoru Fujimoto of Tokyo Gas Synthesis Co., Ltd., Japan found that Zr-doped CuO/ZnO/Al ₂ O ₃ catalysts, metal Zr can increase the surface area of copper, and can increase the concentration of metal copper on the surface, These are very helpful to improve the activity of the reaction (Catalysis A: General 469 (2014) 306-311). C.Seller and R.Prins from the Chemical Technology Laboratory of the Swiss Federal Institute of Technology found that doping a trace amount of Li in the Pd-SiO ₂ synthesis methanol catalyst can improve the activity of the catalyst, and has a high selectivity for methanol sex (99%) (Catalysis Letters 47 (1997) 83-89).

Although the additives used for metal doping in the past have improved the space-time yield and conversion rate, they have the disadvantages of complex catalyst preparation procedures, unsuitable for large-scale production and high cost of added metal additives.

Contents of the invention

The object of the present invention is to provide a copper-based catalyst for synthesizing methanol with thorium as an auxiliary agent, which can increase the pore size of the copper-based catalyst and improve the activity and heat resistance, and a preparation method thereof.

The copper-based catalyst for synthesizing methanol with thorium as an auxiliary agent includes oxides of Cu, Zn, Al and Th, and the content of each component in the copper-based catalyst in terms of mass percentage is: 0.1% to 2% of thorium oxide, 25% to 20% of copper oxide 75%, 20% to 55% of zinc oxide, and the balance is aluminum oxide; the mass percent content of each component of the catalyst is preferably 0.2% to 0.5% of thorium oxide, 60% to 75% of copper oxide, and 20% of zinc oxide ~25%, the balance is alumina.

The preparation method of the copper-based catalyst for synthesizing methanol with thorium as an auxiliary agent comprises the following steps:

1) Dissolve the measured nitrates of Cu, Zn, and Th in water, and prepare Cu(NO ₃ ) ₂ , 1 mol/L Zn(NO ₃ ) ₂ solutions and 0.045 mol/L molar concentration respectively in water. Th(NO ₃ ) ₄ solution of L; then mix Cu(NO ₃ ) ₂ and Zn(NO ₃ ) ₂ solutions to make a mixed solution of Cu(NO ₃ ) ₂ and Zn(NO ₃ ) ₂ , which is called the mixed solution A, then add the Th(NO ₃ ) ₄ solution into the mixed solution A to make a mixed solution of Cu(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ and Th(NO ₃ ) ₄ , which is called mixed solution B;

2) Dissolve anhydrous Na ₂ CO ₃ in water to make a Na ₂ CO ₃ solution with a molar concentration of 0.5 mol/L;

3) Heat the Na ₂ CO ₃ solution with a molar concentration of 0.5 mol/L to 65-82°C, then add it into the mixed solution B, control the pH=8-9 as the end point, and after aging, obtain copper-zinc-thorium basic carbon salt mixture;

4) dissolving the soluble salt of Al in water to form an Al soluble salt solution with a molar concentration of 1 mol/L; adding the ammonia solution to the Al soluble salt solution to obtain an aluminum sol;

5) Mix the copper-zinc-thorium basic carbonate mixture obtained in step 3) with the aluminum sol obtained in step 4), then filter and drain the precipitate, after washing, filter and drain again, dry the obtained filter cake, and calcinate , and tablet molding to obtain a copper-based catalyst for methanol synthesis with thorium as an auxiliary agent.

In step 1), the water can be deionized water.

In step 2), the water can be deionized water.

In step 3), the aging condition may be aging at 80-85° C. for 1 hour.

In step 4), the water can be deionized water; the ammonia solution can be 1:5 by volume ratio ammonia water: water; after the ammonia solution is added to the Al soluble salt solution, it can be heated at 70-85 ° C. Stir for 1 h; the soluble salt of Al can be aluminum nitrate.

In step 5), the washing may be performed with distilled water for 6 times; the drying condition may be 2 hours at 110° C.; the calcination condition may be 330° C. for 3 hours.

Compared with the methanol synthesis catalyst prepared by the traditional method, the invention can improve the pore size, activity and heat resistance of the methanol synthesis catalyst. Compared with the catalyst without adding thorium oxide, the pore diameter of the catalyst added with 0.2%-0.5% (mass percentage) thorium oxide promoter was expanded from 6.91nm to 8.65-8.74nm, and the initial activity was increased by 15%-18%. After the activity increased by 7% to 13%. The method of using thorium oxide doping in the present invention is simple, the amount of doping is small, and has good application significance and scientific research value.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. These examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.

In the following examples, the catalyst was reduced for 20 hours with a hydrogen-nitrogen gas mixture with a low concentration of hydrogen (H ₂ /N ₂ =3/97), and the maximum reduction temperature was 235°C. The activity evaluation of the catalyst is carried out on a miniature fixed-bed reaction device. The main components of the reaction device include the SK2-1-8 tubular resistance furnace (produced by China Shanghai Shiyan Circuit Co., Ltd., rated power 1kw, rated voltage 220v), built-in A quartz reaction tube with a diameter of 8 mm and a length of 60 cm, a valve (from Xiongchuan Company), a flow meter (from Beijing Seven Star Huachuang Company) and a pressure gauge (from Beijing Seven Star Huachuang Company). The catalyst loading is 0.5ml, the feed gas composition is CO: _{H 2} :CO ₂ :N ₂ =14:76:5:5 (volume ratio), the reaction pressure is 5.0MPa, the space velocity is 10000h ^-1 , and the evaluation temperature is At 230°C, the measurement result is called the initial activity; then the catalyst is heat-treated at 400°C for 5 hours in the synthesis atmosphere, and then the measurement result at 230°C is called the activity after heat treatment. The product was analyzed by gas chromatography, and the activity of the catalyst was expressed by methanol space-time yield (g.ml ^-1 _cat .h ^-1 ). The space-time yield is defined as:

$\mathrm{STY}=\frac{A\×C^0\×V^0\×S}{A^0\×L}$ (g.ml ^-1 _cat.h ^-1 )

A—the peak area of methanol in the product; A ⁰ —the peak area of a certain volume of methanol standard solution;

C ⁰ —concentration of methanol standard solution (mol.l ⁻¹ ); V ⁰ —volume of methanol standard solution;

S—space velocity; L—injection tube volume.

Example 1

Preparation of copper zinc aluminum thorium mixed oxide catalyst

1. Take 140 mL of Cu(NO ₃ ) ₂ solution with a concentration of 1 mol L ^-1 and 60 mL of Zn( ^NO ₃ ) ₂ solution with a concentration of 1 mol L -1 , put them in a 400 mL container, stir and mix;

2. Take 1ml of Th(NO ₃ ) ₄ solution with a concentration of 0.045mol/L and add it to the above solution, stir and mix to make a mixed solution of Cu(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ and Th(NO ₃ ) ₄ ;

3. Heat the metered Na ₂ CO ₃ solution to 65°C, and add it to the mixture of Cu(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ and Th(NO ₃ ) ₄ prepared in step 2 above under rapid stirring In the solution, control the pH = 9.0 as the end point, and age at 85°C for 1 hour to obtain a copper-zinc-thorium basic carbonate mixture;

4. Heat 18 ml of Al(NO ₃ ) ₃ solution with a concentration of 1 mol/L to 82°C, add 45 ml of ammonia solution with a volume ratio of 1:5 into the Al(NO ₃ ) ₃ solution under rapid stirring to prepare aluminum sol, Gained aluminum sol is standby after stirring for 1 h;

5. Mix the obtained copper, zinc, thorium basic carbonate mixture and the aluminum sol obtained in step 4 to obtain a precipitate, filter and drain the precipitate, and wash 6 times with distilled water repeatedly;

6. Filter and drain, the obtained filter cake is dried at 110°C for 2 hours, crushed, and roasted in a muffle furnace at 330°C for 3 hours;

7. The catalyst prepared in step 6 is pressed into tablets, crushed and sieved, and a 20-40 mesh catalyst sample is taken for later use. The catalyst prepared in this way contains 0.2% (mass percentage) of thorium oxide, 60% of copper oxide, 25% of zinc oxide, and 14.8% of aluminum oxide, which is recorded as Cat1. The activity evaluation results are listed in Table 1.

Embodiment 2-4

The preparation process is the same as in Example 1, except that in the second step, the amount of thorium nitrate additive is respectively 0.045mol/LTh(NO ₃ ) ₄ solution 2.5ml, 5ml and 10ml. ThO in the catalyst made in this way ₂ mass The percentages are 0.5%, 1% and 2% respectively, which are recorded as cat2, cat3 and cat4 respectively. The activity evaluation results are listed in Table 1.

Example 5

The preparation process is the same as in Example 1, except that in the first step, the Cu(NO ₃ ) ₂ solution with a concentration of 1 mol L ^-1 is 120 mL and the Zn(NO ₃ ) ₂ solution with a concentration of 1 mol L ^-1 is 80 ml In the catalyst made in this way, ThO ₂ mass percentage is 0.2%, copper oxide mass percentage 55%, zinc oxide mass percentage 30%, aluminum oxide mass percentage 14.8%, is recorded as cat5. The activity evaluation results are listed in Table 1.

Example 6

The preparation process was the same as in Example 1, except that in step 1, the Cu(NO ₃ ) ₂ solution with a concentration of 1 mol·L ⁻¹ was 160 mL and the Zn(NO ₃ ) ₂ solution with a concentration of 1 mol·L ⁻¹ was 40 mL. In the catalyst made in this way, _ThO2 content is 0.2% (mass percentage), copper oxide 65% (mass percentage), zinc oxide 20% (mass percentage), aluminum oxide 14.8% (mass percentage), and is recorded as cat6. The activity evaluation results are listed in Table 1.

Example 7

The preparation process was the same as in Example 1 except that in step 1, the Cu(NO ₃ ) ₂ solution with a concentration of 1 mol·L ⁻¹ was 60 mL and the Zn(NO ₃ ) ₂ solution with a concentration of 1 mol·L −1 was 140 ^mL ; In step 2, take concentration and be 0.045mol/L Th(NO ₃ ) ₄ solution 3ml is added in the appeal solution, in the catalyst of making like this, _ThO Content is 0.5% (mass percentage), copper oxide 25% (mass percentage), Zinc oxide 55% (mass percentage), aluminum oxide 14.5% (mass percentage), recorded as cat7. The activity evaluation results are listed in Table 1.

Comparative example 1

The preparation steps of the catalyst of Comparative Example 1 are the same as those of Example 1. Just do not add thorium nitrate solution for co-precipitation. The activity evaluation results are listed in Table 1.

Table 1: Catalyst Activity Evaluation Results of Examples

Calculation of CO conversion rate

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \%</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}\mathrm{<span\; class="notranslate">\; V</span>}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; CO</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

because $C_{N2}^0=\frac{{\mathrm{no}}_{N_2}^0}{V^0},C_{N2}=\frac{{\mathrm{no}}_{N_2}}{V},$ and ${\mathrm{no}}_{N_2}^0={\mathrm{no}}_{N_2},$ but $x_{\mathrm{CO}}(\%)=(1-\frac{C_{\mathrm{CO}}/C_{N_2}}{C_{\mathrm{CO}}^0/C_{N_2}^0})\&times;100\%$

- the amount of CO at the reactor inlet; _nCO - the amount of CO at the reactor outlet;

- the volume percentage of CO at the reactor inlet; C _CO - the volume percentage of CO at the reactor outlet;

- the amount of substance at the reactor inlet _N2 ; - the amount of substance at the reactor outlet _N2 ;

-The volume percentage of _N at the reactor inlet; -The volume percentage of _N at the reactor outlet;

V ⁰ —the volume of the gas at the inlet of the reactor; V—the volume of the gas at the outlet of the reactor.

Claims (10)

1. The copper-based catalyst for synthesizing methanol with thorium as an auxiliary agent is characterized in that it contains oxides of Cu, Zn, Al and Th, and the content of each component in the copper-based catalyst by mass percentage is: 0.1% to 2% of thorium oxide, oxidized 25% to 75% of copper, 20% to 55% of zinc oxide, and the balance is aluminum oxide. 2. as claimed in claim 1, thorium is used as the copper-based catalyst for synthesizing methanol as an auxiliary agent, wherein the content of each component in the copper-based catalyst by mass percentage is: 0.2% to 0.5% of thorium oxide, and 60% to 75% of copper oxide , zinc oxide 20% to 25%, the balance is aluminum oxide. 3. as claimed in claim 1, thorium is used as the preparation method of the methanol synthesis copper-based catalyst of auxiliary agent, it is characterized in that comprising the following steps: 1) Dissolve the measured nitrates of Cu, Zn, and Th in water, and prepare Cu(NO ₃ ) ₂ , 1 mol/L Zn(NO ₃ ) ₂ solutions and 0.045 mol/L molar concentration respectively in water. Th(NO ₃ ) ₄ solution of L; then mix Cu(NO ₃ ) ₂ and Zn(NO ₃ ) ₂ solutions to make a mixed solution of Cu(NO ₃ ) ₂ and Zn(NO ₃ ) ₂ , which is called the mixed solution A, then add the Th(NO ₃ ) ₄ solution into the mixed solution A to make a mixed solution of Cu(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ and Th(NO ₃ ) ₄ , which is called mixed solution B; 2) Dissolve anhydrous Na ₂ CO ₃ in water to make a Na ₂ CO ₃ solution with a molar concentration of 0.5 mol/L; 3) Heat the Na ₂ CO ₃ solution with a molar concentration of 0.5 mol/L to 65-82°C, then add it into the mixed solution B, control the pH=8-9 as the end point, and after aging, obtain copper-zinc-thorium basic carbon salt mixture; 4) dissolving the soluble salt of Al in water to form an Al soluble salt solution with a molar concentration of 1 mol/L; adding the ammonia solution to the Al soluble salt solution to obtain an aluminum sol; 5) Mix the copper-zinc-thorium basic carbonate mixture obtained in step 3) with the aluminum sol obtained in step 4), then filter and drain the precipitate, after washing, filter and drain again, dry the obtained filter cake, and calcinate , and tablet molding to obtain a copper-based catalyst for methanol synthesis with thorium as an auxiliary agent. 4. as claimed in claim 3, thorium is used as the preparation method of the methanol synthesis copper-based catalyst of auxiliary agent, it is characterized in that in step 1), 2), 4), described water adopts deionized water. 5 . The method for preparing a copper-based catalyst for methanol synthesis with thorium as an auxiliary agent according to claim 3 , characterized in that in step 3), the aging condition is aging at 80-85° C. for 1 h. 6. The preparation method of methanol synthesis copper-based catalyst with thorium as auxiliary agent as claimed in claim 3, characterized in that in step 4), the ammonia solution is 1:5 by volume of ammonia water: water. 7. as claimed in claim 3, thorium is used as the preparation method of the methanol synthesis copper-based catalyst of auxiliary agent, it is characterized in that in step 4), after described ammonia solution is added to Al soluble salt solution, stir at 70～85 ℃ 1h. 8. The preparation method of the methanol synthesis copper-based catalyst with thorium as an auxiliary agent according to claim 3, characterized in that in step 4), the soluble salt of Al is aluminum nitrate. 9. The method for preparing copper-based catalyst for methanol synthesis with thorium as auxiliary agent according to claim 3, characterized in that in step 5), the washing is performed 6 times with distilled water. 10. as claimed in claim 3, thorium is used as the preparation method of the methanol synthesis copper-based catalyst of auxiliary agent, it is characterized in that in step 5), the condition of described drying is to dry 2h at 110 ℃; The calcined The condition is to calcinate at 330°C for 3h.