An alkaline earth metal modified copper-based catalyst, a preparation method thereof and application thereof in carbon dioxide hydrogenation to methanol

Abstract

The application discloses an alkaline earth metal modified copper-based catalyst and a preparation method and application thereof in carbon dioxide hydrogenation to prepare methanol, relates to the technical field of catalysts, and the preparation method of the catalyst comprises the following steps: fully grinding and mixing strontium acetate, copper acetate monohydrate, zinc acetate dihydrate and zirconium acetate with anhydrous oxalic acid, drying at high temperature, then high-temperature calcining for a period of time, and naturally cooling to obtain a product. The product is tabletted and granulated to obtain the alkaline earth metal modified copper-based catalyst. The alkaline earth metal modified copper-based catalyst provided by the application has the advantages of good catalytic activity and high selectivity in the reaction of carbon dioxide hydrogenation to prepare methanol; wherein in the process of carbon dioxide hydrogenation, the alkaline earth metal modified copper-based catalyst can obtain a CO2 conversion rate of 6.2% and a methanol selectivity of 93% at a low temperature of 160 DEG.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst technology, in particular to an alkaline earth metal modified copper-based catalyst, a preparation method thereof and application thereof in carbon dioxide hydrogenation to methanol. BACKGROUND

[0002] Methanol, as a basic organic chemical raw material, can be used for preparing various organic chemical products such as formic acid, methyl formate and acetic acid. With the rapid development of economy and the increasing shortage of energy, methanol has great potential and good development prospects in the fields of vehicle fuel and fuel cells.

[0003] The commonly used catalyst for CO2 hydrogenation to methanol is Cu-ZnO-Al2O3, in which Cu and ZnO are active phases and Al2O3 is a structural promoter. However, the catalyst is unstable in use and is prone to sintering and loss of activity, thus having a short service life and poor stability. SUMMARY

[0004] Therefore, the present application provides an alkaline earth metal modified copper-based catalyst, a preparation method thereof and application thereof in carbon dioxide hydrogenation to methanol, which has good catalytic activity and high selectivity in the reaction of carbon dioxide hydrogenation to methanol.

[0005] The present application provides an alkaline earth metal modified copper-based catalyst, and the raw materials for preparing the copper-based catalyst include strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid, and the ratio is (0.1 ~ 0.2) g:(5 ~ 15) mmol:(2 ~ 5):mmol:(2 ~ 5) mmol:(40 ~ 100) mmol.

[0006] Meanwhile, the present application also provides a preparation method of the catalyst, which specifically includes the following steps:

[0007] The strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid are fully ground and mixed at room temperature, heated at a constant speed to a first temperature and then incubated for a period of time to obtain a second mixture;

[0008] The second mixture is heated at a constant speed to a second temperature and incubated for a period of time, and the alkaline earth metal modified copper-based catalyst is obtained after natural cooling;

[0009] The first temperature is 100 ~ 140℃, and the second temperature is 350 ~ 450℃.

[0010] Preferably, the heating rate for heating at a constant speed to the first temperature is 5℃ / min ~ 15℃ / min, and the heating rate for heating at a constant speed to the second temperature is 5℃ / min ~ 15℃ / min.

[0011] Preferably, the holding time at the first temperature is 10h-14h, and the holding time at the second temperature is 2h-4h.

[0012] The application further provides a method for using the catalyst, and the copper-based catalyst is used in a reaction of preparing methanol by hydrogenating CO2.

[0013] Compared with the prior art, the application has the following beneficial effects:

[0014] The copper-based catalyst modified by the alkaline earth metal has good catalytic activity and high selectivity in the reaction of preparing methanol by hydrogenating CO2, and has an industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The XRD pattern of the copper-based catalyst of Example 1 of the application;

[0016] Figure 2 The catalytic performance graph of the copper-based catalyst of Example 1 of the application;

[0017] Figure 3 The XRD pattern of the copper-based catalyst of Example 2 of the application;

[0018] Figure 4 The catalytic performance graph of the copper-based catalyst of Example 2 of the application;

[0019] Figure 5 The XRD pattern of the copper-based catalyst of Example 3 of the application;

[0020] Figure 6 The catalytic performance graph of the copper-based catalyst of Example 3 of the application;

[0021] Figure 7 The XRD pattern of the copper-based catalyst of Comparative Example 1 of the application;

[0022] Figure 8 The catalytic performance graph of the copper-based catalyst of Comparative Example 1 of the application;

[0023] Figure 9 The XRD pattern of the copper-based catalyst of Comparative Example 2 of the application;

[0024] Figure 10 The catalytic performance graph of the copper-based catalyst of Comparative Example 2 of the application. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in details below with reference to the accompanying drawings and in conjunction with specific embodiments. However, the present application can be implemented in different forms and should not be interpreted as being limited to the embodiments presented herein. On the contrary, these embodiments are presented to make the present application thorough and complete and to fully convey the scope of the present application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions can be exaggerated for clarity, and the same reference numerals are used throughout to represent the same elements.

[0026] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present application. The terms "include", "contain" and the like used herein indicate the presence of the stated features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0027] The present application provides an alkaline earth metal modified copper-based catalyst, and raw materials for preparing the copper-based catalyst are strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid, and the proportions are (0.1 ~ 0.2) g: (5 ~ 15) mmol: (2 ~ 5) mmol: (2 ~ 5) mmol: (40 ~ 100) mmol.

[0028] At the same time, the present application also provides a preparation method of the catalyst, which specifically comprises the following steps:

[0029] The strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid are fully ground and mixed at room temperature, heated at a constant speed to a first temperature and then incubated for a period of time to obtain a second mixture;

[0030] The second mixture is heated at a constant speed to a second temperature and incubated for a period of time, and the alkaline earth metal modified copper-based catalyst is obtained after natural cooling;

[0031] The first temperature is 100 ~ 140℃, and the second temperature is 350 ~ 450℃.

[0032] Preferably, the heating rate to the first temperature is 5℃ / min ~ 15℃ / min, and the heating rate to the second temperature is 5℃ / min ~ 15℃ / min.

[0033] Preferably, the incubation time at the first temperature is 10h ~ 14h, and the incubation time at the second temperature is 2h ~ 4h.

[0034] The present application also provides an application method of the catalyst, and the copper-based catalyst is used in a reaction of preparing methanol by CO2 hydrogenation.

[0035] A test method is provided as follows to verify the performance of the catalyst.

[0036] Specifically, the carbon dioxide hydrogenation to methanol reaction is carried out in a fixed bed reactor at 50 bar pressure and 160°C. The catalyst is loaded into a fixed bed reactor with an inner diameter of 9 mm, and then 50 bar of reaction gas (72 vol% H2, 24 vol% CO2 and 4 vol% Ar, Ar as internal standard) is introduced into the fixed bed reactor as the raw gas at a gas flow rate of 40 mL·min-1.

[0037] The present application uses two gas chromatographs to detect the products and reactants online, and analyzes H2, CO, CO2, CH4 and Ar through a carbon molecular sieve column (TDX-1) with a thermal conductivity detector (TCD); CH4 and CH3OH are analyzed using a PLOT-Q chromatographic column with a flame ionization detector (FID), and CH4 is used as a reference bridge between TCD and FID. Assuming that the amount of Ar remains constant after the reaction, the CO2 conversion rate is calculated according to the internal standard method.

[0038] The CO2 conversion rate is calculated based on carbon atoms, and the formula is as follows:

[0039] CO2 conversion rate = (CO2inlet-CO2outlet) / CO2inlet x 100%;

[0040] Wherein, CO2inlet and CO2 outlet are the number of moles of CO2 at the inlet and outlet, respectively.

[0041] The preparation method of the designed alkaline earth metal modified copper-based catalyst and its application in the reaction of CO2 hydrogenation to methanol are described below. It should be noted that this example is only a specific embodiment of the present application and cannot limit the protection scope of the present application.

[0042] Example 1

[0043] The alkaline earth metal modified copper-based catalyst is prepared by the following method:

[0044] First, 0.1 g of strontium acetate, 5 mmol of copper acetate monohydrate, 2 mmol of zinc acetate dihydrate, 2 mmol of zirconium acetate and 40 mmol of anhydrous oxalic acid are mixed at room temperature, and the mixture is thoroughly ground at room temperature, then the mixture is heated to 120°C in an oven at a heating rate of 10°C / min, and dried for 12 h, and then the obtained product is heated to 400°C in a muffle furnace at a heating rate of 5°C / min and kept for 3 h, and after natural cooling to room temperature, the product is obtained.

[0045] The prepared alkaline earth metal modified copper-based catalyst is tested for carbon dioxide hydrogenation performance:

[0046] The 2g of prepared alkaline earth metal modified copper-based catalyst was loaded into a fixed bed, and a mixed gas of carbon dioxide and hydrogen was passed in, the mixed gas containing 4% argon by volume as an internal standard for calculating conversion rate and selectivity, the volume ratio of carbon dioxide and hydrogen in the mixed gas being 1:3, continuous reaction was carried out under the reaction conditions of 160°C, 50bar and 40mL / min, and the reaction tail gas was analyzed on-line after passing through a full-heat needle valve and a heated pipeline into a gas chromatograph. After 5h of reaction, the carbon dioxide conversion rate was as high as 6.2%, and the methanol selectivity was as high as 93%.

[0047] Figure 1 The XRD pattern of the copper-based catalyst according to Example 1 of the present application.

[0048] Figure 2 The catalytic performance graph of the copper-based catalyst according to Example 1 of the present application.

[0049] Example 2

[0050] The difference from Example 1 is that the proportion of catalyst raw materials is adjusted to be 0.2g of strontium acetate, 15mmol of copper acetate monohydrate, 5mmol of zinc acetate dihydrate, 5mmol of zirconium acetate and 100mmol of anhydrous oxalic acid mixed.

[0051] The carbon dioxide hydrogenation performance test was performed on the prepared alkaline earth metal modified copper-based catalyst:

[0052] The 2g of prepared alkaline earth metal modified copper-based catalyst was loaded into a fixed bed, and a mixed gas of carbon dioxide and hydrogen was passed in, the mixed gas containing 4% argon by volume as an internal standard for calculating conversion rate and selectivity, the volume ratio of carbon dioxide and hydrogen in the mixed gas being 1:3, continuous reaction was carried out under the reaction conditions of 160°C, 50bar and 40mL / min, and the reaction tail gas was analyzed on-line after passing through a full-heat needle valve and a heated pipeline into a gas chromatograph. After 5h of reaction, the carbon dioxide conversion rate was as high as 6.2%, and the methanol selectivity was as high as 93%.

[0053] Figure 3 The XRD pattern of the copper-based catalyst according to Example 2 of the present application.

[0054] Figure 4 The catalytic performance graph of the copper-based catalyst according to Example 2 of the present application.

[0055] Example 3

[0056] The difference from Example 1 is that the proportion of catalyst raw materials is adjusted to be 0.2g of strontium acetate, 15mmol of copper acetate monohydrate, 5mmol of zinc acetate dihydrate, 5mmol of zirconium acetate and 100mmol of anhydrous oxalic acid mixed.

[0057] The prepared alkaline earth metal modified copper-based catalyst was subjected to carbon dioxide hydrogenation performance test:

[0058] The prepared 2 g of alkaline earth metal modified copper-based catalyst was loaded into a fixed bed, and a mixed gas of carbon dioxide and hydrogen was introduced, the mixed gas containing 4% argon by volume as an internal standard for calculating conversion rate and selectivity, the volume ratio of carbon dioxide and hydrogen in the mixed gas being 1:3, and the reaction being carried out continuously under the reaction conditions of 160°C, 50 bar and 40 mL / min, and the reaction tail gas was introduced into a gas chromatograph after passing through a full-heat needle valve and a heated pipeline for online analysis. After 5 h of reaction, the carbon dioxide conversion rate was as high as 5.9%, and the methanol selectivity was as high as 92%.

[0059] Figure 5 The XRD pattern of the copper-based catalyst according to Example 3 of the present application.

[0060] Figure 6 The catalytic performance graph of the copper-based catalyst according to Example 3 of the present application.

[0061] Comparative Example 1

[0062] An alkaline earth metal unmodified copper-based catalyst was prepared, and the preparation method was as follows:

[0063] First, 10 mmol of copper acetate monohydrate, 4 mmol of zinc acetate dihydrate, 4 mmol of zirconium acetate and 80 mmol of anhydrous oxalic acid were mixed at room temperature, the mixture was thoroughly ground at room temperature, and then the mixture was heated to 120°C at a heating rate of 10°C / min in an oven and dried for 12 h, and then the obtained product was heated to 400°C at a heating rate of 5°C / min in a muffle furnace and kept for 3 h, and after natural cooling to room temperature, the product was obtained.

[0064] The prepared 2 g of alkaline earth metal unmodified copper-based catalyst was loaded into a fixed bed, and a mixed gas of carbon dioxide and hydrogen was introduced, the mixed gas containing 4% argon by volume as an internal standard for calculating conversion rate and selectivity, the volume ratio of carbon dioxide and hydrogen in the mixed gas being 1:3, and the reaction being carried out continuously under the reaction conditions of 160°C, 50 bar and 40 mL / min, and the reaction tail gas was introduced into a gas chromatograph after passing through a full-heat needle valve and a heated pipeline for online analysis. After 5 h of reaction, the carbon dioxide conversion rate was as high as 5.9%, and the methanol selectivity was as high as 92%.

[0065] Figure 7 The XRD pattern of the copper-based catalyst according to Comparative Example 1 of the present application.

[0066] Figure 8The catalytic performance graph of the copper-based catalyst according to the present application Comparative Example 1.

[0067] Comparative Example 2

[0068] A conventional coprecipitated CuZnZr catalyst was prepared according to the following method:

[0069] First, 10 mmol of copper acetate monohydrate, 4 mmol of zinc acetate dihydrate and 4 mmol of zirconium acetate were dissolved in 50 mL of deionized water, 80 mmol of anhydrous oxalic acid was dissolved in 50 mL of deionized water, and then the two solutions were added dropwise into 50 mL of deionized water at 65°C, and the pH was maintained at 7 during the dropwise addition. The obtained suspension was then aged for 2 h, after which it was filtered and washed with deionized water. The obtained product was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 350°C at a temperature increase rate of 5°C / min for 4 h, and the product was obtained after natural cooling.

[0070] The prepared 2 g of coprecipitated CuZnZr catalyst was loaded into a fixed bed, and a mixed gas of carbon dioxide and hydrogen was introduced, the mixed gas containing 4% argon by volume as an internal standard for calculating the conversion rate and selectivity, the volume ratio of carbon dioxide and hydrogen in the mixed gas being 1:3, and the reaction was carried out continuously under the reaction conditions of 160°C, 50 bar and 40 mL / min, and the tail gas was introduced into a gas chromatograph after passing through a full-heat needle valve and a heated pipeline for online analysis. After 5 h of reaction, the carbon dioxide conversion rate reached 3%, and the methanol selectivity reached 85%.

[0071] Figure 9 The XRD pattern of the copper-based catalyst according to the present application Comparative Example 2.

[0072] Figure 10 The catalytic performance graph of the copper-based catalyst according to the present application Comparative Example 2.

[0073] The catalyst provided by the above embodiments of the present application has excellent performance, good catalytic activity, high selectivity of target products, and has industrial application prospects when applied to the preparation of methanol by carbon dioxide hydrogenation.

[0074] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. Use of an alkaline earth metal-modified copper-based catalyst, characterized in that: The copper-based catalyst is used in a reaction of CO2 hydrogenation to prepare methanol; The raw materials for preparing the copper-based catalyst are strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid, and the ratio is (0.1~0.2)g :(5~15)mmol :(2~5)mmol :(2~5)mmol :(40~100)mmol; The preparation method of the copper-based catalyst comprises the following steps: The strontium acetate, copper acetate monohydrate, zinc acetate dihydrate, zirconium acetate and anhydrous oxalic acid are mixed by grinding at room temperature, and then heated at a constant speed to a first temperature for a second time, to obtain a second mixture; The second mixture is heated at a constant speed to a second temperature for a period of time, and then naturally cooled to obtain the alkaline earth metal modified copper-based catalyst; The first temperature is 100~140℃, and the second temperature is 350~450℃.

2. Use of an alkaline earth modified copper-based catalyst according to claim 1, characterized in that: The heating rate for heating at a constant speed to the first temperature is 5℃ / min~15℃ / min, and the heating rate for heating at a constant speed to the second temperature is 5℃ / min~15℃ / min.

3. Use of an alkaline earth modified copper-based catalyst according to claim 1, characterized in that: The holding time for heating to the first temperature is 10h~14h, and the holding time for heating to the second temperature is 2h~4h.

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