Carbon dioxide catalytic reduction method

Abstract

The invention discloses a carbon dioxide catalytic reduction method which comprises the following steps: in a fixed bed reactor, controlling the flow rate of introduced reaction gas to be H2 / CO2 in a volume ratio of (2-4): 1, and carrying out catalytic reaction under the condition of a catalyst under the reaction conditions that the reaction pressure is 30-50 bar and the reaction temperature is 200-250 DEG C, and the mass space velocity of the reaction is 5000-20000 mL / gcat / h. The method is high in stability, good in methanol selectivity, simple in preparation process, low in cost and beneficial to large-scale popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dioxide catalysis, and in particular relates to a method for catalytic reduction of carbon dioxide. Background Art

[0002] CO 2 Converting it into high-value-added chemicals and fuels can not only solve the problem of excessive CO 2 It can not only solve environmental problems such as global warming caused by carbon dioxide emissions, but also effectively alleviate the problem of excessive dependence on fossil fuels. Among them, methanol, as an ideal low-carbon clean fuel, can replace oil and gas, which helps to solve the problem of carbon emissions in transportation; as an intermediate, it is widely used in basic industries such as chemical industry and material synthesis, which can promote green manufacturing; as an excellent hydrogen storage material, it can alleviate the problems of hydrogen energy storage and transportation safety and cost. Therefore, green hydrogen produced by renewable energy can convert CO 2 Converting it into high value-added methanol can not only solve the problem of energy storage and transportation, but also neutralize CO 2 , realizing the recycling of carbon.

[0003] Among them, Cu-based catalysts are the most widely used, which is attributed to their high reaction activity and methanol space-time yield. However, the poor water resistance of traditional Cu-based catalysts leads to easy sintering of active sites, which seriously affects the stability of their catalytic activity. 2 The core part of the hydrogenation reaction system still has some problems, such as the catalyst itself for CO 2 The catalytic conversion efficiency is low, and it is difficult to maintain long-term stability under high temperature and high pressure reaction conditions; some existing catalyst raw materials are expensive, and the preparation process is cumbersome and time-consuming.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a method for catalytic reduction of carbon dioxide.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a method for catalytic reduction of carbon dioxide.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A method for catalytic reduction of carbon dioxide, comprising:

[0009] In the fixed bed reactor, the flow rate of the reaction gas is controlled to be H 2 With CO2 The volume ratio of (2-4): 1, under the catalyst conditions, the catalytic reaction is carried out under the reaction conditions of reaction pressure 30-50 bar, reaction temperature 200-250°C, and the mass space velocity of the reaction is 5000-20000 mL / gcat / h.

[0010] In one or more embodiments of the present invention, the catalyst is obtained by loading appropriate amounts of Au and Cu elements on a carrier activated by sintering under oxidative conditions, wherein the molar ratio of Au to Cu elements is (3-5):(7-5).

[0011] In one or more embodiments of the present invention, the oxidative condition is an air environment or a pure oxygen environment.

[0012] In one or more embodiments of the present invention, the sintering activation is calcining at 300-600° C. for 1-2 hours.

[0013] In one or more embodiments of the present invention, the carrier is a ZnO microparticle carrier.

[0014] In one or more embodiments of the present invention, the raw material of the ZnO microparticle carrier is a precipitate obtained by reacting a zinc chloride solution under alkaline stirring conditions and then drying it.

[0015] In one or more embodiments of the present invention, the loading of Au and Cu elements is as follows: in an alkaline aqueous system in which a carrier is dispersed, an appropriate amount of 1M HAuCl 4 and 1M Cu(NO 3 ) 2 , adjusting the pH to 7 with 1M NaOH solution, stirring and separating the precipitate, and subjecting the precipitate to hydrogen reduction treatment to obtain the product.

[0016] In one or more embodiments of the present invention, the alkaline aqueous system is an aqueous solution adjusted to a pH of 8 to 9 with aqueous ammonia.

[0017] In one or more embodiments of the present invention, the dripping speed is 3-5 drops / s.

[0018] In one or more embodiments of the present invention, the hydrogen reduction treatment is performed under a gas flow of hydrogen and nitrogen.

[0019] Compared with the prior art, the carbon dioxide catalytic reduction method of the present invention has strong stability, good methanol selectivity, simple preparation process, low cost, and is conducive to large-scale promotion and application. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] Including but not limited to the following examples, the detection of the reaction product adopts: the gas component after the catalyst reaction is qualitatively / quantitatively analyzed by online gas chromatography (Shimadzu, GC-2014AT, detector: thermal conductivity detector (TCD)) and hydrogen flame ionization detector (FID) (Shimadzu, GC-2014AF). The liquid component after the catalyst reaction is also qualitatively / quantitatively analyzed by offline gas chromatography (Shimadzu, GC-2014AF, detector: hydrogen flame ionization detector (FID)).

[0022] Example 1

[0023] The catalytic reduction method of carbon dioxide in this embodiment includes: in a fixed bed reactor, controlling the flow rate of the reaction gas introduced to be H 2 With CO 2 The volume ratio is 2:1, and under the catalyst conditions, the catalytic reaction is carried out under the reaction conditions of reaction pressure 30 bar and reaction temperature 200°C, and the mass space velocity of the reaction is 5000 mL / gcat / h.

[0024] The catalyst is a 3 mm spherical ZnO carrier sintered at 300°C for 2 hours in the presence of air, 50 mL of water is added to 1.0 g of the sintered ZnO to disperse it evenly to form a suspension, and the suspension is adjusted to pH 8 using 1 M ammonia water; HAuCl with a molar ratio of 66:34 is added to the suspension at a rate of 3 drops / s under continuous stirring at a liquid temperature of 60°C. 4 and Cu(NO 3 ) 2 , until the total mass of Au and Cu reaches 1.31wt% of the carrier mass; after the dropwise addition is completed, the pH is adjusted to 7 with 1M NaOH solution, the liquid temperature is maintained at 60°C, stirring is continued for 3 hours, and then, cooled to room temperature, the precipitate is filtered, washed with deionized water, and then dried at 80°C overnight; and then hydrogen reduction treatment is performed at 300°C, the hydrogen reduction treatment is performed under a gas flow of hydrogen and nitrogen, wherein the volume ratio of hydrogen to nitrogen is 1:4, and the gas flow rate is 100mL / min.

[0025] After testing, the methanol selectivity was 70% and the carbon dioxide conversion rate was 83%.

[0026] Example 2

[0027] The difference between this embodiment and embodiment 1 is that the flow rate of the reaction gas introduced is H 2 With CO 2 The volume ratio is 3:1, and under the catalyst conditions, the catalytic reaction is carried out under the reaction conditions of reaction pressure 40 bar and reaction temperature 220°C, and the mass space velocity of the reaction is 10000 mL / gcat / h.

[0028] After testing, the methanol selectivity was 72% and the carbon dioxide conversion rate was 88%.

[0029] Example 3

[0030] The difference between this embodiment and embodiment 1 is that the flow rate of the reaction gas introduced is H 2 With CO 2 The volume ratio is 4:1. Under the catalyst conditions, the catalytic reaction is carried out under the reaction conditions of reaction pressure 50 bar and reaction temperature 250°C, and the mass space velocity of the reaction is 20000 mL / gcat / h.

[0031] After testing, the methanol selectivity was 68% and the carbon dioxide conversion rate was 85%.

[0032] The only difference between Examples 4-6 and Examples 1-3 is that the ZnO carrier is 1M zinc chloride solution, which is fully reacted under the stirring of 1000 rpm with the addition of excess ammonia solution, and the precipitate obtained by filtration is dried at 100° C. When possible, since the optimized carrier has more active centers, higher selectivity and lower side reactions are achieved.

[0033] The test results of Example 4 showed that the methanol selectivity was 81% and the carbon dioxide conversion rate was 89%.

[0034] The test results of Example 5 showed that the methanol selectivity was 83% and the carbon dioxide conversion rate was 88%.

[0035] The test results of Example 6 showed that the methanol selectivity was 80% and the carbon dioxide conversion rate was 91%.

[0036] Example 7

[0037] The difference between this embodiment and embodiment 5 is that the molar ratio of HAuCl is 3:7. 4 and Cu(NO 3 ) 2 . According to the test, the methanol selectivity is 80% and the carbon dioxide conversion rate is 92%.

[0038] Example 8

[0039] The difference between this embodiment and embodiment 5 is that the molar ratio of HAuCl is 5:5 4 and Cu(NO 3 ) 2 . According to the test, the methanol selectivity is 81% and the carbon dioxide conversion rate is 87%.

[0040] Example 9

[0041] The difference between this embodiment and embodiment 5 is that the catalyst is sintered at 300° C. for 2 hours under pure oxygen. According to the test, the methanol selectivity is 85% and the carbon dioxide conversion rate is 89%.

[0042] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0043] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for catalytic reduction of carbon dioxide, characterized in that: include: In a fixed bed reactor, the flow rate of the reaction gas introduced is controlled to be a volume ratio of H2 to CO2 (2-4):

1. Under catalyst conditions, the catalytic reaction is carried out under the reaction conditions of reaction pressure 30-50 bar and reaction temperature 200-250°C, and the mass space velocity of the reaction is 5000-20000 mL / gcat / h.

2. The method for catalytic reduction of carbon dioxide according to claim 1, characterized in that: The catalyst is obtained by loading appropriate amounts of Au and Cu elements on a carrier activated by sintering under oxidative conditions, wherein the molar ratio of Au to Cu elements is (3-5):(7-5).

3. The method for catalytic reduction of carbon dioxide according to claim 2, characterized in that: The oxidative condition is an air environment or a pure oxygen environment.

4. The method for catalytic reduction of carbon dioxide according to claim 2, characterized in that: The sintering activation is performed by calcining at 300-600° C. for 1-2 hours.

5. The method for catalytic reduction of carbon dioxide according to claim 2, characterized in that: The carrier is a ZnO microparticle carrier.

6. The method for catalytic reduction of carbon dioxide according to claim 5, characterized in that: The raw material of the ZnO microparticle carrier is a precipitate obtained by reacting a zinc chloride solution under alkaline stirring conditions and then drying it.

7. The method for catalytic reduction of carbon dioxide according to claim 1, characterized in that: The Au and Cu elements are loaded by dropping appropriate amounts of 1M HAuCl4 and 1M Cu(NO3)2 into an alkaline aqueous system in which a carrier is dispersed, adjusting the pH to 7 with 1M NaOH solution, stirring and separating the precipitate, and subjecting the precipitate to hydrogen reduction treatment.

8. The method for catalytic reduction of carbon dioxide according to claim 7, characterized in that: The alkaline aqueous system is an aqueous solution adjusted to a pH of 8 to 9 by using aqueous ammonia.

9. The method for catalytic reduction of carbon dioxide according to claim 7, characterized in that: The dropping speed is 3-5 drops / s.

10. The method for catalytic reduction of carbon dioxide according to claim 7, characterized in that: The hydrogen reduction treatment is performed under a gas flow of hydrogen and nitrogen.