Method for deeply converting CO2 into acetaldehyde and crotonaldehyde

Abstract

The invention discloses a method for deeply converting CO2 into acetaldehyde and crotonaldehyde, and belongs to the technical field of conversion of acetaldehyde and crotonaldehyde, and the method comprises the following steps: S1, taking one or a mixture of more of melamine, urea and dicyandiamide as a precursor, dissolving the precursor in an aqueous solution under a heating condition, and uniformly stirring until the precursor is completely dissolved; s2, adding one or more of deprotonation agents including triethylamine, isopropanolamine, 1-methylimidazole, n-butylamine, pyridine and tetramethylammonium hydroxide, mixing, and uniformly stirring; s3, placing in a hydrothermal reaction kettle, reacting under given temperature and time conditions, and cooling to room temperature; s4, carrying out centrifugal washing, drying and calcining to obtain polymeric carbon nitride with a crystal / amorphous interlaced interface; according to the method, other hydrogenation steps of the intermediate in the CO2 conversion process are inhibited, and on the basis of high yield and selectivity of acetaldehyde, C-C chain growth is further carried out to generate crotonaldehyde.

Description

Technical Field

[0001] This invention relates to the field of acetaldehyde and crotonaldehyde conversion technology, and more particularly to a method for the deep conversion of CO2 into acetaldehyde and crotonaldehyde. Background Technology

[0002] Solar-driven catalytic remodeling of carbon dioxide (CO2) into high-value-added chemicals is of great significance for mitigating the greenhouse effect and developing renewable energy. However, the highest oxidation state of carbon (C2) is crucial for the chemical production of these chemicals. 4+ The CO2 molecule possesses strong thermodynamic stability and kinetic inertness, and its chemical bond activation requires overcoming the energy barrier of multiple electron-proton cooperative transfer. Furthermore, depending on the change in the valence state of the carbon center and the degree of energy accumulation, it tends to generate single-carbon products via the 2-8 electron transfer pathway, such as carbon monoxide (CO), methane (CH4), methanol (CH3OH), and formic acid (HCOOH). Therefore, how to control the reduction of CO2 to high-value-added multi-carbon products, such as C2 (acetaldehyde, CH3CHO) and C4 (crotonaldehyde, CH3CH=CHCHO), through C-C coupling is a major challenge in solving the utilization of CO2 resources.

[0003] The photocatalytic reduction of CO2 to CH3CHO and further to CH3CH=CHCHO involves a multi-step cascade reaction, with the core challenge being the regulation of complex electron transport pathways. The photocatalytic conversion of CO2 to CH3CHO is a ten-electron transfer process involving multiple hydrogenation steps, resulting in low yields and selectivity of CH3CHO. Furthermore, the subsequent CC-coupling process for preparing CH3CH=CHCHO from the generated CH3CHO requires overcoming the kinetic barrier of C=C bond formation. Therefore, regulating electron transport pathways to suppress other hydrogenation steps, thereby improving the efficiency of photocatalytic CO2 conversion to CH3CHO, and further converting CH3CHO to CH3CH=CHCHO via CC-coupling, is an extremely challenging task. Summary of the Invention

[0004] The present invention aims to provide a method for the deep conversion of CO2 into acetaldehyde and crotonaldehyde, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for the deep conversion of CO2 into acetaldehyde and crotonaldehyde, comprising the following steps:

[0007] S1. Dissolve the precursor in an aqueous solution under heating conditions and stir until completely dissolved;

[0008] S2. Add the deprotonating agent and stir well;

[0009] S3. Place in a hydrothermal reactor and react under given temperature and time conditions, then cool to room temperature; this can be extended to microwave hydrothermal reaction.

[0010] S4. After centrifugation, washing, drying and calcination, polymeric carbon nitride with a crystalline / amorphous interlocking interface is obtained.

[0011] Preferably, the precursor in step S1 includes one or more of melamine, urea, and dicyandiamide.

[0012] Preferably, the deprotonating agent in step S2 includes one or more of triethylamine, isopropanolamine, 1-methylimidazole, n-butylamine, pyridine, and tetramethylammonium hydroxide.

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

[0014] This invention prepares a polymeric carbon nitride with a crystalline / amorphous interfacial interface by introducing one or more of the deprotonating agents triethylamine, isopropanolamine, 1-methylimidazole, n-butylamine, pyridine, and tetramethylammonium hydroxide, thereby regulating the polycondensation kinetics of the polymeric carbon nitride precursor by utilizing intermolecular deprotonation, and controlling the temperature or time of hydrothermal treatment to regulate the crystallization process of the precursor.

[0015] This invention constructs a crystalline / amorphous interleaved interface to utilize the strong electronic coupling between the interfaces, photo-excited electrons transfer from the crystalline phase to the amorphous phase, and the amorphous phase provides effective active sites for the activation and conversion of CO2, which can inhibit other hydrogenation steps of the intermediate and improve the yield of acetaldehyde. Based on the high yield and selectivity of acetaldehyde, CC chain growth further occurs to produce crotonaldehyde. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for the deep conversion of CO2 into acetaldehyde and crotonaldehyde.

[0017] Figure 2 XRD patterns for CN, HTCN, and HTCN-xTEA;

[0018] Figure 3 SEM image of HTCN-0.2TEA;

[0019] Figure 4 TEM image of HTCN-0.2TEA;

[0020] Figure 5 Chromatograms of the photocatalytic CO2 reduction products after 7 h of reaction with HTCN-0.2TEA, as well as acetaldehyde and crotonaldehyde standards;

[0021] Figure 6Gas chromatography-mass spectra of the photocatalytic CO2 reduction products after 7 h of reaction with HTCN-0.2TEA;

[0022] Figure 7 Performance graphs of photocatalytic CO2 reduction to CH3CHO using CN, HTCN, and HTCN-xTEA;

[0023] Figure 8 The yield diagram shows the photocatalytic CO2 reduction to CH3CHO produced by the reaction of CN, HTCN, and HTCN-0.2TEA for 7 h.

[0024] Figure 9 Performance graphs of photocatalytic CO2 reduction to CH3CH=CHCHO using CN, HTCN, and HTCN-0.2TEA;

[0025] Figure 10 The yield graphs for the photocatalytic CO2 reduction to CH3CH=CHCHO produced by the reaction of CN, HTCN, and HTCN-xTEA for 7 h are shown.

[0026] Figure 11 The yield graphs show the photocatalytic CO2 reduction products after 7 h of reaction under different control conditions. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0028] like Figure 1 The method shown is a deep conversion of CO2 into acetaldehyde and crotonaldehyde. The specific operation steps are as follows:

[0029] S1. Using one or more of melamine, urea, and dicyandiamide as precursors, the precursors are dissolved in an aqueous solution under heating conditions and stirred until completely dissolved.

[0030] S2. Add one or more of the following: triethylamine (TEA), isopropanolamine, 1-methylimidazole, n-butylamine, pyridine, and tetramethylammonium hydroxide; and stir until homogeneous.

[0031] S3. Place in a hydrothermal reactor and react under given temperature and time conditions, then cool to room temperature;

[0032] S4. After centrifugation, washing, drying and calcination, polymeric carbon nitride with a crystalline / amorphous interlocking interface is obtained. Figure 2 , Figure 3 and Figure 4 The successful preparation of polymeric carbon nitride at crystalline / amorphous interfacial interfaces was confirmed.

[0033] The hydrothermal reaction temperature (150 ~ 220 ℃), reaction time (8 ~ 14 h), type of deprotonating agent (triethylamine, isopropanolamine, 1-methylimidazole, n-butylamine, pyridine, tetramethylammonium hydroxide) and dosage (0.1 ~ 3 mL) are the influencing factors for the preparation of polymeric carbon nitride with crystalline / amorphous interfacial interfaces.

[0034] The photocatalytic CO2 conversion performance of polymeric carbon nitride at crystalline / amorphous interfacial interfaces was tested using a multi-channel photocatalytic reaction system. The results were obtained by gas chromatography (GC). Figure 5 ) and gas chromatography-mass spectrometry (GC-MS) Figure 6 This confirmed that the two products produced were acetaldehyde (CH3CHO) and crotonaldehyde (CH3CH=CHCHO).

[0035] like Figure 7 As shown, after 7 h of reaction, the amount of CH3CHO produced by the polymeric carbon nitride at the crystalline / amorphous interfacial interface reached 10651 μmol g. -1 It was without the deprotonating agent HTCN (7942 μmol g). -l It is 1.34 times that of traditionally high-temperature carbon nitride (CN) produced at 1335 μmol g. -l 7.98 times that of )

[0036] like Figure 8 As shown, the yield of CH3CHO after 7 h of reaction was further calculated (HTCN-0.2TEA ~ 1522 μmol g). -l h -l HTCN ~ 1135 μmol g -l h -l CN ~ 191 μmol g -l h -l This is due to the fact that the crystalline / amorphous interfacial region promotes the formation of CH3CHO;

[0037] like Figure 9 As shown, after 4 hours of reaction, the amount of CH3CHO produced by the photocatalytic CO2 generation of HTCN-0.2TEA reached as high as 8672 μmolg. -l The reaction system initially produced CH3CH=CHCHO. After 7 hours of reaction, the amount of CH3CH=CHCHO produced by the HTCN-0.2TEA photocatalytic CO2 production reached 709 μmol g. -l It is HTCN (402 μmol g) -l The yield was 1.76 times that of the target; furthermore, HTCN-0.2TEA exhibited the highest CH3CH=CHCHO yield (101 μmol g) during the photocatalytic CO2 reaction after 7 h. -1 h-1 )(like Figure 10 (as shown)

[0038] Preliminary speculation suggests that CH3CH=CHCHO is a further transformation of CH3CHO via CC coupling. Notably, analysis of the post-reaction gases revealed no generation of typical gaseous products CO and CH4 during photocatalytic CO2 reduction, and only a small amount of CH3OH was detected in the liquid phase products. This indicates that the polymeric carbon nitride HTCN-0.2TEA with a crystalline / amorphous interfacial structure prepared by the method of this invention inhibits other hydrogenation steps of CO2 during photocatalytic reduction.

[0039] The photocatalytic CO2 reduction performance was tested under different reaction conditions, such as... Figure 11 As shown, no CH3CHO and CH3CH=CHCHO were observed under reaction conditions 2, 3, 4, 5 and 6, indicating that the carbon source came from the raw gas CO2, the HTCN-0.2TEA catalyst, CO2 gas, light source, triethanolamine (TEOA) and H2O were the necessary conditions for the reaction to occur.

[0040] In summary, the polymeric carbon nitride HTCN-0.2TEA with a crystalline / amorphous interfacial structure prepared by the method of this invention exhibits excellent photocatalytic activity for the generation of CH3CHO and CH3CH=CHCHO.

[0041] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A process for the deep conversion of CO2 to acetaldehyde and crotonaldehyde, characterized in that: The implementation of the method comprises: S1, dissolving the precursor in aqueous solution under heating condition, stirring uniformly until completely dissolved; S2, adding deprotonating agent, stirring uniformly; S3, placing in hydrothermal reaction kettle, reacting under given temperature and time condition, cooling to room temperature; can be extended to microwave hydrothermal reaction; S4, obtaining polymeric carbon nitride with crystalline / amorphous staggered interface after centrifugal washing, drying and calcination.

2. A process for the deep conversion of CO2 to acetaldehyde and crotonaldehyde according to claim 1, characterized in that: The precursor in the step S1 comprises one or more of melamine, urea, dicyandiamide.

3. A process for the deep conversion of CO2 to acetaldehyde and crotonaldehyde according to claim 1, characterized in that: The deprotonating agent in the step S2 comprises one or more of triethylamine, isopropanolamine, 1-methylimidazole, n-butylamine, pyridine, tetramethylammonium hydroxide.

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