Heterojunction photocatalyst for catalyzing decarboxylation of fatty acids to produce aldehydes, preparation method and application thereof

Abstract

The present invention relates to a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, and a preparation method and application thereof. The heterojunction photocatalyst is: (i) anatase-type titanium dioxide; or (ii) anatase-type titanium dioxide as a carrier, with Bi 2 O 3 、CeO 2 , ZnO, NiO as the active component of the catalyst. These catalysts can photocatalyze the removal of a carboxyl group from carboxylic acid and convert it into aldehyde at room temperature and pressure, with low energy consumption and low equipment requirements.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, a preparation method and an application thereof. Background Art

[0002] Fatty aldehydes are widely present in active natural products and drug molecules, and are also important intermediates in organic synthesis. When synthesizing complex drug molecules, the functional groups of fatty aldehydes (such as aldehyde groups) can react with other functional groups to form new chemical bonds and molecular structures. This ability to construct complex molecules makes fatty aldehydes particularly important in the synthesis of drugs with special pharmacological effects.

[0003] Bio-derived fatty acids are widely found in nature as low-value byproducts of oil processing and pulping industries. They are not edible but are abundant and inexpensive. Using them to produce high-value-added chemicals, such as long-chain fatty aldehydes, is not only cost-effective but also of great theoretical and applied value. However, this transformation process faces major challenges in terms of activity and selectivity, because the synthesis methods of fatty aldehydes can be roughly divided into two categories: dehydration and hydroformylation. The first method involves the dehydration of fatty alcohols; the second method is the hydroformylation of olefins, which are mainly derived from crude oil and are often used to produce short-chain aldehydes. Both methods use fossil feedstocks and are carried out at high temperatures up to 500°C and high pressures up to 600 bar.

[0004] In the prior art, tin or platinum group elements are loaded on oxide carriers such as aluminum oxide, zirconium oxide, iron oxide, titanium oxide, and yttrium oxide to prepare catalysts. Such catalysts catalyze the hydrogenation of carboxylic acids or their derivatives in the gas phase at high temperature to prepare aldehydes. These methods have high energy consumption. Summary of the invention

[0005] The invention provides a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, and a preparation method and application thereof, so as to solve the problems of high energy consumption and high equipment requirements when the existing catalyst catalyzes the hydrogenation of carboxylic acids or their derivatives to produce aldehydes.

[0006] The technical solution provided by the present invention is as follows:

[0007] The first aspect of the present invention provides a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, wherein the heterojunction photocatalyst is:

[0008] (i) anatase titanium dioxide; or,

[0009] (ii) A catalyst with anatase titanium dioxide as a carrier and one of Bi2O3, CeO2, ZnO, and NiO as an active component.

[0010] The applicant has found that anatase titanium dioxide (TiO2) can photocatalyze carboxylic acids to remove a carboxyl group and convert them into aldehydes in a normal temperature atmospheric environment. When bismuth oxide (Bi2O3) is loaded on anatase titanium dioxide, the yield of the target aldehyde and the conversion rate of carboxylic acid are greatly improved. After CeO2, ZnO, and NiO are loaded on anatase titanium dioxide, although the yield of the target aldehyde and the conversion rate of carboxylic acid decrease, it still has the ability to photocatalyze carboxylic acids to remove a carboxyl group and convert them into aldehydes. These catalysts can photocatalyze carboxylic acids to remove a carboxyl group and convert them into aldehydes in a normal temperature and air environment, with low energy consumption and low equipment requirements.

[0011] Preferably, the heterojunction photocatalyst is a catalyst with anatase titanium dioxide as a carrier and Bi2O3 as an active component. Preferably, Bi2O3 is α-Bi2O3 nanocrystals. Bi2O3 has an enhancing effect on the ability of anatase titanium dioxide to catalyze the removal of a carboxyl group from carboxylic acid and convert it into aldehyde.

[0012] In combination with the first aspect of the present invention, in some embodiments, the proportion of active components in the catalyst is 0.1wt%~10wt%; preferably, the proportion of active components in the catalyst is 0.1wt%~5wt%; further, the proportion of active components in the catalyst is 3wt%~7wt%; further, the proportion of active components in the catalyst is 4wt%~6wt%; optimally, the proportion of active components in the catalyst is 5wt%.

[0013] When the content of the active component is within the above range, the catalyst can have the ability to catalyze the decarboxylation of carboxylic acids into aldehydes. When the proportion of the active component in the catalyst is too high, the active component will block the active sites on the anatase titanium dioxide, hindering the catalytic effect of the anatase titanium dioxide on carboxylic acids.

[0014] In conjunction with the first aspect of the present invention, in some embodiments, the heterojunction photocatalyst is in the shape of a sea urchin, and the sea urchin-shaped structure can provide more photocatalytic active sites and a high surface area. The particle size of the heterojunction photocatalyst is 0.1 to 2 microns, which can provide a higher specific surface area and increase the contact probability between the active sites and the raw materials.

[0015] The second aspect of the present invention provides the use of a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes in photocatalyzing the decarboxylation of fatty acids or their derivatives to produce aldehydes.

[0016] The heterojunction photocatalyst of the present invention can catalyze carboxylic acid to remove a carboxyl group and convert it into aldehyde under normal temperature, air and light conditions, with low energy consumption and low equipment requirements. It is expected to replace the catalyst in the prior art that can only catalyze carboxylic acid to produce aldehyde under high temperature and high pressure.

[0017] The third aspect of the present invention provides a method for preparing a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, comprising:

[0018] The anatase titanium dioxide is mixed with the precursor of the active component and then fully ground; the active component is one of Bi2O3, CeO2, ZnO, and NiO; the precursor of the active component is nitrate or chloride;

[0019] The ground material is fully calcined in an oxygen atmosphere at 400-650° C., and the calcined product is cooled to room temperature to obtain a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes.

[0020] The preparation method mixes anatase titanium dioxide with a precursor of an active component, and then calcines the precursor of the active component into a metal oxide, thereby evenly dispersing the active component on a carrier and forming a pn heterojunction during the calcination process, thereby improving the photocatalytic activity of the catalyst.

[0021] In conjunction with the third aspect of the present invention, in some embodiments, the precursor of Bi2O3 is Bi(NO3)3·5H2O, the precursor of CeO2 is Ce(NO3)2, the precursor of ZnO is Zn(NO3)2, and the precursor of NiO is NiCl2. These precursors are easily calcined into metal oxides in an oxygen atmosphere at 400-650°C.

[0022] A fourth aspect of the present invention provides a method for photocatalytic decarboxylation of fatty acids or their derivatives to produce aldehydes, comprising:

[0023] Carboxylic acid or its derivative, a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, and an organic solvent are placed in a photoreactor;

[0024] The reaction is stirred at room temperature and pressure under ultraviolet light to obtain aldehyde.

[0025] In the method for preparing aldehyde of the present invention, at room temperature and pressure and under ultraviolet light irradiation, the above-mentioned heterojunction photocatalyst can be used to remove a carboxyl group from carboxylic acid and convert it into aldehyde, without the need for high temperature and high pressure conditions, thus saving equipment cost and energy consumption.

[0026] In conjunction with the fourth aspect of the present invention, in some embodiments, the carboxylic acid is a carboxylic acid having 2 to 18 carbon atoms. For example, the carboxylic acid is selected from one or more of stearic acid, palmitic acid, arachidic acid, myristic acid, and lauric acid.

[0027] In the process of preparing aldehydes according to the present invention, carboxylic acid removes a carboxyl group to form aldehydes, and therefore, the raw material should be a carboxylic acid having 2 or more carbon atoms.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The heterojunction photocatalyst provided by the present invention can remove a carboxyl group from carboxylic acid or its derivatives to prepare aldehydes under normal temperature and pressure and ultraviolet light irradiation, with low energy consumption and low requirements on equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 : Transmission electron microscopy images of Bi2O3 / TF; wherein, Figure (a), Figure (b), and Figure (c) represent transmission electron microscopy images at different magnifications, respectively.

[0032] Figure 2 : EDS element distribution and analysis diagram of Bi2O3 / TF; among them, Figure (a) is Ti, Figure (b) is O, and Figure (c) is Bi.

[0033] Figure 3 : XRD pattern of Bi2O3 / TF.

[0034] Figure 4 : Photocatalytic decarboxylation of stearic acid over different catalysts.

[0035] Figure 5 : Photocatalytic decarboxylation of stearic acid on Bi2O3 / TF with different loading amounts.

[0036] Figure 6 : Photocatalytic decarboxylation of stearic acid over different catalysts.

[0037] Figure 7 : Cyclic stability of 5wt% Bi2O3TF for stearic acid decarboxylation.

[0038] Figure 8 : (a) Active species capture experimental results; (b) EPR spectrum of DMPO-⋅O2. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution 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 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 are within the scope of protection of the present invention.

[0040] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0041] It should be noted that, in the description of this article, unless otherwise specified, "above", "below" are inclusive numbers, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0042] In the description of this specification, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0043] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation in the present invention. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each embodiment, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0044] Heterojunction Photocatalysts:

[0045] The heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes provided by the present invention is:

[0046] (i) anatase titanium dioxide; or,

[0047] (ii) A catalyst with anatase titanium dioxide as a carrier and one of Bi2O3, CeO2, ZnO, and NiO as an active component.

[0048] As in Example 8 and Figure 4 As shown, the present invention attempts to use the following catalysts for photocatalytic decarboxylation of stearic acid to produce aldehydes: pure anatase titanium dioxide (TF); with anatase titanium dioxide as a carrier: a catalyst with Bi2O3 as an active component (Bi2O3 / TF), a catalyst with CeO2 as an active component (CeO2 / TF), a catalyst with ZnO as an active component (ZnO / TF), a catalyst with NiO as an active component (NiO / TF), a catalyst with CoO as an active component (CoO / TF), and a catalyst with CuO as an active component. (CuO / TF), catalyst with Fe2O3 as active component (Fe2O3 / TF); It was found that TF, CeO2 / TF, ZnO / TF, NiO / TF, Bi2O3 / TF all have catalytic activity in photocatalytic conversion of fatty acids to fatty aldehydes, while CoO / TF, CuO / TF, and Fe2O3 / TF have poor or negligible conversion activity for stearic acid, indicating that not all metal oxides with semiconductor properties have the activity in photocatalytic removal of a carboxyl group from carboxylic acids to form aldehydes after combining with anatase titanium dioxide.

[0049] In some embodiments, the active component accounts for 0.1 wt% to 10 wt% of the catalyst; preferably, the active component accounts for 0.1 wt% to 5 wt% of the catalyst; further, the active component accounts for 3 wt% to 7 wt% of the catalyst; further, the active component accounts for 4 wt% to 6 wt% of the catalyst; optimally, the active component accounts for 5 wt% of the catalyst. Figure 5 As shown, the present invention tests the catalytic activity of Bi2O3 / TF with a Bi2O3 content of 0-10wt% in the photocatalytic preparation of fatty aldehydes from fatty acids. The catalyst with added Bi2O3 has higher catalytic activity than pure anatase titanium dioxide, and the yield of aldehydes is improved. However, when the Bi2O3 content exceeds 5wt%, the yield and conversion rate of aldehydes are significantly reduced. It is speculated that this is because excessive active components will block the active sites on the anatase titanium dioxide, hindering the catalytic effect of the anatase titanium dioxide on carboxylic acids.

[0050] In some embodiments, Bi2O3 is α-Bi2O3 nanocrystals. Figure 3 As shown, the Bi2O3 in the Bi2O3 / TF prepared by the present invention is α-Bi2O3 nanocrystals and the TiO2 is anatase titanium dioxide, indicating that the formation of α-Bi2O3 nanocrystals during the calcination process does not change the crystal structure of TiO2. Figure 3 No diffraction peaks corresponding to Bi2O3 are shown, which may be due to the high dispersity, low content and small size of α-Bi2O3 nanocrystals.

[0051] In some embodiments, the particle size of the heterojunction photocatalyst is 0.1-2 microns, preferably 1±0.5 microns. The smaller the catalyst particle size, the larger the specific surface area, and the higher the contact probability between the active site and the raw material.

[0052] Preparation method of heterojunction photocatalyst:

[0053] The present invention provides a method for preparing a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, comprising:

[0054] The anatase titanium dioxide is mixed with the precursor of the active component and then fully ground; the active component is one of Bi2O3, CeO2, ZnO, and NiO; the precursor of the active component is nitrate or chloride;

[0055] The ground material is fully calcined in an oxygen atmosphere at 400-650° C., and the calcined product is cooled to room temperature to obtain a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes.

[0056] In the preparation method of the present invention, the active component is formed in situ on the surface of anatase titanium dioxide, and an obvious pn heterojunction is formed between the two. Figure 6 As shown, the catalytic activity of 5wt% Bi2O3 / TF formed by the preparation method of the present invention in photocatalyzing the removal of a carboxyl group from carboxylic acid to form aldehyde is much higher than that of the physical mixture Bi2O3-TF of anatase titanium dioxide and α-Bi2O3, indicating that the pn heterojunction formed by α-Bi2O3 and anatase titanium dioxide formed during the calcination process can improve the catalytic activity of anatase titanium dioxide.

[0057] In some embodiments, the precursor of Bi2O3 is Bi(NO3)3·5H2O, the precursor of CeO2 is Ce(NO3)2, the precursor of ZnO is Zn(NO3)2, and the precursor of NiO is NiCl2. Nitrates and hydrochlorides are easily decomposed at high temperatures and easily oxidized to metal oxides in an air atmosphere. The present invention calcines a mixture of these precursors and anatase titanium dioxide to form metal oxides in situ on the surface of anatase titanium dioxide, and forms a pn heterojunction between these metal oxides and anatase titanium dioxide.

[0058] In addition, the preparation method starts from simple and easily available raw materials, does not go through the separation of intermediates, and performs multiple steps of reaction continuously, thus reducing the synthesis time and cost; the steps are simple and the operation is easy, which has dual benefits of being economical and environmentally friendly.

[0059] application:

[0060] As described above, the heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes provided by the present invention can photocatalyze the removal of a carboxyl group from carboxylic acids to form aldehydes. On this basis, those skilled in the art can predict that such catalysts can remove a carboxyl group or an ester group from carboxylic acid derivatives to form aldehydes. Therefore, the heterojunction photocatalyst is suitable for photocatalyzing the decarboxylation of fatty acids or their derivatives to produce aldehydes, and can solve the problems of high energy consumption and high equipment requirements in the existing technology of catalyzing the production of aldehydes from carboxylic acids.

[0061] The method for photocatalytic decarboxylation of fatty acids or their derivatives to produce aldehydes provided by the present invention comprises:

[0062] Carboxylic acid or its derivative, a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, and an organic solvent are placed in a photoreactor;

[0063] The reaction is stirred at room temperature and pressure under ultraviolet light to obtain aldehyde.

[0064] As shown in Example 8, the present invention places TF, CeO2 / TF, ZnO / TF, NiO / TF, Bi2O3 / TF and stearic acid at room temperature and pressure and ultraviolet light conditions, and reacts for 2 hours to obtain a high yield of aldehyde, which proves that these catalysts can photocatalyze the removal of a carboxyl group from carboxylic acid to prepare aldehyde. On this basis, those skilled in the art can optimize the reaction conditions to obtain a higher aldehyde yield and selectivity.

[0065] In some embodiments, the carboxylic acid is a carboxylic acid having 2 to 18 carbon atoms. For example, the carboxylic acid is selected from one or more of stearic acid, palmitic acid, arachidic acid, myristic acid, and lauric acid.

[0066] In some embodiments, the organic solvent is dodecane or acetonitrile.

[0067] Example

[0068] The technical scheme of the present invention is described in detail by way of examples below. If the manufacturer's brand or preparation method is not specified, the raw materials, equipment or solvents used are all common raw materials, equipment or solvents on the market. Unless otherwise specified, the raw materials of the same name used in the following examples and comparative examples are all the same raw materials.

[0069] Example 1: Preparation of Bi2O3 / TF photocatalyst (hereinafter referred to as Bi2O3 / TF)

[0070] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF (hereinafter referred to as TF).

[0071] (2) According to the mass fraction of Bi2O3 of 0, 2.5wt%, 5wt% and 10wt% of Bi2O3 / TF photocatalyst, 0.2g of TF synthesized in step (1) was mixed with the required mass of Bi(NO3)3·5H2O, and the mixed powder was fully ground at ambient temperature. Then, the ground powder was heated to 650℃ in a muffle furnace at a heating rate of 5℃ / min in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain Bi2O3 / TF photocatalyst, which was named TF, 2.5wt%Bi2O3 / TF, 5wt%Bi2O3 / TF and 10wt%Bi2O3 / TF respectively according to the mass fraction of Bi2O3 of 0, 2.5wt%, 5wt%Bi2O3 / TF and 10wt%Bi2O3 / TF.

[0072] Morphology test:

[0073] Figure 1 This is a transmission electron microscope image of the Bi2O3 / TF photocatalyst prepared in Example 1. The Bi2O3 / TF photocatalyst is in the shape of a sea urchin. The average particle size of the Bi2O3 / TF photocatalyst is about 1 μm, and the Bi2O3 / TF photocatalyst has an obvious heterojunction interface.

[0074] Elemental Analysis:

[0075] The present invention uses energy dispersive X-ray spectrometer (EDS) to detect Ti, O, and Bi elements in Bi2O3 / TF photocatalyst. Figure 2 As shown, the Ti, O, and Bi elements of the Bi2O3 / TF photocatalyst are evenly distributed.

[0076] Crystallization analysis:

[0077] The present invention uses X-ray diffraction (XRD) pattern ( Figure 1a) The crystal structures of TF, 5wt%Bi2O3 / TF, 5wt%Bi2O3-TF (mm) (physical mixture of anatase titanium dioxide and α-Bi2O3, mm scale) and pure α-Bi2O3 were analyzed. For TF, the diffraction peaks at 25.28°, 37.8°, 48.05°, 53.89° and 55.06° correspond to the (101), (004), (200), (105) and (211) crystal planes of anatase titanium dioxide (JCPDS 21-1272), respectively, indicating that the titanium dioxide synthesized in step 1 (i.e., TF) is anatase titanium dioxide. Compared with TF, the characteristic peaks of 5wt% Bi2O3 / TF remain unchanged, indicating that the formation of α-Bi2O3 (JCPDS 41-1449) does not change the crystal structure of TF. However, compared with 5wt% Bi2O3-TF (mm), 5wt%Bi2O3 / TF does not show the diffraction peak corresponding to α-Bi2O3, which may be due to the high dispersibility, low content and small size of α-Bi2O3.

[0078] Example 2: Preparation of CeO2 / TF photocatalyst (CeO2 / TF)

[0079] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0080] (2) Based on the mass fraction of CeO2 being 5wt% of the CeO2 / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of Ce(NO3)2, and the mixed powder was fully ground at ambient temperature. Subsequently, the ground powder was heated to 650°C at a heating rate of 5°C / min in a muffle furnace in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the CeO2 / TF photocatalyst.

[0081] Example 3: Preparation of ZnO / TF photocatalyst (hereinafter referred to as ZnO / TF)

[0082] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0083] (2) Based on a ZnO mass fraction of 5wt% in the ZnO / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of Zn(NO3)2, and the mixed powder was fully ground at ambient temperature. The ground powder was then heated to 650°C in a muffle furnace at a heating rate of 5°C / min in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the ZnO / TF photocatalyst.

[0084] Example 4: Preparation of NiO / TF photocatalyst (hereinafter referred to as NiO / TF)

[0085] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0086] (2) Based on the mass fraction of NiO being 5wt% of the NiO / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of NiCl2, and the mixed powder was fully ground at ambient temperature. Subsequently, the ground powder was heated to 650°C at a heating rate of 5°C / min in a muffle furnace in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the NiO / TF photocatalyst.

[0087] Example 5: Preparation of CoO / TF photocatalyst (hereinafter referred to as CoO / TF)

[0088] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0089] (2) Based on the mass fraction of CoO being 5wt% of the CoO / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of CoCl2, and the mixed powder was fully ground at ambient temperature. Subsequently, the ground powder was heated to 650°C at a heating rate of 5°C / min in a muffle furnace in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the CoO / TF photocatalyst.

[0090] Example 6: Preparation of CuO / TF photocatalyst (hereinafter referred to as CuO / TF)

[0091] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0092] (2) Based on the mass fraction of CuO being 5wt% of the CuO / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of Cu(NO3)2, and the mixed powder was fully ground at ambient temperature. Subsequently, the ground powder was heated to 650°C at a heating rate of 5°C / min in a muffle furnace in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the CuO / TF photocatalyst.

[0093] Example 7: Preparation of Fe2O3 / TF photocatalyst (hereinafter referred to as Fe2O3 / TF)

[0094] (1) Place 30 mL of acetic acid in a 50 mL polytetrafluoroethylene container, add 100 μL of deionized water, and then drop 1 mL of tetrabutyl titanate and stir at room temperature for 2 hours. The solution turns white, and the polytetrafluoroethylene container is transferred to a stainless steel autoclave, kept at 140°C for 24 hours, and then allowed to cool naturally in the air. The white precipitate is collected by centrifugation, thoroughly washed with ethanol and water, and then dried at 60°C for 3 hours to obtain titanium dioxide, recorded as TF.

[0095] (2) Based on the mass fraction of Fe2O3 being 5wt% of the Fe2O3 / TF photocatalyst, 0.2g of the TF synthesized in step (1) was mixed with the required mass of FeCl3, and the mixed powder was fully ground at ambient temperature. Subsequently, the ground powder was heated to 650°C at a heating rate of 5°C / min in a muffle furnace in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain the Fe2O3 / TF photocatalyst.

[0096] Example 8: Catalyst photocatalytic decarboxylation of stearic acid to formaldehyde performance test

[0097] Reaction conditions: 30 mg of stearic acid, 20 mg of a single photocatalyst, and 10 mL of dodecane were placed in a stainless steel photoreactor; when the temperature reached 28°C, the stainless steel photoreactor was irradiated with an LED light source (central wavelength of 365 nm, power of 40 W), the stirring rate was 1000 rpm, and the reaction time was 2 h. After 2 hours of reaction, the yield of heptadecanal and the conversion rate of stearic acid were calculated.

[0098] Note:

[0099] Conversion rate = (starting mass of stearic acid - remaining mass of stearic acid) / starting mass of stearic acid

[0100] Yield = mass of stearic acid converted to heptadecanal / initial mass of stearic acid

[0101] Selectivity = yield / conversion.

[0102] (1) Catalysts with different types of loading materials

[0103] like Figure 4 As shown, TF, CeO2 / TF, ZnO / TF, NiO / TF, and Bi2O3 / TF all have catalytic activity in the photocatalytic preparation of fatty aldehydes from fatty acids, among which Bi2O3 / TF has the highest fatty aldehyde yield, which can reach 55%, and the conversion rate of fatty acids can reach more than 95%; the yield of TF photocatalytic preparation of fatty aldehydes from fatty acids is relatively low (36%), and the conversion rate of fatty acids is very close to 100%, which is speculated to be the photodegradation of fatty acids into small molecules. Although the photocatalytic yield of aldehydes generated by CeO2 / TF, ZnO / TF, and NiO / TF is not high, they still have a high selectivity for heptadecanal. The present invention tests the catalytic activity of photocatalytic preparation of fatty aldehydes from fatty acids on CoO / TF, CuO / TF, and Fe2O3 / TF, which also have heterojunction structures, and finds that the conversion activity of these photocatalysts for stearic acid is poor or negligible, indicating that not all metal oxides with semiconductor properties have catalytic activity in the photocatalytic preparation of fatty aldehydes from fatty acids after combining with anatase-type titanium dioxide.

[0104] (2) Bi2O3 / TF with different Bi2O3 loadings

[0105] Figure 5 The catalytic activity of Bi2O3 / TF with different Bi2O3 loading amounts in the photocatalytic preparation of fatty aldehydes from fatty acids was demonstrated. Figure 5It is shown that the yield of pure anatase titanium dioxide in the photocatalytic preparation of n-heptadecanal from stearic acid is limited. However, when α-Bi2O3 is formed on pure anatase titanium dioxide, the yield of n-heptadecanal increases and the photocatalytic activity is significantly improved. It is worth noting that the 5wt%Bi2O3 / TF catalyst with a theoretical loading of 5.0 wt% Bi2O3 exhibits the best photocatalytic performance, with a n-heptadecanal yield of 55.33%. However, after increasing the Bi2O3 loading to 10wt%, the yield and conversion rate of the photocatalytic preparation of n-heptadecanal from stearic acid by the 10wt%Bi2O3 / TF catalyst decreased, presumably because the excess Bi2O3 would block the active sites on the anatase titanium dioxide, hindering effective catalysis.

[0106] (3) Photocatalysts with different physical states

[0107] The present invention studies the catalytic activity of TF, pure α-Bi2O3 nanocrystals, a physical mixture of TF and pure α-Bi2O3 nanocrystals (abbreviated as 5wt% Bi2O3-TF, the mass fraction of α-Bi2O3 nanocrystals is 5wt%, and the particle size of the mixture is in the millimeter order), and 5wt% Bi2O3 / TF in photocatalytic preparation of fatty aldehydes from fatty acids under the same conditions.

[0108] like Figure 6 As shown, 5wt% Bi2O3 / TF exhibits a higher yield of n-heptadecanal than other photocatalysts. It is worth noting that the yield of n-heptadecanal catalyzed by 5wt% Bi2O3-TF(mm) is significantly reduced and is comparable to that of TF, while pure α-Bi2O3 nanocrystals have no photocatalytic activity. These results further confirm that the heterojunction promotes the separation and transport of photogenerated carriers and enhances the activation ability of O2. Therefore, the 5wt% Bi2O3 / TF photocatalyst has optimized photocatalytic performance.

[0109] (4) Cyclic stability of 5wt% Bi2O3 / TF photocatalytic preparation of fatty aldehydes from fatty acids

[0110] The present invention studies the photocatalytic stability and durability of 5wt% Bi2O3 / TF. During four cycles of 5wt% Bi2O3 / TF photocatalytic production of n-heptadecanal, the photocatalytic activity of the 5wt% Bi2O3 / TF sample did not show any significant loss, indicating the relative stability of 5wt% Bi2O3 / TF in long-term photocatalytic conversion cycles.

[0111] Example 9: Active species capture experiment

[0112] In order to explore the main active species in the catalytic process, nitrogen was introduced into the reaction mixture of dodecane solution of stearic acid and catalyst, and different target sacrificial agents such as triethanolamine (TEOA) and isopropanol (IPA) were added to observe their inhibition degree on the decarboxylation oxidation of stearic acid. Finally, the mechanism of the catalytic reaction process was analyzed.

[0113] N2, triethanolamine (TEOA) and isopropanol (i-PrOH) were used to capture O2 - 、h + and OH. Figure 8 As shown in a, the conversion of heptadecanal did not change significantly after the addition of isopropanol. However, in the presence of N2 and TEOA, the conversion of heptadecanal decreased from 97.56% to 69.35% and 50.38%, respectively, indicating that h + and O2 - It plays a key role in the decarboxylation of stearic acid.

[0114] Example 10: Electron Spin Resonance (ESR) Experiment

[0115] Weigh 5 mg of sample, disperse it in 10 mL of methanol, ultrasonicate for 20 min, prepare a sample solution of moderate concentration, add the capture agent DMPO (5,5-dimethyl-1-pyrroline-N-oxide), transfer the prepared sample solution to the EPR sample tube, and avoid contact with oxygen and water to avoid interfering with the experimental results. Use nitrogen or a vacuum pump to deoxygenate the sample. Trigger the generation of superoxide anion radicals under light. Record the EPR spectrum at the same time to observe the characteristic signal generated after the reaction of DMPO and superoxide anion radicals.

[0116] The present invention uses electron spin resonance (ESR) technology to study O2 - The generation of charge separation patterns of samples was investigated. Figure 8 As shown in Fig. 2a, 5wt% Bi2O3 / TF and TF do not show obvious ESR signals in the dark or under LED illumination. Even under LED illumination, the ESR signal of TF is weak due to its wide band gap. In contrast, 5wt% Bi2O3 / TF shows strong ·O2 - The ESR signal strongly confirms that the built-in electric field generated by the construction of the pn heterojunction drives the ·O2 - Generation of.

[0117] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for photocatalytic decarboxylation of fatty acids or their derivatives to produce aldehydes, characterized in that: include: Carboxylic acid or its derivative, a photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes, and an organic solvent are placed in a photoreactor; Stirring and reacting at room temperature and pressure under ultraviolet light to obtain aldehyde; The photocatalyst is: (i) anatase titanium dioxide; or, (ii) A heterojunction photocatalyst with anatase titanium dioxide as the carrier and one of Bi2O3, CeO2, ZnO, and NiO as the active component.

2. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 1, characterized in that: The carboxylic acid is a carboxylic acid having 2 to 18 carbon atoms.

3. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 1, characterized in that: The active components account for 0.1wt%~10wt% in the catalyst.

4. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 1, characterized in that: Bi2O3 is α-Bi2O3 nanocrystals.

5. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 1, characterized in that: The particle size of the heterojunction photocatalyst is 0.1~2 microns.

6. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 1, characterized in that: The preparation method of the heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes comprises: The anatase titanium dioxide is mixed with the precursor of the active component and then fully ground; the active component is one of Bi2O3, CeO2, ZnO, and NiO; the precursor of the active component is nitrate or chloride; The ground material is fully calcined in an oxygen atmosphere at 400-650° C., and the calcined product is cooled to room temperature to obtain a heterojunction photocatalyst for catalyzing the decarboxylation of fatty acids to produce aldehydes.

7. The method for preparing aldehydes by photocatalytic decarboxylation of fatty acids or their derivatives according to claim 6, characterized in that: The precursor of Bi2O3 is Bi(NO3)3·5H2O, the precursor of CeO2 is Ce(NO3)2, the precursor of ZnO is Zn(NO3)2, and the precursor of NiO is NiCl2.

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