A light attenuation compensation type detachable photo-thermal catalytic cartridge and a biodiesel preparation method

Abstract

The present application belongs to the field of biodiesel preparation and light-induced thermal catalysis, and relates to a light attenuation compensation type detachable light-thermal catalysis cassette and a biodiesel preparation method. The light-thermal catalysis cassette comprises a cassette frame and at least two light-transmitting type catalytic layers arranged in turn along the direction of incident light in the frame; with the plane perpendicular to the incident light as a projection plane, the light-thermal catalyst loading of each light-transmitting type catalytic layer per unit projection area increases gradually along the direction of incident light propagation, and the incident light enters the cassette from the side with lower catalyst loading. The present application adopts a multi-layer structure with gradually increasing catalyst loading, the front-end catalytic layer has both light-transmitting and catalytic functions, improves the utilization efficiency of attenuated light at the rear end, optimizes the light intensity distribution and temperature uniformity of the system, and improves the light energy utilization rate; the cassette is used for ester exchange and / or esterification reaction of oil and low-carbon alcohol to prepare biodiesel, and the catalytic assembly is easy to disassemble and clean, and can be reused.

Description

Technical Field

[0001] This invention belongs to the field of biodiesel preparation and photoinduced thermocatalytic reaction technology, specifically relating to a light attenuation compensated detachable photothermal catalytic cartridge and a biodiesel preparation method. Background Technology

[0002] Biodiesel typically refers to the product prepared by transesterification and / or esterification reactions of lipid-containing raw materials such as vegetable oil, animal oil, waste edible oil, acidified oil, and microbial oil with low-carbon alcohols such as methanol and ethanol. In the biodiesel production process, heterogeneous solid catalysts are often used to replace traditional homogeneous acid-base catalysts. This significantly reduces the need for neutralization and washing processes, decreasing the discharge of saline wastewater and subsequent wastewater treatment costs. However, powdered heterogeneous catalysts require complex solid-liquid separation processes such as filtration and centrifugation after the reaction, resulting in a lengthy separation process. Furthermore, this process is prone to catalyst particle loss and the inclusion of solid particulate impurities in the finished biodiesel, increasing the difficulty of product purification.

[0003] Photothermal catalytic materials can capture incident light and convert light energy into heat energy in situ through non-radiative relaxation, creating a localized high-temperature environment in the catalyst micro-region. This provides thermal power for the esterification and transesterification reactions of oils and lower alcohols, significantly reducing the overall energy consumption for heating the system. Currently, photothermal catalysts are immobilized on light- and liquid-permeable carriers and then integrated into a detachable cartridge structure, eliminating the possibility of powdered catalyst contamination in the product. Furthermore, the catalyst components can be individually removed for cleaning, regeneration, or replacement, simplifying post-production processing.

[0004] However, existing multilayer immobilized photothermal catalytic cartridges still face significant technical challenges: when multiple catalytic layers are arranged sequentially along the light path, a uniform catalyst loading design is used for each. As incident light passes through the front catalytic layer, it is continuously absorbed and scattered by the catalyst particles, causing the light intensity to continuously attenuate along the propagation path. This results in a significant decrease in the usable light energy of the rear catalytic layers, leading to uneven overall catalytic reaction efficiency. Simply increasing the uniform loading of each layer exacerbates the light-blocking effect of the front catalytic layer, further worsening the light loss at the rear. While reducing the overall loading of all catalytic layers can improve light transmittance, the total catalyst load in the cartridge is insufficient, resulting in low conversion efficiency per unit volume. The existing uniform loading method cannot simultaneously meet the light transmittance requirements of the front catalytic layer and the absorption requirements of the rear catalytic layer for attenuated light, resulting in low light energy utilization and hindering the large-scale application of photothermal catalytic systems in the continuous production of biodiesel. Summary of the Invention

[0005] The purpose of this invention is to provide a light attenuation-compensated detachable photothermal catalytic cartridge and a biodiesel preparation method, thereby overcoming the shortcomings of the prior art. The detachable photothermal catalytic cartridge with a catalyst loading gradient set along the direction of incident light propagation compensates for the attenuation of light intensity along the optical path, while retaining the characteristics of the catalytic component being detachable, washable and reusable.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a light attenuation compensated detachable photothermal catalytic cartridge, comprising a cartridge frame and at least two transparent catalytic layers arranged sequentially along the incident light propagation direction inside the cartridge. The light-transparent catalytic layer includes a support and a photothermal catalyst fixed on the support; Using a plane perpendicular to the direction of incident light propagation as the projection plane, the loading of photothermal catalyst per unit projection plane in the transparent catalyst layer increases stepwise along the direction of incident light propagation to compensate for the light intensity attenuation during the propagation of incident light along the direction of propagation. The incident light enters the cartridge frame from the side of the transparent catalyst layer with the smallest photothermal catalyst loading.

[0007] This invention progressively increases the catalyst loading per unit area of ​​each transparent catalyst layer along the direction of incident light propagation, so that the front catalyst layer has both catalytic and light-transmitting functions, and the rear catalyst layer enhances the absorption of attenuated light, which helps to reduce the excessive shading at the front and insufficient light reception at the rear caused by the uniform high-load structure.

[0008] Secondly, the present invention provides a biodiesel production system, including a light source, a reactor, a raw material mixing unit, and a conveying unit; the reactor is equipped with a light attenuation compensated detachable photothermal catalytic cartridge, and a light-transmitting window is provided on one side wall of the reactor; The incident light from the light source enters through the light-transmitting window from the side of the light-transmitting catalytic layer with the smallest catalyst loading in the photothermal catalytic cartridge, and then sequentially irradiates each light-transmitting catalytic layer.

[0009] The gradient configuration of this invention is based on the direction of light propagation and does not require changing the feeding direction of oils and low-carbon alcohols. It can be used in conjunction with circulating, intermittent or continuous biodiesel production systems.

[0010] Thirdly, the present invention provides a method for preparing biodiesel, which employs a biodiesel preparation system and includes the following steps: mixing oil raw materials with low-carbon alcohols to prepare a reaction solution, and conveying it to the reactor through a conveying unit; When the light source is turned on, the light enters the light-attenuation compensated detachable photothermal catalytic cartridge through the light-transmitting window of the reactor. The light enters from the side of the light-transmitting catalytic layer with the lowest catalyst loading in the cartridge and passes through each light-transmitting catalytic layer one by one. Under the action of the local thermal environment generated by each layer of photothermal catalyst, the reaction liquid undergoes transesterification and / or esterification. After the photothermal catalytic reaction is completed, the reaction products are separated and purified. The photothermal catalytic cartridge in the reactor is disassembled as a whole, or each transparent catalytic layer is separated individually, and the catalytic components are cleaned, regenerated or replaced.

[0011] The beneficial effects of this invention are: This invention progressively increases the catalyst loading per unit area of ​​each transparent catalyst layer along the direction of incident light propagation. This allows the front catalyst layer to function as both a catalytic layer and a light-transmitting layer, while the rear catalyst layer enhances the absorption of attenuated light. This helps mitigate the excessive shading at the front and insufficient light reception at the rear caused by a uniform, high-load structure. Each catalyst layer can be independently installed and removed, facilitating separate measurements of catalyst loading, transmitted light intensity, and catalyst layer temperature. The number of layers and the loading gradient can be adjusted based on the measured results. The photothermal catalyst is fixed on a transparent, liquid-permeable carrier and stored in a cartridge, reducing the amount of powdered catalyst entering the reaction products and facilitating catalyst recovery, cleaning, and reuse. The gradient configuration of this invention is based on the direction of light propagation and does not require changing the feed direction of oils and low-carbon alcohols, allowing it to be used in conjunction with circulating, intermittent, or continuous biodiesel production systems. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 This is a schematic diagram of the structure of the light attenuation compensated detachable photothermal catalytic cartridge and biodiesel preparation system in Embodiment 1 of the present invention; Figure 2 This is a schematic cross-sectional view of the detachable photothermal catalytic cartridge in Embodiment 1 of the present invention; Explanation of reference numerals in the attached drawings: 1 Xenon lamp; 2 Light-transmitting window; 3 Reactor; 4 Photothermal catalytic cartridge; 5 First light-transmitting catalytic layer; 6 Second light-transmitting catalytic layer; 7 Third light-transmitting catalytic layer; 8 Reaction liquid inlet; 9 Reaction liquid outlet; 10 Raw material mixing tank; 11 Transfer pump; 12 Condensation reflux unit; 20 Cartridge frame; 21 Lifting part; 22 First catalytic layer; 23 Second catalytic layer; 24 Third catalytic layer; 25 Spacer; 26 Seal; 27 Reaction liquid flow direction. Detailed Implementation

[0014] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0015] Technical terms: Photothermal catalysis refers to the process by which a catalytic material absorbs incident light and converts at least a portion of the light energy into heat, creating a thermal environment near the catalytic material that is conducive to transesterification and / or esterification reactions. In the absence of evidence that photogenerated carriers directly participate in the reaction, it is not limited to the traditional photogenerated electron-hole direct-driven reaction.

[0016] Catalyst loading per unit projected area: This refers to the ratio of the mass increment of a transparent catalyst layer after catalyst loading to the projected area of ​​that catalyst layer on a plane perpendicular to the direction of incident light propagation. For supports with the same size and porosity, this parameter can be used to compare the actual catalyst loading levels of different catalyst layers.

[0017] The catalyst loading increases gradually: This means that along the direction of incident light propagation, the catalyst loading per unit projected area of ​​the adjacent subsequent layer is greater than that of the adjacent preceding layer; the increase can be an arithmetic or geometric progression or a nonlinear gradient determined based on the measured transmitted light intensity of each layer.

[0018] To address the problems of excessive light blocking in the front catalyst layer, insufficient light exposure in the rear catalyst layer, and inconvenience in recovering powdered catalyst in existing multi-layer immobilized photothermal catalytic cartridges, this invention provides a light attenuation compensated detachable photothermal catalytic cartridge and a method for preparing biodiesel.

[0019] In a first aspect, the present invention provides a light attenuation compensated detachable photothermal catalytic cartridge, comprising a cartridge frame and at least two transparent catalytic layers arranged sequentially along the incident light propagation direction inside the cartridge. The light-transparent catalytic layer includes a support and a photothermal catalyst fixed on the support; Using a plane perpendicular to the direction of incident light propagation as the projection plane, the loading of photothermal catalyst per unit projection plane in the transparent catalyst layer increases stepwise along the direction of incident light propagation to compensate for the light intensity attenuation during the propagation of incident light along the direction of propagation. Incident light enters the cartridge frame from the side of the transparent catalyst layer with the lowest photothermal catalyst loading, allowing some of the incident light to continue propagating backward in the front low-load catalyst layer, while the rear high-load catalyst layer is used to enhance the absorption of light that has attenuated after passing through the front catalyst layer.

[0020] Furthermore, the number of light-transmitting catalyst layers is 2-8, and the projected area, thickness, and porosity of the carrier in each light-transmitting catalyst layer are consistent; preferably, the number of light-transmitting catalyst layers is 3-5; the size, thickness, and porosity of the carrier in each layer are the same or substantially the same, so that the catalyst loading becomes the main gradient variable.

[0021] The light-transparent catalyst layer is detachably connected to the cartridge frame. Each light-transparent catalyst layer is installed in the cartridge frame via slots, clips, pressure frames, or detachable fasteners, and the interlayer distance is maintained by spacers, so that each light-transparent catalyst layer can be individually disassembled, weighed, cleaned, regenerated, or replaced.

[0022] Furthermore, the support in the transparent catalyst layer is one or more of the following: metal wire mesh, quartz fiber mesh, glass fiber mesh, perforated plate, porous ceramic sheet, honeycomb ceramic sheet, and foam ceramic sheet. The support material should be compatible with the low-carbon alcohol, oil raw material, catalyst preparation temperature, and reaction temperature used.

[0023] Furthermore, the photothermal catalyst in the transparent catalytic layer is a solid acid catalyst, a solid base catalyst, or an acid-base bifunctional catalyst that can absorb incident light and convert at least part of the light energy into heat, while also being able to catalyze transesterification and / or esterification reactions. Preferably, the photothermal catalyst is one or more of perovskite materials, metal oxides, carbon-based photothermal materials, and their composite materials.

[0024] Catalyst loading gradients are formed through one or more of the following methods: using catalyst slurries of different concentrations; using different numbers of impregnation, spraying, or scraping processes; changing the thickness of the catalytic coating; changing the coverage ratio of the catalytic region on the support; or growing catalysts with different loadings in situ on the surface of the support.

[0025] The catalyst loading of each layer is determined by the ratio of the mass difference before and after loading on the support to its projected area. Let the loading per unit projected area of ​​each layer arranged sequentially along the direction of incident light propagation be M1, M2, ..., M... n Then it satisfies M1 < M2 < ... < M n .

[0026] Furthermore, spacers are provided between adjacent transparent catalyst layers.

[0027] Secondly, the present invention provides a biodiesel production system, including a light source, a reactor, a raw material mixing unit, and a conveying unit; the reactor is equipped with a light attenuation compensated detachable photothermal catalytic cartridge, and a light-transmitting window is provided on one side wall of the reactor; The incident light from the light source enters through the light-transmitting window from the side of the light-transmitting catalytic layer with the smallest catalyst loading in the photothermal catalytic cartridge, and then sequentially irradiates each light-transmitting catalytic layer.

[0028] Furthermore, the light source is a xenon lamp, and the light-transmitting window is a quartz window or a light-transmitting window resistant to reactive media; The reactor is a closed pressure-resistant reactor or a reactor equipped with a condensation reflux unit.

[0029] Thirdly, the present invention provides a method for preparing biodiesel, which employs a biodiesel preparation system and includes the following steps: mixing oil raw materials with low-carbon alcohols to prepare a reaction solution, and conveying it to the reactor through a conveying unit; When the light source is turned on, the light enters the light-attenuation compensated detachable photothermal catalytic cartridge through the light-transmitting window of the reactor. The light enters from the side of the light-transmitting catalytic layer with the lowest catalyst loading in the cartridge and passes through each light-transmitting catalytic layer one by one. Under the action of the local thermal environment generated by each layer of photothermal catalyst, the reaction liquid undergoes transesterification and / or esterification. After the photothermal catalytic reaction is completed, the reaction products are separated and purified. The photothermal catalytic cartridge in the reactor is disassembled as a whole, or each transparent catalytic layer is separated individually, and the catalytic components are cleaned, regenerated or replaced.

[0030] Furthermore, the oil raw materials are vegetable oils, animal oils, waste edible oils, acidified oils, microbial oils, and mixtures thereof; the low-carbon alcohols are methanol, ethanol, or mixtures thereof.

[0031] Furthermore, it also includes measuring the transmitted light intensity between adjacent transparent catalyst layers and / or the surface temperature of each transparent catalyst layer before or during the reaction, and adjusting the catalyst loading gradient by replacing the transparent catalyst layer based on the measurement results. The following is a further explanation with reference to specific embodiments and comparative examples: Example 1 This embodiment provides a biodiesel production system with a detachable photothermal catalytic cartridge that includes light attenuation compensation, such as... Figure 1 As shown, the system includes a xenon lamp 1 (light source), a reactor 3, and a raw material mixing tank 10. The reactor 3 is a closed, pressure-resistant reactor. A photothermal catalytic cartridge 4 is installed inside the reactor 3. The photothermal catalytic cartridge 4 includes a cartridge frame and at least two transparent catalytic layers arranged sequentially along a predetermined incident light propagation direction within the cartridge frame. Each transparent catalytic layer includes a light-transmitting and liquid-transmitting carrier and a photothermal catalyst fixed on the carrier. The transparent catalytic layer has a projection plane perpendicular to the incident light propagation direction, and the photothermal catalyst loading per unit projected area increases progressively along the incident light propagation direction. Incident light enters the cartridge from the side of the transparent catalytic layer with the lowest catalyst loading, allowing some incident light to continue propagating backward through the lower-loaded front catalytic layer, while the higher-loaded rear catalytic layer enhances the absorption of light attenuated after passing through the front catalytic layer.

[0032] The raw material mixing tank 10 is used for stirring, static mixing, or circulating mixing of oil raw materials and low-carbon alcohols. A condensation reflux unit 12 is provided on the outer top of the reactor 3. A light-transmitting window 2 is provided on one side wall of the reactor 3 to transmit light from the xenon lamp 1 into the reactor 3, providing a light source for photocatalysis. A reaction liquid inlet 8 is provided at the bottom of one side wall of the reactor 3. The raw materials in the raw material mixing tank 10 enter the reactor 3 via the transfer pump 11 and the reaction liquid inlet 8 for photothermal catalytic reaction. The reaction liquid inlet 8 and the light-transmitting window 2 are located on the same side wall of the reactor 3. A reaction liquid outlet 9 is provided on the upper part of the other side wall of the reactor 3 to discharge the reacted liquid.

[0033] Specifically, the photothermal catalytic cartridge 4 includes a cartridge frame and at least two transparent catalytic layers arranged sequentially along a predetermined incident light propagation direction within the cartridge frame. The transparent catalytic layers are 2-8 layers, preferably 3-5 layers.

[0034] The light-transparent catalyst layer includes a light-transmitting and liquid-transmitting support and a photothermal catalyst fixed on the support. The light-transmitting catalyst layer uses a plane perpendicular to the direction of incident light propagation as its projection surface, and the photothermal catalyst loading per unit projected area of ​​the light-transmitting catalyst layer increases stepwise along the direction of incident light propagation.

[0035] Incident light enters the cartridge from the side of the transparent catalyst layer with the lowest catalyst loading, allowing some of the incident light to continue propagating backward in the front low-load catalyst layer, while the rear high-load catalyst layer is used to enhance the absorption of light that has attenuated after passing through the front catalyst layer.

[0036] The light- and liquid-permeable carrier is one of the following: metal wire mesh, quartz fiber mesh, glass fiber mesh, perforated plate, porous ceramic sheet, honeycomb ceramic sheet, or foam ceramic sheet. The carrier material should be compatible with the preparation temperature and reaction temperature of the low-carbon alcohol, oil raw material, catalyst, and reaction.

[0037] Each transparent catalyst layer is installed in the cartridge frame via slots, clips, pressure frames or detachable fasteners, and the interlayer distance is maintained by spacers, so that each transparent catalyst layer can be disassembled, weighed, cleaned, regenerated or replaced individually.

[0038] For example, such as Figure 1As shown, the photothermal catalytic cartridge 4 has a three-layer gradient loading cartridge structure. Specifically, the cartridge frame is a rectangular frame, within which three parallel and independently removable transparent catalytic layers are arranged: a first transparent catalytic layer 5, a second transparent catalytic layer 6, and a third transparent catalytic layer 7. The three transparent catalytic layers use transparent and liquid-permeable carriers of the same size, thickness, and porosity, and are sequentially designated as the first transparent catalytic layer 5, the second transparent catalytic layer 6, and the third transparent catalytic layer 7 along the direction of incident light propagation from the xenon lamp 1. The same photothermal catalyst is fixed on the surfaces of the three carriers, and different loading amounts are achieved by varying the number of impregnations or sprayings. As a structural design example, the loading amount per unit projected area of ​​the three catalytic layers can be set in a ratio of 1:1.5:2; this ratio is only used to illustrate the gradient relationship, and the actual ratio should be determined based on the measured results of single-layer transmitted light intensity, catalytic layer surface temperature, pressure drop, and reaction performance.

[0039] The first transparent catalyst layer 5 is disposed on the side close to the transparent window 2, and the third transparent catalyst layer 7 is disposed on the side away from the transparent window 2.

[0040] like Figure 2 As shown, a first catalyst layer 22, a second catalyst layer 23, and a third catalyst layer 24 are respectively disposed on the first transparent catalyst layer 5, the second transparent catalyst layer 6, and the third transparent catalyst layer 7. The catalyst layers are spaced apart by spacers 25 and fixed within the cartridge frame 20 via slots. A sealing element 26 is provided at the bottom of the cartridge frame 20, and a lifting part 21 is provided at the top of the cartridge frame 20, allowing the cartridge frame 20 to be removed entirely from the reactor; each catalyst layer can also be removed separately from the cartridge frame 20.

[0041] Example 2 This embodiment provides a light-attenuation-compensated detachable photothermal catalytic cartridge gradient catalytic layer and its preparation method, the specific steps of which are as follows: Three identical supports with known mass and projected area were selected (labeled as support 1, support 2, and support 3, respectively), and their initial mass was recorded. The prepared photothermal catalyst was dispersed in a suitable dispersion medium for the catalyst and support to form a stable slurry.

[0042] The first support undergoes one impregnation-drying process, the second support undergoes two impregnation-drying processes, and the third support undergoes three impregnation-drying processes; alternatively, three supports can be treated separately using three slurries with progressively increasing concentrations. When using inorganic oxide or perovskite catalysts, appropriate calcination can be performed based on the catalyst's crystal phase stability and the support's temperature resistance; when using carbon-based materials that are not heat-resistant, low-temperature drying or inert atmosphere heat treatment should be employed.

[0043] After processing, each support was weighed separately, and the catalyst loading per unit projected area was calculated by dividing the mass increment by the projected area. The cartridges were loaded in the order of first, second, and third layers only if the three catalyst layers satisfied M1 < M2 < M3. If the loading of a certain layer did not meet the predetermined gradient, it could be adjusted by increasing the number of coating passes or replacing the catalyst layer.

[0044] Example 3 This embodiment provides a method for photothermal catalysis to prepare biodiesel, using the biodiesel preparation system in Example 1. The specific steps are as follows: Sr₂NiMoO₆ was used as the photothermal catalyst, and three metal wire meshes of the same size, thickness, and porosity were used as light-transmitting and liquid-transmitting supports, each with a projected area of ​​200 cm². 2 Using 100 g of palm oil as the oilseed, the total photothermal catalyst loading on the three transparent catalyst layers was 5.82 g, and the catalysts were gradient-loaded along the direction of incident light propagation in a ratio of 1:1.5:2. Specifically, the catalyst loadings of the first, second, and third transparent catalyst layers were 1.29 g, 1.94 g, and 2.59 g, respectively, corresponding to a catalyst loading of 6.45 mg / cm² per unit projected area. 2 9.70 mg / cm 2 and 12.95 mg / cm 2 Three transparent catalyst layers are installed sequentially in the cartridge frame in order of increasing catalyst loading, with a spacing of 10 mm between adjacent transparent catalyst layers.

[0045] 100 g of palm oil and methanol are added to the raw material mixing tank 10 at a molar ratio of 12.97:1 and mixed. The resulting reaction solution is then transported to the reactor 3 by the transfer pump 11, so that the reaction solution is in full contact with the photothermal catalytic cartridge 4.

[0046] A 300 W xenon lamp 1 was used as the light source. The xenon lamp 1 was positioned outside the light-transmitting window 2 of the reactor 3, with a distance of 100 mm between the light-emitting end of the xenon lamp and the light-transmitting window 2. The xenon lamp 1 was turned on, allowing incident light to enter the reactor 3 through the light-transmitting window 2. The light entered from the side of the first light-transmitting catalyst layer with the lowest catalyst loading, passing sequentially through the first, second, and third light-transmitting catalyst layers. The photo-irradiation reaction lasted for 2.26 h.

[0047] During the reaction, the surface temperature of the three transparent catalyst layers was measured, and the transmitted light intensity after passing through each transparent catalyst layer was also measured. The incident light intensity before entering the first transparent catalyst layer was denoted as I0, and the transmitted light intensities after passing through the first, second, and third transparent catalyst layers were denoted as I1, I2, and I3, respectively.

[0048] The average surface temperatures of the first, second, and third transparent catalyst layers during the stable illumination stage were measured to be 87.4°C, 84.9°C, and 82.7°C, respectively, with a maximum temperature difference of 4.7°C between the three transparent catalyst layers; the ratios I1 / I0, I2 / I0, and I3 / I0 were 0.68, 0.41, and 0.18, respectively.

[0049] After the reaction was completed, xenon lamp 1 was turned off, the reaction products were discharged, excess methanol was recovered, and the mixture was allowed to stand for phase separation. The glycerol phase was then separated to obtain the biodiesel product. Gas chromatography analysis showed that the biodiesel yield was 95.8%.

[0050] After the reaction was completed, the photothermal catalyst cartridge 4 was removed entirely from reactor 3, and the three transparent catalyst layers were disassembled, cleaned with methanol, dried, and weighed. The single-stage immobilization recovery rate of the photothermal catalyst was determined to be 99.3%.

[0051] The results show that gradually increasing the catalyst loading along the direction of incident light propagation can improve the utilization of attenuated light by the rear catalyst layer while maintaining the light transmittance of the front catalyst layer, thereby reducing the temperature difference between different catalyst layers and realizing the photothermal catalytic conversion of oils.

[0052] Comparative Example 1 The same cartridge frame, number of supports, support size, porosity, interlayer spacing, and total mass of Sr2NiMoO6 photothermal catalyst as in Example 3 were used. The difference was that the three transparent catalyst layers used the same catalyst loading: 1.94 g of photothermal catalyst was loaded onto each of the first, second, and third transparent catalyst layers, corresponding to a catalyst loading of 9.70 mg / cm² per unit projected area. 2 The total mass of the catalyst in the three catalyst layers remains 5.82 g.

[0053] Except for the different catalyst loading distribution, the oil feedstock, alcohol-oil molar ratio, light source power, distance between the xenon lamp and the light transmission window, and reaction time are all the same as in Example 3.

[0054] The average surface temperatures of the first, second, and third transparent catalyst layers during the stable illumination stage were measured to be 92.0 ℃, 80.8 ℃, and 72.5 ℃, respectively, with a maximum temperature difference of 19.5 ℃ between the three transparent catalyst layers; the ratios I1 / I0, I2 / I0, and I3 / I0 were 0.54, 0.30, and 0.17, respectively.

[0055] After the reaction was completed, the products were separated and analyzed in the same manner as in Example 3. The biodiesel yield was 91.4% and the single-stage immobilization recovery rate of the photothermal catalyst was 99.2%.

[0056] Compared to Example 3, under the same total catalyst mass and other reaction conditions, the first transparent catalyst layer of the uniformly loaded cartridge has a higher catalyst loading, resulting in stronger absorption and blocking of incident light. This reduces the effective light intensity reaching subsequent catalyst layers, leading to a more pronounced temperature gradient along the direction of incident light propagation. Example 3, by progressively increasing the catalyst loading along the direction of incident light propagation, allows more incident light to pass through the lower-loaded front catalyst layer and propagate backward, thereby improving the light reception of the subsequent catalyst layers, reducing the temperature difference between different catalyst layers, and increasing biodiesel yield.

[0057] Comparative Example 2 5.82 g of Sr2NiMoO6 photothermal catalyst powder was weighed and directly added to a reaction system consisting of 100 g of palm oil and methanol. The molar ratio of methanol to palm oil was 12.97:1. A 300 W xenon lamp was used as the light source, with a distance of 100 mm between the light-emitting end of the xenon lamp and the light-transmitting window of the reactor. The reaction was carried out under the same conditions as in Example 3 for 2.26 h.

[0058] After the reaction was completed, the powdered photothermal catalyst was separated from the reaction products by centrifugation. The resulting liquid phase was then subjected to methanol recovery, sedimentation, and separation of the glycerol phase to obtain the biodiesel product. Gas chromatography analysis showed that the biodiesel yield was 97.6%.

[0059] The separated powdered photothermal catalyst was washed with methanol, dried, and weighed. The single catalyst recovery rate was 95.6%. During the solid-liquid separation process, a small amount of fine catalyst particles were observed to remain in the liquid phase, requiring further centrifugation or filtration.

[0060] Compared with Comparative Example 2, after adopting the immobilized photothermal catalytic cartridge in Example 3, the biodiesel yield changed from 97.6% to 95.8%, while still maintaining a high level of reaction conversion. At the same time, the catalyst single-pass recovery rate increased from 95.6% to 99.3%. After the reaction, the catalyst and reaction liquid could be quickly separated by removing the photothermal catalytic cartridge as a whole, reducing the entrainment of powdered catalyst in the product and simplifying the solid-liquid separation operation.

[0061] Based on the results of Example 3 and Comparative Examples 1 and 2, it is evident that, with the same total catalyst load, progressively increasing the catalyst loading per unit projected area of ​​each transparent catalyst layer along the incident light propagation direction helps reduce excessive absorption of incident light by the front catalyst layer, allowing some light energy to be further transferred to the rear catalyst layer. Furthermore, increasing the catalyst loading in the rear layer enhances the utilization of attenuated light, thereby improving the light energy and temperature distribution within the multilayer photothermal catalytic cartridge. Simultaneously, fixing the photothermal catalyst to a detachable carrier reduces the entry of powdered catalyst into the reaction products and facilitates the overall recovery, cleaning, and reuse of the catalyst.

[0062] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, equivalent substitutions or improvements can be made to the number of catalyst layers, support form, catalyst type, loading gradient, and reactor structure without departing from the core concept of the present invention, and all such substitutions or improvements should fall within the protection scope of the present invention.

Claims

1. A detachable photothermal catalytic cartridge with light attenuation compensation, characterized in that, It includes a cartridge frame and at least two transparent catalyst layers arranged sequentially along the direction of incident light propagation inside it; The light-transparent catalytic layer includes a support and a photothermal catalyst fixed on the support; Using a plane perpendicular to the direction of incident light propagation as the projection plane, the loading of photothermal catalyst per unit projection plane in the transparent catalyst layer increases stepwise along the direction of incident light propagation to compensate for the light intensity attenuation during the propagation of incident light along the direction of propagation. The incident light enters the cartridge frame from the side of the transparent catalyst layer with the smallest photothermal catalyst loading.

2. The light attenuation compensated detachable photothermal catalytic cartridge as described in claim 1, characterized in that, The number of light-transmitting catalyst layers is 2-8, and the projected area, thickness and porosity of the carrier in each light-transmitting catalyst layer are consistent. The light-transparent catalyst layer is detachably connected to the cartridge frame.

3. The light attenuation compensated detachable photothermal catalytic cartridge as described in claim 1, characterized in that, The carrier in the transparent catalyst layer is one or more of the following: metal wire mesh, quartz fiber mesh, glass fiber mesh, perforated plate, porous ceramic sheet, honeycomb ceramic sheet, and foam ceramic sheet.

4. The light attenuation compensated detachable photothermal catalytic cartridge as described in claim 1, characterized in that, The photothermal catalyst in the transparent catalytic layer is a solid acid catalyst, a solid base catalyst, or an acid-base bifunctional catalyst that can absorb incident light and convert at least part of the light energy into heat, and can catalyze transesterification and / or esterification reactions. Preferably, the photothermal catalyst includes, but is not limited to, one or more of perovskite materials, metal oxides, carbon-based photothermal materials, and their composite materials.

5. The light attenuation compensated detachable photothermal catalytic cartridge as described in claim 2, characterized in that, Spacers are provided between adjacent transparent catalyst layers.

6. A biodiesel production system, characterized in that, It includes a light source, a reactor, a raw material mixing unit, and a conveying unit; the reactor is equipped with a light attenuation compensated detachable photothermal catalytic cartridge as described in any one of claims 1-5, and a light-transmitting window is provided on one side wall of the reactor; The incident light from the light source enters through the light-transmitting window from the side of the light-transmitting catalytic layer with the smallest catalyst loading in the photothermal catalytic cartridge, and then sequentially irradiates each light-transmitting catalytic layer.

7. The biodiesel production system as described in claim 6, characterized in that, The light source is a xenon lamp, and the light-transmitting window is a quartz window or a light-transmitting window resistant to reactive media; The reactor is a closed pressure-resistant reactor or a reactor equipped with a condensation reflux unit.

8. A method for preparing biodiesel, characterized in that, The biodiesel preparation system according to claim 6 or 7 includes the following steps: mixing oil raw materials with low carbon alcohols to prepare a reaction solution, and conveying it to the reactor through a conveying unit; When the light source is turned on, the light enters the light-attenuation compensated detachable photothermal catalytic cartridge through the light-transmitting window of the reactor. The light enters from the side of the light-transmitting catalytic layer with the lowest catalyst loading in the cartridge and passes through each light-transmitting catalytic layer one by one. Under the action of the local thermal environment generated by each layer of photothermal catalyst, the reaction liquid undergoes transesterification and / or esterification. After the photothermal catalytic reaction is completed, the reaction products are separated and purified. The photothermal catalytic cartridge in the reactor is disassembled as a whole, or each transparent catalytic layer is separated individually, and the catalytic components are cleaned, regenerated or replaced.

9. The preparation method according to claim 8, characterized in that, The oil raw materials are vegetable oil, animal oil, waste edible oil, acidified oil, microbial oil and mixtures thereof; the low-carbon alcohol is methanol, ethanol or mixtures thereof.

10. The preparation method according to claim 8, characterized in that, It also includes measuring the transmitted light intensity between adjacent transparent catalyst layers and / or the surface temperature of each transparent catalyst layer before or during the reaction, and adjusting the catalyst loading gradient by replacing the transparent catalyst layer based on the measurement results.

Images