Preparation method of CNs@PY53 photocatalyst and its application in photocatalytic synchronous production of lactic acid and CO

Abstract

The present invention belongs to the field of catalytic technology, and specifically discloses a preparation method of a CNs@PY53 photocatalyst and its application in photocatalytic synchronous production of lactic acid and CO. The preparation method of the photocatalyst is as follows: (1) Urea is calcined at high temperature in a tubular furnace to obtain carbon nitride. (2) The carbon nitride is dispersed in concentrated hydrochloric acid for exfoliation, and then the obtained solid is ultrasonicated and freeze-dried to obtain carbon nitride quantum dots. (3) The carbon nitride quantum dots and titanium nickel yellow are dispersed in ethanol, mixed and ultrasonicated, and then evaporated to dryness to obtain the CNs@PY53 catalyst. The photocatalyst prepared by the present invention has good recyclability, chemical stability and application universality, can efficiently and selectively oxidize different biomass-based monosaccharides into lactic acid and CO, is easy to realize industrial production, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to a preparation method of CNs@PY53 photocatalyst and its application in the photocatalytic selective oxidation of biomass-based monosaccharides to break C-C bonds and simultaneously produce lactic acid and CO, belonging to the field of catalytic technology. Background Art

[0002] With the increasing depletion of non-renewable resources such as petroleum, the production of chemical products from renewable biomass has become a trend for the sustainable development of the chemical industry. As an important component of syngas, CO can be used to synthesize a series of high-value-added chemicals, such as methanol, ethylene, propylene, long-chain alkanes, aldehydes, etc. Traditional methods for producing CO mainly include the coke-pure oxygen method, the water gas pressure swing adsorption method, and the coke pure oxygen carbon dioxide gas production method, etc. However, these methods all need to be carried out under high-temperature conditions, and generally have problems such as complex operation, high energy consumption, and heavy pollution. Therefore, their practical applications have great limitations. However, the preparation of CO by photocatalytic selective oxidation of biomass-based raw materials as an emerging technology has the advantages of mild and easy-to-control reaction conditions, low cost, and environmental friendliness, and this method has been proven to be feasible. Lactic acid, as one of the world's three major organic acids, is also one of the important products of the selective oxidation of biomass-based raw materials. Lactic acid has unique acidity, hydrophilicity, and good biocompatibility, and has been widely used in industries such as food, medicine, and chemical engineering. As a key resource for the development of bioeconomy and biomass conversion, the market demand for lactic acid is increasing day by day. Therefore, how to selectively oxidize biomass-based raw materials by photocatalytic technology to simultaneously produce lactic acid and CO while realizing the separation of liquid / gas products is one of the key technical problems in this field. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of CNs@PY53 photocatalyst material and its application in the photocatalytic selective oxidation of biomass-based monosaccharides to break C-C bonds and simultaneously produce lactic acid and CO for the existing photocatalytic production of lactic acid. Aiming at the problems of high energy consumption and low yield in the existing catalytic system, the CNs@PY53 photocatalyst is prepared by a new and simple method, and various biomass-based monosaccharides are selectively oxidized to lactic acid and CO by photocatalytic technology. The CNs@PY53 photocatalyst prepared by the present invention has good catalytic activity, recyclability, chemical stability, and application universality. The synthesis method of the present invention is simple, easy to control, low-cost, "green" and pollution-free, and has the potential for industrial application.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A preparation method of CNs@PY53 photocatalyst for photocatalytic selective oxidation of biomass-based monosaccharides to simultaneously produce lactic acid and CO, comprising the following steps:

[0006] (1) Anneal urea in a tube furnace at 400 - 600 °C for 2 - 6 h in an N₂ atmosphere (high-temperature calcination), and then cool it naturally to obtain carbon nitride (CN).

[0007] (2) Disperse CN into concentrated hydrochloric acid, heat and stir it in a water bath at 80 - 90 °C for 20 - 30 h for exfoliation to obtain a suspension, filter and wash it to obtain a solid product.

[0008] (3) Disperse the solid product obtained in step (2) into deionized water and ultrasonically treat it for 20 - 30 h.

[0009] (4) Filter the dispersion obtained in step (3) through a 0.22 - 0.45 μm aqueous filter membrane (such as polytetrafluoroethylene filter membrane, nylon filter membrane, mixed cellulose filter membrane and polyethersulfone filter membrane), and then freeze-dry it at -40 - -60 °C for 36 - 48 h to obtain carbon nitride quantum dots (CNs).

[0010] (5) Disperse the CNs obtained in step (4) and titanium nickel yellow (PY53) into absolute ethanol, and mix and ultrasonically treat them for 0.5 - 3.0 h, where the mass ratio of CNs to PY53 is 0.005 - 1.0:0.5 - 3.0.

[0011] (6) Evaporate and dry the dispersion obtained in step (5) at 75 - 95 °C for 2 - 4 h to obtain the CNs@PY53 photocatalyst.

[0012] According to the above technical solution, preferably, in step (1), before use, first place urea in a crucible, heat it to 70 - 90 °C and dry (maintain) it for 1 - 2 h.

[0013] According to the above technical solution, preferably, the heating temperature is 80 °C and the maintaining time is 1 h.

[0014] According to the above technical solution, preferably, in step (1), the annealing temperature is 560 °C and the annealing time is 4 h.

[0015] According to the above technical solution, preferably, in step (2), the ratio of CN to concentrated hydrochloric acid is 2.0 - 10.0 g:20 - 100 mL, preferably 4.0 g:80 mL.

[0016] According to the above technical solution, preferably, in step (2), the heating temperature of the water bath is 90 °C and the heating time is 24 h.

[0017] According to the above technical solution, preferably, in step (2), the suspension is diluted with deionized water and filtered, and the obtained solid is washed with deionized water until neutral.

[0018] According to the above technical solution, preferably, in step (3), the ratio of the solid product to deionized water is 2.0 - 10.0 g: 50 - 500 mL, preferably 2.0 - 4.0 g: 200 mL.

[0019] According to the above technical solution, preferably, in step (4), the filter membrane material is a 0.22 μm polytetrafluoroethylene filter membrane, and the freeze-drying time is 48 h.

[0020] According to the above technical solution, preferably, in step (5), the ultrasonic treatment time is 3 h.

[0021] According to the above technical solution, preferably, in step (5), the mass ratio of CNs to PY53 is 0.005 - 0.3: 0.5 - 1.0 g, preferably 0.1 g: 1.0 g.

[0022] According to the above technical solution, preferably, in step (5), the ratio of CNs to absolute ethanol is 0.005 - 1.0 g: 2 - 80 mL, preferably 0.005 - 0.3 g: 20 - 80 mL, preferably 0.1 g: 40 mL.

[0023] According to the above technical solution, preferably, in step (6), the evaporation and drying temperature is 90 °C, and the evaporation and drying time is 3 h.

[0024] The CNs@PY53 material of the present invention is characterized by means of X-ray diffraction, etc., and is used as a good photocatalyst in the photocatalytic selective oxidation of biomass-based monosaccharides to simultaneously produce lactic acid and CO.

[0025] The application of the CNs@PY53 photocatalyst prepared by the above method in the photocatalytic selective oxidation of biomass-based monosaccharides to simultaneously produce lactic acid and CO has the following reaction process: the above CNs@PY53 photocatalyst, biomass-based monosaccharide and alkaline solution are mixed evenly, and photocatalytic reaction is carried out at 20 - 80 °C for 0.5 - 8.0 h. After the reaction, the contents of lactic acid and CO are detected by a high performance liquid chromatograph and a gas chromatograph.

[0026] According to the above technical solution, preferably, the alkaline solution is a water-soluble alkaline solution, such as potassium hydroxide solution, sodium hydroxide solution, barium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution, etc., preferably potassium hydroxide solution.

[0027] According to the above technical solution, preferably, the concentration of the alkaline solution is 0.05 - 3.0 mol / L, preferably 0.5 mol / L.

[0028] According to the above technical solution, preferably, the biomass-based monosaccharide is xylose, arabinose, fructose, rhamnose, mannose or glucose.

[0029] According to the above technical solution, preferably, the ratio of the catalyst, biomass-based monosaccharide, and alkaline solution is 0.05 - 30 mg: 0.01 - 1.0 g: 20 - 100 mL, preferably 25 mg: 0.2 g: 20 mL.

[0030] According to the above technical solution, preferably, the reaction temperature is 50 °C.

[0031] According to the above technical solution, preferably, the reaction time is 5.0 h.

[0032] The present invention relates to the preparation of the CNs@PY53 photocatalyst and the application of photocatalytic selective oxidation of biomass-based monosaccharides to simultaneously produce lactic acid and CO. The experimental conditions are optimized from aspects such as the catalyst dosage, KOH concentration, reaction temperature, and reaction time; and the recyclability of the CNs@PY53 photocatalyst is explored under the optimal reaction conditions.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention selectively oxidizes biomass-based raw materials through photocatalytic technology to simultaneously produce lactic acid and CO.

[0035] (2) The lactic acid synthesized in the present invention is a chemical with high added value and an important chemical intermediate;

[0036] (3) The CO obtained in the present invention is a high-value energy fuel and an important component of syngas;

[0037] (4) The CNs@PY53 prepared in the present invention as a photocatalyst has excellent properties such as good catalytic activity, recyclability, and application universality;

[0038] (5) The production method of photocatalytic selective oxidation of biomass-based monosaccharides to simultaneously produce lactic acid and CO adopted in the present invention has the advantages of safety, non-toxicity, quick effect, low energy consumption, etc., and has the potential for industrial production;

[0039] (6) The present invention can efficiently and selectively oxidize different biomass-based monosaccharides into lactic acid and CO, is easy to realize industrial production, and has good application prospects;

[0040] (7) The product of the present invention provides an effective way to solve the energy crisis problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 XRD spectra of CNs, PY53 and CNs@PY53 photocatalysts, where a is the CNs@PY53 catalyst obtained after step (8) in Example 1, b is titanium nickel yellow, and c is carbon nitride quantum dots obtained in step (6) in Example 1.

[0042] Figure 2 Graph showing the effect of different catalyst dosages of CNs@PY53 photocatalyst on the photocatalytic synchronous production of lactic acid and CO from biomass-based monosaccharides in Example 2, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate.

[0043] Figure 3 Graph showing the effect of different potassium hydroxide concentrations on the photocatalytic synchronous production of lactic acid and CO from biomass-based monosaccharides by CNs@PY53 photocatalyst in Examples 2 and 3, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate.

[0044] Figure 4 Graph showing the effect of different reaction temperatures on the photocatalytic synchronous production of lactic acid and CO from biomass-based monosaccharides by CNs@PY53 photocatalyst in Examples 3 and 4, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate.

[0045] Figure 5 Graph showing the effect of different reaction times on the photocatalytic synchronous production of lactic acid and CO from biomass-based monosaccharides by CNs@PY53 photocatalyst in Examples 4 and 5, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate.

[0046] Figure 6 Graph showing the catalyst recyclability of CNs@PY53 photocatalyst for the photocatalytic synchronous production of lactic acid and CO from biomass-based monosaccharides in Example 6, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate.

[0047] Figure 7 Graph showing the effect of different biomass-based monosaccharides on the photocatalytic synchronous production of lactic acid and CO by CNs@PY53 photocatalyst in Examples 5 and 7, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate. DETAILED DESCRIPTION OF THE INVENTION

[0048] To better understand the technical features of the present invention, the present invention will be further described below by way of examples, but the scope of protection required by the present invention is not limited thereto.

[0049] Example 1

[0050] (1) Place 20 g of urea in a crucible, heat it to 80 °C and dry it for 1 h;

[0051] (2) Transfer the product obtained in step (1) to a tubular furnace, anneal it at 560 °C for 4 h in an N2 atmosphere, and obtain CN after natural cooling;

[0052] (3) Disperse 4.0 g of the product obtained in step (2) into 80 mL of concentrated hydrochloric acid for exfoliation, and stir it in a water bath at 90 °C for 24 h;

[0053] (4) Add 100 mL of deionized water to the suspension obtained in step (3) for dilution and then filter it, and wash the obtained powder with a large amount of deionized water until neutral;

[0054] (5) Disperse the product obtained in step (4) into 200 mL of deionized water and ultrasonically treat it for 24 h;

[0055] (6) After filtering the dispersion obtained in step (5) through a 0.22 μm polytetrafluoroethylene filter membrane, freeze-dry it at -53 °C for 48 h to obtain CNs;

[0056] (7) Add 0.1 g of the product obtained in step (6) and 1.0 g of PY53 to 40 mL of absolute ethanol and ultrasonically treat it for 3.0 h;

[0057] (8) Evaporate and dry the dispersion obtained in step (7) at 90 °C for 4 h to obtain the CNs@PY53 photocatalyst.

[0058] Example 2

[0059] (1) Take 0.2 g of xylose, 20.0 mL of a KOH solution with a concentration of 1.0 mol / L, and different masses of the CNs@PY53 photocatalyst prepared in Example 1 (5, 10, 15, 20, 25, 30 mg respectively) and add them to a pressure-resistant bottle;

[0060] (2) Seal the system in step (1), add a magnetic stir bar, and stir it for 30 min under dark conditions;

[0061] (3) After sealing the system in step (2), carry out a photocatalytic reaction under illumination at 40 °C through a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s) for 4.0 h;

[0062] (4) Measure the lactic acid and CO contents of the system after the reaction in step (3) by a high-performance liquid chromatograph and a gas chromatograph.

[0063] Example 3

[0064] (1) Take 0.2 g of xylose, 20.0 mL of KOH solutions with different concentrations (0.05, 0.1, 0.5, 2.0, and 3.0 mol / L respectively), and 25 mg of the CNs@PY53 photocatalyst prepared in Example 1 and add them to a pressure-resistant bottle;

[0065] (2) Seal the system in step (1) and add a magnetic stir bar, and stir for 30 min under dark conditions;

[0066] (3) After sealing the system in step (2), carry out a photocatalytic reaction under illumination at 40 °C for 4.0 h by a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s);

[0067] (4) Determine the lactic acid and CO contents of the system after the reaction in step (3) by high-performance liquid chromatography and gas chromatography.

[0068] Example 4

[0069] (1) Take 0.2 g of xylose, 20.0 mL of 0.5 mol / L KOH solution, and 25 mg of the CNs@PY53 photocatalyst prepared in Example 1 and add them to a pressure-resistant bottle;

[0070] (2) Seal the system in step (1) and add a magnetic stir bar, and stir for 30 min under dark conditions;

[0071] (3) After sealing the system in step (2), carry out a photocatalytic reaction under illumination at 30, 50, 60, and 70 °C for 4.0 h respectively by a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s);

[0072] (4) Determine the lactic acid and CO contents of the system after the reaction in step (3) by high-performance liquid chromatography and gas chromatography.

[0073] Example 5

[0074] (1) Take 0.2 g of xylose, 20.0 mL of 0.5 mol / L KOH solution, and 25 mg of the CNs@PY53 photocatalyst prepared in Example 1 and add them to a pressure-resistant bottle;

[0075] (2) Seal the system in step (1), add a magnetic stir bar, and stir for 30 min under dark conditions;

[0076] (3) After sealing the system in step (2), irradiate and react for 0.5, 1.0, 2.0, 5.0, and 6.0 h respectively at 50 °C through a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s);

[0077] (4) Measure the lactic acid and CO contents of the system after the reaction in step (3) by high performance liquid chromatography and gas chromatography.

[0078] Example 6

[0079] (1) Filter the system after reacting for 5.0 h in Example 5 to obtain the CNs@PY53 photocatalyst, centrifuge, wash with deionized water until neutral, and dry overnight;

[0080] (2) Take 0.2 g of xylose, 20.0 mL of a KOH solution with a concentration of 0.5 mol / L, and 25 mg of the CNs@PY53 photocatalyst obtained in step (1) and add them to a pressure-resistant bottle;

[0081] (3) Seal the system in step (2), add a magnetic stir bar, and stir for 30 min under dark conditions;

[0082] (4) Irradiate and react the system in step (3) at 50.0 °C through a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s) for 5.0 h;

[0083] (5) Measure the lactic acid and CO contents of the system after the reaction in step (4) by high performance liquid chromatography and gas chromatography;

[0084] (6) Filter the sample after the test in step (5) to obtain the recycled CNs@PY53 photocatalyst, centrifuge, wash with deionized water until neutral, dry overnight, and then repeat the above steps (2) to (5) for the recycled CNs@PY53 photocatalyst for 5 cycles.

[0085] Example 7

[0086] (1) Take 0.2 g of different biomass-based monosaccharides (arabinose, fructose, rhamnose, glucose, mannose respectively), 20.0 mL of KOH solution with a concentration of 0.5 mol / L, and 25 mg of the CNs@PY53 photocatalyst prepared in Example 1 and add them to a pressure-resistant bottle;

[0087] (2) Seal the system in step (1), add a magnetic stir bar, and stir for 30 min under dark conditions;

[0088] (3) After sealing the system in step (2), carry out a photocatalytic reaction under illumination at 50 °C through a Perfectlight PCX 50C multi-channel photocatalytic reaction system (size specification: 320L * 320W * 400H, LED light source, wavelength 420 nm, power 5W, stirring speed 200 rpm / min, unit switching interval 30 s) for 5.0 h;

[0089] (4) Determine the lactic acid and CO contents of the system after the reaction in step (3) by high-performance liquid chromatography and gas chromatography.

[0090] Figure 1 is the XRD pattern of the CNs@PY53 catalyst, where a is the CNs@PY53 catalyst obtained after step (8) in Example 1, b is titanium nickel yellow, and c is the carbon nitride quantum dots obtained in step (6) of Example 1. It can be seen from the figure that the pattern of the CNs@PY53 photocatalyst is very similar to that of pure titanium nickel yellow, and the characteristic peaks representing the (110), (101), (111), (211), (220), and (301) crystal planes of titanium nickel yellow all appear, indicating that the introduction of carbon nitride quantum dots does not affect the crystallinity of titanium nickel yellow.

[0091] Figure 2 is the influence diagram of different catalyst dosages of the CNs@PY53 photocatalyst on the simultaneous production of lactic acid and CO from biomass-based monosaccharides in Example 2, where the line graph represents the lactic acid yield and the bar graph represents the CO evolution rate. The dosages of the CNs@PY53 photocatalyst in Example 2 are set to 5 mg, 10 mg, 15 mg, 20 mg, 25 mg, and 30 mg respectively. It is found that with the increase of the catalyst dosage, the lactic acid yield and CO evolution rate first increase and then decrease, and reach the maximum value at 25 mg. The reason for the decrease in the lactic acid yield and CO evolution rate may be that the light scattering and refraction caused by the excessive catalyst reduce the photocatalytic efficiency of the catalyst.

[0092] Figure 3Figure showing the effects of different KOH concentrations in Example 2 and Example 3 on the photocatalytic production of lactic acid and CO from biomass-based monosaccharides by the CNs@PY53 photocatalyst. The line graph represents the lactic acid yield, and the bar graph represents the CO evolution rate. In Example 3, the KOH concentrations are 0.05, 0.1, 0.5, 2.0, and 3.0 M, and in Example 2, the KOH solution is 1.0 M and the photocatalyst dosage is 25 mg. It can be seen that as the KOH concentration increases, the lactic acid yield gradually increases. This may be because more hydroxide ions are adsorbed on the catalyst surface at high alkali concentrations, which is beneficial to the generation of hydroxyl radicals, thus promoting the formation of lactic acid. At the same time, as the KOH concentration increases, the CO evolution rate first increases and then decreases, reaching the maximum value at a KOH concentration of 0.5 M. This may be because glyceraldehyde is first produced during the conversion of xylose to CO, and too high an alkali concentration will reduce the oxidation activity of glyceraldehyde, resulting in a decrease in the CO evolution rate.

[0093] Figure 4 Figure showing the effects of different reaction temperatures in Example 3 and Example 4 on the photocatalytic production of lactic acid and CO from biomass-based monosaccharides by the CNs@PY53 photocatalyst. The line graph represents the lactic acid yield, and the bar graph represents the CO evolution rate. In Example 4, the reaction temperatures are 30, 50, 60, and 70 °C, and in Example 3, the KOH solution concentration is 0.5 M and the reaction temperature is 40 °C. It was found that as the reaction temperature increases, both the CO evolution rate and the lactic acid yield show a trend of first increasing and then decreasing. Among them, the CO evolution rate is the highest at 50 °C, and the lactic acid yield is the highest at 60 °C. This may be because as the reaction temperature increases, some lactic acid and CO are converted into other by-products during the reaction process.

[0094] Figure 5 Figure showing the effects of different reaction times in Example 4 and Example 5 on the photocatalytic production of lactic acid and CO from biomass-based monosaccharides by the CNs@PY53 photocatalyst. The line graph represents the lactic acid yield, and the bar graph represents the CO evolution rate. In Example 5, the reaction times are set to 0.5, 1.0, 2.0, 5.0, and 6.0 h, and in Example 4, the reaction temperature is 50 °C and the reaction time is 4.0 h. From Figure 5 It can be seen that as the reaction time increases, the lactic acid yield and the CO evolution rate also increase and gradually tend to level off. This shows that appropriately extending the reaction time is beneficial to the conversion of xylose.

[0095] Figure 6 Figure showing the catalyst recyclability of the CNs@PY53 photocatalyst for the photocatalytic production of lactic acid and CO from biomass-based monosaccharides in Example 6. The line graph represents the lactic acid yield, and the bar graph represents the CO evolution rate. From Figure 6It can be seen that after 5 cycles, the yields of lactic acid and the evolution rate of CO still remained at a relatively high level. The lactic acid yield and the CO evolution rate after 5 cycles were 94.4% and 92.1% of those in the first cycle, respectively, and the reaction activity hardly changed. This indicates that the CNs@PY53 photocatalyst can still ensure a high catalytic efficiency during multiple recycling processes, with high recyclability and excellent stability.

[0096] Figure 7 Figure showing the effects of different biomass-based monosaccharides in Example 5 and Example 7 on the photocatalytic synchronous production of lactic acid and CO by the CNs@PY53 photocatalyst. The line graph represents the lactic acid yield, and the bar graph represents the CO evolution rate. In Example 7, the biomass-based monosaccharides were arabinose, fructose, rhamnose, glucose, and mannose, and in Example 5, the biomass-based monosaccharide was xylose and the reaction time was 5.0 h. From Figure 7 It can be seen that in different biomass-based monosaccharide systems, the yields of lactic acid and the evolution rate of CO both remained at a relatively high level, indicating that CNs@PY53 has good application universality. Among them, the lactic acid yield and the CO evolution rate of pentoses were slightly higher than those of hexoses, indicating that the formation of lactic acid and CO is more favorable in the pentose system.

[0097] The above embodiments are part of the implementation process of the present invention, but the implementation manners of the present invention are not limited by the above embodiments. Any other changes, substitutions, combinations, and simplifications made contrary to the spirit and principle of the present invention shall be equivalent replacement manners and are all included in the protection scope of the present invention.

Claims

1. A preparation method of CNs@PY53 photocatalyst for photocatalytic synchronous production of lactic acid and CO, characterized in that, It includes the following steps: (1) Anneal urea in a tubular furnace at 400 - 600 °C for 2 - 6 h in an N₂ atmosphere, and cool it naturally to obtain CN; (2) Disperse CN into concentrated hydrochloric acid, stir it in a water bath at 80 - 90 °C for 20 - 30 h to obtain a suspension, filter and wash it to obtain a solid product; (3) Disperse the solid product obtained in step (2) into deionized water, and ultrasonically treat it for 20 - 30 h to obtain a dispersion; (4) Filter the dispersion obtained in step (3) through a 0.22 - 0.45 μm aqueous filter membrane, and freeze-dry it at -40 - -60 °C for 36 - 48 h to obtain CNs; (5) Disperse the CNs and PY53 obtained in step (4) into absolute ethanol, and ultrasonically treat it for 0.5 - 3.0 h to obtain a dispersion; the mass ratio of CNs to PY53 is 0.005 - 1.0:0.5 - 3.0; (6) Evaporate and dry the dispersion obtained in step (5) at 75 - 95 °C for 2 - 4 h to obtain the CNs@PY53 photocatalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), before use, place urea in a crucible, heat it to 70 - 90 °C and keep it for 1 - 2 h.

3. The preparation method according to claim 1, wherein In step (2), the ratio of CN to concentrated hydrochloric acid is 2.0 - 10.0 g:20 - 100 mL; in step (3), the ratio of the solid product to deionized water is 2.0 - 10.0 g:50 - 500 mL; in step (5), the ratio of CNs to absolute ethanol is 0.005 - 1.0:2 - 80 mL.

4. The preparation method according to claim 1, characterized in that, In step (2), dilute the suspension with deionized water and then filter it, and wash the obtained solid with deionized water until it is neutral.

5. The preparation method according to claim 1, wherein In step (4), the aqueous filter membrane is a polytetrafluoroethylene filter membrane, a nylon filter membrane, a mixed cellulose filter membrane or a polyethersulfone filter membrane.

6. Application of the CNs@PY53 photocatalyst obtained by the preparation method according to any one of claims 1 - 5 in photocatalytically synchronous production of lactic acid and CO.

7. The application according to claim 6, wherein Mix the CNs@PY53 photocatalyst, an alkaline solution and a biomass-based monosaccharide evenly, and carry out a photocatalytic reaction at 20.0 - 80.0 °C for 0.5 - 8.0 h.

8. The application according to claim 7, wherein The alkaline solution is a water-soluble alkaline solution, and the concentration of the alkaline solution is 0.05 - 3.0 mol / L.

9. The application according to claim 7, wherein The biomass-based monosaccharide is xylose, arabinose, fructose, rhamnose, mannose or glucose.

10. The application according to claim 7, wherein The ratio of the CNs@PY53 photocatalyst, the biomass-based monosaccharide and the alkaline solution is 0.05 - 30 mg:0.01 - 1.0 g:20 - 100 mL.

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