A Nb-based single-atom catalyst for preparing hexadecane from palmitic acid and its preparation method

Abstract

The present invention belongs to the field of biomass energy utilization and relates to a Nb-based single-atom catalyst for the production of hexadecane from palmitic acid and its preparation method. The catalyst is synthesized hydrothermally using a co-complexation strategy of ammonium niobium oxalate and chloroplatinic acid to introduce platinum atoms into the niobium oxide framework. Although the added platinum level is only 0.54%, it exhibits excellent selectivity and activity. The catalyst effectively inhibits decarboxylation side reactions, reduces the production of byproducts such as carbon dioxide, and improves selectivity for long-chain alkanes. The palmitic acid hydrodehydration reaction method using this catalyst can achieve high selectivity and high conversion of hexadecane under specific reaction conditions (such as temperature, pressure, reaction time, and catalyst-to-substrate mass ratio). The catalyst and method of the present invention have important application value for biomass energy utilization and reducing carbon dioxide emissions, particularly in the production of long-chain alkanes such as diesel and aviation fuel.

Description

Technical Field

[0001] The invention belongs to the field of biomass energy utilization and relates to a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid and a preparation method thereof. Background Art

[0002] Fatty acid hydrodeoxygenation is a key step in extracting renewable fuels from biomass, particularly in the production of long-chain alkanes (such as diesel and aviation fuel). However, conventional hydrodeoxygenation catalysts often induce side reactions during the reaction, particularly decarboxylation, which leads to carbon chain breakage and the production of large amounts of carbon dioxide and short-chain alkanes. These byproducts not only reduce the selectivity of long-chain alkanes but also result in unnecessary carbon loss, negatively impacting the economic and environmental performance of the process.

[0003] In recent years, noble metal catalysts such as palladium (Pd), platinum (Pt), and ruthenium (Ru) have demonstrated excellent activity and selectivity in hydrodeoxygenation reactions. However, their high price and scarcity have limited their large-scale application. In contrast, niobium oxide (Nb2O5) has become a research hotspot as a catalyst support due to its excellent chemical stability and water resistance. In particular, when loaded with single-atom platinum (Pt) active sites on its surface, this catalyst can inhibit decarboxylation and prevent carbon chain scission, thereby improving selectivity for long-chain alkanes and reducing carbon dioxide production. However, research on Nb-based single-atom catalysts is limited, particularly for efficient hydrodeoxygenation of fatty acids. Summary of the Invention

[0004] The present invention aims to provide a niobium oxide-supported single-atom platinum catalyst for the efficient hydrodeoxygenation of fatty acids. The catalyst's innovation lies in the hydrothermal synthesis of Pt atoms into the Nb oxide framework via a co-complexation strategy involving ammonium niobium oxalate and chloroplatinic acid. Despite a Pt loading of only 0.54%, the catalyst exhibits excellent selectivity and activity. While maintaining high deoxygenation performance, the catalyst effectively suppresses side reactions (such as decarboxylation) and significantly reduces the formation of byproducts such as carbon dioxide.

[0005] The technical solutions provided by the present invention are as follows:

[0006] A method for preparing a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid comprises the following steps: adding a hexadecyltrimethylammonium bromide solution and a chloroplatinic acid solution dropwise to an ammonium niobium oxalate solution, stirring and mixing the mixture, subjecting the mixture to a hydrothermal reaction, washing the product, filtering it with suction, and drying it; performing Soxhlet extraction, and then washing it with methanol reflux; drying the product, and calcining it in a muffle furnace to obtain the Nb-based single-atom catalyst for preparing hexadecane from palmitic acid.

[0007] Specifically, the cetyltrimethylammonium bromide solution, the chloroplatinic acid precursor, and the niobium oxalate are mixed with CTAB and then added into the hydrothermal reactor.

[0008] Furthermore, the temperature of the hydrothermal reaction is 160-200° C., and the reaction time is 24 h.

[0009] Furthermore, the calcination temperature is 350-550°C.

[0010] Furthermore, the heating rate of the calcination is 0.8~1.2℃ / min.

[0011] Furthermore, the template agent is a cationic surfactant cetyltrimethylammonium bromide.

[0012] The present invention also provides a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid, which is prepared by the above-mentioned preparation method.

[0013] The present invention also provides the use of the catalyst in fatty acid hydrodeoxygenation reaction, wherein the catalyst and palmitic acid are placed in a high-pressure reactor, and high-purity hydrogen is used to replace the gas in the reactor.

[0014] Furthermore, the reaction solvent is n-decane.

[0015] Furthermore, the hydrodeoxygenation reaction is carried out at 180-260° C. for 1-8 hours.

[0016] Furthermore, after the gas in the reactor is replaced with high-purity hydrogen, the pressure in the reactor is maintained at 0.1~3MPa.

[0017] Furthermore, the mass ratio of the catalyst to palmitic acid is 1:1-10.

[0018] Beneficial effects

[0019] This invention uses a co-complexation approach to prepare a highly efficient, low-loading, high-activity Nb-based single-atom catalyst for the conversion of palmitic acid to hexadecane. The catalyst exhibits low cracking at relatively high temperatures. At 240°C and 3 MPa, the pentadecane yield is only 1.3%. At low temperatures, it exhibits excellent hexadecane selectivity, conversion, and yield. At 240°C and 3 MPa, the preferred catalyst, 0.5%wt Pt-Nb2O5·H2O-350, achieved a hexadecane yield of 87.3%, an 85% increase over a commercial 5%wt Pt / C catalyst. Compared to a 2%wt Pt / Nb2O5·H2O-350 catalyst prepared by an impregnation method, the hexadecane yield increased by 34.2%. Compared to a 2%wt Pt-Nb2O5·H2O catalyst (P123) prepared using the nonionic surfactant P123, the hexadecane yield increased by 39.2%. The catalyst maintains high activity after multiple reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The XRD patterns of the catalyst with and without metal introduction and after high temperature calcination;

[0021] Figure 2 This is the SEM of the catalyst with 0.5wt% Pt content; ad and il are micromorphologies, and fh and nq are mappings;

[0022] Figure 3 This is the TEM of the catalyst with 0.5 wt% Pt content;

[0023] Figure 4 This is the TEM of the catalyst with 0.5 wt% Pt content after the reaction;

[0024] Figure 5 This is a high-resolution spherical aberration electron microscope of a catalyst with 0.5wt% Pt content;

[0025] Figure 6 These are the adsorption-desorption curves of the catalyst with 0.5 wt% Pt content and the catalyst without metal;

[0026] Figure 7 This is the pore size distribution curve of the catalyst with 0.5wt% Pt content. DETAILED DESCRIPTION

[0027] The following is a further description of the present invention, but not a limitation of the present invention.

[0028] A Nb-based single-atom catalyst for preparing hexadecane from palmitic acid, the preparation method comprising the following steps:

[0029] Step 1. Dissolve 0.1 mol of ammonium niobium oxalate in 100 mL of deionized water heated to 75°C, referred to as solution A.

[0030] Step 2. Dissolve 2 g of CTAB (cetyltrimethylammonium bromide) in deionized water heated to 35°C (Solution B).

[0031] Step 3. Dissolve a specified amount of chloroplatinic acid (0.5-1 wt% loading, calculated by weighing the support mass of a parallel group of pre-calcined supports without metal addition) in 5 mL of deionized water, referred to as solution C.

[0032] Step 4. Add solution B (transparent solution) and solution C, which have been stirred for a while, dropwise into solution A and stir vigorously for a while.

[0033] Step 5. After stirring, transfer to a hydrothermal reactor and perform hydrothermal reaction at 180°C for 24 hours.

[0034] Step 6. Wash and filter the hydrothermal catalyst, then dry it in an oven at 60°C for 12 hours.

[0035] Step 7. The dried solid was refluxed and washed in a Soxhlet extractor for 48 hours, with methanol as the reflux solvent.

[0036] Step 8. The catalyst after reflux washing is placed in an oven at 60°C for drying.

[0037] Step 9. The dried catalyst is placed in a muffle furnace and calcined at a temperature of 350° C. to obtain a Pt-Nb2O5·H2O catalyst.

[0038] The amount of CTAB used in step 2 was 1 g, 3 g, or 5 g, with 3 g being the most preferred. For comparison, a comparative catalyst was prepared using a nonionic surfactant P123 (polyoxypropylene polyoxyethylene copolymer) instead of CTAB.

[0039] In step 3, different amounts of active metal were added, with loadings of 0.3 wt%, 0.5 wt%, 0.7 wt%, and 0.9 wt%, respectively. The reaction was carried out at 240°C, 3 MPa, and 4 hours.

[0040] In step 7, the catalyst Soxhlet extraction can be performed using ethanol or methanol, with methanol being most preferred.

[0041] The calcination temperature of the catalyst in step 9 is 350°C, and the heating rate is 1°C / min. In particular, the catalyst without metal addition is amorphous, and the catalyst with metal addition is between crystalline and amorphous. Figure 1 For XRD.

[0042] The catalyst has a platinum loading of 0.54% and exhibits excellent selectivity and activity.

[0043] The physical property parameters of the preferred catalyst are shown in the following table:

[0044]

[0045] according to Figure 2 SEM observation shows that the rod-like units are interpenetrated to form grid-shaped slit holes. Figure 6 The adsorption-desorption curves show that this pore structure becomes more obvious after the introduction of Pt. Figure 7 is the pore size distribution curve. The average pore size of the catalyst is 12nm, which belongs to the mesoporous category.

[0046] The metal dispersion and particle size of the preferred catalyst are shown in the following table:

[0047]

[0048] Although Figure 3Pt nanoclusters of about 3 nm were observed in TEM, but Figure 5 The medium spherical aberration electron microscope EDS can clearly show the uniform dispersion of Pt on the carrier skeleton.

[0049] The metal contents of the preferred catalysts are shown in the following table:

[0050]

[0051] Palmitic acid hydrogenation dehydration reaction:

[0052] Step 1. Weigh a certain amount of palmitic acid as a model compound. Weigh a certain amount of catalyst, with the mass ratio of reaction substrate to catalyst being 1:1-1:10.

[0053] Step 2. Use 10 ml of n-decane as the reaction solvent. Add the material from step 1 into a micro autoclave.

[0054] Step 3. Replace the gas in the high-pressure reaction with hydrogen at pressures of 0.1, 1, 2, 3, and 4 MPa.

[0055] Step 4: carrying out a hydrogenation dehydration reaction at a temperature of 180-260°C.

[0056] Step 5. After the reaction is completed, the product is qualitatively and quantitatively analyzed by gas chromatography.

[0057] Example 1

[0058] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.5 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.5%wtPt-Nb2O5·H2O-350 catalyst was obtained.

[0059] Catalyst Evaluation: 0.5%wt Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane was 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 87.3%.

[0060] Example 2

[0061] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.5 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the solution was transferred to a hydrothermal reactor and hydrothermally reacted at 160°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.5%wtPt-Nb2O5·H2O-350 catalyst was obtained.

[0062] Catalyst Evaluation: 0.5%wt Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 71.2%.

[0063] Example 3

[0064] Catalyst Preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.5 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group that had been pre-calculated without metal addition. After stirring for a while, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the solution was transferred to a hydrothermal reactor and hydrothermally reacted at 200°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.5%wtPt-Nb2O5·H2O-350 catalyst was obtained.

[0065] Catalyst Evaluation: 0.5%wt Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 60.8%.

[0066] Example 4

[0067] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.3 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.3Pt-Nb2O5·H2O-350 catalyst was obtained.

[0068] Catalyst Evaluation: 0.3% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 68.4%.

[0069] Example 5

[0070] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.5 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group that had been pre-calculated without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the solution was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 450°C for 6 hours. 0.5Pt-Nb2O5·H2O-450 catalyst was obtained.

[0071] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-450 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 1.6%.

[0072] Example 6

[0073] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.5 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 550°C for 6 hours. 0.5Pt-Nb2O5·H2O-550 catalyst was obtained.

[0074] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-550 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 5.4%.

[0075] Example 7

[0076] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.7 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group that had been pre-calculated without metal addition. After stirring for a while, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.7Pt-Nb2O5·H2O-350 catalyst was obtained.

[0077] Catalyst Evaluation: 0.7% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane was 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 86.8%.

[0078] Example 8

[0079] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). CTAB was dissolved in deionized water heated to 35°C (Solution B). A 0.9 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a period of time, Solution B and Solution C were simultaneously added dropwise to Solution A. After vigorous stirring for a period of time, the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 0.9Pt-Nb2O5·H2O-350 catalyst was obtained.

[0080] Catalyst Evaluation: 0.9% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane was 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 87.1%.

[0081] Example 9

[0082] Catalyst preparation: Same as Example 1

[0083] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a micro-autoclave at mass ratios of 1:1, 1:2, 1:3, 1:4, 1:5, and 1:10. The reaction was then replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yields of hexadecane were 86.8%, 86.4%, 86.6%, 86.7%, 87.3%, and 35.7%, respectively.

[0084] Example 10

[0085] Catalyst preparation: Same as Example 1

[0086] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining pressures of 0.1, 1, 2, and 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yields of hexadecane were 31.8%, 51.2%, 68.3%, and 87.3%, respectively.

[0087] Example 11

[0088] Catalyst preparation: Same as Example 1

[0089] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:10 mass ratio in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 1, 2, 3, 4, 6, and 8 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yields of hexadecane were 10.3%, 11.2%, 30.2%, 35.7%, 58.6%, and 82.2%, respectively.

[0090] Example 12

[0091] Catalyst preparation: Same as Example 1

[0092] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. Reactions were carried out at 180°C, 200°C, 220°C, 240°C, and 260°C for 4 hours. After the reaction, the product yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yields of hexadecane were 5.1%, 17.9%, 61.6%, 87.3%, and 86.4%, respectively. The mass yields of pentadecane were 1.4%, 2.6%, 1.8%, 1.3%, and 2.2%, respectively.

[0093] Example 13

[0094] Catalyst preparation: Same as Example 1

[0095] Catalyst Evaluation: 0.5% Pt-Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:10 mass ratio in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane was 88.3%) was analyzed by gas chromatography. After 25 reactions, the selectivity of palmitic acid remained at 99.1%.

[0096] Comparative Example 1

[0097] Catalyst: Commercial Pd / C catalyst with a loading of 5 wt%.

[0098] Catalyst Evaluation: 0.5%wt Pd / C catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 2.3%.

[0099] Comparative Example 2

[0100] Catalyst preparation: Solution A was prepared by dissolving 0.1 mol of ammonium niobium oxalate in 100 mL of deionized water heated to 75°C. Solution B was prepared by dissolving CTAB in deionized water heated to 35°C. Solution C was prepared by dissolving 2 wt% chloroplatinic acid in 5 mL of deionized water. The loading was calculated by weighing the support mass in a parallel group that had been pre-calculated without metal addition. Solution B was hydrothermally reacted at 180°C for 24 hours. The catalyst was washed and filtered after hydrothermal reaction and then dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. The Nb2O5·H2O-350 catalyst was obtained, and the Nb2O5·H2O-350 catalyst was placed in the C solution and stirred at 75°C for 24 hours to obtain 2%wt Pt / Nb2O5·H2O-350.

[0101] Catalyst Evaluation: 2%wt Pt / Nb2O5·H2O-350 catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane was 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 53.1%.

[0102] Comparative Example 3

[0103] Catalyst preparation: 0.1 mol of ammonium niobium oxalate was dissolved in 100 mL of deionized water heated to 75°C (Solution A). P123 was dissolved in deionized water heated to 35°C (Solution B). A 2 wt% loading of chloroplatinic acid was dissolved in 5 mL of deionized water (Solution C). The loading was calculated by weighing the support mass in a parallel group pre-calcined without metal addition. After stirring for a while, Solution B and Solution C were added dropwise to Solution A. After vigorous stirring for a period of time, the solution was transferred to a hydrothermal reactor and hydrothermally reacted at 180°C for 24 hours. The catalyst was washed, filtered, and dried in a 60°C oven for 12 hours. The dried solid was then reflux-washed in a Soxhlet extractor for 48 hours in methanol. The washed catalyst was then oven-dried at 60°C. The dried catalyst was then calcined in a muffle furnace at a rate of 1°C / min to 350°C for 6 hours. 2%wt Pt-Nb2O5·H2O (P123) catalyst was obtained.

[0104] Catalyst Evaluation: 2%wt Pt-Nb2O5·H2O (P123) catalyst and palmitic acid were weighed in a 1:5 mass ratio and placed in a micro-autoclave. The atmosphere was replaced ten times with high-purity hydrogen while maintaining a pressure of 3 MPa. The reaction was carried out at 240°C for 4 hours. After the reaction, the product mass yield (theoretical yield of n-hexadecane is 88.3%) was analyzed by gas chromatography. The mass yield of hexadecane was 48.1%.

Claims

1. A method for preparing a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid, characterized in that: A hexadecyltrimethylammonium bromide solution and a chloroplatinic acid solution are added dropwise to an ammonium niobium oxalate solution, and after thorough stirring and mixing, the mixed solution is subjected to a hydrothermal reaction. The product is washed, filtered, and then dried. After Soxhlet extraction, the product is reflux-washed with methanol. The product is dried and calcined in a muffle furnace to obtain a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid.

2. The method for preparing a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid according to claim 1, wherein: The temperature of the hydrothermal reaction is 160-200° C., and the reaction time is 24 h.

3. The method for preparing a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid according to claim 1, wherein: The calcination temperature is 350-550°C.

4. The method for preparing a Nb-based single-atom catalyst for preparing hexadecane from palmitic acid according to claim 3, wherein: The heating rate of calcination is 0.8~1.2℃ / min.

5. A Nb-based single-atom catalyst for preparing hexadecane from palmitic acid, characterized in that: Prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the catalyst according to claim 5 in the hydrodeoxygenation reaction of fatty acids, characterized in that: The catalyst and palmitic acid are placed in a high-pressure reactor, and high-purity hydrogen is used to replace the gas in the reactor.

7. The use according to claim 6, characterized in that The reaction solvent is n-decane.

8. The use according to claim 6, characterized in that The hydrodeoxygenation reaction is carried out at 180-260° C. for 1-8 hours.

9. The use according to claim 6, characterized in that After replacing the gas in the reactor with high-purity hydrogen, the pressure in the reactor is maintained at 0.1~3MPa.

10. The use according to claim 6, characterized in that The mass ratio of the catalyst to palmitic acid is 1:1~10.

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