A phosphorus-doped carbon supported molybdenum phosphide catalyst, a preparation method and application thereof

Abstract

The application belongs to the technical field of preparing carbon monoxide from formic acid, and provides a phosphorus-doped carbon-supported molybdenum phosphide catalyst, a preparation method and application thereof. The preparation method comprises the following steps: mixing ammonium molybdate, ammonium dihydrogen phosphate, a saccharide polymer, diammonium hydrogen phosphate and water to obtain a mixed solution, drying the mixed solution to obtain a precursor, and pyrolyzing the precursor under a protective atmosphere to obtain the phosphorus-doped carbon-supported molybdenum phosphide catalyst. The phosphorus-doped carbon-supported molybdenum phosphide catalyst is prepared by using a one-step pyrolysis method, the process is simple and safe, a saccharide which is low in cost is used as a catalyst carrier precursor, the catalyst is low in cost, widely available, and easy to separate, and is suitable for large-scale industrial production. The catalyst is used for preparing carbon monoxide by dehydrating pure formic acid at low temperature in a liquid phase, belongs to a heterogeneous and non-noble metal catalyst, and has the characteristics of high gas production rate, low reaction temperature, high carbon monoxide selectivity and the like.

Description

Technical Field

[0001] This invention relates to the field of formic acid preparation of carbon monoxide, and particularly to a phosphorus-doped carbon-supported molybdenum phosphide catalyst, its preparation method, and its application. Background Technology

[0002] Carbon monoxide is an important chemical raw material and energy material. High-purity carbon monoxide is currently used in lasers, pharmaceutical intermediates, and semiconductor processes. Currently, the industrial synthesis of carbon monoxide generally requires high temperature and high pressure conditions, as well as separation and purification. How to efficiently generate high-purity carbon monoxide under mild conditions has attracted widespread attention from industry and researchers.

[0003] Formic acid can be used as a liquid CO support (60.8 wt.%) to prepare high-purity carbon monoxide (HCOOH→CO+H2O) via dehydration. Furthermore, the liquid-phase carbon monoxide support is compatible with existing transport pipelines and facilities, and can be prepared on demand, greatly simplifying the preparation process. Compared to formic acid dehydrogenation, research on formic acid dehydration to produce carbon monoxide is still limited, mainly focusing on gas-phase dehydration. Formic acid dehydration catalysts are mostly metal oxides, and the selectivity of the catalyst is adjusted by regulating the acidity of the metal oxide crystal facets. Haksoo Han et al. reported a zirconium oxide catalyst (Production of H2-free CO by decomposition of formic acid over ZrO2 catalysts. Applied Catalysis A: General 531 (2017) 13–20) that efficiently produces high-purity carbon monoxide at temperatures >215℃. The report pointed out that the catalyst surface... The strength of acidic sites plays a crucial role in the dehydration of formic acid. Yasuhiro Iwasawa et al. (Oxygen Vacancy Promoting Catalytic Dehydration of Formic Acid on TiO2(110) by in Situ Scanning Tunneling Microscopic Observation. J. Phys. Chem. B 2005, 109, 18831-18838) studied the titanium dioxide-catalyzed gas-phase decomposition of formic acid and found that oxygen vacancies can effectively promote the dehydration of formic acid to carbon monoxide. All of the above catalytic reactions are carried out under gas-phase conditions, which limits their practical application prospects and restricts the commercial application of formic acid to carbon monoxide.

[0004] As early as 1821, Doebereiner (J. Chem. Phys., 32, 345 (1821)) first discovered that carbon monoxide could be prepared in liquid form by co-bathing formic acid and concentrated sulfuric acid. However, this method not only requires the use of highly dangerous strong acids, but also makes the start and end of the reaction difficult to control, resulting in a low gas production rate and the presence of sulfur oxides in the gaseous products. Currently, transition metal catalysts have been studied and applied to various reactions, among which molybdenum-based catalysts have shown good catalytic prospects. Molybdenum phosphide, due to its d-band structure similar to noble metals and its easily tunable electronic structure, is considered one of the most promising alternatives to noble metal catalysts (Energy Environ. Sci. 2020, 13, 4564).

[0005] Therefore, the development of a phosphorus-doped carbon-supported molybdenum phosphide catalyst for the preparation of high-purity carbon monoxide from liquid-phase formic acid is of great significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a phosphorus-doped carbon-supported molybdenum phosphide catalyst, its preparation method and application, filling the gap in the catalytic decomposition of pure formic acid to carbon monoxide by non-precious metal heterogeneous catalysts.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a phosphorus-doped carbon-supported molybdenum phosphide catalyst, comprising the following steps:

[0009] 1) Ammonium molybdate, ammonium dihydrogen phosphate, carbohydrates, diammonium hydrogen phosphate and water are mixed to obtain a mixture, which is then dried to obtain the precursor;

[0010] 2) The precursor was pyrolyzed under a protective atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0011] Preferably, the mass ratio of ammonium molybdate, ammonium dihydrogen phosphate, carbohydrate compound, diammonium hydrogen phosphate and water in step 1) is 2-3:2-3:5-9:1-2:10-30.

[0012] Preferably, the carbohydrate compound in step 1) is sucrose and / or glucose.

[0013] Preferably, the drying temperature in step 1) is 70–120°C, and the drying time is 8–14 hours.

[0014] Preferably, the protective atmosphere in step 2) is an argon atmosphere, a nitrogen atmosphere, or a helium atmosphere.

[0015] Preferably, the pyrolysis temperature in step 2) is 750–850°C, and the pyrolysis time is 2–3 hours.

[0016] The present invention also provides a phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared by the aforementioned preparation method.

[0017] The present invention also provides the application of the aforementioned phosphorus-doped carbon-supported molybdenum phosphide catalyst in the preparation of carbon monoxide from liquid-phase formic acid.

[0018] The beneficial effects of this invention include:

[0019] 1) The phosphorus-doped carbon-supported molybdenum phosphide catalyst of the present invention is applied for the first time to the dehydration of liquid-phase pure formic acid to prepare high-purity carbon monoxide, avoiding the additional energy consumption in the traditional gas-phase catalysis process and having prospects for industrial application; Unlike the catalysts for formic acid dehydration in the prior art, the method of the present invention achieves the selective dehydration of liquid-phase pure formic acid to prepare high-purity carbon monoxide by element doping to regulate the catalyst physicochemically, and has good activity and dehydration selectivity, and long service life.

[0020] 2) This invention uses a one-step pyrolysis method to prepare phosphorus-doped carbon-supported molybdenum phosphide catalyst. The process is simple and safe, and uses low-cost sugars as catalyst support precursors. The catalyst is low in cost, widely available, and easy to separate, making it suitable for large-scale industrial production.

[0021] 3) The catalyst of the present invention is used for the dehydration of pure formic acid in the low-temperature liquid phase to prepare carbon monoxide. It is a heterogeneous, non-precious metal catalyst with the characteristics of high gas production rate, low reaction temperature and high carbon monoxide selectivity. It opens up a new field of using non-precious metal heterogeneous catalysts to decompose pure formic acid in the liquid phase to prepare carbon monoxide. Attached Figure Description

[0022] Figure 1 The XRD pattern of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1;

[0023] Figure 2 SEM image of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1;

[0024] Figure 3 The image shows the EDS-mapping diagram of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1. Detailed Implementation

[0025] This invention provides a method for preparing a phosphorus-doped carbon-supported molybdenum phosphide catalyst, comprising the following steps:

[0026] 1) Ammonium molybdate, ammonium dihydrogen phosphate, carbohydrates, diammonium hydrogen phosphate and water are mixed to obtain a mixture, which is then dried to obtain the precursor;

[0027] 2) The precursor was pyrolyzed under a protective atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0028] In this invention, the preferred mass ratio of ammonium molybdate, ammonium dihydrogen phosphate, carbohydrate compound, diammonium hydrogen phosphate and water in step 1) is 2-3:2-3:5-9:1-2:10-30, more preferably 2.2-2.8:2.2-2.8:6-8:1.2-1.8:15-25, and even more preferably 2.4-2.5:2.4-2.5:7:1.4-1.5:18-20.

[0029] In this invention, the mixture obtained by mixing ammonium molybdate, ammonium dihydrogen phosphate, saccharide polymer, diammonium hydrogen phosphate and water is a clear solution.

[0030] In this invention, the carbohydrate compound in step 1) is preferably sucrose and / or glucose.

[0031] In this invention, the drying temperature in step 1) is preferably 70-120°C, more preferably 80-100°C, and even more preferably 90-95°C; the drying time is preferably 8-14 hours, more preferably 9-12 hours, and even more preferably 10-11 hours.

[0032] In this invention, the protective atmosphere in step 2) is preferably an argon atmosphere, a nitrogen atmosphere, or a helium atmosphere.

[0033] In this invention, the pyrolysis temperature in step 2) is preferably 750–850°C, more preferably 770–820°C, and even more preferably 790–800°C; the pyrolysis time is preferably 2–3 h, and even more preferably 2.5 h.

[0034] In this invention, after pyrolysis, the catalyst is naturally cooled under a protective atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0035] The present invention also provides a phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared by the aforementioned preparation method.

[0036] The present invention also provides the application of the aforementioned phosphorus-doped carbon-supported molybdenum phosphide catalyst in the preparation of carbon monoxide from liquid-phase formic acid.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] 2.0 g ammonium molybdate, 2.0 g ammonium dihydrogen phosphate, 7.0 g sucrose, and 1.0 g diammonium hydrogen phosphate were dissolved evenly in 20.0 g deionized water to obtain a clear solution. The clear solution was dried at 80 °C for 12 h to obtain a black precursor. The precursor was pyrolyzed under a nitrogen atmosphere at a temperature of 750 °C for 2.5 h. After pyrolysis, the precursor was naturally cooled to room temperature under a nitrogen atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0040] 20 mL of pure formic acid and 0.5 g of the phosphorus-doped carbon-supported molybdenum phosphide catalyst of this embodiment were placed in a three-necked flask. The flask was then placed in a water bath at a temperature ranging from room temperature to 98°C. Test results showed that when the reaction temperature was 90°C, the catalyst yield was 529 mL / g / h, and no H2 or CO2 byproducts were detected in the gaseous products.

[0041] The XRD pattern of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the diffraction peaks of the phosphorus-doped carbon-supported molybdenum phosphide catalyst correspond to the positions of the standard spectrum of molybdenum phosphide PDF#65-6024, proving that the catalyst prepared in Example 1 is a molybdenum phosphide catalyst with good crystallinity.

[0042] The SEM image of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1 is shown below. Figure 2 As shown. By Figure 2 It can be seen that the catalyst prepared in this embodiment has fewer surface pores and exhibits a 3D three-dimensional morphology.

[0043] The EDS-mapping diagram of the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared in Example 1 is shown below. Figure 3 As shown. By Figure 3 It is known that the phosphorus-doped carbon-supported molybdenum phosphide catalyst prepared by the present invention can uniformly disperse molybdenum and phosphorus elements onto the support.

[0044] Example 2

[0045] 2.5 g ammonium molybdate, 3.0 g ammonium dihydrogen phosphate, 9.0 g glucose, and 1.5 g diammonium hydrogen phosphate were dissolved evenly in 10.0 g deionized water to obtain a clear solution. The clear solution was dried at 120 °C for 10 h to obtain a black precursor. The precursor was pyrolyzed under an argon atmosphere at a temperature of 780 °C for 2.5 h. After pyrolysis, the precursor was naturally cooled to room temperature under an argon atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0046] 20 mL of pure formic acid and 0.5 g of the phosphorus-doped carbon-supported molybdenum phosphide catalyst of this embodiment were placed in a three-necked flask. The flask was then placed in a water bath at a temperature of room temperature to 78°C. Test results showed that when the reaction temperature was 70°C, the catalyst yield was 322 mL / g / h, and no H2 or CO2 byproducts were detected in the gaseous products.

[0047] Example 3

[0048] 3.0 g ammonium molybdate, 2.5 g ammonium dihydrogen phosphate, 5.0 g sucrose, and 2.0 g diammonium hydrogen phosphate were dissolved evenly in 30.0 g deionized water to obtain a clear solution. The clear solution was dried at 110 °C for 11 h to obtain a black precursor. The precursor was pyrolyzed under a helium atmosphere at a temperature of 850 °C for 2.5 h. After pyrolysis, the precursor was naturally cooled to room temperature under a helium atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0049] 20 mL of pure formic acid and 0.5 g of the phosphorus-doped carbon-supported molybdenum phosphide catalyst of this embodiment were placed in a three-necked flask. The flask was then placed in a water bath at a temperature ranging from room temperature to 88°C. Test results showed that when the reaction temperature was 80°C, the catalyst yield was 417 mL / g / h, and no H2 or CO2 byproducts were detected in the gaseous products.

[0050] Example 4

[0051] 2.0 g ammonium molybdate, 2.0 g ammonium dihydrogen phosphate, 7.0 g glucose, and 1.0 g diammonium hydrogen phosphate were dissolved evenly in 15.0 g deionized water to obtain a clear solution. The clear solution was dried at 90 °C for 9 h to obtain a black precursor. The precursor was pyrolyzed under a nitrogen atmosphere at a temperature of 800 °C for 2.5 h. After pyrolysis, it was naturally cooled to room temperature under a nitrogen atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst.

[0052] 20 mL of pure formic acid and 0.5 g of the phosphorus-doped carbon-supported molybdenum phosphide catalyst of this embodiment were placed in a three-necked flask. The flask was then placed in a water bath at a temperature ranging from room temperature to 88°C. Test results showed that when the reaction temperature was 80°C, the catalyst yield was 398 mL / g / h, and no H2 or CO2 byproducts were detected in the gaseous products.

[0053] This invention employs a one-step pyrolysis method to prepare a phosphorus-doped carbon-supported molybdenum phosphide catalyst. The process is simple and safe, using inexpensive sugars as the catalyst support precursor. The catalyst is low-cost, widely available, and easily separated, making it suitable for large-scale industrial production. The catalyst of this invention is used for the low-temperature liquid-phase dehydration of pure formic acid to prepare carbon monoxide. It is a heterogeneous, non-precious metal catalyst with characteristics such as high gas production rate, low reaction temperature, and high selectivity for carbon monoxide.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a phosphorus-doped carbon-supported molybdenum phosphide catalyst in the preparation of carbon monoxide from liquid-phase formic acid, characterized in that, The preparation method of phosphorus-doped carbon-supported molybdenum phosphide catalyst includes the following steps: 1) Ammonium molybdate, ammonium dihydrogen phosphate, carbohydrates, diammonium hydrogen phosphate and water are mixed to obtain a mixture, which is then dried to obtain the precursor; 2) The precursor was pyrolyzed under a protective atmosphere to obtain a phosphorus-doped carbon-supported molybdenum phosphide catalyst; In step 1), the mass ratio of ammonium molybdate, ammonium dihydrogen phosphate, carbohydrate compound, diammonium hydrogen phosphate, and water is 2~3:2~3:5~9:1~2:10~30; Step 1) The carbohydrate compound is sucrose and / or glucose.

2. The application according to claim 1, characterized in that, Step 1) The drying temperature is 70~120℃, and the drying time is 8~14h.

3. The application according to claim 1, characterized in that, Step 2) The protective atmosphere is an argon atmosphere, a nitrogen atmosphere, or a helium atmosphere.

4. The application according to claim 2 or 3, characterized in that, Step 2) The pyrolysis temperature is 750~850℃, and the pyrolysis time is 2~3h.

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