Surface plasma bismuth molybdate nano-photocatalyst for catalyzing propanol to prepare propylene as well as preparation method and application of surface plasma bismuth molybdate nano-photocatalyst

Abstract

The invention belongs to the technical field of propylene production, and particularly relates to a surface plasma bismuth molybdate nano photocatalyst for catalyzing propyl alcohol to prepare propylene as well as a preparation method and application of the surface plasma bismuth molybdate nano photocatalyst. The tungsten-doped surface plasma bismuth molybdate nano photocatalyst is prepared by a hydrothermal method, is a nano flaky material, has the size of 10-300 nanometers, and has a remarkable surface plasma resonance effect in a visible-near infrared spectrum region. Under illumination, the catalyst can realize surface electron enrichment, generate strong surface plasma resonance and promote generation of hot electrons, and high-selectivity and high-yield preparation of propylene can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of propylene production, and specifically relates to a surface plasma bismuth molybdate nanophotocatalyst for catalyzing propylene alcohol to prepare propylene, and a preparation method and application thereof. Background Art

[0002] Propylene is the core raw material for the manufacture of medical products such as masks and protective clothing. Traditional propylene production is mainly prepared by high-temperature cracking or catalytic cracking of raw materials such as coal and petroleum. However, as the cost of olefin cracking continues to increase, the reaction of catalytic dehydration of propanol to prepare propylene has gradually attracted widespread attention. At present, alumina, ZSM-5, and MCM-41 acidic molecular sieves are often used in industry as catalysts to catalyze the dehydration of propanol to prepare propylene. The reaction conditions are harsh (high temperature), the energy consumption is large, the process is complex, and the cost is high. Photocatalysis, as a green technology route that can directly convert solar energy, has been widely used to catalyze various organic synthesis reactions. However, due to the narrow spectral response range, low propylene yield and selectivity of the current photocatalysts that promote the dehydration of alcohols, its application in the dehydration of propanol to prepare propylene is limited. Therefore, the development of photocatalysts with wide spectral response and high propylene yield is a prerequisite for achieving efficient photocatalytic propylene preparation. Summary of the invention

[0003] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a plasma nanomaterial of tungsten-doped bismuth molybdate. By doping tungsten with bismuth molybdate to form a high content of pentavalent tungsten, a large number of shallow defect energy levels are induced, and the concentration of surface free electrons can be greatly increased, thereby achieving effective electron enrichment on the surface of bismuth molybdate, generating a strong surface plasma resonance effect, and promoting the generation of hot electrons, so that it can efficiently photocatalyze the dehydration of propanol under normal temperature and pressure and full spectrum irradiation, and achieve high selectivity and high yield preparation of propylene.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] The first aspect of the present invention provides a tungsten-doped bismuth molybdate plasma photocatalyst, wherein the plasma catalyst is a nano-sheet material with a size of 10-300 nanometers, wherein pentavalent tungsten accounts for 15%-45% of the doped tungsten atoms, and has significant surface plasmon resonance absorption characteristics in the visible-near infrared region of 600-1300 nanometers.

[0006] The second aspect of the present invention provides a method for preparing the plasma photocatalyst of tungsten-doped bismuth molybdate according to the first aspect, the method comprising the following steps:

[0007] S1, uniformly dispersing bismuth nitrate and hexadecyltrimethylammonium bromide in an ethylene glycol solution, adding nitric acid dropwise, and stirring to obtain a solution A;

[0008] S2. Evenly disperse sodium molybdate and tungsten hexachloride in an ethylene glycol solution, then drop the solution into solution A, stir evenly to obtain solution B, then subject solution B to a hydrothermal reaction, cool to room temperature to obtain product C, wash product C, collect the precipitate by centrifugation, and then dry to obtain a plasma photocatalyst of tungsten-doped bismuth molybdate.

[0009] Preferably, in S1, the concentration of the bismuth nitrate in the ethylene glycol solution is 40-80 mmol / L; the concentration of the hexadecyltrimethylammonium bromide in the ethylene glycol solution is 2-5 g / L.

[0010] Preferably, in S1, the nitric acid is an aqueous nitric acid solution with a mass fraction of 50%-70%, and the volume ratio of the ethylene glycol solution to the aqueous nitric acid solution is 3:1-7:1.

[0011] Preferably, in S2, the concentration of the sodium molybdate in the ethylene glycol solution is 20-50 mmol / L, and the concentration of the tungsten hexachloride in the ethylene glycol solution is 0.05-0.1 mmol / L.

[0012] Preferably, in S2, the volume ratio of solution A to ethylene glycol solution is 0.3:1-3:1.

[0013] Preferably, in S2, the temperature of the hydrothermal reaction is 140-180° C., and the time is 10-16 hours.

[0014] Preferably, in S2, the centrifugal rotation speed is 7000-10000 rpm, and the time is 7-15 minutes.

[0015] Preferably, in S2, the drying method is vacuum drying; the temperature of the vacuum drying is 50-80 degrees Celsius, and the time is 10-14 hours.

[0016] The third aspect of the present invention provides the use of the plasma photocatalyst of tungsten-doped bismuth molybdate described in the first aspect in catalyzing the dehydration of propanol to prepare propylene.

[0017] The fourth aspect of the present invention provides a method for preparing propylene by dehydrating propylene alcohol, specifically comprising: adding the plasma photocatalyst of tungsten-doped bismuth molybdate described in the first aspect to propylene alcohol, and mixing them evenly to obtain a plasma photocatalyst dispersion; then dropping the plasma photocatalyst dispersion onto a glass sheet, and then placing the glass sheet under anaerobic conditions, and using a xenon lamp for ultraviolet-visible-near infrared full spectrum irradiation to obtain a propylene product.

[0018] Preferably, the mass volume ratio of the plasma photocatalyst of tungsten-doped bismuth molybdate to propanol is 1-5 mg:100 μL.

[0019] Preferably, the light intensity of the xenon lamp irradiation is 200-500 mW / cm2, and the irradiation time is 170-190 minutes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention discloses a method for preparing a plasma photocatalyst of tungsten-doped bismuth molybdate, wherein bismuth nitrate, sodium molybdate and tungsten hexachloride are used as raw materials, nitric acid and ethylene glycol are used as solvents and reducing agents, and hexadecyltrimethylammonium bromide is used as a surfactant, and a plasma nano-photocatalytic material of tungsten-doped bismuth molybdate is prepared by a hydrothermal method. In the prepared plasma photocatalytic material, the defect energy levels induced by pentavalent tungsten can realize effective electron enrichment on the surface of bismuth molybdate, increase the surface free electron concentration, and then produce a strong surface plasma resonance effect, expand the spectral response range, and improve the photocatalytic activity. At the same time, when the plasma photocatalytic material of tungsten-doped bismuth molybdate is applied to the dehydration of propanol to prepare propylene, under full spectrum irradiation, ultraviolet-visible-near infrared illumination cooperates with each other, can excite the hot electrons and photothermal effects of the surface plasma of tungsten-doped bismuth molybdate, jointly promote the photocatalytic dehydration of propanol, and then achieve high yield and high selectivity preparation of propylene, and solve the problems of high energy consumption of propylene catalyst, harsh reaction conditions, poor product selectivity and low propylene yield in the prior art.

[0022] In addition, the method for preparing tungsten-doped bismuth molybdate plasma photocatalytic material of the present invention is simple and easy to mass produce. When the tungsten-doped bismuth molybdate plasma photocatalytic material prepared by the method of the present invention catalyzes the dehydration of propanol to prepare propylene, it does not need to be carried out under high temperature and high pressure, but can be achieved by using sunlight at normal temperature and pressure difference, with low energy consumption and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Transmission electron microscopy image of plasma photocatalyst of tungsten-doped bismuth molybdate;

[0024] Figure 2 W4fX-ray photoelectron spectroscopy characterization of tungsten-doped bismuth molybdate plasma photocatalyst;

[0025] Figure 3 Absorption spectrum characterization of tungsten-doped bismuth molybdate plasma photocatalyst;

[0026] Figure 4 is a curve diagram showing the change of propylene yield over time;

[0027] Figure 5 is a curve diagram showing the change of yield of other products over time;

[0028] Figure 6 To investigate the product selectivity of the propanol dehydration reaction using tungsten-doped bismuth molybdate plasma photocatalyst. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0031] Example 1: Preparation method of plasma photocatalyst of tungsten-doped bismuth molybdate

[0032] (1) 1 mmol of bismuth nitrate and 0.05 g of hexadecyltrimethylammonium bromide were dispersed and dissolved in 15 mL of ethylene glycol solution, and then 3 mL of 68% nitric acid aqueous solution was added dropwise, and the mixture was stirred uniformly at a speed of 50 rpm for 15 minutes to obtain solution A.

[0033] (2) 0.5 mmol of tungsten hexachloride and 2 μmol of sodium molybdate were dispersed and dissolved in 15 mL of ethylene glycol solution, and then added dropwise to solution A. The mixture was stirred at 50 rpm for 15 minutes and mixed well to obtain solution B.

[0034] (3) The solution B was transferred to a hydrothermal reactor and reacted at 160° C. for 12 hours. After the reaction, the solution was naturally cooled to room temperature to obtain a reaction product C.

[0035] (4) The reaction product C was washed with deionized water and anhydrous ethanol solution in turn, and centrifuged at a speed of 9000 rpm. The precipitate was collected and vacuum dried at 60° C. for 12 hours to obtain a blue-black tungsten-doped bismuth molybdate plasma photocatalyst powder sample.

[0036] Figure 1 The transmission electron microscope image of the obtained tungsten-doped bismuth molybdate plasma photocatalyst is shown in Figure 1. It can be seen that the tungsten-doped bismuth molybdate plasma photocatalyst is a nano-sheet material with a size of 10-300 nanometers.

[0037] Figure 2 This is the W4f X-ray photoelectron spectrum of the obtained tungsten-doped bismuth molybdate plasma photocatalyst, in which pentavalent tungsten accounts for 20% (calculated by atomic number).

[0038] Figure 33 is the absorption spectrum of the obtained tungsten-doped bismuth molybdate plasma photocatalyst. It can be seen that the tungsten-doped bismuth molybdate plasma photocatalyst has significant surface plasmon resonance absorption characteristics in the visible-near infrared light region (600-1300 nanometers).

[0039] Example 2: Propylene production by dehydration of propanol

[0040] The tungsten-doped bismuth molybdate plasma photocatalyst prepared in Example 1 was used to promote the dehydration of propanol to produce propylene. The details are as follows:

[0041] Take 5mg of surface plasma bismuth molybdate powder sample and add it to 0.2mL propanol, and ultrasonicate for 10 minutes to obtain a uniform dispersion. Then the dispersion droplets are attached to a glass sheet, and the glass sheet is placed in a reactor with a capacity of 100mL, and nitrogen is introduced for 10 minutes to exhaust the air inside the reactor, and then the reactor is closed. The reactor is then placed in an optical shielding box and placed under a xenon lamp (with an irradiation intensity of 300 milliwatts / square centimeter) for 180 minutes of ultraviolet-visible-near infrared full spectrum (190-1100 nanometers) irradiation, during which the reaction products (gases) are collected every 30 minutes and monitored and analyzed by gas chromatography.

[0042] The curve of propylene yield changing with time is shown in Figure 4 As shown in Figure 2, it can be seen that after 180 minutes of reaction under full spectrum irradiation, the propylene yield reached 129.8 mmol / g. The yield changes of other by-products are as follows: Figure 5 As shown, the selectivity of the product is Figure 6 As shown, it can be seen that the selectivity of propylene is as high as 99.5%.

[0043] In summary, the plasma photocatalyst prepared by the hydrothermal method of the present invention is a tungsten-doped bismuth molybdate nanosheet material with a size of 10-300 nanometers and a significant surface plasmon resonance effect in the visible-near infrared spectral region. At the same time, the catalyst can achieve electron enrichment on the surface of bismuth molybdate by tungsten doping, increase the surface free electron concentration, and then produce a strong surface plasmon resonance effect, and promote the generation of hot electrons. Therefore, the plasma photocatalyst of the tungsten-doped bismuth molybdate is applied to the dehydration of propanol to prepare propylene, which can achieve high selectivity and high yield preparation of propylene, and has broad application prospects.

[0044] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A plasma photocatalyst of tungsten-doped bismuth molybdate, characterized in that: The plasma catalyst is a nano-sheet material with a size of 10-300 nanometers, in which pentavalent tungsten accounts for 15%-45% of the doped tungsten atoms, and has significant surface plasma resonance absorption characteristics in the visible-near infrared region of 600-1300 nanometers.

2. The method for preparing the plasma photocatalyst according to claim 1, characterized in that: The following steps are involved: S1, uniformly dispersing bismuth nitrate and hexadecyltrimethylammonium bromide in an ethylene glycol solution, adding nitric acid dropwise, and stirring to obtain a solution A; S2. Evenly disperse sodium molybdate and tungsten hexachloride in an ethylene glycol solution, then drop the solution into solution A, stir evenly to obtain solution B, then subject solution B to a hydrothermal reaction, cool to room temperature to obtain product C, wash product C, collect the precipitate by centrifugation, and then dry to obtain a plasma photocatalyst of tungsten-doped bismuth molybdate.

3. The method for preparing a plasma photocatalyst according to claim 2, characterized in that: In S1, the concentration of the bismuth nitrate in the ethylene glycol solution is 40-80 mmol / L; the concentration of the hexadecyltrimethylammonium bromide in the ethylene glycol solution is 2-5 g / L.

4. The method for preparing a plasma photocatalyst according to claim 2, characterized in that: In S1, the nitric acid is a nitric acid aqueous solution with a mass fraction of 50%-70%, and the volume ratio of the ethylene glycol solution to the nitric acid aqueous solution is 3:1-7:

1.

5. The method for preparing a plasma photocatalyst according to claim 1, characterized in that: In S2, the concentration of the sodium molybdate in the ethylene glycol solution is 20-50 mmol / L, and the concentration of the tungsten hexachloride in the ethylene glycol solution is 0.05-0.1 mmol / L.

6. The method for preparing a plasma photocatalyst according to claim 1, characterized in that: In S2, the volume ratio of the solution A to the ethylene glycol solution is 0.3:1-3:

1.

7. The method for preparing a plasma photocatalyst according to claim 1, characterized in that: In S2, the temperature of the hydrothermal reaction is 140-180° C., and the time is 10-16 hours.

8. Use of the plasma photocatalyst of tungsten-doped bismuth molybdate according to claim 1 in catalyzing the dehydration of propanol to produce propylene.

9. A method for preparing propylene by dehydrating propanol, characterized in that: The plasma photocatalyst of tungsten-doped bismuth molybdate described in claim 1 is added to propanol and mixed evenly to obtain a plasma photocatalyst dispersion; then the plasma photocatalyst dispersion is dropped onto a glass sheet, and the glass sheet is placed under oxygen-free conditions and irradiated with a xenon lamp in the ultraviolet-visible-near infrared full spectrum to obtain a propylene product.

10. The method for preparing propylene by dehydrating propanol according to claim 9, characterized in that: The mass volume ratio of the plasma photocatalyst doped with tungsten bismuth molybdate to propanol is 1-5 mg:100 μl; the light intensity of the xenon lamp irradiation is 200-500 mW / cm2, and the irradiation time is 170-190 minutes.

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