method for catalyzing formic acid dehydrogenation by using NiPd nanosheet catalyst under visible light
阅读说明：本技术 用NiPd纳米片催化剂可见光催化甲酸脱氢的方法 (method for catalyzing formic acid dehydrogenation by using NiPd nanosheet catalyst under visible light ) 是由 万超 周柳 王嘉佩 吴胜华 孙林 许立信 张代林 于 2019-09-19 设计创作，主要内容包括：本发明公开了一种用NiPd纳米片催化剂可见光催化甲酸脱氢的方法,属于化学化工技术领域。本发明将制备好的NiPd纳米片催化剂置于夹套反应器中,通过恒温循环槽控制反应,将可见光从夹套反应器上方照射反应液,接着将甲酸和甲酸钠混合液加入反应器中进行反应,生成的氢气采用排水法收集。与传统的负载型催化剂不同的是：根据本发明,调节催化剂中金属镍、钯的含量及Mxene-TiO<Sub>2</Sub>含量就可以制得用于光催化甲酸脱氢制氢气的高活性、高选择性负载型NiPd纳米片催化剂。使用该催化剂进行可见光甲酸脱氢反应,脱氢转化率和选择性均为100％,反应的TOF值大于1260h<Sup>-1</Sup>,循环使用8h,反应的TOF值仍大于1254h<Sup>-1</Sup>。(The invention discloses a method for catalyzing formic acid dehydrogenation by using visible light of a NiPd nanosheet catalyst, and belongs to the technical field of chemical engineering. The method comprises the steps of placing the prepared NiPd nanosheet catalyst in a jacket reactor, controlling the reaction through a constant-temperature circulating tank, irradiating reaction liquid by visible light from the upper part of the jacket reactor, adding a mixed solution of formic acid and sodium formate into the reactor for reaction, and collecting the generated hydrogen by adopting a drainage method. Unlike conventional supported catalysts: according to the invention, the contents of metallic nickel and palladium and Mxene-TiO in the catalyst are adjusted 2 The supported NiPd nanosheet catalyst with high activity and high selectivity for preparing hydrogen by photocatalytic formic acid dehydrogenation can be prepared. The catalyst is used for visible light formic acid dehydrogenation reaction, the dehydrogenation conversion rate and selectivity are both 100 percent, and the reaction is carried outTOF value greater than 1260h ‑1 The reaction time of the catalyst is 8 hours after the catalyst is recycled, and the TOF value of the reaction is still more than 1254 hours ‑1 。)
1. A method for catalyzing formic acid dehydrogenation by using NiPd nanosheet catalyst under visible light is characterized by comprising the following steps: putting a NiPd nanosheet catalyst into a jacket reactor, controlling the reaction at 30-60 ℃ through a constant-temperature circulating tank, irradiating the reaction solution from the upper part of the jacket reactor by visible light with the wavelength of lambda being more than 400nm, and then, adding a catalyst in a molar ratio of 1: (0.2-0.8) adding the mixed solution of formic acid and sodium formate into a reactor for reaction to obtain a product hydrogen;
the mass ratio of the catalyst to the mixed solution of formic acid and sodium formate is 1 (8-15);
The NiPd nanosheet catalyst comprises Ni, Pd and Mxene-TiO2And g-C3N4Nanosheets wherein the nickel is derived from nickel nitrate and the Pd is derived from palladium chloride, Mxene-TiO2Derived from Mxene-Ti2AlC，g-C3N4The nano-sheet is prepared by roasting melamine and lithium chloride;
The NiPd nanosheet catalyst is prepared by the following steps:
(1) Calcining melamine and lithium chloride in certain ratio under certain calcining condition and atmosphere, washing at certain temperature for certain period, and filtering to obtain g-C3N4Nanosheets;
the mass ratio of the melamine to the lithium chloride is 1: (4-7); the roasting temperature is 480-530 ℃, the roasting time is 4-9 hours, the atmosphere is nitrogen, the washing temperature is-5-20 ℃, and the washing time is 10-25 hours;
(2) Taking a certain amount of Ti2Adding AlC into hydrofluoric acid solution with certain concentration for a period of time, and freeze-drying to obtain Ti2C；
The mass concentration of the HF is 20-45 wt%, and the treatment time is 6.0-14.0 h;
(3) Mixing Ti2c and g-C3N4The nano-sheets are placed in a hydrothermal synthesis kettle containing 40ml of deionized water according to a certain molar ratio, and added with a certain concentrationNaHSO of3Ultrasonically dispersing the solution for a period of time, putting the solution at a certain temperature for hydrothermal synthesis for a period of time, filtering, washing with water, and freeze-drying to obtain the Mxene-TiO2@g-C3N4A nanosheet carrier;
The Ti2C and g-C3N4The molar ratio of the nano-sheets is 1: (6 to 12) NaHSO3The concentration is 0.05-0.09 mol/L, the hydrothermal synthesis temperature is 120-160 ℃, and the hydrothermal synthesis time is 9-15 h;
(4) freeze drying the obtained porous Mxene-TiO2@g-C3N4Placing the nanosheet carrier in a nickel nitrate and palladium chloride solution with a certain composition, reducing for a period of time at a certain temperature by using a hydrazine hydrate solution, and centrifugally drying to obtain the NiPd/Mxene-TiO2@g-C3N4A nanosheet catalyst;
The nickel nitrate, palladium chloride and Mxene-TiO2@g-C3N4The molar ratio of the nano-sheets is 1: (0.2-0.5): (12-18), the concentration of hydrazine hydrate is 0.3-0.7 mol/L, the reduction temperature is 5-15 ℃, and the reduction time is 3-9 h.
2. the method of visible light catalyzed dehydrogenation of formic acid with a NiPd nanosheet catalyst of claim 1, wherein:
The mass ratio of the melamine to the lithium chloride is 1: 6.5; the roasting temperature is 490 ℃, the roasting time is 4 hours, the atmosphere is nitrogen, the washing temperature is 20 ℃, and the washing time is 14 hours;
The mass concentration of the HF is 45 wt%, and the treatment time is 8 h;
The Ti2C and g-C3N4The molar ratio of the nano-sheets is 1: 6, NaHSO3The concentration is 0.05mol/L, the hydrothermal synthesis temperature is 120 ℃, and the hydrothermal synthesis time is 11 h;
The nickel nitrate, palladium chloride and Mxene-TiO2@g-C3N4The molar ratio of the nano-sheets is 1: 0.2: 17, the concentration of hydrazine hydrate is 0.7mol/L, the reduction temperature is 5 ℃, and the reduction time is 7 hours;
The reaction temperature is 55 ℃, the mass ratio of the catalyst to the mixed solution of formic acid and sodium formate is 1:15, and the molar ratio of formic acid to sodium formate is 1: 0.6.
Technical Field
the invention belongs to the technical field of chemistry and chemical engineering, and particularly relates to a method for preparing NiPd/TiO2@g-C3N4A method for dehydrogenating formic acid by visible light catalysis of a nanosheet catalyst.
background
The current world-wide energy composition mainly depends on non-renewable energy sources such as coal, petroleum and the like, the large amount of the energy sources causes serious environmental problems, and the reserves are limited; with large scale mining, there is also a serious energy crisis. Currently, scientists focus on the search for new energy sources that are green, clean and sustainable, with hydrogen being widely favored as an emerging green energy source.
At present, hydrogen energy sources have more application modes, and the hydrogen energy sources are widely applied mainly to hydrogen fuel cells. The bottleneck of the large-scale application of the hydrogen fuel cell is mainly the technical problem of hydrogen storage. Although the high-pressure hydrogen storage technology matched with hydrogen fuel has been broken through, the high-pressure hydrogen storage has higher requirements on materials and is easy to generate hydrogen leakage to cause danger. Chemical hydrogen storage has received much attention from researchers because of its safety and high efficiency, and among them, formic acid has been widely available and has been widely studied in recent years because of its high mass hydrogen storage density. Researchers find that the development of efficient dehydrogenation catalysts is expected to promote the large-scale application of formic acid as a hydrogen storage material.
Williams et al use a catalyst formed of iridium and N, P-ligands to catalyze the dehydrogenation of formic acid containing 5% sodium formate with a TON as high as 2160000(nat. Commun.2016,7,11308). AuPd/ompg-C was developed by Wanqiao et al3N4Catalyst, high efficiency catalyst for dehydrogenation of sodium formate/formic acid, TOF up to 165h-1(201510680435. X). With the continuous progress of the photocatalytic technology in recent years, the development of catalytic formic acid dehydrogenation under the action of visible light is an important direction for the application of the hydrogen storage material in the future.
Disclosure of Invention
the invention aims to overcome the defects of the prior art and provides a method for preparing NiPd/Mxene-TiO2@g-C3N4The method for dehydrogenating formic acid by visible light catalysis of a nanosheet catalyst, namely NiPd/Mxene-TiO2@g-C3N4The nanosheet catalyst can realize complete dehydrogenation of formic acid under a relatively mild condition under the action of visible light, and has good catalytic activity, selectivity and stability.
The technical scheme adopted by the invention for solving the technical problem is as follows.
A method for catalyzing formic acid dehydrogenation by using NiPd nanosheet catalyst through visible light specifically comprises the following steps: putting a NiPd nanosheet catalyst into a jacket reactor, controlling the reaction at 30-60 ℃ through a constant-temperature circulating tank, irradiating the reaction solution from the upper part of the jacket reactor by visible light with the wavelength of lambda being more than 400nm, and then, adding a catalyst in a molar ratio of 1: (0.2-0.8) adding the mixed solution of formic acid and sodium formate into the reactor for reaction to obtain the product hydrogen.
The mass ratio of the catalyst to the mixed solution of formic acid and sodium formate is 1 (8-15).
The NiPd nanosheet catalyst comprises Ni, Pd and Mxene-TiO2And g-C3N4Nanosheets wherein the nickel is derived from nickel nitrate and the Pd is derived from palladium chloride, Mxene-TiO2Derived from Mxene-Ti2AlC，g-C3N4The nano-sheet is prepared by roasting melamine and lithium chloride.
The NiPd nanosheet catalyst is prepared by the following steps:
(1) Calcining melamine and lithium chloride in certain ratio under certain calcining condition and atmosphere, washing at certain temperature for certain period, and filtering to obtain g-C3N4Nanosheets;
The mass ratio of the melamine to the lithium chloride is 1: (4-7); the roasting temperature is 480-530 ℃, the roasting time is 4-9 hours, the atmosphere is nitrogen, the washing temperature is-5-20 ℃, and the washing time is 10-25 hours;
(2) Taking a certain amount of Ti2Adding AlC into hydrofluoric acid solution with certain concentration for a period of time, and freeze-drying to obtain Ti2C；
The mass concentration of the HF is 20-45 wt%, and the treatment time is 6.0-14.0 h;
(3) Mixing Ti2C and g-C3N4placing the nano-sheets in a hydrothermal synthesis kettle containing 40ml of deionized water according to a certain molar ratio, and adding NaHSO with a certain concentration3Ultrasonically dispersing the solution for a period of time, putting the solution at a certain temperature for hydrothermal synthesis for a period of time, filtering, washing with water, and freeze-drying to obtain the Mxene-TiO2@g-C3N4A nanosheet carrier;
The Ti2c and g-C3N4The molar ratio of the nano-sheets is 1: (6 to 12) NaHSO3The concentration is 0.05-0.09 mol/L, the hydrothermal synthesis temperature is 120-160 ℃, and the hydrothermal synthesis time is 9-15 h;
(4) freeze drying the obtained porous Mxene-TiO2@g-C3N4Placing the nanosheet carrier in a nickel nitrate and palladium chloride solution with a certain composition, reducing for a period of time at a certain temperature by using a hydrazine hydrate solution, and centrifugally drying to obtain the NiPd/Mxene-TiO2@g-C3N4A nanosheet catalyst;
The nickel nitrate, palladium chloride and Mxene-TiO2@g-C3N4The molar ratio of the nano-sheets is 1: (0.2-0.5): (12-18), the concentration of hydrazine hydrate is 0.3-0.7 mol/L, the reduction temperature is 5-15 ℃, and the reduction time is 3-9 h.
further, the mass ratio of melamine to lithium chloride is 1: 6.5; the roasting temperature is 490 ℃, the roasting time is 4 hours, the atmosphere is nitrogen, the washing temperature is 20 ℃, and the washing time is 14 hours; the mass concentration of the HF is 45 wt%, and the treatment time is 8 h; the Ti2C and g-C3N4The molar ratio of the nano-sheets is 1: 6, NaHSO3The concentration is 0.05mol/L, the hydrothermal synthesis temperature is 120 ℃, and the hydrothermal synthesis time is 11 h; the nickel nitrate, palladium chloride and Mxene-TiO2@g-C3N4the molar ratio of the nano-sheets is 1: 0.2: 17, the concentration of hydrazine hydrate is 0.7mol/L, the reduction temperature is 5 ℃, and the reduction time is 7 hours; the reaction temperature is 55 ℃, the mass ratio of the catalyst to the mixed solution of formic acid and sodium formate is 1:15, and the molar ratio of formic acid to sodium formate is 1: 0.6. at this time, the selectivity of hydrogen was 100%, the conversion of formic acid was 100%, and the TOF value of the reaction was 1632h-1。
Compared with the prior art, the invention has the beneficial effects that:
1. The invention relates to Mxene-Ti2Synthesis of oxygen-deficient Mxene-TiO by using AlC as precursor2And then hydrothermally synthesizing high-dispersity Mxene-TiO2@g-C3N4Nanosheet support material, Mxene-TiO2@g-C3N4The nano-sheet carrier material has good electron transfer performance and photoinduction performance, and further adopts a dipping reduction method NiPd/Mxene-TiO2@g-C3N4The supported NiPd alloy is synthesized by reducing hydrazine hydrate under mild conditions by the nanosheet catalyst, and the NiPd alloy can be regulated and controlled in structure and uniformly supported on a carrier. The charge distribution of the metal valence band orbit is changed by adjusting the proportion of metal components, the concentration of a reducing agent and reaction conditions, and the stability of catalytic reaction is further adjusted. In addition, the influence of multi-component Metal composition and multi-functional groups on the surface of the carrier obviously enhances the Strong interaction (SMSI) of the Metal and the carrier between the Metal and the carrier, and effectively improves the catalytic activity.
2. the invention adopts a dipping reduction method, firstly adopts a salt melting method to synthesize g-C3N4Nanosheets, treating Ti with hydrofluoric acid2Ti from AlC (Mxene)2C, mixing g-C3N4Nanosheet and Ti2C, preparing Mxene-TiO by hydrothermal treatment2@g-C3N4Nanosheet, Mxene-TiO to be obtained2@g-C3N4Placing the nanosheet in a nickel nitrate and palladium chloride solution with a certain composition, reducing for a period of time at a certain temperature by using a hydrazine hydrate solution, and centrifugally drying to obtain the NiPd/Mxene-TiO2@g-C3N4The nanosheet catalyst has high activity and selectivity under the action of visible light. The catalyst is used for visible light catalytic formic acid dehydrogenation reaction, the dehydrogenation conversion rate and selectivity are both 100%, and the TOF value of the reaction is more than 1260h-1The reaction time of the catalyst is 8 hours after the catalyst is recycled, and the TOF value of the reaction is still more than 1254 hours-1。
Detailed description of the invention
The present invention will be described in further detail by way of examples. The examples are not to be construed as limiting the invention.
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