阅读说明：本技术 一种用于十二氢乙基咔唑脱氢的铂/二氧化钛催化剂及其制备方法 (Platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethylcarbazole and preparation method thereof ) 是由 姜召 龚翔 方涛 于 2019-09-09 设计创作，主要内容包括：本发明公开了一种用于十二氢乙基咔唑脱氢的铂/二氧化钛催化剂及其制备方法,该催化剂的成分为铂、钛和氧,铂、钛和氧在催化剂中所占的质量百分比分别为0.5～5.0％、56.9～59.7％和38.1～39.8％；其制备方法分为两步：载体二氧化钛预处理,铂/二氧化钛催化剂的合成；本发明在乙二醇中,以柠檬酸钠为还原剂来制备负载型铂/二氧化钛催化剂,所得到的催化剂粉末粒径较小,并且分布均匀；能够在不添加任何表面活性剂和分散剂的条件下,有效解决了金属颗粒大和分布不均匀的问题；本发明催化剂能在保持反应活性的同时还降低了贵金属铂的用量,脱氢反应终产物乙基咔唑的选择性提高至97％以上,总脱氢量提升至5.75wt％。(the invention discloses a platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethyl carbazole and a preparation method thereof, wherein the catalyst comprises the components of platinum, titanium and oxygen, and the mass percentages of the platinum, the titanium and the oxygen in the catalyst are respectively 0.5-5.0%, 56.9-59.7% and 38.1-39.8%; the preparation method comprises the following two steps: pretreating carrier titanium dioxide, and synthesizing a platinum/titanium dioxide catalyst; in ethylene glycol, sodium citrate is used as a reducing agent to prepare a supported platinum/titanium dioxide catalyst, and the obtained catalyst powder has small particle size and uniform distribution; the problems of large metal particles and uneven distribution can be effectively solved under the condition of not adding any surfactant and dispersant; the catalyst of the invention can keep the reaction activity and simultaneously reduce the dosage of noble metal platinum, the selectivity of the final product of the dehydrogenation reaction, namely ethyl carbazole, is improved to more than 97 percent, and the total dehydrogenation amount is improved to 5.75 percent by weight.)

1. A platinum/titania catalyst for dehydrogenation of dodecahydroethylcarbazole, characterized by: the catalyst comprises the components of platinum, titanium and oxygen, wherein the mass percentages of the platinum, the titanium and the oxygen in the catalyst are respectively 0.5-5.0%, 56.9-59.7% and 38.1-39.8%.

2. The method of preparing a platinum/titania catalyst for dehydrododecahydroethylcarbazole according to claim 1, wherein: the method comprises the following steps:

Step one, pretreatment of carrier titanium dioxide, comprising the following specific steps:

1) Adding titanium dioxide and ethylene glycol into a container, and placing the container on a magnetic stirrer to stir for 15-30 min, so that the titanium dioxide is uniformly dispersed in the ethylene glycol, wherein the titanium dioxide and the ethylene glycol correspond to 20ml of ethylene glycol according to the relation of the amount of each 1.0g of titanium dioxide;

2) Heating the mixture of titanium dioxide and glycol to 110-130 ℃ while stirring, keeping the temperature for 10-20 min, stopping heating, and cooling to room temperature;

3) Filtering the cooled mixture, washing the mixture by using deionized water and absolute ethyl alcohol until no ethylene glycol residue exists, and drying the mixture in a drying oven at the temperature of 60-80 ℃ for 6-12 hours; grinding after completely drying, and weighing required amount for later use;

Step two, synthesizing the platinum/titanium dioxide catalyst, which comprises the following specific steps:

1) Adding potassium chloroplatinate and ethylene glycol into a container, and placing the container on a magnetic stirrer to stir for 3-6 hours to fully disperse the potassium chloroplatinate in the ethylene glycol; weighing the pretreated titanium dioxide obtained in the first step, adding the titanium dioxide into the mixture of the ethylene glycol and the potassium chloroplatinate, and continuously stirring for 0.5-1.0 h to fully disperse the titanium dioxide; adding potassium chloroplatinate with the corresponding mass according to the mass fraction of platinum loading of 0.5-5.0%, and adding ethylene glycol into 20ml of ethylene glycol corresponding to every 1.0g of titanium dioxide;

2) adding a reducing agent sodium citrate according to the mass of 8-10 times of that of the potassium chloroplatinate, adding the reducing agent sodium citrate into the mixture, heating to 110-130 ℃, stirring for 20-30 min, stopping heating after the color of the mixed solution is changed from milky white to cement gray, and cooling to room temperature;

3) And filtering the mixed solution cooled to room temperature, washing the mixed solution by using deionized water and absolute ethyl alcohol until no ethylene glycol, sodium citrate, potassium ions and chloride ions remain, drying the mixed solution in a drying oven at the temperature of 60-80 ℃ for 6-12 h, and grinding the dried product to obtain the platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethylcarbazole.

Technical Field

The invention belongs to the technical field of organic liquid hydride hydrogen storage, and particularly relates to a platinum/titanium dioxide catalyst for dehydrogenating dodecahydroethyl carbazole and a preparation method thereof.

Background

in recent years, the problems of energy crisis and environmental deterioration are always puzzling all over the world, and experts and scholars continuously try to find a more efficient and environment-friendly energy source so as to reduce or even replace the status of the traditional fossil fuel in national production and life. Hydrogen energy is one of the most likely energy sources to be widely used, and has attracted attention in many fields due to its advantages such as large storage capacity, high calorific value, and environmental friendliness. In the field of fuel cells in particular, researchers have been trying to apply hydrogen fuel cells to mobile transportation devices to reduce the emission of toxic and harmful gases. However, the development of hydrogen energy in commercial application is not smooth due to the difficulties in hydrogen storage technology at present. For example: the safety of the pressurized gaseous hydrogen storage technology is low, and the transportation is inconvenient; the metal alloy hydrogen storage technology has non-ideal hydrogen storage capacity and low hydrogen absorption and desorption rate; the low-temperature liquefied hydrogen storage technology has large energy consumption and high cost.

When researchers research hydrocarbon organic substances and dehydrogenation reactions, the researchers find that hydrogen energy can be stored and utilized through reversible reaction of liquid organic hydride and hydrogen. The technology has the advantages of large hydrogen storage capacity, high hydrogen energy utilization rate, safety, stability, environmental friendliness, recyclable hydrogen storage material, capability of being transported for a long distance through the existing fossil fuel basic transportation equipment, and great reduction of commercial application cost.

Among the numerous reported organic liquid hydrogen storage materials, ethyl carbazole was the first proposed liquid organic hydrogen storage material that could achieve a hydrodeoxygenation cycle below 200 ℃. The theoretical hydrogen storage density is 5.79 wt%, and the purity of the released hydrogen can reach 99.9%, so that the hydrogen storage device not only meets the technical hydrogen storage indexes proposed by the U.S. department of energy, but also is environment-friendly.

Some literature reports indicate that the platinum and palladium catalysts can realize dehydrogenation reaction of dodecahydroethyl carbazole within the temperature range of 180-270 ℃. But different supported noble metal catalysts, such as: palladium/alumina, platinum/alumina, palladium/activated carbon, etc., all have low dehydrogenation efficiency (only about 60% of hydrogen can be released) at lower temperature, and the noble metal dosage is large. In order to better realize the commercial application of the organic liquid hydrogen storage material, the design and synthesis of a low-load metal catalyst capable of improving the dehydrogenation reaction rate of the dodecahydroethylcarbazole at a lower temperature are necessary.

Titanium dioxide is an N-type semiconductor, and is researched more in the field of photocatalysis for a long time due to the special photoelectric characteristic, but is not applied to dehydrogenation reaction of dodecahydroethylcarbazole.

the key to the current progress of the technology is how to design and develop a low-load metal catalyst capable of improving the dehydrogenation selectivity and the dehydrogenation rate of the dodecahydroethylcarbazole at a lower temperature, thereby effectively improving the energy conversion rate of the hydrogen fuel cell.

disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethylcarbazole and a preparation method thereof, the catalyst provided by the invention can maintain excellent performance while reducing the loading of noble metal, so that the reaction time is greatly shortened, and the selectivity of the catalyst on final products of the dehydrogenation reaction, namely ethylcarbazole, is greatly improved; the synthesis process is simple and convenient, has low cost, and meets the conditions required by large-scale production.

In order to achieve the purpose, the invention adopts the following technical scheme:

The catalyst comprises the components of platinum, titanium and oxygen, wherein the mass percentages of the platinum, the titanium and the oxygen in the catalyst are respectively 0.5-5.0%, 56.9-59.7% and 38.1-39.8%.

the preparation method of the platinum/titanium dioxide catalyst for dehydrogenating dodecahydroethyl carbazole comprises the following steps:

Step one, pretreatment of carrier titanium dioxide, comprising the following specific steps:

1) adding titanium dioxide and ethylene glycol into a container, and placing the container on a magnetic stirrer to stir for 15-30 min, so that the titanium dioxide is uniformly dispersed in the ethylene glycol, wherein the titanium dioxide and the ethylene glycol correspond to 20ml of ethylene glycol according to the relation of the amount of each 1.0g of titanium dioxide;

2) heating the mixture of titanium dioxide and glycol to 110-130 ℃ while stirring, keeping the temperature for 10-20 min, stopping heating, and cooling to room temperature;

3) filtering the cooled mixture, washing the mixture by using deionized water and absolute ethyl alcohol until no ethylene glycol residue exists, and drying the mixture in a drying oven at the temperature of 60-80 ℃ for 6-12 hours; grinding after completely drying, and weighing required amount for later use;

Step two, synthesizing the platinum/titanium dioxide catalyst, which comprises the following specific steps:

1) Adding potassium chloroplatinate and ethylene glycol into a container, and placing the container on a magnetic stirrer to stir for 3-6 hours to fully disperse the potassium chloroplatinate in the ethylene glycol; weighing the pretreated titanium dioxide obtained in the first step, adding the titanium dioxide into the mixture of the ethylene glycol and the potassium chloroplatinate, and continuously stirring for 0.5-1.0 h to fully disperse the titanium dioxide; adding potassium chloroplatinate with corresponding mass according to the mass fraction of 0.5-5.0% of the platinum load, and adding ethylene glycol according to 20ml of ethylene glycol corresponding to each 1.0g of titanium dioxide);

2) adding a reducing agent sodium citrate according to the mass of 8-10 times of that of the potassium chloroplatinate, adding the reducing agent sodium citrate into the mixture, heating to 110-130 ℃, stirring for 20-30 min, stopping heating after the color of the mixed solution is changed from milky white to cement gray, and cooling to room temperature;

3) And filtering the mixed solution cooled to room temperature, washing the mixed solution by using deionized water and absolute ethyl alcohol until no ethylene glycol, sodium citrate, potassium ions and chloride ions remain, drying the mixed solution in a drying oven at the temperature of 60-80 ℃ for 6-12 h, and grinding the dried product to obtain the platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethylcarbazole.

According to the preparation method of the platinum/titanium dioxide catalyst for dehydrogenation of dodecahydroethylcarbazole, the amounts of potassium chloroplatinate, titanium dioxide, ethylene glycol and sodium citrate can be increased or decreased in equal proportion.

Compared with the prior art, the invention has the following advantages:

1. the preparation method has the advantages of simple and convenient preparation steps, mild preparation conditions and low preparation cost, and is suitable for large-scale production.

2. the platinum/titanium dioxide catalyst prepared by a water immersion method and hydrogen high-temperature reduction is usually adopted, and the particle size of platinum particles is larger. The catalyst prepared in the ethylene glycol can ensure that the platinum is dispersed more fully, so that the distribution of active sites is more uniform. According to the invention, sodium citrate is used as a reducing agent, and the sodium citrate shows mild reducibility within the temperature range of 110-130 ℃, so that the platinum metal is prevented from being agglomerated due to too high reduction speed to generate larger particles.

3. In the traditional liquid phase reduction method of the platinum/titanium dioxide catalyst, sodium borohydride solution or hydrazine hydrate is commonly used as a reducing agent, and a certain amount of dispersing agent or surfactant is added. The reducing agent has strong reducibility, so that noble metal particles are easy to agglomerate and grow up and are not beneficial to dispersion, and the prepared catalyst has larger particle size. According to the invention, in an ethylene glycol system, sodium citrate is used as a reducing agent to prepare the platinum/titanium dioxide catalyst, and the obtained catalyst can also keep small particle size and is uniformly distributed under the condition of not adding any dispersing agent or surfactant. The invention overcomes the defects of large metal particle size and uneven dispersion of the traditional method under the condition of not adding a dispersant and a surfactant.

4. according to the method, the titanium dioxide powder is pretreated by using the ethylene glycol at the temperature of 110-130 ℃, so that impurities adsorbed on the surface of the titanium dioxide can be cleaned, and the influence of the impurities on the adsorption process of the active metal platinum can be reduced.

5. The platinum/titanium dioxide catalyst prepared by the method has excellent performance, not only greatly shortens the reaction time, but also greatly reduces the dosage of noble metal platinum while maintaining the excellent reaction performance, and finally the selectivity of the dehydrogenation product ethyl carbazole is greatly improved to more than 97 percent, and the dehydrogenation amount reaches more than 5.75 percent by weight.

drawings

FIG. 1 is an X-ray diffraction photograph of a platinum/titanium dioxide catalyst prepared according to the present invention.

FIG. 2 is a peak fitting of the platinum element in the X-ray photoelectron spectrum of the platinum/titanium dioxide catalyst prepared in the present invention.

FIG. 3 shows the macro-morphology of the platinum/titanium dioxide catalyst prepared by the present invention at 50nm, 10nm and 5nm scales in a high-resolution transmission electron microscope photograph.

FIG. 4 is a 20nm scale high angle annular dark field image of a platinum/titanium dioxide catalyst made in accordance with the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments.