CN113198513B

CN113198513B - Catalyst for preparing olefin by dehydrogenating alkane, preparation method and dehydrogenation method thereof

Info

Publication number: CN113198513B
Application number: CN202110541901.1A
Authority: CN
Inventors: 周永华; 林百宁; 徐凡; 刘雨薇; 仇普文; 王华伟; 王雷; 王宁
Original assignee: Tianjin Dagu Chemical Co ltd; Central South University
Current assignee: Tianjin Dagu Chemical Co ltd; Central South University
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2022-02-25
Anticipated expiration: 2041-05-18
Also published as: CN113198513A; WO2022241881A1

Abstract

The invention belongs to the technical field of catalytic dehydrogenation, and particularly discloses a preparation method of an olefin catalyst by alkane dehydrogenation, which comprises the steps of recrystallizing a compound raw material capable of providing B, P, S, N element in a solvent, heating a recrystallized product to 700-1000 ℃ at a heating rate of more than or equal to 5 ℃/min in an ammonia-containing atmosphere, and carrying out heat preservation roasting to prepare the catalyst; in the compound raw material, S: the molar ratio of the B element is more than or equal to 10; p: the molar ratio of the B element is more than or equal to 0.5; n: the molar ratio of the elements of B is greater than or equal to 10. The invention also comprises the catalyst prepared by the preparation method and the application of the catalyst in preparing olefin by directly or oxidatively dehydrogenating alkane. The invention can obtain a special catalyst based on the preparation method, and the catalyst has good conversion rate and excellent product selectivity and stability.

Description

Catalyst for preparing olefin by dehydrogenating alkane, preparation method and dehydrogenation method thereof

Technical Field

The invention belongs to the field of chemical synthesis, and particularly relates to a catalyst for preparing olefin by alkane dehydrogenation and a dehydrogenation method.

Background

Olefin is an important chemical raw material, for example, styrene is used as a derivative of aromatic hydrocarbon, is an important monomer raw material for producing high polymers in the chemical industry, and is widely applied to the fields closely related to daily life of people. It is estimated that the annual styrene related commercial value can reach $ 600 billion. In recent 20 years, with the continuous development of the downstream product market of styrene in the world, the demand of styrene rises year by year. Although the production capacity of styrene is abundant from the international market, the styrene self-sufficiency rate is still at a low level as one of the countries where the demand for styrene is rapidly increasing in China. The related data show that the styrene production capacity of China is more than 1500 ten thousand tons/year by 2022, while the apparent styrene demand of a downstream device reaches 1800-1900 ten thousand tons/year according to the currently known new, expanded and proposed plan of the downstream device, and the gap still exceeds 300 ten thousand tons/year. Under the big background of anti-tipping and trade wars, the additional tax of the imported styrene in China is greatly increased, which means that a new styrene production technology is developed, particularly, a catalyst for preparing styrene by ethylbenzene dehydrogenation with high performance, low cost and low energy consumption is independently developed, and the catalyst has important significance and is challenging for improving the self-sufficiency rate of the styrene in China.

In the actual production process, the reaction for preparing styrene by ethylbenzene dehydrogenation is considered to be a strong endothermic reaction with the increased molecular number, the limitation of thermodynamic equilibrium is large, and the reaction conversion rate is favorably improved under the conditions of low pressure and high temperature. In 1937, Dow chemical (Dow) and BASF (BASF) in Germany realized the industrial production of styrene by dehydrogenation of ethylbenzene. Through the development of more than 80 years, the currently industrially applied styrene production methods mainly comprise two methods: the ethylbenzene direct dehydrogenation method and the styrene-ethylene oxide coproduction method, and the ethylbenzene catalytic dehydrogenation catalyst is gradually replaced by an iron catalyst with more excellent comprehensive performance from a zinc catalyst and a magnesium catalyst used in the initial period. Currently, the Lummus/Monsanto/UOP process for producing styrene by directly dehydrogenating ethylbenzene at the high temperature of 600-650 ℃ and under the protection of excess steam (the water/hydrocarbon ratio is 7-15) by using potassium-containing iron oxide or zinc oxide as a catalyst is the most widely applied styrene production technology in the world at present, the technical research has a history for more than 70 years so far, corresponding research results are widely accepted, and the styrene produced by the process accounts for more than 90% of the total styrene production quantity in the world. But the large consumption of the water vapor causes huge energy consumption in the whole production process. In addition, it is considered that the polymerization of styrene is accelerated by an excessively high temperature, and potassium is unstable at a high temperature and easily transferred to a low temperature region or the center of catalyst particles, resulting in deterioration of the stability of the catalyst.

At present, the largest suppliers of ethylbenzene catalytic dehydrogenation catalysts abroad are southern chemical company in germany and standard catalysts company in the united states, and basf company in germany and dow chemical company are still producing such catalysts. As far as southern chemical companies are concerned, their newly introduced Styromax series catalysts have replaced earlier produced G-64, G-84 and G-97 series catalysts. Ethylbenzene catalytic dehydrogenation catalysts from american standard catalyst companies were also developed earlier, especially Shell-105 was used for a long time in large production facilities. In recent years, the standard companies have introduced catalysts such as C-035, C-045, C-145 and Flexi Cat yellow/blue in succession in order to meet the requirements of the production plant. The independent research of ethylbenzene catalytic dehydrogenation catalyst in China starts in 60 s of the 20 th century, and LH series developed by the research center of Lanzhou chemical industry of the petrochemical group of Zhongtian petroleum chemical industry institute, XH series of Xiamen university, DC series developed by the institute of Chinese academy of linkage chemico-physical research and GS series catalyst developed by the research institute of petrochemical Shanghai petroleum chemical industry in China have all realized industrial application. Such as: CN106423187A, CN106423240A, CN105312059A and CN 105749934A. In particular, the catalyst reported in patent CN105749934A can be used at a relatively low water/hydrocarbon (1.2-2.0) ratio, but the problem of high energy consumption when introducing steam still exists. In addition, the catalyst of the above system uses the oxidation of metals such as cerium, chromium, manganese and the like or rare earth elements as auxiliary agents, and partial substances in the catalysts, such as chromium oxide, not only increase the catalyst cost, but also have great harm to the environment and even human health. On the other hand, the improvement of the catalytic dehydrogenation process, such as the improvement of the per pass conversion rate and the reduction of the use of heat energy, is approaching to the limit, while the oxidative dehydrogenation system has the problems of deep oxidation of styrene, low reaction selectivity, limitation of the explosive limit range of the composition of reactants in the actual operation and the like, and also limits the conversion rate of the dehydrogenation reaction to a certain extent. Under the background, the development of a catalyst with high conversion rate, high selectivity, high stability and environmental friendliness, particularly the development of a catalyst suitable for operation under anhydrous or low water/hydrocarbon ratio conditions, has important significance for energy conservation and consumption reduction in the production process of styrene.

In recent years, the search for non-metallic catalysts has become a focus of research. Particularly, the appearance of the two-dimensional material with regular structure and changeable elements provides more possibilities for the research of the alkane dehydrogenation catalyst. In 2010, the sudangshen research institute of metal, shenyang, academy of sciences, china, for the first time reported that Nanodiamond (ND) can be used as a high-efficiency non-metal catalyst for preparing styrene by catalyzing direct dehydrogenation of ethylbenzene under the anhydrous vapor condition, and an unsaturated ketone/diketone type carbonyl (C ═ O) with higher electron density of oxygen atoms is considered as an active center of the catalyst. This work has raised the trend of research on the application of carbon-based catalysts to ethylbenzene dehydrogenation. Then, on the basis of Shenyang metal of Chinese academy of sciences and university of great continuance, carbon nanotubes (novel carbon material, 2013,28,5, 336-; up to now, it has been recognized that doping of nitrogen atoms into a carbon matrix can provide additional electrons to the delocalized pi-system and increase the chemical reactivity of C ═ O in the carbon material. Besides carbon materials, hexagonal boron nitride (h-BN) is considered as a novel characteristic material in the field of heterogeneous catalysis due to the characteristics of strong thermal stability, strong oxidation resistance, high thermal conductivity and the like, and can quickly dissipate reaction heat in high exothermic reaction (such as F-T synthesis). It is reported that the h-BN structure is in combination with C₃N₄Similarly, it is a metal-free catalyst for alkane dehydrogenation, especially the application of carbon-doped BN nano-sheet in propane dehydrogenation and ethylbenzene-carbon dioxide oxidative dehydrogenation (Angew. chem. int. Ed.,2017,56, 8231-8235; J.energy. chem. Doi: 10.1016/j.j.jechem.2020.03.027), and is greatly applicable to the dehydrogenation of alkaneThe application of the heteroatom-doped two-dimensional metal-free material in the field of alkane dehydrogenation is enriched. Some materials such as commercial boron carbide (CN109126843A) also showed higher stability but lower activity.

The work greatly expands the application of the nonmetal catalyst in ethylbenzene dehydrogenation, and particularly researches on the preparation of styrene catalyst by direct dehydrogenation under anhydrous condition. However, nitrogen-doped carbon materials are easy to decompose at high temperature, so that most of the catalysts are limited to be applied below 550 ℃, so that the activity and the stability of the catalysts are not ideal. In addition, anhydrous aerobic dehydrogenation tends to produce more carbon dioxide as a byproduct than anhydrous anaerobic dehydrogenation. Therefore, the development of a non-metal dehydrogenation catalyst which is suitable for anhydrous conditions, especially anhydrous and anaerobic conditions, and has the advantages of high temperature resistance, excellent performance, simple preparation process and the like is still the focus of current research.

Previous work in the subject group of the applicant (CN 201910739798.4) found that phosphorus doped boron nitride is an excellent nonmetallic catalyst for ethylbenzene dehydrogenation. However, the boron nitride-based catalyst prepared by the current subject group mostly takes powder as a main component, has the particle size of 100-200 meshes, is inconvenient for kilogram-level preparation and application in actual production, and has limited practical value; and the phenomenon of carbon deposition inactivation still exists after long-term operation; but also the selectivity of the catalyst has room for improvement.

Disclosure of Invention

Aiming at the technical problems of non-ideal catalytic selectivity, easy carbon deposition, non-ideal long-term stability and the like of the existing catalyst for preparing olefin by alkane dehydrogenation (the catalyst is also called as catalyst for short in the invention), the first purpose of the invention is to provide a preparation method of the catalyst for preparing olefin by alkane dehydrogenation, aiming at improving the product selectivity, the carbon deposition resistance and the long-term stability while keeping good conversion rate.

The second purpose of the invention is to provide the catalyst prepared by the preparation method.

The third purpose of the invention is to provide an alkane dehydrogenation method of the catalyst prepared by the preparation method.

A preparation method of a catalyst for preparing olefin by alkane dehydrogenation comprises the steps of recrystallizing a compound raw material capable of providing B, P, S, N elements in a solvent, heating a recrystallization product to 700-1000 ℃ in an ammonia-containing atmosphere at a heating rate of more than or equal to 5 ℃/min, and carrying out heat preservation roasting to obtain the catalyst;

in the compound raw material, S: the molar ratio of the B element is more than or equal to 10;

p: the molar ratio of the B element is more than or equal to 0.5;

n: the molar ratio of the elements of B is greater than or equal to 10.

The technical scheme of the invention innovatively adopts S, P compound to participate in the in-situ preparation of boron nitride, and further comprises the following steps of based on the form of raw materials, B: s element ratio, B: the synergistic control of the P element ratio and the roasting mechanism (such as the temperature rise rate and the roasting temperature) can unexpectedly obtain a brand-new catalyst which is modified by P, has a special microstructure and has excellent catalytic performance.

In the invention, the in-situ synthesis of boron nitride is carried out under the synergistic assistance of S and P, and the synergistic control on the form, proportion and roasting mechanism of the raw materials is the key for improving the microstructure of the prepared catalyst and improving the performance of the catalyst for preparing olefin by dehydrogenation.

In the present invention, the P, S element needs to be introduced by compound form, so that the element can be unexpectedly cooperated with other conditions, thereby improving the microstructure of the prepared material and improving the dehydrogenation performance of the material.

Preferably, the compound raw material comprises a boron source, a phosphorus source, a sulfur source and a nitrogen source, wherein the boron source is a boron compound capable of providing boron element;

the phosphorus source is a phosphorus compound capable of providing phosphorus element;

the sulfur source is a sulfur compound capable of providing sulfur element;

the nitrogen source is a nitrogen compound capable of providing nitrogen elements.

In the present invention, the raw material may be a compound which can provide only one element of B, P, S, N, or may be a compound which can provide two or more elements of B, P, S, N, and for example, a compound containing N, S two elements may be used as a nitrogen source or a sulfur source.

Preferably, the sulfur source is one or more of thiourea, thioethylthiourea, ammonium thiosulfate and ammonium sulfate. It has been found that the preferred sulfur source compounds, in combination with other conditions, unexpectedly improve the microstructure of the resulting catalyst and improve the performance of the catalyst. More preferably, the sulfur source is thiourea. The preferred compounds are able to further improve the synergistic effect of the present solution, contributing to the unexpected further improvement of the performance of the catalysts obtained.

Preferably, the phosphorus source is at least one of hydroxyethylidene diphosphoric acid, hexachlorotriphosphazene and ammonium dihydrogen phosphate.

Preferably, the boron source is selected from at least one of boric acid and boron oxide.

Preferably, the nitrogen source is at least one of urea, cyanamide, dicyanamide, thiourea and melamine.

In the invention, the combined control of B, P, S element in the raw materials can unexpectedly further improve the microstructure of the prepared material, improve P modification hybridization and improve the catalytic performance, and is particularly helpful for improving the selectivity of products.

Preferably, in the compound starting material, S: the molar ratio of the B element is 10-90: 1; more preferably 16 to 60: 1; more preferably 20 to 60: 1: most preferably 28 to 60: 1.

preferably, in the compound starting material, P: the molar ratio of the B element is 0.5-2: 1; further preferably 1-2: 1; more preferably 1 to 1.4: 1.

Preferably, in the compound starting material, N: the element molar ratio of B is 10-200: 1; further preferably 30-130: 1; more preferably 40 to 120: 1.

In the present invention, the compound capable of providing B, S, P and N element may be subjected to a recrystallization reaction in a solvent. Preferably, the solvent may be water;

preferably, the recrystallization temperature is 30-90 ℃, and more preferably 40-90 ℃; more preferably 50 to 80 ℃.

After recrystallization, conventional solid-liquid separation and drying treatment can be carried out to obtain the product.

In the invention, the product obtained by recrystallization is roasted in an ammonia-containing atmosphere, and researches show that the improvement of cooperativity and the improvement of the catalytic performance of the prepared material can be realized by the aid of the S, P compound and the further coordination of the temperature rise rate and the temperature, and the improvement of the selectivity and the stability of the prepared material is particularly facilitated.

Preferably, the heating rate is 5-15 ℃/min; further preferably 5-10 ℃/min; further preferably 5 to 7.5 ℃/min.

Preferably, in the roasting process, the introduction amount of the ammonia gas containing the ammonia atmosphere is 5-100 mL/min; further preferably 5-80 mL/min; more preferably 40 to 60 mL/min.

Preferably, the roasting temperature is 700-900 ℃; more preferably 800 to 900 ℃.

In the invention, the time of heat preservation roasting is more than or equal to 2 hours; preferably 2-5 h.

According to the preferable preparation method, the raw material aqueous solution of the boron source, the nitrogen source, the phosphorus source and the sulfur source is recrystallized, and then the recrystallized product is dried and roasted in an ammonia atmosphere to obtain the boron-containing organic silicon-based catalyst. The phosphorus source is one or more of hydroxyl ethylidene diphosphoric acid monohydrate, hexachlorotriphosphazene and ammonium dihydrogen phosphate; the sulfur source is one or more of thiourea, thioethylthiourea, ammonium sulfate and ammonium thiosulfate; the boron source is selected from one of boric acid and boron oxide; the nitrogen source is selected from one or more of urea, cyanamide, dicyandiamide and melamine. The recrystallization temperature of the raw material liquid is 40-90 ℃; the vacuum drying temperature of the recrystallized product is 50-80 ℃, and the drying time is 10-20 h; when the ammonia gas is roasted in the ammonia gas atmosphere, the introduction amount of the ammonia gas is 5-100mL/min, the heating rate is 5-15 ℃/min, the roasting temperature is 700-900 ℃, and the roasting time is 2-5 h.

In the present invention, the catalyst may be supported on a carrier.

In the invention, the carrier can be a carrier known in the industry, and can be prepared by loading in a loading way known in the industry.

Preferably, the carrier is at least one of alumina and silicon dioxide or other carriers containing one of the two components;

for example, the steps of the load are as follows:

and (3) recrystallizing a compound raw material capable of providing B, P, S and N elements, formaldehyde and a precursor raw material capable of being converted into a carrier in a solvent, and then performing gradient roasting on a recrystallization product to obtain the catalyst.

Further specific supported catalysts (structured catalysts) are prepared, for example, by the following processes:

and a self-molding technique using formaldehyde or the like as a bubbling medium. The method specifically comprises the following steps: weighing nitrogen source materials with required mass, adding formaldehyde solution, and condensing and refluxing to be clear under the stirring condition of 30-90 ℃. Adding the raw materials of the boron source, the phosphorus source and the sulfur source in the required proportion, and continuously refluxing for 1-10 hours. Transferring the sample into a container, adding one of sodium silicate, silica sol or aluminum sol with certain mass, uniformly stirring, and carrying out constant-temperature heat treatment at 100-200 ℃ for 12-36 hours. And taking out the heat-treated sample, crushing, sieving, taking a certain mesh number, placing in a tubular furnace, introducing 5-80mL/min ammonia gas for gradient roasting, and naturally cooling to room temperature to obtain the supported catalyst.

As a variant of the same inventive concept, another supported catalyst according to the invention is prepared, for example, by: and mixing the carrier and the synthesized raw materials, and performing recrystallization and roasting treatment to obtain the catalyst.

The invention also comprises the catalyst prepared by the preparation method. The catalyst can be in the form of nano, micron or millimeter powder, or in the form of a structured form which is larger in size and is further obtained by means of self-forming and the like.

The preparation method is innovative, and based on the in-situ synthesis of the BN participated by the compounds S and P and the joint control of conditions, the preparation method can help the modification of P and the control of modification morphology, and in addition, the preparation method can also have the function of the compounds S, control the microstructure of the material, and unexpectedly obtain a new material with special chemical and physical structures.

The invention also discloses a method for preparing alkene by alkane dehydrogenation, which comprises the step of contacting alkane raw materials with the catalyst prepared by the preparation method to perform dehydrogenation reaction to prepare corresponding alkene products.

In the invention, the direct dehydrogenation or oxidative dehydrogenation of alkane can be realized by using the catalyst, the corresponding alkene can be efficiently obtained, and the catalyst has good conversion rate, product selectivity and stability.

Preferably, the alkane starting material is a compound having the formula 1:

formula 1

Wherein R is₁～R₄Is alone H, C₁～C₁₀Alkyl of (C)₃～C₁₀Cycloalkyl or aryl of (a); or, R₁And R₄Mutually cyclized to form a ring group;

the alkyl, the naphthenic base, the cyclic group or the aryl is allowed to have a substituent group which is respectively substituted alkyl, substituted naphthenic base, substituted cyclic group and substituted aryl; wherein the substituent is C₁～C₆Alkyl of (C)₁～C₆At least one substituent of alkoxy, halogen, phenyl, nitro and trifluoromethyl.

The alkyl in the invention is a straight chain or branched chain alkyl. The naphthenic base is a ternary-hexahydric monocyclic ring, a spiro ring or a bridged ring. The aryl is a benzene ring, a five-membered heterocyclic aryl group, a six-membered heterocyclic aryl group, or a condensed ring formed by the union of two or more aromatic rings in the benzene ring, the five-membered heterocyclic aryl group and the six-membered heterocyclic aryl group.

In addition, said R₁And R₄Mutually annular shapeA cyclic group such as a five-or six-membered ring. For example, the structure of the cyclized alkane feed is, for example, as

In the invention, the olefin product of the formula 2 is obtained by directly or oxidatively dehydrogenating the formula 1 under the catalysis of the catalyst

Preferably, the alkane starting material is a compound having the structure of formula 1-1;

in the formula 1-1, R₁Is H, C₁～C₆Alkyl, phenyl or substituted phenyl of (a); the benzene ring of the substituted phenyl contains C₁～C₆Alkyl of (C)₁～C₆At least one substituent of alkoxy, halogen, phenyl, nitro and trifluoromethyl.

Under the catalysis of the catalyst, the formula 1-1 can be directly catalyzed to prepare the corresponding terminal olefin product (R)₁- (Y-O-); formula 2-1).

Preferably, the dehydrogenation reaction is carried out under anhydrous conditions; or under an atmosphere containing a weak oxygen. Oxygen content of the oxygen-poor atmosphere, for example, not higher than 10 vol.%; for example, the concentration of the surfactant may be 1 to 5 vol.%.

Preferably, the dehydrogenation reaction is carried out in an aerobic atmosphere or an anaerobic atmosphere;

preferably, the temperature of the dehydrogenation reaction is 500-700 ℃; preferably 550-650 ℃; more preferably 600 to 650 ℃.

In the present invention, the dehydrogenation reaction can be carried out based on existing reaction equipment, for example, it can be filled into a reactor and gas-solid phase catalytic reaction can be carried out.

The principle is as follows:

at present, forThe active sites of non-metallic catalysts in hydrocarbon dehydrogenation reactions are believed by most researchers to be C ═ O groups or B — OH groups present on the surface of carbon and boron nitride materials. The catalysts prepared by the present invention were analyzed by XPS on the surface groups and the pore structure by physical adsorption of nitrogen, as shown in the following examples and comparative examples, and N is₃P-OH、N₂Groups such as P ═ O and N-B-O can be used as reactive groups in the reaction; moreover, the microstructure of the catalyst has a significant impact on selectivity and stability; by introducing sulfur and phosphorus compounds in the in-situ synthesis stage of boron nitride, modification of P can be improved based on the synergy of the sulfur compounds, the phosphorus compounds and conditions, and the microstructure of the material can be regulated and controlled, so that the catalytic performance of the prepared material can be improved.

Has the advantages that:

1. the method innovatively carries out in-situ synthesis of boron nitride under the coordination of a sulfur-phosphorus compound, can improve modification of BN by P under the coordination of S, P material form, content and roasting mechanism, is favorable for regulating and controlling microstructure, and further remarkably improves product selectivity, improves carbon deposition problem and improves catalyst stability while maintaining good conversion rate. The invention takes the typical ethylbenzene dehydrogenation as an example, the styrene generation amount realized in unit catalyst and unit time can reach 24.33 mmol/(g.h), the styrene selectivity is more than 97%, and the stable operation lasts for more than 100 hours. Has important economic value, environmental protection value and social value for the industrial reaction with practical significance.

2. The further research of the invention finds that the mass transfer condition has obvious influence on the selectivity and stability of the reaction catalyst. By controlling the sulfur source type, the B/S ratio, the roasting temperature, the roasting time and the structuring method in the preparation process of the catalyst, the pore structure of the catalyst is favorably regulated and controlled, and the selectivity and the stability of alkane dehydrogenation are further improved.

3. The invention further researches and discovers that N₃P-OH、N₂The groups such as P ═ O and N-B-O can be used as active groups in the reaction, so that the catalyst is a brand new catalystThe meter provides theoretical guidance.

4. The structured catalyst has better mechanical strength and formability, and can meet the production technical requirements of different conditions.

5. Compared with the potassium-containing iron oxide catalyst used in the industry at present, the catalyst provided by the invention has the advantages of high temperature resistance, stronger carbon deposition resistance, simple preparation process, no metal pollution and the like, and has a very good industrial application prospect.

Drawings

FIG. 1: nitrogen adsorption-desorption curve for the catalyst of comparative example 1

FIG. 2 is a drawing: nitrogen adsorption-desorption curves for the catalyst of example 1

FIG. 3: XPS plot of the catalyst of example 1

FIG. 4 is a drawing: TEM image of the catalyst of example 1

FIG. 5: SEM image of catalyst of example 11

Detailed Description

The present invention will be described in detail with reference to examples.

Example 1

Weighing a certain amount of boric acid (a boron source, 0.4g), thiourea (a sulfur source and a nitrogen source) and hydroxyethylidene diphosphonic acid (a phosphorus source), wherein in the raw materials, B: n: s: the molar ratio of P is 1: 90: 48: 1.2), adding 40mL of distilled water, stirring for dissolving, then carrying out recrystallization operation on the beaker filled with the precursor-containing solution under the conditions of 80 ℃ oil bath and 300rpm stirring until no obvious moisture exists, and then transferring the obtained white recrystallized product into a 50 ℃ vacuum drying oven for further drying for 12 hours. Grinding the dried recrystallization product into powder, loading the powder into a corundum ark, placing the corundum ark in a tubular furnace, introducing 60mL/min ammonia gas to provide roasting atmosphere, heating the corundum ark to 800 ℃ from room temperature at the heating rate of 5 ℃/min, roasting the corundum ark for 3 hours, and naturally cooling the corundum ark to room temperature under the protection of ammonia gas (the flow of the ammonia gas is 20mL/min), thus obtaining the catalyst, wherein: BNSP-thiourea/HEDP-48/1.2. A nitrogen adsorption-desorption curve chart 2 of the prepared material; XPS chart see FIG. 3; the TEM image is shown in FIG. 4.

As can be seen from comparison of figures 1 and 2, the nitrogen adsorption-desorption curve of the prepared material shows H3 typeHysteresis ring, i.e. slit pore structure, with specific surface area of 101.13m²The specific surface area of the material is 140-260 m higher than that of BNP-1.2 (comparative example 1) in previous work²/g) is small, the average pore diameter of the material is 13.39nm and is far larger than the pore diameter (3nm) of BNP-1.2 by combining pore size analysis, so the specific surface area is lower than that of BNP-1.2. In addition, the XPS test of fig. 3 found that the atomic percentage of S was lower than the detection line of the instrument, i.e., S hardly entered the BN skeleton or surface, and thus it was concluded that the role of the S source was mainly to influence the formation of the catalyst microstructure during the heat treatment of the material.

The test method of the catalyst performance is as follows: adding 50mg of catalyst into 2mL of quartz sand with the granularity of 40-60 meshes for dilution, filling the mixture into a fixed bed quartz reaction tube with the diameter of phi 8mm, and plugging two ends of a catalyst bed layer by a small amount of quartz cotton. An inert gas atmosphere was provided by introducing 20mL/min of nitrogen. Under the protection of nitrogen, the temperature is raised to 600 ℃ at the speed of 4 ℃/min, the catalyst is pre-activated for 30min in a stable way, and then mixed raw material gas with the volume fraction of 2.8 percent of ethylbenzene is introduced at the flow rate of 20mL/min for continuous reaction. The reaction product was collected with 5 ℃ ethanol and analyzed for composition by Shimadzu GC-2010Plus gas chromatograph, model RTX-5 column, FID detector. The initial ethylbenzene conversion rate is 77.43%, the styrene selectivity is 97.25%, and the corresponding styrene generation amount realized in unit time on the unit catalyst is 22.72 mmol/(g.h), and can be stabilized for more than 40 hours.

Example 2

Compared with the example 1, the difference is that the components of the sulfur source are changed, and the research is respectively carried out by adopting ammonium thiosulfate and ammonium sulfate, wherein, when the ammonium thiosulfate is used as the sulfur source, urea is used as a supplementary nitrogen source to control the proportion of B to N to be kept unchanged, and other parameters and operation are the same as the example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in table 1:

table 1:

example 3

The only difference compared to example 1 is that the molar ratio of sulfur source was varied to 1:16, 1:20, 1:24, 1:28 for B: S, respectively, and urea was used as a supplemental nitrogen source to maintain B: n is unchanged, and in the case that the molar ratio of B to S is 1:60, urea is not additionally added as a nitrogen source; other parameters and operations were the same as in example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in table 2:

TABLE 2

a, no additional urea is added.

Example 4

Compared with the example 1, the difference is that the components of the phosphorus source are changed, ammonium dihydrogen phosphate and hexachlorotriphosphazene are respectively adopted for research, and other parameters and operation are the same as the example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in table 3:

TABLE 3

Example 5

The only difference compared to example 1 is that the molar ratio of phosphorus source was varied to give B to P molar ratios of 1:1.0 and 1:1.4, respectively, and the other parameters and operations were the same as in example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in table 4:

TABLE 4

As can be seen from example 5 and our earlier work, B: the size of the molar ratio of P determines the atomic percent of the phosphorus element in the prepared material and the active site N₂P ═ O and N₃Relative proportion of P-OH. When the ratio of B to P is less than or equal to 1 to 1.4, the atomic percentage of the phosphorus element in the prepared material is increased, and N is₂P ═ O and N₃The relative proportion of P-OH gradually decreases. Combined with DFT theoretical calculation, N₂P ═ O promotes cleavage of C-H bonds in ethylbenzene, N₃The P-OH reduces the energy barrier of H combined desorption generated after the cracking, and the two realize the reaction of directly dehydrogenating the ethylbenzene to generate the styrene under the synergistic effect. When B: P > 1:1.4, the catalytic performance is poor because the use of HEDP introduces a large amount of C and O at the same time as the introduction of P, resulting in a decrease in the atomic percent of phosphorus in the prepared material. In general, the preferred B: the molar ratio of P is 1: 0.9 to 1.4.

Example 6

The temperature increase rates (rates of temperature increase to the firing temperature) were changed to 7.5 ℃/min and 10 ℃/min, respectively, as compared with example 1, and other parameters and operations were the same as in example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in table 5:

TABLE 5

As can be seen from examples 1 and 6, excellent catalytic performance can be obtained at a temperature rise rate of 5 ℃/min or more, particularly preferably 5 to 7.5 ℃/min.

Example 7

The firing temperatures were changed to 600 deg.C, 700 deg.C, 900 deg.C, respectively, as compared with example 1, and other parameters and operations were the same as in example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in Table 6:

TABLE 6

Researches show that good catalytic performance can be obtained at the temperature of more than or equal to 600 ℃, particularly preferably 800-900 ℃.

Example 8

Compared with the ammonium thiosulfate as the sulfur source in the example 2, the difference is only that the supplement of the N source is the cyanamide and the dicyandiamide respectively, and other parameters and operations are the same as those in the example 1.

The performance of the catalyst as measured by the catalyst performance test method of example 1 is shown in Table 7:

TABLE 7

Example 9

The nitrogen flow, the heating rate and the temperature of calcination (80mL/min, 10 ℃/min, 900 ℃) were varied simultaneously as compared with example 1. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: the initial ethylbenzene conversion was 63.09%, the styrene selectivity was 97.33%, and the styrene production per unit time on the catalyst was 18.53 mmol/(g.h), which was stable for 40 hours or longer.

Example 10

8.4g of commercially available dinitrile diamine was weighed, 10ml of a commercially available 37% formaldehyde solution was added, the mixture was placed in a 50ml three-necked flask, and after the mixture was cooled and refluxed to be clear under an oil bath at 85 ℃ and at 400rpm, the cooling and refluxing were continued for 1 hour under the same conditions.

A certain amount of commercially available boric acid (0.4g), thiourea and hydroxyethylidene diphosphonic acid (in the raw materials, the molar ratio of B: N: S: P is 1: 90: 48: 1.2) are weighed, added into a three-neck flask, continuously subjected to oil bath at 85 ℃ and condensation reflux at 400rpm until the mixture is clear, and continuously subjected to condensation reflux for 1 hour under the same conditions.

Transferring the sample into a test tube, weighing 1.5g of commercially available sodium silicate, adding into the test tube, stirring uniformly, covering a plug with a small hole, and placing into a 180 ℃ oven for constant temperature heat treatment for 12 h.

Taking out the heat-treated sample, smashing, sieving, taking a 20-40 mesh sample, loading the sample into a corundum ark, placing the corundum ark in a tubular furnace, introducing 60mL/min ammonia gas to provide a roasting atmosphere, heating from room temperature to 800 ℃ at a heating rate of 5 ℃/min, roasting for 3h, and then naturally cooling to room temperature under the protection of ammonia gas to obtain the self-formed sulfur-modified phosphorus-doped boron nitride catalyst, wherein: BNSP-thiourea/HEDP-48/1.2-self-molding.

Adding 2mL of BNSP-thiourea/HEDP-48/1.2 with the particle size of 40-60 meshes for self-forming, and adopting the catalyst performance test method in the embodiment 1 to test the performance of the catalyst, wherein the performance of the catalyst is as follows: the initial ethylbenzene conversion rate is 78.31%, the styrene selectivity is 97.39%, and the styrene yield per unit time on the corresponding unit catalyst is 23.01 mmol/(g.h), which can be stabilized for more than 100 hours.

Example 11 (Supported structured catalyst prepared compared to example 1)

Compared with the example 1, the 20-40 mesh active alumina particles are added into the mixed solution of boric acid, thiourea and hydroxyethylidene diphosphonic acid monohydrate, and other steps are not changed. The catalyst is noted as: BNP @ alumina/HEDP-48/1.2. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: the initial ethylbenzene conversion rate is 82.50%, the styrene selectivity is 97.72%, and the corresponding styrene generation amount per unit catalyst in unit time is 24.33 mmol/(g.h), and the stability can be realized for more than 100 hours.

Example 12 (oxidative dehydrogenation)

The catalyst of example 1 was applied to oxidative dehydrogenation under a weak oxygen atmosphere. Compared with the example 1, in the method for testing the performance of the catalyst, 20ml/min of nitrogen is changed into nitrogen-oxygen mixed gas containing 3 percent of oxygen (volume percentage), and the performance of the catalyst is measured as follows: the initial ethylbenzene conversion rate is 78.35%, the styrene selectivity is 94.60%, and the corresponding styrene generation amount realized in unit time on the unit catalyst is 22.36 mmol/(g.h), and can be stabilized for more than 100 hours.

Example 13

The difference from example 1 is only that the temperatures during the dehydrogenation reaction are 550 deg.C, 575 deg.C, 625 deg.C, and other parameters and operations are the same as example 1.

TABLE 7

Comparative example 1

Compared with the example 1, the method mainly comprises the following steps of not adding a sulfur source, replacing a nitrogen source by urea, and carrying out the same specific steps as the example 1 with the application number of 201910739798.4; the catalyst was denoted BNP 1.2.

The catalytic effect of this comparative example was: the initial ethylbenzene conversion rate is 62.42 percent, the styrene selectivity is 93.54 percent, and the ethylbenzene conversion amount realized in unit time on the corresponding unit catalyst is 17.62 mmol/(g.h), and the stability can be realized for more than 20 hours. The effect is significantly worse than example 1 and the product selectivity is worse than the embodiments of the present invention.

Comparative example 2

The only difference compared to example 1 is that elemental sulphur (sublimed sulphur, added in the same molar amount as in example 1; the N source is provided by urea and the molar amount of N source is the same as in example 1) is used, the other conditions are the same as in example 1, and the catalyst is: BNSP-sublimed sulphur/HEDP-48/1.2. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: initial ethylbenzene conversion was 22.36% and styrene selectivity was 93.71%. The amount of styrene produced per unit time on the corresponding catalyst was 6.32 mmol/(g.h).

Comparative example 3

The only difference compared to example 1 is that no phosphorus source was added. The catalyst is noted as: BNS-48. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: 29.73 percent and the selectivity of the styrene is 97.68 percent. The amount of styrene produced per unit time on the corresponding catalyst was 8.76 mmol/(g.h), and was stable for 20 hours or longer. The effect is significantly worse than in example 1, mainly the conversion of the product is worse than in the embodiment of the present invention.

Comparative example 4

Compared with example 1, the difference is only that the phosphorus source is phosphorus (red phosphorus, the molar amount is the same as that in example 1). The catalyst is noted as: BNSP-thiourea/P-48-1.2. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: initial ethylbenzene conversion was 20.04% and styrene selectivity was 90.68%. The amount of styrene produced per unit time on the corresponding catalyst was 5.48 mmol/(g.h).

Comparative example 5

Compared with examples 1 and 5, the difference is only that the molar ratio of the boron element to the phosphorus element is 1: 0.2), the catalyst is noted as: BNSP-thiourea/HEDP-48/0.2. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: the initial ethylbenzene conversion was 28.42% and the styrene selectivity was 95.31%, corresponding to a styrene production of 8.17 mmol/(g.h) per unit time per unit catalyst.

Comparative example 6

The only difference between the samples was that the temperature increase rate was 1 ℃/min, as compared with examples 1 and 6. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: initial ethylbenzene conversion was 46.59%, and styrene selectivity was 92.42%. The amount of styrene produced per unit time on the corresponding catalyst was 12.99 mmol/(g.h), and was stable for 20 hours or longer.

Comparative example 7

The only difference compared with examples 1 and 7 is that the firing temperature was 1100 ℃. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: initial ethylbenzene conversion was 50.33% and styrene selectivity was 83.03%. The amount of styrene produced per unit time on the corresponding catalyst was 12.61 mmol/(g.h), and was stable for 20 hours or longer.

Comparative example 8

Discussing physical mixing of BN and sulfur and P sources:

compared with the example 1, the difference is mainly that BN is directly synthesized without adding a phosphorus source and a sulfur source (the synthesis mode is the same as that of the example 1, for example, B is adopted for sintering in an ammonia atmosphere); then BN, a sulfur source (thiourea) and a P source are mixed according to the proportion, and the mixture is further subjected to heat treatment under the nitrogen protection atmosphere. The catalyst performance test method of example 1 was used to determine that the catalyst performance was: initial ethylbenzene conversion was 18.51% and styrene selectivity was 85.47%. The amount of styrene produced per unit time on the corresponding catalyst was 4.77 mmol/(g.h), and was stable for 20 hours or longer.

Comparative example 9 (blank carrier quartz sand)

2mL of quartz sand with the granularity of 40-60 meshes is measured, and the performance of the catalyst is measured by adopting the catalyst performance test method in the embodiment 1: the initial ethylbenzene conversion was 8.82% and the styrene selectivity was 58.33%, corresponding to a styrene yield of 1.55 mmol/(g.h) per unit time on the catalyst.

COMPARATIVE EXAMPLE 10 (blank Carrier sodium silicate)

2mL of sodium silicate is measured, and the performance of the catalyst is measured by the catalyst performance test method in example 1: the initial ethylbenzene conversion was 7.80% and the styrene selectivity was 62.45%, corresponding to a styrene production of 1.47 mmol/(g.h) per unit time on the catalyst.

And (3) analysis:

from the results of the examples and the comparative examples, (1) the doping of the sulfur element can obviously improve the selectivity of the phosphorus-nitrogen-boron catalyst to styrene. (2) The co-addition of a sulfur source and a phosphorus source is one of the keys for obtaining the high-performance catalyst. (3) The type of sulfur source, the type of phosphorus source, and the amount of addition are the second key to obtaining a high performance catalyst. (4) The heating system is the key to obtain high-performance catalyst. As can be seen from the figure, the catalyst is a distinct porous material. The sulfur element mainly affects the formation of pore structure during the catalyst synthesis. The catalyst pore structure is more reasonable, the transfer and the conversion of an intermediate are facilitated in dynamics, and the occurrence of side reactions is avoided.

Claims

1. A preparation method of a catalyst for preparing olefin by hydrocarbon raw material dehydrogenation is characterized in that a compound raw material capable of providing B, P, S, N elements is recrystallized in a solvent, and then a recrystallization product is heated to 700-1000 ℃ at a heating rate of 5-15 ℃/min in an ammonia-containing atmosphere and is subjected to heat preservation and roasting to prepare the catalyst;

in the compound raw material, S: the molar ratio of the B element is 10-90: 1;

p: the molar ratio of the B element is 0.5-2: 1;

n: the element molar ratio of B is 10-200: 1;

the compound raw materials comprise a boron source, a phosphorus source, a sulfur source and a nitrogen source, wherein the sulfur source is one or more of thiourea, thioethylthiourea, ammonium thiosulfate and ammonium sulfate;

the phosphorus source is at least one of hydroxyl ethylidene diphosphoric acid, hexachlorotriphosphazene and ammonium dihydrogen phosphate;

the hydrocarbon raw material is a compound with a structural formula of formula 1:

formula 1

Wherein R is₁~R₄Is alone H, C₁~C₁₀Alkyl of (C)₃~C₁₀Cycloalkyl or aryl of (a); or, R₁And R₄Mutually cyclized to form a ring group;

the alkyl, the naphthenic base, the cyclyl or the aryl is allowed to have a substituent, and the substituent is C₁~C₆Alkyl of (C)₁~C₆At least one substituent of alkoxy, halogen, phenyl, nitro and trifluoromethyl.

2. The process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the ratio of S: the molar ratio of the B element is 16-60: 1.

3. the process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the ratio of S: the molar ratio of the B element is 20-60: 1.

4. the process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the ratio of S: the molar ratio of the B element is 28-60: 1.

5. the process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the ratio of P: the molar ratio of the B element is 1-2: 1.

6. The process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the ratio of P: the molar ratio of the B element is 1-1.4: 1.

7. The process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the molar ratio of N: the molar ratio of the elements B is 30-130: 1.

8. The process for preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to claim 1, wherein in said compound feedstock, the molar ratio of N: the molar ratio of the elements B is 40-120: 1.

9. The method of claim 1, wherein the nitrogen source is at least one of urea, cyanamide, dicyanamide, thiourea and melamine.

10. The method of claim 1, wherein the boron source is at least one selected from the group consisting of boric acid and boron oxide.

11. The method of claim 1, wherein the solvent is water.

12. The method of claim 1, wherein the temperature of recrystallization is from 30 ℃ to 90 ℃.

13. The method of claim 12, wherein the temperature of recrystallization is from 40 ℃ to 90 ℃.

14. The method of claim 1, wherein the ammonia gas is introduced in an amount of 5-100mL/min during the calcination.

15. The method for preparing the catalyst for preparing olefin by dehydrogenating the hydrocarbon raw material according to claim 1, wherein the amount of ammonia gas introduced during the roasting process is 40-60 mL/min.

16. The method of claim 1, wherein the calcination temperature is from 700 ℃ to 900 ℃.

17. The method of claim 16, wherein the calcination temperature is from 800 ℃ to 900 ℃.

18. The method of claim 1, wherein the temperature increase rate is 5-10 ℃/min.

19. The method of claim 1, wherein the temperature rise rate is 5-7.5 ℃/min.

20. The method of producing a catalyst for the dehydrogenation of a hydrocarbon feedstock to olefins according to any one of claims 1 to 19, wherein the catalyst is supported on a carrier.

21. The method of claim 20, wherein the carrier is at least one of alumina and silica or another carrier containing either component.

22. The method of preparing a catalyst for the dehydrogenation of a hydrocarbon feedstock to produce an olefin according to claim 21, wherein the loading step comprises:

recrystallizing a compound raw material capable of providing B, P, S and N elements, formaldehyde and a precursor raw material capable of being converted into a carrier in a solvent, and then roasting a recrystallization product to obtain the catalyst;

or mixing the carrier and the synthesized raw materials, and carrying out recrystallization and roasting treatment to obtain the catalyst.

23. A catalyst for preparing olefin by dehydrogenation of hydrocarbon raw material, which is characterized by being prepared by the preparation method of any one of claims 1 to 22.

24. A method for preparing alkene by hydrocarbon raw material dehydrogenation is characterized in that the hydrocarbon raw material is contacted with the catalyst prepared by the preparation method of any one of claims 1 to 22 to carry out dehydrogenation reaction, so as to prepare a corresponding alkene product;

the hydrocarbon feedstock of claim 1.

25. The process for the dehydrogenation of a hydrocarbon feedstock to produce an alkene according to claim 24 wherein the hydrocarbon feedstock is a compound having the structure of formula 1-1;

formula 1-1

In the formula 1-1, R₁Is H, C₁~C₆Alkyl, phenyl or substituted phenyl of (a); the benzene ring of the substituted phenyl contains C₁~C₆Alkyl of (C)₁~C₆At least one substituent of alkoxy, halogen, phenyl, nitro and trifluoromethyl.

26. The process for the dehydrogenation of a hydrocarbon feedstock to produce an alkene of claim 24 or claim 25,

the dehydrogenation reaction is carried out under anhydrous condition; or under an atmosphere containing weak oxygen; alternatively, the dehydrogenation reaction is carried out in an oxygen-free atmosphere or an oxygen-free atmosphere.

27. The method of dehydrogenating a hydrocarbon feedstock to produce an alkene of claim 26, wherein the temperature of the dehydrogenation reaction is in the range of 500 ℃ to 700 ℃.

28. The method of dehydrogenating a hydrocarbon feedstock to produce an alkene of claim 27 wherein the temperature of the dehydrogenation reaction is 550 ℃ to 650 ℃.