Catalyst for preparing styrene through ethylbenzene dehydrogenation as well as preparation method and application of catalyst

Abstract

The invention relates to the technical field of catalysts and provides a catalyst for preparing styrene through ethylbenzene dehydrogenation as well as a preparation method and application of the catalyst. The surface of the catalyst contains an element C and an element H, the total mass of the element C and the element H on the surface of the catalyst accounts for 0.1-12% of the mass of the catalyst, and the mass ratio of the element H to the element C on the surface of the catalyst is 1: (15-200). The catalyst provided by the invention is used in a reaction for preparing styrene by ethylbenzene dehydrogenation, has high styrene selectivity under high catalytic activity, and has a good technical effect.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more specifically to a catalyst for preparing styrene by dehydrogenating ethylbenzene, and a preparation method and application thereof. Background Art

[0002] Styrene is an important chemical raw material with a wide range of uses. The global styrene production capacity is nearly 40 million tons. The main production method of styrene is to use ethylbenzene as the raw material and catalytically dehydrogenate it in the presence of steam to produce styrene, namely the ethylbenzene catalytic dehydrogenation method, which accounts for about 85% of styrene production capacity.

[0003] For the catalytic reaction process of ethylbenzene dehydrogenation to produce styrene, the performance level of the catalyst plays an important role in the technical indicators of the production process. Among them, the styrene selectivity of the ethylbenzene dehydrogenation reaction determines the material consumption of the production process and has an important impact on the economy of the ethylbenzene dehydrogenation production process.

[0004] Most of the existing ethylbenzene dehydrogenation catalysts are based on Fe-K-Ce series catalysts, and also contain other metal oxides as structural stabilizers or electronic additives. CN115487833A discloses an ethylbenzene dehydrogenation catalyst, which introduces at least one component of TeO2 and B2O3, In2O3 and Ga2O3 on the basis of Fe-K-Ce-Mo-Ca, and is used in the ethylbenzene dehydrogenation reaction to improve the selectivity of styrene. CN106582689A discloses a technical solution of adding In2O3 on the basis of a Fe-K-Ce-W-Mg-Ca catalyst system, and adding at least one of HfO2, Nb2O5 or Ta2O5, thereby improving the catalyst selectivity.

[0005] However, the above catalysts, when applied to ethylbenzene dehydrogenation reaction, have the problem of insufficient selectivity of the product styrene to varying degrees, resulting in decreased economic benefits. Therefore, it is necessary to develop an ethylbenzene dehydrogenation catalyst with higher selectivity for styrene to reduce the material consumption of the device and increase economic benefits. Summary of the invention

[0006] The object of the present invention is to provide a catalyst for preparing styrene by dehydrogenating ethylbenzene and a preparation method thereof, so as to solve the technical problems that the catalyst for preparing styrene by dehydrogenating ethylbenzene in the prior art has more by-products and lower styrene selectivity.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a catalyst for dehydrogenating ethylbenzene to produce styrene, wherein the catalyst surface contains C elements and H elements, the total mass of the C elements and H elements on the catalyst surface accounts for 0.1 to 12% of the catalyst mass, and the mass ratio of the H elements to the C elements on the catalyst surface is 1:(15 to 200).

[0009] The inventors found in their research that a certain amount of carbon deposits on the surface of the catalyst used for the dehydrogenation of ethylbenzene to produce styrene can significantly improve the catalyst's selectivity for styrene. This may be because the carbon deposits on the surface of the catalyst adjust the surface properties of the catalyst, cover part of the active sites where side reactions occur, and reduce the generation of by-products. Furthermore, when the mass ratio of H element to C element in the carbon deposits is 1: (15-200), the catalyst will have a more ideal selectivity for styrene. This may be because carbon deposits with an appropriate amount of H content also have the performance of highly selectively catalyzing the dehydrogenation of ethylbenzene. In addition, carbon deposits with an appropriate amount of H content may promote the desorption of product styrene, thereby reducing product cracking and significantly improving the catalyst's selectivity for styrene.

[0010] According to some embodiments of the present invention, the total mass of the C element and the H element on the catalyst surface accounts for 0.5-6% of the mass of the catalyst.

[0011] According to some embodiments of the present invention, the mass ratio of H element to C element on the catalyst surface is 1:(30-100).

[0012] According to some embodiments of the present invention, the catalyst further includes Fe element, K element, Ce element, Mo element and alkaline earth metal element.

[0013] According to some embodiments of the present invention, in the catalyst, the elements are calculated as oxides, based on the mass of the catalyst, the content of Fe2O3 is 60-78wt%, the content of K2O is 8-14wt%, the content of CeO2 is 4-11wt%, the content of MoO3 is 0.5-5wt%, and the content of alkaline earth metal oxide is 0.2-6wt%.

[0014] According to some embodiments of the present invention, the alkaline earth metal is selected from Ca and / or Mg, preferably Ca.

[0015] In a second aspect, the present invention provides a method for preparing the catalyst described in the first aspect, comprising: mixing catalyst raw materials including Fe source, K source, Ce source, Mo source, alkaline earth metal source and optional pore-forming agent, molding, calcining, and then using hydrocarbon gas for chemical vapor deposition treatment, the treatment temperature is 720-850°C, the time is 0.5-48h, to obtain the catalyst.

[0016] The preparation method of the catalyst provided in the present invention uses hydrocarbon gas to perform chemical vapor deposition on the formed catalyst under appropriate conditions, so that the catalyst surface contains an appropriate amount of carbon deposits and a certain ratio of H element to C element. The catalyst prepared by the preparation method provided by the present invention is suitable for the reaction of dehydrogenating ethylbenzene to prepare styrene, and has the characteristics of high selectivity.

[0017] It should be noted that the "chemical vapor deposition" in the present invention refers to a process in which gaseous substances (hydrocarbon gases) react on the surface of a catalyst to generate solid deposits of carbon.

[0018] According to some embodiments of the present invention, the hydrocarbon gas includes at least one of alkane gas, olefin gas and alkyne gas.

[0019] According to some embodiments of the present invention, the hydrocarbon gas includes at least one of olefin gas and alkyne gas.

[0020] According to some embodiments of the present invention, the chemical vapor deposition process is performed at a temperature of 720 to 800° C. and for a time of 1 to 6 hours.

[0021] According to some embodiments of the present invention, the Fe source is selected from Fe oxides, preferably selected from red iron oxide and / or yellow iron oxide.

[0022] According to some embodiments of the present invention, the K source is selected from potassium salts, preferably selected from one or more of potassium carbonate, potassium nitrate and potassium bicarbonate.

[0023] According to some embodiments of the present invention, the Ce source is selected from cerium salts, preferably one or more selected from cerium nitrate, cerium oxalate, and cerium carbonate.

[0024] According to some embodiments of the present invention, the Mo source is selected from molybdenum salts and / or molybdenum oxides, preferably selected from one or more of ammonium molybdate and molybdenum oxide.

[0025] According to some embodiments of the present invention, the alkaline earth metal source is selected from one or more of alkaline earth oxides and alkaline earth metal hydroxides.

[0026] According to some embodiments of the present invention, the pore former is selected from one or more of activated carbon, graphite, sodium hydroxymethyl cellulose and polystyrene microspheres.

[0027] According to some embodiments of the present invention, the amount of the pore former is 0.01 to 5 wt % of the total mass of the catalyst raw material.

[0028] According to some embodiments of the present invention, the calcination conditions include: a temperature of 600 to 1000° C. and a time of 2 to 24 hours.

[0029] According to some embodiments of the present invention, the preparation method further comprises: contacting the catalyst raw material with water, kneading into a shape, drying, and calcining to obtain the catalyst.

[0030] In the present invention, a proper amount of water can be added to the catalyst raw material before kneading. The water addition method is generally slow addition, and the amount of water added is not particularly limited. It can be adjusted according to the dryness and wetness of the material. Generally, the amount of water added accounts for 15-35% of the total mass of the mixed material.

[0031] In the present invention, the molding can be performed by extrusion molding to obtain particles with a diameter of 2 to 5 mm and a length of 3 to 10 mm.

[0032] According to some embodiments of the present invention, the drying conditions include: a temperature of 30 to 160° C. and a time of 1 to 24 hours.

[0033] In a third aspect, the present invention provides use of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the dehydrogenation of ethylbenzene to prepare styrene.

[0034] In a fourth aspect, the present invention provides a method for preparing styrene by dehydrogenating ethylbenzene, comprising: contacting ethylbenzene with the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the presence of water vapor to cause a dehydrogenation reaction to produce styrene.

[0035] In the present invention, ethylbenzene is fully mixed with water vapor and then contacted with the catalyst.

[0036] According to some embodiments of the present invention, the reaction temperature is 550-640°C.

[0037] According to some embodiments of the present invention, the absolute pressure of the reaction is 30-100 kPa.

[0038] According to some embodiments of the present invention, the mass space velocity of ethylbenzene is 0.2 to 2.0 h -1 .

[0039] The beneficial effects of the present invention are at least:

[0040] The catalyst provided by the invention is used in the reaction of preparing styrene by dehydrogenating ethylbenzene, can have high styrene selectivity under high catalytic activity, and has good technical effect. DETAILED DESCRIPTION

[0041] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0042] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0043] In each embodiment and comparative example of the present invention, the amount of catalyst carbon deposits (the total mass of C elements and H elements on the catalyst surface) and the H / C mass ratio were tested using a Vario EL III element analyzer, and the decomposition temperature was 950°C.

[0044] Example 1

[0045] Weigh 70.5 parts of red iron oxide equivalent to Fe2O3, 10.2 parts of potassium carbonate equivalent to K2O, 9.8 parts of cerium nitrate equivalent to CeO2, 3.2 parts of ammonium molybdate equivalent to MoO3, 2.2 parts of calcium hydroxide equivalent to CaO and 1.8 parts of sodium hydroxymethyl cellulose, add to the mixer and stir for 2 hours until the mixture is uniform. Then add 24% of the total weight of deionized water of the dehydrogenation catalyst raw material and mix for 2 hours. Then extrude and pelletize the above mixture to obtain particles with a diameter of 3 mm and a length of 6 mm, put them into an oven, dry them at 80°C for 4 hours, dry them at 160°C for 4 hours, then place them in a muffle furnace, roast them at 800°C for 4 hours, and then use a mass space velocity of 50h -1 The catalyst was treated with acetylene at 750 °C for 3 h.

[0046] The catalyst composition is shown in Table 1.

[0047] Example 2

[0048] Weigh 65.2 parts of red iron oxide equivalent to Fe2O3, 13.6 parts of potassium carbonate equivalent to K2O, 7.8 parts of cerium nitrate equivalent to CeO2, 4.2 parts of ammonium molybdate equivalent to MoO3, 5.6 parts of calcium hydroxide equivalent to CaO and 1.8 parts of sodium hydroxymethyl cellulose, add to the mixer and stir for 2 hours until the mixture is uniform. Then add 24% of the total weight of deionized water of the dehydrogenation catalyst raw material and mix for 2 hours. Then extrude and pelletize the above mixture to obtain particles with a diameter of 3 mm and a length of 6 mm, put them into an oven, dry them at 80°C for 4 hours, dry them at 160°C for 4 hours, then place them in a muffle furnace, roast them at 800°C for 4 hours, and then use a mass space velocity of 50h -1 The catalyst was treated with acetylene at 800 °C for 2 h.

[0049] The catalyst composition is shown in Table 1.

[0050] Example 3

[0051] Weigh 74.3 parts of red iron oxide equivalent to Fe2O3, 9.4 parts of potassium carbonate equivalent to K2O, 10.1 parts of cerium nitrate equivalent to CeO2, 0.9 parts of ammonium molybdate equivalent to MoO3, 1.8 parts of magnesium hydroxide equivalent to MgO and 2.5 parts of sodium hydroxymethyl cellulose, add to the mixer and stir for 2 hours until the mixture is uniform. Then add 24% of the total weight of the dehydrogenation catalyst raw material and mix for 2 hours. Then extrude and pelletize the above mixture to obtain particles with a diameter of 3 mm and a length of 6 mm, put them into an oven, dry them at 80°C for 4 hours, dry them at 160°C for 4 hours, then place them in a muffle furnace, roast them at 800°C for 4 hours, and then use a mass space velocity of 50h -1 The catalyst was treated with acetylene at 720 °C for 4 h.

[0052] The catalyst composition is shown in Table 1.

[0053] Example 4

[0054] The preparation method of the catalyst is similar to that of Example 1, except that the mass space velocity is 50 h -1 The catalyst was treated with acetylene at 850 °C for 10 h.

[0055] The catalyst composition is shown in Table 1.

[0056] Example 5

[0057] The preparation method of the catalyst is similar to that of Example 1, except that acetylene is replaced by ethylene.

[0058] The catalyst composition is shown in Table 1.

[0059] Example 6

[0060] The preparation method of the catalyst is similar to that of Example 1, except that sodium hydroxymethyl cellulose is not added.

[0061] The catalyst composition is shown in Table 1.

[0062] Comparative Example 1

[0063] The preparation method of the catalyst is similar to that of Example 1, except that the catalyst is not treated with acetylene.

[0064] The catalyst composition is shown in Table 1.

[0065] Comparative Example 2

[0066] The preparation method of the catalyst is similar to that of Example 1, except that the temperature of the acetylene treatment catalyst is 600°C.

[0067] The catalyst composition is shown in Table 1.

[0068] Comparative Example 3

[0069] The preparation method of the catalyst is similar to that of Example 1, except that the temperature of the catalyst treated with acetylene is 900°C.

[0070] The catalyst composition is shown in Table 1.

[0071] Comparative Example 4

[0072] The preparation method of the catalyst is similar to that of Example 1, except that the catalyst is treated with acetylene for 72 hours.

[0073] The catalyst compositions of the embodiments and comparative examples are shown in Table 1.

[0074] Table 1

[0075]

[0076] Catalyst performance evaluation

[0077] The reaction performance of ethylbenzene dehydrogenation to prepare styrene was evaluated in a negative pressure isothermal fixed bed. The specific process is as follows:

[0078] 100 ml of catalyst was loaded into the reactor, and deionized water and ethylbenzene were respectively input into the preheating mixer through metering pumps. After preheating and mixing into gaseous state, they entered the reactor. The reactor was heated by electric heating wire to reach the predetermined temperature. At 60 kPa (absolute pressure) and the mass space velocity of ethylbenzene was 1.0 h -1 The reaction was carried out under the conditions of reaction temperature of 600°C and water ratio of 1.3 (mass ratio of water to ethylbenzene). The reactants flowing out of the reactor were condensed with water and then analyzed for their composition by gas chromatography. The results are shown in Table 2.

[0079] The ethylbenzene conversion rate and styrene selectivity are calculated according to the following formula:

[0080]

[0081]

[0082] Styrene yield % = ethylbenzene conversion % * styrene selectivity %.

[0083] Table 2

[0084] Group Ethylbenzene conversion rate (%) Styrene selectivity (%) Styrene yield (%) Example 1 74.8 97.9 73.23 Example 2 74.5 97.8 72.86 Example 3 74.7 97.8 73.06 Example 4 73.6 97.2 71.54 Example 5 73.7 97.5 71.86 Example 6 74.3 97.4 72.37 Comparative Example 1 73.5 93.7 68.87 Comparative Example 2 73.2 94.6 69.25 Comparative Example 3 73.1 95.4 69.74 Comparative Example 4 72.8 95.0 69.16

[0085] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A catalyst for dehydrogenating ethylbenzene to produce styrene, characterized in that: The catalyst surface contains C elements and H elements, the total mass of the C elements and H elements on the catalyst surface accounts for 0.1-12% of the catalyst mass, and the mass ratio of the H elements to the C elements on the catalyst surface is 1:(15-200).

2. The catalyst according to claim 1, characterized in that The total mass of C and H elements on the catalyst surface accounts for 0.5-6% of the catalyst mass; And / or, the mass ratio of H element to C element on the catalyst surface is 1:(30-100).

3. The catalyst according to claim 1 or 2, characterized in that The catalyst also includes Fe, K, Ce, Mo and alkaline earth metal elements; Preferably, In the catalyst, the elements are calculated as oxides, based on the mass of the catalyst, the content of Fe2O3 is 60-78wt%, the content of K2O is 8-14wt%, the content of CeO2 is 4-11wt%, the content of MoO3 is 0.5-5wt%, and the content of alkaline earth metal oxide is 0.2-6wt%; And / or, the alkaline earth metal is selected from Ca and / or Mg, preferably Ca.

4. The method for preparing the catalyst according to any one of claims 1 to 3, characterized in that: include: The catalyst raw materials including Fe source, K source, Ce source, Mo source, alkaline earth metal source and optional pore-forming agent are mixed, formed, calcined, and then treated by chemical vapor deposition method using hydrocarbon gas at a treatment temperature of 720-850° C. and a time of 0.5-48 hours to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that: The hydrocarbon gas includes at least one of alkane gas, olefin gas and alkyne gas.

6. The preparation method according to claim 4 or 5, characterized in that: The chemical vapor deposition method is used for treatment at a temperature of 720 to 800° C. and for a time of 1 to 6 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The Fe source is selected from Fe oxides, preferably iron oxide red and / or iron oxide yellow; And / or, the K source is selected from potassium salts, preferably one or more selected from potassium carbonate, potassium nitrate, potassium bicarbonate; And / or, the Ce source is selected from cerium salts, preferably one or more selected from cerium nitrate, cerium oxalate, and cerium carbonate; And / or, the Mo source is selected from molybdenum salts and / or molybdenum oxides, preferably selected from one or more of ammonium molybdate and molybdenum oxide; And / or, the alkaline earth metal source is selected from one or more of alkaline earth oxides and alkaline earth metal hydroxides; and / or, the pore-forming agent is selected from one or more of activated carbon, graphite, sodium hydroxymethyl cellulose and polystyrene microspheres; And / or, the amount of the pore former used is 0.01 to 5 wt % of the total mass of the catalyst raw material.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The calcination conditions include: a temperature of 600 to 1000° C. and a time of 2 to 24 hours; And / or, the preparation method further comprises: contacting the catalyst raw material with water, kneading into a shape, drying, and calcining to obtain the catalyst; preferably, the drying conditions include: a temperature of 30 to 160° C. and a time of 1 to 24 hours.

9. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8 in the dehydrogenation of ethylbenzene to prepare styrene.

10. A method for preparing styrene by dehydrogenating ethylbenzene, characterized in that: include: Ethylbenzene is contacted with the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8 in the presence of water vapor to undergo a dehydrogenation reaction to obtain styrene; Preferably, The reaction temperature is 550-640°C; And / or, the absolute pressure of the reaction is 30 to 100 kPa; And / or, the mass space velocity of ethylbenzene is 0.2 to 2.0 h -1 .

Images