CN108097260B

CN108097260B - Catalyst for preparing styrene by ethylbenzene dehydrogenation and preparation method thereof

Info

Publication number: CN108097260B
Application number: CN201611055115.6A
Authority: CN
Inventors: 杨红强; 全民强; 姚文君; 王学丽; 程浩; 王斌; 何崇慧; 刘俊涛; 王继龙
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2016-11-25
Filing date: 2016-11-25
Publication date: 2021-03-30
Anticipated expiration: 2036-11-25
Also published as: CN108097260A

Abstract

The invention relates to a catalyst for preparing styrene by ethylbenzene dehydrogenation and a preparation method thereof, wherein the catalyst comprises the following components in percentage by mass: a) 65-75% of potassium ferrite composite oxide, in terms of K₂Fe₁₀O₁₆Counting; b) 1-4% of K oxide, with K₂Measuring O; c) 6-12% of Ce oxide, CeO₂Counting; d)0.6 to 4% of W oxide, in the presence of WO₃Counting; e) 2-6% of oxides of Mg or/and Ca, calculated as MgO or/and CaO; f) 2-4% of at least one alkali metal oxide selected from Rb and Cs. The catalyst has good activity, high styrene yield and styrene selectivity under the condition of low water ratio, and good stability.

Description

Catalyst for preparing styrene by ethylbenzene dehydrogenation and preparation method thereof

Technical Field

The invention relates to a catalyst for preparing styrene by ethylbenzene dehydrogenation under a low water ratio and a preparation method thereof.

Background

The ethylbenzene catalytic dehydrogenation reaction is a reversible process with increased molecular number and strong heat absorption, and needs to be carried out under the conditions of high-temperature and low-pressure reaction. In order to increase the ethylbenzene conversion and styrene yield in the dehydrogenation of ethylbenzene, it is customary in industry to introduce large quantities of superheated steam into the process. The water vapor mainly plays three roles, (1) is used as a heat source to provide heat for high-temperature reaction, so that the ethylbenzene is prevented from being heated to a higher temperature, and the occurrence of side reaction is inhibited; (2) as a diluent, the ethylbenzene partial pressure is reduced, and the reaction is promoted to move towards the product; (3) the water gas reaction is carried out, the carbon deposit on the surface of the catalyst is removed, and the catalyst is automatically regenerated. However, the addition of the water vapor is limited by two factors of the allowable pressure drop of a reaction system and energy consumption, and the production of the styrene consumes a large amount of water vapor, so that the energy consumption is high, the product condensation amount is large, and the process equipment cost is high, which is an important reason for keeping the production cost high. Therefore, advanced ethylbenzene dehydrogenation processes seek to obtain higher styrene yield with a lower water ratio (mass ratio of steam to ethylbenzene in the feed), and the low water ratio operation is one of important measures for saving energy and reducing consumption of a styrene device.

When the conventional ethylbenzene dehydrogenation catalyst reacts under the condition that the water ratio is less than 2.0, the water gas reaction is slow, the carbon deposition on the surface of the catalyst is increased, and the stability and the activity of the catalyst are reduced, which is the biggest problem for developing the low-water-ratio catalyst, and the main direction for developing the low-water-ratio catalyst is to emphasize the improvement of the carbon deposition resistance, the carbon removal capability and the catalyst stability of the catalyst. Patent CN200510111471.0(CN1981929) discloses a low water ratio ethylbenzene dehydrogenation catalyst, which comprises the following components in percentage by weight: (a) 60-80% Fe₂O₃(ii) a (b)6 to 11% of K₂O; (c) 6-11% of CeO₂(ii) a (d) 0.5-5% of WO₃(ii) a (e) At least two light rare earth compounds except cerium, the content of which is 0.1-10% by oxide; (f)0.001 to 7% of at least one oxide selected from the group consisting of Ca, Mg, Ba, B, Sn, Pb, Cu, Zn, Ti, Zr, V and Mo; wherein Portland cement is not added in the preparation process of the catalyst. The catalyst component is that at least two light rare earth compounds except Ce are added into a Fe-K-Ce-W system as promoters, and at least one metal oxide selected from Ca, Mg, Ba, B, Sn, Pb, Cu, Zn, Ti, Zr, V or Mo is added at the same time; the catalyst is prepared by a dry mixing method, namely all the components are uniformly mixed, and then deionized water is added for kneading, extruding, granulating, drying and roasting to obtain a catalyst finished product; the catalyst has a water ratio1.8, the activity and stability of the catalyst at low water ratios could not be fully reacted. Patent CN200710039046.4(CN101279266) discloses an energy-saving ethylbenzene dehydrogenation catalyst, which comprises the following components in percentage by weight: (a) 60-81% Fe₂O₃(ii) a (b)7 to 12% of K₂O; (c) 6-11% of CeO₂(ii) a (d) 0.5-5% of WO₃(ii) a (e)0.5 to 5% of MgO; (f) 1-5% of NiO; (g) the catalyst contains at least one light rare earth component except cerium, and the content of the light rare earth component is 0.5-5% by weight of oxide; (h) the balance being binder. The method of adding NiO and another light rare earth oxide into the Fe-K-Ce-W-Mg system is adopted to solve the problems that the low-potassium catalyst is easy to deposit carbon and has poor stability under the condition of low water ratio, and the catalyst is prepared by a dry mixing method; at the temperature of 620 ℃ and the space velocity of 1.0h^-1The water ratio is 1.6, the ethylbenzene conversion rate of the catalyst is 75 percent, the styrene selectivity is 95 percent under normal pressure, and the conversion rate is reduced by 0.5 percent after the catalyst continuously operates for 450 hours. The patent CN200910057803.x discloses a low water ratio ethylbenzene dehydrogenation catalyst, which is prepared by adding Rb compound and at least one selected from medium rare earth oxide Pm in Fe-K-Ce-W-Ca system₂O₃、Eu₂O₃、Gd₂O₃Or Dy₂O₃The technical scheme of (1) solves the problem that the low-potassium catalyst has poor stability under the condition of low water ratio, and the catalyst is prepared by adopting a dry mixing method; the Ce is added in the form of cerium oxalate or cerium carbonate instead of cerium nitrate without adding a binder, so that on one hand, the alkalinity of the system is improved, the acid and the alkali in the catalyst are more matched, the higher activity is favorably kept, and meanwhile, the catalyst has good crushing strength; on the other hand, rubidium compounds are used for replacing partial potassium compounds, so that the stability of the alkali metal compounds in the process of ethylbenzene catalytic dehydrogenation reaction is improved, the rate of water gas reaction between water vapor and carbon deposits on the surface of the catalyst is accelerated, and the self-regeneration capacity of the catalyst is enhanced. The catalyst is at normal pressure and space velocity of 1.0h^-1The reaction is carried out for 500 hours at the temperature of 620 ℃ and the water ratio of 1.5, the conversion rate of the ethylbenzene is maintained at 75 percent, and the selectivity of the styrene is 95 percent; similarly, European patents 0177832, CN101829576A, CN102040466A, CN103028419A, CN101279263, CN10142273. Patent CN200910057807.8 discloses a low water ratio ethylbenzene dehydrogenation catalyst, which is a catalyst formed by adding at least one element of La, Pr, Nd, Pm, Sm, Th, Pa or Yb in a Fe-K-Ce-Mo system, and solves the problem of poor stability of a low potassium catalyst under the condition of low water ratio; at the temperature of 620 ℃ and the space velocity of 1.0h^-1And the water ratio is 1.6, the stability of the catalyst reaches 1000 hours. Patent CN200910201627.2 discloses a method for preparing styrene by ethylbenzene dehydrogenation, which adds Rb compound and at least one selected from Pm in Fe-K-Ce-W-Ca system₂O₃、Eu₂O₃、Gd₂O₃Or Dy₂O₃The catalyst prepared by the medium rare earth oxide solves the problems of low strength and poor stability of the low-potassium catalyst under the condition of low water ratio; the catalyst is prepared by a dry mixing method, and rubidium compound and medium rare earth oxide Pm are added into an iron-potassium-cerium-tungsten-calcium catalytic system₂O₃、Eu₂O₃、Gd₂O₃Or Dy₂O₃The Ce is added in the form of cerium oxalate or cerium carbonate instead of cerium nitrate, so that on one hand, the alkalinity of the system is improved, the acid and the alkali in the catalyst are more matched, the higher activity is kept, and meanwhile, the catalyst has good crushing strength; on the other hand, rubidium compounds are used for replacing partial potassium compounds, so that the stability of the alkali metal compounds in the process of ethylbenzene catalytic dehydrogenation reaction is improved, the rate of water gas reaction between water vapor and carbon deposits on the surface of the catalyst is accelerated, the self-regeneration capacity of the catalyst is enhanced, and the performance of the catalyst is basically maintained after the catalyst is used for 1000 hours. The patent CN201010261733.2 discloses a low water ratio ethylbenzene dehydrogenation catalyst and a preparation method thereof, wherein a Cs compound and at least one selected from medium rare earth oxide Sm are added into an Fe-K-Ce-W-Mg system₂O₃、Eu₂O₃、Gd₂O₃Or Dy₂O₃The technical scheme of (1) solves the problem that the low-potassium catalyst has poor stability under the condition of low water ratio; at the temperature of 620 ℃ and the space velocity of 1.0h^-1The water ratio is 1.5, the conversion rate reaches 74.6 percent and the selectivity is kept at 95.2 percent after the catalyst operates for 500 hours under the normal pressure condition; the inventionSimilar to CN200910201627.2, patent CN201410778920.6 discloses a preparation method of a catalyst for preparing styrene by ethylbenzene dehydrogenation at a low water ratio, which solves the problem of low activity of the catalyst under the condition of low water ratio by adding Rb and Cs compounds and La, Pr and Nb light rare earth oxides except Ce in an Fe-K-Ce-Mo-Mg-Ca system. The surface acidity of the catalyst is reduced and the water absorption of the surface of the catalyst is enhanced by modifying the surface of the catalyst with alkali metal and light rare earth metal ions except Ce, so that the reaction rate of water and gas on the surface of the catalyst is increased, and the stability of the catalyst under a low water ratio reaction process is improved; the catalyst is suitable for a low-water-ratio reaction process, and the problems of low activity and low stability of the catalyst caused by the reduction of the water vapor content in the low-water-ratio reaction process are effectively solved. The invention solves the problem of the deactivation of carbon deposition on the surface of the catalyst, and does not relate to the problem of the deactivation of carbon deposition generated in the active phase potassium ferrite of the catalyst. On a 4L adiabatic negative pressure evaluation device, the temperature of a first reaction inlet 610 ℃, the temperature of a second reaction inlet 615 ℃, the water ratio of 1.2 and the liquid space velocity of 0.42h^-1And under the condition that the secondary reaction outlet pressure is 40KPa, the ethylbenzene conversion rate is more than or equal to 65.6 percent, but the potassium content is higher, so that the catalyst is easy to have a plurality of problems of poor stability, poor selectivity and the like caused by potassium loss in the later reaction stage.

The method for improving the reaction rate of water gas on the surface of a catalyst and reducing the carbon deposition on the surface of the catalyst by adding a cocatalyst component is an important way for improving the stability of the low-water-ratio ethylbenzene dehydrogenation catalyst in the prior document, but the process condition for evaluating the stability of the catalyst cannot be matched with the current production technology (the water ratio of a low-water-ratio styrene production device is generally about 1.3, the evaluation condition of the catalyst in the document is generally more than 1.5), and the loss of the activity of the catalyst caused by the low-water-ratio reaction process is not improved. Therefore, how to inhibit carbon deposition and prevent reduction of active phase in the low water ratio reaction process, and improve the activity and stability of the catalyst and reduce energy consumption are still problems to be solved urgently by scientific researchers.

Disclosure of Invention

The invention provides a catalyst for preparing styrene by ethylbenzene dehydrogenation and a preparation method thereof, and solves the technical problems that the bulk density and radial crushing resistance of a low-potassium catalyst in a low water ratio reaction process in the prior art are poor, and the catalyst is poor in stability and selectivity caused by potassium loss easily in the later reaction stage.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a catalyst for preparing styrene by ethylbenzene dehydrogenation with low water ratio comprises the following components in percentage by mass:

a) 65-75% of potassium ferrite composite oxide, in terms of K₂Fe₁₀O₁₆Counting;

b) 1-4% of K oxide, with K₂Measuring O;

c) 6-12% of Ce oxide, CeO₂Counting;

d)0.6 to 4% of W oxide, in the presence of WO₃Counting;

e) 2-6% of oxides of Mg or/and Ca, calculated as MgO or/and CaO;

f) 2-4% of at least one alkali metal oxide selected from Rb and Cs, wherein Rb is used as the alkali metal oxide₂O、Cs₂O, wherein the alkali metal oxide is modified on the surface of the potassium ferrite oxide in the form of a salt solution;

g) 1.5-4% of at least one light rare earth metal oxide selected from La, Pr and Nd except Ce, respectively La₂O₃、Pr₂O₃、Nd₂O₃Wherein, the light rare earth metal oxide is modified on the surface of the catalyst in the form of salt solution;

h)0.3 to 2.5% of Mn oxide with MnO₂Counting;

i) 0.3-2.5% of Zn oxide (calculated as ZnO);

j)0.3 to 2.5% of Sn oxide, SnO₂And (6) counting.

The preparation process of the catalyst is as follows:

1) purifying an iron source, namely roasting the iron oxide red for 1-10 hours at 500-1000 ℃ to remove impurities and water in the iron oxide red;

2) preparing Mg and Ca ion doped potassium ferrite oxide precursor I according to the original iron and potassiumWeighing all iron raw material iron oxide red according to the material mass ratio of 5:1, sequentially adding 10-50% of potassium raw material and 10-60% of Mg and Ca raw material, carrying out dry mixing for 1-5 hours, roasting at 500-1000 ℃ for 1-10 hours, and adding alkali metal oxide Rb₂O、Cs₂Modifying the surface of the potassium ferrite oxide with O in the form of nitrate solution by adopting a spraying method to form a precursor I;

3) and (2) preparing a precursor II, grinding or crushing the precursor I to 50-100 meshes, adding the Ce, W, Mn, Zn and Sn cocatalyst raw materials and the rest K, Mg and Ca raw materials according to the content ratio, dry-mixing for 1-5 hours, adding deionized water to prepare a paste which is viscous and suitable for extrusion, extruding and cutting into particles with the diameter of about 3 mm and the length of 6-8 mm, and drying for 1-10 hours at 80-150 ℃ to form the precursor II.

4) And (3) preparing a finished catalyst, namely modifying a salt solution of La, Pr and Nd light rare earth metal oxides except Ce on a catalyst precursor II by adopting an impregnation method or a spraying method, drying at 80-120 ℃ for 2-8 hours, and roasting at 500-1000 ℃ for 2-8 hours to obtain a finished catalyst.

In the preparation process of the catalyst, except the main component, a pore-forming agent is preferably added, the dosage of the pore-forming agent is 1-10% of the weight of the catalyst, and the pore-forming agent can be selected from graphite, polystyrene fiber spheres (PS) and carboxymethyl cellulose (CMC), and is preferably carboxymethyl cellulose.

In the above technical scheme, K₂Fe₁₀O₁₆The content optimization scheme is 70-75%; k₂The preferable scheme of the O content is 1-3%; CeO (CeO)₂The content optimization scheme is 6-10%; WO₃The content optimization scheme is 1-4%; the content of alkaline earth metal oxide MgO or/and CaO is preferably 2-4%; alkali metal oxide Rb₂O or/and Cs₂The content of O is preferably 2-3%; the preferred scheme of the light rare earth metal oxide except Ce is La₂O₃The content is preferably 2-3%; MnO₂The content optimization scheme is 0.5-2%; the preferable scheme of the ZnO content is 0.5-2%; SnO₂The content is preferably 0.5-2%.

In the catalyst of the present invention, a baseMetal oxide Rb₂O、Cs₂O is modified on the surface of potassium ferrite oxide in the form of nitrate solution by adopting a spraying method, and light rare earth metal oxide La except Ce₂O₃、Pr₂O₃、Nd₂O₃The catalyst surface is modified by adopting an immersion method or a spraying method in the form of nitrate solution, and potassium ferrite oxide and the catalyst surface are modified by alkali metal and light rare earth metal ions, so that the specific surface area and the dispersion degree of active components of the catalyst are effectively improved, the problem of deactivation of carbon deposition on the catalyst surface caused by excessive carbon deposition under the working condition of low water ratio is solved, the side reaction is reduced, and the selectivity of the target product styrene is improved.

The oxides of Mn, Zn and Sn are necessary components of the catalyst, and the conversion rate of ethylbenzene under the working condition of low water ratio is improved through the synergistic effect of the oxide combination.

The dehydrogenation catalyst prepared by the method can be completely suitable for preparing styrene, divinylbenzene and 1-methyl styrene from ethylbenzene, diethylbenzene and 1-methyl ethylbenzene under certain process conditions.

The ethylbenzene dehydrogenation catalyst prepared by the method is subjected to activity evaluation in a 4L adiabatic negative pressure side line device, and the process is briefly described as follows:

the 4L adiabatic negative pressure lateral line device totally 2 sections of reactors, 2L catalyst is filled in every reactor, and the heat preservation divides the heating of three sections outward with the electric heat silk, makes the temperature of heat preservation be close to the temperature of reactor bed to guarantee adiabatic effect, and is equipped with the heating iron plate in the upper and lower position of reactor, and the iron plate plays the effect of adjusting reaction raw materials temperature and preventing axial heat loss. A mixer is arranged in front of an inlet of the first-stage reactor to ensure that two feeds of water and ethylbenzene can be fully mixed before reaction to meet the reaction requirement.

The feeding amount of reaction raw material water and ethylbenzene is controlled by a metering pump, water accounting for about 60% of total water inflow enters a vaporizer and a superheater after passing through a pump, the water is heated to above 600 ℃ to become superheated steam, in addition, water accounting for about 40% of total water amount and the raw material ethylbenzene enter the vaporizer and the superheater after being mixed by the pump, the superheated steam with the temperature of above 600 ℃ enters a mixer together, after two materials are uniformly mixed, an iron block is heated through the upper part of a first-stage reactor, so that the reaction mixed gas reaches the temperature required by the reaction, enters a catalyst bed layer, the dehydrogenation reaction is carried out, and after the first-stage dehydrogenation reaction, the temperature of the reaction materials is obviously reduced. Then heating by the upper iron block of the second stage reactor, raising the temperature of the mixed gas to the required temperature, and entering the second stage dehydrogenation reactor. And the outlet product of the second stage reactor is condensed and then enters a gas-liquid separator, non-condensable gas such as hydrogen and the like is pumped out by a vacuum pump and discharged into the atmosphere, and liquid passes through an oil-water separator and then is respectively led into an oil tank and a water tank, wherein the oil tank and the water tank are respectively 2 and can be automatically switched back and forth. And the outlets of the first reactor and the second reactor are respectively provided with a sampler, and the liquid of the two samplers is taken every 8 hours and sent to a gas chromatograph for analysis. The reaction product composition was analyzed by gas chromatography using Shimadzu corporation of Japan (using the corrected area normalization method).

The ethylbenzene conversion and styrene selectivity were calculated according to the following formulas:

under the working condition of low water ratio reaction, the carbon elimination reaction on the surface of the catalyst caused by the great reduction of water vapor in a reaction system is lower than the carbon deposition reaction, so that the activity of the catalyst is reduced rapidly, the ethylbenzene dehydrogenation catalyst is easy to inactivate under the reaction process condition, and the ethylbenzene dehydrogenation catalyst is a full-active component, so that the problems of carbon deposition inactivation can occur on the surface of the catalyst and in the active phase potassium ferrite in the reaction process₂Fe₁₀O₁₆(Mg, Ca ion-doped potassium ferriteOxide) to inhibit the problem of carbon deposition and inactivation in the active phase of potassium ferrite under the working condition of low water ratio, thereby improving the activity of the catalyst. The bulk density and the crushing resistance of the catalyst are also obviously improved; the catalyst is prepared in the form of Mg and Ca ion doped potassium ferrite oxide precursor, so that the potassium content can be effectively reduced; the method of adding the potassium auxiliary agent step by step is adopted to fully play the role of the cocatalyst K, so that the problems of poor catalyst stability, poor selectivity and the like caused by potassium loss of the high-potassium catalyst in the later reaction stage are effectively solved, and the stability and the selectivity of the catalyst in operation under the working condition of low water ratio are improved; the method purifies the iron source-iron oxide red through high-temperature roasting, removes about 3 percent of impurities in the raw materials, oxidizes the reduced metal impurities contained in the raw materials, prevents the reduced metal impurities from entering a main active phase potassium ferrite crystal lattice of the catalyst in the high-temperature roasting process, and reduces the activity of the catalyst; the ethylbenzene dehydrogenation catalyst prepared by the invention is arranged on a 4L adiabatic negative pressure evaluation device, and has the advantages of 623 ℃ at a first reaction inlet, 627 ℃ at a second reaction inlet, 1.05 of water ratio and 0.36h of liquid airspeed^-1And under the condition that the secondary reaction outlet pressure is 40KPa, the catalyst activity is obviously improved, the ethylbenzene conversion rate is more than or equal to 66 percent, the styrene selectivity is more than or equal to 97 percent, the catalyst stability is obviously improved, the inactivation rate is obviously reduced, and a good technical effect is obtained. The invention is further illustrated by the following examples.

Detailed Description

[ example 1 ]

315g of iron oxide red, 58.7g of potassium carbonate, 71.5g of cerium oxalate, 11g of ammonium tungstate, 8g of magnesium oxide, 15.8g of calcium carbonate, 8.9g of rubidium nitrate, 5.9g of cesium nitrate, 9g of lanthanum nitrate, 2.5g of zinc oxide, 2.5g of manganese dioxide, 1.8g of tin dioxide and 30g of carboxymethyl cellulose are respectively weighed, and the preparation steps of the catalyst are as follows: roasting 315g of iron oxide red at 700 ℃ for 4h, adding 42.5g of potassium carbonate, 4g of magnesium oxide and 7.1g of calcium carbonate, dry-mixing for 2h, roasting at 750 ℃ for 4h, preparing 100mL of solution from rubidium nitrate and cesium nitrate, and uniformly spraying the solution on the surface of potassium ferrite oxide by adopting a spraying method to obtain a precursor I; grinding the precursor I to 80 meshes, adding the rest of magnesium oxide, calcium carbonate, potassium carbonate, cerium oxalate, ammonium tungstate, zinc oxide, manganese dioxide, tin dioxide and carboxymethyl cellulose, dry-mixing for 2h, adding 130mL of deionized water, kneading into paste with viscosity and suitable for extrusion, extruding into strips, cutting into particles with the diameter of about 3 mm and the length of 6-8 mm, drying at 120 ℃ for 4 hours, and roasting at 900 ℃ for 4 hours to obtain a precursor II; and preparing 100mL of lanthanum nitrate solution, uniformly spraying the solution on the surface of the precursor II by adopting a spraying method, drying at 100 ℃ for 4 hours, and roasting at 750 ℃ for 4 hours to obtain a catalyst finished product.

[ example 2 ]

340g of iron oxide red, 51.4g of potassium carbonate, 40g of cerium oxalate, 8.2g of ammonium tungstate, 10.5g of magnesium oxide, 20.3g of calcium carbonate, 2.9g of rubidium nitrate, 2.4g of cesium nitrate, 18.9g of lanthanum nitrate, 1.25g of zinc oxide, 1.25g of manganese dioxide, 0.9g of tin dioxide and 30g of carboxymethyl cellulose are respectively weighed, and the preparation step of the catalyst is as follows: roasting iron oxide red at 900 ℃ for 4 hours, adding 38.2g of potassium carbonate, 2.5g of magnesium oxide and 4.5g of calcium carbonate, dry-mixing for 2 hours, roasting at 550 ℃ for 4 hours, preparing 100mL of solution from rubidium nitrate and cesium nitrate, and uniformly spraying the solution on the surface of potassium ferrite oxide by adopting a spraying method to obtain a precursor I; grinding the precursor I to 80 meshes, adding the rest of magnesium oxide, calcium carbonate, potassium carbonate, cerium oxalate, ammonium tungstate, zinc oxide, manganese dioxide, tin dioxide and carboxymethyl cellulose, dry-mixing for 2h, adding 130mL of deionized water, kneading into paste with viscosity and suitable for extrusion, extruding into strips, cutting into particles with the diameter of about 3 mm and the length of 6-8 mm, drying at 120 ℃ for 4 hours, and roasting at 800 ℃ for 4 hours to obtain a precursor II; preparing 100mL of solution from praseodymium nitrate and neodymium nitrate, uniformly loading the solution on the surface of a precursor II by adopting an impregnation method, drying at 100 ℃ for 4 hours, and roasting at 600 ℃ for 4 hours to obtain a catalyst finished product.

[ example 3 ]

315g of iron oxide red, 58.7g of potassium carbonate, 45g of cerium oxalate, 16.4g of ammonium tungstate, 7g of magnesium oxide, 10.5g of calcium carbonate, 10.8g of rubidium nitrate, 9.4g of cesium nitrate, 17.9g of lanthanum nitrate, 5g of zinc oxide, 5g of manganese dioxide, 3.6g of tin dioxide and 30g of carboxymethyl cellulose are respectively weighed, and the preparation steps of the catalyst are as follows: roasting iron oxide red at 500 ℃ for 4h, adding 42.5g of potassium carbonate, 4.5g of magnesium oxide and 8g of calcium carbonate, dry-mixing for 3h, roasting at 850 ℃ for 4h, preparing 100mL of solution from rubidium nitrate and cesium nitrate, and uniformly spraying the solution on the surface of potassium ferrite oxide by adopting a spraying method to obtain a precursor I; grinding the precursor I to 80 meshes, adding the rest of magnesium oxide, calcium carbonate, potassium carbonate, cerium oxalate, ammonium tungstate, zinc oxide, manganese dioxide, tin dioxide and carboxymethyl cellulose, dry-mixing for 2h, adding 130mL of deionized water, kneading into paste with viscosity and suitable for strip extrusion, extruding and cutting into particles with the diameter of about 3 mm and the length of 6-8 mm, drying at 120 ℃ for 4 hours, and roasting at 900 ℃ for 4 hours to obtain a precursor II; and preparing 100mL of lanthanum nitrate solution, uniformly spraying the solution on the surface of the precursor II by adopting a spraying method, drying at 120 ℃ for 4 hours, and roasting at 800 ℃ for 3 hours to obtain a catalyst finished product.

[ example 4 ]

300g of iron oxide red, 88g of potassium carbonate, 47.2g of cerium oxalate, 16.4g of ammonium tungstate, 6.5g of magnesium oxide, 11.4g of calcium carbonate, 2.9g of rubidium nitrate, 2.4g of cesium nitrate, 10g of praseodymium nitrate, 9.8g of neodymium nitrate, 2.5g of zinc oxide, 2.5g of manganese dioxide, 1.8g of tin dioxide and 30g of polyethylene fiber balls were weighed respectively, and the catalyst preparation procedure was the same as in example 1, wherein 0.75g of magnesium oxide and 1.34g of calcium carbonate were added when the precursor I was formed.

[ example 5 ]

365g of iron oxide red, 51.4g of potassium carbonate, 47.2g of cerium oxalate, 3.8g of ammonium tungstate, 4g of magnesium oxide, 7.9g of calcium carbonate, 2.9g of rubidium nitrate, 3.4g of cesium nitrate, 10g of lanthanum nitrate, 10g of praseodymium nitrate, 9.8g of neodymium nitrate, 0.5g of zinc oxide, 0.5g of manganese dioxide, 0.35g of tin dioxide and 30g of graphite were weighed out, respectively, and the catalyst preparation procedure was the same as in example 1, wherein 1.5g and 2.7g of magnesium oxide and calcium carbonate were added, respectively, when the precursor I was formed.

[ example 6 ]

320g of iron oxide red, 58.7g of potassium carbonate, 107.3g of cerium oxalate, 21.8g of ammonium tungstate, 2g of magnesium oxide, 3.5g of calcium carbonate, 11.8g of rubidium nitrate, 10.4g of cesium nitrate, 20g of lanthanum nitrate, 10g of praseodymium nitrate, 9.8g of neodymium nitrate, 2g of zinc oxide, 2g of manganese dioxide, 1.4g of tin dioxide and 30g of carboxymethyl cellulose are weighed respectively, and the preparation steps of the catalyst are the same as in example 1, wherein 1.2g of magnesium oxide and 2.1g of calcium carbonate are added respectively when the precursor I is formed.

[ example 7 ]

330g of iron oxide red, 58.7g of potassium carbonate, 64.4g of cerium oxalate, 5.5g of ammonium tungstate, 2.5g of magnesium oxide, 4.5g of calcium carbonate, 19.7g of rubidium nitrate, 17.3g of cesium nitrate, 5g of lanthanum nitrate, 5g of praseodymium nitrate, 7.5g of zinc oxide, 7.5g of manganese dioxide, 5.4g of tin dioxide and 30g of polyethylene fiber balls are weighed respectively, and the preparation steps of the catalyst are the same as example 1, wherein 1g of magnesium oxide and 1.8g of calcium carbonate are added when the precursor I is formed.

[ comparative examples 1 to 5 ]

The catalyst preparation methods of comparative examples 1 to 5 were the same as in example 1. In the comparative example 1, no iron oxide purification step is performed, in the comparative example 2, the Mg and Ca components are added at one time in the process of forming the precursor II, in the comparative example 3, the K component is added at one time in the process of forming the precursor I, in the comparative example 4, the light rare earth metal elements except Ce are added into the catalyst body instead of being loaded on the surface of the catalyst in the process of preparing the precursor II, in the comparative example 5, the alkali metal elements rubidium and cesium are added into the catalyst body instead of being loaded on the surface of the potassium ferrite oxide in the process of preparing the precursor I, and the composition condition of the catalyst is shown in the table 1.

TABLE 1 catalyst compositions of comparative examples 1 to 5

[ COMPARATIVE EXAMPLE 6 ]

The catalyst composition was the same as in example 1, and the preparation method was dry-mixed. Roasting 350g of iron oxide red at 700 ℃ for 4 hours, respectively adding 58.7g of potassium carbonate, 61.5g of cerium oxalate, 11g of ammonium tungstate, 8g of magnesium oxide, 15.8g of calcium carbonate, 8.9g of rubidium nitrate, 5.9g of cesium nitrate, 9g of lanthanum nitrate, 2.5g of zinc oxide, 2.5g of manganese dioxide, 1.8g of tin dioxide and 30g of carboxymethyl cellulose, mixing dry powder for 2 hours, adding 130mL of deionized water, kneading for about 1 hour to obtain a dough-like substance suitable for extrusion, extruding strips, and cutting into particles with the diameter of about 3 millimeters and the length of 6-8 millimeters; aging at room temperature for 12h, drying at 120 ℃ for 4h, and roasting at 900 ℃ in a muffle furnace for 6h to obtain the catalyst finished product.

[ COMPARATIVE EXAMPLE 7 ]

Catalyst prepared by the method described in example 1 of patent CN 201410778920.6: respectively weighing 300g of iron oxide red, 73.5g of potassium carbonate, 5g of zinc oxide, 5g of manganese dioxide and 5g of lead dioxide, dry-mixing for 1 hour, roasting for 2 hours at 600 ℃, adding 83g of cerium oxalate, 28.9g of ammonium tetramolybdate, 25g of magnesium oxide, 35.6g of calcium carbonate and 30g of carboxymethyl cellulose into a roasted product, mixing dry powder for 2 hours, adding 130mL of deionized water, kneading for about 1 hour to obtain a dough-like substance suitable for strip extrusion, and extruding and cutting into particles with the diameter of about 3 millimeters and the length of 6-8 millimeters; aging at room temperature for 12h, drying at 120 ℃ for 4h, placing in a muffle furnace, roasting at 900 ℃ for 6h to obtain a catalyst precursor, and measuring the volume of the precursor by using a 500mL measuring cylinder; preparing a mixed solution which is composed of 7.9g of rubidium nitrate, 6.9g of cesium nitrate and 10g of lanthanum nitrate and has the same volume with the catalyst precursor, then loading the mixed salt solution on the catalyst precursor by adopting an isometric impregnation method, drying at 120 ℃ for 6 hours, and roasting at 750 ℃ for 4 hours to obtain a catalyst finished product.

The catalyst physical property detection items include bulk density and radial crushing resistance; the performance evaluation of the catalysts of the comparative examples and the examples is carried out on a 4L adiabatic negative pressure evaluation device, and the reaction process comprises the following steps: the inlet temperature of the first reaction is 623 ℃, the inlet temperature of the second reaction is 627 ℃, the water ratio (mass ratio of water vapor to ethylbenzene) is 1.05, and the space velocity of ethylbenzene liquid is 0.36h^-1The second reaction outlet pressure was 40KPa (absolute pressure). The physical property data of the catalyst are shown in Table 2, the evaluation results of the catalyst activity are shown in Table 3, and the evaluation results of the catalyst stability are shown in Table 4.

Table 2 shows the bulk density and radial crush resistance measurements for the catalysts prepared in the comparative examples and examples. As can be seen from Table 2, the bulk density and the radial crushing resistance of the catalyst are both significantly improved by the method of preparing the precursor I, II by adding Ca and Mg ions in two steps.

TABLE 2 bulk Density vs. radial force to crush data

Catalyst and process for preparing same	Bulk Density (g/mL)	Radial crushing resistance (N/mm)
			Example 1	1.42	30
Example 2	1.41	29
			Example 3	1.40	29
Example 4	1.39	29
			Example 5	1.40	28
Example 6	1.38	28
			Example 7	1.39	29
Comparative example 1	1.30	24
			Comparative example 2	1.32	25
Comparative example 3	1.35	26
			Comparative example 4	1.36	27
Comparative example 5	1.25	20
			Comparative example 6	1.26	21
Comparative example 7	1.41	28

TABLE 3 catalyst Low Water ratio catalytic dehydrogenation Performance comparison

TABLE 4 comparison of stability evaluation results for catalysts

The table 3 and table 4 respectively show the activity and stability investigation results of the catalysts prepared in the comparative example and the example, and it can be seen from the table that the activity of the catalyst is more than 65.0% under the working condition of low water ratio and the activity of the catalyst is high by improving the preparation process such as purifying the iron source, reducing the potassium content, and adding the K, Mg and Ca auxiliary agents into the catalyst step by step; after 1000h reaction, the ethylbenzene conversion rate is basically unchanged and still kept at about 65%, the catalyst deactivation rate is low, and the stability is good. The catalysts prepared in comparative examples 1-6 have poor activity, and after 1000h of reaction, the activity is obviously reduced, and the stability is poor. The catalyst prepared according to the method disclosed in patent CN201410778920.6 (comparative example 7) has good physical properties and high initial activity, but the catalyst has poor stability in long-period operation, and due to loss of potassium element, carbon deposition occurs in active phase potassium ferrite under the working condition of low water ratio, the catalyst has too high inactivation rate, obvious activity reduction and poor stability.

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The catalyst for preparing styrene by ethylbenzene dehydrogenation is characterized by comprising the following components in percentage by mass:

b) 1-4% of K oxide, with K₂Measuring O;

c) 6-12% of Ce oxide, CeO₂Counting;

d)0.6 to 4% of W oxide, in the presence of WO₃Counting;

e) 2-6% of oxides of Mg or/and Ca, calculated as MgO or/and CaO;

h)0.3 to 2.5% of Mn oxide with MnO₂Counting;

i) 0.3-2.5% of Zn oxide (calculated as ZnO);

j)0.3 to 2.5% of Sn oxide, SnO₂Counting; the preparation process of the catalyst is as follows: 1) purifying an iron source, namely roasting the iron oxide red for 1-10 hours at 500-1000 ℃ to remove impurities and water in the iron oxide red;

2) preparing a Mg and Ca ion doped potassium ferrite oxide precursor I, weighing all iron raw material iron oxide red according to the mass ratio of 5:1 of iron raw material to potassium raw material, sequentially adding 10-50% of potassium raw material and 10-60% of Mg and Ca raw material, carrying out dry mixing for 1-5 hours, roasting for 1-10 hours at 500-1000 ℃, and adding alkali metal oxide Rb₂O、Cs₂Modifying the surface of the potassium ferrite oxide with O in the form of nitrate solution by adopting a spraying method to form a precursor I;

3) preparing a precursor II, grinding or crushing the precursor I to 50-100 meshes, adding Ce, W, Mn, Zn and Sn cocatalyst raw materials and residual K, Mg and Ca raw materials according to the content ratio, dry-mixing for 1-5 hours, adding deionized water to prepare a paste which is viscous and suitable for extrusion, extruding and cutting into particles with the diameter of 3 mm and the length of 6-8 mm, and drying at 80-150 ℃ for 1-10 hours to form the precursor II;

2. The catalyst according to claim 1, wherein the content of the potassium ferrite composite oxide is 70 to 75%.

3. The catalyst according to claim 1, wherein the content of the potassium oxide is 1 to 3% and the content of the cerium oxide is 6 to 10%.

4. The catalyst according to claim 1, wherein the content of tungsten oxide is 1 to 4%.

5. The catalyst of claim 1, wherein the alkali metal oxide is Rb₂O and/or Cs₂The content of O is 2-3%.

6. The catalyst according to claim 1, wherein the content of the light rare earth metal oxide other than Ce is 1.5-4%.

7. The catalyst according to claim 1, characterized in that the light rare earth oxide added is La₂O₃The content is 2-3%.

8. The catalyst according to claim 1, wherein at least one pore-forming agent selected from graphite, polystyrene microspheres and carboxymethyl cellulose is added during the preparation of the catalyst, and the amount of the pore-forming agent is 1-10% of the weight of the catalyst.