Patent Description:
The industrial production method of alkenyl aromatic hydrocarbons is mainly dehydrogenation of alkyl aromatic hydrocarbons. For example, the industrial production method of styrene is mainly catalytic dehydrogenation of ethylbenzene, and its production capacity accounts for about <NUM>% of the total production capacity of styrene. One of the keys of the method is catalyst for dehydrogenation of ethylbenzene to styrene. At present, basic components of catalyst for dehydrogenation of ethylbenzene to styrene in industry include a main catalyst, a cocatalyst, a pore-forming agent, and a binder, etc. Early catalysts are Fe-K-Cr system catalysts, such as the published <CIT> (Dehydrogenation catalyst) and <CIT> (A dehydrogenation catalyst having improved moisture stability and a process for making the same). Although such catalysts have good activity and stability, they have been gradually eliminated because the catalysts contain oxides of Cr, which would cause certain pollution to the environment. Later, the catalysts evolved into Fe-K-Ce-Mo system catalysts, in which Cr is replaced with Ce and Mo, which can better improve catalyst activity and stability while overcoming the disadvantages of Cr's high toxicity and pollution to the environment.

<CIT> describes a catalyst for preparing styrene by dehydrogenation of ethylbenzene and preparation method thereof.

In catalysts for production of alkenyl aromatic hydrocarbons by means of dehydrogenation of alkyl aromatic hydrocarbons, iron oxide is a main catalyst, and potassium is a main cocatalyst. The addition of potassium can increase catalyst activity by more than one order of magnitude. For Fe-K-Ce-Mo catalysts, after high temperature calcination, the catalysts generally contain an α-Fe<NUM>O<NUM> phase and phases of a compound containing iron and potassium. A large number of research results show that a compound of iron and potassium is a main active phase or a precursor of active phase of catalysts for dehydrogenation of alkyl aromatic hydrocarbons. Therefore, the formation and structure of a compound of iron and potassium are of great significance to catalyst activity.

How to easily obtain required catalyst phases and structures so as to further improve catalyst activity has always been a topic of interest to researchers.

A method for preparing a catalyst for dehydrogenation of an alkyl aromatic hydrocarbon according to the invention, as well as a method for dehydrogenation of an alkyl aromatic hydrocarbon are defined in the claims.

A first technical problem to be solved by the present disclosure is the technical problem of insufficient catalyst activity in the prior art. The present disclosure provides a new catalyst for the dehydrogenation of an alkyl aromatic hydrocarbon. The catalyst includes a compound containing iron and potassium. The compound containing iron and potassium has a special X-ray diffraction (XRD) pattern. The catalyst has the characteristic of high activity.

A second technical problem to be solved by the present disclosure is to provide a preparing method corresponding to the catalyst that solves the first technical problem.

A third technical problem to be solved by the present disclosure is to apply the catalyst, which solves the first technical problem above, to a method for dehydrogenation of an alkyl aromatic hydrocarbon.

In order to solve the first technical problem above, the present disclosure provides a catalyst for dehydrogenation of an alkyl aromatic hydrocarbon. The catalyst includes a compound containing iron and potassium. The compound containing iron and potassium consists of a K<NUM>Fe<NUM>O<NUM> phase and a K<NUM>Fe<NUM>O<NUM> phase.

According to a preferred implementation of the present disclosure, the compound containing iron and potassium has an X-ray diffraction (XRD) pattern as shown in the following table:.

According to a preferred implementation of the present disclosure, the X-ray diffraction pattern further comprises X-ray diffraction peaks as shown in the following table:.

According to a preferred implementation of the present disclosure, a mass ratio of the K<NUM>Fe<NUM>O<NUM> phase to the K<NUM>Fe<NUM>O<NUM> phase in the compound containing iron and potassium is in a range from <NUM> to <NUM>, preferably in a range from <NUM> to <NUM>.

According to a preferred embodiment of the present disclosure, the catalyst does not contain a free α-Fe<NUM>O<NUM> phase.

According to a preferred embodiment of the present disclosure, the catalyst includes the following components in weight percentage: (a) <NUM>% to <NUM>% of Fe<NUM>O<NUM>; (b) <NUM>% to <NUM>% of K<NUM>O; (c) <NUM>% to <NUM>% of CeO<NUM>; (d) <NUM>% to <NUM>% of MoO<NUM>; and (e) <NUM>% to <NUM>% of CaO.

In order to solve the second technical problem above, the present disclosure provides a method for preparing a catalyst for dehydrogenation of an alkyl aromatic hydrocarbon, the method including the following steps of:.

According to a preferred implementation of the present disclosure, in the step <NUM>), adding the iron source in the form of at least one of red iron oxide and yellow iron oxide; adding the first part of the potassium source in the form of at least one of a potassium salt and potassium hydroxide; adding the cerium source in the form of a cerium salt; adding the molybdenum source in the form of at least one of a molybdenum salt and an oxide of molybdenum; and adding the calcium source in the form of at least one of a calcium salt, calcium oxide, and calcium hydroxide.

According to a preferred implementation of the present disclosure, in the step <NUM>), adding the second part of the potassium source in the form of at least one of potassium hydroxide and potassium carbonate.

According to a preferred implementation of the present disclosure, an amount of addition of water in step <NUM>) is not particularly limited. Those skilled in the art can reasonably control the humidity according to the requirement for extrusion. For example, the amount of addition of water accounts for, but not limited to, <NUM>% to <NUM>% of the total weight of the catalyst raw materials. Preferably, the water is deionized water.

According to a preferred implementation of the present disclosure, the pore-forming agent is a combustible material known to those in the art. For example, the pore-forming agent can be selected from sodium carboxymethyl cellulose, polymethylstyrene microspheres, methyl cellulose, hydroxyethyl cellulose, sesbania powder, graphite, etc. An amount of addition of the pore-forming agent accounts for <NUM>% to <NUM>% of the total weight of the catalyst.

According to a preferred implementation of the present disclosure, the method further includes following step of:
<NUM>) performing processes of wet-kneading, extruding, forming, drying, and calcinating on the as-made catalyst obtained in the step <NUM>).

According to a preferred implementation of the present disclosure, in the step <NUM>), a drying temperature is in a range from <NUM> to <NUM>, and a drying time is in a range from <NUM> to <NUM> hours.

According to a preferred embodiment of the present disclosure, in the step <NUM>), calcinating is performed at <NUM> to <NUM> for <NUM> to <NUM> hours, and then at <NUM> to <NUM> for <NUM> to <NUM> hours.

According to a preferred implementation of the present disclosure, the as-prepared catalyst includes a compound containing iron and potassium, the compound containing iron and potassium consisting of a K<NUM>Fe<NUM>O<NUM> phase and a K<NUM>Fe<NUM>O<NUM> phase.

According to a preferred implementation of the present disclosure, the X-ray diffraction pattern further includes X-ray diffraction peaks as shown in the following table:.

Catalyst particles prepared in the present disclosure can be of various shapes, such as a solid cylindrical shape, a hollow cylindrical shape, a trilobal shape, a diamond shape, a quincuncial shape, and a honeycomb shape. Also, there are no specific limitations on the diameter and particle length of the catalyst particles. It is preferred that the catalyst is in the form of solid cylindrical particles with a diameter of <NUM> to <NUM> and a length of <NUM> to <NUM>.

In order to solve the third technical problem above, the present disclosure provides an application of the above-described catalyst or the catalyst prepared according to the above-described method in preparation of alkenyl aromatic hydrocarbons by means of dehydrogenation of alkyl aromatic hydrocarbons.

The present disclosure further provides a method for dehydrogenation of an alkyl aromatic hydrocarbon, the method including a step of contacting a feed stream containing an alkyl aromatic hydrocarbon with the above-described catalyst or the catalyst prepared according to the above-described method to obtain a reactant stream containing an alkenyl aromatic hydrocarbon.

According to a preferred implementation of the present disclosure, those skilled in the art can use the application according to the prior art process. The alkyl aromatic hydrocarbon includes at least one of ethylbenzene, methyl ethylbenzene, diethylbenzene or polyalkylbenzene. Preferably, the alkyl aromatic hydrocarbon is diethylbenzene or ethylbenzene. For example, ethylbenzene is used as a raw material, and in the presence of the catalyst, the raw material contacts and reacts with the catalyst so as to produce styrene.

The prepared catalyst is evaluated for activity in an isothermal fixed bed. For the activity evaluation of the catalyst for dehydrogenation of ethylbenzene to styrene, the process is briefly described as follows.

Reaction raw materials are respectively fed into a preheating mixer via a metering pump, and are preheated and mixed into a gaseous state and then enter a reactor. The reactor is heated by an electric heating wire so as to reach a predetermined temperature. The reactant flowing out of the reactor is condensed by water, and then the composition of the reactant is analyzed by means of a gas chromatograph.

The conversion of ethylbenzene and the selectivity of styrene are calculated according to the following formulas: <MAT> <MAT>.

In the present disclosure, an XRD measurement of the catalyst is carried out using D8 advance X-ray powder diffractometer from Bruker, with tube voltage of <NUM> kV, tube current of <NUM> mA, Cu target, scanning range of <NUM>° to <NUM>°, scanning speed of <NUM> (°)/min, and solid detector. In the context of this description, in the XRD data of the catalyst, I represents the peak area of a corresponding diffraction peak; I<NUM> represents the peak area of the strongest diffraction peak; and W, M, S, and VS represent the intensity of a diffraction peak, wherein W means weak, M means medium, S means strong, and VS means very strong, which is well known to those skilled in the art. Generally, W is less than <NUM>; M is in a range from <NUM> to <NUM>; S is in a range from <NUM> to <NUM>; and VS is greater than <NUM>.

In the technical solution of the present disclosure, adding potassium in an iron-potassium-cerium-molybdenum-calcium system in different steps, and in the as-prepared catalyst, a compound containing iron and potassium contains both a K<NUM>Fe<NUM>O<NUM> phase and a K<NUM>Fe<NUM>O<NUM> phase. Thus, the catalyst has the characteristic of high activity. When the catalyst of the present disclosure is used in a reaction for dehydrogenation of ethylbenzene to styrene under the conditions of reaction pressure of -<NUM> kPa, liquid space velocity of <NUM>-<NUM>, temperature of <NUM>, water vapor/ethylbenzene (weight ratio) of <NUM>, a conversion can reach <NUM>% and a selectivity can reach <NUM>%, and thus good technical effects are achieved.

Fig. <NUM> is an XRD spectrum of a catalyst prepared in Example <NUM> of the present disclosure.

The present disclosure will be further described with reference to embodiments.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

An XRD measurement was performed on the catalyst. The XRD measurement was carried out using D8 advance X-ray powder diffractometer from Bruker, with tube voltage of <NUM> kV, tube current of <NUM> mA, Cu target, scanning range of <NUM>° to <NUM>°, scanning speed of <NUM> (°)/min, and solid detector. The XRD spectrum of the catalyst is shown in Fig. <NUM>. The results of the crystal phase composition of the sample are listed in Table <NUM>.

<NUM> of the catalyst was put into a stainless steel tube reactor with an inner diameter of <NUM>" under the conditions of reaction pressure of -<NUM> kPa, liquid space velocity of <NUM>-<NUM>, temperature of <NUM>, water vapor/ethylbenzene (weight ratio) of <NUM>. The test results are listed in Table <NUM>.

Fig. <NUM> is the XRD spectrum of the catalyst prepared in Example <NUM>. As can be seen from Fig. <NUM>, characteristic diffraction peak of α-Fe<NUM>O<NUM> phase at 2θ of <NUM>°, <NUM>°, <NUM>°, <NUM>°, and <NUM>° do not appear, indicating that the catalyst does not contain an α-Fe<NUM>O<NUM> phase. In Fig. <NUM>, diffraction peaks appearing at 2θ of <NUM>°, <NUM>°, <NUM>°, and <NUM>° are CeO<NUM> characteristic diffraction peaks, and the remaining diffraction peaks are K<NUM>Fe<NUM>O<NUM> and K<NUM>Fe<NUM>O<NUM> characteristic diffraction peaks. This indicates that, iron and potassium in the catalyst completely formed a compound containing iron and potassium, and the compound containing iron and potassium consists of a K<NUM>Fe<NUM>O<NUM> phase and a K<NUM>Fe<NUM>O<NUM> phase.

An XRD measurement was performed on the catalyst. The XRD measurement was carried out using D8 advance X-ray powder diffractometer from Bruker, with tube voltage of <NUM> kV, tube current of <NUM> mA, Cu target, scanning range of <NUM>° to <NUM>°, scanning speed of <NUM> (°)/min, and solid detector. The results of the crystal phase composition of the sample are listed in Table <NUM>.

Except that K is all added by dry mixing, the method for preparing catalyst and catalyst evaluation conditions are the same as those in Example <NUM>, and are specifically as follows.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours, added into deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Except that K is all added by being dissolved with water, the method for preparing catalyst and catalyst evaluation conditions are the same as those in Example <NUM>, and are specifically as follows.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Except for the difference in the amount of dry-mixed K in the total amount of K, the method for preparing catalyst and catalyst evaluation conditions are the same as those in Example <NUM>, and are specifically as follows.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium hydroxide equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium hydroxide equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium carbonate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, calcium hydroxide equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of sesbania powder were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium carbonate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, <NUM> parts of TiO<NUM>, <NUM> parts of sodium carboxymethyl cellulose, and <NUM> parts of sesbania powder were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of graphite were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium oxalate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, <NUM> parts of TiO<NUM>, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

Red iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, yellow iron oxide equivalent to <NUM> parts of Fe<NUM>O<NUM>, potassium carbonate equivalent to <NUM> parts of K<NUM>O, cerium carbonate equivalent to <NUM> parts of CeO<NUM>, ammonium molybdate equivalent to <NUM> parts of MoO<NUM>, calcium carbonate equivalent to <NUM> parts of CaO, and <NUM> parts of sodium carboxymethyl cellulose were stirred in a kneader for <NUM> hours so as to obtain a catalyst precursor I. Potassium carbonate equivalent to <NUM> parts of K<NUM>O was dissolved with deionized water accounting for <NUM>% of the total weight of the catalyst raw materials, then added to the catalyst precursor I, wet-kneaded for <NUM> hours, taken out, and extruded into particles with a diameter of <NUM> and a length of <NUM>. The particles thus obtained were put into an oven, baked at <NUM> for <NUM> hours, and <NUM> for <NUM> hours, and then calcined at <NUM> for <NUM> hours, and at <NUM> for <NUM> hours to obtain an as-prepared catalyst. The components of the catalyst are listed in Table <NUM>.

In Examples <NUM> to <NUM>, the amounts of respective raw materials are the same, but the only difference lies in the addition amount of the first part of the potassium source. As can be seen from the results of Examples <NUM> to <NUM>, different addition amounts of the first part of the potassium source would change the crystal phase composition of the compound containing iron and potassium in the catalyst. In Comparative Examples <NUM> and <NUM>, the amounts of respective raw materials are the same as those in Examples <NUM>-<NUM>, except that the potassium source is not added in different steps. The catalysts prepared in Comparative Examples <NUM> and <NUM> contain a free α-Fe<NUM>O<NUM> phase and does not contain a K<NUM>Fe<NUM>O<NUM> phase, and when such catalysts are used in a reaction for dehydrogenation of an alkyl aromatic hydrocarbon, the conversion of reactant is low. In Comparative Examples <NUM> to <NUM>, the amounts of respective raw materials are the same as those in Examples <NUM>-<NUM>, but the only difference lies in that the amount of the first part of the potassium source is not within the scope of the present disclosure. In addition to a K<NUM>Fe<NUM>O<NUM> phase and a K<NUM>Fe<NUM>O<NUM>, the catalysts prepared in Comparative Examples <NUM> to <NUM> further contain a free α-Fe<NUM>O<NUM> phase or other phases of the compound containing iron and potassium, and when such catalysts are used in a reaction for dehydrogenation of an alkyl aromatic hydrocarbon, the conversion of reactant is low. As can be seen from the comparison between Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>, according to the method of the present disclosure, a catalyst containing special phases of a compound containing iron and potassium can be obtained, and when such a catalyst is used in a reaction for dehydrogenation of an alkyl aromatic hydrocarbon, the conversion of reactant is relatively high.

A catalyst was prepared according to the method of Example <NUM>. The components and crystal phase composition of the catalyst were the same as those in Example <NUM>.

The obtained catalyst was crushed and sieved, so as to separate catalyst with a particle size of <NUM> to <NUM> for use. <NUM> milliliters of catalyst with a particle size of <NUM> to <NUM> was put into an isothermal tubular reactor, and the reactor was continuously supplied with <NUM>/h ethylbenzene and <NUM>/h deionized water at a reaction temperature of <NUM> and an initial pressure of <NUM> atm. The performance of the catalyst was measured under the condition of a water vapor/ethylbenzene ratio of <NUM>/kg or <NUM> mol/mol. The measured conversion of ethylbenzene was <NUM>% and the selectivity of styrene was <NUM>%.

Claim 1:
A method for preparing a catalyst for dehydrogenation of an alkyl aromatic hydrocarbon, the method comprising following steps of:
<NUM>) dry-mixing a first part of a potassium source with an iron source, a cerium source, a molybdenum source, a calcium source, and a pore-forming agent so as to obtain a catalyst precursor I;
<NUM>) dissolving a second part of the potassium source with water, and adding the catalyst precursor I to obtain an as-made catalyst,
the catalyst comprising the following components in weight percentage: (a) <NUM>% to <NUM>% of Fe<NUM>O<NUM>; (b) <NUM>% to <NUM>% of K<NUM>O; (c) <NUM>% to <NUM>% of CeO<NUM>; (d) <NUM>% to <NUM>% of MoO<NUM>; and (e) <NUM>% to <NUM>% of CaO; and the catalyst does not contain a free α-Fe<NUM>O<NUM> phase,
wherein by amount of contained K<NUM>O, a sum of a weight of the first part of the potassium source and a weight of the second part of the potassium source is a total weight of a required amount of potassium source, and the weight of the first part of the potassium source accounts for <NUM>% to <NUM>% of the total weight of the required amount of potassium source.