JP2014140827A - Method for producing oxidative dehydrogenation catalyst and alkene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an oxidative dehydrogenation catalyst and an alkane with high activity and high yield.SOLUTION: There is provided a method for producing an oxidative dehydrogenation catalyst, the method comprising: (a) a step of dispersing a silicate in water; (b) a step of adding a chromium element; (c) a step of adding a surfactant to perform reaction at 50 to 150°C for 1 to 20 hours; and (d) a step of performing heat treatment at 200 to 700°C for 1 to 10 hours, wherein the step (c) is carried out after the step (a) or the step (b).

Description

  The present invention relates to a method for producing an oxidative dehydrogenation catalyst using silicate, elemental chromium and a surfactant, and a method for producing an alkene in the presence of alkane and oxygen.

  Alkenes are brought into contact with an oxidative dehydrogenation catalyst and dehydrogenated to produce the desired alkene. The alkene production method is well known, and various catalysts are used in this method.

For example, Non-Patent Document 1 discloses a method for producing isobutene by oxidative dehydrogenation of isobutane in an atmosphere containing oxygen gas using a catalyst in which chromium oxide is supported on an alumina support having a specific surface area of 100 to 300 m ² / g. It is disclosed. Patent Document 1 discloses a method for producing alkenes by dehydrogenating various alkanes using zeolite carrying chromium oxide. Furthermore, Non-Patent Document 2 regularly describes pores composed of spherical cavities prepared by the action of a substance that is a silica source such as tetraethylorthosilicate and a surfactant such as bromide of cetyltrimethylammonium. A method for producing isobutene by oxidative dehydrogenation of isobutane using a catalyst in which chromium oxide is supported on an ordered mesoporous material called SBA-16 arranged is disclosed. Non-Patent Document 3 discloses a method for producing propylene by oxidative dehydrogenation of propane using a composite oxide.

JP 2008-266286 A

Ind. Eng. Chem. Res. 2001, 40, 781-784 Applied Catalysis A: General 354 (2009) 72-81 Journal of Ceramic Society of Japan 115 (2007) 667-671

  However, the catalysts and alkene production methods described in the above-mentioned patent documents and non-patent documents have low activity and low yield. Therefore, there are many examples in which the reaction is performed at a high temperature of 500 ° C. or higher. In the study by the present inventors, it has been found that it is difficult to obtain a highly active catalyst by trying various catalyst systems so far.

  An object of the present invention is to provide a highly active and high yield oxidative dehydrogenation catalyst and a method for producing alkane.

  The present invention has been made as a result of intensive studies by the present inventors in order to achieve the above object.

The method for producing an oxidative dehydrogenation catalyst according to the present invention comprises:
(A) dispersing silicate in water;
(B) adding chromium element;
(C) adding a surfactant and reacting at a temperature of 50 to 150 ° C. for 1 to 20 hours;
(D) a step of heat treatment at a temperature of 200 to 700 ° C. for 1 to 10 hours;
Including
Step (c) is performed after step (a) or step (b).

  Further, in the present invention, an alkene is produced from an alkane by bringing a mixed gas containing an alkane having a molar ratio of oxygen to alkane of 0.1 to 1.9 and oxygen into contact with the oxidative dehydrogenation catalyst according to the present invention.

  According to the present invention, it is possible to provide a highly active and high yield oxidative dehydrogenation catalyst and a method for producing alkane.

[Production method of oxidative dehydrogenation catalyst]
The method for producing an oxidative dehydrogenation catalyst according to the present invention comprises:
(A) dispersing silicate in water;
(B) adding chromium element;
(C) adding a surfactant and reacting at a temperature of 50 to 150 ° C. for 1 to 20 hours;
(D) a step of heat treatment at a temperature of 200 to 700 ° C. for 1 to 10 hours;
Step (c) is performed after step (a) or step (b).

(Process (a))
In step (a), silicate is dispersed in water.

  The silicate used in the present invention is a base material that disperses and immobilizes the chromium element which is an active ingredient, and does not itself inhibit the target reaction. In general, silica or alumina is used. However, when silicate is used as a raw material as in the present invention, in addition to an increase in the reaction field due to a high specific surface area, within the skeleton lattice of the active ingredient by ion exchange. The yield of the target product is also expected to be improved by immobilization on the gel.

Examples of the silicate used in the present invention include sodium silicate, kanemite (NaHSi ₂ O ₅ .3H ₂ O), sodium disilicate crystals (α, β, γ, σ-Na ₂ Si ₂ O ₅ ), macatite ( _{Na 2 Si 4 O 9 · 5H} 2 O), Maia write _{(Na 2 Si 8 O 17 ·} xH 2 O), Maga Deer write _{(Na 2 Si 14 O 29 ·} xH 2 O), kenyaite (Na ₂ Si ₂₀ O ₄₁ XH ₂ O) can be used. Among these, as the silicate, sodium silicate or kanemite is preferable. These silicates may be used alone or in combination of two or more.

  Although the density | concentration of the silicate disperse | distributed in water is not specifically limited, For example, it can be 1.0 mass% concentration or more and 50.0 mass% concentration or less.

(Process (b))
In the step (b), chromium element is added.

  There is no restriction | limiting in particular as a raw material of the chromium element to add, For example, a chromium chloride, nitrate, acetate, sulfate, carbonate, hydrogencarbonate, an ammine complex etc. can be used. One kind of these chromium element materials may be used, or two or more kinds thereof may be used.

  The amount of chromium element contained in the oxidative dehydrogenation catalyst produced by the method according to the present invention is preferably 0.01 to 20% by mass as a mass ratio of chromium atoms to the mass of silicon atoms contained. More preferably, it is 1-15 mass%. The chromium content is a value measured by elemental analysis inductively coupled plasma (ICP-AES).

  Chromium element may be added to the silicate dispersion slurry obtained by the step (a) or may be added to the reactant obtained by the step (c) described later.

  The method of adding chromium element to the silicate dispersion slurry obtained in step (a) is not particularly limited, and for example, chromium element can be dissolved in the silicate dispersion slurry.

  The method of adding chromium element to the reactant obtained in step (c) is not particularly limited, and a normal impregnation support method, ion exchange method, or the like can be used. For example, as a method of loading a chromium element on a precursor in which a surfactant is allowed to act on a layered silicate, there is a method of impregnating the precursor with a solution containing the chromium element and drying and loading. In addition, as a method of adding the chromium element to the precursor using an ion exchange method, for example, the chromium element is added to a precursor containing a surfactant generated by heating a layered silicate in a surfactant solution. There is a method of firing after impregnating an aqueous solution containing the solution.

(Process (c))
In the step (c), a surfactant is added and reacted at a temperature of 50 to 150 ° C. for 1 to 20 hours. Step (c) is performed after step (a) or step (b). The method according to the present invention may be performed in the order of steps (a), (b), (c), and (d), for example, and in the order of steps (a), (c), (b), and (d). It may be done.

  As the surfactant used in the present invention, for example, alkyltrimethylammonium, dimethyldialkylammonium, alkylammonium, benzylammonium chloride, bromide, iodide or hydroxide can be used. Of these, alkyltrimethylammonium bromide is preferred as the surfactant. The alkyl group of alkyltrimethylammonium, dimethyldialkylammonium, alkylammonium chloride, bromide, iodide or hydroxide is preferably a linear or branched alkyl group having 8 to 18 carbon atoms. One of these surfactants may be used, or two or more thereof may be used.

When the step (c) is performed after the step (a), for example, a regular mesoporous material may be produced by using a layered silicate on a silicate and causing a surfactant to act. For example, S.M. Inagaki et al. , J .; Chem. Soc. , Chem. Commun. No. 8, 680-682 (1993). The regular mesoporous material has a structure in which periodically curved silicate sheets are vertically coupled by convex portions, and innumerable uniform pores exist in the sheet gap. The pore diameter is 1 to 10 nm, and the pore diameter is distributed in a narrow range around a certain diameter. For example, when alkyltrimethylammonium is used as the surfactant, the pore diameter can be changed depending on the length of the alkyl chain. Among them, it is preferable to produce FSM-16 as a regular mesoporous material using hexadecyltrimethylammonium (C ₁₆ H ₃₃ N (CH ₃ ) ₃ ).

  Examples of a method for synthesizing a regular mesoporous material by reacting a silicate with a surfactant include a method of dispersing the above-described layered silicate in a solvent in which the surfactant is dissolved. The solvent is preferably water, but may be a water-alcohol mixed solvent or other solvents. The concentration of the surfactant is preferably 0.05 to 1 mol / L. The dispersion amount of the layered silicate is preferably, for example, 5 to 200 g of kanemite with respect to 1000 ml of the 0.1 mol / L surfactant aqueous solution. The reaction temperature is 50 to 150 ° C, preferably 60 to 100 ° C. When the reaction temperature is within the above range, a regular mesoporous material having a pore size suitable for the reaction is preferable. It is preferable to stir the dispersion during heating. The pH of the dispersion solution is preferably 10 or more for the first 1 to 5 hours and 10 or less for the remaining time. Since Kanemite is alkaline, the pH of the dispersion becomes 10 or more even if nothing is done. If the pH does not reach 10 or higher, sodium hydroxide can be added to increase the pH to 10 or higher. Thereafter, an acid such as hydrochloric acid can be added to lower the pH of the solution to 10 or lower. It is preferable to lower the pH of the solution to 8.5. By this pH control, an ordered mesoporous material having particularly high crystallinity and heat resistance can be obtained. Thereafter, the solid product is recovered by filtration. The reaction time is 1 to 20 hours, preferably 10 to 19 hours. When the reaction time is within the above range, a regular mesoporous material having a pore size suitable for the reaction is preferable. In addition, reaction time shows the time from when a silicate and surfactant are mixed until it filters a solid product. A regular mesoporous material with high heat resistance can be obtained by repeatedly washing the solid product with deionized water or the like.

  In addition, when performing a process (b) after a process (a) and performing a subsequent process (c), it can carry out by the method similar to the above.

(Process (d))
In the step (d), heat treatment is performed at a temperature of 200 to 700 ° C. for 1 to 10 hours. In this step, the catalyst precursor obtained in steps (a) to (c) is heat-treated, thereby removing the surfactant incorporated in the crystal and producing a porous catalyst.

  The heat treatment temperature is 200 to 700 ° C, preferably 500 to 600 ° C. When the heat treatment temperature is within the above range, the surfactant can be sufficiently removed and the regular mesoporous material itself can be stably maintained. The heat treatment time is 1 to 10 hours, preferably 5 to 9 hours. When the heat treatment time is within the above range, the surfactant can be sufficiently removed. The heat treatment can be performed in an atmosphere of air, oxygen, nitrogen, or the like.

[Method for producing alkenes from alkanes]
In the present invention, an alkene is produced from an alkane by bringing a mixed gas containing an alkane having a molar ratio of oxygen to alkane of 0.1 to 1.9 and oxygen into contact with the oxidative dehydrogenation catalyst according to the present invention.

  The alkane raw material used for the oxidative dehydrogenation reaction is not particularly limited, but an alkane having 2 to 5 carbon atoms is preferable. When the number of carbon atoms is 5 or less, the production of low carbon number alkenes by the decomposition reaction can be sufficiently suppressed. Examples of the alkane having 2 to 5 carbon atoms include ethane, propane, butane, isobutane, and pentane.

  In the present invention, the alkane is subjected to the oxidative dehydrogenation reaction described above to produce the corresponding alkene. The oxidative dehydrogenation reaction is performed by bringing a mixed gas containing alkane and oxygen into contact with an oxidative dehydrogenation catalyst. The molar ratio of oxygen to alkane contained in the mixed gas is 0.1 to 1.9, preferably 0.25 to 1.6. When the molar ratio is less than 0.1, the oxygen concentration is low and the oxidation reaction is not sufficiently performed, so that the reactivity is lowered. On the other hand, when the molar ratio is larger than 1.9, the oxygen concentration is too high, so the selectivity is lowered and an ideal reaction cannot be performed.

  The mixed gas may contain helium, nitrogen, water vapor, etc. in addition to alkane and oxygen. The concentration of alkane in the mixed gas is preferably 1 to 30% by volume, more preferably 1 to 20% by volume. When the alkane concentration is 1% by volume or more, it is possible to suppress a decrease in alkene selectivity due to an improved alkane conversion rate. Moreover, when the alkane concentration is 30% by volume or less, it is possible to suppress a decrease in alkane conversion rate.

  The temperature of the oxidative dehydrogenation reaction is preferably 300 to 1000 ° C, more preferably 400 to 700 ° C, and further preferably 400 to 500 ° C. Sufficient catalytic activity can be obtained when the temperature of the oxidative dehydrogenation reaction is 300 ° C. or higher. In addition, when the temperature of the oxidative dehydrogenation reaction is 1000 ° C. or lower, it is possible to suppress a decrease in the selectivity of the alkene and a decrease in the catalytic activity due to the alkane thermal decomposition reaction.

  The reaction pressure can be appropriately selected depending on the type of alkane used in the reaction, and is usually 1 MPa or less, and atmospheric pressure is preferred. The reaction can be carried out in a fixed bed flow reaction system in which a mixed gas containing raw material alkane, oxygen and the like is circulated through a reactor filled with a catalyst.

  W / F is preferably 0.001 to 1000 g · min / ml, and more preferably 0.01 to 100 g · min / ml. W is the mass (g) of the catalyst charged in the reaction tube, and F is the flow rate (ml / min) of the mixed gas containing alkane and oxygen that flows to the layer filled with the catalyst. That is, W / F is the mass of the catalyst charged with respect to the flow rate of the mixed gas flowing in the reaction tube, and is calculated by the following equation.

    W / F = amount of catalyst to be filled (g) / flow rate of mixed gas flowing in reaction tube (ml / min)

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples.

  The chromium content was measured using elemental analysis inductively coupled plasma (ICP-AES) (product name: SPS 1500 VR, manufactured by Seiko Instruments Inc.).

In the alkene production method, the raw material mixed gas and the product were analyzed using gas chromatography. From the results of gas chromatography, the conversion rate of alkane, the selectivity of alkene, and the yield of alkene were determined by the following formulas.
Alkane conversion (%) = (B / A) × 100
Alkene selectivity (%) = (C / B) × 100
Alkene yield (%) = (C / A) × 100
In the formula, A is the number of moles of supplied alkane, B is the number of moles of reacted alkane, and C is the number of moles of alkene produced.

[Example 1]
Sodium silicate 5.0 g was calcined at 700 ° C. for 6 hours. The calcined sodium silicate was added to 50 mL of distilled water and stirred at room temperature for 3 hours to be dispersed. By filtering this, a paste of kanemite which is a layered silicate was obtained. To the obtained kanemite paste, 100 ml of a 0.1 mol / L hexadecyltrimethylammonium bromide aqueous solution was added and stirred at 70 ° C. for 3 hours. Then, using 2 mol / L hydrochloric acid aqueous solution, it adjusted so that pH might be set to 8.5, and continued stirring at 70 degreeC for 18 hours. Then, it filtered, wash | cleaned several times with distilled water, it was made to dry and the regular mesoporous material FSM-16 precursor was obtained. 50 ml of distilled water was added to the obtained regular mesoporous material FSM-16 precursor, and 5.3 ml of 0.5 mol / L chromium nitrate aqueous solution was added. The mixture was vigorously stirred and mixed for 1 hour and allowed to stand at 80 ° C. for 20 hours. Then, it filtered, wash | cleaned several times with distilled water, and it was made to dry and solid was obtained. This solid was calcined at 550 ° C. for 8 hours in an air atmosphere to obtain an oxidative dehydrogenation catalyst containing an ordered mesoporous material and chromium element. As a result of elemental analysis, the chromium content of the catalyst obtained at this time was 0.6% by mass with respect to the mass of silicon atoms contained.

  The obtained oxidative dehydrogenation catalyst was packed in a reaction tube having a diameter of 9 mm and a length of 35 mm, made of quartz, installed in a fixed bed flow type reactor. The reaction tube was held at 450 ° C. by an electric furnace. Thereafter, a mixed gas obtained by diluting isobutane partial pressure 14.4 kPa, oxygen gas partial pressure 12.3 kPa, and the remainder diluted with helium gas under atmospheric pressure was circulated in the reaction tube at a flow rate of 30 ml / min. Thereby, the said oxidative dehydrogenation catalyst and mixed gas were made to contact and the isobutylene (alkene) was manufactured from isobutane (alkane). At this time, the molar ratio of oxygen to isobutane (mixed gas ratio) was 0.85, and the concentration of isobutane in the mixed gas was 14.2% by volume. The amount of catalyst packed in the reaction tube was set so that W / F was 0.016 g · min / ml.

  The gas at the outlet of the reaction tube was measured by gas chromatography to determine isobutane conversion, isobutene selectivity, and isobutene yield. The results are shown in Table 1. Table 1 shows the reaction results 45 minutes and 360 minutes after the start of the reaction.

[Example 2]
In the process of producing an oxidative dehydrogenation catalyst containing a regular mesoporous material and chromium element, except vigorously stirred and mixed for 1 hour, left at 80 ° C. for 20 hours, filtered and then dried without washing Produced an oxidative dehydrogenation catalyst by the same method as in Example 1 to produce isobutylene. As a result of elemental analysis, the chromium content of the catalyst obtained at this time was 4.2% by mass relative to the mass of silicon atoms contained. The results are shown in Table 1.

[Example 3]
In the production of isobutylene, a mixed gas obtained by diluting isobutane partial pressure 14.4 kPa, oxygen gas partial pressure 20.5 kPa, and the remainder diluted with helium gas under atmospheric pressure was circulated in the reaction tube at a flow rate of 30 ml / min. The same method as in Example 2 was performed. At this time, the molar ratio of oxygen to isobutane (mixed gas ratio) was 1.42. The results are shown in Table 1.

[Example 4]
In the production of isobutylene, a mixed gas obtained by diluting isobutane partial pressure 14.4 kPa, oxygen gas partial pressure 4.1 kPa, and the remainder diluted with helium gas under atmospheric pressure was circulated in the reaction tube at a flow rate of 30 ml / min. The same method as in Example 1 was performed. At this time, the molar ratio of oxygen to isobutane (mixed gas ratio) was 0.28. The results are shown in Table 1.

[Comparative Example 1]
It implemented by the method similar to Example 3 except having used ammonium vanadate instead of chromium nitrate. The results are shown in Table 1.

[Comparative Example 2]
Magnesium nitrate hexahydrate 4.72 g was dissolved in 10 ml of distilled water. Further, an aqueous nitric acid solution was added to adjust the pH to 4.0 to prepare Solution A. Thereafter, 3.54 g of hexaammonium molybdo tetrahydrate was pulverized in a mortar, dissolved in 10 ml of distilled water, and adjusted to pH 8 by adding aqueous ammonia to prepare solution B. Then, the solution B was added while stirring the solution A, and the mixture was stirred until the ammonia odor disappeared. Next, the pressure was reduced with an evaporator, the water was evaporated, and the resulting precipitate was dried at 60 ° C. overnight. The obtained dried product was calcined at 300 ° C. for 3 hours. The obtained solid was pulverized in a mortar and further calcined at 400 ° C. for 5 hours to obtain an oxidative dehydrogenation catalyst composed of a composite oxide called Mg _0.92 MoO _x . Then, isobutylene was produced by the same method as in Example 4. The results are shown in Table 1.

[Example 5]
Sodium silicate 5.0 g was calcined at 700 ° C. for 6 hours. The calcined sodium silicate was added to 100 mL of distilled water, and 4.0 g of chromium nitrate nonahydrate was further added, followed by stirring at room temperature for 3 hours to obtain a precursor containing chromium element. To the obtained precursor was added 100 ml of a 0.1 mol / L hexadecyltrimethylammonium bromide aqueous solution, and the mixture was stirred and held at 70 ° C. for 3 hours. Then, using 2 mol / L hydrochloric acid aqueous solution, it adjusted so that pH might be set to 8.5, and continued stirring at 70 degreeC for 18 hours. Thereafter, filtration was performed, washing was performed several times with distilled water, and drying was performed to obtain a solid. The solid was calcined at 550 ° C. for 8 hours in an air atmosphere to obtain an oxidative dehydrogenation catalyst. Then, isobutylene was produced by the same method as in Example 1. The results are shown in Table 1.

  Thus, an oxidative dehydrogenation catalyst is produced using the oxidative dehydrogenation catalyst production method according to the present invention using silicate, chromium element and surfactant, and the molar ratio of oxygen to alkane is produced in the oxidative dehydrogenation catalyst. Higher activity and yield can be achieved by contacting a mixed gas having an A of 0.1 to 1.9 to produce an alkene from an alkane.

Claims (2)

(A) dispersing silicate in water;
(B) adding chromium element;
(C) adding a surfactant and reacting at a temperature of 50 to 150 ° C. for 1 to 20 hours;
(D) a step of heat treatment at a temperature of 200 to 700 ° C. for 1 to 10 hours;
Including
Step (c) is a method for producing an oxidative dehydrogenation catalyst performed after step (a) or step (b).   A method for producing an alkene from an alkane by bringing a mixed gas containing an alkane and oxygen having a molar ratio of oxygen to alkane of 0.1 to 1.9 into contact with the oxidative dehydrogenation catalyst according to claim 1.