JP5283666B2 - Lower hydrocarbon aromatic compound catalyst, aromatic compound using lower hydrocarbon as raw material, and method for producing hydrogen - Google Patents

Description

  The present invention efficiently converts aromatic hydrocarbons mainly composed of benzene and naphthalene and high-purity hydrogen gas, which are raw materials for chemical products such as chemical industry, chemicals, and plastics from lower hydrocarbons such as natural gas. The present invention relates to a catalyst that can be produced and a method for producing the same.

Conventionally, aromatic compounds such as benzene, toluene and xylene are mainly produced from naphtha. As a method for producing naphthalenes, non-catalytic methods such as solvent extraction methods such as coal and gas pyrolysis methods such as natural gas and acetylene are employed. However, in these conventional methods, only a few percent of benzene and naphthalene can be obtained with respect to raw materials such as coal and acetylene, and there are many by-product aromatic compounds, hydrocarbons, tar, and insoluble carbon residues, which is problematic. Has a point. In addition, solvent extraction methods such as coal have a drawback that requires a large amount of organic solvent.
Also, in the production method of methane and acetylene by the thermal decomposition method, the production of naphthalenes requires a reaction temperature of 1000 ° C. or more to produce naphthalenes with a conversion efficiency of several percent or more. It was less than several percent of acetylene, and there was a problem in practical use.

  In addition, as a method for producing naphthalenes using a catalyst, a method for producing naphthalenes by subjecting alkylbenzenes such as orthoxylene to a dehydrogenative condensation reaction using a platinum-supported catalyst at a high temperature is also known. However, the conversion efficiency of naphthalenes is low, and the alkylbenzenes used as a raw material are expensive, causing problems in practical use.

  Furthermore, the method for producing the hydrogen gas co-produced in the present invention includes an aquatic gas (water gas shift) reaction using carbon monoxide generated by iron oxide waste gas or partial oxidation of coal, and a steam reforming reaction of natural gas. There are industrial processes carried out under high temperature and high pressure reaction conditions. In addition, there is a hydrogen production method by thermal cracking of crude oil, etc., but the production gas contains sulfur and nitrogen oxides that are catalyst poisons, and carbon monoxide that is a by-product in the produced hydrogen. Therefore, in the case of hydrogen gas produced by these conventional methods, there has been an industrial problem that requires a large load and equipment for removal and purification of the catalyst poison. In addition, these conventional hydrogen production methods have a serious problem from the viewpoint of the global environment because a large amount of carbon dioxide gas is by-produced and discharged as hydrogen is produced.

  On the other hand, as a method for producing lower hydrocarbons, in particular methane, aromatic compounds such as benzene and hydrogen, a method is known in which methane is reacted in the presence of a catalyst and in the absence of oxygen or an oxidizing agent. As the catalyst in this case, molybdenum supported on ZSM-5 is effective [Non-patent Document 1 and documents cited in the document].

"JOURNAL OF CATALYSIS", pages 165, 150-161 (1997)

  However, even when these catalysts are used, in addition to problems such as a large amount of carbon deposition and a low conversion rate of methane, the catalyst life is very short and favorable catalyst performance for a practical process cannot be obtained. Has the problem.

In view of the above prior art, the present inventors have proposed a catalyst in which a catalyst material such as Mo is supported on a porous metallosilicate (Japanese Patent Laid-Open Nos. 10-272366 and 11-60514). ). In these publications, in an experiment using a catalyst in which a catalyst material is supported on a porous metallosilicate having a pore diameter of 7 mm as a support, lower hydrocarbons are efficiently converted into aromatic compounds, and accompanied by high purity. It has been confirmed that the hydrogen can be obtained.
However, in order to further increase the production efficiency of aromatic compounds and hydrogen, it is desired to develop a catalyst that is superior in reaction efficiency.

  In view of the actual situation and problems of the prior art, the present invention uses aromatic compounds such as benzene and naphthalene and hydrogen gas, which are useful chemical raw materials using lower hydrocarbons mainly composed of methane such as natural gas. Direct reforming catalyst for lower hydrocarbons such as methane, which can be produced at the same time with high conversion and high selectivity catalyst performance, and exhibits stable catalytic performance for a long time, and aromatic compounds and hydrogen using the same It is an object of the present invention to provide a manufacturing method for the above.

As a result of intensive studies to achieve the above object, the present inventors have completed the present invention.
That is, the first invention of the lower hydrocarbon aromatic compound conversion catalyst of the present invention is a catalyst for reacting a lower hydrocarbon containing methane in the presence of carbon monoxide and / or carbon dioxide, comprising rhenium. Alternatively, the catalyst material includes one or more selected from the group consisting of the compounds and one or more selected from the group consisting of zinc, Ga, iron, or a compound thereof , and carries the catalyst material. substantially closed pores 4.5~6.5Å diameter as carriers, surface area comprising a porous metallosilicate is 200~1000m ² / g.

In addition, the method for producing an aromatic compound and hydrogen using the lower hydrocarbon of the second invention as a raw material includes methane or the like in the presence of carbon monoxide and / or carbon dioxide in the presence of the catalyst of the first invention. lower hydrocarbon is reacted with, characterized in that for producing an aromatic compound as a main component an aromatic hydrocarbon and hydrogen.

The method for producing an aromatic compound and hydrogen using the lower hydrocarbon of the third invention as a raw material is the same as in the production method of the second invention, wherein the added amount of carbon monoxide and / or carbon dioxide is the total amount supplied to the reaction. It is characterized by being in a range of 0.01 to 30% as a volume% in the raw material gas.

From the above results, according to the present invention, the aromatic compound- forming catalyst is one or more selected from the group consisting of rhenium or a compound thereof, and a group consisting of zinc, Ga, iron or a compound thereof. substantially closed pores 4.5~6.5Å diameter and one or more selected from, the surface area is that is supported on a porous metallosilicate is 200~1000m ² / g, the catalyst By using this catalyst when aromatizing lower hydrocarbons, the high-value-added products such as benzene, toluene, xylene and naphthalene are added to the reaction. Hydrocarbons and hydrogen can be produced particularly efficiently.
In addition, by carrying out this reaction in the presence of carbon monoxide or carbon dioxide, the reaction conversion rate of lower hydrocarbons can be improved, and it is effective to reduce the production rate of aromatic compounds such as benzene and hydrogen. And stable catalytic ability can be obtained over a long period of time.

The present invention is applied to a technical field in which an aromatic compound mainly composed of an aromatic hydrocarbon and hydrogen are produced by reacting a lower hydrocarbon in the presence of a catalyst (catalyst material + porous support) described later.
Here, as the lower hydrocarbon used as a raw material in the present invention, natural gas containing at least 50% by weight, preferably at least 70% methane, and the like can be shown. If the methane content is within this range, other saturated and unsaturated hydrocarbons having 2 to 6 carbon atoms may be included. Examples of these hydrocarbons include ethane, ethylene, propane, propylene, n-butane, isobutane, n-butyne and isobutene.

In the catalyst of the present invention, a porous metallosilicate is used as a support. For example, in the case of aluminosilicate, molecular sieve 5A (UTA), faujasite (NaY) and NaX, ZX-5, ZSM-11, ZSM-22, ZSM, which are porous carriers made of silica and alumina having various compositions. -48, β-HZSM, zeolite carriers having micropores and channels in porous carriers such as ALPO-5, SAPO-5, VPI-5, MCM-22 and the like mainly composed of phosphoric acid can be exemplified. . Further, mesoporous porous carriers such as FSM-16 and MCM-41 characterized by mesoporous cylindrical pores (channels) containing silica as a main component and partly alumina as a component are used as silicon alkoxides. Examples thereof include a modified mesoporous material whose mesopore diameter is adjusted by a CVD method using the like. As the metallosilicate, in addition to aluminosilicate and ferrosilicate, a porous carrier such as titanosilicate composed of silica and titania can be used.
Further, for example, in the case of aluminosilicate, a silica / alumina content ratio of a commonly available porous carrier having a silica / alumina ratio of 1 to 8000 can be used. In order to carry out the grouping reaction at a practical lower hydrocarbon conversion and selectivity to aromatic compounds, the silica / alumina ratio is preferably 10-100.

However, the metallosilicate used in the present invention is one having micro and mesopores substantially in the diameter range of 5.5 ± 1 mm. Substantially means that the presence of some pores outside this range is permissible, and most of them are within the scope of the present invention if they are within this range. Furthermore, the thing whose surface area is 200-1000 m < ² > / g is more preferable. The diameter preferably satisfies the above range in all directions, but an irregularly shaped pore may satisfy the above range in one direction. Further, it is more desirable that the above-mentioned diameter has a lower limit of 5.0 mm and an upper limit of 6.0 mm.

  The size of the above pores is almost the same as the size of the molecule of the aromatic compound. According to the study by the present inventors, a catalyst using a metallosilicate having a pore size in this range as a carrier is a lower hydrocarbon. It became clear that it showed a specific activity in the formation of aromatic compounds. Specifically, the pores physically hinder the growth of large molecules (for example, polymers that easily generate coke), suppress carbon generation on the catalyst surface, and exhibit good activity. That is, when carbon is generated and accumulated on the catalyst surface, the activity as a catalyst is lost, but in the present invention, the generation of carbon is suppressed as described above, so that the performance excellent as a catalyst is achieved. Demonstrate. Even if the pore size deviates from the above range either above or below, the above specific activity is impaired.

Next, in the catalyst of the present invention, the catalyst material is selected from one or more selected from the group consisting of rhenium or a compound thereof and optionally selected from the group consisting of zinc, Ga , iron or a compound thereof. 1 or more types are included. In addition, the catalyst material includes at least one selected from the group consisting of chromium, tungsten, molybdenum or a compound thereof and one or more selected from the group consisting of a rare earth metal or a compound thereof. One can mention.

The catalyst material can be prepared as a precursor when it is supported on the metallosilicate. Examples of precursors include halides such as chloride and bromide, mineral salts such as nitrate, sulfate and phosphate, carboxylates such as carbonate, acetate and oxalate, metal carbonyl complexes and cyclopenta An organic metal salt such as a dienyl complex can be exemplified.
For example, examples of rhenium precursors include rhenium carbonyl compounds (Re ₂ (CO) ₁₀ , Re ₆ (CO), (C ₅ H ₅ ) ₂ Re (CO) ₂ , CH ₃ ReO ₃ ) acid. And halides such as chloride and bromide, mineral salts such as nitrate, sulfate and phosphate, carboxylates such as carbonate, acetate and oxalate.
Moreover, a complex complex salt or complex oxide can also be used as a precursor of each material.

The catalyst of the present invention can be obtained by supporting these precursors on a metallosilicate.
In the present invention, the amount of the catalyst material supported on the metallosilicate is not particularly limited, but is 0.001 to 50%, preferably 0 in mass ratio based on the total catalyst weight for each group. .01 to 40% is a good loading range.
When a catalyst material is selected from a plurality of groups, the total supported amount of the catalyst material is desirably 0.002 to 50%, preferably 0.02 to 40% based on the total catalyst weight. In addition, the said carrying amount range shows the carrying amount as a precursor, when using a precursor for a catalyst material.

The catalyst material is supported on a metallosilicate by impregnating and supporting the metallosilicate as an aqueous solution of the above-mentioned metal precursor or an organic solvent such as alcohol, or by supporting by an ion conversion method, and then inactive. There is a method of heat treatment in gas or oxygen gas. An example of this method will be described in more detail. First, for example, a metallosilicate support is impregnated and supported with a rhenium nitrate aqueous solution, and further dried to remove an appropriate amount of solvent, and then in a nitrogen-containing oxygen stream or a pure oxygen stream. Among them, a metallosilicate catalyst carrying rhenium can be produced by heat treatment at 250 to 800 ° C., preferably 350 to 600 ° C.
Also, when a catalyst is obtained using a complex oxide or complex complex salt, a catalyst comprising a complex oxide salt or complex complex salt can be obtained by the same supporting method or heat treatment method.

When each catalyst material is supported on the metallosilicate, the catalyst materials may be sequentially supported on the metallosilicate, or a part or all of them may be supported at once. However, in the present invention, it is desirable to carry an important material first and then carry other catalyst materials sequentially or all at once.
This is presumably because the first component that plays an especially important role as a catalyst is supported first, whereby the first component is reliably supported on the metallosilicate, and the durability of the catalyst is improved.

The catalyst of the present invention obtained as described above may be any of powder, pellets, and other shapes, and the shape is not particularly limited.
In addition, the catalyst used in the present invention has a catalyst activation process including pretreatment with hydrogen gas, hydrazine, a metal hydride compound such as BH ₃ , NaH, AlH _3, etc. in order to shorten the induction period for producing an aromatic compound. You may give it.

In the method for producing an aromatic compound and hydrogen using the lower hydrocarbon as a raw material of the present invention, the above-described lower hydrocarbon is used as a raw material in the reaction in the presence of the above-described catalyst.
In this case, the reaction is performed in the presence of one or two kinds of gases selected from carbon monoxide and carbon dioxide. By performing the reaction in the presence of carbon monoxide and / or carbon dioxide, it is possible to improve the reaction conversion rate of the lower hydrocarbon and to further suppress the significant reduction in the production rate of benzene and hydrogen.
Carbon monoxide and carbon dioxide may be added singly or in combination.
The addition amount of carbon monoxide and / or carbon dioxide is in the range of 0.01 to 30%, preferably 0.1 to 25% as a volume% in the raw material gas supplied to the reaction system. This is because if the amount added is less than this range, the effect is small, and if the amount added is greater than this range, the volumetric efficiency of the reactor deteriorates.

Further, the lower hydrocarbon conversion reaction of the present invention is usually carried out in a batch-type or flow-type reaction mode, but is preferably carried out in a flow-type reaction mode such as a fixed bed, moving bed or fluidized bed. .
The reaction is desirably carried out by bringing a lower hydrocarbon raw material such as methane into contact with the catalyst in the presence of carbon monoxide and / or carbon dioxide at a temperature of 300 to 800 ° C, preferably 450 to 775 ° C.
The reaction is suitably carried out at 0.1 to 10 atmospheres, preferably 1 to 7 atmospheres. The weight hourly space velocity (WHSV) is 0.1 to 10, preferably 0.5 to 5.0.
Unreacted raw material recovered from the reaction product and carbon monoxide or carbon dioxide added to the reaction can be recycled to the aromatization reaction.

By the above reaction, an aromatic compound mainly containing an aromatic hydrocarbon such as benzene and toluene can be obtained. In addition, the kind of aromatic compound obtained and the ratio of a compound change with raw materials, and are not prescribed | regulated uniformly. In addition, high-purity hydrogen is obtained with this reaction.
Either one of the above-described aromatic compound and hydrogen may be used effectively, or both may be used effectively, and the method of use is not limited in the present invention.
Moreover, the field of use is not particularly limited.

Hereinafter, the present invention will be described in more detail by way of examples.
The methane conversion rate, hydrocarbon selectivity, hydrocarbon distribution and hydrogen production rate used in this example were defined as follows.
Methane conversion rate (%) = [(number of raw material methane moles−number of unreacted methane moles) / number of raw material methane moles] × 100
Hydrocarbon selectivity (%) = [number of moles of methane converted to all hydrocarbons produced / (number of moles of raw material methane−number of unreacted methane moles)] × 100
Hydrocarbon distribution (%) = [number of moles of methane equivalent of hydrocarbon of interest / number of moles of methane equivalent of all hydrocarbons produced] × 100
Hydrogen production rate = nmol number of hydrogen produced per second per gram of catalyst Benzene production rate = nmol number of benzene produced per second per gram of catalyst

Example 1
As a precursor of the catalyst material, 1.20 g of ammonium pararhenate was dissolved in 10 ml of distilled water, and HZSM-5 (silica / alumina ratio = 40, surface area of 870 m ² / g, pore diameter = 5) as a metallosilicate support. .4 × 5.6 Å) powder was added and evaporated to dryness using a rotary vacuum evaporator with sufficient stirring to obtain a HZSM-5 carrier of ammonium pararhenate. Since the pores of the carrier are not uniform circular holes, the minimum width and the maximum width are shown. After filling this into a quartz reaction tube (1.2 cm diameter, 30 cm length, V-shaped type), it was fired at 400 ° C. for 2 hours under a pure oxygen gas flow (40 ml / min, 1 atm) as a light grass-colored powder. A catalyst having 6% rhenium supported on HZSM-5 based on the total catalyst weight (hereinafter abbreviated as Re (6%) / HZSM-5) was obtained.

Further, during the production of the catalyst, in addition to 1.20 g of the ammonium pararhenate, Zn (NO ₃ ) ₂ , GaCl ₃ , FeCl ₃ or CoCl ₂ was added as a precursor, respectively, and dissolved in 10 ml of distilled water, In the same manner as above, a catalyst containing 6% rhenium and 1% Zn, Ga, Fe, Co by mass ratio based on the total catalyst weight was obtained. Further, in the case of using a precursor in which GaCl ₃ is added to ammonium pararhenate, MCM-22 (pore diameter 5.5 mm) or HZSM-11 (5.1 × 5.5 mm) is used as a carrier, and A catalyst was obtained by the same method.

  A quartz reaction tube (inner diameter: 8 mm) of a fixed bed flow reactor was charged with 0.3 g of each of the above catalysts, and a reaction gas of 2% carbon dioxide gas added to methane at a reaction temperature of 750 ° C. and 3 atm was 26 ml / The production reaction activity of benzene and hydrogen by the aromatization reaction of methane supplied at a flow rate of min was investigated. The results after 200 minutes from the reaction are shown in Table 1.

  As is apparent from Table 1, in the reaction using the catalyst of the present invention, benzene and naphthalene are obtained from methane, which is a lower hydrocarbon raw material, at a particularly high production rate, and it is excellent in forming an aromatic compound. Along with this, hydrogen is produced at a high production rate, and the production capacity of hydrogen is excellent. From the above, it can be seen that an excellent catalyst ability is exhibited by defining the pore diameter of the porous metallosilicate.

( Reference Example 1 )
In the same manner as in Example 1, ammonium pararhenate was supported on metallosilicate carrier HZSM-5 (silica / alumina ratio = 46, surface area 800 m2 / g, pore size = 5.4 × 5.6 mm). Calcination and pulverization were performed to obtain a catalyst having 6% rhenium supported on HZSM-5 based on the total catalyst weight.
A catalyst tube made of quartz (inner diameter: 8 mm) of a fixed bed flow type reactor was charged with 0.3 g of the catalyst, and a gas obtained by adding a predetermined amount of carbon monoxide to methane gas as a raw material gas at a reaction temperature of 750 ° C. and 3 atm. The methane aromatization reaction was carried out at a flow rate of min.
In addition to unreacted methane, hydrogen, carbon monoxide, carbon dioxide, hydrocarbons having 2 to 5 carbon atoms, benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, dimethylnaphthalene, anthracene are contained in the reaction tube effluent. Etc. existed. Table 2 shows the results after 200 minutes, 400 minutes, and 2000 minutes after the start of the reaction.
As a comparative example, methane aromatization reaction was performed in the same manner as in Reference Example 1 except that carbon monoxide was not added to methane gas. Table 2 shows the results after 100 minutes, 400 minutes and 1440 minutes after the start of the reaction.

  As is apparent from Table 2, the reaction conversion rate of the lower hydrocarbon is greatly improved by carrying out the reaction in the presence of carbon monoxide. In addition, in raw materials that do not contain carbon monoxide, the rate of production of aromatic compounds and hydrogen has been remarkably reduced over time, but this reduction is suppressed in those that react in the presence of carbon monoxide, Stable performance is obtained for a long time.

( Reference Example 2 )
In this reference example, the methane aromatization reaction was performed in the same manner as in Reference Example 1 except that the addition of carbon monoxide to the raw material gas in Reference Example 1 was changed to the addition of carbon dioxide. The results after 420 minutes and 2000 minutes after the start of the reaction are shown in Table 3.
As is clear from Table 3, when the reaction is performed in the presence of carbon dioxide, as in Reference Example 1 , a significant improvement in the reaction conversion rate and a decrease in the production rate over time are suppressed.
In these examples , evaluation was performed only in the presence of carbon monoxide or carbon dioxide, but it was confirmed that the same effect can be obtained in an environment where both carbon monoxide and carbon dioxide coexist. Yes.

Claims (3)

A catalyst for reacting a lower hydrocarbon containing methane in the presence of carbon monoxide and / or carbon dioxide, one or more selected from the group consisting of rhenium or a compound thereof , zinc, Ga, iron or and a least one selected from the group consisting of these compounds as a catalyst material, and substantially possess pores 4.5~6.5Å diameter as a carrier for carrying the catalyst material, the surface area A lower hydrocarbon aromatic compound conversion catalyst comprising a porous metallosilicate of 200 to 1000 m ² / g . The presence of a catalyst according to claim 1, in the presence of carbon monoxide and / or carbon dioxide, aromatic compounds by reacting lower hydrocarbon containing methane as a main component an aromatic hydrocarbon and a hydrogen A process for producing an aromatic compound and hydrogen using a lower hydrocarbon as a raw material, characterized in that it is produced. 3. The lower hydrocarbon as a raw material according to claim 2, wherein the amount of carbon monoxide and / or carbon dioxide added is in the range of 0.01 to 30% as a volume% in the total raw material gas supplied to the reaction. And a method for producing hydrogen.