JP2019037939A - Catalyst for lpg synthesis - Google Patents

Abstract

To provide a catalyst used for producing LPG from syngas, the catalyst having a high conversion rate to LPG and capable of reducing COby-products.SOLUTION: A catalyst for LPG synthesis has: a core containing a catalyst containing one or more element selected from Zn, Cr, Cu, Al, Zr, In and Pd, capable of generating methanol from at least carbon monoxide and hydrogen as raw material; and a shell containing zeolite having a 10 membered or 12 membered ring structure formed outside the core. In the catalyst the zeolite may be MF type I zeolite.SELECTED DRAWING: None

Description

  The present invention relates to a catalyst used for liquefied petroleum gas (LPG) synthesis.

Liquefied petroleum gas (LPG) is produced by refining petroleum or natural gas associated gas from petroleum refining. However, a technique for producing LPG from synthesis gas (mixed gas of CO and H ₂ ) derived from various raw materials is desired from the viewpoint of reduction of oil reserves and regional ubiquity.

As a conventional technique for obtaining hydrocarbons containing LPG from synthesis gas, two types are known: a one-stage method by Fischer-Tropsch reaction, and a two-stage method for obtaining hydrocarbons via methanol or dimethyl ether (DME).
The one-stage method has a wide distribution of generated hydrocarbons and is not suitable for efficiently producing only the target product. There is also a problem in that carbon dioxide (CO ₂ ) is by-produced in large quantities.
On the other hand, in the two-stage method, the reaction is divided into two stages, and the temperature and pressure suitable for the reaction in the first stage and the second stage are greatly different, so that there is a problem that the process becomes complicated and the cost is high.
Therefore, there is a demand for the development of a technology that can efficiently produce LPG from synthesis gas in a single stage and that has little by-product of carbon dioxide.

In Non-Patent Document 1, there is a method of generating LPG with a catalyst obtained by physically mixing a Zn-Cr-based synthesis catalyst and a β-zeolite containing metal Pd in a reaction of converting a synthesis gas to LPG using a Zn-Cr hybrid catalyst. Disclosed.
Non-Patent Document 2 discloses that a catalyst having a core-shell structure having a Cr—Zn core and a SAPO34 (CHA-type zeolite) shell can be used to convert synthesis gas into hydrocarbons with high selectivity.

Qingle Ge, et al., Journal of Molecular Catalysis A, Vol.278, 2007, Page 215-219 Jinjing Li, et al., Chinese Journal of Catalysis, Vol. 36, 2015, Page 1131-1135

In the methods disclosed in Non-Patent Documents 1 and 2, a larger amount of CO ₂ than by-produced LPG is produced as a by-product, and there is a problem in efficiency. In addition, in the method disclosed in Non-Patent Document 2, compared to the case where only the core is used as the catalyst, the conversion rate of CO is remarkably reduced by using the core-shell type catalyst, and there is a problem in productivity. It is an object of the present invention to provide a technique with a high conversion rate to LPG and reduced CO ₂ by-product when LPG is produced from synthesis gas by a one-stage method.

The present inventors have advanced research to solve the above-mentioned problems, and a core containing a catalyst capable of producing methanol using at least carbon monoxide and hydrogen as raw materials, and a shell containing zeolite formed outside the core, The present invention has been completed by finding that the above-mentioned problems can be solved when the zeolite contained in the shell has a specific structure.
The present invention includes the following gist.

[1] A core containing at least one component selected from the group consisting of zinc, chromium, copper, aluminum, zirconium, indium and palladium, which can produce methanol using at least carbon monoxide and hydrogen as raw materials, and the core And a shell containing zeolite having a 10-membered or 12-membered ring structure formed on the outside of the catalyst.
[2] The catalyst according to [1], wherein the core contains zinc and chromium or copper.
[3] The catalyst according to [1] or [2], wherein the core contains zinc and chromium.
[4] The catalyst according to any one of [1] to [3], wherein the core contains aluminum and / or palladium.
[5] The catalyst according to any one of [1] to [4], wherein the zeolite is MFI type zeolite.
[6] The catalyst according to any one of [1] to [5], wherein 80% or more of the core is covered with a shell containing the zeolite.

According to the present invention, there is provided a catalyst used in producing the LPG from synthesis gas, can provide high catalytic have conversion to LPG and which the CO ₂ byproduct can be reduced.

  Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents. Various modifications can be made within the scope of the gist.

An embodiment according to the present invention is a catalyst for LPG synthesis, which includes a core containing a catalyst capable of producing methanol using at least carbon monoxide and hydrogen as raw materials, and a 10-membered ring formed outside the core, Zeolite having a 12-membered ring structure is included. Such a catalyst having a core and a shell around the core is also referred to as a core-shell type catalyst, which is a core-shell type catalyst, and contains a zeolite having a 10-membered or 12-membered ring structure in the shell, thereby converting to a high LPG. And a catalyst capable of reducing CO ₂ by-product. The catalyst contained in the core is also referred to as “first catalyst”.

The core forming the core-shell type catalyst of the present embodiment includes a first catalyst that can generate methanol using at least carbon monoxide and hydrogen as raw materials. The first catalyst can be used without any particular limitation as long as it promotes the above reaction. Typically, a metal catalyst such as Zn, Cr, Cu, Al, Zr, In, Ni, Pd, Pt, Ru, Rh, and the like may be used, or a catalyst using only one of these may be used, or A hybrid catalyst in which two or more kinds are combined may be used.
In one form, a 1st catalyst may be a form containing Zn and Cr, or a form containing Cu. In another embodiment, Zn and Cr may be contained, or Cu may be contained, and Al and / or Pd may further be contained. Further, the metal catalyst may be supported on a support.

  The particle size of the first catalyst is not particularly limited as long as it can be charged into the reaction apparatus. Usually, it is 50 μm or more, may be 250 μm or more, and may be 500 μm or more. Also, it is usually 30 mm or less, 20 mm or less, or 10 mm or less.

The shell forming the core-shell type catalyst of the present embodiment includes zeolite having a 10-membered ring or 12-membered ring structure. By coating the first catalyst with a zeolite having a specific structure and having a core-shell structure, a catalyst having a high conversion rate to LPG and capable of reducing CO ₂ by-product can be obtained. The present inventors have conceived. Although the detailed mechanism by which such an effect occurs is unknown, the present inventors consider as follows. That is, the reaction promoted by the metal catalyst present in the core can promote not only the methanol production direction but also the reverse reaction. However, the reverse reaction can be suppressed by using a zeolite having a 10-membered ring or 12-membered ring structure as a shell. Therefore, a reaction for producing carbon dioxide as a by-product is less likely to occur, and a high conversion rate to LPG and a reduction in CO ₂ by-product are achieved.

  Examples of the zeolite having a 10-membered ring structure include zeolites such as AEL, EUO, FER, HEU, MEL, MFI, NES, TON, and WEI, which are codes defined by International Zeolite Association (IZA). Examples of the zeolite having a 12-membered ring structure include zeolites such as AFI, ATO, BEA, CON, FAU, GME, LTL, MOR, NTW, and OFF. Of these, MFI zeolite is preferably used.

Zeolite contained in the shell include, but are not otherwise limited so long as it has a 10-membered ring or 12-membered ring structure, specific surface area is usually 100 m ² / g or more, preferably 200 meters ² / g or more, and usually 600 meters ² / g or less, preferably 500 m ² / g or less.
The average particle diameter (median diameter D ₅₀ ) is usually 0.05 μm or more, preferably 0.5 μm or more, and usually 100 μm or less, preferably 50 μm or less.

  The shell may contain components other than zeolite having a 10-membered ring or 12-membered ring structure as long as the effects of the present invention are not impaired, but the shell may be composed of zeolite having a 10-membered ring or 12-membered ring structure. preferable.

The catalyst for LPG synthesis of this embodiment is obtained by coating the surface of the core containing the first catalyst with a shell containing zeolite having a 10-membered ring structure or a 12-membered ring structure.
In this embodiment, the core containing the first catalyst is coated with zeolite, but 80% or more of the core containing the first catalyst is preferably coated with a shell containing zeolite, and 85% or more is coated. It is more preferable that 90% or more is covered.

In the LPG synthesis catalyst of the present embodiment, the content of the first catalyst contained in the core is usually 10% by mass or more, preferably 20% by mass or more, and usually 90% by mass or less. Preferably it is 80 mass% or less.
On the other hand, in the LPG synthesis catalyst of the present embodiment, the content of the zeolite having a 10-membered or 12-membered ring structure contained in the shell is usually 10% by mass or more, preferably 20% by mass or more, Moreover, it is 90 mass% or less normally, Preferably it is 80 mass% or less.

The method for producing the LPG synthesis catalyst of the present embodiment is not particularly limited as long as the LPG synthesis catalyst having the above-described structure can be produced. For example, the following method is exemplified.
First, the first catalyst as a core is manufactured. Although there is no restriction | limiting in particular in the manufacturing method of a 1st catalyst, Manufacturing by a coprecipitation method is illustrated. As an example of the production method by the coprecipitation method, there is a method of obtaining a suspension by mixing a metal salt solution containing an element constituting the first catalyst and an aqueous solution containing a precipitant.
As the metal salt, one having excellent solubility in water is preferable because it can be easily removed in the purification step of the resulting catalyst. Examples of such salts include acetate, fluoride, chloride, bromide, iodide, carbonate, sulfate, nitrate, and hydrates of these salts (the acetate to nitrate), As well as metal complexes. Among these, transition metal salts are preferably carbonates and nitrates, and more preferably nitrates because the anion content can be easily removed by heating.

The precipitating agent is dissolved in a solvent to generate hydroxide ions. The precipitating agent is not particularly limited as long as it has such properties, but is preferably an alkaline compound, and examples thereof include sodium hydroxide, potassium hydroxide, ammonia, urea, ammonium carbonate and the like. Of these, ammonia, urea, and ammonium carbonate are more preferred, and ammonium carbonate is even more preferred from the viewpoint that metal ions are not contained and the metal composition in the catalyst can be easily controlled.
Examples of the method of mixing the solution include a method of dropping a solution containing a precipitating agent into the metal salt solution, preferably 0.1 hour to 10 hours, more preferably 0.5 hours to 5 hours, Preferably it is dripped over 1 hour or more and 3 hours or less. Moreover, after mixing of the solution is completed, the dropped product may be continuously stirred.
At the time of mixing the solvent, any solution may be a suspension containing a solid component.

The solid content is recovered from the obtained suspension, dried after washing, and then calcined.
The drying temperature may be a temperature at which moisture can be substantially removed, and is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 60 ° C. or higher and 130 ° C. or lower. The drying time is preferably 1 hour or more and 48 hours or less, and more preferably 12 hours or more and 36 hours or less.
The temperature at which the precipitate is baked is preferably 300 ° C. or higher and 800 ° C. or lower, more preferably 300 ° C. or higher and 600 ° C. or lower, because the hydroxide can be sufficiently converted into an oxide by dehydration. Preferably, it is 400 degreeC or more and 600 degrees C or less.
The time for firing the precipitate is preferably 1 hour or more and 48 hours or less, more preferably 1 hour or more and 24 hours or less, and further preferably 1 hour or more and 12 hours or less.
A metal component may be added to the first catalyst obtained by calcination by the Incipient Wetness method, the evaporation to dryness method, or the like.

As a method of coating the first catalyst with a shell catalyst, the first catalyst is impregnated with a solution containing silica, and further, a zeolite powder having a 10-membered ring structure or a 12-membered ring structure is added and stirred, and the resulting solid is obtained. The method of baking is illustrated.
There is no restriction | limiting in particular in the solution containing a silica, For example, a commercially available silica sol is illustrated. As the zeolite having a 10-membered ring or 12-membered ring structure, a commercially available zeolite can be used, and a powder prepared by a hydrothermal synthesis method can also be used.
Further, the first catalyst may be molded, pulverized, and sized before being coated with the shell catalyst.

Although there is no restriction | limiting in the weight ratio of the shell catalyst with respect to a 1st catalyst, 0.1 to 50 times are preferable and 0.2 to 30 times are more preferable.
The temperature at which the solid is fired is preferably 300 ° C. or higher and 800 ° C. or lower, more preferably 300 ° C. or higher and 600 ° C. or lower, because the hydroxide can be sufficiently converted into an oxide by dehydrating the hydroxide. More preferably, the temperature is 400 ° C. or more and 600 ° C. or less.
The time for firing the solid is preferably 1 hour or more and 48 hours or less, more preferably 1 hour or more and 24 hours or less, and further preferably 1 hour or more and 12 hours or less.

  In the presence of the produced LPG synthesis catalyst, LPG is synthesized by converting a synthesis gas containing at least carbon monoxide and hydrogen. The molar ratio of hydrogen / carbon monoxide in the synthesis gas is usually 0.5-5, preferably 0.5-2.

In the conversion reaction using the LPG synthesis catalyst of this embodiment, a flow-type fixed bed process may be adopted as a one-stage reaction process.
In the conversion reaction, the ratio (W / F) of the weight (W) (g) of the core catalyst to the feed gas velocity (F) (mol / h) of the synthesis gas is usually 0.1 to 100 g · h / mol. It is preferable that it is 0.0-50 g * h / mol. The reaction temperature for the conversion reaction is usually 250 to 400 ° C.
It is preferable that it is 250-350 degreeC. The reaction pressure is usually 0.1 to 10 MPa, and preferably 0.3 to 5 MPa.

  Before performing the synthesis gas conversion reaction, the LPG synthesis catalyst may be activated as necessary. The activation can be performed using a gas containing hydrogen in a pressure range of 10 to 10 MPa, a temperature range of 300 to 500 ° C., and an activation time range of 1 to 50 hours.

By using the LPG synthesis catalyst according to the present embodiment, a high conversion rate to LPG and a reduction in CO ₂ by-product can be achieved, so that an efficient reaction can be achieved.

The catalyst reacted for a certain period of time may be regenerated and used after being subjected to a regeneration treatment. Specifically, a catalyst having a reduced CO conversion rate can be regenerated using various known catalyst regeneration methods. Specifically, for example, it can be regenerated using air, nitrogen, water vapor, hydrogen or the like, and it is preferable to regenerate using a gas containing air or hydrogen.
A method for performing the reproduction process using the above reproduction method is not particularly limited. For example, when the reaction is carried out in a fixed bed reactor, a plurality of reactors are provided in parallel, and when the CO conversion rate decreases, the contact between the catalyst and the reaction raw material is stopped, and the catalyst is regenerated. To serve. In the fixed bed reactor, the reaction time and the regeneration time are appropriately adjusted, that is, the time is appropriately adjusted for switching the reaction step and the regeneration step in the operation, thereby continuously operating at a CO conversion rate in the above preferred range. can do.

In the present specification, the CO conversion rate is defined by “(1− (unreacted CO (mol) in the produced reaction product / CO (mol) in the raw synthesis gas) × 100 (mol%)”. The LPG selectivity refers to the proportion (mol%) of carbon contained in the generated paraffin (LPG) having 3 or 4 carbon atoms out of the carbon contained in the reaction product. The CO ₂ selectivity refers to the proportion (mol%) of carbon contained in the CO ₂ produced by the reaction out of the carbon contained in the reaction product. The LPG yield is “produced by reaction. the carbon contained in LPG (mol) / raw material gas of CO (mol) × 100 (mol%) is a value defined by ", CO ₂ CO ₂ (mol generated in" reaction to the by-product ratio ) / CO (mol) in raw material gas × 100 (mol%) ” A.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, it cannot be overemphasized that the scope of the present invention is not limited to the aspect shown in a following example.

<Example 1-1>
A Zn—Cr catalyst was prepared by a coprecipitation method. 14.6 g of zinc nitrate hexahydrate and 9.8 g of chromium nitrate nonahydrate were dissolved in 100 mL of distilled water to prepare a catalyst precursor solution. The molar ratio of zinc and chromium in the catalyst precursor solution was 2/1.
A solution obtained by dissolving 9.6 g of ammonium carbonate in 100 mL of distilled water was added dropwise to the catalyst precursor solution heated to 70 ° C. The dropwise addition was performed over 1 hour, and during that time, the pH was always 7-8. After completion of the dropwise addition, stirring was continued at 70 ° C. for 3 hours. The obtained precipitate was filtered, washed several times with demineralized water, dried at 120 ° C. overnight, and further calcined in air at 500 ° C. for 1 hour to obtain a Zn—Cr catalyst powder.

  The addition of Pd was performed by the Incipient Wetness method. To 1 g of Zn—Cr powder, 5% dinitrodiammine palladium (II) aqueous solution was added so that Pd would be 1% by weight, followed by ultrasonic treatment for 30 minutes, followed by drying at 120 ° C. overnight. Firing was performed in air at 400 ° C. for 1 hour. The obtained powder was sized to 0.85 mm-1.70 mm to obtain a first catalyst 1 used as a core.

  In an 80 mL container made of PTFE, 9.56 g of distilled water, 7.76 g of 10% tetrapropylammonium hydroxide solution (TPAOH), 2.81 g of ethanol (EtOH), 0.14 g of aluminum nitrate nonahydrate, tetraethyl ortho 3.25 g of silicate (TEOS) was added and stirred at room temperature for 6 hours to obtain a synthetic gel. The molar ratio of the synthetic gel at this time was water: TPAOH: EtOH: aluminum nitrate: TEOS = 120: 0.68: 8: 0.048: 2.

  The synthetic gel was put into a PTFE pressure vessel, and hydrothermal synthesis was performed at 180 ° C. for 24 hours using a hydrothermal synthesis reactor (manufactured by HIRO). During this time, the PTFE pressure vessel was rotated at a speed of 2 rpm. After hydrothermal synthesis, the contents were collected, and the resulting solid was separated and washed thoroughly with distilled water. Thereafter, it was dried at 120 ° C. for 12 hours and calcined in air at 500 ° C. for 5 hours to obtain a zeolite powder. When the X-ray diffraction measurement was performed, the obtained zeolite was ZSM-5.

  To 0.6 g of the first catalyst 1 used as the core, 6 mL of silica gel (Ludox-40) was impregnated, 0.4 g of synthesized ZSM-5 powder was added, and shaken vigorously until a uniform shell was formed. The obtained solid was sieved to remove the ZSM-5 powder which did not adhere as a shell, and then calcined in air at 500 ° C. for 2 hours to obtain a core-shell type catalyst 1. The core-shell type catalyst increased in weight by 60% compared to the core catalyst.

<Manufacturing LPG>
The production reaction of LPG uses hydrogen: carbon monoxide: carbon dioxide: argon = 62.78: 29.3: 4.95: 2.97 (molar ratio) as a raw material gas, and the core-shell type catalyst 1 (weight of the core catalyst) Was used in a fixed bed reactor. Prior to the reaction, pure hydrogen was circulated and the catalyst was reduced at 400 ° C. for 4 hours. After the reduction, the reactor was cooled to room temperature, switched to synthesis gas (W / F = 10 g · h / mol, W is the weight of the core catalyst), and then reacted at 400 ° C. and 5 MPa.
The gas product was analyzed by on-line gas chromatography, and argon was used as an internal standard substance, and CO conversion, CO ₂ selectivity, LPG selectivity, LPG yield, and CO ₂ byproduct rate were determined. The results are shown in Table 1.

<Comparative Examples 1-1 and 1-2>
An example carried out in the same manner as in Example 1-1 except that 0.5 g of the first catalyst 1 was used to produce LPG was made Comparative Example 1-1.
Comparative Example 1 was carried out in the same manner as in Example 1-1 except that 0.5 g of the first catalyst 1 and 0.3 g of zeolite synthesized by a hydrothermal synthesis reactor were used. 2.

<Example 2-1>
In Example 1-1, when carrying out the coprecipitation method, a catalyst was prepared by adding aluminum nitrate nonahydrate to Zn: Cr: Al = 2: 1: 0.3 (molar ratio), Example 2-1 was carried out in the same manner as in Example 1-1 except that core-shell type catalyst 2 prepared using first catalyst 2 to which Pd was not added was used.

<Comparative Example 2-1>
An example carried out in the same manner as in Example 1-1 except that LPG was produced using only the first catalyst 2 was designated as Comparative Example 2-1.

<Example 3-1>
In Example 1-1, using the first catalyst 3 to which Pd was not added, using the core-shell type catalyst 3 prepared using commercially available β zeolite instead of hydrothermally synthesized ZSM-5 powder, the reaction temperature Example 3-1 was carried out in the same manner as in Example 1-1 except that the temperature was changed to 350 ° C.

<Comparative Example 3-1>
An example performed in the same manner as in Example 3-1 except that LPG was produced using only the first catalyst 3 was taken as Comparative Example 3-1.

In Table 1, it is clear that a high CO conversion and a high LPG yield can be obtained by using a core-shell catalyst in which the first catalyst is covered with zeolite as compared with the case of only the first catalyst.
In addition, when the first catalyst and zeolite are physically mixed and used, the byproduct rate of CO ₂ is higher than the yield of the target LPG, whereas when the core-shell type catalyst is used. The yield of LPG is higher than the CO ₂ byproduct rate.
That is, according to the present invention using a core-shell catalyst having a zeolite having a specific structure as a shell, LPG can be efficiently produced with a low CO _{2 by} -product amount.

Claims (6)

  A core containing at least one component selected from the group consisting of zinc, chromium, copper, aluminum, zirconium, indium and palladium, capable of producing methanol using at least carbon monoxide and hydrogen as raw materials; and on the outside of the core And a shell containing zeolite having a 10-membered ring structure or a 12-membered ring structure.   The catalyst according to claim 1, wherein the core contains zinc and chromium or copper.   The catalyst according to claim 1 or 2, wherein the core contains zinc and chromium.   The catalyst according to any one of claims 1 to 3, wherein the core contains aluminum and / or palladium.   The catalyst according to any one of claims 1 to 4, wherein the zeolite is MFI-type zeolite. The catalyst according to any one of claims 1 to 5, wherein 80% or more of the core is covered with a shell containing the zeolite.