JP5617520B2 - Method for producing lower olefin - Google Patents

Description

  The present invention relates to a process for producing lower olefins, especially propylene, and a zeolite catalyst for use in the process.

  Propylene is used in large quantities as a raw material for the synthesis of acrolein, acrylonitrile, isopropyl alcohol, acetone, glycerin, cumene, propylene oxide, allyl alcohol, and the like. In addition, polypropylene obtained by polymerizing propylene is used in a wide range of fields such as building materials and food containers.

  Many methods for producing propylene have been conventionally known. For example, a method for producing propylene from ethanol using a zeolite catalyst has been reported.

  As a zeolite catalyst, for example, Patent Document 1 discloses a ZSM-5 type zeolite catalyst in which acid sites on the outer surface are inactivated using diphenylsilane. However, this catalyst is used for producing olefins from ketones, not for producing propylene from ethanol.

  Patent Document 2 discloses a method for producing olefins by bringing methanol into contact with a zeolite catalyst. As the zeolite catalyst, a ZSM-5 type zeolite catalyst in which the outer surface active sites are deactivated by using diphenylsilane. Is used.

  Patent Document 3 discloses a method for producing propylene by bringing ethanol into contact with a zeolite catalyst. As the zeolite catalyst, ZSM modified with a compound containing a metal of Group 6 and / or Group 7 of the periodic table is disclosed. A -5 type zeolite catalyst is used.

JP 2009-208006 A JP 2009-255014 A JP 2008-289991 A

The zeolite catalyst disclosed in Patent Document 2 is for producing olefins from methanol, and not for producing olefins, particularly propylene, from ethanol. Further, the methanol conversion is low and the olefin selectivity is as low as 44%. Propylene selectivity is not disclosed, but STY (the amount of propylene produced per catalyst) is only 481 (g-propylene / kg-cat · h ⁻¹ ) even if all the olefin obtained is propylene. .

In the method of producing propylene from ethanol disclosed in Patent Document 3, the propylene selectivity is as high as 32%, but the STY is only 174 (g-propylene / kg-cat · h ⁻¹ ).

  Therefore, in both methods of Patent Documents 2 and 3, there is a problem that a large amount of zeolite catalyst is required to efficiently produce propylene.

  In addition, when the comparative example in patent document 3 is taken into consideration, when a catalyst that is not modified with a metal is used, a large amount of high-boiling hydrocarbons are generated. Therefore, it is presumed that by modifying the catalyst with a metal, not only the production rate of high-boiling hydrocarbons but also the entire reaction is suppressed, and the production rate of propylene is reduced.

  Therefore, an object of the present invention is to provide a catalyst for efficiently converting ethanol to a lower olefin, particularly propylene, and to provide a method for producing a lower olefin using the catalyst.

  As a result of intensive studies by the present inventors, it has been found that the above-mentioned problems can be solved by a ZSM-5 type zeolite catalyst treated with an alkoxysilane compound.

That is, the present invention includes the following.
(1) A method for producing a lower olefin, comprising converting ethanol into a lower olefin in the presence of a ZSM-5 type zeolite catalyst treated with an alkoxysilane compound.
(2) The production method according to (1), wherein the lower olefin is propylene.
(3) The production method according to (1) or (2), wherein the alkoxysilane compound is tetraethoxysilane.
(4) The production method according to any one of (1) to (3), wherein ethanol is supplied as a mixed gas having an ethanol concentration of 50% or more.
(5) A ZSM-5 type zeolite catalyst treated with an alkoxysilane compound.
(6) The ZSM-5 type zeolite catalyst according to (5), wherein the alkoxysilane compound is tetraethoxysilane.
(7) The ZSM-5 type zeolite catalyst according to (5) or (6), for converting ethanol into a lower olefin.
(8) The ZSM-5 type zeolite catalyst according to (7), wherein the lower olefin is propylene.

  According to the present invention, it is possible to efficiently produce a lower olefin, particularly propylene, from ethanol.

The relationship between ethanol concentration and a propylene yield is shown.

Hereinafter, the present invention will be described in detail.
1. Zeolite Catalyst The zeolite catalyst according to the present invention is a ZSM-5 type zeolite catalyst treated with an alkoxysilane compound.

  The ZSM-5 type zeolite catalyst has pores at the molecular level, and an outer surface acid point (active point) and an inner surface acid point (active point) exist on the outer surface and inner surface of the pore, respectively. . Since the pores have a constant diameter, ethanol can be selectively converted into lower olefins, particularly propylene, at the acid point on the inner surface. On the other hand, since the shape selectivity due to the pores is not exhibited at the acid point on the outer surface, the conversion reaction to a lower olefin hardly proceeds. Therefore, as the ratio of the outer surface to the specific surface area of the catalyst increases, the conversion rate to lower olefins decreases, and a by-product larger than the pore size (for example, a high-boiling product such as a hydrocarbon having 5 or more carbon atoms). Produces a lot.

  Therefore, in the present invention, by deactivating the outer surface acid sites of the ZSM-5 type zeolite catalyst, while maintaining a high reaction rate, the production of by-products is suppressed and the conversion rate to lower olefins is increased. The yield is improved.

  In order to deactivate only the outer surface acid sites without deactivating the inner surface acid sites of the ZSM-5 type zeolite catalyst, an alkoxysilane compound having a molecular size larger than the pore size of the catalyst is used.

As the alkoxysilane compound, the following formula (I):
R ¹ _x -Si-R ² _4-x (I)
[Where
R ¹ is an alkoxy group;
Each R ² is independently hydrogen, an alkyl group, a vinyl group, or an aryl group;
x is an integer of 1 to 4]
It is preferable to use the compound represented by these.

In a preferred embodiment, R ¹ is a C _1-6 alkoxy group, each R ² is independently hydrogen, a C _1-6 alkyl group, a vinyl group, or a phenyl group, and x is an integer of 1-4. It is.

In a more preferred embodiment, R ¹ is a C _1-3 alkoxy group, R ² is each independently hydrogen or a C _1-3 alkyl group, and x is an integer of 1 to 4.

In a particularly preferred embodiment, R ¹ is a C _1-3 alkoxy group and x is 4. Specifically, it is particularly preferable to use tetrapropoxysilane, tetraethoxysilane, or tetramethoxysilane as the alkoxysilane compound.

  The larger the ratio of the outer surface to the specific surface area of the ZSM-5 type zeolite catalyst, the greater the effect when the catalyst is treated with an alkoxysilane compound. Since the proportion of the outer surface increases as the catalyst particle size decreases, the catalyst particle size is preferably 0.05 to 10 μm, and particularly preferably 0.07 to 4 μm. Here, the particle size means an average particle size and can be determined by SEM.

2. Method for Producing Lower Olefin The method for producing a lower olefin according to the present invention comprises converting ethanol into a lower olefin in the presence of a ZSM-5 type zeolite catalyst treated with an alkoxysilane compound. By using a ZSM-5 type zeolite catalyst treated with an alkoxysilane compound, it is possible to efficiently produce a lower olefin from ethanol. The lower olefin is preferably C _1-3 alkylene, more preferably ethylene and / or propylene, and particularly preferably propylene.

  Ethanol may be supplied as it is or as a mixed gas with a dilution gas. The diluent gas is not particularly limited as long as it exists in a gas state under the condition that ethanol is present in a gas state and does not adversely affect the conversion to a lower olefin. For example, an inert gas such as nitrogen or argon can be used.

  When ethanol is supplied as a mixed gas, it is preferably used at a high concentration in view of industrial applicability. Moreover, a high propylene yield can be obtained by using at high concentration. Therefore, the ethanol concentration in the mixed gas is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more.

  The feeding rate of ethanol can be determined based on the activity of the catalyst used. Since the zeolite catalyst in the present invention can convert ethanol into a lower olefin at a high reaction rate, the contact time (W / F) between ethanol and the catalyst is, for example, 0.05 to 5 g-cat · h / mol. Preferably 0.1 to 1 g-cat · h / mol.

  The reaction temperature is not particularly limited as long as ethanol is converted to a lower olefin with high selectivity and a high reaction rate, but is preferably 300 to 700 ° C, particularly preferably 400 to 600 ° C.

  The reaction pressure is not particularly limited as long as ethanol is highly selectively converted into a lower olefin at a high reaction rate, but is preferably 0.01 to 2 MPa, and particularly preferably 0.05 to 1 MPa.

  The conversion from ethanol to lower olefin can be confirmed by analyzing the product gas after the reaction by gas chromatography.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, the technical scope of this invention is not limited to this.

Example 1
1) Catalyst preparation NH ₄ type ZSM-5 (SiO ₂ / Al ₂ O ₃ = 39, manufactured by Tosoh Corporation) was calcined at 550 ° C. for 1 hour in an Air atmosphere to obtain H type ZSM-5.

2) Silylation of acid points on the outer surface (chemical vapor deposition: CVD)
H-type ZSM-5 (2 g) was filled in a fixed-floor quartz tube, fired at 550 ° C. for 1 hour under N ₂ flow of 100 cc / min, and the temperature was lowered to 100 ° C. Tetraethoxysilane (TEOS) was supplied by bubbling with 100 cc / min N ₂ for 3 hours. The supply of tetraethoxysilane was stopped and N ₂ was allowed to flow for 30 minutes. N ₂ was switched to Air and baked at 550 ° C. for 1 hour.

3) Evaluation of ethanol conversion activity Using a fixed bed flow reactor, the ethanol catalytic cracking reaction of the catalyst obtained in 2) was measured. At 773 K so that the total flow rate is 222 ml and the W / F is 0.67 g-cat · h / mol with a mixed gas of ethanol + nitrogen (ethanol concentration 12.5%) for 0.4 g of catalyst. Made contact. The product gas was analyzed by gas chromatography.

Example 2
The same procedure as in Example 1 was performed except that the silylation (CVD) of the outer surface acid sites was repeated twice.

Example 3
The same procedure as in Example 1 was performed except that silylation of the outer surface acid sites was performed as follows.
2) Silylation of acid points on the outer surface (chemical liquid phase growth method: CLD)
900 μl of tetraethoxysilane was dissolved in 20 ml of hexane, 5 g of H-type ZSM-5 was added, and the mixture was stirred at room temperature for 1 hour. Then, it filtered and wash | cleaned with hexane. After drying at 90 ° C. for 1 hour, baking was performed at 550 ° C. for 1 hour in an Air atmosphere.

Example 4
The same procedure as in Example 1 was performed except that the ethanol concentration was 25%.

Example 5
The same procedure as in Example 1 was performed except that the ethanol concentration was 50%.

Example 6
The same procedure as in Example 1 was performed except that the ethanol concentration was 75%.

Example 7
The same operation as in Example 3 was carried out except that the ethanol concentration was 25%.

Example 8
The same operation as in Example 3 was performed except that the ethanol concentration was 50%.

Example 9
The same procedure as in Example 3 was performed except that the ethanol concentration was 75%.

Comparative Example 1
The same procedure as in Example 1 was performed except that the silylation of the outer surface acid sites was not performed.

Comparative Example 2
The same operation as in Comparative Example 1 was carried out except that the ethanol concentration was 25%.

Comparative Example 3
The same operation as in Comparative Example 1 was performed except that the ethanol concentration was 50%.

Comparative Example 4
The same operation as in Comparative Example 1 was performed except that the ethanol concentration was 75%.

Results The results of the above Examples and Comparative Examples are shown in Tables 1 and 2.

By inactivating the outer surface acid sites, the production of BTX (benzene, toluene, and xylene) was suppressed, and the propylene yield was improved. The STY in Example 1 was 1700 (g-propylene / kg-cat · h ⁻¹ ), and a high value was obtained.

Comparative Example 5
The same procedure as in Example 1 was carried out except that diphenylsilane was used instead of tetraethoxysilane and the ethanol concentration was 50%.

result

Claims (6)

A method for producing a lower olefin , comprising converting ethanol to a lower olefin in the presence of a ZSM-5 type zeolite catalyst in which the outer surface acid sites are deactivated with an alkoxysilane compound ,
The production method, wherein the lower olefin is ethylene and / or propylene . The production method according to claim 1, wherein the lower olefin is propylene.   The manufacturing method of Claim 1 or 2 whose alkoxysilane compound is tetraethoxysilane. A ZSM-5 type zeolite catalyst in which the outer surface acid sites are deactivated with an alkoxysilane compound for converting ethanol into a lower olefin ,
A ZSM-5 type zeolite catalyst, wherein the lower olefin is ethylene and / or propylene .   The ZSM-5 type zeolite catalyst according to claim 4, wherein the alkoxysilane compound is tetraethoxysilane. The ZSM-5 type zeolite catalyst according to claim 4 or 5, wherein the lower olefin is propylene.

Images