JP7538593B2 - Ethylene production catalyst - Google Patents

Description

The present invention relates to a catalyst for producing ethylene that is suitable for producing ethylene by a dehydrogenation reaction using ethane as a raw material, and in particular to a new catalyst for producing ethylene that contains a metal ion-exchanged zeolite carrying a specific combination of metals, and a method for producing ethylene using the same.

Ethylene is a useful chemical raw material, and much of it is obtained by cracking naphtha and other feedstock oils in a thermal cracking reactor and separating ethylene from the resulting thermal cracking products. With this method, ethylene is only one of many thermal cracking products, and there are issues with low reaction selectivity and the need for a high reaction temperature of around 800°C.

Alternative methods that have been proposed include a catalyst for producing ethylene using an oxide containing Sn and W as a catalyst (see, for example, Patent Document 1); a method for producing unsaturated hydrocarbons in the presence of a catalyst in which zinc and a Group VIIIA metal are supported on a zeolite carrier in contact with an alkali metal hydroxide, an alkaline earth metal hydroxide, or the like (see, for example, Patent Document 2); and a method for producing lower alkenes in the presence of a catalyst using ZSM-5 zeolite as a catalyst carrier (see, for example, Patent Document 3).

Furthermore, ethylene is produced by a thermal cracking process using ethane obtained from shale gas and associated petroleum gas as a raw material. However, this process also has the problem of requiring a high reaction temperature of about 800°C or more.

Japanese Patent Application Publication No. 09-0368490 JP 2013-163647 A JP 2008-266286 A

However, the catalyst described in Patent Document 1 uses a special oxide called Sn-W oxide as a catalyst, and the ethylene conversion rate is problematic. In addition, in the method described in Patent Document 2, the production of unsaturated hydrocarbons is observed to some extent, but the efficiency is problematic, and no consideration is given to the production of ethylene, which is difficult to produce. Furthermore, in the production method described in Patent Document 3, the production of ethylene is confirmed, but a chromium-based catalyst is described that has problems with its use, and the operating temperature is relatively high, which also has problems.

Therefore, the present invention aims to provide a new catalyst for ethylene production that can produce ethylene under milder reaction conditions using ethane as a raw material.

As a result of intensive research into solving the above problems, the present inventors have found that by using a catalyst containing a zeolite into which a specific combination of metals has been introduced by ion exchange, it is possible to efficiently produce ethylene from ethane as a raw material under milder reaction temperature conditions, and have thus completed the present invention.
That is, the present invention relates to a catalyst for producing ethylene, which comprises a metal ion-exchanged zeolite having zinc and an alkali metal supported thereon.
The present invention also relates to a process for producing ethylene, which comprises carrying out a dehydrogenation reaction of ethane in the presence of the catalyst for producing ethylene at a temperature in the range of 500°C to 700°C.

The present invention relates to a new catalyst that can efficiently produce ethylene under milder reaction conditions using ethane as a raw material, and is extremely useful industrially.

One embodiment of the present invention will be described in detail below.
The catalyst for ethylene production according to the present embodiment includes a zeolite in which a metal is supported by ion exchange (metal ion-exchanged zeolite), and zinc and an alkali metal are supported in the zeolite. The zeolite may be any zeolite that belongs to the category called zeolite, such as AEI, BEA, CHA, CON, EPI, ERI, EUO, FAU, FER, LAU, LEV, LTA, MEL, MFI, MOR, MSE, MTW, MWW, PON, UTL, or ZON. Among them, MFI type zeolite such as ZSM-5 type zeolite (more preferably ZSM-5 type zeolite) is preferable, since it is a catalyst that exhibits high efficiency under milder temperature conditions, particularly when producing ethylene from ethane. The MFI type is a type belonging to the structure code MFI defined by the International Zeolite Society, and the ZSM-5 type zeolite is preferably a ZSM-5 type aluminosilicate compound.
The structure of the zeolite according to this embodiment can be identified by powder X-ray diffraction.

In this specification, zinc and an alkali metal are supported on a zeolite means that zinc and an alkali metal are bonded to each other at ion exchange sites (cation sites) of the zeolite.
The zinc and alkali metal can be supported on the zeolite by, for example, subjecting the zeolite to an ion exchange treatment. The ion exchange treatment can be carried out by, for example, a known method, and is not particularly limited.
The ion exchange rate of zinc in the metal ion-exchanged zeolite according to this embodiment is not limited, but is preferably within the range of 3 to 80% since it will show higher efficiency when forming a catalyst for ethylene production. Furthermore, it is preferable that the cationic sites not exchanged with zinc are ion-exchanged with an alkali metal. The alkali metal may be any alkali metal as long as it belongs to the alkali metals, but is preferably one or more of sodium, potassium and cesium since it will show higher efficiency as a catalyst for ethylene production. Moreover, the ion exchange rate of the alkali metal is preferably within the range of 97 to 20% since it will show higher efficiency when forming a catalyst for ethylene production.
In order to exhibit even better efficiency as a catalyst for ethylene production, when the alkali metal is sodium, the ion exchange rate of zinc is more preferably 15 to 40%.

In this specification, the ion exchange rate of zinc or alkali metal refers to the rate at which cations on the ion exchange sites in the zeolite are replaced with zinc ions or alkali metal ions.
Specifically, the ion exchange rate can be calculated by the formula: (number of zinc ion or alkali metal ion atoms)×(valence of zinc ion or alkali metal ion)/(number of ion exchange sites in zeolite)×100.
The ion exchange rate can be adjusted to a desired value by adjusting the amount of zinc ions or alkali metal ions supported on the ion exchange sites in the zeolite, for example by adjusting the concentration of the solution used in the ion exchange treatment.

The SiO ₂ /Al ₂ O ₃ (molar ratio) of the zeolite, particularly the ZSM-5 type zeolite, is not limited, and in particular, since it will be a catalyst excellent in heat resistance, reaction selectivity, and productivity, the SiO ₂ /Al ₂ O ₃ (molar ratio) is preferably 20 or more and 100 or less. In order to provide excellent reaction selectivity and productivity, it is preferable that the zeolite does not contain an organic structure directing agent in the pores. Furthermore, there is no limitation on the primary particle size and agglomeration size of the zeolite.

The form of the catalyst for ethylene production in this embodiment may be any form that contains the metal ion-exchanged zeolite. For example, the prepared metal ion-exchanged zeolite powder may be used as a catalyst as is, or may be used after being given a specific shape by compression molding or the like, or may be used after being mixed with a binder or the like and molded to give a specific shape.

The catalyst for ethylene production of this embodiment can efficiently produce ethylene by contacting ethane in the presence of the catalyst to carry out a dehydrogenation reaction, and can efficiently produce ethylene under milder temperature conditions, even in the dehydrogenation reaction of ethane, which is considered difficult to proceed with. The temperature conditions are preferably 500°C or higher and lower than 700°C, since this provides a higher conversion efficiency to ethylene and makes it possible to suppress deactivation of the catalyst. In addition, any pressure conditions can be selected.

The supply of ethane when producing ethylene is arbitrary, and there is no particular restriction on the ratio of catalyst weight to the flow rate of the raw material gas (ethane), and it can be supplied at a space velocity of about 0.01 to 1000 (min·g-catalyst/L-raw material gas), for example. When supplying ethane as the raw material gas, it is also possible to use ethane alone, a mixed gas, or ethane diluted with an inert gas such as nitrogen.

In addition, there are no limitations on the reaction type when producing ethylene, and any type can be used, such as a fixed bed, transport bed, fluidized bed, moving bed, multi-tubular reactor, continuous flow type, intermittent flow type, swing type reactor, etc.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.
The zeolite (ZSM-5) used in the examples was evaluated and measured by the following methods.

Measurement of SiO ₂ /Al ₂ O ₃ molar ratio and zinc and alkali metal ion exchange rates
Zeolite was dissolved in a mixed aqueous solution of hydrofluoric acid and nitric acid, and the solution was observed and measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) using an ICP device ((trade name) OPTIMA3300DV, manufactured by PerkinElmer). Based on the measurement results, the ion exchange rates (%) of zinc and alkali metals were calculated using the above formula.

~ Powder X-ray diffraction measurement ~
Measurements were performed in air using an X-ray diffraction measurement device (Spectris Corporation, product name: X'pert PRO MPD) with a tube voltage of 45 kV and a tube current of 40 mA using CuKα1. The range of 5 to 60 degrees was analyzed at 0.04 degree/step and 4 degrees/min. In addition, background correction based on the absorption rate of the direct beam was removed.

- Ethylene production equipment and its manufacturing method -
Ethylene was produced by the following method and evaluated.
A fixed-bed gas-phase flow-type reactor using a quartz reaction tube (inner diameter 7 mm, length 400 mm) was used. The middle part of the quartz reaction tube was filled with a catalyst for ethylene production, and after performing a heating pretreatment under nitrogen flow, ethane (raw material gas) was fed. A ceramic tubular furnace was used for heating, and the temperature of the catalyst layer was controlled. The reaction outlet gas and reaction liquid were collected, and the gas components and liquid components were analyzed individually using a gas chromatograph. Hydrogen was analyzed using a gas chromatograph equipped with a TCD detector (Shimadzu Corporation, (trade name) GC-8A). The packing material used was Unibeads 1S 60/80 (trade name) manufactured by GL Science Corporation or Sunpack A (trade name) manufactured by Shinwa Kako Co., Ltd. Other gas and liquid components were analyzed using a gas chromatograph equipped with an FID detector (Shimadzu Corporation, (trade name) GC-2025). A capillary column PoraPLOT Q (trade name) manufactured by Agilent Technologies was used as the separation column.

The reaction conditions were set as follows:
(Ethylene production conditions)
Flowing gas: mixed gas of ethane gas 6 mL/min + nitrogen 14 mL/min. Catalyst weight: 60 mg.
Catalyst shape: Zeolite powder passed through a 100 mesh sieve was used.
Pressure: 0 MPaG.
(Catalyst pretreatment conditions)
Catalyst temperature: 550°C.
Flow gas: nitrogen 14 ml/min.
Pressure: 0 MPaG.

Example 1
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 9.5 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, and a series of operations including solid-liquid separation by centrifugation and thorough washing of the solid with pure water were repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 9%, and the sodium ion-exchange rate was 91%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 2
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 19.5 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, and a series of operations including solid-liquid separation by centrifugation and thorough washing of the solid with pure water were repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 25% and the sodium ion-exchange rate was 75%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 3
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 28.1 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 28%, and the sodium ion-exchange rate was 72%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 4
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 46.8 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 52%, and the sodium ion-exchange rate was 48%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 5
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 2.12 g of cesium chloride in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours to obtain cesium-type ZSM-5 zeolite. The cesium ion exchange rate of the cesium-type ZSM-5 zeolite was 100%.
A solution was prepared by dissolving 11.7 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.3 g of the above cesium ion-exchanged ZSM-5 zeolite was dispersed in the above solution, heated to 85° C. and stirred for 24 hours, followed by solid-liquid separation by centrifugation and thorough washing of the solid with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100° C. for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 5%, and the cesium ion-exchange rate was 95%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 6
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 2.12 g of cesium chloride in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours to obtain cesium-type ZSM-5 zeolite. The cesium ion exchange rate of the cesium-type ZSM-5 zeolite was 100%.
A solution was prepared by dissolving 22.8 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.3 g of the above cesium-type ZSM-5 zeolite was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 6%, and the cesium ion exchange rate was 94%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

Example 7
The metal ion-exchanged zeolite was prepared as follows. A solution was prepared by dissolving 2.12 g of cesium chloride in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours to obtain cesium-type ZSM-5 zeolite. The cesium ion exchange rate of the cesium-type ZSM-5 zeolite was 100%.
A solution was prepared by dissolving 46.8 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 100 mL of pure water. 0.3 g of the above cesium ion-exchanged ZSM-5 zeolite was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion-exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 8% and the cesium ion-exchange rate was 92%. The metal ion-exchanged ZSM-5 zeolite was used as a catalyst for ethylene production.

Then, in the presence of the ethylene production catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

<Comparative Example 1>
Sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio=23.8) was used as the catalyst.
Then, in the presence of this catalyst, an attempt was made to produce ethylene using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

<Comparative Example 2>
Zeolite was prepared as follows. 56,200 mg of zinc nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 100 mL of pure water to prepare a solution. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85°C and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100°C for 12 hours. The zinc ion exchange rate of the obtained metal ion-exchanged ZSM-5 zeolite was 100%. The ZSM-5 zeolite was used as a catalyst.

Then, in the presence of this catalyst, ethylene was produced using ethane as a raw material under the above-mentioned conditions at a reaction temperature of 550°C.

<Comparative Example 3>
Zeolite was prepared as follows. A solution was prepared by dissolving 2.12 g of cesium chloride in 100 mL of pure water. 0.5 g of sodium ion-exchanged ZSM-5 zeolite (manufactured by Tosoh Corporation, (product name) HSZ-820NAA, SiO ₂ /Al ₂ O ₃ molar ratio = 23.8) was dispersed in the above solution, heated to 85 ° C. and stirred for 24 hours, solid-liquid separation by centrifugation, and the solid was thoroughly washed with pure water. This series of operations was repeated three times, and the obtained solid was dried at 100 ° C. for 12 hours to obtain cesium ion-exchanged ZSM-5. The cesium ion exchange rate of the cesium type ZSM-5 zeolite was 100%. The cesium ion-exchanged ZSM-5 zeolite was used as a catalyst.

Then, in the presence of this catalyst, we attempted to produce ethylene using ethane as a raw material under the above conditions at a reaction temperature of 550°C.

Table 1 shows the reaction time, ethane conversion, and ethylene yield in the above-mentioned ethylene production using the catalysts of the Examples and Comparative Examples.
When the catalysts of Comparative Examples 1 and 3 were used, no ethylene production was observed, and it is difficult to say that the catalyst or production method is efficient. Also, when the catalyst of Comparative Example 2 was used, the ethylene yield was low, and it is difficult to say that the catalyst or production method is efficient.
On the other hand, when the catalysts of the Examples were used, ethylene could be produced at a higher yield for a longer period of time as compared with the Comparative Examples, resulting in efficient ethylene production.

The catalyst for producing ethylene of the present invention enables ethylene to be produced efficiently under milder conditions and is therefore extremely useful industrially.

Claims (5)

a metal ion-exchanged zeolite having zinc and an alkali metal bound at its ion-exchange sites;
The catalyst for producing ethylene by the dehydrogenation of ethane is characterized in that the zinc ion-exchange rate in the metal ion-exchanged zeolite is 5 to 52% , and the alkali metal ion-exchange rate is 48 to 95%. The catalyst for ethylene production according to claim 1, characterized in that the metal ion-exchanged zeolite is a ZSM-5 type zeolite. 3. The catalyst for producing ethylene according to claim 1, wherein the alkali metal is at least one of sodium, potassium and cesium. The catalyst for use in the production of ethylene according to any one of claims 1 to 3 , wherein the alkali metal is cesium. A method for producing ethylene, comprising carrying out a dehydrogenation reaction of ethane at a temperature in the range of 500° C. to 700° C. in the presence of the catalyst for producing ethylene according to any one of claims 1 to 4 .