JPH0321481B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention produces CO by catalytic cracking of methanol.
When producing a mixed gas with _H2 (hereinafter referred to as synthesis gas),
This invention relates to a manufacturing process in which the H ₂ /CO molar ratio in synthesis gas is arbitrarily controlled. Synthesis gas is increasingly used as a feedstock for chemical production based on carbonylation reactions, hydroformyl reactions, and the like. Methods to obtain synthesis gas include using crude oil or petroleum products refined from it as raw materials and partially oxidizing and reforming them, but a production method using catalytic cracking of methanol is seen as promising. ing. This is because methanol can be produced on an extremely large scale in resource-rich locations, is easy to handle and can be transported to long distances without difficulty or danger, and can be brought into contact under relatively mild conditions. This is due to the fact that it can be decomposed. Research has been conducted on the catalytic decomposition of methanol for a long time, and it is known that it can be easily decomposed into CO and H ₂ using catalysts containing copper or zinc. CH ₃ OH→CO＋2H ₂ (1) In the synthesis gas obtained by the decomposition reaction of equation (1),
The theoretical H ₂ /CO molar ratio is 2.0, but in reality side decomposition reactions to carbon, carbon dioxide, methane, etc. occur, so the H ₂ /CO molar ratio can be 2.0 or higher depending on the decomposition conditions. Only certain values can be obtained. However, in general, various types of synthesis gas having a H ₂ /CO molar ratio different from 2 are often required depending on the reaction using the synthesis gas. In such cases, the usual method is to adjust the H ₂ /CO molar ratio by mixing H ₂ or CO gas with synthesis gas obtained by catalytic cracking of methanol, or to use a pressure swing method or membrane separation method. H ₂ or CO in the synthesis gas is separated to obtain synthesis gas with a desired H ₂ /CO molar ratio. All of these methods are complicated to operate and consume a large amount of energy, so they cannot be said to be industrially advantageous. According to the method of the present invention, methanol and/or methyl formate vapor can be easily passed over the catalyst.
Synthesis gas with a H ₂ /CO molar ratio controlled within an arbitrary range can be obtained. That is, in the method of the present invention, the entire amount or a part of the supplied methanol is dehydrogenated in the first reaction zone to convert it into methyl formate, the resulting gas is led to the second reaction zone, and the resulting gas is introduced into the second reaction zone. In a method for thermally decomposing methyl formate or methyl formate and methanol, a part of the produced gas is removed from a first reaction zone and condensable components are returned to a second reaction zone;
By purging non-condensable gases out of the system
This is a method for producing a mixed gas of carbon monoxide and hydrogen from methanol in which the H ₂ /CO molar ratio can be controlled within an arbitrary range. Next, a typical process in the method of the present invention will be explained. In FIG. 1, the reactor is the first,
The first reaction zone contains a catalyst having at least the ability to synthesize methyl formate, and the second reaction zone contains a catalyst capable of decomposing methyl formate and/or
Alternatively, a catalyst capable of decomposing methanol is used. The supplied methanol is sent from a methanol tank 1 by a pump 2, first vaporized in an evaporator '3, and then introduced into a first reaction zone 4. In the first reaction zone 4,
Since it is filled with at least a catalyst capable of synthesizing methyl formate, methyl formate synthesis occurs through the dehydrogenation reaction of methanol as shown in the following formula. 2CH ₃ OH→HCOOCH ₃ +2H ₂ (2) At this time, methanol decomposition reaction (1) often occurs as a side reaction, but this does not impair the essence of the process. The non-condensable gas in the gas produced in the first reaction zone contains a high concentration of H ₂ based on the main reaction of methyl formate synthesis reaction, and depending on the reaction conditions etc., the H ₂ concentration may increase.
It reaches around 97%. The feature of this process is that the H ₂ /CO molar ratio is controlled by purging a portion of this highly concentrated H ₂ -containing gas outside the reaction system (side cut purge). The side cut purge for this purpose is carried out by extracting a part of the generated gas from the first reaction zone 4, cooling it in a cooler '5, and then separating the liquid and gas in a gas-liquid separator '6. The condensed component from which the purge gas has been separated is sent to the inlet of the second reaction zone 9 via the pump 7 and the evaporator 8. On the other hand, the remaining total amount of the generated gas in the first reaction zone 4 is directly led to the second reaction zone 9. Since the second reaction zone 9 is filled with a catalyst capable of decomposing methyl formate and/or methanol, the methyl formate produced in the first reaction zone 4 is
It is decomposed into CO and methanol as shown in equation (3), HCOOCH ₃ →CO+CH ₃ OH (3) and/or a thermal decomposition reaction of methanol into CO and H ₂ occurs as shown in equation (1). The gas at the outlet of the second reaction zone 9 is cooled in a cooler 10, separated into gas and liquid in a gas-liquid separator '11, and then used as synthesis gas. At this time, if necessary, treatments such as removal of organic components or removal of CO ₂ are performed by known methods, and further steps are taken to compress the gas into a higher-pressure synthesis gas. The main component of the condensed component obtained from the separation of the synthesis gas is methanol, which is mixed with the raw material methanol by the pump 12 and can be recycled. Although there are no particular restrictions on the catalyst used in the first reaction zone for dehydrogenating methanol to obtain methyl formate, the following copper-based catalysts are preferably used. That is, for example, a combination catalyst of copper and an element selected from group a or group a of the periodic table (Japanese Patent Publication No. 56-6412), a combination catalyst of copper and an element selected from rare earth elements or actinide group elements (Japanese Patent Publication No. 56-6412), 54-46879), catalysts containing copper, zirconium and zinc, or copper, zirconium, zinc and aluminum (Japanese Patent Publication No. 54-46821), catalysts containing copper and cement (Japanese Patent Publication No. 54-14176)
and a catalyst containing copper, zirconium, and calcium (Japanese Patent Application Laid-Open No. 7741/1983). The H ₂ /CO molar ratio in the synthesis gas can be adjusted by the amount of side cut purge. This side cut purge amount, when expressed as a ratio to the total amount of produced gas exiting from the first reaction zone (hereinafter referred to as purge ratio), can be varied within the range of 0.01 to 0.95. The product gas obtained in the methanol dehydrogenation process is a mixture containing the main products of unreacted methanol, methyl formate and _H2 , and small amounts of CO, _CH4 and _CO2 . In the second reaction zone, the methyl formate and/or methanol in this mixture is catalytically pyrolyzed. Catalysts for this purpose are not particularly limited, but include activated carbon, zeolite itself, a catalyst containing an alkali metal compound or alkaline earth metal compound as an active ingredient and having the ability to decompose methyl formate, and Industrial and Engineering.
Chemistry 21 1052 (1929), Zh.Pricl.Khim.43
362 (1970), Koka Journal 70 1611 (1967), J.Chem.
Copper-based catalysts as reported in Soc. 5248 (1965), Nikka Shi 64 4311 (1942), Koka Shi 54 504 (1951),
Zinc-based catalysts such as those reported in Ind.Eng.Chem.21 1056 (1929), platinum-based, ruthenium-based catalysts, and other known catalysts with methanol decomposition ability are suitable, and these may be used alone or as a mixture. can do. Note that the reactions in the first reaction zone and the second reaction zone are generally carried out in a gas phase in practice. Further, these reactions can be carried out either batchwise or continuously, but the latter is preferred in practical terms. The reaction conditions of the first reaction zone and the second reaction zone may be those employed in a conventional method. In practice, for example, the reaction temperature is preferably 100 to 400°C in the first reaction zone.
The temperature is 150 to 350°C, and in the second reaction zone, the temperature is 100 to 500°C, preferably 200 to 450°C. At temperatures below 100°C, a practically sufficient reaction rate cannot be obtained, and at temperatures exceeding the respective upper limits of 400°C and 500°C, the amount of side decomposition increases. It is also possible to provide the first reaction zone and the second reaction zone in separate reactors and conduct the reaction at different temperatures. In addition, the pressure is preferably 50Kg/cm ² G to reduced pressure.
20Kg/cm ² G ~ under normal pressure, and the space velocity of gas is 50
-5000hr ^-1 preferably 200-20000hr ^-1 . The present invention will be clarified by examples below, but it goes without saying that the present invention can be practiced without being limited to the described matters as long as the essence of the present method is not impaired. Example 1 According to the process shown in Part 1, a Cn-Zn-Zr-Al catalyst was placed in the first reaction zone of the reactor, and activated carbon supporting K ₂ CO ₃ was placed in the second reaction zone. I filled it up and did it. First, methanol is passed through evaporator 3.

[Table] Example 2 The same procedure as in Example 1 was repeated except that the reaction temperature was changed to ₃₁₀ °C. The results were as follows.

[Table] Example 3 After filling the first stage reactor with Cu-cement catalyst and passing 3.20 Kg/hr of methanol vapor under the conditions of 0 Kg/cm ² G, 260°C, and space velocity 3500 hr ^-1 , Cu-
0 by the second stage reactor filled with Zn-Cr catalyst
The decomposition reaction of methanol and methyl formate was carried out under the conditions of Kg/cm ² G, 300° C., and a space velocity of 1800 hr ⁻¹ . A portion of the product gas exiting the first stage reactor was side-cut purged to vary the H ₂ /CO molar ratio. The purge ratio, H ₂ /CO molar ratio, and amount of synthesis gas generated were as follows.

[Table] Example 4 Cu-Zn-Ca (10:1:
1) Catalyst, K ₂ CO ₃ supported activated carbon and ZnO in the second reaction zone
The reaction was carried out in the same manner as in Example 1, except that the mixed catalyst was charged and the reaction temperature was 350°C. The purge ratio, H ₂ /CO molar ratio, and amount of synthesis gas generated were as follows.

【table】 [Brief explanation of the drawing]

FIG. 1 shows an example of a flow sheet for producing a mixed gas of CO and H ₂ according to the present invention.
In Figure 1, 1... Raw methanol tank, 2... Raw methanol supply pump, 3 and 8... Evaporator', 4
...First reaction zone, 5 and 10...Condenser', 6
and 11... gas-liquid separator', 7... side cut recycle pump, 9... second reaction zone, 12...
...Unreacted methanol recycling pump.

Claims (1)

[Claims] 1 In the first reaction zone, the entire amount or a part of the supplied methanol is subjected to a dehydrogenation reaction to convert it into methyl formate, and the resulting product gas is guided to the second reaction zone,
In the method of thermally decomposing methyl formate or methyl formate and methanol in the second reaction zone, the first
From 0.01 to the total amount of gas produced from the reaction zone
A method for producing a mixed gas of carbon monoxide and hydrogen from methanol, characterized by extracting a portion in the range of 0.95 and purging non-condensable gas out of the system.