JPS6228081B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a completely new method that can separate and obtain each of hydrogen and carbon monoxide independently using methanol as a raw material.More specifically, methanol is dehydrogenated using the following equation (i) to obtain hydrogen gas,
This is a method of selectively thermally decomposing the generated methyl formate into methanol and carbon monoxide as shown in equation (ii) to obtain carbon monoxide gas, and if desired, the extracted methanol is subjected to the reaction of equation (i). This is a method for producing hydrogen and carbon monoxide from methanol, which is generally represented by the formula (iii), by circulating the methanol to methanol, and furthermore, it is a method in which each of hydrogen and carbon monoxide is obtained individually using methanol as a raw material. (i) 2CH ₃ OH→HCOOCH ₃ +2H ₂ (ii) HCOOCH ₃ →CO+CH ₃ OH (iii) CH ₃ OH→CO+2H _2Currently , petroleum hydrocarbons or natural Methods of partially oxidizing gas or steam reforming have been adopted, but these raw materials are becoming more expensive due to the recent oil situation, and their supply is unstable, making them undesirable as industrial raw materials. . On the other hand, it is said that in the near future, methanol will be produced in large quantities in oil-producing countries such as the Middle East and will be able to be transported in large quantities to where it is needed at a very low cost. If this happens, it will become possible to use this inexpensive methanol for fuel or various chemical raw materials, but recently, studies have been made regarding the use of this methanol. Examples include methods for producing industrially valuable hydrogen and carbon monoxide mixed gas, hydrogen gas, methane, ethylene, gasoline, acetic acid, and methyl formate from methanol. Among these, methods for producing hydrogen and carbon monoxide mixed gas from methanol include zinc-chromium catalysts [e.g., Ind.Eng.Chem. 21 1056
(1929)], copper-nickel catalysts [e.g., Ind.
Eng.Chem. 40 583 (1948)] is known to be produced by gas phase catalytic cracking by passing methanol vapor upward, but very recently, Japanese Patent Application Publication No. 1983-
No. 25294 also discloses a catalyst in which a combination of group metals and groups - groups of the periodic table is supported on a carrier such as silica or alumina. These are all methods of thermally decomposing methanol to obtain a mixed gas of hydrogen and carbon monoxide. In order to extract pure hydrogen and carbon monoxide from this mixed gas, it is necessary to perform a separation operation such as deep cooling, adsorption, or absorption. These separation operations are very complex and consume a considerable amount of energy. The object of the present invention is to provide a method for independently extracting hydrogen and carbon monoxide from methanol as a raw material without requiring such complicated separation operations. That is, the present invention involves (1) a step of dehydrogenating methanol to produce methyl formate and separating the generated hydrogen gas, and (2) a step of mixing methyl formate and methanol obtained in step (1). A method for decomposing methanol, which includes two steps: treating a substance or methyl formate with a thermal decomposition catalyst and separating the generated carbon monoxide gas, and separating and obtaining hydrogen and carbon monoxide. be. Although there are no particular limitations on the catalyst for dehydrogenating this methanol to obtain methyl formate, the following copper-based catalyst developed by the present inventors is 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 (JP 52-128315), a combination catalyst of copper and an element selected from rare earth elements or actinide group elements ( Catalysts containing copper, zirconium and zinc, or copper, zirconium, zinc and aluminum (Japanese Patent Publication No. 46821, 1983); Catalysts containing copper and cement (Japanese Patent Application No. 1987-46821);
47436) and a catalyst containing copper, zirconium and calcium (Japanese Patent Application No. 1983-83664). Note that this dehydrogenation reaction is generally carried out in a gas phase in practice. Although this reaction can be carried out either batchwise or continuously, the latter is preferred in practice. The reaction conditions for this dehydrogenation reaction may be those employed in conventional methods, such as a reaction temperature of 100 to 400°C, preferably 150 to 350°C,
Space velocity of gas 100-50000hr ^-1 , preferably 500
〜30000hr ^-1 , and the pressure is 50Kg/ ^cm2G〜under reduced pressure,
Preferably it is 20 kg/cm ² G to normal pressure. The product liquid separated into gas and liquid in the methanol dehydrogenation process is a mixed liquid of unreacted methanol and methyl formate. Either this mixed liquid is sent to a methyl formate thermal decomposition process and only ethyl formate is catalytically decomposed, or the methyl formate separated from this mixed liquid by distillation etc. is thermally decomposed. . The catalyst for catalytically thermally decomposing methyl formate is not particularly limited, but activated carbon, zeolite itself, or a catalyst containing an alkaline earth metal compound or an alkali metal compound as an active component is preferably used. That is, the active component of this catalyst may be any alkali metal or alkaline earth metal compound that does not react or reacts poorly with methanol or methyl formate, such as potassium, sodium and lithium, and alkali metals such as magnesium, calcium, etc. or alkaline earth metal oxides, hydroxides, sulfides, halides,
These include inorganic acid salts such as sulfates and carbonates, organic acid salts such as formates and acetates, and alcoholates. Typical compounds include potassium hydroxide, potassium chloride, potassium formate, sodium sulfide, and sodium sulfate. , sodium carbonate, lithium chloride, magnesium oxide, magnesium carbonate and calcium hydroxide. These can be used alone or in mixtures thereof. The decomposition of methyl formate can be carried out either in the gas phase or in the liquid phase, and can be carried out either batchwise or continuously, but the continuous method is preferred. The form of the catalyst varies depending on the reaction method. For example, in the case of a liquid phase, the alkali metal compound or alkaline earth metal compound itself can be dissolved in the raw material mixture to make a homogeneous state, or if it is poorly soluble, it can be charged into a reactor as a slurry and the reaction can be carried out in a batch manner. The reaction is carried out using a continuous reaction method in which a raw material mixture is continuously supplied and reaction products etc. are continuously extracted. Alternatively, the alkali metal compound or alkaline earth metal compound itself or a solid catalyst in which the alkali metal compound or alkaline earth metal compound is supported on a carrier such as silica gel, diatomaceous earth, pumice, brick, or activated carbon may be used in a reactor. A fixed bed continuous method may also be adopted in which only the raw material mixture is continuously supplied and the reaction products are continuously extracted. Among these, the fixed bed continuous method is most preferred in practice. In the case of vaporization, a continuous method is preferred in which magnesia, for example, is used as the alkaline earth metal, and a solid catalyst is used in which magnesia is supported and mixed on alumina, zeolite, or activated carbon. Although the reaction conditions may be any conventional method, for example, the following conditions may be employed. That is, for example, the amount of catalyst used in the thermal decomposition of methyl formate varies depending on its form. That is, when employing a fixed bed continuous method, for example, there is no particular restriction on the amount of catalyst.
If the catalyst is mixed with the raw material mixture or supplied to the reactor at the same time but separately from the raw material mixture to carry out the reaction in a batch or continuous manner, practically 1 mole of methyl formate contained in the raw material mixture. as an alkali metal atom or an alkaline earth metal atom
0.1 to 400 milligram atoms, preferably 0.4 to 100 milligram atoms. If the amount of catalyst used is less than 0.1 milligram atoms of alkali metal or alkaline earth metal atoms per mole of methyl formate, the reaction rate will be slow, and if it exceeds 400 milligram atoms, methanol or There is a risk of side decomposition reactions of acid methyl. When an alkali metal compound is supported on a carrier and used as a solid catalyst, there is no particular restriction on the ratio of the two, but in practice it is 0.05 to 0.05 to 0.05 to 1 gram of alkali metal atom or alkaline earth metal atom per gram of carrier.
3.0 milligram atoms, preferably 0.1-1.5 milligram atoms is sufficient. The content of methyl formate in the mixture of methanol and methyl formate is not particularly limited, but in practice it is usually 10 to 70 wt%, preferably 20 to 60 wt%. When it is less than 10wt%, the yield of carbon monoxide per raw material mixture is low, and when it is higher than 70wt%, the amount of hydrogen generated is greater than when it is less than 70wt%, reducing the purity of carbon monoxide. However, the extent of this is extremely small and does not pose any problem in practice. Therefore, the content of methyl formate can be higher than 70 wt%. Moreover, it is not prohibited to make it less than 10wt%. The temperature is practically in the range of 200-500℃, preferably
It is carried out in the range of 250 to 450°C. At temperatures below 200°C, a practically sufficient reaction rate cannot be obtained, and at temperatures above 500°C, the amount of side decomposition increases, reducing the yield of carbon monoxide and contaminating the generated carbon monoxide. become. In addition, there is no particular limit to the pressure, and of course it can be used under atmospheric pressure.
Surprisingly, sufficient reaction rates are maintained even under high pressures such as atmospheric pressure, and high purity CO is produced. Therefore, when the above reaction conditions are adopted, high-pressure, high-purity carbon monoxide can be obtained without particularly compressing the generated carbon monoxide. The reaction time is 30 seconds to 4 hours in a batch method, particularly preferably 0.1 to 2 hours, and the liquid hourly space velocity (hereinafter referred to as LSVH) in a continuous method is 0.1 to 100, preferably 0.5 to 20. The gas space velocity per hour is 50 to 50,000, preferably 250 to 10,000. Note that methanol produced by thermal decomposition can be reused if desired. Furthermore, by maintaining a high decomposition rate of methyl formate during thermal decomposition, it is also possible to return the liquid after thermal decomposition treatment to the step (1) as it is. The purity of hydrogen and carbon monoxide thus obtained is sufficiently high that they can be used as industrial raw materials as they are, but they can be further purified and used if necessary. In the present invention, it is possible to omit the separation operation for separating hydrogen and carbon monoxide, and hydrogen and carbon monoxide are produced using methanol as a raw material, respectively, and the purity is sufficiently high that it can be used directly as an industrial raw material. The industrial value is extremely large. In order to explain the present invention more specifically, examples will be illustrated with reference to the accompanying drawings. Example 1 First, 6926 g/hr of methanol vapor preheated in the process shown in FIG. 1 was sent to the dehydrogenation tower 1 through line 18. In dehydrogenation tower 1
The reactor was filled with a catalyst having the composition Cu:Zn:Zr:A (10:3:3:1), and was operated at a methanol vapor space velocity of 3500 hr ^-1 , 270°C, and 7.5 Kg/cm ² G. Methyl formate was selectively produced. Methyl formate containing generated hydrogen gas leaving the dehydrogenation tower 1
The methanol mixture was heat exchanged with inlet methanol (line 18) in heat exchanger 5, and then cooled to 20-30°C in cooler 6. The cooled generated hydrogen gas and the reaction product liquid were separated in a gas-liquid separator 2. Here, hydrogen 91.7vol%, carbon monoxide 8.3vol%
% composition of generated gas is 2133/hr and methyl formate 32.8wt% and methanol 67.2wt% liquid composition is 6529/hr.
g/hr was extracted. Next, the mixed liquid of methyl formate and methanol taken out here is directly transferred to the evaporator 9.
was sent to cracking tower 3 through The decomposer 3 is filled with a solid catalyst in which 10 wt% of potassium chloride is supported on activated carbon, and here the vapor space velocity is 5000 hr ^-1 ,
It was operated at 300°C and 30Kg/cm ² G. Decomposition tower 3
The reaction product passed through the heat exchanger 7 and was cooled to 20 to 30°C in the cooler 8, and then passed through the gas-liquid separator 4 to 98.0 vol% carbon monoxide, 1.0 vol% hydrogen, and methane.
Gas 816 with a composition of 0.5vol% and carbon dioxide 0.5vol%
/hr and methanol 5518g/hr were separated.
The methanol taken out here is preheated through the evaporator 7 and the heat exchanger 5 together with 1408/hr of methanol newly supplied from the line 11, and sent to the dehydrogenation tower 1, where it is not used again to produce methyl formate. Ta. Example 2 In the process shown in FIG. 2, 7620 g/hr of preheated methanol vapor was sent to dehydrogenation column 1 through line 20. Dehydrogenation tower 1 contains Cu:
A solid catalyst with a composition of Zn:Zr (10:3:3) is packed, and here the methanol vapor space velocity is
The reaction was carried out under the conditions of 2200 hr ⁻¹ , 265° C., and 10 Kg/cm ² G, and methyl formate was selectively produced. The methanol-methyl formate mixture containing generated hydrogen gas leaving the dehydrogenation tower 1 is heat exchanged with the inlet methanol (line 20) in the heat exchanger 6, and is heated to 20 to 30 methanol in the cooler 7.
cooled to ℃. The cooled generated hydrogen gas and the reaction product liquid were separated in a gas-liquid separator 2. Here, the generated gas has a composition of 95.5 vol% hydrogen and 4.5 vol% carbon monoxide.
1853 g/hr and 7357 g/hr of a liquid having a composition of 29.1 wt% methyl formate and 70.9 wt% methanol were obtained. Next, the mixed liquid of methyl formate and methanol taken out here was sent to a distillation column 3, where methyl formate and methanol were separated by distillation. 99.0wt% methyl formate and methanol distilled from the top of distillation column 3
2166 g/hr of liquid having a composition of 1.0 wt% was sent to the decomposition column 4 via the evaporator 10. Here, bricks are filled with a solid catalyst with 20wt% of sodium carbonate supported, and the vapor space velocity of methyl formate is 3500hr ^-1 , 320
The operation was carried out at 100 Kg/cm ² G at ℃. The reaction product leaving the decomposition tower passed through a heat exchanger 8 and was cooled by a cooler 9. Carbon monoxide 97.0vol in gas-liquid separator 5
%, hydrogen 2.5vol%, methane 0.25vol%, carbon dioxide
Gas of 0.25vol% composition 808/hr and methanol 1150
g/hr was separated. This methanol and line 1
1,279 g/hr of methanol freshly supplied from distillation column 1 and 5,191 g/hr of methanol taken out from the bottom of distillation column 3 and passed through line 15 are preheated through heat exchanger 8 and heat exchanger 6, and then heated to dehydrogenation column 1. The dehydrogenation reaction was repeated. Examples 3-4 The same process as in Example 1 was carried out with different catalysts and reaction conditions. Table 1 shows the type of catalyst, reaction conditions, and results.

【table】

[Table] Examples 5 to 7 In the same process as Example 2, the catalyst and reaction conditions were changed. The type of catalyst, reaction conditions, results, etc. are shown in Table 2.

【table】

【table】 [Brief explanation of the drawing]

1 and 2 are exemplary flow sheets of processes for carrying out the present invention. In FIG. 1, 1... dehydrogenation column, 2... gas-liquid separator, 3... decomposition column, 4... gas-liquid separator, 5... heat exchanger, 6... cooler, 7... evaporator, 8... cooler, and 9... …Evaporator. In FIG. 2, 1... dehydrogenation column, 2... gas-liquid separator, 3... distillation column, 4... decomposition column,
5... Gas-liquid separator, 6... Heat exchanger, 7... Cooler,
8... Heat exchanger, 9... Cooler and 10... Evaporator.

Claims (1)

[Claims] 1. Steps of dehydrogenating methanol to generate methyl formate and separating the generated hydrogen gas, and (2)(1)
The process includes two steps: treating the mixture of methyl formate and methanol obtained in step 1 or methyl formate with a thermal decomposition catalyst and separating the generated carbon monoxide gas. A method for decomposing methanol, characterized by separating and obtaining it.