JPS6243921B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing gas from methanol. The use of methanol as a raw material for hydrogen production is
The method is well described in the literature and patents. This method was clearly disadvantageous in the past, especially from an economic point of view, but it has become difficult to obtain hydrocarbons, and the conversion of other raw materials to methanol (coal gasification) will likely occur in the future. is trying to turn this situation to its advantage. The purpose of the present invention is to significantly improve the existing technology in order to optimally use methanol as a starting hydrocarbon for the production of gases of various compositions.
It's about adapting. Whether by cracking or steam reforming, methanol decomposition produces gases with widely varying compositions, the composition of which is determined primarily by the appropriate choice of catalyst and operating conditions. be done. In this preface, it is only noted that for hydrogen production, steam reforming of methanol is preferred over cracking, since a portion of the water introduced is converted to hydrogen. It is also clear that if low temperatures are to be used, it will be necessary to use catalysts that have no activity for methanation reactions. The various reactions in this reaction system can be described as follows. Cracking reaction of methanol CH ₃ OHCO+2H ₂ Steam reforming reaction of methanol CH ₃ OH+H ₂ OCO ₂ +3H ₂ (2) Water gas reaction for carbon monoxide conversion CO+H ₂ OCO ₂ +H ₂ Carbon monoxide conversion reaction CO+3H ₂ CH ₄ +H ₂ O (4) CO ₂ +4H ₂ CH ₄ +2H ₂ O (5) The equilibrium constants for these reactions are as follows.

[Table] Looking at these numbers and considering the stoichiometry of this reaction system, the following points can be found. Reaction (2) has higher hydrogen productivity than reaction (1). Reaction (3) can be used to increase the amount of hydrogen produced,
In fact, reaction (2) is the addition of reactions (1) and (3). Reactions (4) and (5) are extremely advantageous in terms of equilibrium at low temperatures and tend to occur, but the presence of water suppresses the production of methane. According to the literature, the catalyst used to promote reaction (2) is often the same as the catalyst used for reaction (3). The reason for this is that when reaction (3) occurs, CO disappears, so reaction (1) is promoted. The present invention uses methanol vapor, water vapor that may not be added, and carbon dioxide that may be added.
1-100 in the presence of a catalyst at a temperature of 130-950℃
In a process for producing gases which react at atmospheric pressure and contain varying concentrations of hydrogen and carbon monoxide, with the remainder being carbon dioxide and the presence of methane, water vapor and methanol, the Steam containing a small amount of methanol is passed through a reactor containing an unreduced or unreduced catalyst, the amount of methanol is gradually increased until a normal composition is reached, and the operation is carried out above the dew point.
This is a method for producing gas from methanol, which is characterized in that it is carried out at a temperature of 400° C. or lower and a pressure of 1 to 100 atmospheres, thereby eliminating the need for catalyst reduction before the start of operation. As catalysts for promoting methanol cracking reaction and steam reforming reaction, transition metal catalysts, Cu catalysts, and catalysts made of Zn, Ni or Fe chromite are known, but the catalyst used in the method of the present invention Of these catalysts, catalysts containing zinc and chromium as main components and catalysts containing nickel and chromium as main components are particularly desirable. Pt, Pd for these catalysts,
Addition of platinum-based noble metals such as Rh, Cu, Co, Mn, Mg, Mo, etc. is desirable because it brings about effects such as improvement of activity, and among these, addition of Cu is particularly desirable because it significantly improves low-temperature activity. The method of the present invention for producing hydrogen or a gas containing hydrogen and carbon monoxide as main components is carried out using one or more of the catalysts mentioned above. In addition, the gas obtained as a result of this implementation can be carried out in accordance with known techniques by combining reactions to convert it into gases of different compositions using a known catalyst (not a single catalyst but multiple catalysts may be used). is voluntary. Here, the term "different compositions" includes not only gases having different ratios of hydrogen and carbon monoxide, but also gases containing hydrocarbons produced by a reaction between hydrogen and carbon monoxide. If two or more catalysts and/or known catalysts are used in combination in the process of the invention, these catalysts may be accommodated in one reactor in sequence depending on the composition of the required product gas or depending on the thermal balance. Alternatively, the reactors may be individually housed in two or more reactors. The invention will now be explained in more detail by way of example. Example 1 (Reference Example 1) A classical low-temperature conversion catalyst with the composition CUO 44% by weight ZnO 45 〃 Al ₂ O ₃ 11 〃 was selected,
A cylindrical reactor with an inner diameter of 5 cm was filled with 550 cm ² of this catalyst, and the height of the catalyst bed was set to 25 cm. A preheating zone with a height of 40 cm filled with an inert material was provided in front of the catalyst filling section. The catalyst was reduced with a gas mixture containing 2% H ₂ in N ₂ at 200° C. for 12 hours. The average temperature of this catalyst was then raised to 295 °C and the _H2O vs. _CH3OH
The liquid mixture with a molar ratio of 5 was pumped into a preheater at normal pressure. The space velocity (VVH) of the gas flow entering the catalyst bed is
It was set to 900h ^-1 . Outlet gas composition is shown in volume %
CO0.45%, _CO2 23.56%, _H2 75.76%,
CH ₃ OH 0.02%, remaining inert. The condensed liquid contained 0.10% by weight CH ₃ OH.
These analytical results were equivalent to 70 hours of operation. Nevertheless, this good conversion could only be maintained by rapidly increasing the temperature. After 214 hours, the average temperature of the reactor was 307° C. and the liquor already contained 1.11% CH ₃ OH without changing the composition and flow rate at the inlet. Finally, after 492 hours, with an average temperature of 350℃, the condensate is 1.00
Contains wt% CH ₃ OH, average temperature after 690 hours
At 350 °C, the condensate contained 5.65% CH ₃ OH. Example 2 (Reference Example 2) Another catalyst was similarly tested under the same conditions as in column 1. The catalyst composition was as follows. ZnO 71% by weight Cr ₂ O ₃ 22 Al ₂ O ₃ 7 In order to obtain the same conversion as in Example 1, higher temperatures were required for this catalyst. For example, after 96 hours of operation, the condensate is 0.07% by weight.
Although containing CH ₃ OH, the average temperature of the catalyst in the reactor was 334°C. However, this catalyst showed better stability as a function of time than the catalyst of Example 1. That is, after 478 hours of operation, the average temperature was 349°C, and the CH ₃ OH in the condensate was 0.84%, and after 831 hours of operation, the average temperature was 350°C, and the CH ₃ OH in the condensate was 0.53% by weight. Ta. Example 3 (Reference Example 3) The low-temperature conversion catalyst with the classical composition of Example 1 is not suitable, and the elements of zinc and chromium in Example 2 have catalytic properties themselves and are stable over long periods of operation. Considering that the temperature is higher than that of the classical catalyst, another catalyst was prepared with the following composition: ZnO 57% by weight Cr ₂ O ₃ 11 CUO 21 Al ₂ O ₃ 11 This catalyst was tested as in Examples 1 and 2.
After 144 hours of operation, the average temperature of the catalyst in the reactor is 311
℃, no CH ₃ OH was detected in the condensate.
This catalyst was then tested under increasingly severe test conditions: high pressure, low H ₂ O to CH ₃ OH molar ratio.
i.e. pressure 30.3 atmospheres (30 bar) vs. H ₂ O
After operating for 311 hours at a CH ₃ OH molar ratio of 1.5, the average catalyst temperature in the reactor was 332°C, and there was very little CH ₃ OH in the condensate.
It was 0.25% by weight. Finally, after 3444 hours of operation at a pressure of 24.3 atm (24 bar) and a H ₂ O to CH ₃ OH molar ratio of 2.5, with an average catalyst temperature in the reactor of 349 °C,
CH ₃ OH was only 0.83% by weight. After examining Examples 1 to 3, it was found that the main elements in the catalyst were zinc, copper and chromium, and that addition of copper enabled operation at much lower temperatures. However, the drawback remained that the mixture of H ₂ O and CH ₃ OH had to be passed through the reduction phase of the catalyst. Obtaining this reduced phase requires reduction using hydrogen in the gas stream or the use of a pre-reduced catalyst (reduced outside the unit before commissioning (pre-reused)), which is discussed in the manual. becomes even more difficult. The present invention has a start-up method that overcomes this drawback and also provides the catalyst of Example 3 with increased low temperature activity. Example 4 (Example 1) The catalyst of Example 3 was charged into the same reactor as Example 3 and the temperature was fixed at 200°C. without reducing the catalyst.
The CH ₃ OH 1% aqueous solution stream was pumped into a preheater at atmospheric pressure. After 20 hours, pump _CH3OH aqueous solution _CH3OH
The content was increased to 2% and after 40 hours to 8%. In this way, the CH ₃ OH concentration was gradually increased until the system reached the conditions of Examples 1, 2 and 3. Thus,
After 192 hours of operation at a pressure of 24.3 atmospheres (20 bar) and a molar ratio of H ₂ O to CH ₃ OH of 2.5, with an average catalyst temperature in the reactor of 268° C., CH ₃ OH in the condensate was 0.89% by weight. . This good activity was maintained after 1665 hours of operation, at 24.3 atmospheres (24 bar), _H2O to _CH3OH molar ratio
1.9, the average catalyst temperature in the reactor was 293° C., and the CH ₃ OH in the condensate was only 0.52% by weight. In Examples 1 to 4, the gas produced was always relatively constant, corresponding to reaction (2), producing 3 parts H ₂ for every 1 part CO ₂ . CO content and methane content were low. Although the gas after removal of the CO ₂ by known methods was essentially pure hydrogen, it is possible to choose other catalysts, or choose other reaction conditions or other feedstocks even with the catalysts of Examples 3 or 4. In particular, it was possible to arrive at different compositions. It becomes possible to change the gas composition thus obtained. Example 5 (Example 2) A reactor was charged with the catalyst described in Example 3 and operated according to the process of the invention described in Example 4. After this initial stage, the following conditions were operated and the results shown in Table 1 below were obtained.

【table】

[Table] Example 6 (Example 3) A reactor was charged with a catalyst having the following composition. NiO 14% by weight Al ₂ O ₃ 86 〃 Operated as described in Example 4, steam reforming and cracking reactions of methanol were carried out at a reactor outlet temperature of approximately 800°C and a temperature of the mixture entering the reaction zone of 400°C. I did it. CO ₂ was added to the inlet gas to shift the equilibrium in favor of CO production. The results of the test are shown in Table 2 below.

[Table] The process described in the present invention is particularly advantageous in combination with a purification process using molecular sheep. This well-known purification process, when combined with methanol steam reforming, not only produces extremely pure hydrogen, but also allows the exhaust gas from this purification process to be used directly to generate the total heat required for the steam reforming process. This is advantageous because it can be used to supply Therefore, in one aspect of the present invention, the heat for the steam reforming process is self-sufficient by providing a combination of a methanol reforming process and a refining process using a molecular sieve in a hydrogen production process apparatus. Example 7 (Example 4) A methanol steam reforming reaction was carried out in the apparatus shown in FIG. The mass balance and heat balance showed that the reaction system was self-sufficient in heat. The selected operating conditions were: H ₂ O to CH ₃ OH molar ratio of 2, outlet temperature of 300°C, and pressure of 25.3 atm (25 bar).
It was hot. The device was designed to produce 250 Nm ³ /h of purified pure hydrogen. Using a hydrogen recovery rate of 72%, which is a typical value for a purification process using molecular sieves, 347 Nm ³ /h of H ₂ would be required at the reactor outlet to produce this amount of pure hydrogen. did. Using the reactor outlet gas analysis value obtained in Example 5, Example 5
Using the same operating conditions as above, the material balance calculation shows that methanol is charged at inlet 1 of this equipment at a charging rate of 172 kg/hour, H ₂ O at inlet 2 is charged at a rate of 193 kg/hour, and a temperature of 25°C is calculated. It was necessary to charge at a certain temperature. No _CO2 was added to the reactor. Leaving the reactor at outlet 10 at 300°C and 25.3 atm (25
The volumetric composition of the wet gas is
CO1.33%, _CO2 18.55%, _H2 58.14%, _CH4 0.078
%, CH ₃ OH 0.157% and H ₂ O2 1.753%, and the flow rate was 597 Nm ³ /h. To heat the feed mixture to its boiling point of 203°C, it is necessary to supply 55,600 Kcal/h, and for evaporation it is necessary to supply a further 111,400 Kcal/h to superheat it to 300°C. In order to do this, it was necessary to supply an additional 15,200 Kcal/hour of heat, and a total of 182,200 Kcal/hour of heat needed to be supplied from the inlet of the reactor 5 to the outlet 10. The heat of reaction that had to be supplied to obtain a specific conversion with this flow of fluid mass was 79,300 Kcal/hr. Therefore, the total amount of heat that must be supplied is
It was 261,500Kcal/hour. The wet gas leaving reactor 5 is condensed
A quantity of heat of 61800 Kcal/hour was supplied to heat exchanger 3, which achieved heating and partial evaporation of the liquid feedstock and the temperature of the liquid feedstock increased from 25°C.
The temperature was raised to 203℃. The wet gas product is transferred to heat exchanger 3
After entering at 300℃ and exiting at 132℃, it is heated to 35℃ in condenser 6.
After being cooled to , it entered purification step 11. Although an additional 51,200 Kcal/hour of heat was removed from the condenser 6, the process shown in FIG. 1 merely shows an example in which this heat is utilized by cooling water discharged from the discharge pipe 12 at 37°C. The reaction mixture leaving the heat exchanger has an additional 120,400 Kcal/hr to reach the reaction conditions and 79,300 Kcal/hr for the reaction itself, thus total
It was necessary to supply 1,997,000 Kcal/hour of heat. This extra heat was provided by passing the exhaust gas from the refining process 11 via line 13 through storage drum 7 into combustion furnace 8, where it was combusted. Exhaust gas is H ₂ 44.5%, CO 3.6%, CH ₄ +
It had a composition of 0.5% CH ₃ OH, 50.8% CO ₂ , and 0.5% H ₂ O, and was able to supply 285,400 Kcal/hour by heating. Assuming that the gas temperature at the exit of the flue 9 is 300° C., the amount of heat recovered by this heat transfer fluid was 233,500 Kcal/hour, and ultimately an excess amount of heat of 33,800 Kcal/hour remained. This heat transfer fluid supplied the required amount of heat to the reaction mixture in evaporator 4 and reactor 5. Therefore, this process equipment had a surplus heat amount of 13% in terms of heat balance. Example 8 (Example 5) A test was conducted in the same manner as in Example 6 using a catalyst having the following composition. NiO 12% Cr ₂ O ₃ 8% Al ₂ O ₃ 80% As in Example 6, the feed gas was introduced into the reaction zone at 400°C. _CO2 was added to increase CO production. The results were as shown in Table 3 below.

[Table] Although the present invention has been described above with reference to specific examples and numerical values, the present invention is not limited thereto, and various modifications and changes can be made without departing from the broad spirit and scope of the present invention. Of course.

[Brief explanation of the drawing]

FIG. 1 is a process flow diagram showing an example of the equipment used to carry out the method of the present invention. 1...methanol inlet, 2... _H2O inlet,
3... Heat exchanger, 4... Evaporator, 5... Reactor,
6... Condenser, 7... Storage drum, 8... Combustion furnace, 9... Flue, 10... Produced gas outlet, 11...
...Refining process, 12... Discharge pipe of condenser 6, 13...
...Exhaust gas pipe.

Claims (1)

[Claims] 1. Reaction of methanol vapor, water vapor that may not be added, and carbon dioxide that may be added at a temperature of 130 to 950°C and a pressure of 1 to 100 atmospheres in the presence of a catalyst. , a process for producing gases containing hydrogen and carbon monoxide in varying concentrations, with the balance being carbon dioxide and possibly methane, water vapor and methanol, which initially contain very small amounts of methanol at the time of initial operation. The steam is passed through a reactor containing an unreduced catalyst or an unprepared reduced catalyst, the amount of methanol is gradually increased until a normal composition is reached, and the operation is carried out at temperatures above the dew point of 400°C.
A method for producing gas from methanol, characterized in that reducing the catalyst before the start of operation is not necessary by carrying out the process at the following temperature and under a pressure of 1 to 100 atmospheres. 2. Claim 1 using a catalyst that is mainly composed of zinc or zinc and chromium, and may also contain one or more of Cu, Co, Pt, Pd, Rh, Ni, Mn, Mg, and Mo. Method described. 3 The main components are nickel or nickel and chromium as a catalyst, Cu, Co, Pt, Pd, Rh, Zn,
The method according to claim 1, using a catalyst which may also contain one or more of Mn, Mg and Mo. 4. The entire amount of heat required for the methanol cracking reaction or steam reforming reaction is supplied by direct combustion of a portion of the reaction product gas and/or the exhaust gas from the purification process of the reaction product gas, or by such combustion. A method as claimed in claim 1, characterized in that it is supplied by a heated heat transfer medium. 5. The method according to claim 4, wherein the reaction purification gas is purified using a molecular sieve for the purpose of obtaining pure hydrogen. 6. The method according to claim 1, wherein the molar ratio of steam to methanol is 10 or less. 7. The method according to claim 1 or 6, wherein the molar ratio of carbon dioxide and methanol is 10 or less.