JP2004269294A - Method for producing synthesis gas and method for producing dimethyl ether using synthesis gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a hydrocarbon-free synthesis gas with a reduced carbon dioxide concentration. <P>SOLUTION: In the method for producing a synthesis gas essentially comprising hydrogen and carbon monoxide, a gas generated through partial combustion of a hydrocarbon is reformed by a catalyst using a synthesis gas-generating furnace wherein a catalytic layer is installed. The outlet temperature of the catalyst layer is kept at 1,100-1,300°C, and the carbon dioxide concentration in the produced synthesis gas is set at ≤10%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a synthesis gas containing hydrogen and carbon monoxide as main components by reforming a gas generated by partial combustion of hydrocarbons with a catalyst and a method for producing dimethyl ether using the synthesis gas. It is. Note that this synthesis gas _is suitable as a synthesis gas of H 2 /CO=0.8~1.2 (molar ratio).
[0002]
[Prior art]
A synthesis gas containing hydrogen and carbon monoxide is used as a raw material for FT synthesis, methanol synthesis, ammonia synthesis, and the like.
[0003]
This synthesis gas is produced from various organic compounds, and the production method of the synthesis gas is known to include a reaction with steam and / or carbon dioxide, a partial oxidation reaction with oxygen and / or air, and the like.
[0004]
In particular, for gaseous organic compounds, (1) a method of reacting organic compounds with steam and / or carbon dioxide in the presence of a catalyst at a high temperature, and (2) partial oxidation of the organic compounds with oxygen and / or air. And (3) a method of combining (1) and (2) with steam and / or carbon dioxide to cause a reaction in the catalyst layer.
[0005]
However, the above method has the following problems.
[0006]
In the method (1), the organic compound decomposes at a high temperature to form carbon on the catalyst, so that there is an upper limit temperature. In the method (2), the organic compound is immediately decomposed by oxygen, but the organic compound consumed as a heat source is preferably as small as possible. Further, in any of the methods (1) to (3), a reaction occurs in which carbon is generated on the catalyst from the generated carbon monoxide, and thus a minimum temperature exists.
[0007]
In order to solve such a problem, the following method is disclosed.
[0008]
First, as an example of a method for producing a synthesis gas using a catalyst, Patent Document 1 discloses that a carbon dioxide gas and / or steam is reacted with an unreacted carbon-containing organic compound in a high-temperature mixed gas. In this case, a method using a catalyst with suppressed carbon deposition activity is disclosed.
[0009]
Patent Document 2 aims to provide a high-performance catalyst for syngas production by a methane reforming reaction, and a metal compound selected from at least one of platinum group metals is supported or mixed in a prescribed amount on the catalyst. It is disclosed that a highly active catalyst for methane reforming reaction can be obtained by denaturation.
[0010]
On the other hand, as a method for producing a synthesis gas without using a catalyst, for example, Patent Document 3 discloses that the generation temperature is about 1000 to 1900 ° C.
[0011]
[Patent Document 1]
Re-published WO 98/46525 [Patent Document 2]
Japanese Patent Application Laid-Open No. 9-131533 [Patent Document 3]
Japanese Patent Publication No. 52-46192
[Problems to be solved by the invention]
However, in the method using a catalyst, when H ₂ / CO of the synthesis gas is reduced to 2 or less, an increase in the concentration of carbon dioxide in the generated synthesis gas cannot be ignored. For example, a dimethyl ether synthesis process using the reaction formula of the following formula (1) requires a synthesis gas having a ratio of hydrogen to carbon monoxide of 1: 1. Reaches 20 to 40% without water.
[0013]
_{3H 2 + 3CO → CH 3 OCH} 3 + CO 2 --- (1)
[0014]
Carbon dioxide contained in the raw material gas inhibits the reaction and adversely affects the production. Circulating a large amount of carbon dioxide in the reaction system is not preferable in terms of equipment costs and operation costs.
[0015]
In order to prevent this, a process of removing CO ₂ of the raw material gas may be added, but this leads to an increase in equipment cost and operation cost.
[0016]
Further, it is known that carbon is generated in the catalyst layer by the following reaction, which increases the pressure loss of the catalyst layer and reduces the reactivity by covering the surface of the catalyst, thereby hindering the operation of the apparatus.
[0017]
2CO → C + CO ₂
[0018]
In the above, when producing a synthesis gas in which H ₂ / CO is as low as about 1, the CO concentration in the gas is increased, so that carbon is particularly easily generated.
[0019]
On the other hand, in the method using no catalyst, the reaction temperature tends to be high in order not to leave unreacted organic compounds and hydrocarbons as intermediate products. High temperature is obtained by combustion of fuel, the proportion varying the material to be H ₂ and CO the heat increases, energy efficiency is reduced. Although it is conceivable to lower the reaction temperature in order to increase energy efficiency, when the reaction temperature is lowered, hydrocarbons such as methane and acetylene are contained in the product gas. Residual methane reduces the reactivity of downstream syngas utilization processes, leaving residual acetylene difficult to compress the syngas and creates the risk of producing explosive acetylides in the plant system.
[0020]
The present invention has been made in view of such circumstances, and a method for producing a synthesis gas which does not contain hydrocarbons in the produced synthesis gas and reduces the concentration of carbon dioxide in the synthesis gas, and uses the same. It is an object of the present invention to provide a method for producing dimethyl ether.
[0021]
[Means for Solving the Problems]
The present inventors have focused on the equilibrium temperature in order to solve the above problems, and as a result, have obtained the following findings.
[0022]
When the temperature at which equilibrium is reached (exit temperature of the catalyst layer) is 1100 to 1300 ° C., no soot is generated even if the hydrogen / carbon monoxide ratio is reduced, and the amount of carbon dioxide as an auxiliary material can be reduced. . As a result, it is possible to reduce the concentration of carbon dioxide in the produced gas to 10 Vol% or less with the LNG fuel. With LPG fuel, the concentration of carbon dioxide in the product gas can be 5 Vol%. Further, since the catalyst works efficiently at a high temperature, an expensive catalyst containing a rare metal is not required, and the amount of the catalyst may be small.
[0023]
Furthermore, the temperature at the inlet of the catalyst layer is suppressed by setting the gas residence time upstream of the catalyst layer to 2 seconds or more.
[0024]
The present invention has been made based on the above findings, and has the following features.
[0025]
According to the first aspect of the present invention, a gas generated by partial combustion of hydrocarbons is reformed by a catalyst using a synthesis gas generator having a catalyst layer provided therein, and hydrogen and carbon monoxide are mainly used. The method for producing a synthesis gas as a component is characterized in that the outlet temperature of the catalyst layer is 1100 to 1300 ° C. and the concentration of carbon dioxide in the produced synthesis gas is 10% or less.
[0026]
The invention described in claim 2 is characterized in that the gas residence time upstream of the catalyst layer is 2 seconds or more.
[0027]
The invention described in claim 3 is characterized in that the synthesis gas is rapidly cooled to 600 ° C. or less immediately after the completion of the catalytic reaction.
[0028]
The invention described in claim 4 is a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen, wherein the synthesis gas is produced by the method according to any one of claims 1 to 3. It is characterized by using the synthesized gas.
[0029]
The invention described in claim 5 is a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen at a ratio of 1: 0.8 to 1.2, wherein the synthesis gas is used as the synthesis gas. Is characterized by using a synthesis gas produced by any one of the above methods.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
The details of the present invention will be described below together with the reasons for the limitation.
[0031]
In a normal synthesis gas production process, excessive carbon dioxide remains, which inhibits the reaction and adversely affects the production. First, the results of an examination of this will be described below.
[0032]
For example, in a process of synthesizing dimethyl ether from a source gas containing carbon monoxide and hydrogen represented by the following formula (1), a synthesis gas having a ratio of hydrogen to carbon monoxide of 1: 1 is required.
[0033]
_{3H 2 + 3CO → CH 3 OCH} 3 + CO 2 --- (1)
[0034]
However, when producing a synthesis gas (a mixed gas mainly (containing) hydrogen and carbon monoxide) using natural gas or propane gas as a raw material, the molar ratio of hydrogen / carbon monoxide is usually 2 or more. If the synthesis gas is used in a dimethyl ether synthesis process, the hydrogen / carbon monoxide molar ratio in the synthesis gas must be reduced. In order to reduce the ratio of hydrogen in the synthesis gas, for example, it is effective to add carbon dioxide to a synthesis gas reaction system and react with hydrogen as shown in the following formula (2) to increase carbon monoxide. is there.
[0035]
_{H 2 + CO 2 → CO +} H 2 O --- (2)
[0036]
However, since the above equation (2) is an equilibrium reaction, not all of the input carbon dioxide reacts, and unreacted, that is, excess carbon dioxide remains in the generated synthesis gas. . In actuality, in order to make the ratio of hydrogen to carbon monoxide 1: 1, carbon dioxide is usually added to the raw material gas such as natural gas at a flow rate higher than that of the raw material gas. Reaches 20 to 40% without water.
[0037]
Therefore, the present inventors have further studied to solve the decrease in the concentration of carbon dioxide. As a result, the following findings were obtained.
[0038]
The generated synthesis gas contains carbon monoxide, carbon dioxide, hydrogen, and water (steam), and these are kept in equilibrium by a shift reaction represented by the following reaction formula (3).
[0039]
_{CO + H 2 O = CO 2} + H 2 --- (3)
[0040]
In order to increase carbon monoxide (CO) and decrease hydrogen (H ₂ ), carbon dioxide (CO ₂ ) may be added to the system and the reaction may be advanced to the left. The carbon dioxide concentration in it will increase. On the other hand, to the left the reaction at higher temperatures, since it proceeds to the right lower temperature, in order to increase the reduction i.e. CO and H ₂ would may be reacted at elevated temperatures. By increasing the temperature, a low H ₂ / CO ratio can be realized while suppressing CO ₂ added to the system and suppressing the concentration of CO ₂ contained in the product gas. However, the catalyst generally has a heat-resistant temperature, and the temperature cannot be raised any higher. There is a Ni catalyst as a generally used catalyst. The melting point of Ni is 1455 ° C., and the upper limit temperature of use of a Ni catalyst carrying fine Ni particles is naturally lower than that.
[0041]
Here, the synthesis gas of the present invention is produced using a synthesis gas generating furnace having a catalyst layer installed therein. That is, a synthesis gas generating furnace is an auto thermal reformer (hereinafter referred to as ATR) for reforming a gas generated by partial combustion of hydrocarbons with a catalyst to produce a synthesis gas containing hydrogen and carbon monoxide as main components. Even when the temperature of the synthesis gas obtained is about 1000 ° C., the temperature of the catalyst layer inlet in the ATR is usually about 1400 ° C., so that the ATR is usually operated at a temperature lower than this.
[0042]
Here, the present inventors studied the temperature difference between the entrance and exit of the catalyst layer in the ATR. As a result, it was found that the gas entering the catalyst layer usually contained methane leaked from the partial combustion region, and this was the main cause of forming the temperature difference between the entrance and exit of the catalyst layer. That is, methane reacts with surrounding CO ₂ and H ₂ O to change into CO + H ₂ , which is an endothermic reaction. When calculated from the endothermic amount, it is assumed that methane containing about 10% of methane at the entrance of the catalyst layer is 1400%. When the methane gas is completely decomposed in the catalyst layer, the temperature at the outlet of the catalyst layer becomes about 1000 ° C.
[0043]
In addition, a reaction equilibrium is established at the outlet of the catalyst layer having a sufficient capacity for eliminating methane, and this temperature determines the CO ₂ concentration of the generated synthesis gas.
[0044]
From the above, if the methane concentration at the inlet of the catalyst layer is reduced, the temperature difference between the inlet and outlet of the catalyst layer in the ATR disappears, and the outlet temperature of the catalyst layer can be increased while maintaining the temperature of the inlet of the catalyst layer at the catalyst heat-resistant temperature. It can be seen that the CO ₂ concentration in the synthesis gas can be reduced.
[0045]
Then, when the amount of oxygen for performing partial combustion of hydrocarbons was increased for the purpose of raising the catalyst layer outlet temperature, it was found that the temperature rise at the catalyst layer inlet was smaller than that at the catalyst layer outlet. This is because the partial combustion reaction is promoted by increasing the temperature of the region where the partial combustion occurs, and the amount of methane leaking out is reduced.
[0046]
As described above, the temperature at the outlet of the catalyst layer is preferably higher in order to suppress the concentration of CO ₂ contained in the product gas. However, on the other hand, raising the catalyst layer outlet temperature allows a reduction in the CO ₂ concentration but lowers the energy efficiency. Therefore, in the present invention, the catalyst layer outlet temperature is set to 1100 to 1300 ° C. in order to reduce the CO ₂ concentration to 10% or less.
[0047]
Further, it is known that carbon is generated in the catalyst layer by the following reaction, which increases the pressure loss of the catalyst layer and reduces the reactivity by covering the surface of the catalyst, thereby hindering the operation of the apparatus.
[0048]
2CO → C + CO ₂
[0049]
Since this reaction is exothermic, it occurs at lower temperatures. Regarding this point (carbon generation suppression), it is effective to increase the temperature of the catalyst layer. In fact, by setting the catalyst layer outlet temperature to 1100 ° C. or higher, even if a synthesis gas having a H ₂ / CO of about 1 is produced in a reaction of about 30 atm, generation of carbon on the catalyst surface is not recognized. Was.
[0050]
On the other hand, even when a raw material gas at a catalyst layer outlet temperature of 1300 ° C. was supplied, hydrocarbon gas such as methane and acetylene remained in the gas entering the catalyst layer. As noted above, residual methane reduces the reactivity of downstream syngas utilization processes, leaving residual acetylene difficult to compress syngas and creates the danger of producing explosive acetylides in the plant system. Will happen. That is, a catalyst is indispensable for the present process, and this makes it possible to achieve both low CO ₂ concentration and high thermal efficiency.
[0051]
As described above, by producing the synthesis gas with the temperature at which this equilibrium is reached, that is, the temperature of the catalyst layer (outlet) being 1100 to 1300 ° C., even if the oxygen / fuel ratio is reduced, it does not enter the soot generation region, Can be suppressed. Further, a shift reaction control with temperature - can le, in order to reduce the hydrogen (H _2), the reaction system is not necessary to add a carbon dioxide (CO ₂₎ in an amount of conventionally required the H 2 _/ CO The amount of secondary material: carbon dioxide to achieve a ratio (for example, the ratio is 1 in DME synthesis) can also be reduced. As a result, the concentration of carbon dioxide in the generated gas can be reduced to 10 Vol% or less with the LNG fuel. Since the LPG fuel has a high carbon / hydrogen ratio in the molecule, the CO concentration can be easily increased, and the carbon dioxide concentration in the produced gas can be reduced to 5 Vol%. Further, since the catalyst works efficiently at a high temperature, the amount of the catalyst is small.
[0052]
As described above, according to the present invention, in the method for producing a synthesis gas containing hydrogen and carbon monoxide as main components by reforming a gas generated by partial combustion of hydrocarbons with a catalyst, the temperature of the catalyst layer is set to 1100 to 1100. The temperature is 1300 ° C., and the concentration of carbon dioxide in the synthesis gas is 10% or less.
[0053]
Further, in the present invention, it has been found that by securing a space upstream of the catalyst layer, that is, by providing a sufficient gas residence time, the decomposition reaction of methane is promoted, and the catalyst layer inlet temperature can be further reduced. The gas residence time upstream of the catalyst layer is preferably at least 2 seconds, more preferably at least 3 seconds. By securing a space upstream of the catalyst layer such that the gas residence time is 2 seconds or longer, the temperature of the catalyst layer inlet can be suppressed to about 1400 ° C. when a raw material gas having a catalyst layer outlet temperature of 1300 ° C. is supplied. . Further, the Ni catalyst in the high-temperature portion caused some sintering and reduced initial performance. However, it was found that the required performance can be sufficiently exhibited for a long period of time because the catalyst is used at a high reactivity at a high temperature.
[0054]
Furthermore, in the present invention, it is preferable that the synthesis gas obtained by the above reaction be rapidly cooled to 600 ° C. or less immediately after the completion of the catalytic reaction. Thereby, the gas having the gas composition at the outlet of the catalyst layer can be sent to the downstream synthesis reaction. At 600 ° C. or lower, the reaction rate decreases, and the change in gas composition due to the following reaction is almost negligible. Therefore, the H ₂ / CO ratio can be maintained at a predetermined value, and methane or CO ₂ which inhibits a downstream synthesis reaction can be maintained. Does not increase.
[0055]
CO + H ₂ O → H ₂ + CO ₂
CO + 3H ₂ → CH ₄ + H ₂ O
2CO + 2H ₂ → CH ₄ + CO ₂
[0056]
Further, in order to promptly pass through a temperature region where a change in gas composition cannot be ignored, it is more preferable that the quenching be performed within 0.1 second after the completion of the reaction.
[0057]
The method for rapidly cooling the synthesis gas is not particularly limited. For example, there is a method in which water is sprayed on the gas discharged from the catalyst layer to directly cool the gas, and a method in which the gas is cooled indirectly by a heat exchanger.
[0058]
FIG. 1 shows one embodiment of a synthesis gas production furnace.
[0059]
In this embodiment, a raw material gas inlet 2 is formed at the upper end of the synthesis gas production furnace 1, a synthesis gas outlet 3 is formed at the lower end, and a catalyst layer 4 is provided inside the synthesis gas production furnace 1. ing.
[0060]
In the above structure, a heat insulating layer 5 for holding the catalyst layer 4 and a water-cooled metal tube 6 are sequentially provided below the catalyst layer 4. Further, the production furnace is provided with cooling means 7 for cooling the produced synthesis gas, such as water spray, directly below the water-cooled metal pipe 6. With the above structure, the inside of the manufacturing furnace is made compact, and the catalyst layer 4 is easily held by the heat insulating layer 5 and the water-cooled metal tube 6.
[0061]
According to this synthesis gas production furnace, the raw material gas is introduced into the synthesis gas production furnace 1 through the raw material gas inlet 2, and comes into contact with the catalyst layer 4 in the process of flowing downward through the synthesis gas production furnace 1, whereby the target synthesis gas is produced. Gas is obtained. Next, the synthesis gas is rapidly cooled to a temperature in the range of 1100 to 1300 ° C. by coming into contact with the heat insulating layer 5 and coming into contact with the water-cooled metal pipe 6 and the cooling means 7. Then, the synthesis gas having a CO ₂ concentration of 10% or less is discharged from the synthesis gas outlet 3 to the outside of the furnace.
[0062]
The type of the catalyst is not particularly limited, as long as it can satisfy the heat resistance at the reaction temperature of 1100 to 1300 ° C. For example, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, potassium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, gold, cadmium, indium, tin, hafnium, tantalum, tungsten, Rhenium, osmium, iridium, platinum, silver, mercury, tellurium, lead, bismuth, thallium, uranium, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, boron, aluminum, scandium, thorium, Metals such as lead and lanthanoids, oxides and the like can be used.
[0063]
The catalyst can be supported on a carrier. As the carrier, silica, alumina, titania, zirconia, magnesia, zeolite and the like can be used alone or in combination of two or more.
[0064]
The particle size of the catalyst is not particularly limited.
[0065]
The hydrocarbons of the raw material gas are methane and hydrocarbons having about 2 to 5 carbon atoms, mixtures thereof, natural gas, methane produced from coal and other substances, LPG, and the like, and these can also be used as an appropriate mixture. .
[0066]
Oxygen may be pure oxygen or air.
[0067]
The reactor is not particularly limited. The gases used in the reaction are hydrocarbons, oxygen, carbon dioxide and water vapor, but may contain nitrogen gas.
[0068]
As the reaction conditions other than the temperature of the catalyst layer, the pressure is from about atmospheric pressure to about 50 atm, but is not particularly limited.
[0069]
【The invention's effect】
As described above, according to the present invention, it is possible to produce a synthesis gas containing no hydrocarbon in the produced synthesis gas and having a reduced carbon dioxide concentration in the synthesis gas. In addition, since the synthesis gas of the present invention has reduced carbon dioxide, when synthesis gas is used as a raw material in a utilization process (for example, a dimethyl ether synthesis process), there is no need to provide a step for removing carbon dioxide and the synthesis gas is directly used. It can be supplied as raw material to utilization process. As a result, for example, dimethyl ether can be stably produced at a higher yield from synthesis gas.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing one embodiment of a synthesis gas production furnace.
[Explanation of symbols]
1: synthesis gas production furnace 2: raw material gas inlet 3: synthesis gas outlet 4: catalyst layer 5: heat insulating layer 6: water-cooled metal tube 7: cooling means

Claims (5)

In a method for producing a synthesis gas containing hydrogen and carbon monoxide as a main component, using a synthesis gas generation furnace having a catalyst layer installed therein, reforming a gas generated by partial combustion of hydrocarbons with a catalyst,
A method for producing a synthesis gas, wherein the outlet temperature of the catalyst layer is 1100 to 1300 ° C and the concentration of carbon dioxide in the produced synthesis gas is 10% or less. The method for producing a synthesis gas according to claim 1, wherein a gas residence time upstream of the catalyst layer is 2 seconds or more. The method for producing a synthesis gas according to claim 1, wherein the synthesis gas is rapidly cooled to 600 ° C. or less immediately after the end of the catalytic reaction. In a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen,
A method for producing dimethyl ether, wherein a synthesis gas produced by the method according to any one of claims 1 to 3 is used as the synthesis gas. In a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen at a ratio of 1: 0.8 to 1.2,
A method for producing dimethyl ether, wherein a synthesis gas produced by the method according to any one of claims 1 to 3 is used as the synthesis gas.

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