JP4315367B2 - Direct reformer for lower hydrocarbons - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct reforming apparatus for directly producing aromatics and hydrogen by reforming lower hydrocarbons such as methane.
[0002]
[Prior art]
Conventionally, as a process for producing an aromatic compound and hydrogen from a lower hydrocarbon such as methane, for example, a catalyst such as a ZSM5 type zeolite catalyst is supported with a metal such as molybdenum or an alloy catalyst, and in the presence of this catalyst, temperature, pressure A technique for selectively producing an aromatic compound such as benzene and hydrogen from a lower hydrocarbon such as methane by reacting a lower hydrocarbon under certain reaction conditions (Patent Documents 1, 2, and 5). 3 etc.).
[0003]
[Patent Document 1]
JP 2001-316302 A [Patent Document 2]
JP 2001-334151 A [Patent Document 3]
Japanese Patent Laid-Open No. 2002-336704
[Problems to be solved by the invention]
However, the conversion of this reaction for producing hydrogen and benzene from methane is governed by thermodynamic equilibrium and varies with temperature and pressure as shown in FIG. For example, at 750 ° C. and 3 atm, the equilibrium conversion rate reaches only a dozen percent. For this reason, even if 100 mol of methane as a raw material is reacted, for example, nearly 90 mol of methane is discharged as an unreacted off gas, which is disadvantageous in that the efficiency is poor and the production costs of hydrogen and benzene are increased.
In response to this drawback, a method has been proposed in which the hydrogen in the off-gas is purified by a hydrogen purifier such as PSA (pressure swing adsorption) and then the unreacted methane is recycled to the reforming section to increase the actual conversion rate. Yes. An example of an apparatus used in this method is shown in FIG. That is, in this apparatus, the raw material methane gas 1 is directly introduced into the reforming unit 2 for direct reforming, and then introduced into the aromatic separation unit 3 to separate the aromatic compounds, and the separated gas is supplied to the hydrogen separation unit. 10 is introduced. In the hydrogen separation unit 10, hydrogen is purified by using a hydrogen permeable membrane or the like that selectively permeates hydrogen to separate the hydrogen and use it in another system. On the other hand, the remaining gas from which hydrogen has been separated is refluxed to the reforming section 2 through the reflux path 20 to improve the conversion rate. In the figure, reference numerals 4 and 6 denote compressors.
[0005]
However, when purifying high-purity hydrogen from the gas from which the aromatic compound has been separated and recovering the remaining gas and then reacting it again, hydrogen and by-products that cannot be purified in addition to methane gas are included in the remaining gas. Since ethane, ethylene and the like remain, the methane purity as a raw material is lowered. If the methane purity is low, the reaction efficiency of the direct reforming catalyst will be seriously affected. For this reason, conventionally, there has been a problem that the conversion rate is not improved as expected even if a gas obtained by purifying hydrogen and separating the hydrogen is used again for reforming.
[0006]
The present invention has been made against the background of the above circumstances, and the low one-pass equilibrium conversion rate is achieved not by purifying hydrogen from a mixed gas containing hydrogen and unreacted lower hydrocarbons, but as raw material lower hydrocarbons. It is an object of the present invention to provide a direct reforming apparatus that can improve the equilibrium conversion rate by purifying and subjecting it to reforming.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 of the direct reforming apparatus for lower hydrocarbons of the present invention comprises a reforming section for directly reforming by introducing lower hydrocarbons as a raw material. An aromatic separation section for separating the aromatic compound by introducing a gas, a lower hydrocarbon separation section for separating the unreacted raw material lower hydrocarbon by introducing a separation gas from which the aromatic compound has been separated, and the lower carbonization A reflux line for returning the lower hydrocarbons separated in the hydrogen separation unit to the reforming unit, and a line for separating the lower hydrocarbons in the lower hydrocarbon separation unit and discharging a residual gas containing hydrogen out of the system. It is characterized by providing .
[0008]
The invention of a direct reforming apparatus for lower hydrocarbons according to claim 2 is characterized in that a reforming section for directly reforming by introducing lower hydrocarbons as a raw material, and an aromatic compound by separating the reformed gas. An aromatic separation part, a lower hydrocarbon separation part for introducing an unreacted raw material lower hydrocarbon by introducing a separation gas from which an aromatic compound has been separated, and a lower hydrocarbon separated by the lower hydrocarbon separation part It is characterized by comprising a reflux line that returns to the reforming section, and a hydrogen separation section that separates hydrogen from the remaining separated gas obtained by separating the unreacted raw material lower hydrocarbon in the lower hydrocarbon separation section .
[0013]
That is, according to the direct reforming apparatus of the present invention, after separating the aromatic compound from the directly reformed product gas, the raw material lower hydrocarbon is further separated from the gas from which the aromatic compound has been separated, Since hydrogen is directly recirculated to reforming, it is possible to continuously supply by-product gas that causes direct degradation of the reforming performance and low-impurity lower hydrocarbons that eliminates hydrogen as much as possible, thereby increasing the actual conversion rate. It can be directly modified for a long time while maintaining good performance.
[0014]
The residual gas from which the raw material lower hydrocarbon has been separated contains mainly the raw material lower hydrocarbon that could not be separated from the produced hydrogen (for example, about 50%), and also contains by-products. Yes. This gas can be used as fuel as it is. In addition, hydrogen can be separated from this gas, and the remaining gas can be used as fuel.
[0016]
In the present invention, lower hydrocarbons are used as a raw material gas. The type is not limited to a specific type, but typically includes methane. Further, the lower hydrocarbon as a raw material may be composed of a plurality of types in addition to a single type.
The method of directly reforming lower hydrocarbons is not particularly limited as well in the present invention, but examples include those using a catalyst in which one or more metals are supported on a carrier as a catalyst material. In reforming, an aromatic compound and hydrogen are generated from lower hydrocarbons as raw materials, and ethane, ethylene, and the like are also generated as by-products. In addition, unreacted raw material lower hydrocarbons remain in the reformed gas.
[0017]
The reformed gas is then separated from aromatic compounds. The method for separating the aromatic compound is not particularly limited, and can be performed by an appropriate method such as fractional distillation or dissolution in a separation liquid. The gas separation of the aromatic compound, then separated material lower hydrocarbon. Also in the separation, the present invention is not limited to a specific separation method, and an appropriate method can be adopted. For example, a membrane separation method using a PSA (pressure swing adsorption method) or a permeable membrane can be used. It should be noted that the separation can be performed in multiple stages, such as when the lower hydrocarbon is composed of a plurality of species.
Further, in the remaining gas from which the raw material lower hydrocarbon is separated, hydrogen can be further separated if desired. This separation method is not particularly limited in the present invention, and an appropriate method can be adopted. For example, PSA and membrane separation methods can be used in the same manner as described above.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
In the following, one embodiment of this invention will be described with reference to FIG. In addition, about the structure equivalent to the conventional method of FIG. 4, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.
In the apparatus of this embodiment, a direct reforming unit 2 for introducing a raw material hydrocarbon (methane) 1, an aromatic separation unit 3 for introducing a gas reformed in the direct reforming unit 2, and an aromatic compound Is introduced into the lower hydrocarbon separation section 4 for separating the raw material lower hydrocarbons by introducing the remaining gas, and the reflux for returning the raw material lower hydrocarbons separated in the lower hydrocarbon separation section 4 to the direct reforming section 2 Line 8 is included. A compressor 4 is installed between the aromatic separation unit 3 and the lower hydrocarbon separation unit 5, and a compressor 6 is installed in the reflux line 7.
[0019]
The direct reforming unit 2 is a direct reforming apparatus in which a ZSM5 type zeolite having a pore system of about 5 mm is filled with a catalyst supporting a metal such as molybdenum. The aromatic separation unit 3 is a separation / purification device that separates aromatics (benzene, toluene, naphthalene: BTX) from a gas containing hydrogen and unreacted gas generated in the direct reforming unit 2. Aromatic compounds are separated. The lower hydrocarbon separation unit 5 includes a PSA and a separation membrane, and separates the raw material lower hydrocarbon and discharges it to the reflux line 7.
[0020]
Next, the operation of the apparatus of this embodiment will be described.
The raw material lower hydrocarbon 1 is directly introduced into the reforming section 2, and by-products such as hydrogen, aromatic compounds, and ethane are generated in the direct reforming section 2. Some raw lower hydrocarbons remain unreacted without reacting. These gases are directly discharged from the reforming unit 2 and introduced into the aromatic separation unit 3. In the aromatic separation unit 3, an aromatic compound (BTX) such as benzene is separated and taken out of the system. The residue from which the aromatic compound has been separated is sent to the lower hydrocarbon separation section 5 via the compressor 4, and in this embodiment, methane is separated as the raw material lower hydrocarbon. This raw material lower hydrocarbon is sent directly to the reforming section 2 by the compressor 6 in the reflux line 7. Further, in the lower hydrocarbon separation unit 5, the residual gas from which the raw material lower hydrocarbon is separated is discharged out of the system, part of it becomes combustion off-gas, and the other off-gas for surplus heat supply in other systems 8 ( It is used as a surplus off gas after heat supply.
[0021]
The unreacted raw material lower hydrocarbon directly returned to the reforming section 2 is further subjected to a reforming reaction and contributes to an improvement in the conversion rate. Further, the returned unreacted raw material lower hydrocarbon contains less hydrogen and by-products, and the adverse effects in the reforming section 2 can be avoided directly.
[0022]
(Embodiment 2)
In the above embodiment, the residual gas from which the raw material gas is separated is intended to be used as an off-gas in other systems. However, the hydrogen is separated from the residual gas and the hydrogen is actively used. It is also possible to plan.
FIG. 2 shows an apparatus that makes it possible to separate hydrogen from the remaining gas from which methane has been separated. In addition, about the structure similar to the said Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.
[0023]
Also in the apparatus of this embodiment, as in the first embodiment, the direct reforming unit 2, the aromatic separation unit 3 into which the gas reformed in the direct reforming unit 2 is introduced, and the aromatic compound A lower hydrocarbon separation section 5 for introducing the remaining separated gas to separate lower hydrocarbons, and a reflux line 7 for returning the raw material lower hydrocarbons separated in the lower hydrocarbon separation section 5 to the direct reforming section 2 And have. Furthermore, in this embodiment, the residual gas which isolate | separated raw material lower hydrocarbon in the lower hydrocarbon separation part 5 is introduce | transduced, and the hydrogen separation part 10 which isolate | separates hydrogen from this gas is provided. The separation method in the hydrogen separation unit 10 is not particularly limited as the present invention, and for example, an appropriate method such as a membrane separation method that allows PSA or hydrogen to permeate can be employed.
[0024]
Also in this apparatus, the lower hydrocarbon is reformed directly in the reforming section 2, and the aromatic compound produced by the reforming is separated in the aromatic separation section 3. The gas from which the aromatic compound has been separated is refluxed directly to the reforming section 2 in the same manner as in the above embodiment after the lower hydrocarbon is separated by the lower hydrocarbon separation section 5. The remaining gas from which the lower hydrocarbons have been separated is sent to the hydrogen separation unit 10 where the hydrogen is separated and taken out of the system. The gas excluding hydrogen can be used as a fuel as in the first embodiment or can be used in another system 8.
[0025]
【The invention's effect】
As described above, according to the present invention, after separating the aromatic compound from the gas directly reformed from the lower hydrocarbon as a raw material, the unreacted raw material lower hydrocarbon is separated from the separated gas from which the aromatic compound has been separated. As a result, the raw material gas having high purity can be directly recycled to the reforming section, the actual conversion rate can be increased, and the apparatus can be stably operated for a long time.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a reformer in one embodiment of the present invention.
FIG. 2 is a flow diagram of a reformer in another embodiment.
FIG. 3 is a graph showing the temperature and pressure dependence of the equilibrium conversion rate when hydrogen and benzene are produced from methane.
FIG. 4 is a flowchart of a conventional reformer.
[Explanation of symbols]
1 Raw material methane gas 2 Direct reforming section 3 Aromatic separation section 4, 6 Compressor 5 Lower hydrocarbon separation section 7 Reflux line 8 Other system 10 Hydrogen separation section 20 Reflux path

Claims (2)

  A reforming section that directly reforms by introducing lower hydrocarbons as a raw material, an aromatic separation section that introduces a reformed gas to separate aromatic compounds, and a separation gas that separates aromatic compounds are introduced. A lower hydrocarbon separation part for separating the unreacted raw material lower hydrocarbon, a reflux line for returning the lower hydrocarbon separated in the lower hydrocarbon separation part to the reforming part, and a lower hydrocarbon separation part in A lower hydrocarbon direct reforming apparatus comprising a line for separating the lower hydrocarbons and discharging a residual gas containing hydrogen to the outside of the system.   A reforming section that directly reforms by introducing lower hydrocarbons as a raw material, an aromatic separation section that introduces a reformed gas to separate aromatic compounds, and a separation gas that separates aromatic compounds are introduced. A lower hydrocarbon separation part for separating the unreacted raw material lower hydrocarbon, a reflux line for returning the lower hydrocarbon separated in the lower hydrocarbon separation part to the reforming part, and a lower hydrocarbon separation part in A direct reformer for lower hydrocarbons, comprising: a hydrogen separation unit that separates hydrogen from the remaining separation gas from which unreacted raw material lower hydrocarbons are separated.

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