JP5243859B2 - Hydrogen production apparatus and hydrogen production method - Google Patents

Description

  The present invention relates to a hydrogen production apparatus using a dehydrogenation reaction and a hydrogen production method using the same, and more particularly to a hydrogen production apparatus and a hydrogen production method capable of improving the conversion rate of the dehydrogenation reaction as compared with the conventional one. Is.

  Since hydrocarbon dehydrogenation is an endothermic reaction, it is possible to introduce a preheated raw material into the catalyst layer in the reactor, which is normally used when producing hydrogen from hydride by dehydrogenation. In a raw material heating type adiabatic reactor that performs a dehydrogenation reaction, the temperature of the raw material (fluid to be dehydrogenated) and the temperature of the catalyst layer decrease with the progress of the reaction, and the reaction rate decreases toward the outlet side of the reactor. There was a point.

In order to solve this problem, Patent Document 1 discloses that in a multi-tubular fixed bed dehydrogenation reactor, hot air is supplied as a heating medium to heat the entire catalyst layer to compensate for a temperature decrease on the outlet side. A method for producing hydrogen is disclosed.
JP 2007-326053 A

  Here, in the heat exchange reactor described in Patent Document 1, the catalyst layer is heated by supplying a heat medium in a direction parallel to the raw material flow, and the catalyst layer is filled. Since the catalyst is composed of a single composition and is almost uniformly supported on the entire catalyst layer, the dehydrogenation reaction proceeds on the inlet side of the catalyst layer where the raw material concentration is high, and the reaction amount (endothermic amount) ) And the temperature of the catalyst layer decreases, while the concentration of the raw material is low from the middle part of the catalyst layer to the outlet side, and the hydrogen partial pressure is increased by the generated hydrogen, and the hydrogenation reaction which is a reverse reaction proceeds. Therefore, the dehydrogenation reaction is difficult to proceed, the reaction amount is reduced, and the temperature of the catalyst layer hardly decreases. That is, in the heat exchange reactor according to the prior art in which the catalyst concentration of the entire catalyst layer is uniform, the dehydrogenation reaction proceeds excessively on the catalyst layer inlet side, and the dehydrogenation reaction becomes slow on the catalyst layer outlet side. The average temperature of the entire catalyst layer is lowered. Therefore, the heat exchange reactor according to the prior art has room for improvement in that the entire catalyst layer does not contribute effectively to the dehydrogenation reaction.

  An object of the present invention is to advantageously solve the above-described problems, and the amount of reaction at the inlet side of the catalyst layer is reduced compared to a catalyst layer in which a dehydrogenation reaction catalyst is uniformly provided. The present invention provides a hydrogen production apparatus and a hydrogen production method capable of increasing the average temperature of the catalyst layer and increasing the conversion rate of the entire catalyst layer by increasing the reaction amount on the outlet side from the intermediate part.

  As a result of intensive studies to achieve the above object, the present inventor has improved the conversion rate of the dehydrogenation reaction by making the catalyst concentration on the outlet side of the catalyst layer for performing the dehydrogenation reaction higher than the catalyst concentration on the inlet side. As a result, the present invention has been completed.

That is, the hydrogen production apparatus of the present invention is an apparatus for producing hydrogen from a hydride of an aromatic hydrocarbon using a dehydrogenation reaction, wherein an inlet through which the hydride flows and a product of the dehydrogenation reaction are provided. A dehydrogenation reactor having a catalyst layer of a dehydrogenation reaction catalyst provided therein, and having a catalyst activity existing per unit volume in a portion of 1/3 from the inlet side of the catalyst layer The average catalyst concentration, which is the amount of the substance having a catalytic property, is lower than the average catalyst concentration, which is the amount of the substance having catalytic activity present per unit volume in the entire catalyst layer. In this way, the average catalyst concentration in the 1/3 portion from the inlet side of the catalyst layer is made lower than the average catalyst concentration in the entire catalyst layer, that is, lower than the average catalyst concentration in the 2/3 portion from the outlet side of the catalyst layer. By doing so, it is possible to suppress the rapid progress of the dehydrogenation in the vicinity of the inlet of the catalyst layer and to effectively contribute the entire catalyst layer to the dehydrogenation reaction. And a hydrogen production apparatus with a high conversion rate can be provided. The average catalyst concentration is the amount of a substance having catalytic activity per unit volume. For example, when a catalyst layer is formed by supporting a metal having catalytic activity on a carrier, the metal per unit volume Refers to the quantity.

  The hydrogen production apparatus of the present invention is preferably an apparatus equipped with a heat exchange type dehydrogenation reactor, and in particular, the catalyst layer and the catalyst can be obtained by flowing a heat medium in the same direction as the direction in which the raw material flows in the catalyst layer. An apparatus comprising a cocurrent heat exchange type dehydrogenation reactor for heating the raw material flowing through the bed is preferable. Since the reactor in which the heat medium flows in parallel flow has a larger amount of dehydrogenation reaction near the catalyst layer inlet than the reactor in which the heat medium flows in countercurrent, the effect of the present invention is particularly remarkable. is there. As such a co-current heat exchange type dehydrogenation reactor, for example, an inflow port through which raw materials flow in and an outflow port through which products of the dehydrogenation reaction flow out are packed inside with a dehydrogenation reaction catalyst. A reaction tube and a jacket portion provided around the reaction tube so as to allow a heat medium to flow therethrough, and the jacket portion flows a heat medium in a direction from the inlet side to the outlet side of the reaction tube. is there.

  Here, the distribution of the catalyst in the catalyst layer may be any distribution as long as the average catalyst concentration in the 1/3 portion from the inlet side of the catalyst layer is lower than the average catalyst concentration of the entire catalyst layer. It is possible to change (gradate) stepwise so that the catalyst concentration gradually increases from the side toward the outlet side. In addition, the portion from 1/5 to 1/2 of the catalyst layer starting from the inlet of the catalyst layer is uniformly formed at the first catalyst concentration, and the remaining portion is the first catalyst. You may comprise uniformly with the 2nd catalyst density | concentration larger than a density | concentration.

  In the hydrogen production apparatus of the present invention, it is preferable that an average catalyst concentration in a third of the catalyst layer from the inlet side is 0.3 to 0.7 times the average catalyst concentration of the entire catalyst layer. If the average catalyst concentration in the 1/3 portion from the inlet side of the catalyst layer is less than 0.3 times the average catalyst concentration of the entire catalyst layer, the reaction amount near the catalyst layer inlet becomes too low and the conversion as a whole This is because if the rate decreases and exceeds 0.7, the amount of reaction in the vicinity of the catalyst layer inlet becomes too large and the overall conversion rate decreases.

  Further, the hydrogen production method of the present invention is a method for producing hydrogen from a hydride of an aromatic hydrocarbon using a dehydrogenation reaction, wherein the raw material contains the hydride in a hydrogen production apparatus provided with a dehydrogenation reactor. A step of performing a dehydrogenation reaction of the hydride in the dehydrogenation reactor, and a step of taking out a product of the dehydrogenation reaction containing at least hydrogen, wherein the hydrogen production apparatus is as described above. It is a hydrogen production apparatus. According to such a hydrogen production method, the entire catalyst layer can be effectively contributed to the dehydrogenation reaction by suppressing the abrupt dehydrogenation reaction in the vicinity of the inlet of the catalyst layer immediately after the raw material supply. And the hydrogen production method with a high conversion rate can be provided.

  According to the present invention, hydrogen can be efficiently produced from a hydride of an aromatic hydrocarbon by performing a dehydrogenation reaction at a high dehydrogenation conversion rate.

  A preferred embodiment of the present invention will be specifically described below with reference to FIG. However, the present invention is not limited to the form shown in FIG.

  In the hydrogen production apparatus 1 as an example of the hydrogen production apparatus of the present invention shown in FIG. 1, the aromatic hydrocarbon hydride is pumped up from the tank 2 for storing the aromatic hydrocarbon hydride as a raw material and then distributed. After mixing with hydrogen and preheating and vaporizing the mixture of the flowing hydrogen and hydride in the primary vaporizer 4 and the secondary vaporizer 5, the mixture is supplied to the dehydrogenation reactor 6 to perform the dehydrogenation reaction. The product after the dehydrogenation reaction in the dehydrogenation reactor 6 is supplied to the hydrogen separator 7, and hydrogen gas is removed from the product by a hydrogen separation membrane (not shown) provided in the hydrogen separator 7. Separated and recovered. The gas that has not passed through the hydrogen separation membrane is used as a heat source for the primary vaporizer 4 to effectively use waste heat, and then cooled and condensed using cold water in the condenser 8. It is separated into liquid components such as unreacted aromatic hydrocarbon hydride, aromatic hydrocarbon generated by dehydrogenation reaction and alkylcyclopentane generated by side reaction, and hydrogen and other gases. The other gases separated include lower hydrocarbons generated by side reactions and liquid vapor that could not be separated. Here, hydrogen and other gas can be used as a raw material of a heat source, for example. On the other hand, a liquid component containing unreacted aromatic hydrocarbon hydride, aromatic hydrocarbon generated by the dehydrogenation reaction and alkylcyclopentane generated by the side reaction is recovered in the recovery oil tank 10 and is not shown in the figure. It can be re-hydrogenated in the apparatus and reused as an aromatic hydrocarbon hydride.

  Here, cyclohexanes and decalins can be used as the aromatic hydrocarbon hydride as a raw material, but from the viewpoint of the safety and ease of handling of the aromatic hydrocarbons produced after the dehydrogenation reaction, A group having a group is preferable, and alkylcyclohexane such as methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, diethylcyclohexane and trimethylcyclohexane, alkyldecalin such as methyldecalin, ethyldecalin, dimethyldecalin and diethyldecalin, and a mixture thereof may be used. preferable.

  The dehydrogenation reactor 6 which is a multi-tube type fixed bed flow reactor is a substantially cylindrical hermetic container, and the internal space serves as a reaction region 61 for dehydrogenating the raw material. The dehydrogenation reactor 6 is provided with a reaction tube 62 filled with a dehydrogenation reaction catalyst, penetrating the reaction region 61. In the reaction tube 62, the raw material is introduced from the upper inlet in FIG. The dehydrogenation reaction is carried out, and in FIG. 1, the product of the dehydrogenation reaction is discharged from the lower outlet. The dehydrogenation reaction catalyst (catalyst layer) in the reaction tube 62 is packed so that the average catalyst concentration in the １ ／ portion from the inlet side is lower than the average catalyst concentration in the entire catalyst layer.

  Here, as a raw material supply method to the dehydrogenation reactor 6, either a method of supplying an aromatic hydrocarbon hydride in a liquid or a method of supplying it in a preheated gas can be taken. It is preferable to supply the gas to a fixed bed type dehydrogenation reactor.

  In addition, air (heat medium) heated from the heat medium supply device 11 is supplied to the reaction region 61 so as to be in parallel with the raw material flow in the reaction tube 62, and the dehydrogenation reaction proceeds at an appropriate temperature. Have been able to. The reaction region 61 is provided with a baffle plate 63 for efficiently performing heat exchange. In FIG. 1, the heat medium supplied from the upper side to the reaction region 61 flows in a zigzag manner in the reaction region 61. It is designed to be discharged from the lower side. The heat medium discharged from the dehydrogenation reactor 6 is reused as a heat source for the secondary vaporizer 5 and then released into the atmosphere. Here, as the heat source for heating the heat medium in the heat medium supply device 11, heat generated by burning fuel with a heating means such as a burner can be used.

  The dehydrogenation reaction catalyst charged in the reaction tube 62 of the dehydrogenation reactor 6 is a metal having at least one catalytic activity selected from the group consisting of platinum, ruthenium, palladium, rhodium, tin, rhenium, and germanium. Those supported on a porous carrier are preferable, and it is preferable to appropriately select the average pore diameter depending on the type of aromatic hydrocarbon hydride used as a raw material. For example, a catalyst having an average pore size of 40 to 80 mm is particularly preferable when monocyclic cyclohexanes are used, and a catalyst having an average pore size of 65 to 130 mm is particularly preferable when bicyclic decalins are used. It is preferable to select any of the catalysts, and it is preferable that the volume of pores having a preferable pore diameter is 50% or more of the total pore volume.

In order to control the average pore diameter and the pore volume ratio of the dehydrogenation reaction catalyst, it is preferable to use Al ₂ O ₃ or SiO ₂ as the catalyst support, and these may be used alone. These may be used in combination at an appropriate ratio. When the aromatic hydrocarbon hydride is a mixture of one ring and two rings, a catalyst having a preferable average pore diameter may be mixed and used depending on the composition.

  Further, the metal loading of the porous carrier in the dehydrogenation reaction catalyst is preferably in the range of 0.001 to 10% by mass, and more preferably in the range of 0.01 to 5% by mass. If the metal loading is less than 0.001% by mass, the dehydrogenation reaction cannot be sufficiently progressed. On the other hand, even if the metal is loaded exceeding 10% by mass, an effect commensurate with the increase in the amount of metal cannot be obtained. Because.

The dehydrogenation reaction in the dehydrogenation reactor 6 is carried out in the presence of the above-mentioned catalyst for dehydrogenation reaction, LHSV is 0.5 to 4 hr ⁻¹ , reaction temperature is 100 to 450 ° C., preferably 250 to 450 ° C. It is carried out while flowing hydrogen together with the aromatic hydrocarbon hydride under a pressure of normal pressure to 2 MPaG, preferably normal pressure to 0.7 MPaG. The reaction temperature of the dehydrogenation reaction, that is, the average temperature of the dehydrogenation catalyst layer in the reaction tube 62 is appropriately selected according to the temperature of the hydrogen separation membrane described later. Further, the amount of flowing hydrogen is preferably in the range where the molar ratio of hydrogen / aromatic hydrocarbon hydride is 0.01-10. When the dehydrogenation reaction is performed while hydrogen is circulated in this way, side reactions can be suppressed as compared to the case where hydrogen is not circulated, not only can hydrogen be produced efficiently, but also the oil recovered after the dehydrogenation reaction can be reduced. When hydrogenated again and reused as an aromatic hydrocarbon hydride, the amount of impurities contained in the hydride can be reduced. Furthermore, in order to produce hydrogen efficiently, it is preferable to select reaction conditions so that the conversion rate is 85% or more.

  The gas produced by the dehydrogenation reaction is mainly composed of hydrogen, but in addition to this, unreacted aromatic hydrocarbon hydride, aromatic hydrocarbons produced by the dehydrogenation reaction, methane, ethane produced by side reactions, etc. It may contain lower hydrocarbons, alkylcyclopentane produced by side reactions, and the like. However, carbon monoxide contained in the reaction product gas when hydrogen is produced by reforming reaction of city gas, kerosene, naphtha, etc. is not included in the dehydrogenation reaction product gas of aromatic hydrocarbon hydride. .

  The gas produced in the dehydrogenation reactor 6 is supplied to a hydrogen separation device 7 having a hydrogen separation membrane in order to obtain high purity hydrogen. When hydrogen is separated by a hydrogen separation membrane, it is preferable to purify the hydrogen without gas-liquid separation of the reaction product immediately after the dehydrogenation reaction. In this way, energy efficiency can be improved as compared with the conventional technique that requires both cooling and reheating of the dehydrogenation reaction product gas.

  The hydrogen separator 7 is not particularly limited as long as it includes a hydrogen separation membrane. Examples of the hydrogen separation membrane used in the hydrogen separation device 7 include a metal membrane, a ceramic membrane, and a polymer membrane. In consideration of the temperature, pressure, and components contained in the fluid of the dehydrogenation reactor 6, A membrane or a ceramic membrane is preferable, and it is particularly preferable to use a Pd alloy membrane having high hydrogen separation performance. Examples of the Pd alloy film include a Pd—Ag film and a Pd—Cu film. In particular, a Pd—Cu film that can be thinned as a rolled film and has little hydrogen embrittlement is preferable. The Pd—Cu film can be produced, for example, by the method described in US Pat. No. 3,439,474.

  In addition, when using a Pd-Cu membrane for the hydrogen separation membrane of the hydrogen separator 7, the separation membrane temperature is preferably in the range of 250 to 400 ° C. This is because when the temperature of the hydrogen separation membrane is less than 250 ° C., the hydrogen permeation rate is lowered and the hydrogen recovery rate is lowered. Further, when the temperature of the hydrogen separation membrane exceeds 400 ° C., the crystal form of the hydrogen separation membrane changes, the hydrogen permeation rate decreases, and the hydrogen recovery rate decreases.

  The high-purity hydrogen separated through the hydrogen separation membrane of the hydrogen separator 7 can be used as fuel for fuel cells such as fuel cell vehicles or stationary fuel cells. Alternatively, a part of the high-purity hydrogen may be circulated to the dehydrogenation reactor 6 and used as circulating hydrogen necessary for the dehydrogenation reaction. In addition to the high purity hydrogen separated through the hydrogen separation membrane, the circulating hydrogen used in the dehydrogenation reaction is included in the hydrogen introduced from the outside and the unpurified gas of the reaction product gas that exits from the dehydrogenation reactor 6. Hydrogen or hydrogen contained in a gas that has not permeated through the hydrogen separation membrane can be used. However, if the purity of the circulating hydrogen is low, the concentration of the gas other than hydrogen becomes high, and the dehydrogenation reaction is performed under the hydrogen circulation. It is preferable to circulate the high-purity hydrogen obtained by permeating the hydrogen separation membrane to the dehydrogenation reactor 6 because the advantage of performing cannot be sufficiently obtained.

  In addition to the above embodiment, a hydrogen purifier using a gas separation technique such as PSA (Pressure Swing Adsorption) or TSA (Temperature Swing Adsorption) is provided on the downstream side of the gas-liquid separator 9. High purity hydrogen may be produced from a gas that has not passed through the hydrogen separation membrane.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
In the hydrogen production apparatus 1 described above, when the amount of Pt (active metal) in the catalyst layer (volume: 1.4 L) in the reaction tube 62 divides the catalyst layer into three equal parts in the depth direction (reactor 1/3 layer on the inlet side [first layer]) <(1/3 layer in the middle of the reactor [second layer]) <(1/3 layer on the outlet side of the reactor [third layer]) As described above, the reaction tube 62 was filled with a Pt / Al ₂ O ₃ catalyst (average pore diameter: 72.9 kg, and the ratio of the pore volume of 40 to 80 kg to the total pore volume was 60%). Each layer is uniformly filled with the same amount of Pt / Al ₂ O ₃ catalyst with different Pt loading, and the Pt loading of each layer of Pt / Al ₂ O ₃ catalyst is 0 for the first layer. .3% by mass, 0.5% by mass of the second layer, and 0.7% by mass of the third layer. Then, methylcyclohexane (MCH) is used as the aromatic hydrocarbon hydride, the reaction pressure is 0.3 MPaG, the liquid space velocity (LHSV) is 2.0 hr ⁻¹ , and the hydrogen / oil ratio (H ₂ / Oil) is 1.0 mol. The dehydrogenation reaction was performed under the conditions of / mol. Table 1 shows the temperature of each layer, the average temperature of the entire catalyst layer, and the conversion rate.

(Comparative Example 1)
A dehydrogenation reaction was performed in the same manner as in Example 1 except that the entire reactor was uniformly filled with a Pt / Al ₂ O ₃ catalyst having a Pt loading of 0.5% by mass. Table 1 shows the temperature of each layer, the average temperature of the entire catalyst layer, and the conversion rate.

From Example 1 in Table 1, the average catalyst concentration of the catalyst layer was determined as follows: (1/3 layer on the reactor inlet side) <(1/3 layer in the middle of the reactor) <(1/3 on the reactor outlet side) It can be seen that the dehydrogenation conversion rate is improved by making the average catalyst concentration of the portion 1/3 from the inlet side of the catalyst layer lower than the average catalyst concentration of the entire catalyst layer. On the other hand, it can be seen from the results of Comparative Example 1 that the conversion rate in the dehydrogenation reactor using the reaction tube uniformly packed with the catalyst is significantly lower than that in Example 1.

It is a schematic diagram which shows an example of the hydrogen production apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogen production apparatus 2 Tank 3 Pump 4 Primary vaporizer 5 Secondary vaporizer 6 Dehydrogenation reactor 7 Hydrogen separation apparatus 8 Condenser 9 Gas-liquid separation apparatus 10 Recovery oil tank 11 Heating medium supply apparatus 61 Reaction area 62 Reaction tube 63 Baffle plate

Claims (3)

An apparatus for producing hydrogen from a hydride of an aromatic hydrocarbon using a dehydrogenation reaction,
A dehydrogenation reactor having an inlet through which the hydride flows in and an outlet through which a product of the dehydrogenation reaction flows out, and in which a catalyst layer of a dehydrogenation catalyst is provided;
The average catalyst concentration, which is the amount of a substance having catalytic activity per unit volume, in the 1/3 portion from the inlet side of the catalyst layer has the catalytic activity existing per unit volume of the entire catalyst layer. An apparatus for producing hydrogen, which is lower than an average catalyst concentration which is an amount of a substance .   2. The hydrogen production apparatus according to claim 1, wherein an average catalyst concentration in a portion of ３ from the inlet side of the catalyst layer is 0.3 to 0.7 times an average catalyst concentration of the entire catalyst layer. A method for producing hydrogen from a hydride of an aromatic hydrocarbon using a dehydrogenation reaction,
Supplying a raw material containing the hydride to a hydrogen production apparatus including a dehydrogenation reactor;
Performing a dehydrogenation reaction of the hydride in the dehydrogenation reactor;
Removing the product of the dehydrogenation reaction containing at least hydrogen;
The hydrogen production apparatus according to claim 1 or 2, wherein the hydrogen production apparatus is the hydrogen production apparatus according to claim 1 or 2.

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