TWI501920B - Production method and apparatus for hydrogen - Google Patents

Description

Hydrogen manufacturing method and device

The present invention relates to a process for producing hydrogen by a reaction system comprising at least a mixed raw material of hydrocarbon and water by at least steam reforming in the presence of a reforming catalyst, using CuO alone catalyst as the above A method of producing hydrogen from a recombination catalyst. In particular, the present invention relates to a process for producing hydrogen from a mixed raw material containing hydrocarbon, oxygen and water by autothermal reforming comprising a partial oxidation recombination reaction and a vapor recombination reaction. Furthermore, the present invention relates to a hydrogen production apparatus for carrying out the hydrogen production method of the above modes.

As a method of industrially producing hydrogen, an autothermal reforming method combining a partial oxidation method and a vapor recombination method is known. In this autothermal recombination method, hydrocarbon is used as a source of hydrogen generation. In the partial oxidation process, hydrogen and carbon dioxide are produced from hydrocarbons and oxygen by a partial oxidation recombination reaction of an exothermic reaction. On the other hand, in the steam reforming process, hydrogen and carbon dioxide are generated from hydrocarbons and water by a vapor recombination reaction of an endothermic reaction. The autothermal recombination method balances the exothermic amount derived from partial oxidation recombination with the endothermic amount derived from vapor recombination, and ideally requires no external heating to carry out a thermoreactive type recombination reaction. For example, when methanol is used as the hydrocarbon, the reaction formula of the partial oxidation recombination reaction and the vapor recombination reaction is represented by the following formulas (1) and (2).

CH ₃ OH+1/2O ₂ →2H ₂ +CO ₂ + exothermic ‧‧‧(1)

CH ₃ OH+H ₂ O→3H ₂ +CO ₂ + endotherm ‧‧‧(2)

Any of these reactions are carried out by recombination of the catalyst. In the autothermal recombination method, a copper/zinc containing catalyst (Cu/ZnO catalyst) is generally used. The Cu/ZnO catalyst can be obtained by reducing CuO/ZnO catalyst (copper oxide/zinc oxide catalyst) or the like, and the catalyst efficiency is improved by increasing the specific surface area, for example, alumina of fine powder. As a dispersing agent, it is used in a state of being formed into a small particle shape.

In the autothermal recombination method, if the endothermic reaction represented by the above formula (2) occurs in the vicinity of the exothermic reaction represented by the above formula (1), it is considered that the heat transfer efficiency is good. Therefore, it is attempted to simultaneously carry out a partial oxidation recombination reaction and a vapor recombination reaction by a common recombination catalyst. However, in practice, the partial oxidation recombination reaction is faster than the vapor recombination reaction. Therefore, for example, when a mixed raw material containing a hydrocarbon and oxygen and water is supplied to the reforming reactor, the partial oxidation recombination reaction occurs more preferentially than the vapor recombination reaction on the upstream side of the gas passage in the recombination reactor, resulting in partial overproduction. The temperature rises. As a result, it becomes a recombination catalyst in an excessively high temperature region, and the catalyst activity due to a decrease in specific surface area due to sintering is impaired, and it is difficult to continue the autothermal recombination reaction for a long period of time. On the other hand, in the downstream side of the gas passage in the recombination reactor, the vapor recombination reaction due to the endothermic reaction is more preferential than the partial oxidation recombination reaction, and the temperature is gradually lowered. Here, since the steam recombination reaction is sufficiently carried out in the autothermal recombination reaction, it is estimated that the heat absorption amount derived from the vapor recombination reaction tends to be excessively high in the high temperature region when the heat is derived from the exothermic heat derived from the partial oxidation recombination reaction. . In order to achieve an autothermal recombination reaction, a partially excessively high temperature region is inevitably produced.

In order to reduce the activity of the catalyst at a high temperature, it is proposed to suppress the decrease in the activity of the catalyst and improve the durability of the recombination catalyst by using a composite recombination catalyst in which a metal such as a noble metal is added to the Cu/ZnO catalyst. Method (for example, refer to Patent Documents 1 and 2).

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-79101

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-144931

However, in practice, the problems in the autothermal recombination method cannot be sufficiently solved by the above composite recombination catalyst. That is, with the above composite recombination catalyst, there was no significant improvement in durability in an excessively high temperature region generated by the partial oxidation recombination reaction. Further, the composite recombination catalyst has a lower reaction selectivity with respect to the vapor recombination reaction than a general Cu/ZnO catalyst, and the hydrogen generation efficiency is lowered, and there is a problem that an undesired by-product is likely to be generated. Further, the above composite recombination catalyst itself is also inexpensive and not suitable.

The present invention is considered in the above circumstances, in the presence of a recombination catalyst, in the production of hydrogen by autothermal recombination, in order to prevent a decrease in catalytic activity, the autothermal recombination reaction is continued for a long time. purpose.

According to a first aspect of the present invention, there is provided a method for producing hydrogen gas, which is a method for producing hydrogen gas by a reaction system containing at least a vapor reforming reaction in the presence of a recombination catalyst, comprising at least a mixed raw material of a hydrocarbon and water. The recombination catalyst is made up of CuO alone catalyst. In particular, in the present invention, the mixed raw material further contains oxygen, and the reaction is particularly excellent when the partial oxidation recombination reaction and the vapor recombination reaction are carried out in the presence of the recombination catalyst.

The present inventors have made efforts to solve the above problems, and have found that the present invention can be suitably carried out using a CuO single catalyst as a recombination catalyst in an autothermal recombination reaction. That is, based on the conventional knowledge, it is considered that the Cu/ZnO catalyst is suitable for the vapor recombination reaction, and attempts have been made to improve the addition of other metal species based on the Cu/ZnO catalyst. Contrary to these prior knowledge, the inventors have unexpectedly discovered that a CuO alone catalyst can be applied to a recombination catalyst as a vapor recombination reaction. Therefore, when a CuO alone catalyst was used as the recombination catalyst in the autothermal recombination reaction, even if a high-temperature region derived from the partial oxidation recombination reaction was generated, no good result of a decrease in catalytic activity was observed after a long period of time.

Preferably, the recombinant catalyst is supported on a carrier selected from the group consisting of alumina, cerium oxide, zeolite and activated carbon.

Preferably, the above hydrocarbons are selected from the group consisting of methanol, ethanol, dimethyl ether, methane, propane and butane.

When the hydrocarbon is methanol, it is preferred that the molar ratio of water to methanol in the mixed raw material is from 1.5 to 2.0.

When the hydrocarbon is methanol, preferably, the ratio of the partial oxidation recombination reaction is 20 to 30%, and the ratio of the vapor recombination reaction is 80 to 70%, and methanol, oxygen and water in the mixed raw material are selected. proportion. More specifically, the ratio of the hydrocarbon, oxygen, and water in the mixed raw material is selected such that the ratio of the partial oxidation recombination reaction is 20 to 30%, and the ratio of the vapor reforming reaction is 80 to 70%.

According to a third aspect of the present invention, there is provided a hydrogen production apparatus comprising a recombination reactor having a gas passage through which a recombination catalyst is disposed, comprising a mixed raw material comprising a hydrocarbon, oxygen and water, via partial oxidation recombination reaction and steam recombination A hydrogen production apparatus for generating a reformed gas containing hydrogen, which is composed of CuO alone catalyst. The production method of the first aspect of the present invention can be suitably carried out by using the hydrogen production apparatus constructed in this manner.

Other features and advantages of the present invention will become more apparent from the following detailed description.

Fig. 1 is a view showing the schematic configuration of a recombination reactor 1 which is a main part of the hydrogen production apparatus of the present invention. The recombination reactor 1 is a mixture of a hydrocarbon containing a gasified state, and a hydrogen-containing gas is produced by a combination of a partial oxidation recombination reaction and a vapor recombination reaction. The insect group reactor 1 includes a tube body 2 and a recombination reaction unit 3.

The tubular body 2 has a closed-end tubular structure, and a raw material introduction port 21 is provided at the upper end thereof, and a reformed gas outlet port 22 is provided at the lower end thereof. Thereby, in the inside of the pipe body 2, the gas from the material introduction port 21 to the reformed gas outlet port 22 flows to form a passage. The tubular body 2 is made of, for example, stainless steel.

The recombination reaction unit 3 is a portion in which the recombination catalyst is filled in the gas passage inside the tubular body 2, and is defined by the tubular body 2 and one of the inner sides of the tubular body 2 in the high direction. The filled recombination catalyst is a particulate catalyst substantially formed of CuO alone, for example, supported on an alumina carrier. The partition member 4 can be formed into a perforated sheet by enclosing a recombination catalyst while passing through a mixed raw material or a reformed gas which has been vaporized.

In the reforming reactor 1 having the above configuration, the mixed raw material is introduced into the tubular body 2 through the raw material gas introduction port 21 via the operation of the hydrogen producing apparatus including the reforming reactor 1. The mixed raw material contains hydrocarbons, oxygen, and water, and is heated in advance in a vaporizer (not shown) to be in a vaporized state. In the gasifier, the recombination reaction of the subsequent recombination reactor 1 is heated to a desired reaction temperature (for example, 200 to 260 ° C) as necessary. Examples of the hydrocarbon include methanol, ethanol, methyl ether, methane, and butane. Hereinafter, the case of using methanol as a hydrocarbon will be described. The oxygen source contained in the mixed raw material may be air or an oxygen-rich gas (the oxygen concentration is higher than that of air).

The mixed raw material supplied to the gasification state of the reforming reactor via the raw material gas introduction port 21 is led to the reformed gas outlet 22 through the recombination reaction unit 3 in the tubular body 2. The recombination reaction unit 3 is heated to a temperature (for example, 220° C. or higher) necessary for the initial partial oxidation recombination reaction via, for example, a heater (not shown) provided to surround the periphery of the tube body 2. In the recombination reaction section 3, by the action of a recombination catalyst (CuO alone catalyst), the partial oxidation recombination reaction of the exothermic reaction methanol and the vapor recombination reaction of the endothermic reaction methanol are simultaneously performed, and the mixed raw material containing hydrogen is produced. Recombinant gas.

Specifically, in the recombination reaction unit 3, a partial oxidation recombination reaction of methanol is mainly performed on the upstream side. That is, an exothermic reaction represented by the following formula (1) occurs by oxidation of a CuO catalyst. Since the partial oxidation recombination reaction is relatively fast in response, on the upstream side of the recombination reaction unit 3, the temperature rises rapidly due to the reaction, and an excessively high temperature region is generated.

CH ₃ OH+1/2O ₂ → 2H ₂ +CO ₂ + exothermic ‧‧‧(1)

On the other hand, on the downstream side of the recombination reaction unit 3, a steam recombination reaction of methanol is mainly carried out. That is, the endothermic reaction represented by the following formula (2) occurs by the action of the CuO catalyst. More specifically, the reaction of the formula (2) is a reaction of two stages of the reaction represented by the following formula (3) and the reaction represented by the following formula (4) (CO shift reaction).

CH ₃ OH+H ₂ O → 3H ₂ +CO ₂ + endotherm ‧‧‧(2)

CH ₃ OH → H ₂ +CO + endotherm ‧‧‧(3)

CO+H ₂ O → H ₂ +CO ₂ + exothermic ‧‧‧(4)

In the present embodiment, the partial oxidation oxidative recombination reaction and the vapor recombination reaction are regulated by appropriately adjusting the mixing ratio of methanol, oxygen, and water introduced into the recombination reaction unit 3, and the temperature of the recombination reaction unit 3 can be maintained within a predetermined range. Inside. That is, in the recombination reaction section 3, an autothermal recombination reaction is carried out.

In the autothermal recombination reaction of methanol, the proportion of partial oxidative recombination reaction and steam recombination reaction is the same as the heat balance per 1 mol of exotherm of methanol consumption in the partial oxidation oxidative recombination reaction and the methanol consumption in the steam recombination reaction. In the calculation of the mode, the proportion of the partial oxidation recombination reaction is about 20%, and the proportion of the vapor recombination reaction is about 80%. This assumes that the exothermic heat via the partial oxidation recombination reaction is all spent on the theoretical proportion of the endotherm of the vapor recombination reaction. However, actually, the temperature of the mixed raw material introduced into the gasification state of the recombination reactor 1 or the heat released to the outside by the recombination reactor 1 is also entangled as a condition factor for the heat calculation. In this case, since the vapor recombination reaction of the endothermic reaction proceeds sufficiently, the amount of heat dissipated from the partial oxidation recombination reaction must be slightly larger than the theoretical value, and the mixing ratio of oxygen is slightly higher than the theoretical value to adjust the partial oxidation recombination reaction. The ratio is about 20 to 30%, and the proportion of the steam recombination reaction is preferably about 80 to 70%. Further, regarding the steam recombination reaction, the reaction ratio of water to methanol is theoretically a molar ratio of 1:1 according to the above formula (2), but actually, a side reaction is likely to occur when the vapor is insufficient. Therefore, it is preferable to use a condition in which the vapor is excessive compared to the theoretical value. However, when the proportion of steam is too high, the mixing ratio of water to methanol in the mixed raw material (Steam By Methanol: S/M ratio) is preferably about 1.5 to 2.0 (mol/mol).

The reformed gas containing hydrogen gas generated in the recombination reactor 1 of this mode is purified by an appropriate method. When a chemical method is used, for example, a reforming gas mainly containing hydrogen, carbon dioxide, or carbon monoxide is treated with an alkali solution to remove carbon dioxide and carbon monoxide. Further, when air is used as the oxygen source for the mixed raw material, from the viewpoint of efficiently removing nitrogen gas, for example, a plurality of adsorption columns packed with an adsorbent that selectively adsorbs nitrogen are used to carry out PSA gas separation to remove nitrogen gas. The hydrogen can be concentrated.

In the present embodiment, in the autothermal recombination reaction, the partial oxidation recombination reaction represented by the above formula (1) is carried out until the oxygen in the system is substantially completely consumed. The vapor recombination reaction represented by the above formula (2) is carried out in the same manner as or in parallel with the partial oxidation recombination reaction. When a CuO alone catalyst is used as the recombination catalyst, the reaction temperature (for example, 250 ° C or higher) is ensured to be suitable for the vapor recombination reaction by adjusting the conditions, for example, the methanol reaction rate of the first stage represented by the above formula (3) is 99. % or more, the CO fluctuation reaction rate in the second stage represented by the above formula (4) may be 95% or more. That is, it is considered that the selectivity of the CuO single catalyst in the two-stage reaction of the vapor recombination reaction is excellent, and the recombination catalyst as the vapor recombination reaction also has catalytic properties comparable to the Cu/ZnO catalyst in the net. Further, in the recombination catalyst of the present embodiment, since CuO is supported on a unit catalyst such as alumina alone, the preparation method is relatively easy, and it is also advantageous in terms of the raw material price.

Further, the recombination catalyst (CuO alone catalyst) of the present embodiment is used in an oxide state of metallic copper (Cu), and is more stable than physical properties of Cu. Therefore, CuO alone catalyst is less prone to sintering than Cu/ZnO catalyst, and also has durability at high temperatures. In this way, the recombination catalyst (CuO alone catalyst) of the present embodiment can be used as a catalyst for a long period of time in both the partial oxidation recombination reaction in which the high temperature region is easily adsorbed and the vapor recombination reaction in the endothermic reaction. performance. In addition, compared with the conventional Cu/ZnO catalyst method, a fine powder of alumina or the like is used as a dispersing agent to form a small granular shape, and it is expected to be high in that it is less likely to be pulverized by heat history. Life expectancy. In other words, when the hydrogen gas of the present embodiment is produced by using CuO alone catalyst as a recombination catalyst, the autothermal recombination reaction in which the partial oxidation recombination reaction and the vapor recombination reaction are combined can be carried out appropriately over a long period of time, and hydrogen can be increased. The efficiency of the generation.

Further, according to the present embodiment, since the long-term catalyst life can be expected in the autothermal recombination reaction, and the generated reformed gas is subjected to hydrogen separation by the PSA gas separation method, the PSA gas separation device can be stably operated continuously for a long period of time. Therefore, it is better.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the above embodiments. The specific constitution of the recombination reactor of the present invention and the hydrogen production method of the present invention may be variously changed without departing from the scope of the inventive concept.

The recombination catalyst (CuO alone catalyst) used in the present invention may be in a form not supported on an alumina carrier, or may be a carrier supported on alumina (for example, cerium oxide, zeolite or activated carbon). )By.

Next, the usefulness of the present invention will be described by way of examples and comparative examples.

[Example 1]

In the present embodiment, a recombination reactor 1 (Fig. 1) of the following specific specifications was used, and a reformed gas containing hydrogen was produced from a mixed raw material composed of methanol and air.

The tube body 2 of the recombination reactor 1 was composed of a stainless steel tube (inner diameter: 23 mm, full length: 400 mm). The recombination reaction unit 3 was filled with a granular catalyst (particle diameter: 1.2 to 2.5 mm) which was supported by alumina as a catalyst for the recombination catalyst by a CuO single catalyst. Here, the recombination reaction portion 3 is disposed such that its upper end is lowered by 110 mm from the upper end of the stainless steel pipe. Furthermore, an electric heater (maintaining a temperature of 250 ° C) surrounding the periphery of the stainless steel tube was disposed.

The supply amount of the mixed raw material supplied to the reforming reactor 1 was 4.96 mol/h for methanol, 7.44 mol/h for water (S/M ratio = 1.5), and 76.71 dm ³ N/h for air (converted to pure oxygen of 0.72). The flow rate of mol/h). The mixed raw material is supplied to the reforming reactor 1 after being heated to a vaporized state in a gasifier. The temperature at which the raw material was mixed at the time of introduction of the reforming reactor 1 was 260 °C. The pressure in the recombination reactor 1 was maintained at 800 kPa (pressure gauge).

In this example, investigation of normal operation (mixing of the recombination reactor 1) The temperature distribution of the reaction portion 3 was recombined after about 5 hours from the start of introduction of the raw material. The investigation of the temperature fraction is performed by measuring the temperature of a plurality of measurement points set in the recombination reaction unit 3. The measurement point is set in the recombination reaction unit 3 along a central axis in accordance with the gas flow direction, and a reconfigurable reaction unit 3 is provided with a movable thermometer along the central axis. Therefore, the plurality of measurement points on the central axis of the measurement unit of the thermometer are sequentially shifted, and the temperature of the measurement point is measured. The measurement results are shown in Fig. 2. The horizontal axis of the same figure indicates the measurement point, and the upstream end (upper end) of the recombination reaction unit 3 is used as a base point and is expressed by the amount of displacement in the gas flow direction. The vertical axis of the same graph indicates the measured temperature of the measurement point.

The reformed gas derived from the recombination reactor 1 was cooled to room temperature using a heat exchanger, and the condensed liquid component was separated and removed by a gas-liquid separator, and then analyzed by composition using a gas chromatography apparatus. The analysis of the reformed gas is carried out by using the above-mentioned reformed gas obtained during normal operation. The composition of the reformed gas was about 63% of that of the main component, and carbon dioxide, nitrogen, carbon monoxide, and argon were also confirmed, but by-products such as methane or dimethyl ether were not confirmed. Further, the overall reaction rate (total methanol reaction rate) was 99.5% with respect to the amount of methanol to be charged, and it was considered that all of the methanol to be charged was consumed by the reaction. The CO fluctuation reaction rate also gave good results of 96.8%.

[Comparative Example 1]

In the comparative example, the same recombination reactor 1 as in Example 1 was used, and in the same raw material supply state as in Example 1, the oil-mixed raw material was used to produce a reformed gas containing hydrogen. However, as the recombination catalyst charged to the recombination reaction unit 3, the C _u /ZnO catalyst was used instead of the recombination catalyst to which the first embodiment was applied. This recombination catalyst is a fine powder of alumina added as a dispersing agent to Cu/ZnO, and is subjected to press molding and then sintered. In the comparative example, the temperature distribution of the recombination reaction unit 3 was measured in the same manner as in the first embodiment. The measurement results are shown in Fig. 2.

In the comparative example, the results of the components of the condensate and the reformed gas derived from the recombination reactor 1 during the normal operation were analyzed in the same manner as in Example 1, and the total methanol reaction rate was 98.8%, and the CO fluctuation reaction rate was 96.1%. Further, the composition of the reformed gas was about 62% of that of the main component, and carbon dioxide, nitrogen, carbon monoxide, and argon were also confirmed, but by-products such as methane or dimethyl ether were not confirmed.

From the results of the first embodiment and the comparative example 1, it is understood that the CuO alone catalyst is used as a recombination catalyst in the autothermal recombination method, and similarly to the Cu/ZnO catalyst, temperature regulation in the recombination reactor can be performed, and confirmation can be confirmed. It has excellent catalyst properties comparable to Cu/ZnO catalyst.

[Comparison of durability of recombination catalyst]

The durability test of the catalyst performance was carried out under the same conditions as in Example 1 and Comparative Example 1 using the recombination catalyst (CuO alone catalyst and Cu/ZnO catalyst) used in the above Examples and Comparative Examples. The results are shown in Fig. 3, and the horizontal axis represents the operation time (the elapsed time from the start of the recombination of the recombination gas by the recombination reactor 1), and the slave axis indicates the total methanol reaction rate at the elapse of the operation time. In the case of the CuO alone catalyst of the present invention, the methanol reaction rate at the time of passage of 700 hours is also maintained at a value of about 99%. On the other hand, in the case of the Cu/ZnO catalyst, the total methanol reaction rate showed a value of about 99% higher at the beginning of the operation, but showed a tendency to gradually decrease as time passed, and decreased at the time of passage of 700 hours. Up to 80%. In the case of using any of the catalysts, the peak temperature in the high temperature region of the recombination reaction unit 3 is about 400 ° C. It is considered that the Cu/ZnO catalyst is degraded by the catalytic activity through sintering, and the total methanol reaction rate is lowered.

1. . . Recombination reactor

2. . . Tube body

3. . . Recombination reaction department

4. . . Spacer

twenty one. . . Raw material gas inlet

twenty two. . . Recombinant gas outlet

Fig. 1 is a cross-sectional view showing a schematic structure of a reforming reactor constituting a main part of the hydrogen producing apparatus of the present invention.

Fig. 2 is a graph showing the temperature distribution of the recombination reactor in the examples and comparative examples of the present invention.

Figure 3 is a graph showing the durability of the recombination catalyst.

1. . . Recombination reactor

2. . . Tube body

3. . . Recombination reaction department

4. . . Spacer

twenty one. . . Raw material gas inlet

twenty two. . . Recombinant gas outlet

Claims (5)

A method for producing hydrogen, comprising: at least a mixed raw material of methanol and water, producing hydrogen by a reaction system in which at least a recombination reaction is carried out by a recombination reaction unit of a recombination reactor filled with a recombination catalyst, wherein the mixed raw material further contains oxygen, wherein The recombination catalyst is composed of a CuO single catalyst which is subjected to a partial oxidation reaction of methanol on the upstream side of the recombination reaction unit and performs a vapor recombination reaction on the downstream side of the recombination reaction unit. The ratio of the oxidative recombination reaction is 20 to 30%, and the ratio of the vapor recombination reaction is 80 to 70%, and the ratio of methanol, oxygen, and water in the mixed raw material is selected. The method for producing hydrogen according to the first aspect of the invention, wherein the recombination catalyst is supported on a carrier selected from the group consisting of alumina, cerium oxide, zeolite and activated carbon. The method for producing hydrogen according to the first aspect of the invention, wherein the molar ratio of water to methanol in the mixed raw material is from 1.5 to 2.0. The method for producing hydrogen according to claim 1, wherein the mixed raw material is selected such that the amount of heat generated from the partial oxidation recombination reaction is substantially equal to the amount of heat absorbed from the vapor recombination reaction. The ratio of hydrocarbons, oxygen and water. A hydrogen production apparatus comprising a recombination reactor having a gas passage equipped with a recombination catalyst, wherein the recombination reaction is carried out by a partial oxidation reaction of the upstream side of the recombination reaction unit by a mixed raw material containing methanol, oxygen and water. The downstream side of the part is subjected to a steam recombination reaction to produce a a reformed gas of hydrogen, wherein the recombination catalyst is composed of CuO alone catalyst, and the ratio of the partial oxidation recombination reaction is 20 to 30%, and the ratio of the vapor recombination reaction is 80 to 70%. The ratio of methanol, oxygen and water in the mixed raw material.