JP4301362B2 - Lower hydrocarbon direct cracking catalyst, lower hydrocarbon direct cracking reactor, and lower hydrocarbon direct cracking reactor - Google Patents

Description

  The present invention relates to a technical field for producing high-purity hydrogen and nano-size functional carbon by directly decomposing lower hydrocarbons such as methane, and the fine particles of carbon are generated in situ. The present invention relates to a catalyst in which the support is deformed, in particular, a similar expansion characteristic, a lower hydrocarbon direct cracking reactor containing the catalyst, and a lower hydrocarbon direct cracking reaction apparatus including the catalyst.

Conventionally, the catalyst used for the direct decomposition reaction of methane and lower hydrocarbons is such that a catalytic metal such as nickel is supported on a particulate carrier made of a material such as silica or alumina or a porous monolith carrier having a honeycomb shape or the like. Have been prepared. For example, in the “carbon dioxide fixing device” disclosed in Patent Document 1, a catalyst that decomposes methane using SiO ₂ or Al ₂ O ₃ as a carrier and Ni, Co, or the like as a catalyst metal is used. Yes. The material of the porous monolith support of the catalyst is not limited to inorganic materials. Further, for example, in “hydrocarbon decomposition catalyst and hydrogen production method using the same” disclosed in Patent Document 2, a nickel compound, an alkali metal, an alkaline earth metal, and the like are used with a carbonaceous material such as fullerene as a carrier. A methane direct cracking catalyst is prepared by supporting it.

Although the direct decomposition process of methane and lower hydrocarbons is still a research and development technology and may be disputed as being taken up as a conventional technology, the direct decomposition reaction of methane will be described here as an example.
In the methane direct decomposition reaction, hydrogen and carbon are produced by bringing methane, which is a raw material, into contact with the methane and hydrocarbon decomposition catalyst in a reaction tube in a temperature range of about 300 to 900 ° C. and thermally decomposing them. is there. The carbon produced by the reaction stays inside the reaction tube together with the catalyst, and the gas components are only hydrogen and unreacted methane. Since carbon accumulates in the vicinity of the catalyst as the reaction proceeds, if the reaction tube is installed vertically and filled with catalyst particles, the pressure loss increases and the reaction tube closes quickly. Therefore, it is necessary to devise measures to prevent this, and in the experiment at the laboratory stage, there is a method in which a reaction tube is installed sideways, catalyst particles are placed on the bottom, and an appropriate space corresponding to the volume increase due to carbon accumulation is left on the top. In experiments that are frequently used and put into practical use, a fluidized bed reactor is used in which reaction tubes are installed vertically and catalyst particles are moved so that methane gas can pass through the gaps.
JP 2000-226205 A Japanese Patent No. 2838192

  However, in the conventional horizontal system, (1) the distribution of the catalyst particles is non-uniform, (2) the location of the reactor in the methane direct cracking device is limited, (3) contact between methane gas and the catalyst There are problems such as poor efficiency. In addition, in the conventional fluidized bed reactor method, it is necessary to maintain the fluidized state by keeping the size and weight of the catalyst particles in a certain range. (1) The catalyst / carbon mixture is periodically extracted outside the reactor, There are problems such as a device for supplying a new catalyst, work is indispensable, and (2) catalyst utilization efficiency is low.

  The present invention was made to solve the problems of the above-described method of placing the reaction tube horizontally, placing catalyst particles at the bottom, and leaving an appropriate space at the top, and the problem of the fluidized bed reactor method. The catalyst for lower hydrocarbon direct cracking reaction and the lower hydrocarbon direct cracking reactor capable of allowing the reaction to proceed stably for a predetermined time regardless of the catalyst installation method and requiring no special operation such as flow, and An object is to provide a lower hydrocarbon direct cracking reaction apparatus.

In order to solve the above problems, among the catalysts for direct decomposition reaction of lower hydrocarbons of the present invention, the invention according to claim 1 is characterized in that a catalyst material is supported on a porous carrier, A catalyst used in a reaction for producing pure hydrogen and nano-size functional carbon, wherein the support has a three-dimensional network structure and is similarly expanded and deformed by accumulation of the carbon generated by the direct decomposition reaction. And has a function of ensuring air permeability.

The invention for a catalyst for direct decomposition reaction of lower hydrocarbon according to claim 2 is the invention according to claim 1 , wherein the surface of the carrier is provided with an uneven surface layer formed of surface ceramic particles, and the uneven surface layer The catalyst material is supported on the substrate.

The invention for a catalyst for direct cracking of a lower hydrocarbon according to claim 3 is the invention according to claim 1 or 2 , wherein the catalyst material is nickel, iron, cobalt, or a mixture thereof. And

The invention for a catalyst for direct cracking of lower hydrocarbon according to claim 4 is characterized in that, in the invention according to any one of claims 1 to 3 , the nano-sized functional carbon has a shape other than bulk carbon. To do.

The invention of a lower hydrocarbon direct cracking reactor according to claim 5 has a reactor body provided with a gas inlet and a gas outlet, and the catalyst according to any one of claims 1 to 4 is placed in the reactor body. It is housed, and has a structure in which the gas inlet is detachably connected to an external lower hydrocarbon supply unit and the gas outlet is detachably connected to an external post-reaction gas intake unit.

The invention of a lower hydrocarbon direct cracking reaction apparatus according to claim 6 comprises the lower hydrocarbon direct cracking reaction catalyst according to any one of claims 1 to 4 and supplies lower hydrocarbons to the catalyst. A hydrogen supply unit, and a post-reaction gas intake unit into which a reaction gas generated by the direct decomposition of lower hydrocarbons by the catalyst and an unreacted gas are provided.

Invention of lower hydrocarbons directly decomposition reaction apparatus according to claim 7 is the invention of claim 6, wherein the lower the hydrocarbon feed section, a lower hydrocarbon direct decomposition reaction catalyst is housed the reactor gas inlet The post-reaction gas intake part has a structure in which a gas outlet of the reactor is connected to be detachably ventilated.

The invention of the lower hydrocarbon direct cracking reaction apparatus according to claim 8 is characterized in that, in the invention according to claim 7 , the reactor is detachable in a cartridge system.

That is, according to the catalyst for direct decomposition reaction of lower hydrocarbons of the present invention, the catalyst material is supported on the porous carrier, and by supplying the lower hydrocarbons to the catalyst, many holes of the carrier function as vent holes. Then, the lower hydrocarbon and the catalyst material are effectively brought into contact with each other to cause direct decomposition of the lower hydrocarbon to produce high-purity hydrogen and nano-size functional carbon. The carbon produced with the decomposition of the lower hydrocarbons gradually accumulates in the carrier, and by deforming the carrier due to this accumulation, the pressure loss in the pores of the carrier is increased and the blockage is suppressed, thereby providing good air permeability. It is possible to maintain good performance as a catalyst over a long period of time while ensuring. Then, the reaction can proceed smoothly until the porous composite in which the catalyst and carbon are united with each other fills the interior of the reactor or the like.
The carrier expands similarly as a characteristic deformation. When the catalyst expands in a similar manner, the diameter of the continuous air vent is rather widened so that it is not blocked by the carbon fine particles. In addition, the composite of the catalyst and carbon expanded while leaving the characteristics of the shape of the original catalyst has a mechanical strength that does not cause self-collapse. Therefore, a catalyst having a predetermined shape can be accommodated in a vertical reactor or the like, and there are few restrictions on arrangement.

A carrier having a three-dimensional network structure (for example, SOLACLEA (trade name) manufactured by Noritake Company Limited) is used as the carrier that performs the above function. The carrier having this three-dimensional network structure can be obtained by, for example, an array of ceramic fibers. The method for producing the three-dimensional network structure carrier is not particularly limited, and can be obtained by an appropriate method. For example, a three-dimensional network structure may be obtained by bonding the intersections of fibers serving as a carrier, or a monolith carrier may be obtained by molding the carrier in a mold having a three-dimensional network structure. In the three-dimensional network structure, the force of carbon growing in the voids inside the carrier is stronger than the bonding force between the particles constituting the carrier, and the voids are expanded. A similar expansion occurs. At this time, since the pore diameter of the carrier pores gradually increases, the pore clogging due to the carbon fine particles and the increase in pressure loss are reliably suppressed. The diameter and the mesh size of the ceramic fiber can be appropriately determined in consideration of the air permeability, the contact area between the catalyst material and the gas, the deformability due to carbon accumulation, and the like.

  A catalyst material made of nickel, iron, cobalt or a mixture thereof is supported on the carrier. The catalyst material may be supported by fixing the catalyst material on the surface of the carrier. In addition, when the carrier is produced, the catalyst material is mixed with the carrier so that the catalyst material is mixed with the carrier. It may be manufactured at the same time. The catalyst material can be fixed to the support surface by an impregnation method, a precipitation method, an ion exchange method, or a method not limited to these methods. Furthermore, in order to increase the effective surface area of the catalyst, an uneven surface layer may be formed on the surface of the support having a three-dimensional network structure with ceramic particles for the surface layer, and the catalyst material may be supported on the uneven surface layer.

  The catalyst is often housed in a reactor having a gas inlet and a gas outlet, allowing contact with lower hydrocarbons introduced from the gas inlet and flowing through the reactor, and allowing gas to flow. Yes. The reaction gas generated by the reaction and the unreacted gas are taken out from the reactor through the gas outlet. Although this reactor may be fixed in the lower hydrocarbon direct cracking reaction apparatus, it is desirable that the reactor is removable by making it a cartridge type. As a result, the carbon produced by the reaction is gradually accumulated and the catalyst having a reduced function can be easily replaced, and the functional carbon can be easily recovered. 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.

As described above, according to the present invention, by using a catalyst in which a catalyst material is supported on a porous support that can be similarly expanded and deformed by the accumulation of carbon, carbon fine particles that are products of direct decomposition of lower hydrocarbons can be obtained. Since pressure loss and gas passage blockage due to generation and accumulation can be avoided, it is possible to continue the reaction for a predetermined time, and systematically produce high-purity hydrogen and nano-sized carbon microparticles characterized by a filament shape. There is an effect that can. Also, by using this catalyst as a cartridge type reactor integrated with the reactor, the entire device can be reduced in size and simplified, and there is an effect that no maintenance is required. For example, when compared with a fluidized bed reactor The advantage of is extremely large. In addition, by using the above catalyst, there is provided a novel small-scale hydrogen generator for home use in which there is no CO ₂ emission from the process, the reactor can be installed vertically, and the catalyst can be replaced with the reactor. Make it possible.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the catalyst 1 of this embodiment has, as a catalyst material, catalytic metal fine particles 3 made of nickel, iron, cobalt, or a mixture thereof on a monolithic carrier 2 having a three-dimensional network structure made of ceramic fibers. It is supported. A continuous air passage is secured by a large number of holes 2 a obtained by the mesh of the carrier 2. In FIG. 1, the carrier 2 is shown as having a square hole 2a that is arranged in a simulated manner, but in this embodiment, the hole 2a of the carrier 2 is substantially hexagonal as shown in FIGS. The mesh is also randomly interlaced in three dimensions.

The monolith carrier 2 having the three-dimensional network structure can be manufactured, for example, by the following procedure.
That is, water and a dispersing agent as a solvent are added to ceramic fine powder such as alumina and mixed by stirring to obtain a slurry containing the ceramic fine powder. Next, urethane foam which is an organic porous material having a three-dimensional network structure is put into the slurry, and the slurry is infiltrated into the pores of the urethane foam. This is dried and fired to burn the urethane foam and sinter the ceramic fine powder. As a result, a monolithic carrier 2 of ceramic fibers having a three-dimensional network structure is obtained. In this embodiment, the diameter of the ceramic fiber constituting the carrier 2 is 100 to 1000 μm, and the carrier 2 having a thickness of 5 mm has a mesh with a light transmittance of 30%.

For supporting the catalyst material 3 on the monolith support 2, an appropriate method such as an impregnation method, a precipitation method, or an ion exchange method can be employed. Further, the catalyst material 3 may be supported by mixing the fine powder of the catalyst material 3 with the slurry so that the catalyst material 3 is contained integrally with the carrier 2.
In the catalyst 1, lower hydrocarbons are directly decomposed by contacting with lower hydrocarbons such as methane, and high-purity hydrogen and nano-sized functional carbon C such as filaments and onions, which are different from bulk carbon (see FIG. 3). The nano-sized functional carbon C gradually accumulates on the catalyst 1 and causes the carrier 2 in the catalyst 1 to expand and deform similarly as shown in FIG. At this time, since the diameter of the hole 2a is also increased, an increase in pressure loss and blockage in the hole 2a are suppressed over a long period of time. FIG. 4 shows a catalyst 31 having a conventional honeycomb structure carrier 30. In this catalyst 31, nanosize functional carbon C gradually accumulates in the holes 30 a that are gas flow paths with the progress of the reaction, but the support 30 is hardly deformed structurally, so that the nanosize functional carbon that accumulates. The carbon C gradually increases the pressure loss and eventually closes the hole 30a, which is a gas flow path. In addition, although the expansion | swelling of the whole support | carrier 30 by the uptake | capture of carbon microparticles | fine-particles also occurs slightly, since it occurs unevenly, it will cause collapse of a honeycomb structure.

The catalyst 1 is accommodated in a cylindrical reactor 5 main body as shown in FIG. At that time, the internal volume in the main body of the reactor 5 is sufficiently larger than the volume of the catalyst 1 so that the catalyst can be expanded and deformed. The shape of the reactor 5 is preferably a cylindrical shape, but is not necessarily limited to a cylindrical shape.
A gas inlet 5a and a gas outlet 5b are formed at the ends of the reactor 5, respectively. The gas inlet 5a is an external lower hydrocarbon feed section, and the gas outlet 5b is an external post-reaction gas intake section. It has a structure that allows ventilation connection and is detachable.

  As shown in the system image of FIG. 6, the reaction apparatus 10 including the reactor 5 is connected to a raw material supply pipe 12 to which a raw material methane 11 is supplied as a raw material lower hydrocarbon, and the raw material supply pipe 12 is connected to the reaction apparatus 10. It is connected to the lower hydrocarbon feed section 10a. A gas inlet 5a of the reactor 5 is detachably connected to the lower hydrocarbon supply unit 10a. One end of a post-reaction gas transfer pipe 13 is connected to the reaction apparatus 10, and the post-reaction gas transfer pipe 13 is connected to a post-reaction gas intake portion 10 b in the reaction apparatus 10. A gas outlet 5b of the reactor 5 is detachably connected to the post-reaction gas intake 10b. The other end of the post-reaction gas transfer pipe 13 is connected to a hydrogen / methane separator 14. The hydrogen / methane separator 14 can be constituted by, for example, a hybrid of a hydrogen separator and a methane separator. For example, the hydrogen separation apparatus can be configured by an apparatus that employs an appropriate method such as a membrane separation method that allows PSA or hydrogen to permeate. Similarly, the methane separation apparatus can be constituted by an apparatus including a PSA and a separation membrane.

The methane separation side of the hydrogen / methane separation device 14 is connected to a methane transfer pipe 15, and the methane transfer pipe 15 branches into a fuel pipe 15a and a reflux pipe 15b. The fuel pipe 15a supplies methane to the reaction apparatus 10 so that methane can be used as fuel for the heat required for the reaction of the reaction apparatus 10. The reflux pipe 15 b is connected to the lower hydrocarbon supply pipe 12 of the reaction apparatus 10 to cause the reaction apparatus 10 to reflux methane. In the present invention, the method of using the unreacted gas is not particularly limited, and it may be used for fuel or reflux, or may be used for other reforming.
The hydrogen separation side of the hydrogen / methane separation device 14 is connected to a hydrogen supply pipe 16 that supplies hydrogen to the fuel cell 20. In the present invention, the method of using hydrogen is not particularly limited, and for example, it may be used as fuel or stored.

Next, the operation of the above system of the present invention will be described by taking the direct decomposition of methane as an example.
The catalyst 1 in which the catalytic metal fine particles 3 are supported on the similarly expandable monolith support 2 is heated in the reactor 5 to a temperature of 300 ° C. to 900 ° C. (preferably 500 ° C. to 700 ° C.). It is supplied to the reactor 10 through the supply pipe 12. Methane is supplied into the reactor 5 from the gas inlet 5a through the lower hydrocarbon supply unit 10a in the reactor 10. In the reactor 5, when methane is reacted under a pressure of 1 to 9.99 atm, the hydrogen-carbon bond of methane is broken on the catalytic metal fine particles 3, and the generated hydrogen atoms become hydrogen gas, and carbon atoms Becomes nano-sized carbon fine particles having a special shape different from bulk (bulk) carbon, such as filament-like or onion-like. When filamentous carbon fine particles are produced, the catalyst metal fine particles 3 are often located at the growth end portion. The carbon fine particles not only grow from the outer surface of the catalyst toward the gas phase, but also grow in the voids inside the carrier 2, so when the force is stronger than the bonding force between the particles constituting the carrier 2, the voids are pushed. Will spread. When such a phenomenon occurs uniformly in the entire support 2, similar expansion of the support 2 occurs. At this time, since the pore diameter of the continuous flow hole 2a of the carrier 2 gradually increases, the flow hole 2a is not blocked by the carbon fine particles. That is, in the catalyst 1 using the similarly expandable monolith support 2, the gas flow path is not blocked, and the perforated complex in which the catalyst 1 and carbon C are naturally integrated expands to fill the inside of the reaction tube 5. The reaction can continue to proceed until exhausted.

  The reaction gas (hydrogen) and the unreacted gas (methane) generated in the reactor 5 are discharged from the gas outlet 5b of the reactor 5, and hydrogen / methane is passed through the post-reaction gas intake 10b and the post-reaction gas transfer pipe 13. It is supplied to the separation device 14. In the hydrogen / methane separator 14, methane is separated from the unreacted gas. This unreacted gas methane is, for example, about 50% of the raw material methane 11. A part of the methane transferred through the methane transfer pipe 15 is used for heating the reaction apparatus 10 through the fuel pipe 15a, and the remaining methane is refluxed to the reaction apparatus 10 through the reflux pipe 15b. Improve the conversion efficiency of methane by increasing the direct cracking efficiency. Further, the high purity hydrogen separated from the hydrogen / methane separator 14 is supplied to the fuel cell 20 through the hydrogen supply pipe 16 and used for power generation.

An embodiment of the present invention will be described below.
As a monolithic catalyst 1 that can be expanded in a similar manner, a catalyst in which 1, 5, 10, 15 wt% nickel is supported on SOLACLEA (trademark; hereinafter abbreviated as SOLAC) manufactured by Noritake Company Limited whose ceramic fibers have a three-dimensional network structure. 1 to 15% Ni / SOLAC) of about 0.7 to 0.8 g is placed in a 25 mm diameter quartz straight tube as the reactor 5 under the conditions of a reaction temperature of 600 ° C., a total pressure of 1 atm, and an undiluted methane flow rate of 60 ml / min. Under the direct methane decomposition. The methane conversion at that time is shown in FIG. Although the conversion rate depends on the nickel loading rate, direct decomposition can be performed stably for a long time at a conversion rate of about 60%.

Also, 10 wt% Ni / SOLAC and a honeycomb structure porous ceramic monolith support that cannot be deformed (similar expansion) due to carbon accumulation (Isolite manufactured by Isolite Industry, abbreviated as Iso, Ceramic Honeycomb: abbreviated as CH) The same experiment as above was carried out using a catalyst carrying 5 wt% and 3 wt% of nickel (the nickel content was unified to 1.0 × 10 ⁻³ mol). The results are shown in FIG. From the results, it is apparent that by using SOLAC as the carrier 2, direct methane decomposition occurs stably for a long time as compared with those using other carriers.

Next, as another embodiment, in a system for supplying hydrogen to a household fuel cell according to the system image flow shown in FIG. 6, a 10 wt% Ni (59 g) / SOLAC (531 g) catalyst is reacted at a reaction temperature of 600 ° C. and a total pressure of 1 atm. SV value: 51000 ml / g-Ni / h, methane direct decomposition reaction was performed under the conditions of undiluted methane flow rate 60 ml / min. In this system, by utilizing the fact that the volume of the carrier 2 expands approximately four times before and after the reaction, the initial catalyst volume is 2.3 L, and the reactor 5 in which the catalyst is put is used. The volume was set to 9.2L. As a result, when undiluted methane was allowed to flow at ³ Nm ³ / h (50 l / min), ³ Nm ³ / h of hydrogen could be generated for about 10 hours. Using a 1kW household fuel cell, which is expected to become popular as a current household fuel cell, and generating electricity with 3Nm ³ / h of hydrogen, it is about one day's required electricity for a general household (family of 4) It becomes possible to obtain power of 3 kW.
In addition, since the inside of the reactor 5 is filled with carbon fine particles including the catalyst 1 after a predetermined time has elapsed, it is easy to exchange the catalyst and discharge the carbon fine particles by using a cartridge type reactor in which the catalyst 1 and the reactor 5 are integrated. It can be carried out. In addition, there is a possibility that the volume of this cartridge can be significantly reduced by improving the catalyst and improving the fuel cell performance in the future.

It is a figure which shows typically the catalyst of one Embodiment of this invention. Similarly, it is a partially enlarged view. Similarly, it is a figure which shows the mode of the uniform expansion before and behind performing a methane direct decomposition reaction. It is a figure which shows the mode inside the honeycomb before and behind using the catalyst which made the conventional ceramic honeycomb the support | carrier for methane direct decomposition reaction. Similarly, it is a figure which shows the reactor which accommodated the catalyst. It is a system image flow figure provided with the reaction apparatus of this invention. It is the graph which showed the relationship between the methane conversion rate of a SOLAC carrying catalyst, and a nickel carrying rate. It is the graph which showed the relationship of the methane conversion rate and support | carrier of various nickel catalysts.

Explanation of symbols

1 catalyst 2 carrier 2a hole 3 catalyst metal fine particles (catalyst material)
5 Reactor 5a Gas inlet 5b Gas outlet 10 Reactor 10a Lower hydrocarbon supply part 10b Post-reaction gas intake part 11 Raw material methane

Claims (8)

A catalyst material is supported on a porous carrier, and is a catalyst used in a reaction for producing high-purity hydrogen and nano-sized functional carbon by direct decomposition of lower hydrocarbons. The carrier has a three-dimensional network structure. And a catalyst for direct decomposition reaction of a lower hydrocarbon, characterized by having a function of expanding and deforming similarly due to accumulation of the carbon produced by the direct decomposition reaction and ensuring air permeability. And uneven surface layer formed by the surface ceramic particles provided on the surface of the support, lower hydrocarbons direct decomposition reaction of claim 1 wherein the catalytic material to the irregular surface layer is characterized in that it is carried Catalyst. The catalyst for direct decomposition reaction of a lower hydrocarbon according to claim 1 or 2 , wherein the catalyst material is nickel, iron, cobalt or a mixture thereof. The catalyst for direct decomposition reaction of a lower hydrocarbon according to any one of claims 1 to 3 , wherein the nano-sized functional carbon has a shape other than bulk carbon. A reactor main body having a gas inlet and a gas outlet, wherein the catalyst according to any one of claims 1 to 4 is accommodated in the reactor main body, and the gas inlet is desorbed to an external lower hydrocarbon feed section. A lower hydrocarbon direct cracking reactor characterized by having a structure in which the gas outlet can be vented and connected so that the gas outlet can be vented and connected to an external post-reaction gas intake. 5. A lower hydrocarbon direct cracking reaction catalyst according to any one of claims 1 to 4 , wherein the lower hydrocarbon is directly cracked by the lower hydrocarbon feed section for feeding the lower hydrocarbon to the catalyst and the catalyst. A lower hydrocarbon direct cracking reaction apparatus, comprising a post-reaction gas intake portion into which a reaction gas generated by the reaction and an unreacted gas are taken. The lower hydrocarbon supply unit has a structure in which a gas inlet of a reactor in which a catalyst for direct decomposition reaction of lower hydrocarbons is accommodated is removably connected, and the post-reaction gas intake unit includes the reaction 7. The lower hydrocarbon direct cracking reaction apparatus according to claim 6 , wherein the gas outlet of the vessel is structured to be detachably ventilated. 8. The lower hydrocarbon direct cracking reaction apparatus according to claim 7, wherein said reactor is detachable by a cartridge system.

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