JPS6247578B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a methanol reforming catalyst. Currently, crude oil and refined petroleum products are used as raw materials for producing liquid fuel, gaseous fuel, and reducing gas used in power generation boilers, internal combustion engines, etc. However, due to the recent rise in crude oil prices, In an effort to diversify fuels, methanol, which can be synthesized from fossil fuels other than crude oil, is attracting attention. Furthermore, since methanol is reformed into a gas containing hydrogen and carbon monoxide at a much lower temperature than naphtha, it has the advantage that waste heat can be used as a heat source for reaction heat. The reformed gas generated at this time has the advantage that the calorific value of the reformed gas increases by the amount equivalent to the endothermic amount of the reforming reaction (approximately 22 Kcal/mol), and furthermore, the generated reformed gas has a high octane number and has a high output. When applied to designed internal combustion engines, it has the advantage of increasing the compression ratio and improving thermal efficiency, and enables clean combustion without emitting aldehydes when burning methanol. When carrying out a methanol reforming reaction using the exhaust gas heat of an internal combustion engine, the temperature of the exhaust gas varies from room temperature to about 700℃, so it is difficult to use a device that can be installed in an internal combustion engine over a wide temperature range. With a small amount of catalyst and for example at 700℃ as above
There is a need for a stable catalyst that does not deteriorate its reforming performance even when exposed to moderately high temperatures. Conventionally, as a catalyst for reforming methanol, platinum metal elements such as platinum or base metal elements such as copper, nickel, chromium, zinc, and their oxides are supported on a carrier such as alumina (hereinafter referred to as Al ₂ O ₃ ). However, these catalysts have poor low-temperature activity. Until now, many problems remain, such as lack of heat resistance. Among the conventional catalysts mentioned above, for example, catalysts in which one or more metals from the group consisting of copper, zinc, chromium, and nickel or their oxides are simply supported on an alumina carrier react with methanol even at relatively low temperatures; There are problems in that the selectivity for reforming to hydrogen or carbon monoxide is low, side reactions that produce methane, carbon dioxide, dimethyl ether, etc. are likely to occur, and the catalyst life is short. In particular, for catalysts with nickel or copper supported on alumina supports, NiO
There is a problem in that the specific surface area of the catalyst decreases at the same time as spinel crystals of -Al ₂ O ₃ or CuO-Al ₂ O ₃ are formed. In addition to the catalyst preparation method using the impregnating support method described above, there is also a catalyst preparation method using the precipitation method.A typical example of a catalyst prepared by the latter method is one containing zinc, chromium, and even copper. There is a catalyst for methanol synthesis. This catalyst for methanol synthesis is generally known to be effective in the reaction of reforming methanol into a gas containing hydrogen and carbon monoxide, but its activity is low at low temperatures and side reactions occur. The problem is that it is easy. In order to solve the above problem, the present inventors have carried out extensive experimental studies, and have found that nickel is supported on a carrier made of one or more oxides or hydroxides of one or more of the group consisting of copper, zinc, and chromium. They discovered that the catalyst had high activity and high selectivity, and filed a separate patent application on the same day. However, preparing this catalyst requires two steps: preparing a carrier and supporting nickel, and in order to reduce the manufacturing cost of the catalyst,
It is considered more preferable to mix nickel as a catalytically active component in advance when preparing the carrier. As a result of further experimental studies on a method for preparing a catalyst in one step, the inventors of the present invention discovered that the oxides of one or more oxides of the group consisting of copper, zinc, and chromium, or their hydroxides, and the oxide of nickel. It was discovered that a catalyst in combination with a hydroxide has high activity and excellent selectivity for the methanol reforming reaction, and also has a long life as there is no carbon precipitation, leading to the present invention. Ivy. Selectivity is important as a methanol reforming catalyst because the decomposition reaction of methanol into hydrogen and carbon monoxide is an endothermic reaction, which has the advantage of increasing the calorific value of the fuel. ,
This is because the side reaction in which dimethyl ether and the like are produced is an exothermic reaction, and there is a problem in that the calorific value decreases by the reaction heat of the side reaction. The present invention is characterized by a methanol reforming catalyst that combines one or more oxides of the group consisting of copper, zinc, and chromium or their hydroxides with nickel oxides or their hydroxides. . Here, in order to prepare a catalyst in which one or more oxides or hydroxides thereof from the group consisting of copper, zinc, and chromium are combined with nickel oxides or hydroxides, commercially available copper, zinc, and chromium , oxides or hydroxides of nickel may be used as they are, or hydroxides or carbonates of alkali metal elements or alkaline earth metal elements may be used as they are or in an aqueous solution as a precipitant in an aqueous solution of the above-mentioned metal compound. It may also be prepared by mixing ammonia or aqueous ammonia to form a precipitate. Furthermore, these may be converted into oxides by firing and then used as catalysts. Specifically, for example, the following method can be used to prepare a nickel oxide-chromium oxide catalyst. (1) Add an appropriate amount of water to powder or paste nickel oxide and chromium oxide, mix well, and then dry. (2) Add a mixed aqueous solution of sodium dichromate and aqueous ammonia to the aqueous solution of nickel nitrate, mix well to form a precipitate, and then wash and dry. (3) Add an aqueous solution of barium hydroxide to an aqueous solution of nickel nitrate and chromium nitrate, mix well to form a precipitate, and then wash and dry. What has been shown above is an example, and does not particularly limit the present invention. In addition, the catalyst composition of the present invention includes CuO, ZnO,
In combination with each one of Cr ₂ O ₃ , the molar ratio of the oxide form, i.e. CuO/NiO, ZnO/
For NiO, Cr ₂ O ₃ /NiO, a range of 2/8 to 6/4 is appropriate, and a range of 3/7 to 4/6 is particularly preferred, and more preferably 2 of CuO, ZnO, Cr ₂ O ₃ Composite systems containing one species or three species are preferred, such as CuO, ZnO,
For the three components of NiO, it is appropriate that the ratio (mol%) of CuO:ZnO:NiO is in the range of 50 to 20:10 to 40:20 to 60, and in particular the ratio of NiO is 30 to 50 mol%.
The preferred range is . The catalyst obtained as described above exhibits high activity at a low temperature of 300°C for the reaction of reforming methanol into a gas containing hydrogen and carbon monoxide, and also It exhibits highly selective catalytic activity with a ratio of over 90%. Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 1 [mol/] copper or zinc nitrate aqueous solution or 2 [mol/] chromium nitrate aqueous solution, respectively.
1 [mol/] nickel nitrate aqueous solution 200 c.c.
cc in advance and add 1 [mol/
] Add 200c.c. of barium hydroxide aqueous solution and mix well to form a precipitate, then wash and obtain a particle size of 2 to 4 mm.
After turning into pellets, they were dried and calcined. As described above, NiO−CuO catalyst (No. 1), NiO−
ZnO catalyst (No. 2), NiO-Cr ₂ O ₃ catalyst (No. 3)
was prepared. The activity of these catalysts was evaluated under the conditions shown in Table 1, and the results are shown in Table 2. In addition, the above catalyst
Similar activity evaluations were performed on catalysts subjected to hydrogen reduction treatment at 500° C. for 3 hours, and the results are summarized in Table 2. Furthermore, catalysts 4, 5, 6, 7, 8, and 9 having different compositions were prepared using the same procedure as described above, and the activity of these catalysts was evaluated under the conditions shown in Table 1. The results are shown in Table 3.
It was shown to.

【table】

【table】

[Table] The ratio of hydrogen and carbon monoxide in the cracked gas was over 90%. Example 2 Catalyst 10 shown in Table 4 was prepared in the same manner as in Example 1,
11, 12, and 13 were prepared respectively. The activity of these catalysts was evaluated under the same conditions as in Example 1, and the results are also shown in Table 4. The ratio of hydrogen and carbon monoxide in the cracked gas was 95% or more.

[Table] Catalysts 10, 11, and 12 are 1 for copper and zinc.
For chromium, prepare a nitrate aqueous solution of [mol/] and a 2 [mol/] nitrate aqueous solution for chromium, and mix 60 c.c. of each of the two types of aqueous solutions.
120 c.c., and further mixed with 80 c.c. of an aqueous solution of 1 [mol/] nickel nitrate.Catalyst 13 is a mixture of 80 c.c. of copper, zinc, and chromium nitrate aqueous solutions prepared respectively above. 1 [mol/mol/
] The same operation as in Example 1 was repeated except that 200 c.c. of barium hydroxide aqueous solution was added. Example 3 Among Example 2, CuO has a high methanol reaction rate.
-Catalysts 14, 15, 16 _{, 17, 18} , 19 were prepared in almost the same manner as in Example 1 by changing the composition of -ZnO-NiO and CuO- _Cr2O3 -ZnO-NiO-based catalysts,
The activity of each was evaluated under the same conditions as in Example 1, and the results are shown in Table 5.

[Table] The ratio of hydrogen and carbon monoxide in the cracked gas was 95% or more. Example 4 Regarding catalyst 13 prepared in Example 2, the reaction temperature was changed from 300°C under the same conditions as in Table 1 except for the reaction temperature.
The methanol reaction rate and the composition of the cracked gas were measured by changing the temperature up to 500°C, and the results are shown in Table 6.

【table】

[Table] In addition, when using this catalyst and keeping the reaction temperature constant at 500℃,
When the catalyst was operated continuously for 50 hours at a liquid hourly space velocity of 6 hr ^-1 , almost no carbon was deposited on the catalyst. Comparative Examples Catalyst 20 made of nickel oxide powder made into pellets with a particle size of 2 to 4 mmφ, and catalysts 1', 2', 3', 10', which did not contain nickel oxide in Examples 1 and 2,
Activity evaluation was carried out for 11', 12', and 13' (corresponding to the catalyst numbers of Examples 1 and 2) under the same conditions as in Example 1, and the results are shown in Table 7.

[Table] As can be seen from the above Examples and Comparative Examples, the catalyst of the present invention has higher activity and better selectivity at low temperatures than conventional catalysts. As shown in the Examples above, the catalyst of the present invention has high activity, high selectivity, and long life at low temperatures for the reaction of reforming methanol into a gas containing hydrogen and carbon monoxide. In the examples, a granular catalyst is described, but the shape of the catalyst is not particularly limited, and it goes without saying that catalyst shapes such as a honeycomb shape and a plate shape may be used. Further, in the examples, copper, zinc, chromium, or nitrate of nickel is used as the raw material for the carrier and catalyst, but it goes without saying that other compounds of the above metals may also be used, and the precipitants are also used in the examples. It goes without saying that hydroxides or carbonates of alkali metal elements or alkaline earth metal elements other than the barium hydroxide used may be used. Further, in the examples, methanol alone is described, but there is no problem in carrying out the methanol reforming reaction in the coexistence with a gas containing water vapor, air, or the like.

Claims (1)

[Claims] 1. A methanol reforming catalyst comprising one or more oxides or hydroxides of the group consisting of copper, zinc, and chromium, and nickel oxides or hydroxides.