JPH09168740A - Carbon dioxide modifying catalyst and modifying method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new catalyst capable of efficiently modifying carbon dioxide by supporting rhodium on one or more kind of a carrier selected from among oxide of group II, III, IV metal and a lanthanide metal oxide compd. or a composite carrier of alumina containing those metal oxides. SOLUTION: One or more kind of a carrier selected from among oxide of group II, III, IV metal and a lanthanide metal oxide or a composite carrier of those oxides and alumina is used and rhodium is supported on this carrier. As a rhodium supporting method, a known method such as an impregnation method or the like can be used. The supporting amt. of rhodium is set to 0.5-5wt.%, especially pref. 0.5-3wt.%. The carrier on which rhodium is immobilized is dried pref. at below 200 deg.C, more pref. at 150 deg.C or lower, especially pref. at 100 deg.C or less. It is necessary to reduce the supported rhodium catalyst before modifying reaction. As a reducing gas, it is pref. to use hydrogen gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carbon dioxide reforming catalyst for hydrocarbons and a carbon dioxide reforming method using the same.

[0002]

2. Description of the Related Art In recent years, carbon dioxide is a major causative agent of global warming, and therefore reduction of emission and effective use thereof have been a subject. Therefore, carbon dioxide electrical reduction method, photosynthesis method,
Chemical conversion methods such as catalytic hydrogen reduction are being studied,
As an example, there is a method of converting carbon dioxide into hydrogen and carbon monoxide, which are industrially useful synthesis gases, by using saturated hydrocarbon such as methane as a reducing agent (carbon dioxide reforming of hydrocarbon).

Known as carbon dioxide reforming catalysts for hydrocarbons are nickel catalysts in which nickel is supported on alumina or the like, and noble metal catalysts in which precious metals such as ruthenium, rhodium, or platinum are supported on alumina or the like. When a nickel-based catalyst is used, carbon tends to be deposited on the catalyst, resulting in a decrease in activity. Since noble metal catalysts have the effect of suppressing carbon deposition, they are less likely to deposit carbon and maintain their activity more easily than conventional nickel catalysts, but they are easily poisoned by sulfur components such as hydrogen sulfide. (Catalyst, Vol. 35, p. 224 (1993)). Further, when carbon dioxide is reformed using an unsaturated hydrocarbon such as ethylene, thermal carbon deposition is likely to occur due to causes other than catalyst poisoning, and even if the noble metal-based catalyst has a carbon deposition suppressing effect. , It is difficult to carry out the reaction stably and efficiently.

As described above, the raw material for carbon dioxide reforming is generally a saturated hydrocarbon mainly containing methane such as methane or natural gas. On the other hand, natural gas is valuable as a resource, and research has been conducted to produce an alternative gas from a petroleum hydrocarbon by a steam reforming reaction without using it. However, in particular, the products of steam reforming of heavy oil include unsaturated hydrocarbons and hydrogen sulfide in addition to methane, and these are not suitable as raw materials for carbon dioxide reforming reaction. is there. As a solution to these problems, there is a method of reacting a raw material containing unsaturated hydrocarbon or hydrogen sulfide and carbon dioxide in the presence of a catalyst having ruthenium supported on a specific metal oxide (Japanese Patent Application No. 7-294383). Yes, but almost nothing else.

[0005]

Therefore, according to the present invention, even with a raw material containing an unsaturated hydrocarbon or hydrogen sulfide, it is possible to suppress carbon deposition or decrease in catalytic activity due to sulfur poisoning.
It is an object of the present invention to provide a new catalyst for more efficiently reforming carbon dioxide and a carbon dioxide reforming method using the same.

[0006]

Under the circumstances, as a result of intensive investigations by the present inventors, in a carbon dioxide reforming method using a raw material containing unsaturated hydrocarbon or hydrogen sulfide, a specific metal oxide support It was found that the catalyst in which rhodium is supported is excellent in reforming activity, and there is little decrease in activity due to precipitation of carbon and poisoning of hydrogen sulfide, and the present invention has been completed.

That is, the present invention relates to at least one carrier selected from Group 2, Group 3 and Group 4 metal oxides and lanthanoid metal oxides of the Periodic Table or alumina containing these metal oxides. The present invention provides a carbon dioxide reforming catalyst in which rhodium is supported on a composite carrier. The present invention also provides a carbon dioxide reforming method using a raw material containing unsaturated hydrocarbon or hydrogen sulfide in the presence of the above catalyst.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon dioxide reforming catalyst of the present invention comprises at least one carrier selected from Group 2, Group 3, and Group 4 metal oxides and lanthanoid metal oxides, or these oxides. A composite of alumina and alumina is used as a carrier, and rhodium is supported on the carrier.

As the Group 2 metal oxide, beryllium,
Oxides of magnesium, calcium, strontium, barium and the like can be used, but it is particularly preferable to use oxides of magnesium, calcium or barium.

As the Group 3 metal oxide, oxides of scandium, yttrium and the like can be used, but yttrium oxide is particularly preferable.

Oxides of titanium and zirconium can be used as the Group 4 metal oxide.

As the lanthanoid metal oxide, oxides such as lanthanum and cerium can be used. The group of the periodic table of elements used in the present specification was based on the new IUPAC method described in Kagaku No. 45, No. 5, (1990), p. 314.

The Group 2, Group 3, and Group 4 metal oxides and the lanthanoid metal oxides can be directly supported on a carrier, but after supporting chlorides, nitrates, etc. as precursors. It is also possible to oxidize it on a support and convert it to an oxide.

Alumina can be used directly, but by using an alkoxide such as aluminum isopropoxide as a precursor, a group 2, group 3, group 4 metal oxide or lanthanoid metal oxide can be used. 1 selected from
Alumina can also be produced in a supported reaction system by oxidizing a mixture of one or more or its precursors.

Second in alumina free carrier
The respective proportions of the Group 3, Group 3, and Group 4 metal oxides and the lanthanoid metal compound are not particularly limited, but are the Group 2, Group 3, and Group 4 metal oxides and the lanthanoid metal oxides in the composite carrier with alumina. The amount of the substance is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, based on the carrier.
It is particularly preferably 15 to 30% by weight. Within such a range, sulfur resistance and catalytic activity are particularly excellent.

The specific surface area and pore volume of the carrier are not particularly limited.
However, the specific surface area of the carrier is 50m ^Two/ G or more, especially 6
0m^Two/ G or more, the pore volume is 0.1-0.8 ml / g,
It is preferably 0.2 to 0.6 ml / g.

The method for preparing the carrier is not particularly limited,
The metal oxide is dispersed in a solvent such as water, methanol, ethanol, or acetone and kneaded, and then this is baked; or a method of adjusting the pH of a mixed solution of the metal chloride and nitrate and baking the coprecipitate is mentioned. To be Alternatively, the metal oxides may be simply mechanically mixed and fired.

As a method for supporting rhodium on these carriers, known methods such as impregnation can be used.

The amount of rhodium supported is preferably 0.5 to 5% by weight, more preferably 0.5 to 3% by weight. This is because if the supported amount is too small, the amount of active sites will be small, and if it is too large, the active site amount will be saturated and the dispersibility will be reduced, which not only has no technical meaning but is uneconomical. .

The carrier on which rhodium is immobilized is dried under reduced pressure or atmospheric pressure at preferably less than 200 ° C., more preferably 150 ° C. or less, particularly preferably 100 ° C. or less.

The supported rhodium catalyst needs to be reduced before the reforming reaction. As such a reducing method, it is preferable that the catalyst is immobilized and dried and then the reducing gas is used in the reactor.

As the reducing gas, pure hydrogen, hydrogen / steam and carbon monoxide can be used, and hydrogen gas is preferably used.

The reduction temperature may be the reaction temperature of the reforming reaction, but it can be carried out at a lower temperature so that the metal does not aggregate. The carbon dioxide reforming method of the present invention is preferably a method of bringing the catalyst into contact with the raw material gas immediately after the reduction.

The carbon dioxide reforming method of the present invention includes:
It can be carried out using a raw material containing unsaturated hydrocarbon or hydrogen sulfide in the presence of the above catalyst.

Such raw materials are unsaturated hydrocarbons, a mixture of saturated hydrocarbons and unsaturated hydrocarbons, or those containing hydrogen sulfide. Here, the raw material saturated hydrocarbon used is not particularly limited, but a linear, branched or cyclic saturated hydrocarbon having 1 to 6 carbon atoms is preferable, and methane, ethane, propane or a mixture thereof is particularly preferable. Further, the unsaturated hydrocarbon is not particularly limited, but a linear, branched or cyclic unsaturated hydrocarbon having 2 to 6 carbon atoms is preferable, and specifically, ethylene, propene, butene, or a mixture thereof or the like. Is preferred.

The amount of hydrogen sulfide contained in the raw material is not particularly limited, but is not more than 100 ppm in the raw material gas, especially 10 pp.
m or less is preferable from the viewpoint of catalyst poisoning.

Particularly preferred as a raw material used in the present invention is a product gas (alternative natural gas) obtained by steam reforming heavy oil such as vacuum residue. The composition of the substitute natural gas is usually 10 to 30 mol% of saturated hydrocarbons, 1 to 50 mol% of unsaturated hydrocarbons, 0 to 100 ppm of hydrogen sulfide, and 1 hydrogen.
Since it is 0 to 60 mol% and 1 to 20 mol% of carbon monoxide, the raw material of the present invention may contain hydrogen and carbon monoxide in addition to saturated hydrocarbon, unsaturated hydrocarbon and hydrogen sulfide. Good.

The supply amount of carbon dioxide is not particularly limited, but it is preferable that the number of moles of carbon dioxide / the number of moles of carbon of all hydrocarbons in the raw material (CO ₂ / C) is about 0.5 to 5. , Especially 1.2-2.8, and even 1.5-2.5
It is preferred that the amount of carbon is less and the conversion rate is higher.

The reaction temperature in the carbon dioxide reforming method of the present invention is preferably 500 to 1200 ° C, more preferably 800 to 1000 ° C. From the viewpoint of suppressing carbon precipitation, the pressure is preferably 10 atm or less, particularly about normal pressure. The source gas is GHSV500 to 20000.
It is preferably supplied at h ^-1 .

Hydrogen and carbon monoxide are produced by the carbon dioxide reforming method of the present invention. These can be used as a synthesis gas, a fuel gas, etc., and can also be separated and recovered by means of pressure swing adsorption. can do.

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, carbon dioxide reforming of a raw material containing unsaturated hydrocarbon or hydrogen sulfide can be carried out in a high yield while suppressing a decrease in catalytic activity due to carbonization precipitation or sulfur poisoning. it can. This is because the sulfur compounds such as hydrogen sulfide in the raw material gas are adsorbed and absorbed by the group 2, group 3, group 4 and lanthanoid metal oxide components, so that the active component rhodium is less likely to be poisoned and the life is shortened. It seems to be extended. Further, according to the present invention, it is possible to synthesize hydrogen and carbon monoxide not only from natural gas, which is a valuable resource, but also from a wide range of raw materials such as gas obtained by steam reforming of heavy oil. Become.

[0032]

EXAMPLES The present invention will now be described in more detail by way of examples, which are merely examples and do not limit the present invention.

In the examples and comparative examples, the produced gas was analyzed by gas chromatography. In the table, the conversion rate of hydrocarbons and the amount of deposited carbon were determined by the following equations.

Hydrocarbon conversion rate = (mol number of hydrocarbon in raw material−mol number of hydrocarbon in produced gas) / (mol number of hydrocarbon in raw material) × 100

Amount of deposited carbon = (number of moles of deposited carbon) /
(Mole number of carbon atoms in the raw material) x 100

Example 1 100 g of cerium oxide powder was thoroughly mixed in a mortar, and then about 40 ml of water was added and further kneaded. The paste-like mixture was heated to 60 to 70 ° C. under reduced pressure of about 2.7 KPa to remove water. This was pre-dried in a dryer kept at 105 ° C., and then calcined at 500 ° C. for 3 hours in an electric furnace to obtain a carrier (A). 20 g of the carrier was immersed in an aqueous solution of 1 g of rhodium chloride trihydrate dissolved in 37 ml of water for 1 hour,
After removing the residual liquid, 40 to 50 ° C. under reduced pressure of about 2.7 KPa.
Water was removed by heating. This was added to 10 to 15% by volume of ammonia water, kept at 40 ° C., stirred for 2 hours,
After the rhodium was insoluble and fixed, the catalyst was filtered off and thoroughly washed with pure water. Furthermore, in a vacuum dryer
The catalyst (A-1) was prepared by drying at 45 ° C for 8 hours. 4 ml of this catalyst was filled in a stainless steel reaction tube, and the temperature was set to 900.
Hydrogen was supplied at atmospheric pressure for about 4 hours in the process of heating to 0 ° C. for reduction treatment. Thereafter, a gas containing 14 mol% of methane and 14 mol% of hydrogen, 22 mol% of hydrogen, 7 mol% of carbon monoxide, and 43 mol% of carbon dioxide was supplied at 900 ° C. and atmospheric pressure at a GHSV of about 4000 h ⁻¹ , and 4 Reacted for hours. Table 1 shows the conversion rate and the carbon deposition amount at this time.

Example 2 Example 1 except that 20 g of magnesium oxide powder and 80 g of alumina powder were used instead of 100 g of cerium oxide powder.
A carrier (B) was prepared in the same manner as in Example 1 and the carrier was used in Example 1.
A catalyst (B-1) was prepared by supporting rhodium in the same manner as in. Fill 4 ml of this catalyst into a stainless steel reaction tube,
The reduction treatment and the carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

Example 3 Example 1 was repeated except that 20 g of yttrium oxide powder and 80 g of alumina powder were used instead of 100 g of cerium oxide powder.
A carrier (C) was prepared in the same manner as in Example 1 and the carrier was used in Example 1.
A catalyst (C-1) was prepared by supporting rhodium in the same manner as in. Fill 4 ml of this catalyst into a stainless steel reaction tube,
The reduction treatment and the carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

Example 4 Zirconium oxide 1 instead of 100 g of cerium oxide powder
A carrier (D) was prepared in the same manner as in Example 1 except that 00 g was used, and rhodium was loaded on this carrier in the same manner as in Example 1 to prepare a catalyst (D-1). 4 ml of this catalyst was filled in a stainless steel reaction tube, and reduction treatment and carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results
Shown in

Comparative Example 1 25 g of the carrier (A) of Example 1 and 1 g of ruthenium chloride monohydrate were immersed in an aqueous solution of 37 ml of water for 1 hour to remove the residual liquid, and then under reduced pressure of about 2.7 KPa. And heated to 40-50 ° C to remove water. This was added to 10 to 15% by volume of ammonia water, kept at 40 ° C. and stirred for 2 hours to insolubilize and immobilize ruthenium, and then the catalyst was filtered off and thoroughly washed with pure water. Furthermore, in a vacuum dryer
It dried at 45 degreeC for 8 hours, and obtained the catalyst (A-2). 4 ml of this catalyst was filled in a stainless steel reaction tube, and reduction treatment and carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 A catalyst (B-2) was obtained by loading 20 g of the carrier (B) obtained in Example 2 with ruthenium in the same manner as in Comparative Example 1. 4 ml of this catalyst was filled in a stainless steel reactor, and reduction treatment and carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 20 g of the carrier (B) of Example 2 was added to 1 g of chloroplatinic acid hexahydrate.
Is immersed in an aqueous solution of 37 ml of water for 1 hour, the residual liquid is removed, and the product is washed with pure water.
Water was removed by heating to ~ 50 ° C. This was dried in a vacuum dryer at 40 to 45 ° C. for 8 hours to obtain a catalyst (B-3). 4 ml of this catalyst was filled in a stainless steel reaction tube, and reduction treatment and carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 4 20 g of the carrier (B) obtained in Example 2 was loaded with 10% by weight of nickel by an impregnation method to obtain a catalyst (B-4). This catalyst 4
ml was filled in a stainless steel reaction tube, and reduction treatment and carbon dioxide reforming reaction were performed in the same manner as in Example 1. Table 1 shows the results.

[0044]

[Table 1]

From Table 1, the catalyst supporting rhodium has a higher conversion rate and less carbon deposition than the ruthenium, platinum and nickel catalysts.

Example 5 4 ml of the catalyst (A-1) prepared in Example 1 was filled in a stainless steel reaction tube, and hydrogen was supplied at atmospheric pressure for about 4 hours in the process of heating to 900 ° C. for reduction. Processed. Then, 13 mol% each of methane and ethylene, 27 mol% of hydrogen, 6 mol% of carbon monoxide, and 4 mol of carbon dioxide.
A gas containing 1 mol% and 5 ppm of hydrogen sulfide was supplied at 900 ° C. and normal pressure at a GHSV of about 4000 h ⁻¹ to perform a carbon dioxide reforming reaction. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Example 6 4 ml of the catalyst (B-1) prepared in Example 2 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Example 7 4 ml of the catalyst (C-1) prepared in Example 3 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Example 8 4 ml of the catalyst (D-1) prepared in Example 4 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Comparative Example 5 4 ml of the catalyst (B-2) prepared in Comparative Example 2 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Comparative Example 6 4 ml of the catalyst (B-3) prepared in Comparative Example 3 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

Comparative Example 7 4 ml of the catalyst (B-4) prepared in Comparative Example 4 was subjected to reduction treatment and carbon dioxide reforming reaction in the same manner as in Example 5. Table 2 shows the conversion rates 20 hours after the start of the reaction.

[0053]

[Table 2]

It can be seen from Table 2 that the rhodium catalyst has a higher conversion rate than the ruthenium, platinum and nickel catalysts, and maintains a high activity even in the presence of hydrogen sulfide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Takaoka 2856-1 Osawa, Koshigaya City, Saitama Century Condominium Saga 206 (72) Inventor Takashi Yoshizawa 1-69-25 Iwana, Noda City, Chiba Prefecture

Claims (3)

[Claims] 1. Rhodium on one or more carriers selected from Group 2, Group 3, and Group 4 metal oxides and lanthanoid metal oxides of the Periodic Table or on a composite carrier of alumina containing these metal oxides. A carbon dioxide reforming catalyst, characterized in that it carries. 2. A method for reforming carbon dioxide using a raw material containing unsaturated hydrocarbon or hydrogen sulfide in the presence of the catalyst according to claim 1. 3. The reforming method according to claim 2, wherein the molar ratio of carbon dioxide to the total hydrocarbons in the raw material is 0.5 to 5.