JP5242086B2 - Hydrogen production ethanol reforming catalyst and hydrogen production method - Google Patents

Description

  The present invention relates to a hydrogen production ethanol reforming catalyst for producing hydrogen by reforming ethanol, and a hydrogen production method using the same.

  Hydrogen (gas) has heretofore been used in large quantities as a basic raw material gas for petrochemicals, and in recent years, great expectations are placed on it as a clean energy source. Such hydrogen is mainly composed of hydrocarbons such as methane, butane and kerosene, and oxygen-containing hydrocarbons (hydrocarbons containing oxygen atoms) such as methanol, ethanol and dimethyl ether, and water (steam), carbon dioxide, oxygen Can be obtained from these source gases using chemical reactions such as reforming reaction, partial oxidation reaction, and decomposition reaction.

Among the main raw material gases, ethanol is expected as a carbon-neutral next-generation raw material derived from biomass, and steam reforming using ethanol as a raw material is represented by the following chemical formula.
C ₂ H ₅ OH + 3H ₂ O = 2CO ₂ + 6H ₂

The above reaction can proceed thermodynamically at about 400 ° C. However, in reforming catalysts such as Ni / Al ₂ O ₃ and Rh / Al ₂ O ₃ that are generally used in the past, since methane is by-produced, methane steam reforming is substantially achieved, and a sufficient reaction rate is obtained. Required a high temperature of 700-800 ° C. Therefore, in recent years, a catalyst for reforming ethanol at a low temperature (a catalyst that does not produce methane as a by-product) has been developed.

Patent Documents 1 and 2 propose ethanol steam reforming using a ruthenium-based catalyst (ZrO ₂ , CeO ₂ , ZrO ₂ -CeO ₂ support) and a cobalt-based catalyst (ZrO ₂ -CeO ₂ support), respectively. It is said that hydrogen can be produced at 250 to 500 ° C. in the former and 300 to 500 ° C. in the latter.

In Non-Patent Document 1, it is reported that a cobalt-based catalyst (ZnO, La ₂ O ₃ support) generates hydrogen at a high yield at 400 to 500 ° C.

JP 2005-131468 A JP 2005-131469 A Applied Catalysis A: General 243 (2003) 261-269

However, in these prior arts, the hydrogen yield (in the ethanol steam reforming, a maximum of 6 mol of hydrogen is generated per 1 mol of ethanol, the actual hydrogen ratio to the maximum value of 6 mol is expressed as hydrogen in this application. (E.g., defined as the yield) is low, and evaluation is performed under reaction conditions (raw gas is dilute or H ₂ O / EtOH is high) that seems to be effective for suppressing coking. Under the conditions, there is a problem that coking occurs in a short time and lacks durability.

  An object of the present invention is to provide a hydrogen production ethanol reforming catalyst for reforming ethanol at a lower temperature than before and efficiently producing hydrogen while suppressing coking, and a hydrogen production method using the same. is there.

  The inventors of the present invention can solve the above-mentioned problems by including a hydrogen production ethanol reforming catalyst in a mixture of a steam reforming catalyst for the reforming reaction and a shift reaction catalyst for the shift reaction. I found. That is, according to the present invention, the following hydrogen production ethanol reforming catalyst and a hydrogen production method using the same are provided.

[1] A steam reforming catalyst for a reforming reaction that generates a mixed gas containing hydrogen and carbon monoxide or carbon dioxide by a reaction between a hydrocarbon containing ethanol and steam; A shift reaction catalyst for a shift reaction that generates hydrogen and carbon dioxide by reaction and an ethanol dehydrogenation catalyst having a function of dehydrogenating from ethanol are mixed, and the steam reforming catalyst is used as an active metal. , Co, and any Ru, as a carrier, wherein ZnO, and one of _La 2 _{O 3,} wherein the shift reaction catalyst, as active catalyst / _{carrier, Fe 2 O 3 / Cr 2} O 3, 及 beauty Pt / comprise any TiO _2, wherein the ethanol dehydrogenation catalysts, as an active metal, Cu, as a carrier, the basic carrier, ZnO, MgO, and any _La 2 _{O 3} A hydrogen production ethanol reforming catalyst containing the above.

[ 2 ] A hydrogen production method for producing hydrogen by reaction of a raw material gas containing ethanol and water vapor using the hydrogen production ethanol reforming catalyst according to [1 ] .

[ 3 ] The method for producing hydrogen according to [ 2 ], wherein ethanol and water vapor are reacted at 300 to 550 ° C.

[ 4 ] The method for producing hydrogen according to [ 2 ] or [ 3 ], wherein ethanol and water vapor are reacted at 1 to 5 atm.

[ 5 ] The method for producing hydrogen according to any one of [ 2 ] to [ 4 ], wherein CH ₄ / (CH ₄ + CO + CO ₂ ) in a product gas generated by reacting the raw material gas is 0.4 or less.

[6] The molar ratio of water vapor _(H 2 O), to ethanol of the material gas _{(C 2} H 5 OH) is the production of hydrogen according to any one of the is 1.5 to 5 [2-5] Method.

[ 7 ] The hydrogen production method according to any one of [ 2 ] to [ 6 ], wherein the hydrogen production ethanol reforming catalyst is 0.1 to 10 g with respect to 100 cc / min of the source gas.

  By including a steam reforming catalyst, the hydrogen production ethanol reforming catalyst can perform a reforming reaction at a lower temperature than conventional. Moreover, since the shift reaction catalyst is included, hydrogen can be efficiently produced while suppressing coking. For this reason, manufacturing cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  The hydrogen production ethanol reforming catalyst of the present invention includes a steam reforming catalyst for reforming reaction that generates hydrogen and a mixed gas containing carbon monoxide or carbon dioxide by a reaction between a hydrocarbon containing ethanol and steam. And a shift reaction catalyst for the shift reaction that generates hydrogen and carbon dioxide by the reaction of carbon monoxide and water vapor. With the hydrogen production ethanol reforming catalyst of the present invention, ethanol and water vapor can be reacted to produce hydrogen more efficiently at a lower temperature than conventional.

The steam reforming catalyst is, for example, a catalyst having a function of generating hydrogen from ethanol and steam, or a function of generating hydrogen from acetaldehyde generated from ethanol, as in the following formula.
C ₂ H ₅ OH + H ₂ O → 2CO + 4H ₂
CH ₃ CHO + H ₂ O → 2CO + 4H ₂

As the active metal of the steam reforming catalyst, Co and Ru are preferable. Further, ZnO and La ₂ O ₃ are preferable as the carrier. The steam reforming catalyst, the active metal and carrier, Co / ZnO, be a Co / _La 2 _{O 3,} particularly preferred.

The shift reaction catalyst has a function of generating hydrogen and carbon dioxide from carbon monoxide as shown in the following formula.
CO + H ₂ O → CO ₂ + H ₂

The shift reaction catalyst is not particularly limited, and those generally used can be used, but those in which the active catalyst / support is Fe ₂ O ₃ / Cr ₂ O ₃ , Cu / ZnO, Pt / TiO ₂ are used. It is preferable to do.

A catalyst (shift reaction catalyst) that promotes a shift reaction (CO + H ₂ O = CO ₂ + H ₂ ), which is considered to be effective in suppressing CO disproportionation reaction (2CO = C + CO ₂ ) that causes coking, Hydrogen can be efficiently obtained at a low temperature while suppressing coking by mixing with a catalyst to form a hydrogen production ethanol reforming catalyst. Since the shift reaction proceeds, the hydrogen yield is also improved.

  The hydrogen production ethanol reforming catalyst of the present invention is a mixture of a steam reforming catalyst and a shift reaction catalyst, and thereby can efficiently produce hydrogen at a lower temperature than before while suppressing coking. However, in addition to the steam reforming catalyst and the shift reaction catalyst, it is more preferable that an ethanol dehydrogenation catalyst is further mixed and contained.

The ethanol dehydrogenation catalyst has a function of dehydrogenating from ethanol, for example, as in the following formula.
C ₂ H ₅ OH → CH ₃ CHO + H ₂

The ethanol dehydrogenation catalyst preferably contains Cu as an active metal. The ethanol dehydrogenation catalyst may be a carrier that does not have a property as a strong solid acid typified by Al ₂ O ₃ , silica alumina, or zeolite, and a carrier having no acid sites such as SiO ₂ should be used. However, basic carriers such as MgO and La ₂ O ₃ are preferably used, and ZnO is particularly preferable.

  The hydrogen production ethanol reforming catalyst is, for example, a physical mixture in which a plurality of types of individually produced catalysts are physically mixed, and a plurality of types of individually produced catalysts are ground and combined in a mortar or the like. The shape is not particularly limited as long as it is mixed by contact mixing, the same carrier mixture in which a plurality of types of active metals are supported on the same carrier, or the like, but the powder, pellet shape, or ceramic such as honeycomb It can be carried on a structure. Thus, the hydrogen production ethanol reforming catalyst used in the ethanol reforming reaction is not particularly limited as long as the active component of each reaction is present in a mixed manner.

  Next, a hydrogen production method for producing hydrogen by a reaction between ethanol and steam using the hydrogen production ethanol reforming catalyst of the present invention will be described. The hydrogen production equipment is a general equipment that is configured so that water and ethanol can be used as a raw material gas source, and water and ethanol can be vaporized and mixed by a vaporizer to be supplied to the reactor. Can be used.

  The catalyst layer of the reactor has a steam reforming catalyst for a reforming reaction that generates a mixed gas containing hydrogen and carbon monoxide or carbon dioxide, and a shift reaction for a shift reaction that generates hydrogen and carbon dioxide. A hydrogen production ethanol reforming catalyst of the present invention comprising at least a catalyst and a mixture.

Gasified H ₂ O (steam) and ethanol are introduced into the reactor of the hydrogen production apparatus, and brought into contact with the hydrogen production ethanol reforming catalyst, and ethanol at 300 to 550 ° C., more preferably at 400 to 500 ° C. And H ₂ O are reacted. Ethanol and water vapor are reacted at 1 to 5 atm, more preferably 1 to 3 atm. The molar ratio of water vapor (H ₂ O) to ethanol (C ₂ H ₅ OH) of the raw material gas is 1.5 to 5, more preferably 2 to 3.5. Further, the hydrogen production ethanol reforming catalyst is reacted in an amount of 0.1 to 10 g, more preferably 0.5 to 5 g with respect to 100 cc / min of the raw material gas.

  The reaction may be carried out by selectively separating the carbon dioxide and hydrogen of the product with a selectively permeable membrane reactor or the like by combining a separation membrane and an adsorbent. When separating hydrogen, a palladium alloy membrane or a porous ceramic membrane such as silica or zeolite can be used as the membrane, or a carbon membrane and a hydrogen storage alloy containing nickel, manganese, vanadium, etc. can be used as the adsorbent. . As the carbon dioxide removing means, a carbon dioxide adsorbent, a carbon dioxide separation membrane, or the like can be suitably used. As the adsorbent, for example, an inorganic compound such as calcium oxide or lithium silicate, an alkali solution, an ionic solution, or an inorganic porous material such as alumina or silica carrying an alkali solution or an ionic solution is preferably used. Can do. As the carbon dioxide separation membrane, for example, a polymer membrane or a zeolite membrane can be suitably used.

  According to the hydrogen production method as described above, hydrogen can be efficiently produced at 300 to 550 ° C., which is lower than conventional, while suppressing coking. For this reason, manufacturing cost can be reduced more than before.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Evaluation device and evaluation method)
The catalysts of Examples and Comparative Examples were evaluated. The hydrogen production apparatus can supply ethanol and water vaporized by heating to a reactor filled with a catalyst. A flow meter for measuring the amount of product gas and a gas chromatograph for quantifying gas components are connected downstream of the reactor. Note that a liquid trap set at about 5 ° C. is provided on the upstream side of the flow meter to collect liquid components such as water.

Regarding Rh / Al ₂ O ₃ , Fe ₂ O ₃ / Cr ₂ O ₃ and Cu / ZnO, commercially available products were pulverized and sized to 0.5 to 1 mm. Co / ZnO and Co / La ₂ O ₃ were prepared by an impregnation method. The weight ratio of Co to the carrier is 16 wt%. In use, the particles were sized to 0.5 to 1 mm in the same manner as Fe ₂ O ₃ / Cr ₂ O ₃ .

The reaction was carried out by appropriately setting the raw material gas flow rate, the reaction temperature, and the reaction pressure to desired values with the respective regulators. The hydrogen yield was determined from the product gas flow rate and its composition.
Hydrogen yield [%] = 100 × outlet hydrogen flow rate / (inlet ethanol flow rate × 6)

( Reference Examples 1 and 2)
A hydrogen production ethanol reforming catalyst in which Co / ZnO was mixed as a steam reforming catalyst and Fe ₂ O ₃ / Cr ₂ O ₃ was mixed as a shift reaction catalyst was used.

( Reference Example 3)
Steam reforming catalyst as Co / _La 2 _{O 3,} with a shift reaction catalyst as _{Fe 2 O 3 / Cr 2 O} 3 were mixed hydrogen ethanol reforming catalysts.

(Example 1 )
A hydrogen production ethanol catalyst in which Cu / ZnO was mixed as the ethanol dehydrogenation catalyst, Co / ZnO as the steam reforming catalyst, and Fe ₂ O ₃ / Cr ₂ O ₃ mixed as the shift reaction catalyst was used.

(Comparative Example 1)
A catalyst comprising a steam reforming catalyst Rh / Al ₂ O ₃ and containing no shift reaction catalyst was used.

(Comparative Example 2)
A catalyst made of Co / ZnO as a steam reforming catalyst and containing no shift reaction catalyst was used. The results of the above Example 1 , Reference Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1. The hydrogen yield and the like are averages after steady state (about 15 minutes to about 1 to 2 hours after the start of the reaction), but since Comparative Example 2 was deactivated, it was initially (about 15 minutes after the start of the reaction). ). Moreover, ethanol and water vapor were reacted at the reaction temperature and reaction pressure shown in Table 1.

In Example 1 and Reference Examples 1 to 3 , a catalyst in which a steam reforming catalyst and a shift reaction catalyst were mixed was used, and hydrogen could be produced at a lower temperature of 450 ° C. for a longer time. Specifically, Reference Example 1 was a mixture of the catalyst of Comparative Example 2 and a shift reaction catalyst, and the low-temperature activity was improved and was not deactivated. Reference Example 2 is a mixture of the catalyst of Comparative Example 2 and a shift reaction catalyst, Reference Example 3 is a mixture of Co / La ₂ O ₃ and a shift reaction catalyst, Example 1 is Cu / ZnO and Co / ZnO, Although a shift reaction catalyst was mixed, the low-temperature activity was improved as in Reference Example 1 and was not deactivated. In Example 1 and Reference Examples 1 to 3 , CH ₄ / (CH ₄ + CO + CO ₂ ) in the product gas generated by reacting the raw material gas is 0.4 or less and needs to be reformed at a high temperature. High yields of hydrogen were obtained because the production of CH ₄ could be reduced.

On the other hand, Comparative Example 1 is a general reforming catalyst. Although CO ₂ / CO is high, the ratio of CH ₄ / (CH ₄ + CO + CO ₂ ) is high, so the activity at low temperature is low, and the hydrogen yield is low. It was low. Comparative Example 2 had high activity at low temperature and high hydrogen yield, but was deactivated in 2 hours because it contained no shift reaction catalyst.

1 and 2 show the change over time in the hydrogen yield. FIG. 1 shows Reference Example 1 (mixture of Co / ZnO and Fe ₂ O ₃ / Cr ₂ O ₃ ), and FIG. 2 shows Comparative Example 1 (Co / ZnO only). In Reference Example 1, as shown in FIG. 1, a good hydrogen yield could be maintained even after 6 hours. On the other hand, in Comparative Example 1 not including the shift reaction catalyst, as shown in FIG. 2, the hydrogen yield extremely decreased after 2 hours. In the present application, a catalyst having a high hydrogen yield over a long time is desirable. From this viewpoint, the catalysts of Example 1 and Reference Examples 1 to 3 are superior to the catalysts of Comparative Examples 1 and 2.

  The catalyst of the present invention can be used as a hydrogen production ethanol reforming catalyst for reforming ethanol to produce hydrogen. In addition, the production method of the present invention can be used as a hydrogen production method that is more efficient at a lower temperature than in the past.

4 is a graph showing the change over time in the hydrogen yield of Reference Example 1. 6 is a graph showing the change over time in the hydrogen yield of Comparative Example 1.

Claims (7)

A steam reforming catalyst for a reforming reaction that generates a mixed gas containing hydrogen and carbon monoxide or carbon dioxide by a reaction between a hydrocarbon containing ethanol and steam;
A shift reaction catalyst for the shift reaction that generates hydrogen and carbon dioxide by the reaction of carbon monoxide and water vapor;
An ethanol dehydrogenation catalyst having a function of dehydrogenating from ethanol,
The steam reforming catalyst includes any one of Co and Ru as an active metal, and any one of ZnO and La ₂ O ₃ as a support,
The shift reaction catalyst comprises as active catalyst / _{carrier, Fe 2 O 3 / Cr 2} O 3, one of 及 beauty Pt / TiO _2,
The ethanol dehydrogenation catalyst is a hydrogen production ethanol reforming catalyst containing Cu as an active metal and any one of ZnO, MgO, and La ₂ O ₃ as a basic support as a support.   A hydrogen production method for producing hydrogen by a reaction of a raw material gas containing ethanol and water vapor using the hydrogen production ethanol reforming catalyst according to claim 1.   The method for producing hydrogen according to claim 2, wherein ethanol and water vapor are reacted at 300 to 550 ° C.   The hydrogen production method according to claim 2 or 3, wherein ethanol and water vapor are reacted at 1 to 5 atm. 5. The hydrogen production method according to claim 2, wherein CH ₄ / (CH ₄ + CO + CO ₂ ) in a product gas generated by reacting the raw material gas is 0.4 or less. Molar ratio to a method of producing hydrogen according to any one of claims 2 to 5 is a 1.5-5 water vapor _(H 2 O) to ethanol _{(C 2} H 5 OH) of the raw material gas.   The hydrogen production method according to claim 2, wherein the hydrogen production ethanol reforming catalyst is 0.1 to 10 g with respect to the source gas of 100 cc / min.

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