JP5572855B2 - Biomass gasification reforming catalyst and method for producing synthesis gas using the same - Google Patents

Description

  The present invention relates to a reforming catalyst and a method for producing synthesis gas using the same, and more specifically, a reforming catalyst having high activity and high selectivity, and further, high carbon combustion activity, heat resistance, and easy reduction. And a synthesis gas production method using the catalyst.

  Biomass is an ecological term that is used in a broad sense for the overall expression of biomass in terms of substance. In recent years, it is also used in the meaning of biological resources, and fuel using biomass is also called biofuel. Such a biomass (also referred to as “raw material biomass”) includes a method of gasifying it and using it as biofuel.

  In general, in biomass gasification, as the gasification temperature becomes lower, the amount of tar, which is a high molecular weight hydrocarbon, increases. On the other hand, the higher the gasification temperature, the lower the molecular weight. The generation amount tends to increase. Therefore, as a method for gasifying biomass, a method is generally used in which gasification is performed at a high temperature of about 1000 ° C. by partial oxidation using air / oxygen as a gasifying agent to suppress tar formation. .

  For this reason, in general gasification of biomass, biomass itself is often used as a heat source fuel. Specifically, nearly 40 to 60% is burned as a heat source for obtaining heat necessary for the reaction. As a result, the yield of synthesis gas from biomass decreases. When air is used as the gasifying agent, the synthesis gas is diluted with about 80% of nitrogen contained in the air, resulting in a synthesis gas having a lower energy density.

  Therefore, in order to obtain synthesis gas with a high yield, it is necessary to perform gasification at a lower temperature. However, if gasification is performed at a low temperature, the yield of synthesis gas decreases due to the generation of tar as described above. In addition, there is a problem that the generated tar and solid carbon adhere to the piping and the reaction furnace and adversely affect the process itself.

  Therefore, the use of a catalyst is considered as a solution for producing synthesis gas from biomass at a low temperature and at a higher yield. However, even when a catalyst is used, tar is generated in the synthesis gas, resulting in a decrease in the synthesis gas yield. In addition, the tar adheres to the catalyst, reducing the active sites, resulting in a decrease in catalyst performance. Or, it may be deactivated by carbon deposition on the catalyst. Therefore, it was expected to develop a catalyst that suppresses tar generation and carbon deposition to the maximum, enables a high conversion rate (high selectivity for tar reforming), and has a low cost and a long life.

  Unlike a reforming catalyst such as methane, the gasification catalyst for biomass is almost impossible to completely remove carbon deposition because the raw material is a high molecular weight hydrocarbon compound. For this reason, in order to use the catalyst without replacement for a long period of time, a catalyst regeneration step is indispensable, and it is necessary to develop a catalyst that can be regenerated and has a long life and high activity that maintains its function. Therefore, in addition to maximizing tar generation and carbon deposition and enabling a high conversion rate, when regenerating the catalyst by combustion removal of tar and deposited carbon deposited on the catalyst, There has been a demand for a catalyst having heat resistance, which is a countermeasure against the problem. Furthermore, in addition to heat resistance, it has high carbon combustion activity so that regeneration by combustion can be performed at a lower temperature, and easy reducibility to easily perform regeneration by reduction of deactivation caused by metal oxidation due to the combustion. A catalyst was desired.

  By the way, conventionally, various reforming catalysts have been proposed. For example, in JP 2005-529744 A, for the purpose of providing a catalyst capable of controlling the activity and / or selectivity, based on the total weight of the supported catalyst, (i) a specific amount of cobalt, nickel or the like (Ii) a specific amount of at least one promoter selected from specific metals; and (iii) a Fischer-Tropsch synthesis catalyst or catalyst precursor containing a specific amount of carbon on an inert support, etc. Is disclosed.

  Moreover, in Japanese translations of PCT publication No. 2007-532305, for the purpose of providing a catalyst that can be used for producing hydrogen from a hydrocarbon fuel by steam reforming treatment, the alkaline earth metal hexaaluminate is contained in a specific amount or more. A catalyst carrier or the like having the above surface area is disclosed.

  However, these prior art catalysts are all intended for hydrocarbons such as gasoline, kerosene, diesel oil, etc., and have not been disclosed as catalysts for producing synthesis gas from biomass in higher yields. Absent.

JP 2005-529744 A Special table 2007-532305 gazette

  An object of the present invention is to provide a reforming catalyst having high heat resistance for producing synthesis gas from biomass at a higher yield. In addition, the present invention has a high carbon combustion activity so that the regeneration by the combustion can be performed at a lower temperature, as well as heat resistance, which is a countermeasure against a high temperature when the catalyst is regenerated by removing the carbon by combustion, and its combustion Another object of the present invention is to provide a reforming catalyst having easy reducibility for facilitating regeneration by reduction of deactivation caused by metal oxidation due to.

  The present invention achieves the object of the present invention by providing an invention having the following configuration.

  A reforming catalyst that is used when biomass is used as a raw material to obtain synthesis gas through a reforming reaction, and includes at least an alkaline earth metal aluminate.

  A reforming catalyst, comprising at least nickel (Ni) in addition to the alkaline earth metal aluminate.

  A reforming catalyst, comprising at least iron (Fe) in combination with the alkaline earth metal aluminate and nickel.

  The reforming catalyst, comprising at least platinum (Pt) in addition to the alkaline earth metal aluminate, nickel, and iron.

The reforming catalyst, wherein the alkaline earth metal aluminate is barium hexaaluminate (BaAl ₁₂ O ₁₉ ).

  The reforming catalyst, wherein the biomass is agricultural biomass.

  The reforming catalyst, wherein the biomass is woody biomass.

  A reforming catalyst, wherein the reforming catalyst is a steam reforming catalyst.

  Furthermore, it is a method for producing a synthesis gas using biomass as a raw material and generating hydrogen and carbon monoxide by a reforming reaction using a catalyst, wherein the synthesis gas is produced using any one of the above reforming catalysts as the catalyst. Method.

  The method for producing synthesis gas, wherein the catalyst used in the method for producing synthesis gas is a steam reforming catalyst.

  A method for producing the synthesis gas, wherein the biomass is thermochemically decomposed and partially oxidized to obtain a product of hydrogen, carbon monoxide, tar content, carbon content and ash content, and other than the ash content A reforming step of introducing the product into the catalyst and reforming them using heat obtained in the partial oxidation step.

  The method for producing synthesis gas, wherein the reforming step includes a steam reforming step by a steam reforming reaction in which the product other than the ash is reacted with steam.

  A method for producing a synthesis gas, wherein at least part of heat required for the partial oxidation step, the reforming step, and the steam reforming step is supplied by external heat.

  The partial oxidation step, the reforming step, and the steam reforming step are a synthesis gas production method that is performed in a temperature range of 300 to 1100 ° C.

  According to the above, a reforming catalyst having high activity and high selectivity for producing synthesis gas from biomass at a higher yield is provided. Further, a steam reforming catalyst having high combustion activity, heat resistance, and easy reduction is also provided. Furthermore, a method for producing a synthesis gas is provided that can produce a synthesis gas with a higher yield using biomass as a raw material.

It is a conceptual diagram of the apparatus which evaluates the performance of the reforming catalyst which concerns on the present Example for biomass gasification.

  Next, the present invention will be described in more detail based on preferred embodiments thereof.

  As described above, the reforming catalyst of the present invention is used when obtaining synthesis gas (Syngas) through a reforming reaction using biomass as a raw material, and contains at least an alkaline earth metal aluminate. Since the reforming catalyst of the present invention has such a configuration, it has higher heat resistance than conventional catalysts.

Examples of the alkaline earth metal aluminate used in the present invention include barium hexaaluminate (BaAl ₁₂ O ₁₉ ), magnesium hexaaluminate, strontium hexaaluminate, calcium hexaaluminate, magnesium calcium hexaaluminate and the like. It is done.

In particular, barium hexaaluminate (BaAl ₁₂ O ₁₉ ) is preferable because it can further improve the heat resistance of the reforming catalyst. When barium hexaaluminate is used as a carrier and a metal is supported and fired at a high temperature, the reduction rate of the surface area is smaller than when alumina (Al ₂ O ₃ ) is used, and the surface area has a high specific surface area. The effect is due to the unique surface of barium hexaaluminate. That is, when barium hexaaluminate is used as a carrier, it becomes a catalyst carrier with high heat resistance in which sintering is suppressed even under high temperature conditions.

  Moreover, in the reforming catalyst of this invention, it is preferable that nickel (Ni) is included as a structural component with a metal aluminate at least. In the present invention, by using nickel together, the selectivity of tar modification can be further improved while maintaining the effect of barium hexaaluminate. Nickel is also useful for producing a reforming catalyst because it can be obtained at low cost.

  When nickel is used as a component of the reforming catalyst, the nickel content is preferably in the range of 1 to 25% by mass with respect to the reforming catalyst. This is not preferable in the case of less than 1% by mass because the catalytic activity due to the use of nickel is not sufficiently exhibited. On the other hand, if it exceeds 25% by mass, the degree of dispersion of nickel on the surface of the carrier will be low, and as a result, high catalytic activity will not be exhibited.

  Further, in the reforming catalyst of the present invention, it is further preferable that at least iron is included as a constituent component together with barium hexaaluminate and nickel.

  In the present invention, by using iron together with barium hexaaluminate and nickel, agglomeration of nickel is suppressed, and the metal dispersion degree of nickel is improved, so that many active sites are maintained and tar reforming ability is improved. Can do. In addition, the combustion activity of burning and removing tar and deposited carbon adhering to the catalyst can be improved, and the catalyst can be regenerated at a lower temperature.

  When iron is used as a component of the reforming catalyst, the amount of iron used is preferably such that the molar ratio of nickel: iron is within the range of 10: 1 to 1: 3. This is not preferable when the molar ratio of nickel: iron is less than 10: 1 because the effect of suppressing the aggregation of nickel is not sufficiently exhibited. Further, when the molar ratio of nickel: iron is larger than 1: 3, the active sites on nickel are covered with iron, and the nickel reforming activity is not sufficiently exhibited, which is not preferable.

  Further, in the reforming catalyst of the present invention, it is even more preferable that at least platinum is contained as a constituent component together with barium hexaaluminate, nickel, and iron.

  In the present invention, by using platinum together with barium hexaaluminate, nickel, and iron, dissociative adsorption of hydrogen occurs on platinum reduced earlier than other metals because of the ease of reduction of platinum. The induction period of hydrogen can be shortened.

  When using platinum as a structural component of the reforming catalyst, the amount of platinum used is preferably in the range of 0.01 to 1.0 mass% with respect to the reforming catalyst.

  In the reforming catalyst of the present invention, in addition to the components described above, cobalt (Co), ruthenium (Ru), rhodium (Rh), manganese (Mn), cerium (Ce) as long as the effects of the present invention are not impaired. In addition, a component of a generally known reforming catalyst such as palladium (Pd) can also be included. In particular, there are cobalt, ruthenium and rhodium as catalyst types that can be used in place of or in combination with nickel, manganese and cerium that can be used in place of or in combination with iron, and rhodium, ruthenium, and palladium that can be used in place of or in combination with platinum. , Preferably in terms of obtaining the same effect as each of iron and platinum.

  Although the shape of the catalyst is not described here, any catalyst shape such as a honeycomb shape, a ring shape, or a column shape may be used.

In the method for producing synthesis gas in which the reforming catalyst of the present invention is used, biomass is used as a raw material, and the biomass of the raw material is represented by, for example, C _x H _y O _z and is particularly limited. Agricultural biomass such as rice straw and wheat straw, rice husks, herbs, etc., or remaining forest land, sawmill waste, pruned branches, fruit tree pruned branches, building demolition waste, new extension waste, etc. Woody biomass is preferred.

  In particular, rice biomass such as rice straw and wheat straw, and agricultural biomass such as rice husks are more preferable because energy required for pretreatment such as crushing can be reduced.

  In the method for producing synthesis gas using the biomass of the present invention as a raw material and producing hydrogen and carbon monoxide by a reforming reaction using the catalyst, the above-described reforming catalyst is used as the catalyst. By using such a reforming catalyst, the yield of synthesis gas obtained from raw material biomass can be increased, and a desired synthesis gas can be obtained.

As one embodiment of the method for producing synthesis gas according to the present invention, the following steps (1) and (2), that is,
(1) A partial oxidation step in which biomass is decomposed thermochemically and partially oxidized to obtain hydrogen, carbon monoxide, tar content, carbon content, ash content and heat (2) Other than the ash content obtained in the partial oxidation step Examples include a method including a reforming step of introducing a product into the above-described reforming catalyst and reacting the product with water vapor using heat obtained in the step.

  The partial oxidation reaction (1) can be performed using an oxidizing gasifying agent such as pure oxygen, oxygen-enriched air, or air. The “oxygen-enriched air” is a gas having a high oxygen partial pressure obtained by a known technique using an oxygen-enriched film or PSA (Pressure Swing Adsorption).

The reforming step (2) is preferably performed in a temperature range of 300 to 1100 ° C., and hydrogen (H ₂ ) and carbon monoxide (CO) are generated in a temperature range of 500 to 700 ° C. More preferably. By carrying out the reforming in such a temperature range, partial oxidation can be performed at a lower temperature, the amount of combustion of the raw material biomass can be reduced, and as a result, synthesis with a high yield and a high H ₂ / CO ratio Gas can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to such examples.

1. Catalyst preparation

[BaAl ₁₂ O ₁₉ carrier preparation method]
Alumina (Al ₂ O ₃ , surface area: 100 m ² / g) and BaCO ₃ were physically mixed so that (BaO) _0.14 (Al ₂ O ₃ ) _0.86 . This was fired at 1400 ° C. for 12 hours, allowed to cool, and then pressed at a pressure of 400 kgf / cm ² to form a tablet. This was pulverized appropriately in a mortar, and the particle size was adjusted to 177 to 590 μm using a sieve to prepare BaAl ₁₂ O ₁₉ .

[Ni 4, 12% by mass—BaAl ₁₂ O ₁₉ catalyst preparation method]
Prepare an aqueous solution using nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O) so that the content of Ni is 4 mass% and 12 mass%, respectively, in the BaAl ₁₂ O ₁₉ obtained above, and impregnation Nickel was supported by the method. Firing was performed at 500 ° C. for 3 hours.

[Ni 4, 12% by mass, Fe / BaAl ₁₂ O ₁₉ catalyst preparation method]
_BaAl 12 _{O 19} on the content, respectively 4 wt% of Ni obtained above, 12 weight%, and Ni: the molar ratio of Fe 4: 1 to become as nickel nitrate _{(Ni (NO 3) 2 ·} 6H _An aqueous solution was prepared using ₂ O) and iron nitrate (Fe (NO ₃ ) ₃ · 9H ₂ O), and nickel and iron were supported by an impregnation method. Firing was performed at 500 ° C. for 3 hours.

[Pt 0.1% by mass, Ni 12% by mass, Fe / BaAl ₁₂ O ₁₉ catalyst preparation method]
In the BaAl ₁₂ O ₁₉ obtained above, nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O) and a Ni content of 12% by mass and a Ni: Fe molar ratio of 4: 1 and An aqueous solution was prepared using iron nitrate (Fe (NO ₃ ) ₃ · 9H ₂ O), and nickel and iron were supported by an impregnation method. Firing was performed at 500 ° C. for 3 hours. Next, an aqueous solution was prepared using platinum diaminonitrite ((NH ₃ ) ₂ Pt (NO ₂ ) ₂ ) so that the Pt content was 0.1% by mass, and platinum was supported by an impregnation method. Firing was performed at 500 ° C. for 3 hours.

2. Evaluation method
Using the apparatus shown in FIG. 1, biomass gasification experiments were conducted to evaluate the performance of the catalyst for biomass gasification. The conceptual diagram of the apparatus used for evaluation of a present Example is shown in FIG.

  In FIG. 1, reference numeral 1 denotes a thermal decomposition section, which includes a dispersion plate / communication passage 8 between the thermal decomposition section 1 and the tar reforming section 2, gas injection ports 4, 5, 6 and the like. Reference numeral 2 denotes a tar reforming section, which includes a dispersion plate / communication passage 8 and a synthesis gas discharge port 12 for the thermal decomposition section 1 and the tar reforming section 2. The dispersion plate / communication passage 8 is for flowing gas after supporting the catalyst particles.

  Next, the process from biomass to synthesis gas generation will be described in order. First, raw material biomass is supplied from, for example, the gas inlet 3 of FIG. The supplied biomass is supplied to the pyrolysis unit 1 as it is or after it is once accumulated in the biomass supply tank in the biomass feeder 7. In the pyrolysis section 1, the biomass is pyrolyzed in the temperature range of 300 to 1100 ° C. for 0.1 to 10 seconds, preferably in the temperature range of 500 to 700 ° C. for 0.2 to 2 seconds. As a result, the biomass is separated into a solid component 9 made of solid carbon, ash and the like, and a gas component made of gaseous tar and the like. Here, it is important to adjust the temperature so that tar becomes a gas component. This is because if it is a gas component, it can be separated from the solid component 9 such as solid carbon and separately introduced into the tar reforming section 2 that generates synthesis gas.

  The separated gas component such as gaseous tar is, for example, along with the flow of gas from the gas injection ports 3, 5, 6, etc. The tar reforming unit 2 is introduced.

  Although the dispersion plate / communication passage 8 may have any shape, the catalyst 10 of the tar reforming unit 2 is prevented from flowing out of the tar reforming unit 2. For example, it is good also as a structure which becomes below from the thermal decomposition part 1 to the tar reforming part 2. FIG. In the tar reforming unit 2, the separated gas component and water vapor react in the presence of the catalyst 10 to generate synthesis gas. The synthesis gas is discharged from the synthesis gas outlet 12.

  The biomass subjected to gasification is 10.4% moisture, 48.9% C, 6.59% H, 44.0% O, 0.14% N, 0.01% S, 0.05% Cl, A timber composed mainly of cedar composed of ash content of 0.36% is used to make a sized particle of 177 μm or less (wood powder). The catalyst 10 provided is shown in the left column of Table 1. Five of these were used which were each subjected to reduction treatment under a hydrogen stream. The reduction treatment was performed at 500 ° C. for 30 minutes.

In the apparatus of FIG. 1, the catalyst amount of the catalyst 10 is about 1 g, wood powder as biomass is supplied from the biomass feeder 7 as 60 mg / min (2328 μmol / min), and water vapor supplied from the gas inlet 5 is 20 μl / min. Then, gasification was performed by supplying 30 ml / min of nitrogen from the gas inlet 3 and 30 ml / min of nitrogen from the gas inlet 6. The reaction temperature is set to three patterns of 650 ° C., 600 ° C. and 550 ° C. by external heat from an electric furnace (not shown) attached to the periphery of the reaction tube in the apparatus of FIG. After 1 minute, sampling of the product gas was started, and the production rate (μmol · min ⁻¹ ) and carbon conversion rate of CO, H ₂ , CO ₂ , and CH ₄ in the synthesis gas 12 produced using GC-TCD and FID (% -C) was measured respectively.

The calculation method of carbon conversion rate is
Carbon conversion rate (% -C) = (CO + CO ₂ + CH ₄ + 2 × C ₂ hydrocarbon production rate) / (carbon supply rate in biomass) × 100
It is.

After the reaction time of 15 minutes has elapsed, the temperature is stabilized at 600 ° C., oxygen is introduced from the gas inlet 4, the carbon adhering to the catalyst 10 is combusted, oxygen is then introduced from the gas inlet 6, and the reaction tube The solid carbon deposited on the deposition plate 11 was burned, carbon dioxide in the combustion gas was measured every minute using GC-TCD, and the carbon yield deposited on the catalyst from each amount (% -C ), And the solid carbon yield (% -C) was calculated. The tar yield (% -C) was also calculated.
The carbon yield deposited on the catalyst was defined as the coke yield, and the results of the examples were described.

The tar yield calculation method is as follows:
Tar yield (% -C) = 100-carbon conversion-coke yield-solid carbon yield.

  The results are shown in Table 1. In the column of each catalyst in Table 1, the upper part shows the result at a reaction temperature of 650 ° C., the middle part shows the result at a reaction temperature of 600 ° C., and the lower part shows the result at a reaction temperature of 550 ° C.

As is apparent from the results shown in Table 1, when a catalyst (bottom three catalysts in Table 1) containing barium aluminate (BaAl ₁₂ O ₁₉ ) was used as a catalyst in the reforming reaction (Example), alumina was used. Compared to the case where a catalyst containing (Al ₂ O ₃ ) (the upper two catalysts in Table 1) is used (comparative example), the amount of coke and tar are reduced, the carbon conversion rate is increased, and the synthesis gas ( It can be seen that the yield of CO + H ₂ ) tends to be high.

  The present invention has industrial applicability as a reforming catalyst having high heat resistance for producing synthesis gas from biomass at a higher yield. In addition, the present invention has a high carbon combustion activity so that the regeneration by the combustion can be performed at a lower temperature, as well as heat resistance, which is a countermeasure against a high temperature when the catalyst is regenerated by removing the carbon by combustion, and its combustion As a steam reforming catalyst with easy reducibility to facilitate regeneration by reduction of deactivation caused by metal oxidation by, and synthesis gas production with higher yield from biomass as raw material As a method, it has industrial applicability.

DESCRIPTION OF SYMBOLS 1 Thermal decomposition part 2 Tar reforming part 3 Gas inlet 4 Gas inlet 5 Gas inlet 6 Gas inlet 7 Biomass feeder 8 Dispersion plate and communication path 9 Solid component 10 Catalyst 11 Deposit plate 12 Syngas outlet

Claims (11)

A steam reforming catalyst that introduces hydrogen, carbon monoxide, tar content, carbon content and ash content products other than the ash content obtained by thermochemically decomposing and partially oxidizing the biomass and reacting with steam. ,
A biomass gasification reforming catalyst characterized by using iron together with nickel in barium hexaaluminate to enable regeneration by burning and removing attached tar and precipitated carbon.   The biomass gasification reforming catalyst according to claim 1, wherein the molar ratio of nickel: iron is in the range of 10: 1 to 1: 3.   The biomass gasification reforming catalyst according to claim 2, comprising nickel in the range of 1 to 25 mass%. A steam reforming catalyst that introduces hydrogen, carbon monoxide, tar content, carbon content and ash content products other than the ash content obtained by thermochemically decomposing and partially oxidizing the biomass and reacting with steam. ,
Barium with nickel hexaaluminate by combination of iron and platinum, deposited tar and features and to Luba Iomasugasu of reforming catalysts that due precipitated burn off carbon and enabling reproduction.   The biomass gasification reforming catalyst according to claim 4, wherein platinum is contained within a range of 0.01 to 1.0 mass%.   The biomass gasification reforming catalyst according to any one of claims 1 to 5, wherein the biomass is agricultural biomass.   The biomass gasification reforming catalyst according to any one of claims 1 to 5, wherein the biomass is woody biomass. A partial oxidation step in which the biomass is thermochemically decomposed and partially oxidized to obtain products of hydrogen, carbon monoxide, tar, carbon and ash;
A steam reforming step of introducing the product other than the ash and reacting with steam,
The method for producing synthesis gas, wherein the steam reforming step is caused to react in the presence of a biomass gasification reforming catalyst comprising one of claims 1 to 5.   The method for producing synthesis gas according to claim 8, wherein the steam reforming step is a step of using heat obtained in the partial oxidation step.   The method for producing synthesis gas according to claim 8 or 9, wherein at least part of heat necessary for the partial oxidation step and the steam reforming step is supplied by external heat. The method for producing a synthesis gas according to claim 8, wherein the partial oxidation step and the steam reforming step are performed in a temperature range of 300 to 1100 ° C.