RU2213691C1 - Method of producing synthesis gas or hydrogen-enriched gas mixture from water-alcohol mixtures - Google Patents

Abstract

FIELD: alternate fuels. SUBSTANCE: invention relates to catalytic method for steam conversion of ethanol to produce synthesis gas or hydrogen-enriched gas mixture, which can find use in a variety of areas including hydrogen power engineering as fuel for fuel elements. Method is implemented in reactor with two fixed catalyst beds. First-bed catalyst contains, as active component (at least 0.05 wt %), 16- group metal (copper, silver, gold) and/or precious metal selected from platinum, palladium, ruthenium, rhodium, and iridium deposited on graphite-like carbon support. Second-bed catalyst contains VIII-group metal selected from nickel, platinum, palladium, ruthenium, rhodium, and iridium. Reaction mixture entering second catalyst bed is preliminarily supplemented with oxygen or carbon dioxide with concentration no higher than 50 vol %. EFFECT: increased efficiency of steam conversion of alcohol due to use of water-ethanol mixture containing methanol and prevented deactivation of catalyst and formation if by-products. 10 cl, 8 tbl, 5 ex

Description

 The invention relates to a catalytic method for carrying out a steam reforming reaction of ethanol to produce synthesis gas or a hydrogen-rich gas mixture, which can be used in various industries, including hydrogen energy, for example, as fuel for fuel cells.

 It is known that ethanol is a widely available renewable raw material, the industrial production technologies of which are well developed - for example, the biochemical processing of sugar cane, grain crops or wood. The resulting bioethanol is an aqueous solution containing about 12 wt.% Ethanol. Especially attractive would be the processes that allow the processing of bioethanol without distillation. Such a process is the steam reforming of ethanol to produce synthesis gas or hydrogen-rich gas mixtures.

 It is known that the possibility of producing hydrogen by ethanol steam reforming is thermodynamically confirmed (K. Vasudeva, N. Mitra, P. Umasankar, D. Dhiugra, Int. J. Hydrogen Energy, Steam reforming of ethanole for hydrogen production: thermodynamic analysis, 21 (1996) 113; I. Fishtik, A. Alexander, R. Datta, D. Geana, Int. J. Energy, A thermodynamic analysis of hydrogen production by steam reforming of ethanol via response reactions 25 (2000) 31), while the main hydrogen-containing product methanol is a steam reforming of ethanol at moderate temperatures, whereas at high temperatures and large molar ratios of water / ethanol a predominantly hydrogen-containing mixture is formed.

 A known method for the steam conversion of ethanol on cobalt-containing catalysts using oxide and carbon carriers (F. Haga, T. Nakajama, H. Miya, S. Mishima, Catal. Lett. Catalytic properties of supported cobalt catalysts for steam reforming of ethanol, 48 (1997) 223). The disadvantage of this method is the formation of by-products, such as methane, methanol, ethylene, acetaldehyde, diethyl ether. It is also well known that, in the presence of ethylene, carbon formation on the catalyst is significantly enhanced (JR Rosrup-Nielsen, Catalytic steam reforming, Catalysis Science and Technology, Eds. JR Anderson and M. Boudart, v.5, Ch.l, Springer-Verlag, Berlin, 1984).

A known method of producing a hydrogen-rich gas mixture by steam ethanol conversion on potassium-promoted Ni- and Cu-containing catalysts supported on Al ₂ O ₃ (FJ Marino, EG Cerrela, S. Dunalde et al., J. Hydrogen Energy, Hydrogen from steam reforming of ethanol. Characterization and performance of copper-nickel supported catalysts, 23 (1998) 1095). The main disadvantages of this method of conducting the steam conversion of ethanol into a hydrogen-rich mixture are the low conversion of ethanol, the formation of by-products (such as methane, acetaldehyde, diethyl ether). A disadvantage is the need to complicate the catalytic system (the introduction of potassium-containing promoter) to reduce the formation of by-products.

In addition, a method is known in which the hydrogen production process is carried out in a reactor with two fixed catalyst beds using a Cu / SiO ₂ catalyst in the first stage (S. Freni, N. Mondello, S. Cavallaro, G. Cacciola, VN Parmon, VA Sobyanin, React. Kinet. Catal. Lett., Hydrogen production by steam reforming of ethanol two step process, 71 (2000) 143). At this stage, acetaldehyde is formed from ethanol, the steam conversion of which in the second stage on the Ni / MgO catalyst leads to the formation of a hydrogen-rich gas mixture. The disadvantage of this method is the rapid deactivation of the catalyst Cu / SiO ₂ .

 The closest is the method (VD Belyaev, VV Galvita. VN Parmon, GL Semin, VA Sobyanin, PG Tsyrulnikov. The catalyst and method for producing synthesis gas or enriched hydrogen gas mixture from water-alcohol mixtures, RF Patent 2177366, 7 V 01 J 23/40, C 01 B 3/00, 12/27/2001) obtaining a hydrogen-rich gas mixture in a reactor with two fixed catalyst beds, where, as a catalyst, the first the layer using a catalyst containing as an active component a metal of group I of the Periodic system (copper, silver, gold) and / or a hydrogen metal selected from the group consisting of platinum, palladium, ruthenium, rhodium, iridium supported on a graphite-like carbon support, and a catalyst containing a metal of group VIII of the Periodic system selected from the group consisting of nickel, platinum is used as a second layer catalyst , palladium, ruthenium, rhodium, iridium, for example, use the well-known industrial nickel-containing catalysts for the conversion of methane GIAP-16 (Reference Nitrogen // Ed. Melnikova E.Ya. M .: Chemistry, 1986. 512 p.). The disadvantages of this method are the presence of a by-product (methane), as well as a rather high content of carbon monoxide in the products, which is a poison for low-temperature fuel cells. This does not allow the use of the resulting gas mixture to power low-temperature fuel cells without significant costs to reduce the concentration of carbon monoxide.

 The problem to which the present invention is directed, is to increase the efficiency of the process of steam conversion of alcohol in order to obtain a hydrogen-enriched gas mixture by preventing catalyst deactivation and reducing the formation of by-products.

 The problem is solved by the method of producing synthesis gas or a hydrogen-enriched gas mixture by steam reforming of alcohols in a reactor with two fixed catalyst beds, and oxygen or carbon dioxide at a concentration of not higher than 50 vol% are preliminarily introduced into the reaction mixture.

As the alcohol, ethanol or a methanol-ethanol mixture is used in the form of a water-alcohol mixture having an alcohol concentration of from 1 to 50 vol.%. The process in the first layer is carried out at a temperature not lower than 200 ^o С, in the second layer - not lower than 500 ^o С.

 Depending on what is used in the first catalyst bed, the steam conversion process can be carried out in two ways.

(1) Ethanol or a water-ethanol mixture on the first catalyst bed (catalysts: platinum, palladium, ruthenium, rhodium, iridium) is converted into a mixture of CO, CH ₄ and H ₂ gases by reaction
C ₂ H ₅ OH = CH ₄ + CO + H ₂ , (1)
which then on the second catalyst bed is converted into synthesis gas or a hydrogen-rich gas mixture according to the reactions:
CH ₄ + 2H ₂ O = CO ₂ + 4H ₂ ; (2)
H ₂ + CO ₂ = CO + H ₂ O (3)
When oxygen is introduced after the first layer into the reaction mixture, along with reactions (2) and (3), reaction (4) proceeds:
CH ₄ + 0.5O ₂ = CO + 2H ₂ . (4)
(2) Ethanol or a water-ethanol mixture on the first catalyst bed (catalysts: copper, silver, gold) is converted to acetaldehyde and hydrogen by reaction
C ₂ H ₅ OH = CH ₃ CHO + H ₂ (5)
and then on the second catalyst bed the mixture of acetaldehyde and hydrogen is converted to synthesis gas or a hydrogen-rich gas mixture by reactions
CH ₃ CHO + 3H ₂ O = 2CO ₂ + 5H ₂ (6)
H ₂ + CO ₂ = CO + H ₂ O. (7)
When oxygen is introduced after the first layer into the reaction mixture, along with reactions (6) and (7), reaction (8) proceeds
CH ₃ CHO + 0.5O ₂ = 2CO + 2H ₂ . (8)
The ethanol steam reforming reaction is carried out in a flow reactor with two fixed catalyst beds. The reactor was a quartz tube with an inner diameter of 8 mm. The layers consisted of 0.5-1 g of catalyst mixed with 5 g of inert SiC material. The space velocity varies in the range of 1000-100000 h ^-1 , the temperature of the first layer is 200-450 ^o С, the temperature of the second layer is 650-800 ^o С. The reaction proceeds in the pressure range 1-10 atm. The reaction gas mixture has a composition of from 1 to 50 vol.% C ₂ H ₅ OH in H ₂ O. All the data presented are obtained after the catalysts have been running for 25 hours.

 The invention is illustrated by the following examples.

 Example 1

The vapor conversion of ethanol into a hydrogen-rich mixture is carried out at atmospheric pressure in a flow reactor with two fixed catalyst beds. The process in the first layer is carried out on a catalyst of 1 wt.% Pd / C at a temperature of 330 ^o C, a space velocity of 2200 h ^-1 and atmospheric pressure. The reaction mixture consists of 11.2 vol.% C ₂ H ₅ OH + 88.8 vol.% H ₂ O. After the first layer, 3 vol.% O ₂ is introduced into the gas mixture. The second layer contains the industrial catalyst GIAP-16 in an amount of 1 g. The results obtained are shown in table 1. The data from the prototype are shown in table 1a.

 Example 2

The vapor conversion of ethanol into a hydrogen-rich mixture is carried out at atmospheric pressure in a flow reactor with two fixed catalyst beds. The first layer contains a catalyst of 15 wt.% Cu / C, and the process on it is carried out at a temperature of 340 ^o C, a space velocity of 100,000 h ^-1 and atmospheric pressure. The reaction mixture consists of 15.3 vol.% C ₂ H ₅ OH + 84.7 vol.% H ₂ O. After the first layer, 3.5 vol.% O ₂ is introduced into the gas mixture. The second layer contains the industrial catalyst GIAP-16 in an amount of 1 g. The results obtained are shown in table 2. The data from the prototype are shown in table 2a.

 Example 3

The vapor conversion of the ethanol-methanol mixture into a hydrogen-enriched mixture is carried out at atmospheric pressure in a flow reactor with two fixed catalyst beds. The reaction gas mixture consists of 10 vol.% C ₂ H ₅ OH + 10 vol. % CH ₂ OH + 80 vol.% H ₂ O. The first layer contains a catalyst of 1 wt.% Pd / C, and the process of steam conversion is carried out at a temperature of 330 ^o C and a volumetric flow rate of the mixture of 2200 h ^-1 . After the first layer, 3.5 vol.% O ₂ is introduced into the gas mixture. The second layer contains the industrial catalyst GIAP-16 in an amount of 1 g. The results are shown in table 3. The data from the prototype are shown in table 3a.

 Example 4

The vapor conversion of ethanol into a hydrogen-rich mixture is carried out at atmospheric pressure in a flow reactor with two fixed catalyst beds. The process in the first layer is carried out on a catalyst of 1 wt.% Pd / C at a temperature of 330 ^o C, a space velocity of 2200 h ^-1 and atmospheric pressure. The reaction mixture consists of 10 vol.% C ₂ H ₅ OH + 90 vol.% H ₂ O. After the first layer, 4 vol.% O ₂ is introduced into the reaction mixture. The second layer contains the industrial catalyst GIAP-16 in an amount of 1 g. The results obtained are shown in table 4.

 Example 5

The vapor conversion of ethanol into a hydrogen-rich mixture is carried out at atmospheric pressure in a flow reactor with two fixed catalyst beds. The process in the first layer is carried out on a catalyst of 1 wt.% Pd / C at a temperature of 330 ^o C, a space velocity of 2400 h ^-1 and atmospheric pressure. The reaction mixture consists of 11.2 vol.% C ₂ H ₅ OH + 88.8 vol.% H ₂ O. After the first layer, 3 vol.% CO ₂ is introduced into the reaction mixture. The second layer contains the industrial catalyst GIAP-16 in an amount of 1 g. The results obtained are shown in table 5.

 The above examples demonstrate the high activity, selectivity and stability of the proposed catalysts during the conversion of water-alcohol mixtures into a hydrogen-enriched gas mixture.

 The proposed method of processing ethanol, including bioethanol, into a hydrogen-enriched gas mixture allows the use of water-alcohol mixtures without distillation, which is of great technological importance. Catalysts have a wide possibility of varying their chemical composition. The proposed method allows to reduce the formation of by-products, as well as products that are poisons for low-temperature fuel cells.

Claims (10)

 1. A method for producing synthesis gas or a hydrogen-rich gas mixture by steam reforming of alcohols in a reactor with two fixed catalyst beds, a catalyst containing a metal of group I of the Periodic table and / or a noble metal deposited on a graphite-like metal as the active component is used as the first component catalyst carbon carrier, and as a catalyst for the second layer, a catalyst containing a metal of group VIII of the Periodic system is used, characterized in that the reaction mixture a second conductive layer of the catalyst, previously introduced oxygen or carbon dioxide in a concentration not exceeding 50 vol.%.  2. The method according to claim 1, characterized in that the catalyst of the first layer contains a metal selected from the group consisting of copper, silver, gold.  3. The method according to claim 1, characterized in that the catalyst of the first layer contains a metal selected from the group consisting of platinum, palladium, ruthenium, rhodium, iridium.  4. The method according to claims 1 to 3, characterized in that the catalyst of the first layer contains the active component in an amount of not less than 0.05 wt.%.  5. The method according to claim 1, characterized in that the second layer of the catalyst contains a metal selected from the group consisting of nickel, platinum, palladium, ruthenium, rhodium, iridium.  6. The method according to claims 1-5, characterized in that ethanol or a methanol-ethanol mixture is used as the alcohol. 7. The method according to any one of claims 1 to 6, characterized in that the process in the first layer is carried out at a temperature not lower than 200 ^o C. 8. The method according to any one of claims 1 to 7, characterized in that the process in the second layer is carried out at a temperature not lower than 500 ^o C.  9. The method according to any one of claims 1 to 8, characterized in that the reaction is carried out at a pressure of not lower than 0.1 atm.  10. The method according to any one of claims 1 to 9, characterized in that the alcohol is used in the form of a water-alcohol mixture having a concentration of from 1 to 50 vol.%.

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