RU2290363C1 - Hydrogen generation method - Google Patents

Abstract

FIELD: hydrogen production processes.

SUBSTANCE: invention relates to catalytic processes of hydrogen production from hydrocarbon-containing gases. Method of invention comprises elevated-pressure catalytic decomposition of methane and/or natural gas into hydrogen and carbon followed by gasification of the latter with the aid of gasification reagent in several in parallel installed interconnected reactors, each of them accommodating preliminarily reduced catalyst bed. When one of reactors is run in methane and/or natural gas decomposition mode, the other gasifies carbon, the both operation modes being regularly switched. Operation period in one of the modes ranges from 0.5 to 10 h. Carbon gasification reagent is, in particular, carbon dioxide and catalyst utilized is reduced ferromagnetic thermally stabilized product consisting of iron oxides (30-80 wt %) and aluminum, silicon, magnesium, and titanium oxides. Methane and/or natural gas is decomposed at 625-1000°C and overpressure 1 to 40 atm.

EFFECT: ensured environmental safety and increased productivity of process.

3 cl, 1 dwg, 8 ex

Description

The invention relates to catalytic processes for producing hydrogen and carbon from hydrocarbon-containing gases. Hydrogen after its separation from a gas mixture can be used as a reducing agent in various industries of the chemical, metallurgical and other industries, as well as a reagent for fuel cells of vehicles and autonomous sources of electric energy.

A known method of producing hydrogen and fibrous carbon by decomposing a hydrocarbon-containing gas at an elevated temperature on a catalyst, comprising a ferromagnetic thermally stabilized product recovered by hydrogen, isolated by magnetic separation of ash from burning coal in thermal power plants. The catalyst is a structure consisting of 18-90% iron oxides and containing aluminum, magnesium and silicon oxides - the rest, and the process is conducted at a pressure of 1-40 at and a temperature of 500-1200 ° C (Application for the grant of a patent of the Russian Federation No. 2004137196 from 12/20/04 according to class IPC С 01 В 31/26).

The main disadvantage of this method is that the process of pyrolysis of methane and / or natural gas is carried out until the catalyst is completely deactivated with a corresponding drop in time of hydrogen output to zero and the conditions for catalyst regeneration are not determined.

Also known is a high-temperature method for producing hydrogen by decomposing methane on a Ni / SiO ₂ catalyst with gasification of the carbon deposited on the catalyst using CO ₂ (S. Takenaka, K. Otsuka. Specific reactivity of the carbon filaments formed by decomposition of methane over Ni / SiO ₂ catalyst : gasification with CO _2. Chem. Lett. 2001.218-219).

The disadvantages of the method are the relatively low activity of the catalyst and its resistance to deactivation.

Closest to the claimed invention is a continuous method for producing hydrogen at a relatively low process temperature (about 650 ° C) using methane and / or natural gas and steam, as well as a catalytically active metal of the 8th group of the periodic system of elements (Patent EP No. 1227062 Cl. C 01 B 3/26, B 01 J 08/06 B, 2002).

The process is carried out in two parallel reactors, each of which is placed the required amount of catalyst. The catalyst is subjected to reduction using the corresponding component, and then methane and / or natural gas is supplied to one of them, and steam is transferred to the other with regular switching of the supply of these components from one reactor to another. In this case, the combined gas stream contains a sufficient amount of hydrogen. The process is carried out at a pressure close to atmospheric. The time for switching the supply of components to the reactors is 5-15 minutes.

The obvious disadvantages of this method of producing hydrogen are the high cost of the catalysts used (due to the use of Ni, Co, Zr, etc.), the complexity of their preparation and relatively low activity, the short time of switching the supply of reagents from one reactor to another. In addition, the contamination of the combined gas stream with carbon oxides does not allow its direct use as an energy carrier for hydrogen fuel cells.

The aim of the present invention is the creation of environmentally friendly production of hydrogen as a result of the use of carbon dioxide as an agent, gasifying carbon deposited on the catalyst. This reduces the emission and emission of carbon dioxide into the atmosphere, which is formed in large quantities when water is used as a gasification agent, and, accordingly, does not affect the increase in the greenhouse effect. In addition, a valuable product is obtained, which is carbon monoxide, which is widely used in various fields of the chemical industry for organic synthesis. The increase in the duration of the reactor in one mode increases the productivity of the process of obtaining the target product.

The proposed method for the continuous production of hydrogen involves catalytic decomposition at a temperature of 625-1000 ° C and a pressure of 1-40 ati methane and / or natural gas into hydrogen and carbon in several reactors installed in parallel and interconnected. A pre-reduced layer of iron-containing catalyst is placed in each of the reactors, in which iron is represented as oxides. Iron oxides are part of the recovered ferromagnetic thermally stabilized product isolated from ash from burning coal in thermal power plants by magnetic separation followed by particle size and hydrodynamic classification and consisting of iron oxides in an amount of 30-80 wt.% In a composition with aluminum oxides, silicon, magnesium, titanium. Further, methane and / or natural gas is supplied to one of the reactors for 0.5-10 hours, and it operates in the decomposition mode of methane and / or natural gas. After that, the supply of methane and / or natural gas is stopped, the reactor is switched to gasification mode and carbon dioxide is fed into it as a reagent, gasification carbon. And the supply of methane and / or natural gas begins in another reactor. Moreover, switching the supply of reagents from one reactor to another is carried out as the catalyst is deactivated, which is reduced after gasification of carbon with hydrogen-containing gas leaving the first reactor.

Distinctive features of the proposed technical solution are: the duration of the reactor in one of the modes of decomposition of methane and / or natural gas or carbon gasification of 0.5-10 hours, the use of carbon dioxide as a gasifying carbon reagent, and as a catalyst for the decomposition of methane and / or natural gas reduced ferromagnetic thermally stabilized product consisting of iron oxides in an amount of 30-80 wt.%, oxides of aluminum, silicon, magnesium, titanium.

Other distinctive features are the methane decomposition process at a temperature of 625-1000 ° С and a pressure of 1-40 ati.

In addition, the recovered ferromagnetic thermally stabilized product is obtained from ash obtained by burning fossil fuels at thermal power plants by magnetic separation, followed by particle size and hydrodynamic classification.

The combination of the above essential features of the present invention will reduce the emission and emission of carbon dioxide into the atmosphere, which is formed in large quantities when using water as a gasification agent. This gives a valuable product, which is carbon monoxide, which is widely used in various fields of the chemical industry for organic synthesis, as well as to increase the productivity of the process of obtaining the target product.

The gasification of methane and / or natural gas formed during the catalytic pyrolysis of carbon and natural gas using carbon dioxide as a gasification agent allows the catalyst to be regenerated and reused in the future, with the use of greenhouse gas (CO ₂ ) in the process of producing hydrogen, thereby reducing its emission in atmosphere, to produce a valuable product for the chemical and other industries - CO.

The drawing shows a schematic diagram of an installation for implementing a method of continuous production of hydrogen.

The installation includes: reactors 1 and 2, in which layers 3 and 4 of the reduced iron-containing catalyst are placed, pipes 5 and 6 for supplying methane and / or natural and carbon dioxide, a multi-way valve 7 for switching incoming reagents, pipelines 8 and 9 for supplying reagents to reactors 1 and 2, nozzles 10 and 11 for withdrawing hydrogen and carbon monoxide from the reactors, respectively, a multi-way valve 12 for switching exiting reagents and evacuating them through nozzles 13 and 14 from the process.

The method is as follows.

Methane and / or natural gas through pipe 5 through a multi-way valve 7 from a source (not shown) and pipe 8 enters reactor 1, where the decomposition of hydrocarbons proceeds on the catalyst bed 3 to form carbon and hydrogen. Hydrogen-containing gas through the pipe 10 through the multi-way valve 12 through the pipe 13 leaves the installation. The duration of the reactor 1 in the decomposition mode of methane and / or natural gas is 0.5-10 hours. After that, carbon dioxide is supplied to the reactor 1 through a multi-way valve 7 from a source (not shown) through a pipe 5 and a pipe 8 for gasification of carbon. The formed carbon monoxide through a multi-way valve 12 through the pipe 13 is removed from the installation.

At the same time, methane and / or natural gas is supplied through the pipe 6 through a multi-way valve 7 from a source (not shown) and the pipe 9 enters the reactor 2, where the decomposition of hydrocarbons proceeds on the catalyst bed 4 to form carbon and hydrogen. Hydrogen-containing gas through the pipe 11 through the multi-way valve 12 through the pipe 14 leaves the installation. The duration of the reactor 2 in the decomposition mode of methane and / or natural gas is 0.5-10 hours. After that, carbon dioxide is supplied to the reactor 2 through a multi-way valve 7 from a source (not shown) through a pipe 6 and a pipe 9 for gasification of carbon. The formed carbon monoxide through a multi-way valve 12 through the pipe 14 is removed from the installation. Then the feed flow is switched.

The invention is illustrated by the following examples.

Example 1 (prototype). The process is carried out in two parallel reactors, each of which is placed the required amount of catalyst. The catalyst is reduced using the corresponding component, and then methane and / or natural gas is supplied to one of them, and steam is transferred to the other with regular switching of the supply of these components from one reactor to another. The catalyst, consisting of NiO-ZrO ₂ (molar ratio Ni / Zr = 1.0), is reduced with a nitrogen-hydrogen mixture (5 mol% H ₂ ) at 601 ° C and a mixture volume velocity of 4230 cm ³ / g _cat. hour for 10 hours. Then, the nitrogen-hydrogen mixture is replaced by nitrogen-methane (71.4 mol% CH ₄ ) and at a temperature of 613 ° C, the process of producing hydrogen is carried out for 5 minutes. Then, instead of the nitrogen-methane mixture, water vapors (83.7 mol% in nitrogen) are fed into the reactor and, at a temperature of 610 ° C, the previously formed carbon is removed (gasified) also within 5 minutes. The hydrogen productivity of methane and / or natural gas is 91.6 mmol / g _cat. hour. In this case, due to the reaction of steam gasification of carbon, CO (6.1 mmol / g _cat. Hour) and CO ₂ (39.6 mmol / g _cat. Hour) are formed.

Example 2 (prototype). Similar to example 1. Differences: in the recovery of the catalyst, the space velocity of the nitrogen-hydrogen mixture is 15050 cm ³ / g _cat. an hour with a hydrogen content of 20 mol%, a temperature of 520 ° C, a recovery time of 1 hour; during the pyrolysis reaction of methane and / or natural gas, the space velocity of the nitrogen-methane mixture is 10320 cm ³ / g _cat. hour at a methane content of 50 mol% and 590 ° C; during the gasification of carbon, the space velocity of the vapor-nitrogen mixture (80.9 mol%) is 6773 cm ³ / g _cat. hour, temperature 587 ° C. The time interval between switching feed flows is 7 minutes. The hydrogen productivity of methane is 75 mmol / g _cat. hour. Due to the gasification reaction, the formation of 37.4 mmol / g _cat. hour of CO ₂ .

Example 3 (according to the invention). The catalyst containing wt.%: 59.2 Fe ₂ About ₃ , 8.8 Al ₂ About ₃ , 26.0 SiO ₂ , 1.5 MgO, 0.69 TiO ₂ , restore hydrogen for 5 hours at a space velocity of 45,000 cm ³ / g _cat. hour and a temperature of 650 ° C. Then, hydrogen is replaced with methane and / or natural gas, and at a temperature of 650 ° C and a pressure of 15 atm, a hydrogen production process is carried out for 10 hours. Then, instead of methane and / or natural gas, carbon dioxide is supplied to the reactor at a space velocity of 45,000 cm ³ / g _cat. hour and at a temperature of 800 ° C and 1 ati for 10 hours, gasification of previously formed carbon is carried out with the formation of CO. The hydrogen productivity of methane and / or natural gas is 180.8 mmol / g _cat. hour. The average carbon monoxide emission is also 180.8 mmol / g _cat. hour.

Example 4. Similar to example 3. Differences: the temperature of the recovery of the catalyst 600 ° C; pyrolysis temperature of methane and / or natural gas 650 ° C, duration 4 hours; gasification process temperature 750 ° C, duration 4 hours. Productivity for hydrogen and carbon monoxide 200.9 mmol / g _cat. hour.

Example 5. Similar to example 3. Differences: the temperature of recovery of the catalyst 750 ° C; the pyrolysis temperature of methane and / or natural gas is 750 ° C, the duration of the reactor is 4 hours; gasification process duration 4 hours. Productivity for hydrogen and carbon monoxide 421.9 mmol / g _cat. hour.

Example 6. Similar to example 3. Differences: the catalyst is reduced with a mixture of hydrogen and argon (10.2% vol. N ₂ ) at a space velocity of 30,000 cm ³ / g _cat. hour and at a temperature of 688 ° C for 1 hour; the duration of the pyrolysis of methane and / or natural gas is 3 hours; gasification duration 3 hours. Productivity for hydrogen and carbon monoxide 502.2 mmol / g _cat. hour.

Example 7. Similar to example 3. Differences: the composition of the used catalyst wt.%: 69.5 Fe ₂ O ₃ , 7.5 Al ₂ About ₃ , 22.2 SiO ₂ , 2.0 MgO, 0.8 TiO ₂ . Productivity for hydrogen and carbon monoxide 221.0 mmol / g _cat. hour.

Example 8. Similar to example 3. Differences: the temperature of the recovery of the catalyst 600 ° C; the duration of the pyrolysis of methane and / or natural gas for 2 hours at 700 ° C and a pressure of 1 MPa; the duration of the gasification process is 2 hours. Productivity for hydrogen and carbon monoxide 130.6 mmol / g _cat. hour.

Thus, an analysis of the above experimental materials shows that the iron-containing catalysts used, characterized by a strong interaction of the active component with the carrier, in this cyclic process have high activity and a stable level of performance over many cycles. Moreover, in the process of gasification of the formed carbon, there is a consumption of carbon dioxide, which belongs to the class of greenhouse, and intensive formation of carbon monoxide, which is a valuable chemical product. The selected interval of the cycle duration enhances the processability.

Claims (3)

1. A method for the continuous production of hydrogen, including catalytic decomposition at elevated temperatures of methane and / or natural gas into hydrogen and carbon and gasification of the latter with a gasification agent in several reactors installed in parallel and interconnected, each of which contains a previously reduced catalyst layer, moreover, when one of the reactors is operating in the decomposition mode of methane and / or natural gas, the other at this time is operating in the mode of gasification of carbon, while the reactors brightly switch from one operating mode to another, characterized in that the duration of the reactor in one of the modes of decomposition of methane and / or natural gas or carbon gasification is 0.5-10 hours, carbon dioxide is used as a gasification carbon reagent, and as The decomposition catalyst for methane and / or natural gas uses a reduced ferromagnetic thermally stabilized product consisting of iron oxides in an amount of 30-80 wt.%, oxides of aluminum, silicon, magnesium, titanium. 2. The method of continuous production of hydrogen according to claim 1, characterized in that the decomposition of methane and / or natural gas is carried out at a temperature of 625-1000 ° C and a pressure of 1-40 MPa. 3. The method of continuous production of hydrogen according to claim 1, characterized in that the recovered ferromagnetic thermally stabilized product is obtained from ash obtained by burning fossil fuels at thermal power plants by magnetic separation, followed by particle size and hydrodynamic classification.