RU2843003C1 - Adsorbent for extracting hydrogen from hydrogen-containing gas and method for producing adsorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to chemical engineering. Method of producing an adsorbent for extracting hydrogen involves preparation of a finely dispersed catalyst suspension. For this purpose, in a ball mill to one of the compounds: ammonium metavanadate NH₄VO₃, nickel nitrate, iron nitrate Fe₂(NO₃)₃ or niobium oxide nanopowder Nb₂O₅, silica sol and titanium powder are added thereto and subjected to homogenization and mechanochemical activation. Obtained suspension is applied on carrier – metal wool with wire diameter of not more than 0.12 mm, and then dried and calcined at temperature 600–700 °C for 20–30 minutes. Resulting adsorbent for extracting hydrogen has porosity of 50–60% and hydrogen adsorption capacity of 102–114 kg per 1 m³ of the adsorbent, is active at temperatures of up to 1100 °C and pressure of up to 4 MPa.

EFFECT: group of inventions enables to obtain an adsorbent for extracting hydrogen from hydrogen-containing mixtures, having high adsorption capacity, high resistance to gas-dynamic loads at high temperatures and pressures.

2 cl, 4 ex

Description

The group of inventions relates to the field of producing adsorbents for extracting hydrogen from hydrogen-containing gases, which can be used for fine separation of synthesis gas, extracting hydrogen from purge and tank waste gases, and coke oven gas.

More than 90% of the world's hydrogen is produced through the process of steam methane reforming. In this process, natural gas reacts with steam at elevated temperatures to form carbon monoxide and hydrogen.

The process of adsorption concentration of hydrogen from hydrogen-containing gas mixtures (HCM) is mainly based on the technology of pressure swing adsorption (PSA) under variable pressure. The process is carried out in adsorbers, periodically switched by an automatic control system, located at different stages of the working cycle, which allows obtaining purified hydrogen with a continuous flow rate and pressure close to the initial pressure of the raw HCM.

The feedstock for the PSA units for the hydrogen production unit is hydrogen sulfide gas with a hydrogen content of about 75-80% by volume. The products of the PSA units are hydrogen with a concentration above 99.5% by volume, as well as blow-off (waste) gas, which also contains some hydrogen (10-40% by volume). However, in practice, the degree of hydrogen extraction by the PSA method does not exceed 75-80% by volume, since with an increase in the degree of extraction, the costs of the operation increase sharply.

Carbon molecular sieves (CMS) with a granule size of 1.0-1.5 mm are used as an adsorbent in PSA units. The size of the adsorbent granules has a direct effect on the kinetics of the PSA process, and its reduction allows for an increase in the productivity of VSH and the degree of _H2 extraction. However, in practice, an excessive reduction in the size of the CMS granules leads to an increase in the aerodynamic resistance of the adsorbent layer to the gas flow.

A block microporous carbon adsorbent and a method for producing it are known (RU Patent No. 2744400 for invention), in which the adsorbent is produced on the basis of peat, including processing the peat raw material until a homogeneous mass is obtained, mixing the processed raw material with a chemical activator and a binder, granulating the mixture, drying, carbonization, activation, washing off mineral impurities, processing with an alkaline solution, additionally processing the adsorbent with an acidic solution, washing with water to a pH of at least 4, crushing the resulting adsorbent granules to an average particle fraction of 600-900 μm, mixing the crushed adsorbent with a binder, molding at pressures from 200 to 500 kgf/ ^cm2 and drying at a temperature from 110 to 150°C for at least 48 hours.

The disadvantage of the known technical solution is the low adsorption rate due to the relatively large size of its granules.

Also known are carbon sorption fibers (RU Patent No. 2109562), obtained by pyrolysis of viscose fiber, including meso- and macropores, with the depth of the meso- and macroporous layer of the fiber being 1000-5000 Å with a ratio of meso- and macropores of 1:0.25-0.75, and a fiber diameter of 5-8 µm.

The disadvantages of the known invention for practical application are the high cost of the fibers used, high aerodynamic resistance to the gas flow due to the small thickness of the fibers, and a high degree of adsorbent carryover at high gas flow rates due to the low mechanical strength of the viscose fibers.

A method for producing carbon fiber used as a sorption-active material is known (Patent of the Russian Federation No. 2130516, published on 20.05.1999), in which textile fibers made of acrylonitrile copolymer are oxidized at 235-260°C for 35-60 min with an extraction of 20-30%, then at 230-260°C for 85-140 min with an extraction of -5 to +5%, carbonized in a nitrogen environment for 10 min at a temperature of 350 to 1500°C under tension. The diameter of the resulting fiber is 5-15 μm.

The disadvantages of such fibers are their high cost, high aerodynamic resistance to gas flow due to the small thickness of the fibers, and longitudinal deformation of pores, which is typical for stretch molding, leading to a lack of selectivity of hydrogen adsorption.

A method for forming solid particles of aluminum oxide clad with titanium oxide is known (RU Patent No. 2533822), in which an aqueous suspension of solid particles of aluminum oxide is mixed with an aqueous solution of titanyl sulfate, the solution is alkalized and the suspension is maintained for a certain time, after which sulfate ions are removed by washing with hot water, the precipitate is filtered off, the precipitate is resuspended by adding water, dried by spraying at 100 °C and calcined at 400-1000 °C.

The disadvantages of the known solution are obtaining an adsorbent in the form of a finely dispersed microspherical powder, effective when used in a fluidized bed, but creating significant resistance to the gas flow in a stationary adsorbent bed. In addition, the proposed adsorbent has a different purpose from the proposed one.

A carbon-based hydrogen absorber is known (RU Patent No. 2176981, published on 20.12.2001), which is made in the form of a macro-sized body. The macro-sized body contains carbon in an amount of more than 90 wt. % and has dimensions in the range of 0.1 μm - 250 mm, and the content of nanopores having a size of 0.8-3 nm is 20-60 vol. %. The macro-sized body can additionally contain transport pores of 0.05-100 μm in an amount not exceeding 50 vol. %. The absorber can contain at least one metal from the group including Pd, Pt, Ni, Ti, V, Fe, Co, Nb, Mo, Rh, Ta, W and their alloys.

The disadvantages of the known hydrogen absorber are: the complexity and high cost of its manufacture, the environmentally hazardous technology of preparing a porous carrier using chlorine at high temperature, the use of precious metals (Pd, Pt) and the low rate of hydrogen adsorption and desorption.

The problem solved by the invention is to obtain an adsorbent for extracting hydrogen from a hydrogen-containing gas, which ensures an increase in the productivity of adsorbers when extracting hydrogen in the process of separating hydrogen-containing gases under high gas-dynamic loads, as well as elevated temperatures and pressures.

The technical result, which the group of inventions is aimed at achieving, is the production of an adsorbent for extracting hydrogen from hydrogen-containing mixtures, which has a high adsorption capacity, increased resistance to gas-dynamic loads under conditions of high temperatures (up to 1000°C) and pressures (up to 4 MPa).

The specified technical result is achieved due to the fact that in the method for producing an adsorbent for extracting hydrogen from a hydrogen-containing gas, in which at the first stage a finely dispersed suspension of a catalyst for the hydrogenation-dehydrogenation process is prepared, for which purpose in a ball mill to one of the compounds of transition metals from the series: ammonium metavanadate NH ₄ VO ₃ , nickel nitrate Ni(NO ₃ ) ₂ , iron nitrate Fe ₂ (NO ₃ ) ₃ or niobium oxide nanopowder Nb ₂ O ₅ , silica sol with a concentration of 500-550 g / l SiO ₂ and titanium powder with a particle size of 0.63-1.0 mm are added, homogenization and mechanochemical activation of the resulting suspension are carried out under normal conditions for 10-20 hours with a drum rotation speed of 30-60 rpm until a particle size of no more than 20 μm is achieved, and at the second stage activated suspension on a carrier, which is metal wool with a wire diameter of no more than 0.12 mm, after which the resulting composition is dried at a temperature of 100-120 °C for 30-40 minutes and calcined at a temperature of 600-700 °C for 20-30 minutes, then the second stage is repeated 3-5 times until the thickness of the layer of suspension components applied to the carrier is formed, equal to 0.1-0.12 mm, and the activity of the finished adsorbent for extracting hydrogen from hydrogen-containing gas is achieved at a temperature of up to 1100 °C and a pressure of up to 4 MPa, a porosity of 50-60% and an adsorption capacity for hydrogen of 102-114 kg per 1 m ³ of adsorbent.

In this case, the adsorbent obtained by the above-mentioned method, active at a temperature of up to 1100°C and a pressure of up to 4 MPa, for extracting hydrogen from a hydrogen-containing gas on a carrier made of metal wool with a wire diameter of no more than 0.12 mm, has a porosity of 50-60% and an adsorption capacity for hydrogen of 102-114 kg per 1 ^m3 of adsorbent.

An adsorbent for extracting hydrogen from a hydrogen-containing gas is obtained in two stages as follows.

At the first stage, a finely dispersed suspension of the hydrogenation-dehydrogenation catalyst is prepared for impregnating the adsorbent carrier. For this purpose, silica sol with a concentration of 500-550 g/l SiO 2 and titanium powder with a particle size of 0.63-1.0 mm are added to _the hydrogenation-dehydrogenation catalyst, which is one of the transition metal compounds from the series: ammonium metavanadate NH ₄ VO ₃ , nickel nitrate Ni(NO ₃ ) ₂ , iron nitrate Fe ₂ (NO ₃ ) ₃ , niobium oxide nanopowder Nb ₂ O ₅ , and homogenization and mechanochemical activation of the initial components are carried out using a ball mill. Homogenization and mechanochemical activation are carried out for 10-20 hours with intensive mixing at a drum rotation speed of 60 rpm, until the particle size reaches no more than 20 µm.

At the second stage, the activated finely dispersed suspension of the catalyst of the hydrogenation-dehydrogenation process is applied to the carrier, which is metal wool with a wire diameter of no more than 0.12 mm. The resulting composition of the activated finely dispersed suspension of the catalyst of the hydrogenation-dehydrogenation process applied to the carrier is additionally activated by drying at a temperature of 100-120 °C for 30-40 minutes and calcining at a temperature of 600-700 °C for 20-30 minutes. The second stage is repeated 3-5 times until the thickness of the layer of the applied suspension components on the threads of metal wool equals 0.1-0.12 mm.

The resulting activated adsorbent is a carrier made of metal wool with a dense layer of metallic titanium, a hydrogenation-dehydrogenation catalyst (an oxide of a transition metal, for example, from the series Ni, Fe, V, Nb) with a total content of up to 90%, as well as silica sol with a total content of up to 10%, as a binder that firmly holds metallic titanium and a hydrogenation-dehydrogenation catalyst on the carrier.

Below are presented examples that disclose, but do not limit, the described method for producing an adsorbent for extracting hydrogen from hydrogen-containing mixtures.

Example 1. Homogenization and mechanochemical activation of the initial components are carried out using a ball mill, the drum volume of which can be 10 l, the number of balls - 50 pcs. with each ball weighing 200 g. The drum and balls can be made of stainless steel. The initial components are loaded into the drum and formed into a finely dispersed suspension. The following were used as initial components: silica sol with a volume of 4 l with a concentration of 520 g / l SiO ₂ , titanium powder of the PTN-2 brand, grain size of 0.63-1.0 mm in an amount of 1 kg, a liquid catalyst for accelerating the process of metal hydrogenation-dehydrogenation - nickel nitrate Ni (NO ₃ ) ₂ with a concentration of 200 g / l based on Ni in a volume of 0.2 l.

Homogenization and mechanochemical activation were carried out for 20 hours.

The carrier used was 20X25N20S2 stainless steel wool weighing 200 g, with a volume of 2 l and a wire diameter of 0.12 mm. The resulting adsorbent absorbs hydrogen from hydrogen-containing gas at temperatures up to 1100°C and pressures up to 4 MPa. The amount of absorbed hydrogen was 114 kg per 1 ^m3 of adsorbent.

Example 2. Differs from Example 1 in that the following were used as initial components: 4 l of silica sol with a concentration of 500 g/l SiO ₂ , titanium powder of the PTN-2 brand, with a grain size of 0.63-1.0 mm in an amount of 1 kg, a liquid catalyst for accelerating the process of metal hydrogenation-dehydrogenation - ferric nitrate Fe ₂ (NO ₃ ) ₃ with a concentration of 200 g/l by Fe in a volume of 0.2 l. Grinding and mechanochemical activation were carried out for 20 hours. Metal wool made of stainless steel grade 20X25N20S2 weighing 200 g, with a volume of 2 l, with a wire diameter of 0.12 mm was used as a carrier. The resulting adsorbent absorbs hydrogen from a hydrogen-containing gas at a temperature of up to 1100 ° C and a pressure of up to 4 MPa. The amount of absorbed hydrogen was 103.2 kg per 1 ^m3 of adsorbent.

Example 3. Differs from Example 1 in that the following were used as initial components: 4 l of silica sol with a concentration of 520 g/l SiO ₂ , titanium powder of the PTN-2 brand, with a grain size of 0.63-1.0 mm in an amount of 1 kg, a liquid catalyst for accelerating the process of metal hydrogenation-dehydrogenation - ammonium metavanadate NH ₄ VO ₃ with a concentration of 100 g/l by V, with a volume of 0.25 l. Grinding and mechanochemical activation were carried out for 20 hours. Metal wool made of stainless steel grade 20X20N14S2 weighing 300 g, with a volume of 3 l, with a wire diameter of 0.12 mm was used as a carrier. Such an adsorbent absorbs hydrogen from a hydrogen-containing gas at a temperature of up to 800 ° C and a pressure of up to 4 MPa. The amount of absorbed hydrogen was 102 kg per 1 ^m3 of adsorbent.

Example 4. Differs from Example 1 in that the following were used as initial components: 4 l of silica sol with a concentration of 550 g/l SiO ₂ , 1.5 kg of PTN-2 titanium powder with a grain size of 0.63-1.0 mm, and 0.1 kg of a solid catalyst for accelerating the metal hydrogenation-dehydrogenation process - Nb ₂ O ₅ nanopowder. Grinding and mechanochemical activation were carried out for 20 hours. The carrier was metal wool made of 20X20N14S2 stainless steel weighing 200 g, with a volume of 2 l, and a wire diameter of 0.12 mm. The resulting adsorbent absorbs hydrogen from a hydrogen-containing gas at a temperature of up to 250°C and a pressure of up to 4 MPa. The amount of absorbed hydrogen was 112.8 kg per 1 m ³ of adsorbent.

The obtained adsorbent for hydrogen extraction from hydrogen-containing gas mixtures has low gas-dynamic resistance due to high porosity of 50-60%, high adsorption capacity for hydrogen (102-114 kg of hydrogen per 1 ^m3 of adsorbent) and stability under the influence of high temperatures (up to 1100°C) and pressures (up to 4 MPa). Such indicators are achievable due to high thermodynamic stability of the adsorbent components. Thus, the declared technical result is fully achieved.

Claims (2)

1. A method for producing an adsorbent for extracting hydrogen from a hydrogen-containing gas, in which, at the first stage, a finely dispersed suspension of a catalyst for the hydrogenation-dehydrogenation process is prepared, for which purpose, in a ball mill, to one of the compounds of transition metals from the series: ammonium metavanadate NH ₄ VO ₃ , nickel nitrate Ni(NO ₃ ) ₂ , iron nitrate Fe ₂ (NO ₃ ) ₃ or niobium oxide nanopowder Nb ₂ O ₅ , silica sol with a concentration of 500-550 g/l SiO ₂ and titanium powder with a particle size of 0.63-1.0 mm are added, homogenization and mechanochemical activation of the resulting suspension are carried out under normal conditions for 10-20 hours with a drum rotation speed of 30-60 rpm until a particle size of no more than 20 μm is achieved, and at the second stage the activated suspension is applied to a carrier, as which uses metal wool with a wire diameter of no more than 0.12 mm, after which the resulting composition is dried at a temperature of 100-120 ° C for 30-40 minutes and calcined at a temperature of 600-700 ° C for 20-30 minutes, then the second stage is repeated 3-5 times until the thickness of the layer of suspension components applied to the metal wool threads is 0.1-0.12 mm, and the activity of the finished adsorbent for extracting hydrogen from hydrogen-containing gas is achieved at a temperature of up to 1100 ° C, a pressure of up to 4 MPa, a porosity of 50-60% and an adsorption capacity for hydrogen of 102-114 kg per 1 m ^{3 of} adsorbent. 2. An adsorbent for extracting hydrogen from a hydrogen-containing gas on a carrier made of metal wool with a wire diameter of no more than 0.12 mm, obtained by the method according to item 1, active at a temperature of up to 1100°C, a pressure of up to 4 MPa, having a porosity of 50-60% and an adsorption capacity for hydrogen of 102-114 kg per 1 ^m3 of adsorbent.