CN117042873A - Catalytic element with regular cellular structure for heterogeneous reactions - Google Patents

Catalytic element with regular cellular structure for heterogeneous reactions Download PDF

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Publication number
CN117042873A
CN117042873A CN202180096000.4A CN202180096000A CN117042873A CN 117042873 A CN117042873 A CN 117042873A CN 202180096000 A CN202180096000 A CN 202180096000A CN 117042873 A CN117042873 A CN 117042873A
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catalyst
ltoreq
metal
honeycomb
monolith
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阿纳托利·库兹米奇·阿布拉莫夫
阿尔乔姆·列昂尼多维奇·米泽
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Special Design and Engineering Bureau Katalizator JSC
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/04—Mixing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Thermal Sciences (AREA)
  • Catalysts (AREA)

Abstract

The invention relates to a catalytic element for heterogeneous reactions having a regular cellular structure. Catalytic elements for heterogeneous reactions involving deep oxidation of hydrocarbons and carbon monoxide are described, in the form of blocks with regular cellular structures and rectangular cellular channels made of catalytically active species comprising an active ingredient and alumina. The alumina precursor used is of formula Al obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 O wherein 0.3.ltoreq.n.ltoreq.1.5, and alumina powder, at a ratio of 20 to 80wt% of Al 2 O 3 ·nH 2 O wherein 0.3.ltoreq.n.ltoreq.1.5 and 80-20wt% of alumina powder, the channel walls having open transport pores with a size of 50-500nm, said open transport poresThe pores account for 35-70% of the total pore volume and the active ingredient comprises a metal or a compound of metals selected from the group of manganese, chromium, copper, iron or mixtures thereof. The object of the present invention is to develop catalytic elements in the form of blocks with a regular cellular structure, which exhibit high thermal stability and mechanical strength, while also having high activity.

Description

Catalytic element with regular cellular structure for heterogeneous reactions
Technical Field
The present invention relates to catalysts having a regular cellular structure for heterogeneous reactions, for example, processes for the treatment of enterprise exhaust gases, the selective reduction of nitrogen oxides and oxygen, ozone destruction, the fixed bed catalytic dehydrogenation of lower alkanes, alkenes, arylalkanes to produce the corresponding alkenes, alkadienes, arylalkenes.
Background
The operating conditions of the catalyst are characterized by very high temperatures and mechanical loading, excessive exposure to gas streams. For example, the reduction of the temperature of the industrial waste gas by post combustion ranges from 400 to 1000 ℃, which determines the requirement for high thermal stability of the catalyst. The operating environment of the catalyst also involves high mechanical loads and excessive exposure to gas streams. Thus, catalyst performance and lifetime depend on its ability to maintain its strength, phase composition uniformity, and high activity over long term severe operation. If a bulk catalyst in the form of spherical or cylindrical pellets is used under such conditions, high bed resistance, uneven temperature distribution across the reactor cross-section and enhanced particle attrition are typically noted.
For the purpose of eliminating said drawbacks, it is possible to use a monolithic (honeycomb) catalyst in which a support is used as a solid monolith. Typically, the monolith has a large number of parallel, non-intersecting channels and is made of silicate ceramic material. The channel surfaces are coated with an active component.
The honeycomb catalyst should have high mechanical strength, thermal stability and good flow rates at the various layers of the channel walls, and have a sufficiently high channel density that reagents can enter the interior channel walls to increase the active surface area and correspondingly the activity of the honeycomb monolith catalyst.
The honeycomb monolith catalyst may be composed of the active component mixed with a binder (so-called integral monolith) or may be presented as a support coated with the active component. In terms of the distribution of the active component, there are catalysts in which the active component is located on the outer surface of the monolith, or is uniformly distributed over the wall depth (rp. Avila, m. Montes, E.E.Miro, chem.Eng.Journal (2005), 11-36).
There are known methods for producing honeycomb catalysts for heterogeneous catalytic reaction systems (RU 2724261,IPC B01D 53/94; B01D 53/56; B01D 53/58; B01J 29/064; B01J29/068; B01J 29/072; B01J 29/076; B01J 29/46; B01J 29/56; B01J 29/72, disclosed in month 22 of 2020), wherein the active component is applied to a support (inert support) or the active component (catalyst) is mixed with other components to produce a catalyst for the selective catalytic reduction of nitrogen oxides (SCR).
According to a second variant, the catalyst is mixed with other components such as fillers, binders and reinforcing agents to obtain an extrudable paste which is further extruded through a die to form a honeycomb monolith.
The development of a more durable coating for honeycomb supports is one of the current trends, but its production technology is complex, which limits the wide application of honeycomb catalysts in different heterogeneous high temperature reactions.
There are known catalysts for ozone destruction processes (patent KR 900003136,IPC B01D53/34; B01J 23/34; B01J 37/00, disclosed in 1989, month 09, 18), which comprise a support having a honeycomb structure; preparation of SiO 2 (30％)、Al 2 O 3 (35%), caO (3%), mgO (1%), monazite (5%), tiO 2 (25.5%) and Ag (0.5%) and calcined at 150-250 ℃ for forming the ceramic support. The obtained carrier is doped with MnO 2 。
To support the active component, a cordierite honeycomb monolith may be used.
There are known catalysts for the removal of organic compounds (patent U.S. Pat. No. 3,262,IPC B01D 53/86; B01J 23/42; B0U 23/44, disclosed in 2020, 25/06). The catalyst comprises cordierite honeycomb ceramic and uses a mixture of platinum and palladium as an active component; the amount of the mixture of platinum and palladium ranges from 0.01% to 0.05% of the mass of the substrate; the amount of carrier ranges from 3% to 5% of the mass of the matrix.
The disadvantage is the use of noble metals, which limits their application and in some cases is cost-effective.
There are known catalysts for the removal of Volatile Organic Compounds (VOCs) (patent CN110404550, IPC B01D 53/44; B01D 53/86; B01J 23/83, disclosed in 2019, 11, 05). The catalyst for removing volatile organic compounds comprises a support and a coating material applied to the support, wherein the support is a monolith support having cordierite honeycombs, and the coating material comprises a composite Co/Ce-Zr-M oxide, wherein M is one or more of La, nd, pr and Y. The catalyst does not include expensive precious metal components.
The main disadvantage of the above analogues is their low thermal stability, leading to cracking and flaking of the active catalytic layer from the support, which in turn leads to plugging of the honeycomb channels, and if dust-laden gases are handled, these processes are accelerated several times due to erosion.
The closest technical solution in terms of structure and monolith shape to the claimed technical solution is a catalyst with a regular honeycomb structure for heterogeneous high temperature reactions (patent RU 2209117,IPC B01J 35/04; B01J 23/745; B01J 23/26; B01J 21/04; C01B 21/26, disclosed in month 27 of 2003), manufactured as a separate monolith with a square cross section with sides of 65 to 73mm, as a 25 to 50mm high monolith. A regular honeycomb structure with channel dimensions of 4x4 mm, 5x 5mm is arranged in the monolith, with walls of 0.8 to 1.5mm thickness.
The closest technical solution to the claimed technical solution in the method for producing the claimed catalyst with a regular honeycomb structure is a method for producing a honeycomb monolith as a parallelepiped or hexagonal prism comprising iron, aluminum oxide and a promoter (patent RU 2207904,IPC B01J 23/84; b01j 21/04; c01 b 21/26, disclosed in 07 th month 10 2003). As cocatalyst, the catalyst comprises at least one compound of an element from the group: co (Co)Mn, cr, V, mo, sn, bi or mixtures thereof and is Al 2 O 3 ·nH 2 The precursor of alumina of aluminum compound of O, wherein n is more than or equal to 0.3 and less than or equal to 1.5, has lamellar X-ray amorphous structure. The precursor of alumina may comprise at least one compound of an element from the group: si, mg, c a in an amount not exceeding 1.0wt.% expressed as oxide. The catalyst obtained has the following composition, in wt.%: fe (Fe) 2 O 3 65 to 86, promoters as oxides-0.1 to 15, the remainder being Al 2 O 3 . The honeycomb catalyst further comprises titanium oxide in an amount of no more than 5 wt.%.
Patent RU 2207904 proposes a method for producing honeycomb monoliths from catalytically active substances.
For the production of monoliths, based on formula Al 2 O 3 ·nH 2 X-ray amorphous compound of O (wherein n is 0.3.ltoreq.n.ltoreq.1.5) prepares a mixture of the active ingredient and peptized aluminum hydroxide. From the paste obtained, a monolith is produced by extrusion through a die (mold) as a parallelepiped or hexagonal prism. The honeycomb monolith was air-dried at room temperature for 6 days and dried in a flow dryer, and air heated to 350 ℃ flowed through the honeycomb channels. Once dried, the catalyst monolith was calcined at 950 ℃.
According to these solutions, the honeycomb structure of the proposed catalyst has geometrical components: channels and channel walls.
In long channels with a small channel cross section there is always the risk of clogging the channel with reagents and reaction products or soot. The flow within the channels is different along the channel axis and in the wall layers, there is no filtration through the channel walls, which ultimately reduces the accessibility of active sites on the channel walls and reduces the activity and lifetime of the catalyst.
In extruded catalysts having a honeycomb structure, wherein the working mixture to be shaped is a catalytically active mixture, the active component is distributed over the entire volume of the catalyst as a monolithic block having a regular honeycomb structure with honeycomb channels.
However, modification of the composition of the working mixture and the catalytically active component results in difficult shaping or in cracking of the monolith, which makes the development of improved catalysts with honeycomb structures cost intensive and expensive, even for one process, especially for different chemical processes.
Disclosure of Invention
The object of the present invention is to develop catalysts from catalytically active substances for heterogeneous reactions as honeycomb monoliths which exhibit high thermal stability, mechanical strength and maintain high activity, and to develop a simple process for producing them which allows a significant expansion of the use of honeycomb monolithic catalysts in different chemical processes.
This problem is solved by using a catalyst for heterogeneous reactions, including the deep oxidation of hydrocarbons and carbon monoxide, made of catalytically active species comprising an active component, alumina, into honeycomb monoliths with rectangular honeycomb channels. As precursor of alumina, use is made of the formula Al obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 Mixtures of aluminum compounds and aluminum oxide powders of O (where 0.3.ltoreq.n.ltoreq.1.5), in a ratio of 20 to 80wt.% of Al 2 O 3 ·nH 2 O (wherein 0.3.ltoreq.n.ltoreq.1.5) and 80 to 20wt.% of alumina powder, wherein the channel walls have open transport pores with a size of 50 to 500nm, said open transport pores accounting for 35 to 70% of the total pore volume, and said active component comprises a metal or a compound of metals selected from the group of manganese, chromium, copper, iron or mixtures thereof.
Preferably, the particle size of the active component is no greater than 20 to 50nm.
Preferably, the sides of the rectangular monolith substrate are 20 to 150mm in height 30 to 1470mm, the channel walls are 0.1 to 2mm thick, the channel sides are 0.1 to 19.9mm in size, and the number of channels per square inch of the monolith cross-section is 1.5 to 250cpsi.
Preferably, the honeycomb monolith is shaped as a right hexagonal prism or a right rectangular prism, and the inner walls of all honeycomb channels have the same thickness.
Preferably, grooves are made in the outside of the honeycomb monolith, said grooves having a depth equal to 1/2 of the sides of the honeycomb channels.
Preferably, the catalyst comprises a metal or a metal compound selected from the group consisting of metal oxides, metal hydroxides, metal carbonates, metal hydroxycarbonates, or mixtures thereof.
Preferably, the metal or the metal compound comprises one or more metals selected from Na, K, ba, al, si, V, co, ni, zn, mo, ag, sn, la and Ce.
Preferably, the catalyst comprises titanium dioxide, zirconium dioxide, a metal aluminate or mixtures thereof.
Preferably, the catalyst has a specific surface area of 1 to 100m 2 Per gram, bulk density of 0.4 to 1.4g/cm 3 The mechanical strength is not less than 6.0MPa, and the liquid flow resistance of the bed layer is not more than 280Pa/m at a flow rate of 0.5 m/s.
This problem is also solved by a process for producing the above-described catalyst for heterogeneous reactions comprising deep oxidation of hydrocarbons and carbon monoxide, said process comprising the steps of: a powder material is prepared from the components of the catalytically active material, which is mixed with a binder based on an aluminum compound, plasticizing additives, pore structuring additives including combustible pore structuring additives to obtain the catalytically active material, shaped by extrusion through a die to produce a shaped element as a honeycomb monolith having rectangular honeycomb channels, air-dried, dried and calcined. For shaping, use is made of the formula Al obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 O A mixture of a binder of an aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 and an alumina powder, the ratio of which is 20 to 80wt.% of Al of formula 2 O 3 ·nH 2 O wherein 0.3.ltoreq.n.ltoreq.1.5 and 80 to 20wt.% of alumina powder, wherein the channel walls have open transport pores with a size of 50 to 500nm, said open transport pores accounting for 35 to 70% of the total pore volume, said mixture being initially activated by combined grinding or grinding alone, with a component comprising a catalytically active species of a metal or a compound of a metal selected from the group of manganese, chromium, copper, iron or a mixture thereof,The plasticizing additive and the pore structuring additive are mixed, the resulting catalytically active material is plasticized, shaped, air-dried, then dried at a temperature which increases gradually from 40 to 120 ℃ and calcined at a temperature of 300 to 1200 ℃ for 1 to 16 hours.
Preferably, the formula Al 2 O 3 ·nH 2 The aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 of O has an average particle size of 30 μm after activation by grinding.
Preferably, pyrolusite and/or pyrolusite, which are preliminarily ground in a grinder to a particle size of not more than 40 μm, are used as the manganese compound.
Preferably, polyvinyl alcohol or isopropanol, polyethylene glycol, cellulose, starch, urotropin (urotropin), sawdust, stearic acid and/or commercially available derivatives thereof or mixtures thereof are used as plasticizing additives in an amount of 0.1 to 15.6 wt.%.
Preferably, nitric acid having an acid modulus (acid modulus) of 0.10 to 0.30 is used for plasticizing the catalyst working mixture.
Preferably, the shaped monolith is air dried at a temperature of 18 to 20 ℃ and a relative humidity of 20 to 90% for 7 to 14 days.
Preferably, the monolith is dried at a relative humidity of 20 to 90% for 7 to 21 days.
Preferably, the calcination is carried out at a temperature of 350 to 500 ℃ for 2 to 8 hours.
Preferably, the low temperature calcination is performed at a temperature of 400 to 600 ℃ for not less than 1 to 6 hours, and then the high temperature calcination is performed at a temperature of 900 to 980 ℃ for not less than 1 to 6 hours, optionally followed by raising the temperature to 1200 ℃.
Preferably, the strength is not lower than 4.0MPa after 100 to 200 heating cycles from room temperature to 800 ℃ in air and cooling to room temperature in a muffle furnace.
This problem is also solved by a catalytic process comprising the deep oxidation of hydrocarbons and carbon monoxide using the above-mentioned catalyst produced by the above-mentioned method, said catalytic process comprising the step of contacting the reaction mixture with said catalyst under catalytic reaction conditions.
The proposed catalysts for heterogeneous reactions have the following substantial differences from the known solutions:
as precursor of alumina, use is made of the formula Al obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 Mixtures of aluminum compounds and aluminum oxide powders of O (where 0.3.ltoreq.n.ltoreq.1.5), in a ratio of 20 to 80wt.% of Al 2 O 3 ·nH 2 O (wherein 0.3.ltoreq.n.ltoreq.1.5) and 80 to 20wt.% alumina powder;
the channel walls have open transport pores with a size of 50 to 500nm, which account for not less than 35% of the total pore volume.
The set of features proposed allows the production of catalysts for heterogeneous reactions from catalytically active substances as honeycomb monoliths with rectangular honeycomb channels, with high thermal stability and mechanical strength and maintaining high activity.
The technical result of the proposed solution is to develop a catalyst for heterogeneous reactions as a honeycomb monolith with high thermal stability, mechanical strength and maintaining high activity from the catalytically active material, and to develop a simple method of producing it that allows to significantly expand the use of honeycomb monolith catalysts in different chemical processes.
In this case, the problem of using catalysts in high productivity plants and dusty mixtures is solved, and the high ratio of contact surface to element volume allows for efficient heterogeneous reactions at low (100 to 1500 ppm) and very low (< 100 ppm) reagent concentrations.
The proposed method for producing the catalyst as a honeycomb monolith is as follows:
formula Al as catalyst for preparing 2 O 3 ·nH 2 Aluminum compound of O, using Al 2 O 3 ·nH 2 O (wherein 0.3.ltoreq.n.ltoreq.1.5). Compound Al 2 O 3 ·nH 2 O, where 0.3.ltoreq.n.ltoreq.1.5, is obtainable by any known method by rapid partial dehydration of gibbsite, for example according to patent RU 2064435 (IPC C01F 7/44, disclosed in 1996, 27) or according to the expertRU 2148017 (IPC C01F 7/44, disclosed in month 27 of 2000).
Compound Al of lamellar X-ray amorphous structure 2 O 3 ·nH 2 O, wherein 0.3.ltoreq.n.ltoreq.1.5, means a compound whose X-ray analysis does not detect any characteristic line of the crystalline phase. The compound has an increased reactivity, which allows the compound of the catalyst component to be inserted into the interlayer space between the aluminum hydroxide packs with sliding of the aluminum hydroxide packs relative to each other.
During the production of the catalyst, the amorphous structure of formula Al in layered X-rays as the temperature increases to 350 to 1200 DEG C 2 O 3 ·nH 2 An aluminum compound of O, wherein 0.3.ltoreq.n.ltoreq.1.5, forms an active phase in the presence of a compound of the following metals: na, K, ba, al, si, V, cr, mn, fe, C, ni, cu, zn, mo, ag, sn, la and C. At the same time, al 2 O 3 ·nH 2 The lamellar X-ray amorphous structure of the aluminum compound of O, wherein 0.3.ltoreq.n.ltoreq.1.5, contributes to the generation of highly dispersed active components, and increases the mechanical strength of the catalyst due to the stronger bonding of the active component particles to the alumina surface.
Al of the formula 2 O 3 ·nH 2 The binder of O (hereinafter referred to as heat activated alumina, TAA) and alumina powder are initially activated by grinding (disintegrating) in combination or separately to a specific particle size, possibly of formula Al 2 O 3 ·nH 2 The aluminum compound of O, wherein 0.3.ltoreq.n.ltoreq.1.5, has an average particle size of 30 μm after activation by grinding.
Different phases may be used: gamma-Al 2 O 3 、χ-Al 2 O 3 、α-Al 2 O 3 As alumina powders, they are also ground to a specific particle size in a pulverizer.
Polyvinyl alcohol or isopropanol, polyethylene glycol, cellulose, starch, urotropine, sawdust, stearic acid and/or commercially available derivatives thereof or mixtures thereof in an amount of 0.1 to 15.6wt.% are used as plasticizing additives.
Nitric acid having an acid modulus of 0.10 to 0.30 is used for plasticizing the catalyst working mixture.
In order to plasticize the catalytically active material, water may be added, and other acids may be used in addition to nitric acid.
The prepared catalytically active material (working mixture) was shaped by extrusion through a die to produce a shaped element as a honeycomb monolith having rectangular honeycomb channels, the monolith having the following dimensions: the sides of the rectangular block matrix are 20 to 150mm in height 30 to 1470mm, the channel walls are 0.1 to 2mm thick, the channel sides are 0.1 to 19.9mm in size, and the number of channels per square inch of the monolithic cross section is 1.5 to 250cpsi.
The honeycomb monolith has the shape of a right hexagonal prism (fig. 2) or a right rectangular prism.
Grooves are made on the outside of the honeycomb monolith, the grooves having a depth equal to 1/2 of the sides of the honeycomb channels. The grooves form additional channels when the monolith is stacked in layers (fig. 3).
The catalyst may comprise a metal or a compound of a metal selected from the group consisting of metal oxides, metal hydroxides, metal carbonates, metal hydroxycarbonates or mixtures thereof as an active component.
Depending on the catalytic process, the at least one metal or compound of metals is selected from the group of Na, K, ba, al, si, V, co, ni, zn, mo, ag, sn, la and Ce.
The catalyst may comprise titania, zirconia, metal aluminates or mixtures thereof.
For ozone destruction, the catalyst may include an oxide of at least one metal selected from the group consisting of copper, manganese, cobalt and nickel as an active component.
For the selective catalytic reduction of nitrogen oxides, the catalyst may include oxides of vanadium, cerium and manganese as active components.
The shaped pieces were possibly air-dried for 7 to 14 days under the following conditions: at a temperature of 18 to 20 ℃ and a relative humidity of 20 to 90%.
The monolith is then dried at a temperature of 40 to 120 ℃ and a relative humidity of 20 to 90% for 7 to 21 days and then calcined, including low temperature calcination which may be carried out at a temperature of 350 to 500 ℃ for 2 to 8 hours.
Possibly, the low temperature calcination is not less than 1 to 6 hours at a temperature of 400 to 600 ℃, followed by the high temperature calcination at a temperature of 900 to 980 ℃ for not less than 1 to 6 hours, optionally followed by an increase in temperature to 1200 ℃.
The calcination temperature depends on the metal compound:
cu-400 to 600 ℃;
mn-400 to 1000 ℃;
cr-400 to 700 ℃;
fe-400 to 850 ℃.
The temperature is gradually increased at a rate of 1 to 5 ℃ per minute.
The high temperature calcination may be performed as follows: at a temperature of 900 to 980 ℃ for not less than 1 to 6 hours, optionally followed by increasing the temperature to 1200 ℃.
The catalyst obtained after calcination has a specific surface area of 1 to 100m 2 Per gram, bulk density of 0.4 to 1.4g/cm 3 The mechanical strength is not less than 6.0MPa, the liquid flow resistance of the bed layer at the flow rate of 0.5m/s is not more than 280Pa/m, the strength is not less than 4.0MPa after 100 to 200 heating cycles from room temperature to 800 ℃ and cooling to room temperature in a muffle furnace, and the granularity of the active component is not more than 20 to 50nm.
The proposed solution allows the development of catalysts that are made in honeycomb monoliths, providing an optimal combination of strength in high-velocity gas streams with minimal flow resistance of the catalyst bed, ensuring high performance and economic cost reduction of the final e.g. gas treatment.
Preferred embodiments of the invention
The process described below for preparing catalysts for the deep oxidation of organic compounds comprises the preparation steps which are also used for producing catalysts for other heterogeneous reactions, such as ozone destruction, selective catalytic reduction of ethylbenzene dehydrogenation to styrene, nitrogen oxides, selective partial oxidation of organic compounds.
The strength was measured using an instrument MP-9S for measuring mechanical strength.
Model for deep oxidation of butaneThe catalytic activity of the samples prepared according to examples 1 to 5 was determined by flow cycling in the reactor. The butane concentration in the reaction mixture was 0.2vol.% and the catalyst sample weight was 1±0.2g. The butane oxidation reaction rate (cm) at a temperature of 400.+ -. 2 ℃ at 60% butane conversion was used 3 /g.s) as activity measure.
The composition and physical and chemical characteristics of the resulting catalyst were determined as follows:
the catalyst density is determined by dividing the mass of the monolithic catalyst by the geometric volume.
The content of the components in the catalyst samples was determined by X-ray fluorescence using a "Spectroscan MAX-GV" instrument.
The specific surface area of the sample was determined by argon thermal desorption using a gasometer GKh-1.
The flow resistance of the catalyst pellet bed was measured on a pressure drop test bed in a catalyst fixed bed.
The porous structure of the prepared sample was studied by mercury porosimetry using a mercury porosimeter Autopore 9500.
The examples provided below disclose the proposed solution.
Example 1
A catalyst for the deep oxidation of organic compounds was prepared as a honeycomb monolith having rectangular honeycomb channels.
The catalytically active material (working mixture) is prepared by mixing the required amounts of binder aluminium hydroxide powder, aluminium oxide powder, manganese (IV) oxide powder and organic additives, for example sawdust, in a rotor mixer for 10 to 120min and then in a Z-bladed mixer for 5 to 45 min.
As aluminium hydroxide, use is made of the rapid partial dehydration product of gibbsite, of the formula Al 2 O 3 ·nH 2 O, where n=0.9 (TAA), comprising not less than 40wt.% of shaped boehmite, which is ground and has an average particle size of 30 μm and a specific surface area of about 250m 2 Per gram, loss On Drying (LOD) of not more than 18%, loss On Ignition (LOI) 800 ) 28 to 32%.
As alumina, pre-calcined highly dispersed gamma-Al was used 2 O 3 (40 μm fraction weight content is not less than 60%).
The amount of TAA was 80wt.%, al 2 O 3 The amount of powder was 20%.
As manganese dioxide, pyrolusite (the weight content of the main component is not less than 90%) is used, which is preliminarily ground in a grinder to a particle size of not more than 240 μm, preferably not more than 100 μm.
For plasticization, nitric acid (acid modulus of 0.15 to 0.20) is added to the prepared catalytically active material (working mixture) in the mixer, and the obtained material is mixed for 30 to 40min to form a uniform paste. The preparation state of the material to be molded is determined visually. If a high viscosity material is obtained, a small amount of water is added, and if a low viscosity material is obtained, alumina powder is added.
Polyvinyl alcohol, polyethylene glycol, cellulose, starch, sawdust, stearic acid and/or commercially available derivatives thereof or mixtures thereof may be used as plasticizing additives in an amount of 0.1 to 15.6 wt.%.
The shaping is carried out on a screw or ram press with a string cutter. When formed, the paste is pressed through a die to form an extrudate having the desired cross-sectional geometry (fig. 2). The extrudate is cut into pieces of equal length with a cutter. The length of the shaped workpiece is 10 to 250mm. The obtained workpiece has a parallelepiped (rectangular prism) shape.
The resulting workpieces were air dried at a temperature of 18 to 20 ℃ and a humidity of 20 to 50% for 1 to 16 days.
After air drying, the honeycomb catalyst was dried in a chamber dryer at a temperature of 20 to 120 ℃ and a humidity of 20 to 90% for 60 to 400 hours.
In the step of drying the pellets, free water is removed:
AlO(OH)·xH 2 O→AlO(OH)+xH 2 O
AlO(OH) 1-y (NO 3 ) y ·xH 2 O→AlO(OH) 1-y (NO 3 ) y +xH 2 O。
the dried extrudate is calcined in two steps.
The low temperature calcination is carried out in a belt kiln with a catalyst loading of no more than 25% of the total kiln volume. As the belt moves, the product is delivered to a calcination zone where calcination is performed at a temperature of 630 to 650 ℃ for no less than 4 hours.
The following process occurs during the low temperature calcination of the honeycomb catalyst:
removal of structural water and dehydration of aluminium hydroxide and formation of alumina
2AlO(OH)→γ-Al 2 O 3 +Н 2 О；
Basic aluminum nitrate decomposition to form alumina, nitrogen dioxide and water
2AlO(OH) 1-y (NO 3 ) y →А1 2 О 3 +yNO 2 +(1-y)Н 2 О；
Combustion of combustible additives (sawdust) and plasticizers
С+О 2 →СО 2 ；
Interaction of formed nitrogen dioxide with sawdust carbon
NO 2 +C→CO 2 +1/2N 2 ；
Conversion of manganese dioxide
4MnO 2 →2Mn 2 O 3 +О 2 。
The high temperature calcination of the honeycomb catalyst is carried out in a belt kiln or an intermittent kiln. The product is placed in a calcination zone where calcination is carried out at a temperature of 900-980 ℃ for not less than 4 hours.
Further conversion of manganese (III) oxide occurs during the high temperature calcination of the honeycomb catalyst:
6Mn 2 O 3 →4Mn 3 O 4 +О 2 。
the characteristics of the honeycomb catalyst are characterized by the values shown in the rows of table 1.
The honeycomb catalyst included 4.5wt.% of m n 2 O 3 。
The monolith had the shape of a rectangular prism with a channel size of 3.1mm, a channel wall thickness of 0.9mm, S Specific surface area ＝15m 2 /g; total pore volume of 0.3cm 3 And/g, the transport pores account for 41% of the total pore volume.
Example 2
A catalyst was prepared in a similar manner to example 1, except that the catalyst was composed, the monolith had the shape of a rectangular prism, the substrate side was 150mm, the height was 300mm, the wall thickness was 0.9mm, the channel side dimension was 1.6mm, S Specific surface area ＝18m 2 /g; total pore volume of 0.37cm 3 And/g, the transport pores account for 50% of the total pore volume. TAA with n=0.3 was used.
Example 3
A catalyst was prepared in a similar manner to example 1, using ramsdellite as manganese dioxide, except for the catalyst composition and monolith shape.
The monolith had the shape of a hexagonal prism with a channel size of 1.6mm, a channel wall thickness of 0.5mm, S Specific surface area ＝20m 2 Per gram, total pore volume of 0.33cm 3 And/g, the transport pores account for 37% of the total pore volume. TAA with n=1.5 was used.
Example 4
A catalyst was prepared in a similar manner to example 1, using ramsdellite as manganese dioxide, except for the catalyst composition and monolith shape.
The monolith had the shape of a hexagonal prism with a channel size of 1.6mm, a channel wall thickness of 0.5mm, S Specific surface area ＝45m 2 Per gram, total pore volume of 0.31cm 3 And/g, the transport pores occupy 70% of the total pore volume (FIG. 1).
Example 5A. A catalyst for low temperature oxidation of VOCs was prepared.
The working mixture is prepared by mixing the required amounts of binder, aluminum hydroxide powder, copper (II) oxide powder and organic additives (e.g. sawdust) in a rotor mixer for 10 to 120min, then in a Z-bladed mixer for 5 to 45 min.
As the aluminum hydroxide, use was made ofA rapid partial dehydration product (TAA) of gibbsite, wherein n=0.9, comprising no less than 40wt.% of profiled boehmite, having an average particle size of 30 μm and a specific surface area of about 250m 2 Per gram, loss On Drying (LOD) of not more than 18%, loss On Ignition (LOI) 800 ) 28 to 32%.
As copper oxide, calcined basic copper hydroxide (the weight fraction of the main component is not less than 98%) is used, and ground in a grinder to a particle size of not more than 120 μm, preferably not more than 50 μm.
For plasticization, nitric acid (acid modulus of 0.15 to 0.20) is added to the prepared catalytically active material (working mixture) in the mixer, and the obtained material is mixed for 30 to 40min to form a uniform paste. The preparation state of the material to be molded is determined visually. If a high viscosity material is obtained, a small amount of water is added, and if a low viscosity material is obtained, alumina powder is added.
As alumina, pre-calcined highly dispersed gamma-Al was used 2 O 3 (40 μm fraction weight content is not less than 60%).
The amount of TAA was 20wt.%, γ -Al 2 O 3 The amount of powder was 80%.
Polyvinyl alcohol, polyethylene glycol, cellulose, starch, sawdust, stearic acid and/or commercially available derivatives thereof or mixtures thereof may be used as organic additives in an amount of 0.1 to 15.6 wt.%.
The shaping is carried out on a screw or ram press with a string cutter. When formed, the paste is pressed through a die to form an extrudate having the desired cross-sectional geometry. The extrudate is cut into pieces of equal length with a cutter. The length of the shaped workpiece is 10 to 250mm. The obtained workpiece has a parallelepiped shape.
The resulting shaped monolithic piece was air dried at a temperature of 18 to 20 ℃ and a humidity of 20 to 50% for 1 to 16 days.
After air drying, the molded monolith is dried in a chamber dryer at a temperature of 20 to 120 ℃ and a humidity of 20 to 90% for 60 to 400 hours.
In the step of drying the pellets, free water is removed:
AlO(OH)·xH 2 O→AlO(OH)+xH 2 O
AlO(OH) 1-y (NO 3 ) y ·xH 2 O→AlO(OH) 1-y (NO 3 ) y +xH 2 O。
the dried shaped monolith is calcined in a belt kiln with a catalyst loading of no more than 75% of the total kiln volume. As the belt moves, the product is delivered to a calcination zone where calcination is performed at a temperature of 430 to 650 ℃ for no less than 4 hours.
The following process occurs during calcination of the dried formed monolith:
removal of structural water and dehydration of aluminium hydroxide and formation of alumina
2AlO(OH)→γ-AL 2 O 3 +Н 2 О；
Basic aluminum nitrate decomposition to form alumina, nitrogen dioxide and water
2AlO(OH) 1-y (NO 3 ) y →А1 2 О 3 +yNO 2 +(1-y)Н 2 О；
Combustion of combustible additives (sawdust) and plasticizers
С+О 2 →СО 2 ；
Interaction of formed nitrogen dioxide with sawdust carbon
NO 2 +C→CO 2 +1/2N 2 ；
The monolith had the shape of a rectangular prism with 100mm base side, 100mm height, channel size of 1.8mm, wall thickness of 0.9mm, S Specific surface area ＝126m 2 /g; total pore volume of 0.48cm 3 And/g, the transport pores account for 51% of the total pore volume.
Example 5B
A catalyst was prepared in a similar manner to example 5A, the only difference being the catalyst composition, the nitric acid solution and CrO being added to the ready catalytically active material (working mixture) in the mixer for plasticization 3 。
As shown by the examples provided, the catalyst is preferably present as a honeycomb monolith having a particle size of greater than 1m 2 The specific surface area per g, depending on the calcination temperature, has high strength, thermal stability and high activity.
According to the proposed solution, for the production of catalysts for different heterogeneous reactions as honeycomb monoliths, a method for producing the catalyst is proposed which allows to obtain open transport pores with dimensions ranging from 50 to 500nm, which represent not less than 35% of the total pore volume.
It is known that the high pressures required to extrude monoliths with high channel densities result in increased material density in the channel wall skins. As a result of the high temperature treatment, the surface layer of the wall is sintered while forming a molten shell having a low specific surface area. Such a gas impermeable shell limits the access of reagents to the monolithic inner layer and thus greatly reduces the active surface.
The proposed solution will be to obtain formula Al by rapid partial dehydration of gibbsite in a specific ratio 2 O 3 ·nH 2 The use of a mixture of an aluminum compound (TAA) of O (where 0.3.ltoreq.n.ltoreq.1.5) and an alumina powder as a precursor for alumina allows solving the problem, maintaining a high flow rate of the reagent in the inner walls of the honeycomb catalyst, and thereby increasing heat and mass transfer.
Industrial applicability
The proposed catalyst can be used for the treatment of waste gases of enterprises, the selective reduction of nitrogen oxides and oxygen, ozone destruction, the fixed bed catalytic dehydrogenation of lower alkanes, alkenes, arylalkanes to produce the corresponding alkenes, alkadienes, arylalkenes.
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Claims (20)

1. Be used for packageCatalyst for heterogeneous reactions involving the deep oxidation of hydrocarbons and carbon monoxide, produced from catalytically active substances comprising active components, alumina, into honeycomb monoliths with rectangular honeycomb channels, characterized in that Al of the formula is used, obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 O A mixture of an aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 and an alumina powder as a precursor of alumina, the ratio of Al being 20 to 80wt.% 2 O 3 ·nH 2 O wherein 0.3.ltoreq.n.ltoreq.1.5 and 80 to 20wt.% of alumina powder, wherein the channel walls have open transport pores with a size of 50 to 500nm, said open transport pores accounting for 35 to 70% of the total pore volume, and said active component comprises a metal or metal compound selected from the group of manganese, chromium, copper and iron or mixtures thereof.
2. The catalyst of claim 1, wherein the particle size of the active component is no greater than 20 to 50nm and the active component comprises metal or metal compound in an amount of 2 to 30wt.% as metal oxide.
3. The catalyst of claim 1 wherein the rectangular monolith substrate has sides of 20 to 150mm, a height of 30 to 1470mm, a channel wall thickness of 0.1 to 2mm, channel sides of 0.1 to 19.9mm, and a number of channels per square inch of the monolith cross-section of 1.5 to 250cpsi.
4. The catalyst of claim 1 wherein the honeycomb monolith is shaped as a right hexagonal prism or a right rectangular prism, and the inner walls of all honeycomb channels have the same thickness.
5. The catalyst of claim 1 wherein grooves are made in the outside of the honeycomb monolith having a depth equal to 1/2 of the sides of the honeycomb channels.
6. The catalyst of claim 1, wherein the catalyst comprises a metal or a metal compound selected from the group consisting of a metal oxide, a metal hydroxide, a metal carbonate, a metal hydroxycarbonate, or a mixture thereof.
7. The catalyst of claim 6, wherein the metal or the metal compound comprises one or more metals selected from Na, K, ba, al, si, V, co, ni, zn, mo, ag, sn, la and Ce.
8. The catalyst of claim 7, wherein the catalyst comprises titanium dioxide, zirconium dioxide, a metal aluminate, or a mixture thereof.
9. The catalyst according to any one of claims 1 to 8, characterized in that the catalyst has a specific surface area of 1 to 100m 2 Per gram, bulk density of 0.4 to 1.4g/cm 3 The mechanical strength is not less than 6.0MPa, and the liquid flow resistance of the bed layer is not more than 280Pa/m at a flow rate of 0.5 m/s.
10. A method of producing a catalyst according to any one of claims 1 to 9 for heterogeneous reactions comprising deep oxidation of hydrocarbons and carbon monoxide, the method comprising the steps of:
preparation of a powder material from the components of a catalytically active substance, mixing it with a binder based on an aluminum compound, a plasticizer, a pore structuring additive comprising a combustible pore structuring additive to obtain the catalytically active substance, shaping by extrusion through a die to produce a shaped element as a honeycomb monolith with rectangular honeycomb channels, air drying, drying and calcining, characterized in that for shaping, use is made of a material of the formula Al obtained by rapid partial dehydration of gibbsite 2 O 3 ·nH 2 O A mixture of a binder of an aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 and an alumina powder, the ratio of which is 20 to 80wt.% of Al of formula 2 O 3 ·nH 2 O an aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 and 80 to 20wt.% of alumina powder, wherein the channel walls have a sizeAn open transport pore of 50 to 500nm, which occupies 35 to 70% of the total pore volume, the mixture being preliminarily activated by combined grinding or separate grinding, being mixed with a component of a catalytically active material comprising a metal or a compound of a metal selected from the group consisting of manganese, chromium, copper, iron or a mixture thereof, a plasticizing additive and a pore structuring additive, the obtained catalytically active material being plasticized, shaped, air-dried, then dried at a temperature gradually increasing from 40 to 120 ℃ and calcined at a temperature of 300 to 1200 ℃ for 1 to 16 hours.
11. The method of claim 10, wherein the formula Al 2 O 3 ·nH 2 The aluminum compound in which 0.3.ltoreq.n.ltoreq.1.5 of O has an average particle size of 30 μm after activation by grinding.
12. The method according to claim 10, wherein pyrolusite and/or pyrolusite, which are preliminarily ground in a grinder to a particle size of not more than 40 μm, are used as the manganese compound.
13. The method according to claim 10, characterized in that polyvinyl alcohol or isopropanol, polyethylene glycol, cellulose, starch, urotropin, sawdust, stearic acid and/or commercially available derivatives thereof or mixtures thereof are used as plasticizing additives in an amount of 0.1 to 15.6 wt.%.
14. The method according to claim 10, characterized in that nitric acid having an acid modulus of 0.10 to 0.30 is used for plasticizing the catalyst working mixture.
15. The method of claim 10, wherein the shaped monolith is air dried at a temperature of 18 to 20 ℃ and a relative humidity of 20 to 90% for 7 to 14 days.
16. The method of claim 10, wherein the monolith is dried at 20 to 90% relative humidity for 7 to 21 days.
17. The method of claim 16, wherein the calcining is carried out at a temperature of 350 to 500 ℃ for 2 to 8 hours.
18. The method according to claim 10, wherein the low temperature calcination is performed at a temperature of 400 to 600 ℃ for not less than 1 to 6 hours, followed by high temperature calcination at a temperature of 900 to 980 ℃ for not less than 1 to 6 hours, optionally followed by increasing the temperature to 1200 ℃.
19. The method according to any one of claims 10 to 18, wherein the strength is not lower than 4.0MPa after 100 to 200 heating cycles from room temperature to 800 ℃ and cooling to room temperature in air in a muffle furnace.
20. Catalytic process for the deep oxidation of hydrocarbons and carbon monoxide, using a catalyst according to any one of claims 1 to 9 produced by a process according to any one of claims 10 to 19, characterized in that it comprises a step of contacting the reaction mixture with the catalyst under catalytic reaction conditions.
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