Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
  • B01D53/8628—Processes characterised by a specific catalyst
• • 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
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/65—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the ferrierite type, e.g. types ZSM-21, ZSM-35 or ZSM-38, as exemplified by patent documents US4046859, US4016245 and US4046859, respectively
  • B01J29/66—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the ferrierite type, e.g. types ZSM-21, ZSM-35 or ZSM-38, as exemplified by patent documents US4046859, US4016245 and US4046859, respectively containing iron group metals, noble metals or copper
  • B01J29/68—Iron group metals or copper
• • 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
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20738—Iron
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20746—Cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/50—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/40—Nitrogen compounds
  • B01D2257/402—Dinitrogen oxide
• • 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
  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)

Definitions

• the present invention relates to a high temperature process for the catalytic decomposition of N 2 0 in a gaseous effluent containing N 2 0 in the presence of a ferriérite zeolite type catalyst exchanged with a transition metal and having a Si / Si ratio. High al.
• Nitrous oxide is a gas that contributes to the greenhouse effect. In particular, it has a radiative power 310 times greater than that of C0 2 and therefore contributes significantly to global warming.
• N 2 0 is formed on platinum webs (a by-product of the oxidation of NH 3 to NO) and is found in tail with NOx not converted to nitric acid.
• N 2 0 is also formed in chemical industries aiming to synthesize caprolactam or hydrocyanic acid, by secondary reaction during a catalytic reaction with ammonia (NH 3 + O 2 for caprolactam or NH 3 + CH 4 for hydrocyanic acid) on platinum canvas. This reaction is very exothermic and the temperature under the cloths is between 800 and 900 ° C.
• the content of N 2 0 is generally between 300 and 2000 ppm and is a function of the age of the fabrics.
• N 2 O is found in the tail gases and can be treated (decomposition or reduction to produce N 2 N 2 ) catalytically, especially on zeolites exchanged with iron ( WO 99/34901 and WO 2008/049557).
• the inventors have been able to demonstrate that it is possible to use ferrierite zeolites (FER) exchanged, partially or totally, with transition metal cations and having a high Si / Al ratio for the treatment of gaseous effluents containing N 2 0 to reduce the N 2 0 content at elevated temperatures, such as those observed after platinum webs in a nitric acid unit.
• FER ferrierite zeolites
• Zeolites are tetrahedral silicoaluminates of the family of crystallized microporous tectosilicates with a high specific surface area, with pore sizes varying according to the structure of the zeolite from 3 to 13 ⁇ .
• zeolites in their natural state that have been known for a long time, the main ones being clinoptilolite, chabazite and mordenite, and synthetic zeolites known since the 1950s with numerous industrial applications implementing their adsorption properties. ions or catalysis.
• Synthetic zeolites unlike natural zeolites, are pure products. To date, more than 200 different structures are known, the main ones being A, faujasite (X and Y), mordenite, ferrierite, pentasil and beta.
• zeolites are obtained by hydrothermal synthesis.
• the structure of zeolites is described as a sequence of Si0 4 and A10 4 " tetrahedra (carrying a negative charge), with pooling of oxygen in the three directions of space: these are the sequences that generate channels and cavities specific to each structure.
• x represents the atomic ratio Si / Al
• w represents the amount of water present
• M represents the compensation cation which is most often Na + (sodium form) and / or optionally K, 1 M compensating for the negative charge related to aluminum (lNa + / l Al) due to the tetrahedral structure (AIO 4 " ) and the pooling of oxygen.
• zeolites are also commercially available in acid or ammonium form, that is to say in a form in which the compensation cations have been exchanged respectively with H + or ⁇ 4 + ions.
• Synthetic zeolites that is to say more than 99% pure, are crystallized microporous silicates whose channel and cavity sizes vary according to the structure between 3 and 13 ⁇ . They are in the form of powdery powder, the size of the crystals being on average a few microns, advantageously between 1 and 2 microns.
• a particular zeolite is used, namely ferrierite, which has two channel arrays whose pore openings are 4.3 ⁇ 5.5 ⁇ and 3.4 ⁇ 4.8 ⁇ .
• the zeolites can be exchanged, partially or totally, with a metal cation, that is to say that the compensation cation is replaced partly or entirely by a metal cation, for example Fe 2+ (2Na + ⁇ 1 Fe 2+ ).
• x is always greater than 1 and represents the atomic ratio Si / Al
• M n represents the compensation cation
• m represents the valence degree of C m
• n represents the valence degree of the compensation cation M n +
• y represents the exchange rate
• the subject of the present invention is thus a process for the catalytic decomposition of N 2 0 in a gaseous effluent containing N 2 0 by passing said gaseous effluent over a ferrierite-type zeolite catalyst bed exchanged, partially or totally, with a transition metal and having an Si / Al ratio of 20 to 40, at a temperature of 800 to 900 ° C, and especially of about 850 ° C.
• the inventors have indeed discovered that zeolites having such an Si / Al ratio were more stable under the process conditions, in particular under the conditions of high temperature, compared to a zeolite having a lower Si / Al ratio.
• Such a process may be used more particularly in a nitric acid unit, behind the platinum webs.
• gaseous effluent containing N 2 0 and “gaseous effluent” are used interchangeably.
• the process of the invention can be carried out at a volumetric rate in h -1
• WH between 30,000 and 120,000 h -1 , advantageously between 50,000 and 100,000 h -1 , in particular between 70,000 and 100,000 h -1 .
• VVH is meant, in the sense of the present invention, the ratio between the flow of gaseous effluent (in Nl / h) and the volume of catalyst used (in liters).
• the pressure used has little influence on the process of the present invention.
• the gaseous effluent used in the context of this process may contain from 200 to 2000 ppm of N 2 O. It will contain mainly nitrogen (N 2 ) and may also contain nitrogen oxides (NOx), water, or oxygen. It may be in particular the gaseous effluent obtained at the exit of the plates of plates of a nitric acid unit.
• a gas generally has the following composition:
• NOx nitrogen oxides
• NOx includes nitrogen monoxide (NO) and carbon dioxide. nitrogen (N0 2 ).
• the ferrierite according to the invention will have an Si / Al ratio of between 22 and 35, preferably of between 25 and 30, and in particular of approximately 27.5.
• the transition metal may be iron or cobalt and in particular iron.
• the transition metal content in ferrierite will be between 0.1 and 3%, preferably between 0.2 and 1.6%.
• the ferrierite used to carry out the partial or total exchange with a transition metal may be in sodium and / or potassium form (that is, the compensation cation that compensates the negative charge of A10 4 " is Na + and / or K + ), in acid form (when the compensation cation is H + ), or in ammonium form (when the compensation cation is NH 4 + ), these different forms being commercially available or easily accessible
• the ammonium form can be obtained from the sodium form by cation exchange in the presence of ammonium sulphate
• the acid form can be obtained from the ammonium form by heat treatment, especially at a temperature of about 400 ° C. or more
• the ferrierite may be in acid form. Under these conditions, the zeolite exchanged with a transition metal according to the invention can meet the following formula:
• C - C m + represents a metal cation of a transition metal, preferably selected from Fe, Fe, Co ZT and C ⁇ T " , more preferably selected from Fe 2+ and Fe 3+ , and preferably being Fe 2+ ,
• m represents the valence of the metal cation C m + (that is to say the number of positive charges borne by this metal cation) and may more particularly represent 1, 2 or 3, and preferably 2 or 3,
• M n + (cation of compensation) represents an alkaline or alkaline-earth ion, such as Na + , K + , Li + or Ca 2+ , an H + ion or a mixture thereof (i.e. that the ⁇ 10 4 "groups are compensated by different cations compensation), preferably Na +, K + and / or H +, including H +,
• n represents the valence of the compensation cation M n + and may more particularly be between 1 and 2, and may be more particularly 1,
• y represents the exchange rate of the compensation cation M n + by the cation C m + and is advantageously between 0.2 and 1, in particular between 0.2 and 0.8, and
• x represents the Si / Al ratio and can be between 20 and 40, advantageously between 22 and 35, preferably between 25 and 30, and especially about 27.5.
• the ferrierite according to the invention will in particular be greater than 99% pure (synthetic ferrierite). It will occur in the form of powder powder, the size of the crystals being on average a few microns, preferably between 1 and 5 microns, especially between 1 and 2 microns.
• the zeolite is exchanged with iron, and preferably with iron (II)
• the binder may be a binder based on silica (for example a gel such as Ludox) or based on alumina (also called aluminous binder).
• the binder will be an aluminous binder, in particular converted into gel by peptization with nitric acid.
• the binder content expressed as A1 2 0 3 or SiO 2 , depending on the type of binder, may be between 10 and 40%, and preferably between 15 and 25% by weight, relative to the total weight of the catalyst.
• the shaping of the catalyst comprising the ferrierite in admixture with a binder may be carried out through a die after having obtained, continuously, in an Aoustin-type mixer, a homogeneous mixture and optimized rheology between the zeolite and the binder. , in particular A1 2 0 3 peptized with HN0 3 . It is thus possible to obtain extrudates of different sizes (for example between 1.8 and 3.2 mm in diameter and with a length of 5 to 10 mm).
• Especially shaped "pellets” can be manufactured to limit pressure drops, for example, trilobal extrusions, “hollows” (hollow extrusions) or extrusions of 6 to 8 mm with 1 mm holes.
• the parameters that will influence the exchange, and thus the final content of C m + cation after exchange, will include the temperature, the concentration of metal salt in the solution, the solution / volume ratio of ferrierite (V / P), and the reaction time.
• the zeolite obtained after exchange will advantageously be heat treated, especially at a temperature of about 400 ° C. or more.
• FIG. 1 represents the evolution of the conversion rate of N 2 0 in N 2 and O 2 over time and according to the hourly volumetric velocity VVH for a catalyst according to the invention.
• FIG. 2 shows the evolution of the conversion rate of N 2 O to N 2 and O 2 over time for a ferrierite-based catalyst with an Si / Al ratio of 8.8.
• a ferrierite zeolite, commercial, acid form, whose Si / Al (atomic) ratio is 27.5 was used.
• This zeolite is exchanged from an iron salt, sulphate FeSO 4 ⁇ 7H 2 0, in aqueous solution.
• the zeolite exchanged is recovered by filtration on a filter funnel and is washed by percolation with a liter of demineralised water (conductivity ⁇ 10 ⁇ ).
• the zeolite exchanged with iron is dried at 100 ° C.
• the iron content measured by ICP (Inductively Coupled Plasma, plasma torch) is 0.7% (on dry product).
• the iron ferrierite zeolite whose preparation is described above is pelletized (without binder) in pellets 5 mm in diameter which are then heat-treated at 400 ° C. in air for three hours. This is followed by crushing and sieving these pellets between 0.1 and 1 mm to carry out the catalytic test described below. The test is conducted in a 1 "(2.7 cm) diameter fixed bed reactor surrounded by heating shells.
• the reaction mixture is prepared from dry air, nitrogen and a standard 2% N 2 O bottle in N 2 . Concentrations are controlled by mass flow meters and saturator adjusted water content.
• the operating conditions are as follows:
• the analysis of the N 2 O content at the inlet and the outlet is determined by infrared analysis.
• the operating conditions are identical, namely a VVH of 50000 h -1 and a temperature of 850 ° C.
• the conversion of N 2 0 is then> 99.8% and the output is the 2000 ppm of NO which have not been broken down.
• a catalyst was prepared from a ferrierite having an Si / Al ratio of 8.8 by exchange with ammonium sulphate and then exchanged with 0.5M iron sulphate under the same conditions as for the catalyst according to US Pat. invention.
• This catalyst was used under the same catalytic test conditions as for the catalyst according to the invention, except that the VVH was not increased over time.

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• Chemical & Material Sciences (AREA)
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• 2010
  • 2010-08-26 FR FR1056785A patent/FR2964043B1/fr not_active Expired - Fee Related
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