EP2451573A2 - Catalyseur de h2-scr contenant du platine supporté par un oxyde mixte promu de magnésium et cérium - Google Patents

Catalyseur de h2-scr contenant du platine supporté par un oxyde mixte promu de magnésium et cérium

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Publication number
EP2451573A2
EP2451573A2 EP10722966A EP10722966A EP2451573A2 EP 2451573 A2 EP2451573 A2 EP 2451573A2 EP 10722966 A EP10722966 A EP 10722966A EP 10722966 A EP10722966 A EP 10722966A EP 2451573 A2 EP2451573 A2 EP 2451573A2
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EP
European Patent Office
Prior art keywords
catalyst
ceo
promoted
mgo
platinum
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EP10722966A
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German (de)
English (en)
Inventor
Angelos M. Efstathiou
George Olympiou
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University of Cyprus
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University of Cyprus
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Priority to EP10722966A priority Critical patent/EP2451573A2/fr
Publication of EP2451573A2 publication Critical patent/EP2451573A2/fr
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/648—Vanadium, niobium or tantalum or polonium
    • B01J23/6482—Vanadium
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    • 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
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
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    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/652—Chromium, molybdenum or tungsten
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/19—Catalysts containing parts with different compositions
    • 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
    • B01J37/0027—Powdering
    • B01J37/0036—Grinding
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0205—Impregnation in several steps
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    • B01J37/02—Impregnation, coating or precipitation
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    • 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
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2251/202—Hydrogen
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    • B01D2255/2047—Magnesium
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
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    • B01D2255/2065—Cerium
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D2255/20723—Vanadium
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    • B01D2255/20769—Molybdenum
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    • B01D2255/20776—Tungsten
    • 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
    • B01D53/26—Drying gases or vapours
    • B01D53/261—Drying gases or vapours by adsorption
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    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B01J35/45—Nanoparticles

Definitions

  • Catalyst consisting of Platinum supported on chemically promoted Magnesium Oxide and Cerium Dioxide towards H?-SCR
  • This invention refers to a catalyst comprising platinum on a support, a process for the preparation of such a catalyst, and a use of such a catalyst.
  • This catalyst can be used in the selective conversion of nitric oxide (NO) or nitric dioxide (NO 2 ) produced in many industrial combustion processes, in the manufacture of nitric acid, etc., to N 2 gas using hydrogen (H 2 ) as a reducing agent (H 2 -SCR). It is known that hydrogen is available in numerous industrial installations. Using the said catalyst, only a very small percentage of the available hydrogen is necessary for the reduction of NO x to N 2 under strongly oxidizing conditions (H 2 -SCR) in the low- temperature range of 100-200 0 C.
  • H 2 -SCR strongly oxidizing conditions
  • Selective catalytic reduction (SCR) of NO x from an industrial flue gas stream at low- temperatures has many advantages over that at higher temperatures (e.g., T>250°C).
  • placement of the catalyst after the electrostatic dust precipitator unit implies that the partially cleaned flue gas from dust requires less soot blowing and catalyst cleaning, thus providing longer catalyst lifetime.
  • low- temperature SCR process can reduce both the investment and operating costs since the SCR unit can be installed at the end of the stack gas train, thus minimising the need to run ductwork from a high-temperature region and then return the flue gas to the stack gas train.
  • less reheating of the flue gas from the de-SO x to the SCR unit is required [4,5].
  • New low-temperature NO x control SCR catalysts are also capable of retrofitting existing large utility boilers and installations (e.g. industrial furnaces) firing natural gas or refinery fuel gas, where better heat economy of the whole flue gas after- treatment process is achieved.
  • a low-temperature H 2 -SCR of NO x technology can be considered as breakthrough green and clean industrial NO x control technology compared to the existing NH 3 -SCR technology.
  • Supported-palladium catalysts have also been investigated towards H 2 -SCR [57-63] but to a significantly less extent than supported-platinum catalysts.
  • low- temperature NO x control has been also studied with H 2 /CO [64-67] and H 2 /CO/CH 4 [68] reducing gas mixtures over supported-palladium catalysts. It appears from these reports that N 2 -selctivity of H 2 -SCR might be lower or higher than that obtained over supported-platinum catalysts at the same temperature in a non-obvious way, while NO conversion appears in general to be lower on supported-palladium compared to supported-platinum catalysts for the same experimental conditions.
  • EP 1 475 149 (2008) discloses a catalyst for NO x control comprising platinum in an amount between 0.1 and 2.0 wt% dispersed on a pre-nitrated and pre-sulphated mixed metal oxide support of magnesium and cerium [55, 56].
  • the latter supported platinum catalyst provides a high activity (NO conversion larger than 90%) and N 2 -selectivity (up to 82%) at low reaction temperatures (e.g. 140-160 0 C) when hydrogen is used as reducing agent at reaction temperatures between 100 0 C and 200 0 C.
  • the object of the present invention is the development of an alternative catalyst for the selective conversion of NO x to N 2 by hydrogen (H 2 ) to that reported [55,56] with significantly better performance in the 110-180 0 C range and in the presence of large concentrations of water (ca. 20 vol%) and carbon dioxide (ca. 10 vol%) in the simulated flue gas stream to be purified.
  • catalyst comprising platinum as noble metal, which is dispersed on a mixed metal oxide support of magnesium and cerium, charaterized in that the mixed metal oxide support of magnesium and cerium is chemically promoted by one of the following elements or compound of the following elements: vanadium, sodium, potassium, molybdenum or tungsten.
  • the inventive idea is the use of specific "chemical promoters" in combination with magnesia, ceria, and platinum in an appropriate composition (wt%) along with the application of an appropriate activation step to the final catalyst formed in a non- obvious way for achieving its effective H 2 -SCR of NO x performance.
  • chemical promoter here implies the addition of a chemical compound in the final catalyst composition that would enhance the chemical function of the catalyst [69].
  • chemical function is meant the selective conversion of NO x (NO/NO 2 ) into N 2 gas by the use of hydrogen from a gas mixture containing NO x , oxygen, carbon dioxide, and water, and especially in the low-temperature range of 110-180 0 C.
  • the role of "chemical promoter” is to enhance the rate of conversion of NO x into N 2 than any other by-product (e.g. N 2 O, NH 3 ).
  • the "chemical promoter" in the mixed metal oxide support of magnesium oxide and cerium dioxide could provide other centers for NO x adsorption, thus changing the concentration and reactivity of the active surface absorbed NO x species formed, which are then reduced by hydrogen into N 2 and H 2 O [71 ,72].
  • the "chemical promoter” could interact directly with the platinum, since some platinum is expected to be found on the surface of oxides or compounds of the “chemical promoter”. Thus, different catalytic active components could have been expected to be formed.
  • the "chemical promoter” may change the electronic structure of the catalytic surface which in turn could affect the catalysis at hand through alterations in the binding strength of adsorbed species or surface concentrations or energy barriers for hydrogen diffusion on the catalyst surface [71]. Therefore, very high conversion rates of NO x into nitrogen (N 2 -selectivity) by hydrogen in the temperature range of 110 - 180 0 C could be achieved.
  • the mean primary crystal size of the mixed metal oxide support phases is between 5 and 10 nm.
  • the mean primary crystal size is determined by X-ray diffraction and using the Scherrer relationship [73].
  • the support is a mixture of vanadium-promoted magnesium oxide and vanadium-promoted cerium dioxide, whereby vanadium (V) oxide (V 2 O 5 ) in an amount between 0.1 wt% and 12 wt%, preferably between 2 wt% and 8 wt%, most preferred between 3.0 wt% and 5 wt%, is used as chemical promoter.
  • vanadium (V) oxide V 2 O 5
  • platinum is dispersed in an amount between 0.01 and 2.0 wt% on the promoted mixed metal oxide support (MgO-CeO 2 ).
  • palladium (Pd) in an amount between 0.01 and 2.0 wt% as a second noble metal is dispersed on the mixed metal oxide support.
  • 0.1 wt% of platinum and 0.05 wt% of palladium are dispersed on the promoted mixed metal oxide support.
  • High N 2 -selectivity values could be obtained by using a catalyst comprising of platinum and palladium between 0.01 and 2.0 wt%, wherein the platinum and palladium noble metal are dispersed on a preferably vanadium-promoted MgO and CeO 2 mixed metal oxide.
  • the use of primary crystals with a mean crystal size larger than 40 nm is also advantageous.
  • the promoted mixed metal oxide support consists of magnesium oxide and cerium dioxide solid phases in the ratio between 50:50 and 70:30 (w/w), respectively, depending on the primary crystal size of MgO and CeO 2 used.
  • the present invention refers also to a process for obtaining catalyst comprising platinum dispersed on a mixture of promoted magnesium oxide and promoted cerium dioxide comprising the steps:
  • the promoter is one of the following elements or a compound of the following elements: vanadium (V), sodium (Na) 1 potassium (K), molybdenum (Mo) or tungsten (W),
  • 35O 0 C range for at least 1 h.
  • the present invention refers to a process for obtaining a catalyst comprising platinum and palladium dispersed on a mixture of promoted magnesium oxide and promoted cerium dioxide comprising the steps:
  • the promoter is one of the following elements or a compound of the following elements: vanadium (V), sodium (Na), potassium (K), molybdenum (Mo) or tungsten (W) 1
  • 35O 0 C range for at least 1 h.
  • the activation of the said catalyst compositions is crucial for the catalyst performance (activity, N 2 -selectivity and stability) towards H 2 -SCR, where optimum calcination and reduction conditions (gas compostion, temperature, time on stream) depend on Pt, Pd, and chemical promoter loading (wt%).
  • the temperature at which activation of the catalyst as prepared is conducted in a flow of O 2 /He gas mixture (calcination step) followed by a flow of H 2 /He gas mixture (reduction step), and the time on stream allowed for each activation step are crucial parameters that strongly influence the activity (NO conversion) and N 2 -selectivity of the H 2 -SCR process.
  • the catalyst should be used for the NO x reduction in gas streams containing SO x , an additional step for the pre-nitration and pre-sulphatation of the catalyst is advantageous.
  • the presence of sulphates on the MgO-CeO 2 support of the present invented catalyst does not exhibit any chemical promoting effect.
  • the "chemical promoter” is one of the elements of vanadium, sodium, potassium, molybdenum and tungsten.
  • a surface compound of magnesium is formed by interaction between NO x (NO and NO 2 ) species present in the gaseous phase under reaction conditions and the oxide of magnesium present.
  • a surface compound of cerium is formed by interaction between NO x (NO and NO 2 ) species present in the gaseous phase under reaction conditions and the oxide of cerium present.
  • a surface compound of vanadium is formed by interaction between NO x (NO and NO 2 ) species present in the gaseous phase under reaction conditions and the oxide of vanadium present.
  • surface compounds of platinum and palladium are formed by interaction between species present in the gaseous phase under reaction conditions (NO, NO 2 , O 2 ) and metallic platinum and palladium present.
  • the present invention also refers to the selective reduction of nitric oxide, nitrogen dioxide and/or mixture of nitric oxide and nitrogen dioxide to N 2 gas using hydrogen as reducing agent in the presence of the catalysts described herein.
  • the inventive catalyst is used for the reduction of a chemical compound selected from the group consiting of nitrogen oxide, nitrogen dioxide or a mixture of both to nitrogen using hydrogen as reducing agent in the presence or absence of oxygen.
  • One embodiment of the invention also refers to a method of reducing a chemical compound selected from the group consisting of NO, NO 2 and/or a mixture of NO and NO 2 to N 2 gas using hydrogen as reducing agent in the presence of oxygen, and also in the presence of other gases, for example H 2 O and CO 2 , by a catalyst comprising Pt in an amount between 0.01 and 2.0 wt% and Pd in an amount between 0.01 and 2.0 wt%, dispersed on a vanadium-promoted MgO and CeO 2 .
  • a reactor selected from the group consisting of a fixed-bed and a monolithic-type reactor can be used.
  • the present invention provides a variety of advantages.
  • the N 2 -selectivity of a catalyst comprising platinum and palladium dispersed on a vanadium-promoted MgO and vanadium- promoted CeO 2 mixed metal oxide was remarkably increased by 10-30 percentage units in the H 2 -SCR of NO at temperatures in the 120-160 0 C low-temperature range compared to platinum dispersed on a mixed metal oxide of MgO and CeO 2 according to prior art.
  • Pt/MgO-CeO 2 , PW-MgO-CeO 2 , and Pt-Pd/V-MgO-CeO 2 catalysts were prepared by means of the wet impregnation method as follows:
  • 0.5 g of commercial nano-crystalline MgO (Aldrich, product no. 549649, mean primary crystal size 9.0 nm) or MgO with larger mean primary crystal size (Aldrich, product no. 288667, mean primary crystal size 44 nm) were mechanically mixed with 0.5 g of commercial nano-crystalline CeO 2 (Aldrich, product no. 544841 , mean primary crystal size 5 nm) or CeO 2 with larger mean primary crystal size (Aldrich, product no. 211575, mean primary crystal size 41 nm), and the resulting solid (1.0 g) was impregnated with 200 ml of an aqueous solution containing the desired quantity of hexachloroplatinic acid solution (Aldrich, product no.
  • the catalyst is activated first in a flow of air or 10 vol% O 2 /He gas mixture in the 500-650 0 C range for 1-2 h, and then reduced in a flow of 10-15 vol% H 2 /He gas mixture in the 200-350 0 C range for at least 1 h.
  • the content of metallic platinum varied in the 0.01-2.0 wt% range.
  • the catalyst is activated first in a flow of air or 10 vol% O 2 /He gas mixture in the 500-650 0 C range for 1-2 h, and then reduced in a flow of 10-15 vol% H 2 /He gas mixture in the 200- 350 0 C range for at least 1 h.
  • the content of metallic platinum varied in the 0.01-2.0 wt% range.
  • V-MgO-CeO 2 prepared according to the same procedure as in the case of PW-MgO-CeO 2 solid, was impregnated with 200 ml of an aqueous solution containing the desired quantity of hexachloroplatinic acid (Aldrich, product no. 262587). The excess of water was evaporated with continuous stirring at 60-70 0 C and the residue was dried at 120 0 C for ⁇ 12 h. The dry residue was sieved and heated at 500 0 C in a flow of air or 20%O 2 /He gas mixture for at least 2 h.
  • the solid material was again impregnated with 200 ml of an aqueous solution containing the desired quantity of palladium(ll) nitrate solution (Aldrich, product no. 380040).
  • the excess of water was evaporated with continuous stirring at 60-70 0 C and the residue was dried at 120 0 C for ⁇ 12 h.
  • the dry residue was sieved and heated at 500 0 C in a flow of 20%O 2 /He for at least 2 h in order to remove chlorine and nitrates from the solid surface and convert Pt and Pd into their respective metal oxides, cooled to room temperature and stored for further use.
  • the catalyst is activated first in a flow of air or 10 vol% O 2 /He gas mixture in the 500-650 0 C range for 1-2 h, and then reduced in a flow of 10-15 vol% H 2 /He gas mixture in the 200-350 0 C range for at least 1 h.
  • the content of metallic platinum (Pt) and palladium (Pd) was varied in the 0.01-2.0 wt% and 0.01-2.0 wt% range, respectively.
  • Example 9 the combination of Pt, Pd, V, MgO and CeO 2 , the latter two solids having a primary crystal size larger than 40 nm, with the said chemical composition in a non-obvious way, resulted in remarkable improvements of N 2 - selectivity (10-30 percentage units) in the low-temperature range of 120-180 0 C for the H 2 -SCR process at the said feed gas composition as compared to the Pt/MgO-CeO 2 catalyst chemical composition previously reported by us [55,56].
  • a catalyst sample of 0.62 g was placed in a fixed-bed quartz micro-reactor, and it was first activated in a flow of 10%O 2 /He gas mixture (100 NmL/min) at 500 0 C for 1 h, followed by H 2 reduction (12.5%H 2 /He, 100 NmL/min) at 250 0 C for 1 h before a reaction feed gas mixture of 325 ppm NO, 0.8 vol% H 2 , 2.5 vol% O 2 , 10 vol% CO 2 , 20 vol% H 2 O and 66.67 vol% He at a GHSV of 40,000 h 1 (Lgas/Lca t .b e d /h) was used.
  • Figure 1 clearly demonstrates that the use of 3.5 wt% V 2 O 5 -MgO-CeO 2 (magnesium oxide and cerium dioxide chemically promoted with vanadia) as a carrier to deposit 0.2 wt% Pt resulted in a remarkable improvement of both the NO conversion and N 2 - selectivity, especially at the lowest temperatures (130-150 0 C) investigated, compared to the case of use of MgO-CeO 2 carrier alone.
  • the NO conversion (X NO , %) was increased from 20.5% to 72.5% (an increase by a factor of ⁇ 3.5), whereas at 18O 0 C from 60.0 to 96.0% (an increase by a factor of 1.6).
  • the high NO conversions (73.5 - 97.0%) obtained in the 130-180 0 C range under the given experimental conditions is noted which are representative of many industrial flue gas compositions and space velocities encountered.
  • N 2 -selectivity of H 2 -SCR reaction the effect of vanadia was to siginificantly enhance N 2 -selectivities (S N2 , %) to values of 90% in the 160-180 0 C range, and 72-87% in the 130-150 0 C range.
  • Example 2 The experimental conditions were the same as those presented in Example 2, except that now a feed flue gas composition of 175 ppm NO, 0.8 vol% H 2 , 2.5 vol% O 2 , 10 vol% CO 2 , 20 vol% H 2 O and 66.69 vol% He was used.
  • the beneficial effect of vanadia promoter on the X NO (%) and S N2 (%) is now larger compared to the previous Example 2 (use of 325 ppm NO in the feed stream).
  • Very high NO conversions (85.0 - 98.7%) were seen in the 130-180 0 C range, and N 2 - selectivities of 80-90% in the same temperature range were obtained.
  • the NO conversion (X N0 , %) was increased from 11.0 to 85.0% (increase by a factor of 7.7), whereas the N 2 -selectivity (S N2 , %) from 14.0 to 80.0% (increase by a factor of 5.7).
  • vanadia loadings in the 0.1 - 12.0 wt% V 2 O 5 range were investigated over various MgO-CeO 2 support compositions (0-100 wt% MgO) and using 0.1-2.0 wt% Pt loadings.
  • vanadia loading by increasing the vanadia loading from 3.5 to 5 wt% V 2 O 5 , an increase of NO conversion by 10-20 percentage units was seen at the lowest temperatures of 120-130 0 C for the 0.2 wt% Pt-supported catalyst with the MgO-CeO 2 support composition and feed gas compositions mentioned previously (Examples 2 and 3). Improvements up to 10-15 percentage units were seen in the N 2 -selectivity for the given catalyst composition.
  • the optimum vanadia loading for catalyst performance (X NO (%) and S N2 (%)) was found to depend on the BET area of support composition, the primary crystal size of MgO and CeO 2 support, and the Pt loading (wt%) used.
  • a pre-sulphated MgO-CeO 2 support used to deposit 0.2 wt% Pt was also not able to prevent catalytic activity loss. However, in this case the activity loss was less than that observed with the 0.2 wt% Pt/MgO-CeO 2 (Fig. 3) catalyst and larger than that observed with the 0.2 wt% Pt/3.5wt%V 2 O 5 -MgO-CeO 2 catalyst (Fig. 3).
  • a very important parameter that determines the catalytic performance of the PW 2 O 5 - MgO-CeO 2 solid towards its effective low-temperature H 2 -SCR performance (NO conversion and N 2 -selectivity) is the way the as prepared catalyst is activated before reaction (contact with the flue gas for NO x purification).
  • Catalyst activation includes calcination (use of O 2 /He or air gas flow) and reduction (use of H 2 /He gas mixture or pure hydrogen flow) steps at a given temperature and for a given time on stream. This parameter is illustrated by experimental data obtained and presented in Table 1 for the 0.2 wt% Pt/3.5wt%V 2 O 5 -MgO-CeO 2 catalyst, the same used in Examples 2-4.
  • the NO-conversion and N 2 -selectivity versus reaction temperature (T, 0 C) profile is strongly influenced by the activation steps performed on the given catalytic system before H 2 -SCR reaction.
  • catalyst activation by H 2 reduction only performed at 300 0 C for 14 h results in high NO conversion values (88.5-97.0%) in the whole 125-18O 0 C range, but with N 2 -selectivity values in the 66-80% range.
  • both the NO conversion and N 2 -selectivity values obtained become significantly lower in the whole temperature range of 125-18O 0 C, when compared to the case of 500 0 C calcination.
  • N 2 -selectivities larger in the 160-180 0 C range but lower in the 125-15O 0 C range are obtained.
  • lower NO conversion values are obtained in the whole 125-18O 0 C range.
  • Pt loading (wt%) is a very important parameter that determines not only the catalytic performance (NO conversion and N 2 -selectivity) of Pt/MgO-CeO 2 solid towards H 2 -SCR [53-56] but also the economics of the associated technology for industrial applications.
  • Figure 4 illustrates that using only 0.1 wt% R supported on the MgO-CeO 2 carrier, the latter promoted with 3.5 wt% V 2 O 5 , results in an excellent H 2 -SCR performance in the 140-18O 0 C range, where both NO conversion and N 2 -selectivity exchibit values larger than 90%.
  • Examples 2-7 where smaller primary crystals for the MgO-CeO 2 support were used.
  • a catalyst sample of 0.3-g was placed in a fixed-bed quartz micro-reactor, and it was first calcined in 20%O 2 /He gas flow (50 NmL/min) at 600 0 C for 2 h, followed by H 2 reduction (1 bar H 2 , 50 NmLJmin) before a reaction feed gas mixture consisting of 500 ppm NO, 0.8 vol% H 2 , 5 vol% O 2 and 94.15 vol% He or 500 ppm NO, 0.8 vol% H 2 , 5 vol% O 2 , 10 vol% CO 2 , and 84.15 vol% He at a GHSV of 40,000 h 1 was used.
  • Figure 6 clearly demonstrates that the use of 3.5 wt% V 2 O 5 -MgO-CeO 2 (magnesium oxide and cerium dioxide promoted with vanadia) as carrier to deposit 0.1 wt% Pt resulted in a remarkable improvement of NO conversion when 10 vol% CO 2 was also present in the reaction feed stream, compared to the case of use of MgO-CeO 2 carrier alone.
  • the NO conversion (%) was increased from 15% to 57% (an increase by a factor of 3.8), whereas at 140 and 16O 0 C an increase by a factor of 2.3 and 1.7, respectively, was obtained.
  • Similar results to those depicted in Fig. 6 were obtained when 20 vol% H 2 O was also present in the 500 ppm NO, 0.8 vol% H 2 , 5 vol% O 2 , 10 vol% CO 2 , He reaction feed gas composition.
  • Vanadium (V) loadings in the 0.1-12 wt% range were investigated, where it was found that the optimum loading for the 0.1 wt% Pt/x wt% V-MgO-CeO 2 catalytic system strongly depends not only on the reaction feed gas composition in NO, O 2 and H 2 gases but also on the primary crystal size of MgO and CeO 2 support used, as it is illustrated in the following Example 9.
  • Figure 6 presents also the effect of 2 wt% vanadium (V) loading on the N 2 -selectivity (S N2 , %) of the H 2 -SCR of NO under the same reaction conditions described for the NO-conversion versus T profile (500 ppm NO, 0.8 vol% H 2 , 5 vol% O 2 , 10 vol% CO 2 , and 84.15 vol% He). It is seen that in the lowest reaction temperature range of 110- 13O 0 C, an increase in S N2 (%) between 6 and 15 percentage units was observed, whereas at higher temperatures S N2 (%) was practically the same. Siginificantly larger N 2 -selectivity values were obtained at another V loading (wt%) and feed gas composition, as illustrated in the following Example 9, and also after using smaller primary crystals for MgO and CeO 2 support phases (see Examples 2 and 3).
  • V vanadium
  • Pt loadings in the 0.01 - 2.0 wt% range were investigated, where an optimum Pt loading in the 0.1-0.3 wt% range was found, depending on vanadia loading, feed gas composition, and primary crystal size of MgO-CeO 2 support.
  • Pt and Pd loadings lower than 0.05 wt% or larger than 2.0 wt% did not result in better catalytic performance (S N2 , %) as that presented in Fig. 7.
  • An optimum Pt and Pd loading was found to depend on the loading (wt%) of V, the mean primary crystal size of MgO and CeO 2 , and also on their wheight ratio (w/w) used to deposit V, Pt and Pd.
  • Example 10 This example illustrates the effect of using nano-crystalline MgO and CeO 2 support phases (mean primary crystal size lower than 10 nm) to deposit the combination of Pt and V catalytic and chemical promoter components, respectively, on the low- temperature H 2 -SCR of NO in terms of NO conversion, X N o(%) and N 2 -selectivity, S N2 (%) at a feed containing larger NO concentrations (e.g. 500 ppm) as compared to the cases presented in Examples 2 and 3.
  • a catalyst sample of 0.3 g and a feed gas composition of 500 ppm NO, 0.7 vol% H 2 , 3 vol% O 2 and 96.25 vol% He at a GHSV of 40,000 h "1 were used.
  • Figure 1 illustrates the strong chemical promoting effect of vanadia when deposited on MgO and CeO 2 support solid phases (70 wt% MgO-30 wt% CeO 2 ) on the NO conversion, X N o(%), and N 2 -selectivity, S N2 (%) of H 2 -SCR in the low-temperature range of 130-18O 0 C for the 0.2 wt%Pt/3.5wt% V 2 O 5 -MgO-CeO 2 catalyst.
  • Figure 3 illustrates the strong chemical and likely structural promoting effect of vanadia when deposited on MgO and CeO 2 support solid phases (70 wt% MgO-30 wt% CeO 2 ) on the stability with time on stream (up to 70 h) of NO conversion, X NO (%), and N 2 - selectivity, S N2 (%) of H 2 -SCR at 16O 0 C for the 0.2 wt%Pt/3.5wt% V 2 O 5 -MgO-CeO 2 catalyst.
  • Figure 4 illustrates the catalytic performance in terms of NO conversion, X NO (%), and N 2 -selectivity, S N2 (%) of H 2 -SCR in the low-temperature range of 120-180 0 C over a low- loading 0.1 wt%Pt supported on vanadia-promoted support (3.5wt% V 2 O 5 -MgO-CeO 2 ).
  • Figure 5 illustrates the effect of increasing the vanadia loading from 3.5 to 5.0 wt% on the catalytic activity in terms of NO conversion, X NO (%) of H 2 -SCR in the low- temperature range of 120-180 0 C for the 0.2 wt%Pt supported on vanadia- promoted support (3.5 or 5.0 wt% V 2 O 5 -MgO-CeO 2 ).
  • Figure 6 illustrates the effect of 2 wt% vanadium deposited on MgO and CeO 2 support solid phases (50 wt% MgO-50 wt% CeO 2 ) on the NO conversion, X N o(%) and N 2 - selectivity, S N2 (%) of H 2 -SCR in the low-temperature range of 110-180 0 C for the 0.1 wt%Pt/2 wt% V-MgO-CeO 2 catalyst.
  • X N o(%) versus reaction temperature, T( 0 C) behaviour over the 0.1 wt% Pt/MgO-CeO 2 (absence of 2 wt% V) is also presented.
  • the mean primary crystal size of MgO and CeO 2 support phases used was 44 and 41 nm, respectively.
  • Figure 7 compares the N 2 -selectivity, S N2 (%) of H 2 -SCR obtained in the low- temperature range of 120-18O 0 C over 0.1 wt% Pt supported on MgO-CeO 2 ( ⁇ ) or 8 wt% V-MgO-CeO 2 (•), and 0.1 wt% Pt - 0.05 wt% Pd supported on 8 wt% V-MgO-
  • Figure 8 illustrates the effect of 8 wt% vanadium deposited on MgO and CeO 2 support solid phases (50 wt% MgO-50 wt% CeO 2 ) on the NO conversion, X N o(%) and N 2 - selectivity, S N2 (%) of H 2 -SCR in the low-temperature range of 120-180 0 C over 0.1 wt% Pt/8 wt% V-MgO-CeO 2 catalyst.
  • Figure 9 illustrates the effect of catalyst (0.2wt%Pt/3.5wt%V 2 O 5 -MgO-CeO 2 ) activation conditions on its performance in terms of NO conversion (X N0 , %), N 2 -selectivity (S N2 , %), and H 2 conversion (X H2 , %).

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Abstract

Cette invention porte sur un nouveau catalyseur d'activité et sélectivité excellentes destiné à la réduction d'oxydes nitriques (NO/NO2) en azote gazeux (N2), de l'hydrogène (H2) étant utilisé comme agent réducteur dans des conditions fortement oxydantes (par exemple 2 à 10 % en volume d'O2) (RCS par H2) dans la plage de 100 à 400°C, mais en particulier dans la plage de basses températures de 110 à 180°C. Le catalyseur de l'invention est constitué de nanoparticules de platine et de palladium ayant une morphologie et une structure de surface appropriées qui sont en contact avec des phases solides d'un milieu de MgO et CeO2 mélangés activés par exemple par de l'oxyde de vanadium (par exemple V2O5).
EP10722966A 2009-06-16 2010-06-10 Catalyseur de h2-scr contenant du platine supporté par un oxyde mixte promu de magnésium et cérium Withdrawn EP2451573A2 (fr)

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EP09007863A EP2269729A1 (fr) 2009-06-16 2009-06-16 Catalyseur pour H2-SCR contenant du platine supporté par un oxyde mixte promu de magnésium et cérium
PCT/EP2010/003494 WO2010145777A2 (fr) 2009-06-16 2010-06-10 Catalyseur constitué de platine supporté sur de l'oxyde de magnésium et du dioxyde de cérium chimiquement activés destiné à la rcs par h2
EP10722966A EP2451573A2 (fr) 2009-06-16 2010-06-10 Catalyseur de h2-scr contenant du platine supporté par un oxyde mixte promu de magnésium et cérium

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EP4252891A3 (fr) 2016-10-18 2023-12-20 BASF Corporation Réduction des nox à basse température à l'aide de h2-scr pour véhicules diesel
CN110801849B (zh) * 2019-10-10 2022-07-15 北京华电光大环境股份有限公司 平板式宽温抗硫抗碱金属scr脱硝催化剂及其制备方法
CN110801848B (zh) * 2019-10-10 2022-07-15 北京华电光大环境股份有限公司 平板式宽温抗硫scr脱硝催化剂及其制备方法
CN113786828B (zh) * 2021-09-16 2023-12-29 清华大学 一种用于NOx和CVOCs的协同脱除的催化剂及其制备方法和用途
EP4282513A1 (fr) * 2022-05-23 2023-11-29 Basf Corporation Catalyseurs améliorés pour la réduction sélective de nox à l'aide d'hydrogène

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EP1358933A4 (fr) * 2001-02-02 2005-08-10 Hitachi Ltd Catalyseur de traitement des gaz d' mission et moteur combustion interne pourvu d'un tel catalyseur
US7138358B2 (en) * 2001-11-13 2006-11-21 Sud-Chemie Inc. Catalyzed diesel particulate matter filter with improved thermal stability
ES2192985B1 (es) 2002-02-15 2005-02-16 Consejo Sup. Investig. Cientificas Nuevo catalizador para la reduccion de no a n2 con hidrogeno en condiciones de nox oxidantes.

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