WO2023089352A1 - Metal supported oxide nh3-scr catalysts having hetero-dual sites and synthesis processes - Google Patents
Metal supported oxide nh3-scr catalysts having hetero-dual sites and synthesis processes Download PDFInfo
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- WO2023089352A1 WO2023089352A1 PCT/IB2021/000830 IB2021000830W WO2023089352A1 WO 2023089352 A1 WO2023089352 A1 WO 2023089352A1 IB 2021000830 W IB2021000830 W IB 2021000830W WO 2023089352 A1 WO2023089352 A1 WO 2023089352A1
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- 239000003054 catalyst Substances 0.000 title claims abstract description 103
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 68
- 239000002184 metal Substances 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 46
- 230000008569 process Effects 0.000 title claims abstract description 43
- 230000015572 biosynthetic process Effects 0.000 title description 19
- 238000003786 synthesis reaction Methods 0.000 title description 11
- 239000000463 material Substances 0.000 claims abstract description 134
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims abstract description 98
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims abstract description 84
- 239000010955 niobium Substances 0.000 claims abstract description 82
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 57
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 38
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 35
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 25
- 230000009467 reduction Effects 0.000 claims abstract description 18
- 238000006722 reduction reaction Methods 0.000 claims abstract description 18
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 17
- 239000010937 tungsten Substances 0.000 claims abstract description 16
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 15
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 15
- 229910052715 tantalum Inorganic materials 0.000 claims abstract description 15
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052742 iron Inorganic materials 0.000 claims abstract description 14
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims abstract description 13
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 11
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 11
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 11
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 9
- 238000010531 catalytic reduction reaction Methods 0.000 claims abstract description 9
- 229910052741 iridium Inorganic materials 0.000 claims abstract description 9
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910052707 ruthenium Inorganic materials 0.000 claims abstract description 7
- 150000001875 compounds Chemical class 0.000 claims description 63
- 239000010948 rhodium Substances 0.000 claims description 45
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 36
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 32
- 239000002243 precursor Substances 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 15
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 14
- 239000012298 atmosphere Substances 0.000 claims description 9
- 125000003545 alkoxy group Chemical group 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 125000004432 carbon atom Chemical group C* 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 7
- 125000000951 phenoxy group Chemical group [H]C1=C([H])C([H])=C(O*)C([H])=C1[H] 0.000 claims description 7
- 125000004213 tert-butoxy group Chemical group [H]C([H])([H])C(O*)(C([H])([H])[H])C([H])([H])[H] 0.000 claims description 7
- -1 1, 3, 5-tri methylphenyl Chemical group 0.000 claims description 6
- 125000000217 alkyl group Chemical group 0.000 claims description 6
- 125000003118 aryl group Chemical group 0.000 claims description 6
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 5
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- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 claims description 3
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- 125000001183 hydrocarbyl group Chemical group 0.000 claims 3
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- LVGLLYVYRZMJIN-UHFFFAOYSA-N carbon monoxide;rhodium Chemical group [Rh].[Rh].[Rh].[Rh].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-] LVGLLYVYRZMJIN-UHFFFAOYSA-N 0.000 description 16
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 13
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 11
- 229910015189 FeOx Inorganic materials 0.000 description 10
- JCXJVPUVTGWSNB-UHFFFAOYSA-N Nitrogen dioxide Chemical compound O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 9
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- 125000002524 organometallic group Chemical group 0.000 description 7
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- 239000003446 ligand Substances 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 229910016553 CuOx Inorganic materials 0.000 description 5
- 238000004873 anchoring Methods 0.000 description 5
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- 238000001914 filtration Methods 0.000 description 5
- 238000005470 impregnation Methods 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
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- 229910052905 tridymite Inorganic materials 0.000 description 5
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 4
- 238000001994 activation Methods 0.000 description 4
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- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000004611 spectroscopical analysis Methods 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- SLGNWAIQRQVYQG-UHFFFAOYSA-N [V+5].CC([O-])C=O.CC([O-])C=O.CC([O-])C=O.CC([O-])C=O.CC([O-])C=O Chemical compound [V+5].CC([O-])C=O.CC([O-])C=O.CC([O-])C=O.CC([O-])C=O.CC([O-])C=O SLGNWAIQRQVYQG-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
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- 230000036571 hydration Effects 0.000 description 2
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- 230000006872 improvement Effects 0.000 description 2
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- CRSOQBOWXPBRES-UHFFFAOYSA-N neopentane Chemical compound CC(C)(C)C CRSOQBOWXPBRES-UHFFFAOYSA-N 0.000 description 2
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Chemical compound O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000010653 organometallic reaction Methods 0.000 description 2
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- 238000012360 testing method Methods 0.000 description 2
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- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- POILWHVDKZOXJZ-ARJAWSKDSA-M (z)-4-oxopent-2-en-2-olate Chemical compound C\C([O-])=C\C(C)=O POILWHVDKZOXJZ-ARJAWSKDSA-M 0.000 description 1
- IUVCFHHAEHNCFT-INIZCTEOSA-N 2-[(1s)-1-[4-amino-3-(3-fluoro-4-propan-2-yloxyphenyl)pyrazolo[3,4-d]pyrimidin-1-yl]ethyl]-6-fluoro-3-(3-fluorophenyl)chromen-4-one Chemical compound C1=C(F)C(OC(C)C)=CC=C1C(C1=C(N)N=CN=C11)=NN1[C@@H](C)C1=C(C=2C=C(F)C=CC=2)C(=O)C2=CC(F)=CC=C2O1 IUVCFHHAEHNCFT-INIZCTEOSA-N 0.000 description 1
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 239000002841 Lewis acid Substances 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 1
- AONFIPYLIWZRMC-UHFFFAOYSA-N [Ta+3] Chemical compound [Ta+3] AONFIPYLIWZRMC-UHFFFAOYSA-N 0.000 description 1
- CUJRVFIICFDLGR-UHFFFAOYSA-N acetylacetonate Chemical compound CC(=O)[CH-]C(C)=O CUJRVFIICFDLGR-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 238000005865 alkene metathesis reaction Methods 0.000 description 1
- BVCZEBOGSOYJJT-UHFFFAOYSA-N ammonium carbamate Chemical compound [NH4+].NC([O-])=O BVCZEBOGSOYJJT-UHFFFAOYSA-N 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- VZTDIZULWFCMLS-UHFFFAOYSA-N ammonium formate Chemical compound [NH4+].[O-]C=O VZTDIZULWFCMLS-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- KXDHJXZQYSOELW-UHFFFAOYSA-N carbonic acid monoamide Natural products NC(O)=O KXDHJXZQYSOELW-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 238000003776 cleavage reaction Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
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- JBAKCAZIROEXGK-LNKPDPKZSA-N copper;(z)-4-hydroxypent-3-en-2-one Chemical compound [Cu].C\C(O)=C\C(C)=O JBAKCAZIROEXGK-LNKPDPKZSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- 238000005342 ion exchange Methods 0.000 description 1
- LZKLAOYSENRNKR-LNTINUHCSA-N iron;(z)-4-oxoniumylidenepent-2-en-2-olate Chemical compound [Fe].C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O LZKLAOYSENRNKR-LNTINUHCSA-N 0.000 description 1
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- 125000001827 mesitylenyl group Chemical group [H]C1=C(C(*)=C(C([H])=C1C([H])([H])[H])C([H])([H])[H])C([H])([H])[H] 0.000 description 1
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Classifications
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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
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- 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
- B01J23/20—Vanadium, niobium or tantalum
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
- B01J23/24—Chromium, molybdenum or tungsten
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/30—Tungsten
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- 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
- B01J23/38—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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- 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
- B01J23/38—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
- B01J23/6484—Niobium
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Definitions
- the present invention relates to the synthesis of ammonia selective catalytic reduction (NH 3 -SCR) catalysts for nitrogen oxides (NOx) reduction.
- NH 3 -SCR ammonia selective catalytic reduction
- Toxic NOx gases included in exhaust gases from fossil-fuel-powered vehicles or stationary sources such as power plants are required to be converted to N 2 before being released to the environment. This is normally done by using different types of NOx reduction catalysts such as three-way catalysts (TWO), NOx storage reduction (NSR), or selective catalytic reduction (SCR) using ammonia as external reducing agent (NH 3 -SCR).
- TWO three-way catalysts
- NSR NOx storage reduction
- SCR selective catalytic reduction
- NH 3 -SCR ammonia as external reducing agent
- Prior art catalysts have often used Cu, Fe, which are well recognized as good active sites for NH 3 -SCR when incorporated into zeolite materials.
- As regards support materials prior art has often used SiO 2 , which has high specific surface area, and may be expected to improve SCR performance by increasing the quantity of active sites.
- EP 2 985 077 Al describes Si O 2 -supported molybdenum or tungsten complexes, such as trialkyltungsten or molybdenum oxo complexes, their preparation and use in olefin metathesis.
- Rh 4 (CO) 12 The usual precursor of rhodium is Rh 4 (CO) 12 with a structure described as a tetrahedral array of four Rh atoms with nine terminal CO ligands and three bridging CO ligands. Isolated species of Rh(CO) 2 have been obtained from zerovalent [Rh 4 (CO) 12 ] cluster precursors on alumina (Chem. Rev. 2002, 102, 9, 3085-3128).
- the Surface Organometallic Chemistry (SOMC) approach is capable of modifying the surface of support materials by grafting organometallic precursors, i.e. forming chemical bonds between precursors and surface hydroxyl groups, and thus preserving the local structure of the grafted material to minimize the formation of diversified species on the surface of support materials that are normally created through conventional synthesis methods.
- This methodology can be used to synthesize metal oxide catalysts supported with different metals.
- a typical SOMC procedure to synthesize materials consists of 3 steps as follows:
- Step 2 Grafting o Allow metal precursors to react with surface hydroxyl groups of the support material in a solution, for example toluene, typically at room temperature ( ⁇ 25 °C) o Washing and drying
- Step 3 Activation o Remove remaining organic ligands, typically by calcination at around 500 °C or higher in 16 h under air flow
- the present invention discloses the development of new oxide NH 3 -SCR catalysts with improved NOx reduction performance by using new SOMC procedures.
- the present invention relates to a process for preparing a catalyst material, comprising the steps of:
- step (b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
- step (c) heating the material obtained in step (b), having a grafted metal element, in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
- step (d) regenerating surface hydroxyl (OH) groups on the material obtained in step (c);
- step (e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound containing a metal element different to the metal element of the first precursor compound; (f) heating the material obtained in step (e), having grafted metal elements from both the first and second precursor compounds, in an oxygen- containing atmosphere at a temperature of least 300°C, for at least 1 hour, so as to prepare a catalyst material, wherein one of the first and second precursor compounds is a compound (L) containing a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and the other precursor compound is a compound (R) containing a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt.
- the present invention relates to a process for preparing a catalyst material, comprising the steps of:
- step (b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
- step (c) heating the material obtained in step (b) having a grafted metal element in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
- step (d) regenerating surface hydroxyl (OH) groups on the heated material containing a grafted metal element obtained in step (c);
- step (e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound;
- step (f) heating the material obtained in step (e) in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour; wherein one of the first or second precursor compounds contains tungsten (W) and the other precursor compound contains vanadium (V) or niobium (Nb), and wherein the calcined catalyst material obtained by step (f) has at least 0.6 wt% and at most 1.4 wt% of tungsten (W), and either at least 0.8 wt% and at most 1.6 wt% of niobium (Nb) or at least 0.5 wt% and at most
- V vanadium
- the calcined catalyst material obtained by step (f) has at least 0.8 wt% and at most
- the calcined catalyst material obtained by step (f) has at least 0.9 wt% and at most 1.1 wt% of tungsten (W), and either at least 1.1 wt% and at most 1.3 wt% of niobium (Nb) or at least 0.7 wt% and at most 0.9 wt% of vanadium (V).
- the embodiments of the first aspect of the present invention thus provide processes for bimetallic grafting, on a support material which is ceria (CeO 2 ), zirconia (ZrO 2 ) or a combination thereof, of (i) a combination of a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt, or (ii) a combination of tungsten (W) with vanadium (V) or niobium (Nb).
- a support material which is ceria (CeO 2 ), zirconia (ZrO 2 ) or a combination thereof, of (i) a combination of a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt, or
- the present invention relates to a catalyst material as may be obtained by the processes set out above.
- the present invention relates to the use of the catalyst material set out above as an ammonia selective catalytic reduction (NH 3 -SCR) catalyst for nitrogen oxides (NOx) reduction.
- NH 3 -SCR ammonia selective catalytic reduction
- NOx nitrogen oxides
- the catalyst materials of the invention are of particular interest in providing improved NOx reduction performance in a low temperature range, notably 100°C to 250°C, particularly in the range of at least 130°C and at most 230°C.
- Figures 1 to 3 show NH 3 -SCR NOx reduction of catalysts synthesized by SOMC (Surface Organometallic Chemistry) processes, and specifically the performance of illustrative Nb-based hetero-dual site catalysts in comparison to an Nb-only catalyst, all on a ceria (CeO 2 ) support.
- the numbers (1.2 etc.) after metal elements in the legends identifying the catalysts giving rise to the different plotted curves indicate metal loading as a weight percentage.
- Figures 4 to 6 show NH 3 -SCR NOx reduction of catalysts synthesized by SOMC (Surface Organometallic Chemistry) processes, and specifically the performance of illustrative hetero-dual site catalysts in comparison to an Nb- only catalyst, all on a ceria (CeO 2 ) support.
- Figures 4 to 6 show, respectively, the performance of illustrative Nb-Rh, V-Rh and W-Rh hetero-dual site catalysts.
- Figure 7 shows DRIFT spectroscopy analysis spectra of a) ceria dehydroxylated at 200 °C (CeO 2-200 ) and b) after grafting of Rh 4 (CO) 12 .
- Figure 8 shows DRIFT spectra of a) grafting of Rh 4 (CO) 12 on ceria dehydroxylated at 200 °C, b) after thermal treatment at 250 °C under vacuum (10 5 Torr) and c) after calcination of the later at 400°C under dry air.
- Figure 9 shows physisorption isotherms of nitrogen at 77 K of the material containing 1 wt% of Rh on ceria after calcination under dry air at 400 °C for 16 h.
- Figure 10 shows DRIFT spectra of a) RhO x -CeO 2-200 material dehydroxylated at 200 °C, b) grafting of W( ⁇ C t Bu)(CH 2 t Bu) 3 on RhO x -CeO 2-200 , c) preparation of bimetallic Rh-W catalyst through calcination at 500 °C for 16h under dry air.
- Figure 11 shows physisorption isotherms of nitrogen at 77 K of the material containing 1 wt% of Rh and 0.98 wt% of W on ceria.
- a process of grafting (chemical reactions between precursors and surface) is used rather than impregnating.
- a support material selected from CeO 2 , ZrO 2 or their mixtures such as CeO 2 -ZrO 2 is used and is treated in such a way as to generate desired anchoring points (OH groups).
- the catalysts prepared in the first embodiment of the first aspect of the present invention comprise both (1) at least one metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W); and (2) at least one metal element selected from the group consisting of: Ru, Fe, Mn, Rh, Ir, Pd and Pt.
- the metal elements of types (1) and (2) are grafted in successive steps, with a fresh generation of OH-bearing support material between each grafting step.
- Figures 1, 2 and 3 show NOx transformation performance of catalysts containing two metals. After grafting with a Group 5 or Group 6 metal, in particular Nb, V or W, a second grafting is carried out using either a further Group 5 or Group 6 metal, or a separate transition metal. It appears that a separate loading of a further Group 5 or Group 6 metal may provide improved catalyst performance in certain temperature ranges, in a synergistic effect. Conversely, addition of Cu decreases activity compared to single metal catalysts i.e. ones only loaded with a Group 5 or Group 6 metal.
- ceria can be obtained from suppliers such as SOLVAY and typically has a specific surface area of about 250 m 2 /g.
- hydration of the oxide support material may be carried out in a first instance using moisture, followed by dehydroxylation through heating under reduced pressure.
- the solid support material may appropriately be put in close contact with a vapour pressure of water for ca. 10 min., a sufficient duration to allow a physical and chemical adsorption of water.
- the vapour pressure of water at 25°C is 16 Torr. In a generally appropriate way to proceed, one may allow sufficient time for the adsorption of an excess of water from a glass reactor on the surface of the support.
- the concentration of OH groups is notably influenced by the temperature of the treatment.
- a pressure of about 10 -5 mbar, at a temperature of 200 °C for typically 16 h constitute advantageous treatment conditions.
- Generally appropriate temperature ranges are from 150 °C to 550 °C, preferably from 200°C to 350°C, with a treatment time 4 h to 24 h preferably from 10 h to 16 h, with pressures 10 -3 mbar to 10 -6 mbar.
- the concentration of OH groups on the support material can for example be determined by chemical titration through reaction with AI( i Bu)3 - the latter reacts quantitatively with surface hydroxyl groups releasing one equivalent of isobutane per OH group.
- regeneration step (d) for the regeneration of appropriate ranges of OH groups on the support after the heating in step (c) to fix a first metal element, the conditions in terms of quantity of water added, temperature and pressure and duration, for adding moisture and heating under low pressure to dehydroxylate I produce a controlled quantity of OH groups, are generally the same as in step (a), and process conditions in final heating step (f) are generally the same as in heating step (c).
- the support material provided in step (a), and/or the support material obtained by regeneration in step (d) contain(s) at least 0.3 mmol and at most 2.0 mmol OH groups/g of the support material, and preferably at least 0.5 mmol and at most 1.3 mmol OH groups/g of the support material.
- Preferred support materials in the present invention are ceria (CeO 2 ) or ceria-zirconia (CeO 2 - ZrO 2 ) supports.
- the amount of ZrO 2 can be in the range 20-80 wt%, preferably between 30-60 wt%.
- a higher content of ZrO 2 may in practice decrease the concentration of OH groups.
- CeO 2 and CeO 2 -ZrO 2 are not known in the prior art as good support materials for SCR catalysts - these materials normally have lower specific surface area (SSA) than SiO 2 .
- solvents include apolar solvents, such as in particular hydrocarbon solvents.
- solvents include: pentane, hexane, heptane, toluene, xylenes, and mesitylene.
- temperatures may range from room temperature up to reflux conditions and the reaction time may appropriately be from 1 hour to 60 hours.
- the activation process may be carried out at temperatures from 400 °C - 700 °C, preferably between 300 °C and 600 °C. Calcination may appropriately be carried out in an oxygen-containing atmosphere, such as dry air.
- the compound (L) is:
- (B) a compound containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W).
- compound (R) is a compound having alkyl, aryl, alkenyl and/or carbonyl groups bound to the metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt.
- the compound (R) is selected from the group consisting of: Rh( ⁇ 3 -allyl) 3 ; Rh 4 (CO) 12 ; Fe(Mesityl) 2 ; Fe(CO) 5 ; Mn(CH 2 t Bu) 2 ; Me 5 CpPtMe 4 ; Pd(dba) 2 ; Pd(COD)(CH 2 SiMe 3 ) 2 ; CpPdMe; Pt(COD)Me 2 .
- the compound (R) contains rhodium (Rh) or iron (Fe), and/or the compound (L) contains one or more of: tungsten (W), niobium (Nb) and vanadium (V), most preferably tungsten (W).
- the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 9.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W). More preferably, the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 6.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element selected from the group consisting of: Ru, Mn, Fe, Rh, Ir, Pd and Pt.
- the first and second precursor compounds are:
- compound (B) a compound containing at least one hydrocarbon group bound though a carbon atom to V, Nb or W.
- Catalyst materials prepared in the present invention may be used as NH 3 -SCR catalysts. Hydrocarbons may also be envisaged as reductant instead of ammonia for NOx reduction.
- Catalyst materials of the present invention can interact with gas reactants in a catalytic process.
- the catalyst materials may be applied to an inert substrate such as a metal plate, corrugated metal plate, or honeycomb.
- the catalyst material may be combined with other solids such as fillers and binders in order to provide an extrudable paste that may be transformed into a porous structure such as a honeycomb.
- a catalytic converter based on catalyst materials of the present invention may appropriately include the catalyst material disposed on a supporting element such that passages are made available for the passage of exhaust gases, and the supported catalyst material may appropriately be housed in a metal casing.
- the metal casing is generally connected with one or more inlets such as pipes for transferring exhaust gases towards the catalyst material.
- the catalytic converter is appropriately connected with a source of ammonia in order for the latter to come into contact with exhaust gas.
- the ammonia can be provided as anhydrous ammonia, aqueous ammonia, urea, ammonium carbonate, ammonium formate, or ammonium carbamate.
- an ammonia storage tank is used to contain the ammonia source.
- An SCR system can be integrated into various systems that require NOx reduction.
- Applications include engine systems of a passenger vehicle, truck, utility boiler, industrial boiler, solid waste boiler, ship, locomotive, tunnel boring machine, submarine, construction equipment, gas turbine, power plant, airplane, lawnmower, or chainsaw.
- Catalytic reduction of NOx using catalyst materials according to the present invention is therefore of general interest in situations where fossil fuels are used for power generation, not just for transportation but also in power generation devices, and domestic appliances using fossil fuels.
- Catalysts according to the present invention may be notably used in vehicles partially powered by electric engines.
- Peaks at 2082 and 2008 cm -1 are attributable to symmetric and to asymmetric geminal dicarbonyl species [Rh-(CO) 2 ] respectively.
- the signal at 2059 cm -1 can be assigned to linear CO species and the band at 1918 cm -1 is presumably due to the bridged CO species.
- Scheme 2 Schematic representation of surface organometallic species Rh 4 (CO) 12 ]- CeO 2-(200) (a) °C evolution with the different treatments by pyrolysis under vacuum at 250°C (b) and calcination at 400°C under dry synthetic air
- the BET surface area measured for the resulting material was found to be ca. 176 ⁇ 9 m 2 /g, close to the one found for the neat ceria calcined under the same conditions, which was ca. 200 ⁇ 10 m 2 /g. This would mean that the crystal structure of ceria support is preserved and the grafting as well as the calcination process induce no particle sintering.
- the material ⁇ RhOx ⁇ -CeO 2 obtained in the first step was rehydrated by addition of vapor pressure of water.
- the sample was heated at 100 °C for 6 h in the presence of the moisture. Afterwards, the material was dehydroxylated under high vacuum (10 - 5 Torr) at 200 °C, and the excess as well as the physisorbed water were removed.
- Example A2-a Grafting of [W( ⁇ C t Bu)(CH 2 t Bu) 3 ]-onRhOx-CeO2
- the new bands appearing in the 3100-2850 cm -1 and 1620-1400 cm -1 ranges are characteristic of aliphatic v(C-H), and ⁇ (C-H) vibrations of the perhydrocarbyl ligands coordinated to surface tungsten.
- Example A2-c Grafting of [W(O)(O t Bu) 4 ] on RhOx-CeO 2 through SOMC approach : (WOx-RhOx/CeO 2 ) (Rh 1.0; W 2.0)
- Example A2-d Grafting of rw( C t BuHCH2 t Bu l on RhOx-CeO 2 - ZrO 2 through SOMC approach : (WOx-RhOx/CeO 2 -ZrO 2(200) )(Rh 1.0; W 2)
- Example A2-e Grafting of [V(O)(OEt) 3 ] on RhOx-CeO 2 through SOMC approach : (VOx-RhOx/CeO 2 ) (Rh 1.0; V 2.0)
- the material obtained in the first step was calcined at 400°C and rehydrated by addition of vapor pressure of water.
- the sample was heated at 100 °C for 6 h in the presence of the moisture.
- the material was dehydroxylated under high vacuum (10 - 5 Torr) at 200 °C, and the excess as well as the physisorbed water were removed leading to WO x -CeO 2-200 .
- Similar experiments were carried out for the preparation of the catalysts W0x/Ce02 with different loading (0.87, 1.74, 2, 3.7).
- Example B2-a Preparation of WOx-VOx/CeO 2 through SOMC approach: WOx-VOx/CeO 2 (W 1.0, V 0.8)
- Example B2-b Preparation of WOx-FeOx/CeO 2 through SOMC approach: WOx-FeOx/CeO 2 (W 1.0, Fe 0.6)
- Example B2-c Preparation of WOx-NbOx/CeO 2 through SOMC approach: WOx-NbOx/CeO 2 (W 1.0; Nb 1.2)
- the material obtained in the first step was calcined at 500°C and rehydrated by addition of vapor pressure of water.
- the sample was heated at 100 °C for 6 h in the presence of the moisture.
- the material was dehydroxylated under high vacuum (10 - 5 Torr) at 150 °C, and the excess as well as the physisorbed water were removed leading to VO x -CeO 2-200 (V 0.8).
- Example C2-a Preparation of VOx-FeOx/CeO 2 through SOMC approach: VOx-FeOx/CeO 2 (v 0.8; Fe 0.5)
- Example C2-b (Comparative): Preparation of VOx-CuOx/CeO 2 through SOMC approach: VOx-CuOx/CeO 2 (V 0.8; Cu 0.4)
- CeO 2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10 - 5 Torr).
- the material obtained in the first step was calcined at 500°C and rehydrated by addition of vapor pressure of water.
- the sample was heated at 100 °C for 6 h in the presence of the moisture.
- the material was dehydroxylated under high vacuum (10 - 5 Torr) at 150 °C, and the excess as well as the physisorbed water were removed leading to NbOx-CeO 2- 200 (Nb 1.2).
- Example D2-a Preparation of NbOx-FeOx/CeO 2 through SOMC approach: NbOx-FeOx/CeO 2 (Nb 1.2; Fe 0.6)
- CeO 2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10 - 5 Torr).
- NbOx/CeO 2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10 - 5 Torr).
- Pellet samples of approximately 33 mg were prepared under 1 ton pressure and put into a quartz reactor (diameter 4.5mm). A mixture of gas consisting of NO 300ppm, NH 3 , 350ppm, O 2 10%, H2O, 3%, CO 2 10%, He (balance), was sent through a catalytic bed at the rate of 300 mL/min. The reactor was heated from room temperature to 600°C with a heating rate of 10 °C/ min. The system was kept at 600°C for 10 min before cooling down to room temperature. Gas composition at the outlet was monitored during the heating up and cooling down by a combination of FTIR and GC-MS.
Abstract
The present invention relates to processes for bimetallic grafting, on a support material which is ceria (CeO2), zirconia (ZrO2) or a combination thereof, of (i) a combination of a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt, or (ii) a combination of tungsten (W) with vanadium (V) or niobium (Nb). The present invention further relates to catalyst materials as may be obtained by such processes, and to the use of such catalyst materials as an ammonia selective catalytic reduction (NH3-SCR) catalyst for nitrogen oxides (NOx) reduction. The catalyst materials of the invention are of particular interest in providing improved NOx reduction performance in a low temperature range, notably 100°C to 250°C, particularly in the range of at least 130°C and at most 230°C.
Description
METAL SUPPORTED OXIDE NH3-SCR CATALYSTS HAVING HETERO-DUAL SITES AND SYNTHESIS PROCESSES
Field of the Invention
[0001] The present invention relates to the synthesis of ammonia selective catalytic reduction (NH3-SCR) catalysts for nitrogen oxides (NOx) reduction.
Background Art
[0002] Toxic NOx gases (NO, NO2, N2O) included in exhaust gases from fossil-fuel-powered vehicles or stationary sources such as power plants are required to be converted to N2 before being released to the environment. This is normally done by using different types of NOx reduction catalysts such as three-way catalysts (TWO), NOx storage reduction (NSR), or selective catalytic reduction (SCR) using ammonia as external reducing agent (NH3-SCR).
[0003] Metal oxides such as V2O5 are known to be good NH3-SCR catalysts. It has been suggested that the catalytic activity is achieved by the complementary features of acidity and reducibility of the surface species. Briefly, NH3 is adsorbed on a Brpnsted acid site (V5+-OH) followed by N-H activation through the adjacent V=O surface groups through a redox cycle (V5+=O/V4+-OH). The resulting surface complex reacts with gaseous or weakly adsorbed NO through Langmuir-Hinshelwood and Eley-Rideal mechanisms, respectively, to form NH2NO intermediate species which undergo decomposition into N2 and H2O. An alternate mechanism (amide-nitrosamide) involving the adsorption of NH3 over Lewis acid sites has also been proposed. Furthermore, under realistic conditions, particularly when a peroxidation catalytic convertor is placed upstream of the SCR catalytic convertor, this gives rise to formation of nitrogen dioxide which favors the SCR reaction known as fast-SCR. Indeed, NO2 allows fast re-oxidation of the reduced species. However, the optimal NO2/NO ratio is one, and the presence of excess NO2 is also reduced through slower
reaction leading to a lower total SCR reaction rate. Metal oxide catalysts such as V2O5 are developed mostly by synthesis routes such as impregnation, which normally produce nanoparticles of metal dispersed on support. The problem of such catalysts is the low performance, such as low NOx conversion and/or low N2 selectivity.
[0004] Prior art catalysts have often used Cu, Fe, which are well recognized as good active sites for NH3-SCR when incorporated into zeolite materials. As regards support materials, prior art has often used SiO2, which has high specific surface area, and may be expected to improve SCR performance by increasing the quantity of active sites.
US 9,283,548 B2 discloses catalysts of the type: MA I CeO2 (M = Fe, Cu; A = K, Na), the synthesis route being impregnation, with chelating agents such as EDTA, DTPA being used.
J. Phys. Chem. B 2006, 110, 9593 - 9600 [Tian2006] discloses catalysts of the type: VOx I AO2 (A = Ce, Si, Z), the synthesis route being impregnation. Applications include propane oxidative dehydrogenation (ODH). Dispersion and physisorption of the vanadium oxo-isopropoxide is achieved, rather than chemisorption.
J. Phys. Chem. B 1999, 103, 6015 - 6024 [Burchaml999] discloses catalysts of the type: Nb2O5 1 SiO2, AI2O3, ZrO2, TiO2, the synthesis route being impregnation. The reference discusses surface species of isolated Nb, characterized by vibrational spectroscopy. The preparation is carried out in water, and the metal is deposited on the surface, rather than being grafted by protonolysis.
J. Phys. Chem. C 2011, 115, 25368-25378 [Wu2011] discloses catalysts of the type:VOx I CeO2, SiO2, ZrO2, the synthesis route being impregnation. Iso-propanol is used as a solvent, not leading to grafting of the precursor on the surface, but instead only dispersion and physisorption of the vanadium oxo- isopropoxide.
Appl. Catal. B 62, 2006, 369 [Chmielarz 2006] describes catalysts of the type: Fe or Cu/SiO2 (3 different forms). It is widely known that Cu and Fe show good NH3-SCR performance when zeolites are used (ion-exchange synthesis). The catalyst materials were used for deNOx by NH3-SCR. Synthesis was carried out by molecular designed dispersion (MDD) using precursors Fe(acac)3, Cu(acac)(acac = acetylacetonate).
Science 2007, 317, 1056-1060 [Avenier 2007] describes cleavage of dinitrogen on isolated silica surface-supported tantalum(III) and tantalum(V) hydride centers
EP 2 985 077 Al describes Si O2-supported molybdenum or tungsten complexes, such as trialkyltungsten or molybdenum oxo complexes, their preparation and use in olefin metathesis.
[0005] The use of noble metals (platinum, Pt, palladium, Pd, rhodium, Rh) in catalytic convertors to promote the reactions and clean up the exhaust gas, has known for many years, largely used in a Three- Way-Catalyst (TWC). In addition to the metal components of modern TWCs, a complex mixture of precious-metal particles (Rh, Pt, Pd) and various oxide materials are included in the catalyst's formulation. Rhodium is included in the formulation of TWC for its superior capacity to catalyse the reduction of NO in reducing atmosphere- containing unused hydrocarbons. The usual precursor of rhodium is Rh4(CO)12 with a structure described as a tetrahedral array of four Rh atoms with nine terminal CO ligands and three bridging CO ligands. Isolated species of Rh(CO)2 have been obtained from zerovalent [Rh4(CO)12] cluster precursors on alumina (Chem. Rev. 2002, 102, 9, 3085-3128).
Summary of the Invention
[0006] In order to address the problems associated with prior art products and processes in the field of ammonia selective catalytic reduction (NH3-SCR) catalysts for nitrogen oxides (NOx) reduction, the processes and
products of the present invention have been developed. Combinations of transition metal loading of ceria and zirconia oxides have been optimized in terms of catalytic performance. In particular, among catalyst materials of the present invention are ones showing improved low temperature performance. Indeed, in the field of exhaust gas catalysis in conventional fuel-powered cars, the so-called cold-start period (immediately after the engine starts) is known to be a problem for catalytic performance. During this period, the temperature ranges from room temperature to about 250°C, where catalytic reactions are more generally activated. In cars with a hybrid chassis, i.e. partially powered by an electric engine, the average temperature of exhaust gas is even lower, making the issue of low-temperature catalyst performance more critical. It is therefore of particular interest to provide new catalysts with improved NOx reduction performance in a low temperature range, such as 100°C to 250°C, to address this issue.
[0007] The Surface Organometallic Chemistry (SOMC) approach is capable of modifying the surface of support materials by grafting organometallic precursors, i.e. forming chemical bonds between precursors and surface hydroxyl groups, and thus preserving the local structure of the grafted material to minimize the formation of diversified species on the surface of support materials that are normally created through conventional synthesis methods. This methodology can be used to synthesize metal oxide catalysts supported with different metals. A typical SOMC procedure to synthesize materials consists of 3 steps as follows:
• Step 1: Preparation, example: o Support materials:
■ calcination
■ hydration
■ dehydroxylation to generate controlled concentrations of hydroxyl groups
o Metal precursors:
■ Synthesis (for those that are not readily available)
• Step 2: Grafting o Allow metal precursors to react with surface hydroxyl groups of the support material in a solution, for example toluene, typically at room temperature (~ 25 °C) o Washing and drying
• Step 3: Activation o Remove remaining organic ligands, typically by calcination at around 500 °C or higher in 16 h under air flow
[0008] The present invention discloses the development of new oxide NH3-SCR catalysts with improved NOx reduction performance by using new SOMC procedures.
[0009] Thus, in a first embodiment of a first aspect, the present invention relates to a process for preparing a catalyst material, comprising the steps of:
(a) providing a support material having surface hydroxyl (OH) groups, wherein the support material is ceria (CeO2), zirconia (ZrO2) or a combination thereof;
(b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
(c) heating the material obtained in step (b), having a grafted metal element, in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
(d) regenerating surface hydroxyl (OH) groups on the material obtained in step (c);
(e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound containing a metal element different to the metal element of the first precursor compound;
(f) heating the material obtained in step (e), having grafted metal elements from both the first and second precursor compounds, in an oxygen- containing atmosphere at a temperature of least 300°C, for at least 1 hour, so as to prepare a catalyst material, wherein one of the first and second precursor compounds is a compound (L) containing a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and the other precursor compound is a compound (R) containing a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt.
[0010] In a second embodiment of the first aspect, the present invention relates to a process for preparing a catalyst material, comprising the steps of:
(a) providing a support material having surface hydroxyl (OH) groups, wherein the support material is ceria (CeO2), zirconia (ZrO2) or a combination thereof;
(b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
(c) heating the material obtained in step (b) having a grafted metal element in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
(d) regenerating surface hydroxyl (OH) groups on the heated material containing a grafted metal element obtained in step (c);
(e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound;
(f) heating the material obtained in step (e) in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour; wherein one of the first or second precursor compounds contains tungsten (W) and the other precursor compound contains vanadium (V) or niobium (Nb), and wherein the calcined catalyst material obtained by step (f) has at least 0.6 wt% and at most 1.4 wt% of tungsten (W), and either at least
0.8 wt% and at most 1.6 wt% of niobium (Nb) or at least 0.5 wt% and at most
1.1 wt% of vanadium (V).
[0011] Preferably, in the second embodiment of the first aspect, the calcined catalyst material obtained by step (f) has at least 0.8 wt% and at most
1.2 wt% of tungsten (W), and either at least 1.0 wt% and at most 1.4 wt% of niobium (Nb) or at least 0.6 wt% and at most 1.0 wt% of vanadium (V). More preferably, the calcined catalyst material obtained by step (f) has at least 0.9 wt% and at most 1.1 wt% of tungsten (W), and either at least 1.1 wt% and at most 1.3 wt% of niobium (Nb) or at least 0.7 wt% and at most 0.9 wt% of vanadium (V).
[0012] The embodiments of the first aspect of the present invention thus provide processes for bimetallic grafting, on a support material which is ceria (CeO2), zirconia (ZrO2) or a combination thereof, of (i) a combination of a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt, or (ii) a combination of tungsten (W) with vanadium (V) or niobium (Nb).
[0013] In a second aspect, the present invention relates to a catalyst material as may be obtained by the processes set out above.
[0014] In a third aspect, the present invention relates to the use of the catalyst material set out above as an ammonia selective catalytic reduction (NH3-SCR) catalyst for nitrogen oxides (NOx) reduction. As mentioned above, the catalyst materials of the invention are of particular interest in providing improved NOx reduction performance in a low temperature range, notably 100°C to 250°C, particularly in the range of at least 130°C and at most 230°C.
Brief description of the Figures
[0015] Figures 1 to 3 show NH3-SCR NOx reduction of catalysts synthesized by SOMC (Surface Organometallic Chemistry) processes, and specifically the performance of illustrative Nb-based hetero-dual site catalysts in
comparison to an Nb-only catalyst, all on a ceria (CeO2) support. The numbers (1.2 etc.) after metal elements in the legends identifying the catalysts giving rise to the different plotted curves indicate metal loading as a weight percentage.
Figures 4 to 6 show NH3-SCR NOx reduction of catalysts synthesized by SOMC (Surface Organometallic Chemistry) processes, and specifically the performance of illustrative hetero-dual site catalysts in comparison to an Nb- only catalyst, all on a ceria (CeO2) support. Figures 4 to 6 show, respectively, the performance of illustrative Nb-Rh, V-Rh and W-Rh hetero-dual site catalysts.
Figure 7 shows DRIFT spectroscopy analysis spectra of a) ceria dehydroxylated at 200 °C (CeO2-200) and b) after grafting of Rh4(CO)12.
Figure 8 shows DRIFT spectra of a) grafting of Rh4(CO)12 on ceria dehydroxylated at 200 °C, b) after thermal treatment at 250 °C under vacuum (10 5 Torr) and c) after calcination of the later at 400°C under dry air.
Figure 9 shows physisorption isotherms of nitrogen at 77 K of the material containing 1 wt% of Rh on ceria after calcination under dry air at 400 °C for 16 h.
Figure 10 shows DRIFT spectra of a) RhOx-CeO2-200 material dehydroxylated at 200 °C, b) grafting of W(ΞCtBu)(CH2 tBu)3 on RhOx-CeO2-200, c) preparation of bimetallic Rh-W catalyst through calcination at 500 °C for 16h under dry air.
Figure 11 shows physisorption isotherms of nitrogen at 77 K of the material containing 1 wt% of Rh and 0.98 wt% of W on ceria.
Detailed description of the invention
[0016] In the present invention, a process of grafting (chemical reactions between precursors and surface) is used rather than impregnating. A support material selected from CeO2, ZrO2 or their mixtures such as CeO2-ZrO2
is used and is treated in such a way as to generate desired anchoring points (OH groups).
[0017] The catalysts prepared in the first embodiment of the first aspect of the present invention comprise both (1) at least one metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W); and (2) at least one metal element selected from the group consisting of: Ru, Fe, Mn, Rh, Ir, Pd and Pt.
[0018] In practice, the metal elements of types (1) and (2) are grafted in successive steps, with a fresh generation of OH-bearing support material between each grafting step.
[0019] Figures 1, 2 and 3 show NOx transformation performance of catalysts containing two metals. After grafting with a Group 5 or Group 6 metal, in particular Nb, V or W, a second grafting is carried out using either a further Group 5 or Group 6 metal, or a separate transition metal. It appears that a separate loading of a further Group 5 or Group 6 metal may provide improved catalyst performance in certain temperature ranges, in a synergistic effect. Conversely, addition of Cu decreases activity compared to single metal catalysts i.e. ones only loaded with a Group 5 or Group 6 metal.
[0020] Of particular interest in the present invention is an improvement in low-temperature catalyst performance, which was not observed to be obtainable through mixtures of Group 5 and 6 metals, or mixtures of Group 5 and 6 metals with Cu. It was observed that catalysts containing 1.0 wt% of W and 0.8 wt of V show higher NOx reduction than reference catalysts in the range 150 to 200°C, but in fact show improvements over a much broader temperature range. Without wishing to be bound by any particular theory, it is postulated that the effect observed may result from an increase in the number of active sites rather than a special effect such as a change in chemical mechanism.
[0021] In the framework of the present invention, comparisons of catalytic performance were made between samples with only Nb metal loaded
on the support (1.8 wt%, or 3.4 wt% by grafting two times), Rh (1 wt%) alone, and Nb in combination with Rh. Improved NOx reduction in the (low) temperature range of 130 to 230°C was investigated. The use of a high Nb loading shows improved performance at high temperature but actually reduced performance at low temperature (compared to a lower loading of Nb alone). Similar effects were observed experimentally with V or W instead of Nb as Group 5/6 metal. The combination of both a Group 5/6 metal atom and a metal element such as Rh therefore appears to create a special synergistic effect as regards low temperature catalytic performance.
[0022] Appropriate support materials in the form of ceria (CeO2) and/or zirconia (ZrO2) can be obtained from commercial suppliers. For example, ceria can be obtained from suppliers such as SOLVAY and typically has a specific surface area of about 250 m2/g.
[0023] In an advantageous embodiment to provide a certain controlled concentration of OH groups on the support material, in order to provide the material in step (a) of the process of the invention, hydration of the oxide support material (as received in a typical commercial sample) may be carried out in a first instance using moisture, followed by dehydroxylation through heating under reduced pressure. For this step the solid support material may appropriately be put in close contact with a vapour pressure of water for ca. 10 min., a sufficient duration to allow a physical and chemical adsorption of water. The vapour pressure of water at 25°C is 16 Torr. In a generally appropriate way to proceed, one may allow sufficient time for the adsorption of an excess of water from a glass reactor on the surface of the support.
[0024] The concentration of OH groups is notably influenced by the temperature of the treatment. In a generally appropriate process for treating a ceria (CeO2) support material, a pressure of about 10-5 mbar, at a temperature of 200 °C for typically 16 h, constitute advantageous treatment conditions. Generally appropriate temperature ranges are from 150 °C to 550 °C,
preferably from 200°C to 350°C, with a treatment time 4 h to 24 h preferably from 10 h to 16 h, with pressures 10-3 mbar to 10-6 mbar. The concentration of OH groups on the support material can for example be determined by chemical titration through reaction with AI(iBu)3 - the latter reacts quantitatively with surface hydroxyl groups releasing one equivalent of isobutane per OH group.
[0025] In regeneration step (d), for the regeneration of appropriate ranges of OH groups on the support after the heating in step (c) to fix a first metal element, the conditions in terms of quantity of water added, temperature and pressure and duration, for adding moisture and heating under low pressure to dehydroxylate I produce a controlled quantity of OH groups, are generally the same as in step (a), and process conditions in final heating step (f) are generally the same as in heating step (c). Thus, in the processes according to the invention, the support material provided in step (a), and/or the support material obtained by regeneration in step (d), contain(s) at least 0.3 mmol and at most 2.0 mmol OH groups/g of the support material, and preferably at least 0.5 mmol and at most 1.3 mmol OH groups/g of the support material.
[0026] Preferred support materials in the present invention are ceria (CeO2) or ceria-zirconia (CeO2 - ZrO2) supports. Concerning the mixed ceria- zirconia (CeO2 - ZrO2) support, the amount of ZrO2 can be in the range 20-80 wt%, preferably between 30-60 wt%. A higher content of ZrO2 may in practice decrease the concentration of OH groups. CeO2 and CeO2-ZrO2 are not known in the prior art as good support materials for SCR catalysts - these materials normally have lower specific surface area (SSA) than SiO2.
[0027] Concerning the functionalization (grafting) stages, constituted by steps (b) and (e) of the processes of the first or second embodiment of the first aspect of the present invention, generally appropriate solvents include apolar solvents, such as in particular hydrocarbon solvents. Specific example of solvents include: pentane, hexane, heptane, toluene, xylenes, and mesitylene. In terms of reaction conditions for grating, temperatures may range from room
temperature up to reflux conditions and the reaction time may appropriately be from 1 hour to 60 hours.
[0028] Concerning the activation (calcination) stages, constituted by steps (c) and (f) of the processes of the first or second embodiment of the first aspect of the present invention, the activation process may be carried out at temperatures from 400 °C - 700 °C, preferably between 300 °C and 600 °C. Calcination may appropriately be carried out in an oxygen-containing atmosphere, such as dry air.
[0029] In preferred processes according to the first embodiment of the first aspect of the present invention, the compound (L) is:
(A) a compound containing at least one alkoxy or phenoxy group bound though its oxygen atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W); or
(B) a compound containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W).
[0030] In preferred embodiments, compound (A) containing at least one alkoxy or phenoxy group bound though its oxygen atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W) is at least one compound selected from the group consisting of: [Nb(OEt)5]2; Nb(OAr)5 where Ar is the 1, 3, 5-tri methylphenyl (CH3)3C6H2- group; [W=O(OEt)4]2; [W(0)(0tBu)4]; [W2(OtBU)6]; [V(=O)(OEt)3]2; [V(=O)(OiPr)3]; and [Ta(OEt)5]2.
[0031] In preferred embodiments, compound (B) containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W) is at least one compound selected from the group consisting of: W(=NR)(=CHtBu)2(CH2tBu)2 (R = alkyl or aryl); W(=O)(CH2 tBu)3CI; W(ΞCtBu)(CH2 tBu)3; [(tBuCH2)3W]O;
[(tBuCH2)3W=O]2(μ-O); [tBuO3W=O]2(μ-O); (tBuO)3WΞW(tBuO)3;
Mo(=O)(CH2 tBu)3CI; Mo(O)2Mesityl2; V(=O)Mes3; V(=O)CH2SiMe3; Ta(=CHtBu)(CH2 tBu)3.
[0032] In preferred embodiments, compound (R) is a compound having alkyl, aryl, alkenyl and/or carbonyl groups bound to the metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt. Preferably, the compound (R) is selected from the group consisting of: Rh(η 3-allyl)3; Rh4(CO)12; Fe(Mesityl)2; Fe(CO)5; Mn(CH2 tBu)2; Me5CpPtMe4; Pd(dba)2; Pd(COD)(CH2SiMe3)2; CpPdMe; Pt(COD)Me2.
[0033] In particularly preferred embodiments of processes according to the first embodiment of the first aspect of the present invention, the compound (R) contains rhodium (Rh) or iron (Fe), and/or the compound (L) contains one or more of: tungsten (W), niobium (Nb) and vanadium (V), most preferably tungsten (W).
[0034] In particularly preferred embodiments of processes according to the first embodiment of the first aspect of the present invention, the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 9.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W). More preferably, the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 6.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element selected from the group consisting of: Ru, Mn, Fe, Rh, Ir, Pd and Pt.
[0035] In preferred processes according to the second embodiment of the first aspect of the present invention, the first and second precursor compounds are:
(A) a compound containing at least one alkoxy or phenoxy group bound though its oxygen atom to V, Nb or W; or
(B) a compound containing at least one hydrocarbon group bound though a carbon atom to V, Nb or W.
[0036] In particularly preferred processes according to the second embodiment of the first aspect of the present invention, compound (A) containing at least one alkoxy or phenoxy group bound though its oxygen atom to V, Nb or W is at least one compound selected from the group consisting of: [Nb(OEt)5]2; Nb(OAr)5 where Ar is the 1,3,5-trimethylphenyl (CH3)3C6H2- group; [W=O(OEt)4]2; [W(O)(OtBu)4]; [W2(OtBu)6]; [V(=O)(OEt)3]2; and
[V(=O)(O'Pr)3]. In particularly preferred processes according to the second embodiment of the first aspect of the present invention, compound (B) containing at least one hydrocarbon group bound though a carbon atom to V, Nb or W is at least one compound selected from the group consisting of: W(=NR)(=CHtBu)2(CH2 tBu)2 (R = alkyl or aryl); W(=O)(CH2 tBu)3CI; W(ΞCtBu)(CH2 tBu)3; [(tBuCH2)3W]O; [(tBuCH2)3W=O]2(μ-O);
[tBuO3W=O]2(μ-O); (tBuO)3WΞW(tBuO)3; V(=O)Mes3; V(=O)CH2SiMe3.
[0037] Catalyst materials prepared in the present invention may be used as NH3-SCR catalysts. Hydrocarbons may also be envisaged as reductant instead of ammonia for NOx reduction.
[0038] Catalyst materials of the present invention can interact with gas reactants in a catalytic process. In certain embodiments the catalyst materials may be applied to an inert substrate such as a metal plate, corrugated metal plate, or honeycomb. Alternatively, the catalyst material may be combined with other solids such as fillers and binders in order to provide an extrudable paste that may be transformed into a porous structure such as a honeycomb.
[0039] A catalytic converter based on catalyst materials of the present invention may appropriately include the catalyst material disposed on a supporting element such that passages are made available for the passage of exhaust gases, and the supported catalyst material may appropriately be housed in a metal casing. The metal casing is generally connected with one or more inlets such as pipes for transferring exhaust gases towards the catalyst material.
[0040] In order to function in NH3-SCR catalysis, the catalytic converter is appropriately connected with a source of ammonia in order for the latter to come into contact with exhaust gas. The ammonia can be provided as anhydrous ammonia, aqueous ammonia, urea, ammonium carbonate, ammonium formate, or ammonium carbamate. In some embodiments, an ammonia storage tank is used to contain the ammonia source.
[0041] An SCR system can be integrated into various systems that require NOx reduction. Applications include engine systems of a passenger vehicle, truck, utility boiler, industrial boiler, solid waste boiler, ship, locomotive, tunnel boring machine, submarine, construction equipment, gas turbine, power plant, airplane, lawnmower, or chainsaw. Catalytic reduction of NOx using catalyst materials according to the present invention is therefore of general interest in situations where fossil fuels are used for power generation, not just for transportation but also in power generation devices, and domestic appliances using fossil fuels. Catalysts according to the present invention may be notably used in vehicles partially powered by electric engines.
[0042] Within the practice of the present invention, it may be envisaged to combine any features or embodiments which have hereinabove been separately set out and indicated to be advantageous, preferable, appropriate or otherwise generally applicable in the practice of the invention. The present description should be considered to include all such combinations of features or embodiments described herein unless such combinations are said herein to be mutually exclusive or are clearly understood in context to be mutually exclusive.
Experimental section - Examples
[0043] The following experimental section illustrates experimentally the practice of the present invention, but the scope of the invention is not to be considered to be limited to the specific examples that follow.
Part A: Preparation of bimetallic RhOx/MOx/CeO2 catalysts through SOMC approach(M =W, V ,Nb)
Preparation Example A1: First step - Preparation of RhOx/CeO2 through SOMC approach
[0044] A mixture CeO2(200) (6 g) and a desired amount of tetrarhodium dodecacarbonyl as a dark-red crystalline solid (109 mg to reach ca. 1 wt% of Rh) was stirred at 25 °C in toluene (20 ml) for 12 h. After filtration, the solid [Rh4(CO)12]-CeO2-(200) was heated at 60 °C under vacuum (10-5 mbar) in order to remove the unused complex and to promote the formation of isolated Rh/ CeO2 species. In a second variant, this catalyst was prepared via CVD [Rh4(CO)12] (a solid/solid phase reaction - Scheme 1). Thus a mixture of [Rh4(CO)12] (37 mg, 0.05 mmol) and CeO2-200 (1 g) was stirred at 25 °C for 12 h. Then the unreacted Rh4(CO)12 was removed through sublimation at 60 °C under vacuum ( 10- 5 Torr).
Scheme 1 : Surface organometallic reaction of Rh4(CO)12 with surface hydroxides of CeO2 dehydroxylated at 200 °C
[0045] The grafting reaction of Rh4(CO)12 on ceria to form [Rh4(CO)12]- CeO2-(200) is monitored by DRIFT spectroscopy (Figure 7). After the grafting reaction and the removal of the excess complex, the bands between 3400 and 3700 cm -1 attributed to different vibration mode of v(CeO-H) were disturbed. The band at 3747 cm -1 completely disappeared, and others were shifted. New bands in the 2100-1900 cm -1 range were observed - these peaks are characteristic of CO stretching vibrations of the chemisorbed ligands on the surface. Peaks at 2082 and 2008 cm -1 are attributable to symmetric and to asymmetric geminal dicarbonyl species [Rh-(CO)2] respectively. The signal at 2059 cm -1 can be assigned to linear CO species and the band at 1918 cm -1 is presumably due to the bridged CO species.
Scheme 2: Schematic representation of surface organometallic species Rh4(CO)12]- CeO2-(200) (a) °C evolution with the different treatments by pyrolysis under vacuum at 250°C (b) and calcination at 400°C under dry synthetic air
[0046] Pyrolysis of [Rh4(CO)12]-CeO2-(200) material at 250 °C under vacuum resulted in the removal of the carbonyl ligands as confirmed by disappearance of the bands in the region between 1900 and 2100 cm -1 in DRIFT spectrum shown in Figure 8-b, characteristic of v(CO) vibrations. The brown sample becomes black suggesting the formation of Rh nanoparticles on the ceria support.
[0047] After calcination at 400 °C under dry air (15 h) (Figure 8 c), bands between 3400 and 3700 cm -1 attributed to different vibration mode of v(CeO-H) are observed - this portion of hydroxyl groups can be further functionalized by other organometallic to yield heterobimetallic catalyst on CeO2 support.
[0048] The BET surface area measured for the resulting material was found to be ca. 176 ± 9 m2/g, close to the one found for the neat ceria calcined under the same conditions, which was ca. 200 ± 10 m2/g. This would mean that the crystal structure of ceria support is preserved and the grafting as well as the calcination process induce no particle sintering.
[0049] In addition to creating an additional anchoring site, the material {RhOx}-CeO2 obtained in the first step (Schemes 1 and 2) was rehydrated by addition of vapor pressure of water. The sample was heated at 100 °C for 6 h in the presence of the moisture. Afterwards, the material was dehydroxylated under high vacuum (10- 5 Torr) at 200 °C, and the excess as well as the physisorbed water were removed.
Example A2-a: Grafting of [W(ΞCtBu)(CH2 tBu)3]-onRhOx-CeO2
Through SOMC approach ;(WOx-RhOx/CeO2)(Rh1.0;W2.5)
[0050] A mixture of W(ΞCtBu)(CH2 tBu)3 (193 mg) and RhOx-CeO2-200
(2 g) was stirred in toluene for 4 h, at room temperature. The W(Ξ CtBu)(CH2 tBu)3/RhOx-CeO2-200 material was washed three times with pentane via filtration-condensation cycles. Then, all volatiles were condensed into a 6 L vessel in order to quantify neopentane evolved during the grafting reaction. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
Scheme 3: Surface organometallic reaction of W(ΞCtBu)(CH2 tBu)3 on RhOx-CeO2-200 and preparation of bimetallic Rh-W catalyst through subsequent calcination
[0052] As shown in Figure 10, after surface functionalization of the ceria surface by W(ΞCtBu)(CH2 tBu)3 , the bands between 3500 and 3700 cm -1 attributed to different vibration modes of surface v(O-H) are disturbed. Indeed, the DRIFT spectrum of the resulting material (Figure 10 b) shows a partial consumption of the other OH vibration bands, located between 3700 and 3600 cm -1, while a new broad band appears, resulting from the interaction of some OH groups with tungsten alkyl ligands. The new bands appearing in the 3100-2850 cm -1 and 1620-1400 cm -1 ranges are characteristic of aliphatic v(C-H), and δ(C-H) vibrations of the perhydrocarbyl ligands coordinated to surface tungsten.
[0053] The material of [W(ΞCtBu)(CH2tBu)3]-RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to catalyst (Rh 1.0, W 2.5). The recovered material prior to catalytic test was characterized. The DRIFT analyses showed the complete disappearance of CH group of the perhydrocarbyl moieties and the appearance of new signals around 3690 cm -1 attributed to hydroxyl group (M-OH, and Ce- OH).
[0054] The surface area measurement (Figure 11) of the WOx- RhOx/CeO2-200 bimetallic based catalyst indicated a surface of ca. 160 m2/g. It should be noted that the surface area decreased (ca. 20 % loss) by the grafting as well as the different thermal treatment. Nevertheless, the surface area remains relatively high.
Example A2-b: Grafting of [W2(OtBu)6] on RhOx-CeO2 through SOMC approach : (WOx-RhOx/CeO2 (Rh 1.0; W 2.5)
[0055] A mixture of [W2(OtBu)6] (120 mg) and ROxx-CeO2-200 (2.15 g) was stirred in toluene for 15 h, at room temperature. The [W2(OtBu)6]/RhOx-CeO2-200 material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0056] The material of [W2(OtBu)6]/RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst (WOx-RhOx/CeO2) (Rh 1.0; W 2.5).
Example A2-c: Grafting of [W(O)(OtBu)4] on RhOx-CeO2 through SOMC approach : (WOx-RhOx/CeO2) (Rh 1.0; W 2.0)
[0057] A mixture of [W(O)(OtBu)4] (150 mg) and ROxx-CeO2-200 (2 g) was stirred in toluene for 15 h, at room temperature. The [W(O)(OtBu)4]/RhOx-CeO2-200 material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0058] The material [W(O)(OtBu)4]/RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst (WOx-RhOx/CeO2) (Rh 1.0; W 2.0).
Example A2-d: Grafting of rw( CtBuHCH2tBu l on RhOx-CeO2- ZrO2 through SOMC approach : (WOx-RhOx/CeO2-ZrO2(200) )(Rh 1.0; W 2)
[0059] A mixture CeO2-ZrO2(200) (6.10 g) and a desired amount of tetra- rhodium dodecacarbonyl as a dark-red crystalline solid (115 mg to reach ca. 1 wt% of Rh) was stirred at 25 °C in toluene (20 ml) for 12 h. After filtration, the
solid [Rh (CO)12]-CeO2-ZrO2-(200) was heated at 60 °C under vacuum (10- 5 mbar) in order to remove the unused complex and to promote the formation of isolated Rh/CeO2-ZrO2(200) species. After calcination at 400 °C under dry air (15 h) (Figure 8 c), bands between 3400 and 3700 cm -1 attributed to different vibration mode of v(CeO-H) are observed - this portion of hydroxyl groups can be further functionalized by other organometallic to yield heterobimetallic catalyst on CeO2-ZrO2 support.
[0060] A mixture of [W(ΞCtBu)(CH2tBu)3] (120 mg) and RhOxx-CeO2- ZrO2(200) (2.15 g) was stirred in toluene for 15 h, at room temperature. The [W(ΞCtBu)(CH2tBu)3]-/RhOx-CeO2-ZrO2(200) material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0061] The material of [W(ΞCtBu)(CH2tBu)3]-RhOx/CeO2-ZrO2(200) was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst (WOx-RhOx/CeO2-ZrO2(200)) (Rh 1.0; W 2).
Example A2-e: Grafting of [V(O)(OEt)3] on RhOx-CeO2 through SOMC approach : (VOx-RhOx/CeO2) (Rh 1.0; V 2.0)
[0062] A mixture of [V(O)(OEt)3] (30 mg) and ROxx-CeO2-200 (1-6 g) was stirred in toluene for 5 h, at room temperature. The [V(O)(OEt)3]/RhOx- CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0063] The material [V(O)(OEt)3]/RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst (VOx-RhOx/CeO2) (Rh 1.0; V 2.0).
Example A2-f: Grafting of [Nb(OEt)5] on RhOx-CeO2 through SOMC approach (NbOx-RhOx/CeO2 ) (Rh 1.0; Nb 1.8)
[0064] A mixture of [Nb(OEt)5] (70 mg) and ROxx-CeO2-200 (1-6 g) was stirred in toluene for 5 h, at room temperature. The [Nb(OEt)5]/RhOx-CeO2-200 material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0065] The material [Nb(OEt)5]/RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst (NbOx-RhOx/CeO2) (Rh 1.0; Nb 1.8).
Part B: Preparation of bimetallic WOx-MOx/CeO2 (M = V, Nb, Fe) catalysts through SOMC approach
Preparation Example Bl: Preparation of WOx-CeO2 through SOMC approach : WOx-CeO2 (W 1.0)
[0066] A mixture of CeO2(200) (8.46 g) and a desired amount of W(ΞCtBu)(CH2tBu)3 as yellow crystalline solid (241 mg to reach ca. 1 wt% of W) was stirred at 25 °C in toluene (20 ml) for 12 h. After filtration, the solid was heated at 60 °C under vacuum (10- 5 mbar) in order to remove the unused complex and to promote the formation of isolated W/ CeO2 species.
[0067] In addition to creating an additional anchoring site, the material obtained in the first step was calcined at 400°C and rehydrated by addition of vapor pressure of water. The sample was heated at 100 °C for 6 h in the presence of the moisture. Afterwards, the material was dehydroxylated under high vacuum (10- 5 Torr) at 200 °C, and the excess as well as the physisorbed water were removed leading to WOx-CeO2-200.
[0068] Similar experiments were carried out for the preparation of the catalysts W0x/Ce02 with different loading (0.87, 1.74, 2, 3.7).
Example B2-a: Preparation of WOx-VOx/CeO2 through SOMC approach: WOx-VOx/CeO2(W 1.0, V 0.8)
[0069] A mixture of VO(OEt)3 (76 mg) and WOx-CeO2-200 (2.34 g) was stirred in toluene for 4 h, at room temperature. The VO(OEt)3/WOx-CeO2-200 material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0070] The material of [W(ΞCtBu)(CH2tBu)3]-RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst (WOx-VOx/CeO2), (W 1.0; V 0.8).
Example B2-b: Preparation of WOx-FeOx/CeO2 through SOMC approach: WOx-FeOx/CeO2 (W 1.0, Fe 0.6)
[0071] A mixture of Fe2(1,3,5-Ph)4 (65 mg) and WOx-CeO2-200 (2.14 g) was stirred in toluene for 4 h, at room temperature. The Fe2(1,3,5-Ph)4/WOx- CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0072] The material of Fe2(1,3,5-Ph)4/WOx-CeO2 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst WOx-FeOx/CeO2 (W 1.0; Fe 0.6).
Example B2-c: Preparation of WOx-NbOx/CeO2 through SOMC approach: WOx-NbOx/CeO2 (W 1.0; Nb 1.2)
[0073] A mixture of Nb(OEt)5 (72 mg) and WOx-CeO2-200 (1-73 g) was stirred in toluene for 4 h, at room temperature. The Nb(OEt)5/WOx-CeO2-200
material was washed three times with toluene via filtration-condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0074] The material of Nb(OEt)5-RhOx-CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst WOx-NbOx/CeO2 (W 1.0; Nb 1.2).
Part C: Preparation of bimetallic VOx-MOx/CeO2 (M = Fe, Cu) catalysts through SOMC approach
Preparation Example Cl: Preparation of VOx-CeO2 through SOMC approach : VOx-CeO2(V 0.8)
[0075] A mixture CeO2-200 (6.5 g) and a desired amount of V(O)(OEt)3 (217 mg) was stirred at 25 °C in toluene (20 ml) for 12 h. After filtration, the solid was heated at 60 °C under vacuum (10- 5 mbar) in order to remove the unused complex and to promote the formation of isolated V/CeO2 species.
[0076] In addition to creating an additional anchoring site, the material obtained in the first step was calcined at 500°C and rehydrated by addition of vapor pressure of water. The sample was heated at 100 °C for 6 h in the presence of the moisture. Afterwards, the material was dehydroxylated under high vacuum (10- 5 Torr) at 150 °C, and the excess as well as the physisorbed water were removed leading to VOx-CeO2-200 (V 0.8).
[0077] A similar experiment was carried out for the preparation of the catalysts VOx/CeO2 with loading 2.1.
Example C2-a: Preparation of VOx-FeOx/CeO2 through SOMC approach: VOx-FeOx/CeO2(v 0.8; Fe 0.5)
[0078] A mixture of Fe2(1,3,5-Ph)4 (56 mg) and VOx-CeO2-200 (2.06 g) was stirred in toluene for 4 h, at room temperature. The Fe2(1,3,5-Ph)4-WOx/ CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0079] The material of Fe2(1,3,5-Ph)4-WOx/CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst VOx-FeOx/CeO2 (V 0.8; Fe 0.5).
Example C2-b (Comparative): Preparation of VOx-CuOx/CeO2 through SOMC approach: VOx-CuOx/CeO2(V 0.8; Cu 0.4)
[0080] A mixture of [Cu(1,3,5-Ph)]4 (78 mg) and VOx-CeO2-200 (2.14 g) was stirred in toluene for 15 h, at room temperature. The [Cu(1,3,5-Ph)]4-WOx/
CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0081] The material of [Cu(1,3,5-Ph)]4-WOx/CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst VOx-CuOx/CeO2 (V 0.8; Cu 0.4).
Part D: Preparation of bimetallic NbOx-MOx/CeO2 (M = Fe, Cu) catalysts through SOMC approach
Preparation Example D1: Preparation of NbOx-CeO2 through
SOMC approach: NbOx-CeO2(Nb 1.2)
[0082] A mixture CeO2-200 (6.4 g) and a desired amount of Nb(OEt)5 (268 mg) was stirred at 25 °C in toluene (20 ml) for 12 h. After filtration, the solid was heated at 60 °C under vacuum (10- 5 mbar) in order to remove the unused complex and to promote the formation of isolated Nb/ CeO2 species.
[0083] In addition to creating an additional anchoring site, the material obtained in the first step was calcined at 500°C and rehydrated by addition of vapor pressure of water. The sample was heated at 100 °C for 6 h in the presence of the moisture. Afterwards, the material was dehydroxylated under high vacuum (10- 5 Torr) at 150 °C, and the excess as well as the physisorbed water were removed leading to NbOx-CeO2- 200 (Nb 1.2).
[0084] Similar experiments were carried out for the preparation of the catalysts NbOx/CeO2 with different loading (1.8; 3.4).
Example D2-a: Preparation of NbOx-FeOx/CeO2 through SOMC approach: NbOx-FeOx/CeO2(Nb 1.2; Fe 0.6)
[0085] A mixture of Fe2(1,3,5-Ph)4 (58 mg) and VOx-CeO2-200 (1-85 g) was stirred in toluene for 15 h, at room temperature. The Fe2(1,3,5-Ph)4-NbOx/
CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0086] The material of Fe2(1,3,5-Ph)4-NbOx/CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h, leading to the catalyst NbOx-FeOx/CeO2 (Nb 0.8; Fe 0.6).
Example D2-b (Comparative): Preparation of NbOx-CuOx/CeO2 through SOMC approach: NbOx-FeOx/CeO2(Nb 1.2; Cu 0.4)
[0087] A mixture of [Cu(1,3,5-Ph)]4 (78 mg) and NbOx-CeO2-200 (2.14 g) was stirred in toluene for 15 h, at room temperature. The [Cu(1,3,5-Ph)]4-
NbOx/CeO2-200 material was washed three times with toluene via filtration- condensation cycles. After evaporation of the solvent, the resulting solid was dried under vacuum (10- 5 Torr).
[0088] The material of [Cu(1,3,5-Ph)]4-WOx/CeO2-200 was calcined using a glass reactor under continuous flow of dry air at 500 °C for 16 h leading to the catalyst NbOx-CuOx/CeO2 (V 0.8; Cu 0.4).
Catalytic activity test conditions
[0089] Pellet samples of approximately 33 mg were prepared under 1 ton pressure and put into a quartz reactor (diameter 4.5mm). A mixture of gas consisting of NO 300ppm, NH3, 350ppm, O2 10%, H2O, 3%, CO2 10%, He (balance), was sent through a catalytic bed at the rate of 300 mL/min. The reactor was heated from room temperature to 600°C with a heating rate of 10 °C/ min. The system was kept at 600°C for 10 min before cooling down to room temperature. Gas composition at the outlet was monitored during the heating up and cooling down by a combination of FTIR and GC-MS.
Claims
1. Process for preparing a catalyst material, comprising the steps of:
(a) providing a support material having surface hydroxyl (OH) groups, wherein the support material is ceria (CeO2), zirconia (ZrO2) or a combination thereof;
(b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
(c) heating the material obtained in step (b), having a grafted metal element, in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
(d) regenerating surface hydroxyl (OH) groups on the material obtained in step (c);
(e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound containing a metal element different to the metal element of the first precursor compound;
(f) heating the material obtained in step (e), having grafted metal elements from both the first and second precursor compounds, in an oxygen- containing atmosphere at a temperature of least 300°C, for at least 1 hour, so as to prepare a catalyst material, wherein one of the first and second precursor compounds is a compound (L) containing a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W), and the other precursor compound is a compound (R) containing a metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt.
2. Process according to claim 1, wherein the support material provided in step (a), and/or the support material obtained by regeneration in step (d), contain(s) at least 0.3 mmol and at most 2.0 mmol OH groups/g of the support
material, and preferably at least 0.5 mmol and at most 1.3 mmol OH groups/g of the support material.
3. Process according to claim 1 or 2, wherein the compound (L) is:
(A) a compound containing at least one alkoxy or phenoxy group bound though its oxygen atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W); or
(B) a compound containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W).
4. Process according to claim 3, wherein the compound (A) containing at least one alkoxy or phenoxy group bound though its oxygen atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W) is at least one compound selected from the group consisting of: [Nb(OEt)5]2; Nb(OAr)5 where Ar is the 1, 3, 5-tri methylphenyl (CH3)3C6H2- group; [W=O(OEt)4]2; [W(O)(OtBu)4]; [W2(OtBu)6]; [V(=O)(OEt)3]2; [V(=O)(O'Pr)3]; and [Ta(OEt)5]2.
5. Process according to claim 3, wherein the compound (B) containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W) is at least one compound selected from the group consisting of: W(=NR)(=CHtBu)2(CH2tBu)2 (R = alkyl or aryl); W(=O)(CH2 tBu)3CI; W(ΞCtBu)(CH2 tBu)3; [(tBuCH2)3W]O;
[(tBuCH2)3W=O]2(μ-O); [tBuO3W=O]2(μ-O); (tBuO)3W=W(tBuO)3;
Mo(=O)(CH2 tBu)3CI; Mo(O)2Mesityl2; V(=O)Mes3; V(=O)CH2SiMe3; Ta(=CHtBu)(CH2 tBu)3.
6. Process according to any of claims 1 to 5, wherein the compound (R) is a compound having alkyl, aryl, alkenyl and/or carbonyl groups bound to the metal element selected from the group consisting of: Ru, Rh, Ir, Pd, Mn, Fe and Pt.
7. Process according to claim 6, wherein the compound (R) is selected from the group consisting of: Rh(F|3-allyl)3; Rh4(CO)i2; Fe(Mesityl)2; Fe(CO)5; Mn(CH2 tBu)2; Me5CpPtMe4; Pd(dba)2; Pd(COD)(CH2SiMe3)2; CpPdMe; Pt(COD)Me2.
8. Process according to any of claims 1 to 7, wherein the compound (R) contains rhodium (Rh) or iron (Fe).
9. Process according to any of claims 1 to 8, wherein compound (L) contains one or more of: tungsten (W), niobium (Nb) and vanadium (V).
10. Process according to claim 9, wherein compound (L) contains tungsten (W).
11. Process according to any of claims 1 to 10, wherein the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 9.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element from Group
5 (V, Nb, Ta) or Group 6 (Cr, Mo, W).
12. Process according to any of claims 1 to 11, wherein the calcined catalyst material obtained by step (f) has at least 0.5 wt% and at most 6.0 wt%, preferably at least 1.0 wt% and at most 6.0 wt%, of metal element selected from the group consisting of: Ru, Mn, Fe, Rh, Ir, Pd and Pt.
13. Process for preparing a catalyst material, comprising the steps of:
(a) providing a support material having surface hydroxyl (OH) groups, wherein the support material is ceria (CeO2), zirconia (ZrO2) or a combination thereof;
(b) reacting the support material having surface hydroxyl (OH) groups of step (a) with a first precursor compound containing a metal element;
(c) heating the material obtained in step (b) having a grafted metal element in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour;
(d) regenerating surface hydroxyl (OH) groups on the heated material containing a grafted metal element obtained in step (c);
(e) reacting the support material having surface hydroxyl (OH) groups of step (d) with a second precursor compound;
(f) heating the material obtained in step (e) in an oxygen-containing atmosphere at a temperature of least 300°C, for at least 1 hour; wherein one of the first or second precursor compounds contains tungsten (W) and the other precursor compound contains vanadium (V) or niobium (Nb), and wherein the calcined catalyst material obtained by step (f) has at least 0.6 wt% and at most 1.4 wt% of tungsten (W), and either at least 0.8 wt% and at most 1.6 wt% of niobium (Nb) or at least 0.5 wt% and at most 1.1 wt% of vanadium (V).
14. Process according to claim 13, wherein the calcined catalyst material obtained by step (f) has at least 0.8 wt% and at most 1.2 wt% of tungsten (W), and either at least 1.0 wt% and at most 1.4 wt% of niobium (Nb) or at least 0.6 wt% and at most 1.0 wt% of vanadium (V).
15. Process according to claim 13 or 14, wherein the calcined catalyst material obtained by step (f) has at least 0.9 wt% and at most 1.1 wt% of tungsten (W), and either at least 1.1 wt% and at most 1.3 wt% of niobium (Nb) or at least 0.7 wt% and at most 0.9 wt% of vanadium (V).
16. Process according to any of claims 13 to 15, wherein the first and second precursor compounds are:
(A) a compound containing at least one alkoxy or phenoxy group bound though its oxygen atom to V, Nb or W; or
(B) a compound containing at least one hydrocarbon group bound though a carbon atom to V, Nb or W.
17. Process according to claim 16, wherein compound (A) is at least one compound selected from the group consisting of: [Nb(OEt)5]2; Nb(OAr)5 where Ar is the 1, 3, 5-tri methylphenyl (CH3)3C6H2- group; [W=O(OEt)4]2; [W(O)(OtBu)4]; [W2(OtBU)6]; [V(=O)(OEt)3]2; [V(=O)(OiPr)3].
18. Process according to claim 16, wherein compound (B) is at least one compound selected from the group consisting of: W(=NR)(=CHtBu)2(CH2tBu)2 (R = alkyl or aryl); W(=O)(CH2 tBu)3CI; W(ΞCtBu)(CH2 tBu)3; [(tBuCH2)3W]O; [(tBuCH2)3W=O]2(μ-O); [tBuO3W=O]2(μ-O); (tBuO)3W=W(tBuO)3; V(=O)Mes3; V(=O)CH2SiMe3.
19. Catalyst material as may be obtained by the process according to any of claims 1 to 12 or by the process according to any of claims 13 to 18.
20. Use of the catalyst material according to claim 19 as an ammonia selective catalytic reduction (NH3-SCR) catalyst for nitrogen oxides (NOx) reduction.
21. Use according to claim 20, wherein the catalytic reduction takes place at a temperature of at most 260°C, preferably at most 250°C, more preferably at most 230°C.
22. Use according to claim 20 or 21, wherein the catalytic reduction takes place at a temperature of at least 100°C, preferably at least 130°C.
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