Um dos fatores limitantes de uma economia baseada em hidrogênio está associado à problemas de estocagem de hidrogênio. Muitas abordagens diferentes estão sendo avaliadas e uma abordagem ótima não será a mesma para todas as aplicações, i.e., necessidades estática, móvel, pequena e grande escala, etc. Neste artigo, foca-se no ácido fórmico como molécula promissora para o estoque de hidrogênio, que, em certas condições catalíticas, pode ser desidrogenado gerando hidrogênio altamente puro e dióxido de carbono, com níveis extremamente baixos de monóxido de carbônico gasoso produzido. Vários catalisadores homogêneos disponíveis que geralmente operam em soluções aquosas de ácido fórmico são descritos. Também é descrita brevemente a reação reversa que pode contribuir para tornar o uso de ácido fórmico em estoque de hidrogênio ainda mais atrativo.
Reviews • J. Braz. Chem. Soc. 25
(12)
• Dez 2014 • https://doi.org/10.5935/0103-5053.20140235 linkcopiar
Homogeneous Catalytic Dehydrogenation of Formic Acid: Progress Towards a Hydrogen-Based Economy
Autoria
person Gábor Laurenczy
*
schoolInstitut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, SwitzerlandInstitut des Science et Ingénierie ChimiquesSwitzerlandLausanne, SwitzerlandInstitut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
person Paul J. Dyson
schoolInstitut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, SwitzerlandInstitut des Science et Ingénierie ChimiquesSwitzerlandLausanne, SwitzerlandInstitut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
Paul Dyson
is currently the director of the Institute of Chemical Sciences and Engineering at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and a guest professor at Shangai Jiao Tong University in China. He joined the EPFL in 2002 where he established the Laboratory of Organometallic and Medicinal Chemistry. Prior to joining the EPFL he had positions at Imperial College of Science, Technology and Medicine and the University of York. He obtained a PhD in organometallic chemistry in 1993 from the University of Edinburgh.
Gabor Laurenczy
is the Head of Group of Catalysis for Energy and Environment (GCEE), professor in the Laboratory of Organometallic and Medicinal Chemistry at École Polytechnique Fédérale de Lausanne (EPFL), in Switzerland. He has got his PhD in 1980 in Inorganic Chemistry, at the Lajos Kossuth University, in Debrecen, Hungary. He was pointed out there as assistant professor in 1984, and he has made his habilitation in 1991. In 1985 he moved to Switzerland, he had positions at University of Lausanne and at EPFL.
SCIMAGO INSTITUTIONS RANKINGS
Institut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, SwitzerlandInstitut des Science et Ingénierie ChimiquesSwitzerlandLausanne, SwitzerlandInstitut des Science et Ingénierie Chimiques (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
Figuras | Tabelas | Fórmulas
imageScheme 1 The carbon dioxide-formic acid cycle. open_in_new

imageFigure 1 Proposed mechanism for the selective iron-catalyzed hydrogen generation from formic acid with calculated relative energies of complexes (kJ mol−1).29,33 Reproduced with permission of The American Association for the Advancement of Science (3470280610808). open_in_new

imageFigure 2 Proposed reaction mechanism involving two competing cycles in the formic acid dehydrogenation reaction using the RuCl3 pre-catalyst with the water-soluble m-trisulfonated triphenylphosphine (mTPPTS = P) ligand.46 Reproduced with permission of J. Wiley and Sons (3470260322908). open_in_new

table_chartTable 1
Bicarbonate, carbonate and carbon dioxide hydrogenation into formic acid/formate or formic acid derivatives with ruthenium(II) pre-catalysts
| Catalyst | Solvent | Base | PCO2/H2 / bar | TON | TOF / h-1 | Ref. |
|---|---|---|---|---|---|---|
| [RuH2(PMh3)4] | Benzene | NEt3/H2O | 25/25 | 87 | 4 | 8 |
| [RuH2(PPh3)4] | scCO2 | NEt3, H2O | 120/80 | 1'400 | 1'400 | 9 |
| [RuCl2(PMe3)4] | scCO2 | NEt3, H2O | 120/80 | 7'200 | - | 6 |
| [RuCl(OAc)(PMe3)4] | scCO2 | NEt3/C6F5OH | 120/70 | 32'000 | 95'000 | 10 |
| [Ru(6,6'-Cl2bpy)2(H2O)2]/(CF3SO3)2 | EtOH | NEt3 | 30/30 | 5'000 | - | 11 |
| [RuHCl(CO)(PNP)] | DMF | DBU | 10/30 | - | 1'100'000 | 12 |
| [TpRu(PPh3)(CH3CN)H] | THF | NEt3, H2O | 25/25 | 760 | 48 | 13 |
| [TpRu(PPh3)(CH3CN)H] | THF | NEt3, CF3CH2OH | 25/25 | 1'815 | 113 | 14 |
| [RuCl2(TPPMS)2] | H2O | NaHCO3 | - | 320 | 9'600 | 15 |
| [Ru(η6-C6Me6)(4,4'-OMe-bpy)(OH2)](SO4) | H2O | Citrate buffer | - | 55 | - | 16 |
| [(η6-C6Me6)Ru(bis-NHC)Cl] | H2O | KOH | - | 23'000 | - | 17 |
| [Ru(η6-C6Me6)(DHPT)Cl]Cl | H2O | KOH | - | 15'400 | 3'600 | 18 |
| [Ru(η6-C6Me6)(DHBP)Cl]Cl | H2O | KOH | - | 13'620 | 4'400 | 18 |
| [RuCl2(PTA)4] | H2O | - | 50/150 | 204 | - | 7 |
| [RuCl2(PTA)4] | DMSO | - | 50/150 | 749 | - | 7 |
-
TON: turnover number; TOF: turnover frequency.
table_chartTable 2
Bicarbonate, carbonate and carbon dioxide hydrogenation into formic acid/formate or formic acid derivatives with other metal based catalysts
| Catalyst | Solvent | Base | PCO2/H2 / bar | TON | TOF / h-1 | Ref. |
|---|---|---|---|---|---|---|
| [RhCl(TPPTS)3] | H2O | NHMe2 | - | 3'400 | 7'300 | 20 |
| [Ir(η5-C5Me5)(DHPT)Cl]Cl | H2O | KOH | - | 222'000 | 33'000 | 21 |
| [IrI2(AcO)(bis-NHC2)] | H2O | KOH | - | 190'000 | 2'500 | 22 |
| [IrCp*(DHBP)Cl]Cl | H2O | KOH | - | 190'000 | 42'000 | 18 |
| [{IrCp*Cl}2(thbpym)]2+ | H2O | KHCO3 | - | 153'000 | 53'800 | 23 |
| [Ir(PNP1)H3] | H2O | KOH/THF | - | 3'500'000 | 150'000 | 19 |
| [(PNP2)Fe(H)2(CO)] | HH2O | NaOH/THF | - | 788 | 156 | 24 |
| [Rh(cod)Cl]2 /dppb | DMSO | NEt3 | 20/20 | 1'150 | - | 25 |
| [Rh(cod(μ-H)]4 / PPh2(CH2)4PPh2 | DMSO | NEt3 | 20/20 | 2'200 | 375 | 26 |
| [Rh(hfacac)(dcpb)] | DMSO | NEt3 | 20/20 | - | 1'335 | 27 |
| [RhCl(PPh3)3] | MeOH | NEt3/PPh3 | 40/20 | 2'700 | 125 | 28 |
| Fe(BF4)*6H2O/PP3 | MeOH | NaHCO3 | 0/60 | 610 | 30 | 29 |
| Co(BF4)*6H2O/PP3 | MeOH | NaHCO3 | 0/60 | 2'877 | 200 | 30 |
| FeCl3/dcpe | DMSO | DBU | 60/40 | 113 | 15.1 | 31 |
| NiCl2/dcpe | DMSO | DBU | 160/40 | 4'400 | 20 | 31 |
| MoCl3/dcpe | DMSO | DBU | 60/40 | 63 | 8.4 | 31 |
-
TON: turnover number; TOF: turnover frequency.
table_chartTable 3
Selective catalytic cleavage of the formic acid into carbon dioxide and hydrogen
| Catalyst | Substrate | Solvent | Temperature / ºC | TON | TOF / h-1 | Ref. |
|---|---|---|---|---|---|---|
| [Ir(PPh3)H3] | HCOOH | AcOH | 118 | 11'000 | 8'900 | 34 |
| [RuCl2(benzene)]2/DPPE | HCOOH | Me2NHex | 25 | 260'000 | 900 | 35 |
| [RuCl2(PPh3)3] | HCOOH | NEt3 | 40 | 891 | 2'700 | 36 |
| [Ru(k3-triphos)(MeCN)3](OTf)2 | HCOOH | NMe2Oct | 80 | 10'000 | - | 37 |
| [Ir(PNP1)H3] | HCOOH/tBUOH | Et3N/THF | 80 | 5'000b | 120'000c | 19 |
| [RuHCl(CO)(PNP2)] | HCOOH | DMF/NHex3 | 90 | 706'500 | 256'000 | 38 |
| [Cp*IrCl(N^C)] | HCOOH | NEt3 | 40 | - | 147'000 | 39 |
| [RuCl2(DMSO)4] | HCOOH | NEt3 | - | 25'000 | 18'000 | 40 |
| [Fe3(CO)12]/PPh3/tpy | HCOOH/NEt3 | DMF | 40 | 200 | - | 41 |
| [Fe3(CO)12]/PBn3/tpy | HCOOH/NEt3 | DMF | 40 | 1'266 | - | 42 |
| [Fe(BF4)2]*6H2O/PP3 | HCOOH | Prop. carb. | 80 | 92'417 | 9'425 | 33 |
| [(PNP2)Fe(H)2(CO)] | HCOOH | THF/NEt3 | 40 | - | 836 | 43 |
| [IrH3(PNP1)] | HCOOH/HCOONa | H2O/THF | 60 | 890 | - | 19 |
| [Cp*Ir(DHBP)(H2O)](SO4) | HCOOH | H2O | 90 | 10'000 | 14'000 | 44 |
| [Cp*Rh(DHBP)(H2O)](SO4) | HCOOH | H2O | 80 | 83'000 | 7'700 | 45 |
| RuCl3/TPPTS | HCOOH | H2O | 120 | 40'000 | 670 | 46 |
| RuCl3/cationic phosphines | HCOOH | H2O | 120 | 10'000a | 1'950 | 47 |
| [Ir(Cp*)(H2O)(bpm)Ru(bpy)2](SO4)2 | HCOOH/HCOONa | H2O | 25 | 142 | 426 | 48 |
| [(Cp*Ir)2(thpbym)Cl2] | HCOOH/HCOONa | H2O | 80 | 308'000 | - | 23 |
| [Ir(Cp*)(TH4BPM)(H2O)] (SO4) | HCOOH/HCOONa | H2O | 80 | 11'000 | 39'500 | 49 |
-
TON: turnover number; TOF: turnover frequency.
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