Decomposition and Reforming of Formic Acid on Supported Au Catalysts: Production of CO-Free H₂

Abstract

The vapor-phase decomposition of formic acid was studied over Au supported on various materials, with the aim of producing COfree H 2. With regards to the decomposition and H 2 formation, Au/SiO 2 was found to be the most active catalyst. The reaction started at 373 K and was complete at 523 K. Depending on the nature of the supports, significant differences were experienced in the reaction pathways. On Au deposited on SiO 2 , CeO 2 , and carbon Norit, dehydrogenation predominated, whereas on Al 2 O 3 , ZSM-5, and TiO 2-supported Au, dehydration of formic acid was favored. Pure CO-free H 2 was obtained on Au/SiO 2 and Au/CeO 2 at and below 473 K. No changes in activity or selectivity were observed within ∼10 h. For most of the catalysts, the selectivity was improved by the addition of water to formic acid. In situ infrared spectroscopic studies revealed the formation of formate species even on Au/SiO 2 , located exclusively on Au particles. The decomposition of HCOOH over Au/SiO 2 followed zero-order kinetics. The activation energy for the decomposition was 60.7 kJ mol À1 , and that for H 2 production was 58.5 kJ mol À1 .

Photolysis of HCOOH over Rh Deposited on Pure and N-Modified TiO2

“…The level of CO can be lowered by the subsequent water-gas shift reaction, but the complete elimination of CO can not be achieved. Surprisingly formic acid as a source of hydrogen has received attention only recently [4][5][6][7][8]. The catalytic effect of Pt metals, Au and Mo 2 C depositing on various oxides and carbon support were tested [4][5][6][7][8].…”

“…Surprisingly formic acid as a source of hydrogen has received attention only recently [4][5][6][7][8]. The catalytic effect of Pt metals, Au and Mo 2 C depositing on various oxides and carbon support were tested [4][5][6][7][8]. CO-free H 2 was obtained only on few catalysts at 423-473 K, mainly in the presence of water [4,5,7,8].…”

“…The catalytic effect of Pt metals, Au and Mo 2 C depositing on various oxides and carbon support were tested [4][5][6][7][8]. CO-free H 2 was obtained only on few catalysts at 423-473 K, mainly in the presence of water [4,5,7,8]. In the present paper we examine the photolysis of formic acid on pure, N-doped and Rh-promoted TiO 2 with the same approach as used in the study of the photodecomposition of ethanol [9].…”

Production of Hydrogen: Photocatalytic Decomposition of Dimethyl Ether over Metal-Promoted TiO<sub>2</sub> Catalysts

“…More frequently used sources of H 2 are ethanol, me-thanol and formic acid [4] [5]. For the generation of H 2 , almost free of CO formic acid is proved to be the more suitable compound [6]- [11]. However, the decomposition of all these compounds occurs at relatively high temperatures at 473 -673 K even on the most active Pt metals.…”

Fotokémiai folyamatok vizsgálata TiO2 hordozós katalizátorokon

“…A CO mennyiségét különböző módszerekkel lehetséges csökkenteni (víz-gáz reakció), de a teljes elimináció nehezen érhető el. Meglepő módon a hangyasav, mint lehetséges hidrogénforrás csak a közelmúltban kapott figyelmet 112,113 .…”