Catalytic reactions of formate. 3. Noble metal chlorides as catalyst precursors for formic acid reactions

Abstract

Noble metal chlorides ('RuCI~-xH20', 'RhC13"3H20', PdC12 and 'IrC13 "xH20' ) have been evaluated as catalyst precursors for the decomposition (HCO2H ~ H 2 + CO2), dehydration (HCO2H ~H20 + CO) and air oxidation (2HCO2H + O z ~2H20 + 2CO2) of 88% HCO2H at 75-80 ~ RhC13 under these conditions is an active oxidation catalyst but not an active decomposition catalyst. However, RuC1 a is an active decomposition catalyst but not an active oxidation catalyst. PdC12 exhibits modest but detectable activity for all three formic acid reactions (decomposition, dehydration and oxidation). IrCl 3 is a relatively active catalyst for all three HCO2H reactions. A comparison of the catalytic activities of the four noble metal chlorides for HCOzH decomposition under conditions where both the dehydration and air oxidation reactions are suppressed (4.4% aqueous HCOzH. Ar atmosphere) indicates the relative catalytic activity sequence: Ir >> Ru > Pd >> Rh (inactive).

Hydrogen Generation from Formic Acid Decomposition by Ruthenium Carbonyl Complexes. Tetraruthenium Dodecacarbonyl Tetrahydride as an Active Intermediate

“…PdCl 2 exhibited only moderate but detectable activity, whereas RhCl 3 seemed to be inactive under the reaction conditions. [32] It was found in the course of control experiments that pure FA decomposed in the absence of a catalyst in the temperature range from 78-98 8C, resulting in an increased concentration of CO in the gas phase as a function of temperature whereas the formation of H 2 was negligible. The activation energy for the dehydration of 88 % FA, determined from an Arrhenius plot, was 123 kJ mol À1 .…”

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols

“…Initial FA dehydrogenations rates of up to 80 mol L –1 h –1 (TOF ≈ 8900 h –1 ) were attained with an [IrH 3 (PPh 3 ) 3 ] catalyst, which was also successfully employed in the transfer hydrogenation of n -butyraldehyde to n -butanol with a 70% yield. In the subsequent decades, several rhodium-, iridium-, and ruthenium-based catalysts were tested for FA dehydrogenation, albeit resulting in only moderate activities. ,− In certain studies, FA was evaluated as a hydrogen donor in transfer hydrogenation rather than as a hydrogen storage medium. In 1998, Puddephatt and co-workers reported the binuclear ruthenium complex Ru 2 (μ-CO)­(CO) 4 (μ-DPPM) 2 , which exhibited improved activity (TOF = 500 h –1 ) in acetone without basic additives and at room temperature (RT). , However, it was not until 2008, when the potential application of FA as a liquid organic hydrogen carrier was highlighted independently by the groups of Laurenczy and Beller, , that intensive investigations were resumed.…”

Highly Efficient Base‐Free Dehydrogenation of Formic Acid at Low Temperature

“…Although the hydrogenc ontent of 4.4 wt %i ss lightly lower than the desired target (4.5 wt %u ntil 2020) of the U.S.Department of Energy( DOE), [8,9a] it has severala dvantages:I ti sn ontoxic, widely produced in industry,a nd ab iologically formed product of biomass fermentation. This process occurs at highert emperatures [10] or in the presenceo fc oncentrated acid. The energetically favoredd ehydrogenation pathway results in H 2 and CO 2 as products.…”

“…However, decarbonylation of formic acid alternativelyf orms CO and water as products. This process occurs at highert emperatures [10] or in the presenceo fc oncentrated acid. [11] Since CO 2 is tolerated by protone xchange membrane fuel cells( PEMFCs) but carbon monoxide poisons the same, [12] any catalystm ust be designed such that very highly selectivity for formic acid dehydrogenation is achieved at low temperature.…”