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The conversion of polysaccharides to hydrogen gas. Part I: The palladium catalysed decomposition of formic acid/sodium formate solutions
Author(s) -
Hill S. P.,
Winterbottom J. M.
Publication year - 1988
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280410205
Subject(s) - sodium formate , formic acid , formate , chemistry , catalysis , hydrogen , inorganic chemistry , carbon monoxide , palladium , methyl formate , decomposition , organic chemistry
The palladium catalysed decomposition, to H 2 +CO 2 , of solutions containing formic acid and sodium formate, in various proportions, has been studied in a stirred reactor in the temperature range 60–90°C. The production of hydrogen gas was at its optimum in the pH range 3.8–6.5 and the order of reaction varied with the solution composition from 0.33 (100 mol % formic acid) to 1.07 (100 mol% formate ion). Energies of activation lay in the range 20±9.5 kJ mol −1 –41.8±7 kJ mol −1 , the larger values occurring at the ends of the composition range. Electrode potential measurements were also performed and these were helpful in explaining the (i) cessation of hydrogen production at low HCOO − ion concentrations before completion of reaction and (ii) the possible nature of catalyst poisons. In no case was the theoretical quantity of hydrogen obtained, although yields >90% can be achieved. It is proposed that reaction proceeds via a surface formate intermediate with different rate determining steps operating at high and low HCOO − ion concentrations. A number of reversible catalyst poisons are discussed including carbon monoxide and methyl formate, which appear to be the most likely.