Dehydrogenation, of formic acid

This means that such a reaction is independent of the concentration, or of zero order. Such a case is presented by the dehydrogenation of formic acid vapor on metals. If, on the contrary, bp < . 1, we have... 

Dehydrogenation of formic acid on metals and alloys, decomposition of... 

Fig. 16. Dehydrogenation of formic acid on the Cu/Zn alloys [G. M. Schwab and S. Pesmatjoglou, J. Phys. Chem. 62, 1046 (1948)].

Fig. 10. Relationship between the rate of dehydrogenation of formic acid wdth Rh-PVA catalyst contains 10 mg. of Rh and 200 mg. PVA. [From Hernandez and Nord, J. Colloid Sci. 3, 377 (1948), Figure 1, p. 379.]...

Dynamic Catalytic Dehydrogenation of Formic Acid on a TiO2(TI0) Surface... 

Fig. 17. Dehydrogenation of formic acid on Cu-Ag alloys, according to Schwab and Schwab-Agallidis (20), and according to Rienacker. —Rienacker, static decomposition O—Schwab, static decomposition A—Schwab, dynamic decomposition.

Fig. 18. Dehydrogenation of formic acid on Cu-Pd alloys, according to Rienacker, Wcssing, and Trautrnarm (6S) (Cu and Pd form a continuous scries of solid solutions). O—disordered alloys X—ordered alloys.

All in all, we do not believe that the experiments described in this section invalidate the concept of a formate ion being the adsorbed intermediate in the dehydrogenation of formic acid on metals. 

The kinetics of the dehydrogenation of formic acid on oxides are not extensively investigated only about the reactions on MgO and on Fes04 are some data available. 

As mentioned already in the introduction, the dehydrogenation of formic acid proceeds particularly well on MgO and ZnO. It is, however, always accompanied by a dehydration reaction. The following scheme gives the order of selectivity ... 

The activities for the dehydrogenation of formic acid given in literature are compiled in Fig. 23 here the reaction rate per sq cm of the accessible catalyst surface area is given as a function of temperature. If not given by the authors, the value of the accessible surface area is estimated from experience. This figure shows that the specific activity as well as the activation energy of the reaction depend largely on the nature of the oxide (see also Table V). 

In both dehydrogenation and dehydration formate ions on the surface thus seem to play a central role. It is therefore of interest to study the decomposition of bulk formates, although it is obviously to be expected that there will always be differences between two-dimensional surface compounds and bulk compounds. The decomposition reactions of various formates will be discussed in the following section. Knowledge of the properties of these compounds will enable us to deal more extensively with the reaction mechanisms of the dehydration and the dehydrogenation of formic acid. 

Figure 40.15 Thermal conversion of glucose followed by catalytic dehydrogenation of formic acid in IL [86].

With the experience gathered in the development of DMFCs, Pt-Ru catalysts were used for the anodic process in the early studies on DFAFCs. Ha et al. (2006) showed that much better electrical characteristics can be obtained with palladium black as the catalyst. Importantly, with this catalyst one can work at much lower temperatures. In particular, at a temperature of 30°C, power densities of 300 mW/cm were obtained with a voltage of 0.46 V, and about 120 mW/cm with a voltage of 0.7 V. The differences between the two catalysts probably are due to the fact that with Pt-Ru, formic acid oxidation follows the second of the mechanisms mentioned (chemisorption with dehydration), while palladium black is a highly effective catalyst for the dehydrogenation of formic acid, the first mechanism being followed on it. It must be pointed out that this effect is highly specific in methanol oxidation, the catalytic activity of palladium is lower than that of Pt-Ru. 

Dehydrogenation of formic acid is catalysed by the cobalt(i) compoimds Co( (CO) ,(PBu 3)4 a, where x — 1, 2, or 3 the compound with jc = 2 is the most efiective catalyst. Rates of dehydrogenation vary with the solvent used, being greatest in the most polar media. Some of the... 

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