Formic from HCHO

Figure 13.3 Potentiodynamic electrooxidation of (a) formic acid, (b) formaldehyde, and (c) methanol on a Pt/Vulcan thin-film electrode (7 xgpt cm, geometric area 0.28 cm ) in 0.5 M H2SO4 solution containing 0.1 M HCOOH (a), HCHO (b), or CH3OH (c). The potential scan rate was 10 mV s and the electrolyte flow rate was 5 p-L s at room temperature). The top panels show the faradaic current (solid lines), the partial currents for Ci oxidation to CO2 (dashed lines) and for formic acid formation (dash-dotted line), calculated from the respective ion currents, and the difference between the measured faradaic current and the partial current for CO2 oxidation (formic acid oxidation (a), formaldehyde oxidation (b)), or the difference between faradaic current and the sum of the partial currents for CO2 formation and formic acid oxidation (methanol oxidation, (c)) (dotted line). The solid lines in the lower panels in...

Figure 13.6 Potential-step electro-oxidation of formaldehyde on a Pt/Vulcan thin-film electrode (7 p,gpt cm, geometric area 0.28 cm ) in 0.5 M H2SO4 solution containing 0.1 M HCHO upon stepping the potential from 0.16 to 0.6 V (electrolyte flow rate 5 pL at room temperature). (a) Solid line, faradaic current transients dashed line, partial current for HCHO oxidation to CO2 dotted line, difference between the net faradaic current and that for CO2 formation, (b) Solid line, m/z = 44 ion current transients gray line potential-step oxidation of pre-adsorbed CO derived upon HCHO adsorption at 0.16 V, in HCHO-free sulfuric acid solution, (c) Current efficiency transients for CO2 formation (dashed line) and formic acid formation (dotted line).

Figure 8.5, for example, shows that the yield of formic acid first increases and then decreases as the SOz concentration increases, as expected from the competition of reactions (9) and (10) for the adduct. At the same time, as seen in Fig. 8.6, the increased yield of HCHO upon addition of S02 to the ethene-ozone reaction was equivalent to the consumption of S02 (Hatakeyama et al., 1986). 

An introduction to the typical resin synthesis of a UF resin used as an adhesive for wood products and in industrial applications is given below. It constitutes a handy formulation for those who want to work in this field. It is not a low-formaldehyde-emission formulation. To 1000 parts by mass of 42% formaldehyde solution (methanol < 1%) are added 22% NaOH solution to pH 8.3 to 8.5,497 parts by mass of 99% urea, and the temperature raised in 50 min from ambient to 90°C while maintaining pH in the range 7.3 to 7.6 by small additions of 22% NaOH. The temperature is maintained at 90 to 91°C until the turbidity point is reached (generally another 15 to 20 min). The pH is then corrected to 4.8 to 5.1 by addition of 30% formic acid, and the temperature is raised to 98°C. The water tolerance point is reached in 18 min and the pH is then adjusted to 8.7. Vacuum distillation of the reaction water with concomitant cooling is then initiated. After distillation of the wanted amount of water to reach a resin content of 60 to 65%, the resin is cooled to 40°C, 169 parts by mass of second urea is added, the pH is adjusted to 8.5 to 8.7, and the resin is allowed to mature at 30°C for 24 to 48 h resin characteristics solids content, 60% density, 1.268 g/cm free HCHO, 0.4% viscosity, 200cP pH, 8. 

Chapter 5.3.3, HCHO provides a net source of radicals. The formation of formic acid is likely to be negligible in the gas phase. But methanol, formaldehyde and formic acid (all produced and/or emitted in huge quantities from biogenic sources) will be scavenged and provide more efficient oxidation, finally with an accumulation of formic acid, but partly until its mineralization to CO2 and, most interestingly, a pathway in the formation of highly reactive bicarbonyls such as glyoxal and oxalic acid. 

Hydrocarbons can have many different effects on FC performance depending on their structure. Methane acts as an inert species in the fuel diluting the concentration, but does not interact strongly with the catalyst surface to disrupt the HOR. Aromatic hydrocarbons interact more strongly with the catalyst surface and tend to hydrogenate to cycloparaffins (Bender et ah, 2009). While this is a parasitic consumption of Hj, the effect of 20 ppm toluene on FC performance was minimal. Oxygenated hydrocarbons such as formic acid (HCOOH) and formaldehyde (HCHO) were explored in the literature because they are intermediate products of methanol reforming. The behavior of PEMFCs when exposed to formic acid or formaldehyde in Hj is very similar to CO it is characterized by initially rapid decreases in PEMFC performance followed by a saturation period and partial recovery when the contaminant is removed from the Hj (Narusawa et ah, 2003). 

While formic acid accumulation in folic deficiency makes it clear that the main route for formate removal is folic-mediated, little is known in this respect about formaldehyde, which arises from the oxidation of methyl groups or the folic-mediated reduction of formate (Section II, 5). Perhaps an important connection between Ci and the principal pathways for substrates is indicated by the finding that HCHO is an excellent acceptor for the ketol group ( active glycolaldehyde ) formed from a variety of ketose phosphates and from hydroxypyruvate (Dickens and Williamson, 1958). This reaction may be formulated as follows ... 

---