Formaldehyde combustion

Indoor Air Quality Control Techniques Radon, Formaldehyde, Combustion Products, Eds., W.J. Fisk, R.K. Spencer, D.T. Grimsrud, EJ. Offerman, B. Pedersen and R. Sextro, Noyes Data Corporation, Park Ridge, NJ, USA, 1987. 

Formaldehyde, HCHO, is a primary and necessary constituent of the first five synthetic adhesives in the listing. It is a simple organic chemical first identified during the latter half of the 1800s. Its irritating and toxic odor and preservative properties were known from the time of its early development. It is a ubiquitous chemical, formed naturally in small quantities by every process of incomplete combustion as well as in normal biologic processes. The human body has a natural formaldehyde level of about 3 lg/g, ie, 3 parts per million (ppm) in the blood at all times. 

Other applications of zirconium tetrafluoride are in molten salt reactor experiments as a catalyst for the fluorination of chloroacetone to chlorofluoroacetone (17,18) as a catalyst for olefin polymerization (19) as a catalyst for the conversion of a mixture of formaldehyde, acetaldehyde, and ammonia (in the ratio of 1 1 3 3) to pyridine (20) as an inhibitor for the combustion of NH CIO (21) in rechargeable electrochemical cells (22) and in dental applications (23) (see Dentalmaterials). 

Emissions from methanol vehicles are expected to produce lower HC and CO emissions than equivalent gasoline engines. However, methanol combustion produces significant amounts of formaldehyde (qv), a partial oxidation product of methanol. Eormaldehyde is classified as an air toxic and its emissions should be minimized. Eormaldehyde is also very reactive in the atmosphere and contributes to the formation of ozone. Emissions of NO may also pose a problem, especiaHy if the engine mns lean, a regime in which the standard three-way catalyst is not effective for NO reduction. 

Both urea— and melamine—formaldehyde resins are of low toxicity. In the uncured state, the amino resin contains some free formaldehyde that could be objectionable. However, uncured resins have a very unpleasant taste that would discourage ingestion of more than trace amounts. The molded plastic, or the cured resin on textiles or paper may be considered nontoxic. Combustion or thermal decomposition of the cured resins can evolve toxic gases, such as formaldehyde, hydrogen cyanide, and oxides of nitrogen. 

Unbumed Hydrocarbons Various unburned hydrocarbon species may be emitted from hydrocarbon flames. In general, there are two classes of unburned hydrocarbons (1) small molecules that are the intermediate products of combustion (for example, formaldehyde) and (2) larger molecules that are formed by pyro-synthesis in hot, fuel-rich zones within flames, e.g., benzene, toluene, xylene, and various polycyclic aromatic hydrocarbons (PAHs). Many of these species are listed as Hazardous Air Pollutants (HAPs) in Title III of the Clean Air Act Amendment of 1990 and are therefore of particular concern. In a well-adjusted combustion system, emission or HAPs is extremely low (typically, parts per trillion to parts per billion). However, emission of certain HAPs may be of concern in poorly designed or maladjusted systems. 

Fire Hazards - Flash Point (deg. F) 203 OC Flammable limits in Air (%) 3 - 6.3 Fire Extinguishing Agents Water, foam, dry chemical, or carbon dioxide Fire Extinguishing Agems Not to be Used Not pertinent Special Hazards of Combustion Products Sulfur dioxide, formaldehyde, and methyl mercaptan may form Behavior in Fire Not pertinent Ignition Temperature (deg. F) 572 Electrical Hazard Not pertinent Burning Rate 2.0 mm/min. 

Unlike carbon dioxide and water that are the inevitable by products of complete combustion of hydrocarbons, species such as carbon monoxide, ethene, toluene, and formaldehyde can be emitted because combustion has been interrupted before completion. Many factors lead to emissions from incomplete combustion. Emitted unburned hydrocarbons and carbon monoxide are regulated pollutants that must be eliminated. In automobiles with spark ignited engines, these emissions are almost entirely removed by the catalytic converter. 

Formaldehyde is a harmful compound released from walls and furnitures in new houses because adhesives containing HCHO are often used in constmction materials. In addition, H CHO is emitted by tobacco smoke and combustion exhaust gases. Long exposure to HCHO causes serious health problems called sick house diseases. In Japan, the concentration of HCHO in indoor air is regulated [54] to under 0.08 ppm based on the recommendation of the World Health Organization (WHO). 

Aniline reacts with perchloric acid and then formaldehyde to give an explosively combustible condensed resin. 

Gaseous formaldehyde, 12 123 13 759 Gaseous fuel combustion technology, 7 455 60... 

Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rates of formaldehyde were 1,165 mg/kg of pine burned, 759 mg/kg of oak burned, and 599 mg/kg of eucalyptus burned. 

The re-oxidation of lead was expected to occur rapidly at 600 K the surface of the lead oxide would then remain unchanged in the presence of oxygen. The authors concluded that, as a consequence, general hydrocarbon combustion in which formaldehyde is a degenerate branching intermediate is inhibited in the presence of PbO by the rapid removal of formaldehyde. 

As one might guess from our previous example of H2 oxidation, this reaction is extremely complex. The standard model involves over 300 reaction steps among approximately 30 chemical species. Here even the stable product species can be complex, with CO, HCHO (formaldehyde), and soot (carbon) being among the highly undesired pollutants in CH4 combustion. Since H2, O2, and H2O are involved as intermediates and products, the 38 reaction steps in the H2 + O2 reaction hsted previously set of the reactions that be involved in CH4 oxidation. 

Numerous polymers autooxidize to form peroxides. These compositionally, and thus calorimetrically, ill-defined products may be considered polymeric peroxides. However, one well-defined polymeric peroxide is that of polystyrene with the repeat unit —CHa-CH(CeH5)-0-0-. Through a combination of combustion and reaction calorimetry (chain degradation to benzaldehyde and formaldehyde), a solid phase enthalpy of formation of this species was found to be 27 21 kJ mol . Much the same procedure was used to determine the enthalpy of degradation for the polyperoxide polymers of 2-vinylnaphthalene and the isomeric 1- and 2-propenylnaphthalene to form the related acylnaphthalene and formaldehyde. Numerically, the reaction enthalpy values for these last three polyperoxides were —206+4, —222 + 8 and —222 + 10 kJmol, to be compared with the aforementioned polystyrene with a value of —209 + 8 kJ mol. However, in the absence of enthalpy of formation data for the decomposition products in the naphthalene case, we hesitate to derive enthalpies of formation for these three species. ... 

Recently, the enthalpies of combustion and sublimation were measured for formaldehyde diperoxide, i.e. 1,2,4,5-tetroxane , from which the enthalpies of formation could be derived. These results were shown to be in good agreement with quantum chemical... 

Methanol is expected to oxidize to formaldehyde, both during combustion and after emission to the atmosphere. As discussed in Chapter 6.H, OH reacts with methanol primarily at the methyl group ... 

HaCH2.C(N02XC2H6)-CH20H, mw 149.15, N9-39% ndls (w), mp 57-8°, sol in w, ale eth. Was first ptepd by Pauwels (Ref 2) on condensation of formaldehyde with Tnitropio-pane in presence of K carbonate. Vanderbilt Hass (Ref 3 4) described rriethods of repn with yields up to 96% using formalde-yae, 1-nitropropane and tertiary amines or alkali hydroxides. Medard (Ref 5) and Med-ard Thomas (Ref 6) detd its heats of combustion (703.7 kcal/mjQ,) and formation. 

Results of analysis of formic acid in diesel engine exhaust subjected to various forms of post-combustion control, i.e., catalytic oxidation and water conditioning, indicate both a reduction of formic acid due to oxidation in the catalyst and dissolution in the water scrubber. In-mine analysis of formic acid at increasing distances from a source of diesel exhaust indicates that no significant change in concentration occurs. This finding contradicts a hypothesis that formaldehyde concentration decreases with increasing distance due to gas phase oxidation to formic acid. Surface reactions may, however, be important sinks for formaldehyde. 

FORMALDEHYDE SOLUTION Formalith, Formalin, Formic Aldehyde, Methanal, Fide Combustible Liquid, III 2 2 0... 

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