Catalytic mufflers

Platinum is used as a catalyst for nitric and sulphuric acid production, in petroleum refining and in catalytic mufflers to control air pollution. Platinum salts can cause respiratory complaints, asthma, and platinosis , an allergic response. Allergic dermatitis may also result from exposure to soluble platinum salts and once subjects have been sensitized it generally precludes continued occupational exposure at any level. The 8 hr TWA OEL for platinum metal is 5 mg/m but for soluble platinum salts it is only 0.002 mg/m. Handling precautions must include containment where possible, ventilation, personal protection, and the screening out of individuals who have become sensitized. 

As an example, when automotive catalytic mufflers and converters were introduced many years ago, the automobile industry required the petrochemical industry to eliminate lead from gasoline since lead degraded and reduced the effectiveness of the catalyst and caused the destruction of the gasoline. One set of industrial compounds that can harm catalysts are halogens, a family of compounds that include chlorine, bromine, iodine, and fluorine. Bromine, while not prevalent in industry, is present in chemical plants. Freons are fluorine compounds. Silicone is another compound that is deleterious to catalysts. It is used as a slip agent, or a lubricant, in many industrial processes. Phosphorous, heavy metals (zinc, lead), sulfur compounds, and any particulate can result in shortening the life of the catalyst. It is necessary to estimate the volume or the amount of each of those contaminants, to assess the viability of catalytic technologies for the application. 

When a simple, fast and robust model with global kinetics is the aim, the reaction kinetics able to predict correctly the rate of CO, H2 and hydrocarbons oxidation under most conditions met in the DOC consist of semi-empirical, pseudo-steady state kinetic expressions based on Langmuir-Hinshelwood surface reaction mechanism (cf., e.g., Froment and Bischoff, 1990). Such rate laws were proposed for CO and C3H6 oxidation in Pt/y-Al203 catalytic mufflers in the presence of NO already by Voltz et al. (1973) and since then this type of kinetics has been successfully employed in many models of oxidation and three-way catalytic monolith converters... 

Unsteady-state operation of a monolith was modeled to study the light-off behavior of catalytic mufflers as well as the deactivation of the catalyst. 

Modeling of the monolith dynamics presents an opportunity to improve the performance of catalytic mufflers by involving the benefits of cyclic operation via an appropriate control strategy. 

Response to Oxides of Nitrogen Other than Nitric Oxide. Although NO is normally the oxide of nitrogen in combustion products, exhaust aging at ambient temperature forms other products such as N02, N204, N205, and HN03. Catalytic muffler treatment of exhaust may produce... 

Oh and Cavendish " (L),(T) Investigation of poison accumulation in washcoats for catalytic mufflers... 

Total gas-phase volumetric flow rate = 3 L/min = 3000 cm /min Diameter of the catalytic muffler = 7 cm Interpellet porosity of the packed catalytic reactor = 0.45 Overall length of the catalytic muffler = 15 cm... 

Precontrol—no catalytic mufflers installed) 1993 (Catalytic mufflers required on all automobiles) 2004 Standards... 

Sulfur compounds are corrosive and foulsmelling. When burned in an engine, these compounds result in sulfur dioxide exhaust. Should the engine be equipped with a catalytic muffler, as is the case for many modern automobile engines, the sulfur is exhausted from the muffler as sulfur trioxide, or sulfuric acid mist. 

Chemical reaction engineering problems associated with environmental systems are nijmerous. Design of gas cleaning absorption processes, waste water treatment facilities, low-emission combustion processes, and catalytic mufflers are typical problems. 

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