Overheating reactions

While the sodium ethoxide solution is cooling, prepare a solution of 7 7 g. of finely powdered iodine in 60 ml. of ether. When this solution is ready, add 9 ml. (9 6 g.) of ethyl malonate to the ethanolic sodium ethoxide solution, mix w ell and then allow to stand for 30-60 seconds not longer) then cautiously add the ethereal solution of the iodine, mixing thoroughly during the addition in order to avoid local overheating by the heat of the reaction. (If, after the ethyl malonate has been added to the sodium ethoxide, a considerable delay occurs before the iodine is added, the yield of the final product is markedly decreased.)... 

This route to acid chlorides is often preferred over the alternative use of phosphoms trichloride because the by-products, SO2 and HCl, are gaseous and easily removed. On the other hand, the use of phosphoms trichloride yields phosphorous acid as a by-product. This can decompose exothermically with evolution of toxic and flammable phosphine if overheated, however, phosphorous acid is saleable as a valuable by-product on a commercial scale. Ma.nufa.cture. Thionyl chloride may be made by any of the following reactions ... 

Despite all these safeguards to extend the service life of the antifreeze, fluid replacement is requited periodically. Typically, fluids are replaced because of irreversible damage caused by one of four conditions contamination, gel formation because of glycol/siUcate reaction, extensive glycol degradation caused by overheating or excessive oxygen exposure, or inhibitor depletion. 

The oxychlorination reaction is very exothermic and the catalyst is very active, which makes it necessary to mix the catalyst with an inert diluent to avoid overheating in a fixed-bed reactor. A low surface area, spherically- or ring-shaped alumina or chemical porcelain body can be used as a diluent with the ring-shaped catalyst. The density of the inert material should be similar to the catalyst to avoid segregation during loading, and the size should be slightly different to allow separation of the inert material from the spent catalyst. 

Treatment of thermal conductivity inside the catalyst can be done similarly to that for pore diffusion. The major difference is that while diffusion can occur in the pore volume only, heat can be conducted in both the fluid and solid phases. For strongly exothermic reactions and catalysts with poor heat conductivity, the internal overheating of the catalyst is a possibility. This can result in an effectiveness factor larger than unity. 

The chlorosilanes are dissolved in a suitable solvent system and then blended with the water which may contain additives to control the reaction. In the case of methylsilicone resin the overall reaction is highly exothermic and care must be taken to avoid overheating which can lead to gelation. When substantial quantities of chlorophenylsilanes are present, however, it is often necessary to raise the temperature to 70-75°C to effect a satisfactory degree of hydrolysis. 

The submitters report that the purity of the product is rather dependent upon the purity of the lithium used and that results can vary from batch to batch. In addition, they state that side reactions may be catalyzed by traces of heavy metals, that the degree of vigor in the initial reaction may influence the purity of the product owing to local overheating, and that increase in scale of this reaction is deleterious. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May ignite or explode spontaneously when mixed with combustible materials Stability During Transport Stable if not overheated Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Overheating can result in overpressure due to reduction of allowable stress. Therefore, flie design must include monitoring and control features to prevent the occurrence of decompositions and runaway reactions, since conventional pressure reheving devices cannot normally provide protection against these contingencies. 

The cyanide reactor is critical because of the high temperatures dial arc iinoh cd. Overheating tlie reactor could result in uncontrollable combustion reactions or explosions." These uncontrollable combustion reactions or explosions could result in the physical breakdown of the reactor vessel by... 

Hot spot formation witliin tlie reactor can result in catalyst breakdown or physical deterioration of tlie reactor vessel." If tlie endothermic cyanide reaction has ceased (e.g., because of poor catalyst performance), the reactor is likely to overheat. Iron is a decomposition catalyst for hydrogen cyanide and ammonia under the conditions present in the cyanide reactor, and e. posed iron surfaces in the reactor or reactor feed system can result in uncontrolled decomposition, which could in turn lead to an accidaital release by overheating and overpressure. 

Twenty-five grams (0.212 mole) of 3-sulfolene, and 15.0 g (0.153 mole) of pulverized maleic anhydride are added to a dry 250-ml flask fitted with a condenser. Boiling chips and 10 ml of dry xylene are added. The mixture is swirled gently for a few minutes to effect partial solution, then gently heated until an even boil is established. During the first 5-10 minutes, the reaction is appreciably exothermic, and care must be exercised to avoid overheating. 

Deposit control is important because porous deposits, under the influence of heat flux, can induce the development of high concentrations of boiler water solutes far above their normally beneficial bulk values with correspondingly increased corrosion rates. This becomes an increasingly important feature with increase in boiler saturation temperature. In addition, deposits can cause overheating owing to loss of heat transfer. Finally, carryover of boiler water solutes, which can be either mechanical or chemical, can lead to consequential corrosion in the circuit, either on-load or off-load. Material so transported can result in corrosion reactions far from its point of origin, with costly penalties. It is therefore preferably dealt with by a policy of prevention rather than cure. 

This closeness of 0 to zero explains the existence of a gas-oversaturated solution area in the polymer melt, when P < Pg, but the entire volume of gas remains in the solution. The degree of oversaturation, particularly upon free foaming (not in flow) can be 2- to 3-fold. In real polymer compositions, there are always solid admixtures, which have poor wetting areas. This reduces the degree of oversaturation at the interface melt-molding tool. Moreover, bubble nuclei can result from fragmentation of gas bubbles in the polymer [16]. Another factor that promotes the formation of bubble nuclei is the presence of localized hot points in the polymer melt they act as nuc-leation centres. Hot points appear either after a chemical reaction in the melt polymer [17], or in overheated areas on the surface of metal equipment [18]. Density of nucleation can be improved via introduction of various agents that reduce tension of the polymer [19]. 

During oxidn of mesitylene with nitric acid in an autoclave at 115° to give 3,5-dimethylbenzoic acid, a violent expln occurred. The reaction was attributed to local overheating, formation of a trinitro compd, 1,3,5-tri (nitromethyl) benzene, and to violent decompn of the latter. Smaller scale prepns with better temp control were uneventful (Ref 3)... 

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