Quantitative high temperature conversion

These dynamic results provide graphic and quantitative proof that CSTRs designed for high conversions and/or low temperature are easier to control and provide tighter temperature control than are CSTRs that are designed for low conversion and/or high temperature. 

The Newman-Kuart rearrangement is an example of a high-temperature reaction [34]. With the use of a microreactor, the reaction temperature could be extended up to 200 °C. 0-(2-Nitrophenyl)-N,N-dimethylthiocarbamate was converted to S-(2-nitro-phenyl)-N,N-dimethylcarbamothioate at 170 °C in 14 min at 90% yield. Quantitative conversion with a throughput of 34 g/h was achieved with sulfolane as solvent at the same temperature and reaction time. 

This new benzyne precursor combines practical facility in its preparation with relative stability and safety in handling in addition, its conversion into benzyne does not require a strong base or high temperature. Another useful feature of this methodology is that, as with substituted diphenyliodonium 2-carboxylates, only one aryne can be formed from substituted precursors. Indeed, two methyl analogues of 2-trimethylsilyl-diphenyliodonium triflate, in the presence of furan, afforded quantitatively the corresponding adducts high yields of benzyne-diene adducts were also obtained with other 1,3-dienes. 

The oxidation of olefinic substrates with rert-butylhydroperoxide (TBHP) and various metal catalysts in SCCO2 has been investigated [15,77-79]. For simple cyclic alkenes, [Mo(CO)6] (18) proved by far the most active catalyst (Scheme 4.7-15), one reason being the high solubility of the complex. Quantitative conversion and high selectivity for the epoxide was observed in case of cyclic alkenes such as cyclooctene or cyclohexene with 2 mol% of catalyst when TBHP solutions in water or hydrocarbons were used at temperatures below 90 °C [15,79]. With aqueous TBHP solutions at temperatures above 90°, the reaction was found to produce the trans-1,2-diols via hydrolysis of... 

DOC analysers on the market at the time of purchase, operate based on two different principles A) high temperature oxidation over a catalyst followed by measurement of the evolved CO 2 by infra-red photometry, or after conversion to methane, by flame ionisation detection, and B) wet oxidation of organic carbon by the action of UV light in the presence of potassium persulphate. The CO2 produced is stripped from solution and reduced to methane which is measured quantitatively by flame ionisation detection. 

The particular temperatures at which peaks are observed can be used for the identification of components in a mixture, and the size of a particular peak can be used for quantitative evaluation. Examples include the determination of quartz in clays and analysis of the constituents of polymer blends, both of which would be difficult to achieve by other means. DTA has been used to determine the presence and degree of conversion of high-alumina cement concrete (HAC), a material subject to severe loss of strength under certain atmospheric conditions due to solid-state reactions in the cement matrix. Figure 9 shows a DTA curve for partially converted HAC together with the way the data are used for a conversion measurement. 

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