Product distribution Yield

Many researchers have correlated the overall decomposition as an nxh. order reaction, with most paraffins following the first order and most olefins following a higher order. In general, isoparaffin rate constants are lower than normal paraffin rate constants. The rate constants are somewhat dependent on conversion due to inhibition effects that is, the rate constant often decreases with increasing conversion, and the order of conversion is not affected. This has been explained by considering the formation of aHyl radicals (38). To predict the product distribution, yields are often correlated as a function of conversion or other severity parameters (39). 

The Pacman catalyst selectively oxidized a broad range of organic substrates including sulfides to the corresponding sulfoxides and olefins to epoxides and ketones. However, cyclohexene gave a typical autoxidation product distribution yielding the allylic oxidation products 2-cyclohexene-l-ol (12%) and 2-cyclohexene-1-one (73%) and the epoxide with 15% yield [115]. 

Silane Temp ro Catalyst Product Distribution Yield (%)... 

Scheme 27 Comparison of the product distribution (yields in parenthesis) for the Heck reaction between diiodobenzene and w-butyl acrylate using dendrimer complexed and monomeric catalyst ...

Olefin Hydroborating agent Ratio of olefin Reaction Reaction to hydroborat- temperature time (h) ing agent (°C) Total Product distribution yield (%) Boron distribution (%) a p ... 

The major operating variables that affect the product distribution (yield) of the HCR process are the reactor temperature, hydrogen partial pressure, amount of ammonia present, and residence time. This section uses the MP HCR model to illustrate how to quantify the effects of operating variables on process performance. 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

Electrophilic addition to quinones, eg, the reaction of 2-chloro-l,4-ben2oquinones with dia2onium salts, represents a marked contrast with acetoxylation in product distribution (58). Phenyldia2onium chloride (Ar = C H ) yields 8% 2,3-substitution [80632-59-3] 75% 2,5-substitution [39171-11-4] and 17% 2,6-substitution [80632-60-6]. Fory)-chlorophenyldia2onium chloride, the pattern is 28% 2,3-substitution [80632-61-7], 35%... 

Nonicosahedral carboranes can be prepared from the icosahedral species by similar degradation procedures or by reactions between boranes such as B H q and B H with acetylenes. The degradative reactions for intermediate C2B H 2 species (n = 6-9) have been described in detail (119). The small closo-Qr Yi 2 species (n = 3-5 are obtained by the direct thermal reaction (500—600°C) of B H using acetylene in a continuous-flow system. The combined yields approach 70% and the product distribution is around 5 5 1 of 2,4-C2B3H2 [20693-69-0] to l,6-C2B Hg [20693-67-8] to 1,5-C2B3H3 [20693-66-7] (120). A similar reaction (eq. 60) employing base catalysts, such as 2 6-dimethylpyridine at ambient temperature gives nido-2 >-(Z, ... 

Experimental data taken from the chlorination of toluene in a continuous stirred tank flow reactor at 111°C and irradiated with light of 500 nm wavelength yield a product distribution shown in Table 1 (1). 

Table 6 shows the effect of varying coil oudet pressure and steam-to-oil ratio for a typical naphtha feed on the product distribution. Although in these tables, the severity is defined as maximum, in a reaUstic sense they are not maximum. It is theoretically possible that one can further increase the severity and thus increase the ethylene yield. Based on experience, however, increasing the severity above these practical values produces significantly more fuel oil and methane with a severe reduction in propylene yield. The mn length of the heater is also significantly reduced. Therefore, this is an arbitrary maximum, and if economic conditions justify, one can operate the commercial coils above the so-called maximum severity. However, after a certain severity level, the ethylene yield drops further, and it is not advisable to operate near or beyond this point because of extremely severe coking. 

In other work, these authors examined the product distribution for Eq. (2.3) as a function of ring size formed. Maximum yields for cyclic product were observed when a five-oxygen, seventeen-membered ring was formed. 

Chemical reactions often yield entirely different product distributions depending on the conditions under which they are carried out. In particular, high temperatures and long reaction times favor the most stable ( thermodynamic ) products, while low temperatures and short reaction times favor the most easily formed ( kinetic ) products. 

The major part of each chapter deals with mechanistic aspects however, for didactic reasons, in most cases not with too much detail. Side-reactions, variants and modified procedures with respect to product distribution and yields are described. Recent, as well as older examples for the application of a particular reaction or method are given, together with references to the original literature. These examples are not aimed at a complete treatment of every aspect of a particular reaction, but are rather drawn from a didactic point of view. 

The study of biochemical natural products has also been aided through the application of two-dimensional GC. In many studies, it has been observed that volatile organic compounds from plants (for example, in fruits) show species-specific distributions in chiral abundances. Observations have shown that related species produce similar compounds, but at differing ratios, and the study of such distributions yields information on speciation and plant genetics. In particular, the determination of hydroxyl fatty acid adducts produced from bacterial processes has been a successful application. In the reported applications, enantiomeric determination of polyhydroxyl alkanoic acids extracted from intracellular regions has been enabled (45). 

The FTS mechanism could be considered a simple polymerization reaction, the monomer being a Ci species derived from carbon monoxide. This polymerization follows an Anderson-Schulz-Flory distribution of molecular weights. This distribution gives a linear plot of the logarithm of yield of product (in moles) versus carbon number. Under the assumptions of this model, the entire product distribution is determined by one parameter, a, the probability of the addition of a carbon atom to a chain (Figure 4-7). ... 

Table 5-4 shows the product distribution, when methanol was reacted over different catalysts for maximizing olefin yield. 

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