Yields and product distributions

Process development with particular attention to process profitability and safety and minimization of the environmental impact is presented in Chapter 5. A brief description of the present practice in scale-up, development, and production planning is given and the most promising trends and achievements are presented. Recommendations are given how to achieve success in the scale-up of a process a successful scale-up can be defined as the procedure that allows the same yields and product distribution in a full-scale plant as on a small scale. 

TABLE 31. Yields and product distributions in the reaction of 534 with 535... 

The yields and product distribution obtained in delayed coking are functions of the character of the feed stock and the operating conditions. Gas oil yields of 60 to 85 volume % with coke yields of 10 to 30 weight % of the feed are reasonably representative 5). 

The water-soluble Ru(II) complex [Ru(i76-C6H6)(CH3CN)3](BF4)2 catalyzed the biphasic hydrogenation of alkenes and ketones with retention of the catalyst in the aqueous phase (87). However, the ruthenium complex moved to the organic phase when benzaldehyde was hydrogenated. In a benzene-D20 system, H-D exchange was observed between H2 and D20. Both monohydridic pathway and a dihydridic pathway are possible for hydrogen activation, and these two different catalytic cycles influence the yield and product distribution. 

The lifetimes of the BRs are of critical importance to any attempt at quantitative analysis of the factors which will determine quantum yields and product distributions (E/C and t/c ratios) in Type II reactions of ketones under various reaction conditions. Virtually all information about lifetimes is derived from study of triplet BRs and much of it has been provided, and reviewed, by Scaiano [261]. There are many interesting reactions, both bimolecular and unimolecular, which occur at only one of the radical centers but they have little relevance to this chapter and are not discussed here. BR triplets derived from alkanophenones have lifetimes of 25-50 ns in hydrocarbon solvents. They are lengthened several fold in t-butyl alcohol and other Lewis bases capable of hydrogen bonding to the OH groups of the BRs. The rates of decay are virtually temperature independent but are shortened by paramagnetic cosolutes such as 02 or NO. The quenchers react with the BRs... 

In commercial practice, the yield and product distribution in nitration of alkanes is controlled as far as possible by the judicious addition of catalysts (e.g., oxygen and halogens), which are believed to raise the concentration of alkyl radicals. The products are separated from the mixtures by fractional distillation. 

Table I. Mean quantum yields and product distribution for the dehydrogenation of the alcohols indicated (catalyst ...

For greater detail of the influence of reaction conditions and substrate structures on yields and product distributions the original papers and a review (33) should be consulted. 

The total volatile matter yield, and hence the yield of tar plus light oils, is proportional to the hydrogen-to-carbon ratio in the raw material. On the other hand, the chemically formed water vapor that distills off during pyrolysis in an inert atmosphere is proportional to the oxygen-to-carbon ratio. The yields and product distributions also depend on the rate of pyrolysis. 

The resulting noncovalently immobilized complexes have been used as ligand systems for both the Pd-catalyzed allylic amination reaction and the Rh-catalyzed hydroformylation. A glycine-urea functionalized PPh3 ligand, 4(S), was noncovalently attached to the immobilized dendritic support, and the application of this system in the Pd-catalyzed allylic amination attains similar yields and product distributions as the homogeneous analogue for the... 

Table II shows the yields and product distribution in a Dimersol Unit charging 3803 BPSD of mixed C3 s containing 2700 BPSD propylene. The conversion level on propylene is 957o.

Overall yields and product distributions obtained in experiments using CH3CI, CH2CI2, and C2H5CI are shown in Table 3. The overall trends of reactivities obtained with various coinitiators at various... 

Temperature significantly affects the relative rates of reactions and consequently the final yields and product distributions. 

YIELD AND PRODUCT DISTRIBUTIONS FROM THE CHLORINATION OF AROMATIC COMPOUNDS IN TRIFLUOROACETIC ACID ... 

Yields and product distribution strongly depend on the nature of the ligand L where L is a phosphane or phosphite (cf. Table 1). With the bulky phosphane P(iPr)2(tBu) only 6% of the 1,2-addition products 4 and 5 are obtained, the main products being 2 1 cyclocotrimers 6 of 3,3-dimethylcyclopropene and methyl acrylate (see p. 85). 

Perhalogenated cyclopropenes, such as 1,2,3,3-tetrachlorocyclopropene, are similarly converted into a copper carbenoid species with copper(I) chloride at 110-130°C. The intermediate can then be trapped with various alkenes to yield l-chloro-l-(trichloroethenyl)cyclopropanes in moderate to good yields.Yields and product distributions are often comparable to those obtained in thermal reactions. 

Only a limited number of vinyl sulfones, e.g. phenyl ( )-2-phenylvinyl sulfone (14), undergo codimerization with MCR Homocyclodimerization of MCP is the most efficient side reaetion. Interestingly, yields and product distributions are solvent dependent. No reaction takes place with catalytic amounts of bis(t -cycloocta-l,5-diene)nickel(0)/triphenylphosphane. In this case the vinyl sulfones are strongly coordinated to the catalyst metal, thus preventing interaction with MCP. When the sulfones bear alkyl-substituted vinyl groups, isomerization to yield allyl sulfones usually proceeds faster than cycloaddition, at least in the case of palladium(O) catalysis. 

TABLE 5 Quantum Yields and Product Distributions in Photolysis of Triphenylsulfonium Triflate in AN 82a]... 

Koll and Metzger (1978) report on the use of supercritical acetone as the reaction medium for the thermal degradation of cellulose and chitin. Since the pyrolysis of these polysaccharides occurs at such high temperatures, it is necessary to remove the primary products from the reaction zone as soon as they are formed to avoid degradation of the products into coke. The high operating temperature also adversely affects both yield and product distribution. It is possible to reduce the carbon formation by carrying out the pyrolysis under vacuum but the reaction rate is also reduced because of the poor heat transfer to the reactants. 

Yields and product distribution are closely related to the composition of the reaction medium. High selectivity, relative to both phenol and hydrogen peroxide, designates acetone and methanol as the solvents of choice. Catechol/hydroquinone ratio varies in the range 0.5-1.3, well removed from the statistical distribution, owing to the shape selectivity of TS-1. Hydroquinone formation predominates in methanol, whereas the reverse occurs in acetone or acetone-water mixtures. At elevated phenol concentrations, however, even in the presence of methanol the catechol/hydroquinone ratio can approach unity [9]. In acetonitrile and 2-butanone, kinetics and selectivity were both significantly reduced [12], However the nature of the TS-1 used in this study has been the subject of some disputes [8,13]. 

Some catalysts were discarded in a day. When others looked of interest, gasoline yield and product distribution by weight were determined accurately. The gasoline produced was tried for antiknock value in a racing car and, to test for stability, was exposed to sun rays. 

The reaction of ethylene oxide with aqueous ammonia to form ethanol-amines is an example of a process where the kinetics of product distribution is most important. In this process, the reaction is fast and the reactor required is very small compared to the separation and finishing equipment needed in the process. For this reason the absolute rate of reaction is of minor importance. The relative rates of the reactions to form mono-, di-, or triethanolamine are extremely important for economic yield and product distribution. 

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