Yield enhancement

All process objectives including cost effectiveness, yield enhancement, energy conservation, and environmental acceptability. 

Aciylonitrile production has increased from 3.9 kg/s to 4.6 kg/s, which corresponds to an 18% yield enhancement for the plant This production increase is a result of better allocation of process streams the essence of mass integration. For a selling value of 0.6/kg of AN, the additional production of 0.7 kg AN/s can provide an annual revenue of 13.3 million/yr ... 

Under high pressure, the reaction favors the formation of kinetic adducts (10) and (11) with precursor (6). Further regioselectivity and yield enhancement could be achieved with the bidentate phosphite ligand tpdp (12) as illustrated in Scheme 2.3 [11]. 

In most work on electrochemical systems, use is made of two effects that greatly enhance the Raman signals. One is resonance Raman spectroscopy (RRS), wherein the excitation wavelength corresponds to an electronic transition in an adsorbed molecule on an electrode surface. The other effect is surface-enhanced Raman spectroscopy (SERS), which occurs on certain surfaces, such as electrochemically roughened silver and gold. This effect, discovered by Fleischmann et al. (1974), yields enhancements of 10 to 10 . The vast majority of publications on Raman studies of electrochemical systems use SERS. The limitations of SERS are that it occurs on only a few metals and the mechanism of the enhancement is not understood. There is speculation that only a small part of the surface is involved in the effect. There is a very good review of SERS (Pemberton, 1991). 

Self-assembled structures can be closed if all the potential binding sites are utilized, or open if they are not. Closed assemblies have a definite geometry and stoichiometry, while open assemblies exist as mixtures of oligomers or polymers of varying stoichiometry. In addition, the self-assembled structure can be classified as cooperative if the multiple binding interactions reinforce each other to yield enhanced stability, or trivial if the binding interactions do not cooperate in the... 

Tuziuti T, Yasui K, Sivakumar M, Iida Y, Miyoshi N (2005) Correlation between acoustic cavitation noise and yield enhancement of sonochemical reaction by particle addition. J Phys Chem A 109 4869 1872... 

Which methods improve quantum convergence and which have better sampling It is not clear whether one can really separate these effects. For instance, one can have an improved method that is designed primarily to reduce P, but which also yields enhanced sampling. Thus, in the list of methods given above, we only state the primary reason for the apparent success of each of them. 

More recently [29] the microwave-mediated Biginelli dihydropyrimidine synthesis (Eq. 2) was reinvestigated using a purpose-built commercial microwave reactor with on-line temperature, pressure, and microwave power control. Transformations performed with microwave heating at atmospheric pressure in ethanol solution resulted in neither a rate increase nor an increase in yield when the temperature was identical to that used for conventional thermal heating. The only significant rate and yield enhancements were found when the reaction was performed under solvent-free conditions in an open system. 

Quite recently this reaction was revisited by Kappe [91] et al. who reinvestigated the Biginelli synthesis under the action of microwave irradiation under a variety of different conditions. At atmospheric pressure in ethanol solution there is no difference from conventional heating. Under pressure the yield is reduced and byproducts are formed. In an open system rate and yield enhancements are significant and this is rationalized by the rapid evaporation of the solvent which means that this is in fact a solvent-free reaction. This was confirmed by running the reaction without solvent under the action of microwaves and with thermal heating. (Scheme 8.65)... 

Comparison of this reaction with that performed using classical heating shows an acceleration of the 1,3-dipolar cycloaddition upon irradiation and yield enhancements for the synthesis of imidazolones 122. These advantages occur by virtue of diminished formation of the byproduct 125 (see Scheme 9.37). 

The reactions were performed under a steady stream of nitrogen to aid the removal of ethene from the reaction mixture. Changing from a static nitrogen atmosphere to this flow of nitrogen resulted in a 30% yield enhancement and appeared to extend the life of the catalyst. 

The efficacy of anticholinergic drugs in parkinsonism is likely due to the ability to block muscarinic receptors in the striatum. In the absence of the inhibitory action of dopamine, the actions of the intrastriatal cholinergic interneurons are unopposed, yielding enhanced stimulation of muscarinic receptors. Blockade of these receptors reduces striatal activity. The muscarinic antagonists exert only modest antiparkinsonian actions and thus are most commonly used during the early stages of the disease or as an adjunct to levodopa therapy. 

HS(CH2)2COOH. Addition of the thiol yields enhanced anodic peak current, but at very high thiol concentrations, the catalytic activity is suppressed, consistent with the inner-sphere oxidation of the thiol. The carboxylic acid group was shown to be important for the reaction in a position 2 or 3 bonds away from the SH group. 

In some studies, retardants have been implicated in yield enhancement mediated by the manipulation of crop canopy structure and the removal of dominance characteristics, leading to a more uniform crop and potentially higher yields. Senescence may be delayed. Although the maintenance of green tissue is a clear advantage with respect to yield production, prolonged seasons can expose the crop to damaging episodes of adverse weather and counteract the potential benefits of PGR treatment. 

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