Serial reactions

The catalyst performance depends on the H2 to CCI2F2 feed ratio. The selectivities to CH2F2 and CHCIF2 are influenced by the H2 to CCI2F2 feed ratio, while the selectivity to methane is independent of this ratio. We have previously proposed a reaction mechanism with serial reactions on the catalyst surface and minor readsorption of the intermediate products, which is depicted in figure 8 [4,5]. Thus the kinetics of the reaction follows mainly parallel reaction pathways, in which the selectivities are not influenced by the conversion, and a... 

Thus it is clear from both the remarkable constant selectivity to methane and the influence of addition of methane on the selectivities to CHCIF2 and CH2F2, that the serial reaction mechanism has to be modified in order to explain the observed phenomena. Therefore, more measurements will be performed in order to determine the adsorption of CFCs on the metal surface and the influence of other products, such as CH2F2 and HCl on the catalyst performance [11]. 

Reactive distillation is one of the classic techniques of process intensification. This combination of reaction and distillation was first developed by Eastman Kodak under the 1984 patent in which methyl acetate was produced from methanol and acetic acid. One of the key elements of the design is to use the acetic acid as both a reactant and an extraction solvent within the system, thereby breaking the azeotrope that exists within the system. Likewise, the addition of the catalyst to the system allowed sufficient residence time such that high yields could be obtained, making the process commercially viable. Other examples in which reactive distillation may enhance selectivity include those of serial reactions, in which the intermediate is the desired product, and the reaction and separation rates can be systematically controlled to optimize the yield of the desired intermediate. ... 

Carli M, Samanin R. (1992). Serotonin2 receptor agonists and serotonergic anorectic drugs affect rats performance differently in a five-choice serial reaction time task. Psychopharmacology (Berlin). 106(2) 228-34. 

Koskinen, T, Ruotsalainen, S., Puumala, T., Lappalainen, R., Koiv-isto, E., et al. (2000) Activation of 5-HT2A receptors impairs response control of rats in a five-choice serial reaction time task. Neuropharmacology 39 471-481. 

Muir JL, Dunnett SB, Robbins TW, et al Attentional functions of the forebrain cholinergic systems effects of intraventricular hemichohnium, physostigmine, basal forebrain lesions and intracortical grafts on a multiple-choice serial reaction time task. Exp Brain Res 89 611-622, 1992 Mukherjee S Mechanisms of the antimanic effect of electroconvulsive therapy. Convulsive Therapy 5 227-243, 1989... 

In complex reaction systems the conversion of reactants to products typically takes place through a number of parallel and serial reactions. The reaction path from a reactant through a number of intermediates to the final product naturally occurs in a series of steps. The overall conversion rate and the peak concentrations of the intermediates will depend on the relative rates of the serial reactions. 

In view of the appreciable number of SE s involved in reaction (9.25), distinct serial reaction steps can be anticipated. Steps in which the electron hole is involved are assumed to be fast compared to steps involving ionic SE s (in line with the fact that >h > Dj). Thus, the (locally homogeneous) Frenkel reaction becomes rate determining for the overall internal process described by Eqn. (9.25). The Frenkel reaction is bimolecular. The rate equation for the formation of Frenkel defects is, according to standard kinetics,... 

Bjemer B. Alpha depression and lowered pulse rate during delayed actions in a serial reaction test a study of sleep deprivation. Aviat Space Environ Med 1949 6 233-235. 

Sustained Attention Five-Choice Serial Reaction lime Task... 

Chudasama Y, Robbins TW. Psychopharmacological approaches to modulating attention in the five-choice serial reaction time task implications for schizophrenia. Psychopharmacology 2004 174 86-98. 

Robbins TW. The 5-choice serial reaction time task behavioural pharmacology and functional neurochemistiy. Psychopharmacology 2002 163 362-380. 

Three other main test paradigms have been used that appear to expose the possible attentional dysfunction following manipulations of DA-ergic function latent inhibition prepulse inhibition and continuous performance (the five-choice serial reaction time task) - all notable for their correspondence to similar tests for human subjects. Curiously, the main emphasis of these investigations has been on mesolimbic rather than mesostriatal systems. 

Cole BJ, Robbins TW (1987) Amphetamine impairs the discriminative performance of rats with dorsal noradrenergic bundle lesions on a 5-choice serial reaction-time-task New evidence for central DA-ergic-noradrenergic interactions. Psychopharmacology 97(4) 458-466. 

Cole BJ, Robbins TW (1989) Effects of 6-hydroxydopamine lesions of the nucleus accumbens septi on peformance of a 5-choice serial reaction-time task in rats Implications for theories of selective attention and arousal. Behav Brain Res 33 165-179. 

Robbins TW (2002) The 5-Choice Serial Reaction Time Task Behavioural pharmacology and functional neurochemistry. Psychopharmacology 763 362-380. 

The metabolic network described by this matrix is simplified in the following ways. First, in some cases several reactions are lumped together when the network is so constrained that the fluxes through the combined reactions are the same in a steady state. For example the reaction of the third column in the matrix (labeled G6PDH ) is actually the combination of two serial reactions... 

Typical results are given in Fig. 9. It is clear that styrene reacts away at the highest rate simultaneously with the disappearance of styrene, ethylbenzene is formed. The subsequent reaction of ethylbenzene into cthylcyclohexane does not proceed at a measurable rate. The isomerization of 1-octene into internal olefins is slower than the hydrogenation of styrene but faster than the hydrogenation into octane. The serial reaction network for the isomerizations is clear from Fig. 10. They all go through a maximum in agreement with serial kinetics. As expected, the maxima occur in the sequence 2-octene < 3-octene < 4-octene. 

Type III selectivity is that found with serial reactions such as the hydrogenation of an acetylene first to an alkene and then to the alkane (Eqn. 5.9).33 In such reactions the transport of the organic substrate through the... 

The ORR is a multielectron reaction that may include a number of elementary steps involving different reaction intermediates. The detailed mechanism is still not known, since neither ex situ nor in situ techniques are capable of identifying all reaction intermediates formed under genuine reaction conditions exist. Of the various possibilities [13], it has been proposed that on metal surfaces the most plausible reaction pathway for the ORR in both alkaline and acidic electrolytes can be described by the so-called serial reaction pathway (Scheme 3.1) where after the transfer of two electrons and (simultaneous) fast protonation of superoxo/peroxo radicals (not included in the reaction scheme), O is reduced to H O (with rate constant k. ... 

Scheme 3.1 Serial reaction pathway for oxygen reduction reaction...

Besides activity and selectivity, stability is crucial in catalysis applications. Catalyst deactivation can have a kinetic origin. For instance, deactivation might occur by a serial reaction mechanism in which an intermediate can undergo a reaction to form a substance that is a poison for the active catalyst sites. Frequently encountered examples are oligomerization and coke formation. 

Since tandem reactions first appeared they have been given many diverse names such as cascade, consecutive, and coupled processes, domino reactions, interrupted polymerisation, one-pot, sequential and serial reactions, and tactical combinations. Some authors have tried to classify... 

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