Influencing factors reaction time

In this paper we formulated and solved the time optimal problem for a batch reactor in its final stage for isothermal and nonisothermal policies. The effect of initiator concentration, initiator half-life and activation energy on optimum temperature and optimum time was studied. It was shown that the optimum isothermal policy was influenced by two factors the equilibrium monomer concentration, and the dead end polymerization caused by the depletion of the initiator. When values determine optimum temperature, a faster initiator or higher initiator concentration should be used to reduce reaction time. 

The application of the fluorescence derivatization technique in an HPLC method involves utilization of a post column reaction system (PCRS) as shown in Figure 3 to carry out the wet chemistry involved. The reaction is a 2-step process with oxidation of the toxins by periodate at pH 7.8 followed by acidification with nitric acid. Among the factors that influence toxin detection in the PCRS are periodate concentration, oxidation pH, oxidation temperature, reaction time, and final pH. By far, the most important of these factors is oxidation pH and, unfortunately, there is not one set of reaction conditions that is optimum for all of the PSP toxins. The reaction conditions outlined in Table I, while not optimized for any particular toxin, were developed to allow for adequate detection of all of the toxins involved. Care must be exercised in setting up an HPLC for the PSP toxins to duplicate the conditions as closely as possible to those specified in order to achieve consistent adequate detection limits. 

Cellulase and all chemicals used in this work were obtained from Sigma. Hydrolysis experiments were conducted by adding a fixed amount of 2 x 2 mm oflSce paper to flasks containing cellulase in 0.05 M acetate buffer (pH = 4.8). The flasks were placed in an incubator-shaker maintained at 50 °C and 100 rpm. A Box-Behnken design was used to assess the influence of four factors on the extent of sugar production. The four factors examined were (i) reaction time (h), (ii) enzyme to paper mass ratio (%), (iii) amount of surfactant added (Tween 80, g/L), and (iv) paper pretreatment condition (phosphoric add concentration, g/L), as shown in Table 1. Each factor is coded according to the equation... 

Establishing the process sensitivity with respect to the above-mentioned factors is crucial for further scale-up considerations. If the sensitivity is low, a direct volume scale-up is allowed and the use of standard batch reactor configurations is permitted. However, many reactions are characterized by a large thermal effect and many molecules are very sensitive to process conditions on molecular scale (pH, temperature, concentrations, etc.). Such processes are much more difficult to scale up. Mixing can then become a very important factor influencing reactor performance for reactions where mixing times and reaction times are comparable, micromixing also becomes important. 

The Effect of Reaction Time. The problem associated with time-varying OH concentrations has already been mentioned. The difficulty associated with the influence of dissolved C02 can be appreciated by referring to Figure 4, which shows the results of two experiments. In one, samples were taken every hour and in the other sampling occurred every two hours. However, the important factor is that the reactor was recharged with CO after each sample Note that the effective reaction rate is lower when two hours elapse between samples, presumably due to the buildup of C02, which consumes OH . In fact, one experiment was conducted at 94°C for 17 hours and only 27% conversion to alcohol occurred, the same conversion experienced after 3 hours when fresh CO was added hourly. 

The more we know about what is occurring during reaction, what the reacting materials are, and how they react, the more assurance we have for proper design. This is the incentive to find out as much as we can about the factors influencing a reaction within the limitations of time and effort set by the economic optimization of the process. 

The unified approach adopted by Ma ek assumed that all initiations are ultimately thermal. More precisely every initiating stimulus (shock, impact, electric discharge, friction, etc) serves to heat up the explosive or a portion thereof, initially at a temperature T to an elevated temperature T. It is assumed that T and the length of time t the explosive is exposed to T are the two variables sufficient to account for initiation. The 3rd factor influencing the reaction rate, density p, is important in gaseous combustions and explosions where it varies considerably with temperature and pressure in homogeneous solids and liquids it is nearly constant... 

Although delayed larger utilities are obviously discounted, the influence of the time factor is more complicated. While the initial heroin high lasts a certain period, the effects of repeated drug intake complicate the picture. Through homeostatic neuroadaptation, the utility of heroin use in itself diminishes. It is the state without heroin that seems unattractive. At first, this is caused by abstinence reactions through neuroadaptation to the secondary effects. After these have diminished, post-use anhedo-nia by adaptation to the primary, core effects might cause most utilities to be devalued, whether present or distant. The devaluation may persist not only for days but for months or years. 

All the work described in this section thus has a common theme inasmuch as it deals with the influence of various environmental factors on the activity of homogeneous oxidation catalysts. In particular, the results shed valuable light on the ways in which temperature, the structure of the organic substrate, the concentration and the form of the catalyst, and reaction time may all affect the nature and kinetics of the various competing stages involved in the reaction of organic compounds with molecular oxygen. 

The reaction (keeping warm) time (Factor B) exhibits little influence on the mean size of the product, but significantly affects the yield of titanium. However the direction of the influence is somewhat unexpected the longer the reaction time, the lower is the yield of Ti. This indicates that re-dissolution of the precipitate obviously occurred, but, as yet, the phenomenon is difficult to explain exactly or reasonably and further investigation is needed. After all, the reaction mixture is very complex. 

Those which do occur, their rates, and routes, depend on a complicated balance between the influences of many factors. Major among these are temperature, reaction time, other constituents in the environment, physical state, and molecular organization. Indeed, studies with model systems are invaluable, however, perfect simulation of the natural situation is practically impossible. The model and the real systems are still far apart and much more research is required with both to better understand the wide gap in between. 

An important difference between solution-phase and solid-phase chemistry is the new variable the polymer support. The polymer has significant influence on the reaction. There have been many solid supports used over the years with variation in polymer type, degree of cross-linking, and even quality. These factors have significant influence on solvation properties and reaction kinetics, and hence on synthesis characteristics. Various grafted polymers may have characteristics that differ from other supports. Consequently, the optimal conditions for a reaction on one polymer may be different from those for the same reaction on a different polymer. This should not dishearten the chemist. A reported reaction may be used as the basis for optimization studies of the reaction on a different support. Variables such as solvent, temperature, and reaction time may all be investigated to optimize the reaction on the new surface. 

The rate constant k is independent of the concentration, but temperature dependent, the details are described in Section 4.1.1.3.3. n is the reaction order. For elementary reactions, it is the stoichiometric coefficient a. However, if the studied reaction is not an elementary reaction, the order of the reaction does not relate to the stoichiometric factors anymore. Moreover, the reaction order can then be a fractional number and it usually does not have a physical meaning. Nevertheless, the reaction order has a strong influence on the time dependent development of the concentration of the reactants, disregarding if it is an elementary reaction or not. 

The synthesis of zeolite A, mixtures of A and X, and zeolite X using batch compositions not previously reported are described. The synthesis regions defined by triangular coordinates demonstrate that any of these materials may be made in the same area. The results are described in terms of the time required to initiate crystallization at a given reaction temperature. Control of the factors which can influence the crystallization time are discussed in terms of "time table selectors" and "species selectors . Once a metastable species has preferentially crystallized, it can transform to a more stable phase. For example, when synthesis conditions are chosen to produce zeolite A, the rate of hydroxysodalite formation is dependent on five variables. These variables and their effect on the conversion of zeolite A to hydroxysodalite are described mathematically. 

At this point, we have to verify the eorreetness of the selection of the unification relations. When S sSint we can conclude that our selection for the unification relations is good in this case, we can also note that the calculations have been made without errors. Otherwise, if computation errors have not been detected, we have to observe that the selected interactions for the unification of blocks are strong and then they carmot be used as unification interactions. In this case, we have to carry out a new experimental research with a new plan. However, part of the experiments realized in the previous plan can be recuperated. Table 5.68 contains the synthesis of the analysis of the variances for the current example of an esterification reaction. We observe that, for the evolution of the factors, the molar ratio of reactants (B) prevails, whereas all other interactions, except interaction AC (temperature-reaction time), do not have an important influence on the process response (on the reaction conversion). This statement is sustained by all zero hypotheses accepted and reported in Table 5.68. It should be mentioned that the alcohol quality does not have a systematic influence on the esterification reaction efficiency. Indeed, the reaction can be carried out with the cheapest alcohol. As a conclusion, the analysis of the variances has shown that conversion enhancement can be obtained by increasing the temperature, reaction time and, catalyst concentration, independently or simultaneously. 

Intaestingly, this results suggests that TCE conversion, x, was apparently influenced only by reaction time r, not by ozone concentration, which dif finm the bulk reaction directly influenced by ozone concentration [Hoigne et al, 1983 ]. This suggests that thoe will be conclusive factors that have a strongly effect on the apparent reaction behavior, indqiendent of the characteristics of the adsoibent nature. Thus, the effect of otho flictors such as particle size (binder... 

For some pesticide compounds, such as dini-troaniline herbicides (Weber, 1990), phototransformation occurs primarily in the vapor phase, rather than in the dissolved or sorbed phases. Perhaps the most environmentally significant pesticide phototransformation in the atmosphere, however, is the photolysis of the fumigant methyl bromide, since the bromine radicals created by this reaction are 50 times more efficient than chlorine radicals in destroying stratospheric ozone (Jeffers and Wolfe, 1996). Detailed summaries of the rates and pathways of phototransformation of pesticides and other organic compounds in natural systems, and discussions of the physical and chemical factors that influence these reactions, have been presented elsewhere (e.g., Zepp et al, 1984 Mill and Mabey, 1985 Harris, 1990b). 

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