Temperature effects on productivity

These results are in agreement with the literature results, especially with data concerning temperature effects on CO conversion.121619 20 In case of temperature effect on product distribution, there are many studies that, in apparent disagreement with what is presented here, report an increase of selectivity to the lighter products with increasing temperature. These data, however, are compatible with our results if one considers the narrow temperature interval (220-235°C) investigated in this study. 

The adoption of new hypotheses for the reactants adsorption, the removal of all the empiric laws and parameters, and a reevaluation of the temperature effect on product distribution have allowed us to obtain significant improvements with respect to our previous work,10 in terms of both fitting ability and model consistency. 

Clark, K.J., F.W. Chaplin, and S.W. Harcum. 2004. Temperature effects on product-quality-related enzymes in batch CHO cell cultures producing recombinant tPA. Biotechnol Prog 20 1888-1892. 

Figure 23.3 Temperature effects on product phase yields for the feed size range 150-75 xm. (Copyright 2003 from Polymer-Plastics Technology and Engineering by A Karaduman, M. C. Kocak and A. Y. Bilgesu. Reproduced by permission of Taylor Francis, Inc., http //www.taylorandfrancis.com)...

Figure 23.7 The temperature effects on product phase yields of PS. (Reproduced from Journal of Analytical and Applied Pyrolysis, 60 (2), A. Karaduman, Flash pyrolysis of polystyrene wastes in a free-fall reactor under vacuum, 179-186(2001), with permission from Elsevier)...

The reaction may produce both ortho and para acylated phenols, the former generally favored by high temperatures and the latter by low temperatures, (a) Suggest an experiment that might indicate whether the reaction is inter- or intramolecular, (b) Explain the temperature effect on product formation. 

Pleasantly, this kinetic modeling enables us to extract interesting features of this catalytic system, for example, platinum species distribution over time, catalyst loading or temperature effects on products distribution and reaction rates, and so on, thereby demonstrating its practical usefulness [16,23a]. 

Changes in surface temperature elsewhere in the globe are likely to have a lesser impact on carbon or DMS production. For example, the warming that a doubling of atmospheric COj could produce in the Southern Ocean has been modelled to lead to decreased carbon uptake, but enhanced biological productivity, due to the temperature effect on phytoplankton growth." This would lead to an approximately 5% increase in DMS production and a lesser increase in CCN. There is thus a negative feedback here, but only of minor impact. 

Taft equation, 229-230 Temperature, effect on rate, 156-160 Temperature-jump method, 256 Termination reaction, 182 Thermodynamic products, 59 Three-halves-order kinetics, 29... 

The effect of the temperature on the polymerization of 53 in methylene chloride is presented in Table 3. The upper half of the data in the table shows the temperature effect on the products in the initial stage of the reaction, and the lower half is that for the middle to final stages of the reaction. Obviously there is a drastic change in the reaction products between -20 and -30 ° Below —30 °C, the cyclic dimer is the predominant or even sole product after the reaction of 48 hours, while above —20 °C, the low molecular weight polymer is exclusively formed. The cyclic oligomers once formed in the initial stage of the reaction are converted to the polymer in the later stage of the reaction above —20 °C. 

The entropy of any chemical substance increases as temperature increases. These changes in entropy as a function of temperature can be calculated, but the techniques require calculus. Fortunately, temperature affects the entropies of reactants and products similarly. The absolute entropy of every substance increases with temperature, but the entropy of the reactants often changes with temperature by almost the same amount as the entropy of the products. This means that the temperature effect on the entropy change for a reaction is usually small enough that we can consider A Sj-eaction he independent of temperature. 

Andersen, J.N., "Temperature Effect on Recombinant Protein Production Using a Baculovirus/Insect Cell Expression System", Diploma Thesis, University of Calgary and Technical University of Denmark, 1995. 

Along with catalyst activity, product selectivity is a key issue in cobalt-based FTS.1 For GTL processes the preferred product is long-chain waxy hydrocarbons. It is well known that FT reaction conditions have an important effect on product selectivities. High temperatures and H2/CO ratios are associated with higher methane selectivity, lower probability of hydrocarbon chain growth, and lower olefinicity in the products.105... 

Also, concerning the effect of the temperature on the reaction rates, different assumptions were made here with respect to our previous work.10 In that case, only the hydrogen and CO adsorption were regarded as activated steps, in order to describe the strong temperature effect on CO conversion. In contrast, due to the insensitivity of the ASF product distribution to temperature variations (see Section 16.3.1), other steps involved in the mechanism were considered as non-activated. In the present work, however, this simplification was removed in order to take into account the temperature effect on the olefin/paraffin ratio. For this reason, Equations 16.7 and 16.8 were considered as activated. 

The introduction of alkyl phosphine complexes of cobalt carbonyl as hydroformylation catalysts was reported to have a significant effect on product composition (50, 51). Slaugh and Mullineaux (52) reported that hexanol with a 91% linear distribution was formed by the hydroformylation of 1-pentene at 150°C, 500 psi, H2/CO 2.0, catalyst [Co2(CO)8 + 2(n-C4H9)3P]. Under the same conditions except at a temperature of 190°C, the n-hexanol was 84% of the hexyl alcohol produced. 

Temperature effects on solubility products are readily assessed as most solubility reactions are clearly seen as endothermic and disorder increasing. Raising the temperature will thus increase Ksp together with the solubility of the solid. 

Hirano, A., Hon-Nami, K., Kunito, S., Hada, M., and Ogushi, T. (1998). Temperature Effect on Continuous Gasification of Microalgal Biomass Theoretical Yield of Methanol Production and its Energy Balance, Catalysis Today 45. pp. 399-404. 

Cano, M.P., Hernandez, A., and De Ancos, B. 1997. High pressure and temperature effects on enzyme inactivation in strawberry and orange products. J. Food Sci. 62, 85-88. 

The rate of reaction may depend upon reactant concentration, product concentration, and temperature. Cases in which the product concentration affects the rate of reaction are rare and are not covered on the AP exam. Therefore, we will not address those reactions. We will discuss temperature effects on the reaction later in this chapter. For the time being, let s just consider those cases in which the reactant concentration may affect the speed of reaction. For the general reaction aA + bB+...->c C + dD +. . . where the lower-case letters are the coefficients in the balanced chemical equation the upper-case letters stand for the reactant and product chemical species and initial rates are used, the rate equation (rate law) is written ... 

The reaction of dicyclohexylborane and trifluoromethanesulfonic acid is highly exothermic. On one occasion, the checkers cooled the reaction in an ice bath during the addition period, with no effect on product yield. The submitter reports that he once experienced a sudden vigorous reaction under cooling conditions, probably due to accumulation of unreacted triflic acid. It thus appears safer to add the acid at room temperature, slowly, so that it reacts immediately. 

A change in any one of the three included variables which improves the quality of the product will increase the numerical value of the factor hence, the larger the factor, the better the alkylate quality. In ordinary commercial operation F will vary from about 10 to 40. Acid content of the reaction mixture and reaction time, while not directly a part of the factor, are so interrelated that if the acid content is maintained above 40%, the olefin space velocity term correlates the effects of these variables satisfactorily. While reaction temperature has an important effect on product quality, it has not been included in this factor since this variable is ordinarily held constant at an optimum value for any well-... 

The Chevron/Gulf process also uses triethylaluminum but in a catalytic reaction at higher temperature. Reaction conditions exert a strong effect on product distribution. Under the proper conditions (200-250°C, 140-270 atm) the rates of insertion and chain transfer (displacement) are comparable, ensuring frequent p-hydrogen elimination. A broader product distribution compared with that of the two-step ethyl process is obtained. 

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