Effect of temperature on product distribution

Fig. 5. The effect of temperature on product distribution in VPO of butane with air.

To understand the effect of temperature on product distribution, let s briefly review what we said in Section 5.7 about rates and equilibria. Imagine a reaction that can give either or both of two products, B and C. 

Effect of Temperature. Figure 5 illustrates the effect of temperature on product distribution. An increase in temperature decreases yields of gasoline and increases gas yields. In addition, the yield of butylenes in the C4 cut increases with increased temperature and the octane number of the gasoline produced is higher,... 

COKE YIELD, WEIGHT % OF CHARGE Figure 5, Effect of Temperature on Product Distribution... 

Figure 4. Effect of temperature on product distribution (3000 psig, 1.0 gm/hr/gm nominal)...

As with cyclopentadiene, the relative yields of products (19)—(21) were relatively insensitive to the sensitizer triplet energy(37) although an effect of temperature on dimer distribution has been noted.0,28 The direct photolysis of cyclohexadiene with wavelengths greater than 330 nm yielded products (19)—(21), although the product distribution in this case was more nearly statistical [(19) (20) (21) = 44% 2470 33%] 28 . 

Since product distributions depend on the relative rates of competing reactions, effects of temperature on products depend on differences in activation energies, AE. For each pair of competing reactions of the tert-Bu02 radicals, the following AE values (in kilocalories per mole) and qualitative effects of increasing temperature are estimated. Some of these values were considered under Liquid-Phase Oxidations. ... 

FIGURE 10.15 Effect of temperature on the distribution of products for butane oxidation at atmospheric pressure and constant reactant ratio [248]. 

The effect of temperature on the distribution of olefin products over SAPO-34 is illustrated in Table 8. As the temperature increases, the molar selectivity to ethylene increases, selectivities to propylene and butene decrease, and the molar selectivity to CH increases [151,193]. According to the equilibrium, propylene selectivity should also increase when temperature is raised (Fig. 34). However, propylene and butenes are more reactive than ethylene, so they can further undergoing transformation. Furthermore, diffusion of ethylene to outside cages of SAPO-34 is favored in comparison with the diffusion of propylene [194], This highlights the fact that the thermodynamic equilibrium of light olefins may occur within SAPO-34 prior to diffusion out of the crystalline structure. But diffusion limitations and differences in reactivity between the light olefins influence the final composition outside the zeolyte crystal. 

The effects of temperature on the conversions of CO2 and CH4 and the product distribution over Ni-YSZ-Ce02 catalyst are represented in Fig. 2. The concentrations of H2 and CO were slowly increased with increasing reaction temperature but those of CO2 and CH4 were decreased. Moreover, the concentrations of H2 and CO over Ni-YSZ-Ce02 catalyst were slightly higher than those over Ni-YSZ-MgO [7],... 

The experiments revealed that the initial rate increases as a function of temperature. The product distribution was not strongly affected by the temperature. The product ratio of pentanal-to-2-methyl butanal is approximately 4. The total pressure did not have any significant effect on the product distribution. 

Table 10.8. Effect of Temperature on the Product Distribution from the a-Acetonaphthone-Sensitized Photoaddition of Cyclopentadiene to cis- and trans-Dichloroethylene<60>...

The effect of temperature on the catalytic performance of Mg/Fe/O is reported in Figure 3. The behavior was quite different from that of the Mg/Al/O catalyst. The conversion of m-cresol with Mg/Fe/O was always lower than that with Mg/Al/O. The selectivity to 3-MA was almost negligible in the whole range of temperature. The selectivity to polyalkylates and to 3,4-DMP was also much lower than that observed with Mg/Al/O. Therefore, the catalyst was very selective to the products of ortho-C-methylation, 2,3-DMP and in particular 2,5-DMP. This behavior has to be attributed to specific surface features of Mg/Fe/O catalyst, that favor the ortho-C-methylation with respect to O-methylation. A different behavior of Mg/Al/O and Mg/Fe/O catalysts, having Mg/Me atomic ratio equal to 4, has also been recently reported by other authors for the reaction of phenol and o-cresol methylation [5], The effect was attributed to the different basic strength of catalysts. This explanation does not hold in our case, since a similar distribution of basic strength was obtained for Mg/Al/O and Mg/Fe/O catalysts [4],... 

The aldol condensation reaction of acetone was performed over CsOH/Si02 at a range of reaction temperatures between 373 and 673 K (a typical product distribution is shown in Figure 2). Table 1 displays the conversion of acetone along with the selectivities for the products produced once steady state conditions were achieved. Figure 3 presents the effect of temperature on the yield of the products. The activation energy for acetone conversion was calculated to be 24 kJ. mol 1. 

The effects of composition of heavy oils derived from petroleum and biomass, on their response to cracking over catalysts of various composition were investigated. The contribution to the conversion from different types of cracking was estimated and the effect of temperature on the product distribution was studied. 

Figure 3. Effect of temperature on the product distribution with ZnCl2 catalyst...

Results of a large number of experiments carried out to study the effect of temperature and the nature of the coinitiator in various solvents on conversion and product distributions are summarized in Table 3. The effect of temperature on overall conversions obtained in methyl chloride solvent is plotted separately in Fig. 2. These results will be (bussed in terms of the overall coinitiator reactivities and coinitiator efficiencies. Further, the effect of temperature, solvent and the nature of the alkyl-aluminum coinitiator-alkylhalide initiator system on the fundamental reactions of polymerization will be examined... 

FIGURE 5.7. Effect of reaction temperature on product distribution... 

The model is formulated on the premise that the decomposing hydrate particle is surrounded by a cloud of the product gas hence the driving force for the decomposition process is expressed in terms of the fugacity difference given in Eq. (1). The process of decomposition possibly involves (1) destruction of the clathrate host (water) lattice at the surface of the particle, and (2) and desorption of the guest (hydrate former) molecules from the surface. The particle size distribution was incorporated in the calculations for the determination of the intrinsic rate constants.The following Arrhenius type equation is used to represent the effect of temperature on the intrinsic rate constant ... 

Table XIX presents a selection of the results obtained in a study of the reaction of ethylene with deuterium over rhodium-alumina (31), together with some calculated distributions obtained by the method previously employed. The proportion of deuterated ethylenes in the initial products rises from 30% at —18° to 75% at 110°. In contrast to the behavior of palladium, ethane-dj is the major ethane throughout and hydrogen exchange is significant at all but the lowest temperature studied. The parameters used in the calculations attribute the greatest effect of temperature to the variation of the chance of ethylene desorption, which rises from 25% at —18° to 62% at 110°. The effect of temperature on the chance of alkyl reversal is relatively small. Another resjject in which the reaction over rhodium differs from that over palladium is that the chance of acquisition of deuterium in the hydrogenation steps is higher, and indeed it appears that, as with iridium, molecular deuterium may be substantially responsible for the conversion of ethyl radicals to ethane. E — E, is 3 kcal mole and E, — E, is 4.5 kcal mole. The reaction is first-order in hydrogen and zero in ethylene.

Fig. 5 shows the effect of various supports of nickel-loaded catalysts and reaction temperature on the methane conversion, in the partial oxidation of methane. At methane to oxygen ratio of 5 1, the maximum conversion of methane is 40 %, when reaction (5) proceeded, and 10% when complete oxidation proceeded. Only the oxidized diamond-supported Ni catalyst exceeded 10% conversion above 550 C, indicating that the synthesis gas formation proceeded. Ni-loaded LazOz catalyst afforded considerable methane conversion above 450 °C, but the product is mainly COz. Other supports to nickel showed no or only slight catalytic activity in the partial oxidation of methane. These results clearly show that oxidized diamond has excellent properties in the partial oxidation of methane at a low temperature, giving synthesis gas. Fig. 6 shows the effect of temperature on the product distribution, in the partial oxidation of methane. Above 550 °C, Hz and CO were produced, and below 500 °C, only complete oxidation occurred. The Hz to CO ratio should be 2 according to the stoichiometry. However, 3.2 and 2.8 were obtained at 550 and 600 °C, respectively. 

It is possible to use the effect of temperature on the solution phase product distribution (Table 2) to deduce the lifetime of singlet phenyl nitrene in solution. 

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