Reaction conditions temperature effects

In the aqueous biphasic hydroformylation reaction, the site of the reaction has been much discussed (and contested) and is dependent on reaction conditions (temperature, partial pressure of gas, stirring, use of additives) and reaction partners (type of alkene) [35, 36]. It has been suggested that the positive effects of cosolvents indicate that the bulk of the aqueous liquid phase is the reaction site. By contrast, the addition of surfactants or other surface- or micelle-active compounds accelerates the reaction, which apparently indicates that the reaction occurs at the interfacial layer. 

This iron-ate complex 19 is also able to catalyze the reduction of 4-nitroanisole to 4-methoxyaniline or Ullmann-type biaryl couplings of bis(2-bromophenyl) methylamines 31 at room temperature. In contrast, the corresponding bis(2-chlor-ophenyl)methylamines proved to be unreactive under these conditions. A shift to the dianion-type electron transfer(ET)-reagent [Me4Fe]Li2 afforded the biaryl as well with the dichloro substrates at room temperature, while the dibromo substrates proved to be reactive even at —78°C under these reaction conditions. This effect is attributed to the more negative oxidation potential of dianion-type [Me4Fe]Li2. 

Electronic effects of substituent, as well as reaction conditions (temperature, solvent) influence the ratio of isomers. The alkylation of l-alkyl-5-aryl tetrazoles with dimethyl sulfate at room temperature proceeds at the... 

Limitation of Effects - safer technical alternatives - safer reaction conditions temperature pressure equipment safety safe process structure pressure temperature chemical interaction... 

The rate expressions Rj — Rj(T,ck,6m x) typically contain functional dependencies on reaction conditions (temperature, gas-phase and surface concentrations of reactants and products) as well as on adaptive parameters x (i.e., selected pre-exponential factors k0j, activation energies Ej, inhibition constants K, effective storage capacities i//ec and adsorption capacities T03 1 and Q). Such rate parameters are estimated by multiresponse non-linear regression according to the integral method of kinetic analysis based on classical least-squares principles (Froment and Bischoff, 1979). The objective function to be minimized in the weighted least squares method is... 

Direct Conversion of Ammonium Zeolite Y. The procedures of McDaniel and Maher 20), Hansford 27), and Kerr 26) appear to have in common reaction conditions which effect hydrolysis and removal of a portion of the tetracoordinate aluminum ions from the framework of the hydrogen form during decomposition of the ammonium form at temperatures of 400° C and above. 

The transient nature of the cavitation event precludes conventional measurement of the conditions generated during bubble collapse. Chemical reactions themselves, however, can be used to probe reaction conditions. The effective temperature realized by the collapse of clouds of cavitating bubbles can be determined by the use of competing unimolecular reactions whose rate dependencies on temperature have already been measured. The sonochemical ligand substitutions of volatile metal carbonyls were used as... 

The effect of reaction conditions (temperature, pressure, H2 flow, C02 and/or propane flow, LHSV) and catalyst design on reaction rates and selectivites were determined. Comparative studies were performed either continuously with precious-metal fixed-bed catalysts in a trickle-bed reactor, or batchwise in stirred-tank reactors with supported nickel or precious metal on activated carbon catalysts. Reaction products were analyzed by capillary gas chromatography with regard to product composition, by titration to determine iodine and acid value, and by elemental analysis. 

This study evaluated changes in the quantity of volatiles formed from rhamnose and proline as functions of three reaction conditions temperature, pH and relative concentration. The objective was to identify and quantify the presence of interactions between dependant variable reaction conditions. That is, for example, the effect of temperature on trends brought about by pH. Such interactions cannot be estimated when variables are studied one-variable-at-a-time. A further benefit would be attained if the models could provide insight into the chemical processes involved. 

Table 2 Effect of the dilution of feed ethanol with water (Reaction conditions temperature = 363 K, contact time = 1.5 h and ethanol/isobutene ratio = 1.2).

As already indicated, the overall concentration and distribution of macrocyclics may be to some extent altered by changing the reaction conditions (temperature, solvent, counterion). These effects, however, are not significant and difficult to predict. 

Cook and Moore35 studied gas absorption theoretically using a finite-rate first-order chemical reaction with a large heat effect. They assumed linear boundary conditions (i.e., interfacial temperature was assumed to be a linear function of time and the interfacial concentration was assumed to be a linear function of interfacial temperature) and a linear relationship between the kinetic constant and the temperature. They formulated the differential difference equations and solved them successively. The calculations were used to analyze absorption of C02 in NaOH solutions. They concluded that, for some reaction conditions, compensating effects of temperature on rate constant and solubility would make the absorption rate independent of heat effects. 

This work involved the study by TPSR in H2 of carbon and carbide species formed in iron catalysts during FT synthesis for up to 18 hours under steady-state conditions or up to 6 hours under severe, deactivating reaction conditions. The effects of reaction temperature and potassium oxide promotion on the distribution of carbon types were also determined. 

To elucidate the effects of reaction, reoxidation and industrial reaction conditions (temperature, presence of steam and composition of reactant mixture) on the structural properties,... 

Under steady state reaction conditions, the effects of CO2 on the methane coupling reaction over Li/MgO catalyst were quantitatively determined. Poisoning effects of CO2 on carbon oxide formation rate, C2 formation rate, and methane conversion were observed for all methane to oxygen ratios and all temperatures. However, C2 selectivity is relatively unaffected by CO2 partial pressure. The mechanism described here accounts for important elementary steps, especially the effects of carbon dioxide. Under the low conversion conditions used in this study, further oxidation of C2 products to CO and CO2 is assumed negligible. These reactions will become more important at high conversions. Rate expressions derived from the mechanism match well the experimental conversions and selectivities. 

Fig. 2. Effect of alkali promotion on the average STY over Fe UFP catalysts. Reaction conditions temperature, 220°C pressure, 30 atm H2/CO, 1 mol/mol ...

Figure 1. Effect of Sr/La ratio on the ethane and O2 conversion, product selectivity and CO/CO2 ratio in the oxidative dehydrogenation of ethane to ethylene over Sr-La2O3/SA-5205 catalyst [ Reaction condition Temperature = 700°C, C2H5/O2 = 6.0, steam/C2H6 = 1.0, space velocity = 100,104 cm. g. h ].

Boundary layer diffusion resistance can be reduced by increasing the linear velocity of the flow passing over the surface. In practice this means increasing the turbulence of the fluid in die presence of the solid particle. To see the effect of turbulence (or fluid linear velocity) at a given space time and the other reaction conditions (temperature, pressure and composition), one has to change the relative velocity between the solid and the fluid. 

The present work deals with sintering of Ni/AbOa catalysts under reducing and steamreforming reaction conditions. The effects of preparation method (impregnation and coprecipitation), lanthanum oxide promoter, oxide phases developed after calcination, sintering temperature and atmosphere were studied in terms of the time evolution of metal dispersion, size distribution properties and kinetic parameters obtained from a GPLE model. 

Measurements of are usually made at ambient conditions using simple gases such as N2, He, H2, and CO2. To predict for the same catalyst under reaction conditions, the effects of changes in temperature, pressure, and gas composition must be accounted for. One approach is to predict Dpore for the test gas (say. He) from Eqs. (4.5), (4.7), and (4.9) and to calculate r from Eq. (4.10) using measured values of and r. Then is predicted for the reactants at various reaction temperatures and pressures, and the same values of e and r are used to get from Eq. (4.10). The relative importance of Knudsen diffusion and bulk diffusion may change with reaction conditions, but and r should be constant. 

Amine-copper complexes are able to produce DMC even at room temperature under carbon monoxide at atmospheric pressure. Simple copper salts, like CuCl, require more drastic reaction conditions to effect the formation of DMC (15), e.g. temperature starting from about 70 °C. On the other hand they do not suffer the problems associated with the use of copper complexes, so that, a catalytic cycle with simultaneous reoxidation by O2 is easily established using CuCl. 

---