Temperature, effect on hydrogenation

Pressure and Temperature Effect on Hydrogenous Mixture Self-Ignition... 

First Carbonation. The process stream OH is raised to 3.0 with carbon dioxide. Juice is recycled either internally or in a separate vessel to provide seed for calcium carbonate growth. Retention time is 15—20 min at 80—85°C. OH of the juice purification process streams is more descriptive than pH for two reasons first, all of the important solution chemistry depends on reactions of the hydroxyl ion rather than of the hydrogen ion and second, the nature of the C0 2 U20-Ca " equiUbria results in a OH which is independent of the temperature of the solution. AH of the temperature effects on the dissociation constant of water are reflected by the pH. 

The composition of the products of reactions involving intermediates formed by metaHation depends on whether the measured composition results from kinetic control or from thermodynamic control. Thus the addition of diborane to 2-butene initially yields tri-j iAbutylboraneTri-j -butylborane. If heated and allowed to react further, this product isomerizes about 93% to the tributylborane, the product initially obtained from 1-butene (15). Similar effects are observed during hydroformylation reactions however, interpretation is more compHcated because the relative rates of isomerization and of carbonylation of the reaction intermediate depend on temperature and on hydrogen and carbon monoxide pressures (16). 

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. 

FLF)- (L = H or D) anion in low temperature solutions of (C4H9)4N+ (FL)nF . The authors were able to determine zero-, one-, and two-bond, H/D isotope effects on hydrogen and fluorine NMR chemical shifts for the series n = 1 to n = 3, and to relate the observed spectra to H/D isotope effects on the hydrogen bond geometries. Isotope effects on spin-spin L-F and F-F coupling 13C constants were reported. 

Horita J, Cole DR, Polyakov VB, Driesner T (2002) Experimental and theoretical study of pressure effects on hydrogen isotope fractionation in the system brucite-water at elevated temperatures. Geochim Cosmochim Acta 66 3769-3788... 

Bajusz, I.G. and Goodwin, Jr., J.G., Hydrogen and Temperature Effects on the Coverages and Activities of Surface Intermediates during Methanation on Ru/Si02, J. Catalysis 169, 157-165 (1997). 

Fukai, T. and K. Matsumoto, Surface modification effects on hydrogen permeation in high-temperature, high-pressure, hydrogen-hydrogen sulfide environments. Corrosion (Houston), 50, 522 (1994). 

The temperature effect on the hydrogenation kinetics was examined at 60 C, 70 °C and 77 °C. The yield of citronellal and its ethylacetal attained its maximum most rapidly at the lowest temperature (60 °C). This is probably because the activation energy of the hydrogenation of the conjugated double bond is lower than that of the carbonyl group. 

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