Reactions conversion

The influence of the partial pressure of water vapor during calcium sulfate dihydrate decomposition was explored by Lehmann and RiekeJ This work provided confirmation of the direct conversion of the dihydrate 

DTA curves forthe liberation of non-stoichiometric water of 13-hemihydrate are presented in Fig. 14. The curve (/ .a.) refers to the sample of particle size 20 pm. The influence of the temperature forthe dihydrate dehydration and the time for rehydration on the slope of the peak doublet are apparent. The doublet reflects mass loss from both the non-stoichiometric lattice water and the sorbed water associated with the high specific surface area. This suggests that the micro-porosity of the /3-hemihydrate pseudo-morph is responsible for the appearance of the peak doublet. Examination of Fig. 14 shows a small effect ofthe temperature of dehydration on the shape of the peak doublet. The first peak can be attributed to the liberation of micropore water, which does not appear to depend on the dehydration temperature. The absorption of lattice water is a slow process as reflected in the much longer time of rehydration required forthe growth of the second peak. It is also apparent that the slow water absorption of the lattice depends on the grain size [compare curves (c) and (/) in Fig. 14]. 

The influence of the experimental parameters on the shape of the peak doublet in the DTA curves of the liberation of the non-stoichiometric water of j8-hemihydrate is indicated in Fig. 15. The influence of the partial pressure of the water vapor or the speed of liberation of the non-stoichio-metric water can be discerned from the curves. Curve (1) was obtained without a crucible lid. The water can be driven off much faster and a low partial pressure of water vapor can be obtained. A higher partial pressure results in a displacement of the peak to higher temperature and produces improved resolution of the second peak. The areas of curves (2) and (3) are approximately the same if the decreased heating rate and reduced chart speed are taken into account. The sensitivity of the measurements was held constant. Curve (3) illustrates that a lower heating rate results in a lower partial pressure of water vapor, lower peak temperatures, and a decrease in the intensity of the second peak. 

It should be noted that other woikers, e.g., Holdridge and Walker, indicate that for prolonged storage, e.g., 18 months, the first peak is larger than the second one.t J At shorter times of storage, the second peak was of larger intensity. Comparison of the data is rendered difficult unless the experiments are carried out under identical conditions. 

---

Carbon monoxide and excess steam are normally passed over a cobalt catalyst at about 250-300 C resulting in greater than 99% conversion of CO to COj. This conversion reaction is widely used in oil or solid fuel gasification processes for the production of town gas or substitute natural gas. ... 

The presence of an electron donor causes the equiHbrium to shift to the left. The acidity represented by this mechanism is important in hydrocarbon conversion reactions. Acidity may also be introduced in certain high siHca zeoHtes, eg, mordenite, by hydrogen-ion exchange, or by hydrolysis of a zeoHte containing multivalent cations during dehydration, eg,... 

AMMONIA Raw material Process description Feedstock conversion reaction V012... 

The conversion reaction from coal to oil has been modeled as a series of steps ... 

The frequency job on the middle structure produces one imaginary frequency, indicating that this conformation is a transition structure and not a minimum. But what two minima does it connect Is it the transition structure for the cis-to-trans conversion reaction (i.e. rotation about the C=C bond) ... 

The reaction capability of PS is weak, but the reaction capability can be improved by anchoring the functional group to the aliphatic chain or aromatic ring of PS using chemical or conversion reactions. Aliphatic chain reactions are halogenation reactions, oxidation reactions, or unsaturated acids to bonded aliphatic chain of PS (in the presence of a radical catalysis). 

From these simple intermediates, many important chemicals and polymers are derived through different conversion reactions. The ohjec-tive of this hook is not merely to present the reactions involved in such conversions, hut also to relate them to the different process variables and to the type of catalysts used to get a desired product. When plausi-hle, discussions pertinent to mechanisms of important reactions are included. The hook, however, is an attempt to offer a simplified treatise for diversified subjects dealing with chemistry, process technology, polymers, and catalysis. 

The reaction of 3-substituted 3-haloallenes with various cuprates, the converse reaction of propargyl derivatives, proceeds in an SN2 manner to form alkynes 69b. Very high anti stereoselectivity is achieved693. 

Table III lists the kinetic equations for the reactions studied by Scholten and Konvalinka when the hydride was the catalyst involved. Uncracked samples of the hydride exhibit far greater activation energy than does the a-phase, i.e. 12.5 kcal/mole, in good accord with 11 kcal/mole obtained by Couper and Eley for a wire preexposed to the atomic hydrogen. The exponent of the power at p amounts to 0.64 no matter which one of the reactions was studied and under what conditions of p and T the kinetic experiments were carried out. According to Scholten and Konvalinka this is a unique quantitative factor common to the reactions studied on palladium hydride as catalyst. It constitutes a point of departure for the authors proposal for the mechanism of the para-hydrogen conversion reaction catalyzed by the hydride phase.

In general, for polymerization reactions, the heat generation rate is not a single-valued function of temperature, g(t), but also a function of monomer and catalyst concentrations, f(c). This is particularly important in high conversion reactions where a certain amount of peaking can be tolerated. 

In a reaction in which the number of product molecules is equal to the number of reactant molecules, (e.g., A + B —> C + D), entropy effects are usually small, but if the number of molecules is increased (e.g., A —> B + C), there is a large gain in entropy because more arrangements in space are possible when more molecules are present. Reactions in which a molecule is cleaved into two or more parts are therefore thermodynamically favored by the entropy factor. Conversely, reactions in which the number of product molecules is less than the number of reactant molecules show entropy decreases, and in such cases there must be a sizable decrease in enthalpy to overcome the unfavorable entropy change. 

Buser H-R, MD Muller (1997) Conversion reactions of various phenoxyaUcanoic acid herbicides in soil 2 elucidation of the enantiomerization process of chiral phenoxy acids from incubation in a DjO/soil system. Environ Sci Technol 31 1960-1967. 

Figure3.56 Resultsofaparametricstudyontheimpactofchannel depth on benzene conversion. Reaction probability=l 0 T=200°C /3 =l.latm atm [10],...

In the copper production stage, copper sulfide is oxidized to molten copper metal, known as blister copper and so named because when liquid copper cools, the evolution of the residual sulfur and oxygen from the metal as sulfur dioxide gas causes blisters to form on the surface of the metal. The conversion reaction may be shown as ... 

Basch, H., Mogi, K., Musaev, D. G., Morokuma, K., 1999, Mechanism of the Methane —> Methanol Conversion Reaction Catalyzed by Methane Monooxygenase A Density Functional Study , J. Am. Chem. Soc., 121, 7249. 

Finally, some details of the dynamics of NO conversion reactions on surfaces have been recently probed by using angle-resolved TPD. For instance, in a study of the decomposition of N20 on Rh(110), Matsushima and co-workers have identified four N2 peaks between 60 and 150 K originating from direct N20-dissociation, and a fifth feature at 160 K attributed to the desorption of N2 molecules adsorbed on the surface after previous decomposition (Figure 3.2) [20]. The appearance of each of these peaks... 

Durham polyacetylene occurs in a highly disordered state on conversion from the precursor polymer [90], but using stretch orientation techniques during the conversion reaction, a high degree of order with long conjugated sequences can be achieved [91-93],... 

---