Propylene kinetic orders

Simple nth order kinetics are not adequate for representing propylene pyrolysis over any but a relatively short temperature and/or conversion range, A transition does occur from an overall propylene pyrolysis order of 1.5 to 1.0 as the temperature of reaction increases from 700 to 850C. 

Hydrolysis to Glycols. Ethylene chlorohydrin and propylene chlorohydrin may be hydrolyzed ia the presence of such bases as alkaU metal bicarbonates sodium hydroxide, and sodium carbonate (31—33). In water at 97°C, l-chloro-2-propanol forms acid, acetone, and propylene glycol [57-55-6] simultaneously the kinetics of production are first order ia each case, and the specific rate constants are nearly equal. The relative rates of solvolysis of... 

Debande and Huybrechts lnt. J. Chem. Kinetics, 6 (545), 1974] have studied the gas phase Diels-Alder additions of propylene (P) to cyclohexa-1, 3-diene (Chd) to give the exo-and endo-isomers of 5-methylbicyclo (2,2,2) oct-2-ene (MBO). The initial reaction rates were both found to be of the mixed second-order type with... 

Baranski and Lu [209] have carried out, applying microelectrodes, voltammetric studies on ammonium amalgam in propylene carbonate solutions at room temperatures. The sweep rates up to 80 V s were appropriate for the analysis of the formation kinetics of this compound. Experimental and numerical simulation results have shown that ammonium amalgam was formed via fast charge-transfer process and its first-order decomposition was characterized by the rate constant of about 0.6 s . Diffusion coefficient of NH4 radical in mercury was estimated to be about 1.8 X 10 cm s k The formal potential of NH4+ (aq)/NH4(Hg) couple was determined as—1.723 V (SHE). 

Metathesis activity. A quantitative comparison of metathesis activities was made in the gas phase homometathesis of propylene. The reaction kinetics are readily monitored since all olefins (propylene, ethylene, cis- and fra/3s-2-butylenes) are present in a single phase. Metathesis of 30 Torr propylene was monitored in a batch reactor thermostatted at 0 °C, in the presence of 10 mg catalyst. The disappearance of propylene over perrhenate/silica-alumina (0.83 wt% Re) activated with SnMe4 is shown in Figure 2a. The propylene-time profile is pseudo-first-order, with kob (1.11 + 0.04) X 10" slightly lower rate constant, (0.67 constants are linearly dependent on Re loading. Figure 3. The slope yields the second-order rate constant k = (13.2 + 0.2) s (g Re) at 0°C. 

Figure 2 Kinetics of gas-phase propylene homometathesis at 0°C, catalyzed by (a) perrhenate/silica-alumina activated by SnMe4 (10 mg, 0.83 wt % Re) and (b) MeReOs on HMDS-capped silica-alumina (10 mg, 1.4 wt % Re). Solid lines are curve-fits to the first-order integrated rate equation. Solid squares first addition solid circles second addition open circles third addition of propylene (30 Torr) to the catalyst.

Oxidation of propylene to form acrolein depends on the first order of propylene and is independent of oxygen on multicomponent bismuth molybdate catalysts under the usual reaction conditions. The observed kinetics is the same with simple bismuth molybdates and suggests that the oxidation of propylene proceeds via the similar reaction scheme reported for simple molybdates, the slow step being the abstraction of allylic hydrogen (9-15, 19, 20). However, the reaction sometimes depends on the partial pressure of oxygen under lower temperature and lower oxygen pressure (41, 42). 

Kinetics of reaction must be considered when attempting to postulate mechanisms, but kinetic equations alone are unreliable in fixing mechanism. For example, in the oxidation of propylene to acrolein, cuprous oxide and bismuth molybdate have very different kinetics, yet the studies of Voge, Wagner, and Stevenson (18), and especially of Adams and Jennings (1, 2) show that in both cases the mechanism is removal of an H atom from the CH3 group to form an allylic intermediate, from which a second H atom is removed before the O atom is added. The orders of the reactions and the apparent optimum catalysts (16) are as follows ... 

Recently, a study on the effect of cosolvents on a degradation of zileuton has been reported [104], Under aqueous conditions, zileuton follows Lrst order kinetics. In this study, authors have used a ternary solvent system consisting of water, ethanol, and propylene glycol to examine both the solubility and stability of zileuton. 

A special feature of this reaction is that the first order kinetics is not related to the propylene concentration fed by convection and gas-liquid mass transfer (a saturated propylene concentration assumed in electrolyte), but related to the OH ion concentration, because the OH ion pass through the membrane from the cathode side ... 

A simple dynamic model is discussed as a first attempt to explain the experimentally observed oscillations in the rate of propylene oxide oxidation on porous silver films in a CSTR. The model assumes that the periodic phenomena originate from formation and fast combustion of surface polymeric structures of propylene oxide. The numerical simulations are generally in qualitative agreement with the experimental results. However, this is a zeroth order model and further experimental and theoretical work is required to improve the understanding of this complex system. The in situ use of IR Spectroscopy could elucidate some of the underlying chemistry on the catalyst surface and provide useful information about surface coverages. This information could then be used to either extract some of the surface kinetic parameters of... 

Figure 5.20 shows concentration-time profiles for the decomposition of hydrocortisone butyrate at 60°C in a buffered aqueous propylene glycol (50 w/w%, pH 7.6). Consecutive, irreversible, first-order kinetic models [i.e., Equation (5.119a), Equation (5.119b), and Equation (5.119c)] fit reasonably well with the experimental... 

The kinetic curve would then be the result of two curves, one representing the 1st order decay attributed to isospecific polymerization centers, and the other representing a stationary state attributed to the less stereospecific centers. This expression can be credited with taking into consideration a stationary state and, furthermore, it is in agreement with the inverse correlation between productivity and isotacticity of the polymer found experimentally. In fact, assuming Is to be the isotacticity of propylene produced by the isospecific centers, unstable with time, and IA the isotacticity of polypropylene produced by the less specific centers, stable with time, the total isotactic index IIt is given by the expression ... 

Actually, studies on the propylene polymerization at atmospheric pressure carried out in our laboratories 101 > have demonstrated that R0 and the deactivation rate depend, in a complex manner, on both the organoaluminum and external donor concentrations (see Sect. 6.1.2 and 6.1.3). The kinetic curves obtained cannot be reduced to a single model for the deactivation of active centers according to a simple 1 st and 2nd order law, but rather they seem to follow a more complicated behavior. This is not surprising if one considers that the decay of polymerization rate is probably the effect of an evolution, in time, of a plurality of different catalytic species having different stability, reactivity and stereospecificity (see Sect. 6.3). 

The measured reaction orders support the proposed mechanism. Path A is certainly first order in reactant. Paths B and C may be 1/2, first, or 3/2 order, depending on the termination reaction (15). Most likely, termination involves combination or disproportionation of small chain carrying radicals (CH3, C2H5 ). With first-order initiation, this would result in 3/2-order kinetics. The overall reaction order would then be somewhere between first (Mechanism A) and 3/2 (Mechanisms B and C). The measured order of 1.33 for dodecene agrees with this prediction. The fact that propylene and nonene are formed with reaction orders of 1.10 and 1.16 with respect to dodecene (Table III) supports the hypothesis that they are formed largely by a first-order decomposition. 

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