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** First-order reactions reaction **

** Pseudo first-order reaction, rate coefficient for **

FIRST-ORDER RATE COEFFICIENTS FOR REACTION OF CYCLOHEXENE WITH BENZENE [Pg.155]

FIRST-ORDER RATE COEFFICIENTS FOR REACTION OF [4,6-3H2]-l, 2,3-(MeO)3C6H WITH [Pg.208]

Figure 11. First-order reaction rate coefficients for the very-low-pressure pyrolysis of t-C4H90N0 for collision numbers of 11200, fA) 2,470 (O) 387 ( ). From Mendenhall et al. (1973) with permission of John Wiley and Sons, Inc. |

If methane is considered for reaction (3.13), a first order reaction rate is usually assumed, i.e. the coefficient n of expression (3.22) is equal to 1. According to Achenbach [22], the activation energy of methane steam reforming is 82 kJ mol-1 and the pre-exponential factor is 4274 mol m-2 bar-1 s-1. More recent experimental studies report an activation energy of 112 15 kJ mol-1 [23], [Pg.57]

Yamase and Goto406 determined first- and second-order rate coefficients for the aluminium chloride-catalysed reaction of halide derivatives of benzoic acid (lO5 = F, 1.73 Cl, 4.49 Br, 4.35 I, 0.81) and phenylacetic acid (105fc2 = F, 12 Cl, 21 Br, 9 I, 6) with benzene. The maxima in the rates for the acid chloride are best accommodated by the assumption that a highly (but not completely) polarised complex takes part in the transition state. Polarisation of such a complex would be aided by electron supply, and consistently, the acetyl halides are about a hundred times as reactive as the benzoyl compounds (see p. 180, also Tables 105 and 108). [Pg.173]

Eaborn and Taylor147 measured first-order rate coefficients for sulphonation of some aromatics in mixtures of trifluoroacctic acid-aqueous sulphuric acid, as sulphonation proved to be a troublesome side reaction accompanying hydrogen exchange in these media. They introduced a technique which has been found useful by later workers and makes use of the high solubility of sulphonic acids in [Pg.61]

First-order and pseudo-first-order reactions are represented by the upper curve in Fig. 14-14. We note that for first-order reactions when the Hatta number is larger than about 3, the rate coefficient k can be computed by the formula [Pg.1367]

Fig. 5.5 Concentration profile for a reaction fast enough to become complete within the diffusion film first-order reaction rate constant k =1 s-1, and reactant diffusion coefficient in the receiving phase D = 5x10-6 cm2 s 1. |

Base catalysis was shown not to be significant on two grounds. Firstly, the second-order rate coefficients for the two sets of acetate buffer data are the same within experimental error, and secondly, the addition of base of concentrations 0.05 and 0.2 M to the reaction with water caused a negligible change in the rate coefficient. [Pg.210]

A 95% conversion of reactant A is required in a tubular reactor for which we anticipate DluL will be 0.5. The reaction is first order with rate coefficient, k, equal to 0.16 min and there is no change in volume on reaction 107 dm min of feed must be treated. What size reactor is required [Pg.266]

Note that if sticking is controled by site-exclusion only, i.e., if S 6,T) = 5 o(P)(l — 0), this rate is that of a first-order reaction at low coverage. This simple picture breaks down when either the sticking coefficient depends dilferently on the coverage, as it does for instance for precursor-mediated adsorption, or when lateral interactions become important. It then does not make much physical sense to talk about the order of the desorption process. [Pg.445]

A kinetic analyses of the data was performed by noting the pseudo-first order loss of substrate together with selectivity. This enabled a pseudo-first order kinetic description of the two pathways to be obtained. Table 1 lists the lifetimes of 2-butanone and 2-butanol production for the various experiments. Here the lifetimes refers to the inverse of the pseudo-first order reaction rate coefficients. [Pg.216]

Figure 29, the Arrhenius plot of these data, yields an adequate exponential fit with a correlation coefficient of 0.973. The fit is neither as good nor as rehable as that of the first-order reaction rate because fewer points were obtainable for either the 200°C reactions - where initiation occurs veiy rapidly, making measurement of the active complex formation difficult - or for the 130°C reactions - where few data points had been collected because of the sluggishness of the reaction at this temperature. [Pg.148]

The CEB method can be extended to chemically reactive species by introducing decay factors into the mass balances for the chemical species. The decay factors can be evaluated from data for the composition of emissions and of the ambient aerosol. They can be related to first order reaction rate coefficients measured in the laboratory by means of an appropriate atmospheric model. [Pg.18]

Diffusion effects can be expected in reactions that are very rapid. A great deal of effort has been made to shorten the diffusion path, which increases the efficiency of the catalysts. Pellets are made with all the active ingredients concentrated on a thin peripheral shell and monoliths are made with very thin washcoats containing the noble metals. In order to convert 90% of the CO from the inlet stream at a residence time of no more than 0.01 sec, one needs a first-order kinetic rate constant of about 230 sec-1. When the catalytic activity is distributed uniformly through a porous pellet of 0.15 cm radius with a diffusion coefficient of 0.01 cm2/sec, one obtains a Thiele modulus y> = 22.7. This would yield an effectiveness factor of 0.132 for a spherical geometry, and an apparent kinetic rate constant of 30.3 sec-1 (106). [Pg.100]

The concentration of monomers in the aqueous phase is usually very low. This means that there is a greater chance that the initiator-derived radicals (I ) will undergo side reactions. Processes such as radical-radical reaction involving the initiator-derived and oligomeric species, primary radical termination, and transfer to initiator can be much more significant than in bulk, solution, or suspension polymerization and initiator efficiencies in emulsion polymerization are often very low. Initiation kinetics in emulsion polymerization are defined in terms of the entry coefficient (p) - a pseudo-first order rate coefficient for particle entry. [Pg.64]

As a reactant molecule from the fluid phase surrounding the particle enters the pore stmcture, it can either react on the surface or continue diffusing toward the center of the particle. A quantitative model of the process is developed by writing a differential equation for the conservation of mass of the reactant diffusing into the particle. At steady state, the rate of diffusion of the reactant into a shell of infinitesimal thickness minus the rate of diffusion out of the shell is equal to the rate of consumption of the reactant in the shell by chemical reaction. Solving the equation leads to a result that shows how the rate of the catalytic reaction is influenced by the interplay of the transport, which is characterized by the effective diffusion coefficient of the reactant in the pores, and the reaction, which is characterized by the first-order reaction rate constant. [Pg.171]

** First-order reactions reaction **

** Pseudo first-order reaction, rate coefficient for **

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