Kinetics propane cracking

Keywords Propane cracking Density fimctional methods BMK Thermochemistry Kinetics CCSD(T) calculations Composite models... 

In commercial practice, propane is often cracked at percent decompositions above 90%. C4+ paraffins are commonly cracked at 90% to nearly 100% decomposition. A kinetic model fitting decomposition data in the 90+% range should, therefore, be valuable. 

Mechanistic modeling has been useful in studying pyrolysis kinetics at low conversion (4,5,6). Few attempts have been reported at the high conversion levels of commercial cracking (7). This stems from the large number of species and free radicals and of their associated reactions, which increases substantially with conversion and leads to excessive computation time. In addition, when one considers that precise pyrolysis mechanisms, for even a simple feedstock such as propane (8), are still subject to dispute, it is clear that more empirical models will continue to dominate commercial applications. 

The kinetics of the pyrolysis of -butenes with propane and -butane were studied to obtain the relative rate constants and so calculate the effective relative reactivities towards Me and As part of a detailed study on hydrocarbon cracking, UHF... 

The cracking of propane to produce ethylene is represented by the simplified kinetic model ... 

Berner, U., Faber, E., Scheeder, G. Panten, D. 1995. Primary cracking of algal and landplant kerogens kinetic models of isotope variations in methane, ethane and propane. Chemical Geology, 126(3/4), 233-245. 

The possible influence of nonideal flow is to be estimated. For this approximate study assume that the temperature in the tubes is constant and that the reaction gases are completely mixed in the U-bend at the end of each tube section. The cracking reactions are approximately first order and kinetic data indicate that three tube sections would be required to obtain 96% conversion of the propane for plug flow in each section. The flow rate in such that the Reynolds number in the tubes in 10,000. For these conditions the axial dispersion parameter, Djudi, where d the tube... 

Example 9.1-1 Derivation of a Kinetic Equation from Experiments in an Isothermal Tubular Reactor with Plug Flow. Thermal Cracking of Propane... 

Tdjle 2 Thermal cracking of propane. Rate versus conversion, k-vaiues from the integral and differential method of kinetic analysis... 

In a naphtha, 200-300 components may lead to these olefins, so that all the networks have to be developed and their ethylene production summed up. It is clear that a realistic kinetic analysis of the cracking of a complex hydrocarbon mixture into olefins is not a simple task. The rate parameters of the elementary steps can only be accessed by an investigation of the kinetics of a number of specific feed components, preferably with increasing complexity. Even for the paraffin family, cracking ethane and propane will not suffice because they do not generate all the steps encountered with the higher members. 

The results given in Section 9.3.2 for the thermal cracking of naphtha and of a mixture of ethane-propane were obtained with very detailed radical kinetic schemes for these processes [Willems and Froment, 1988a, b]. The present problem formulates ethane cracking in terms of a drastically simplified molecular model containing 7 reactions. This reaction scheme and the corresponding kinetic model was derived from the radical scheme developed by Sundaram and Froment [1977]. Table 1 gives the kinetic parameters of these reactions. It should be mentioned that the kinetic parameters for the reverse reactions (2) and (5) were obtained from equilibrium data. Table 2 is the matrix of stoichiometric coefficients ay defined by... 

In this paper, we describe a computational study of the cracking reactions of propane and the production of olefins, especially propene, as a preUminary step in our research of gas-phase production of propylene oxide. The purpose of the smdy is twofold. On the one hand, we aim to compare different computational schemes applied to a subset of reactions for which experimental data exist On the other hand, we want to obtain precise estimates of the thermochemistry and kinetics of the radical chain initiation, propagation and termination reactions involved in the mechanism. Previous computational and experimental studies on this area of research have been performed by several authors, which results we will use to compare to our own. 

Modeling of thermal cracking of propane was performed by Sundaram and Froment [46] on the basis of experimental work by Van Damme et al. [47]. The kinetics of mercury-photosensitized decomposition of propane was studied in a pair of papers by Papic and Laidler [14, 15] in the seventies. 

Sundaram, K. M. and G. F. Froment, 1977. Modeling of thermal cracking kinetics. 1. Thermal cracking of ethane, propane and their mixtures. Chemical Engineering Science, 32, 601. 

In the work of Lobera et al. (2008), Li et al. (201 la), and Fsgoo s et al. (2011), cracking of propane was also included in their kinetic models. They all used power-law models and assumed that the reaction was first order to propane. It is worth mentioning that the C—C break from both... 

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