Analysis Of Catalytic Reactors Research Articles

Area averaging of packed bed in continua conservation equations in axial flow

AbstractA novel averaging of the conservation equations for axial flow in packed beds is presented to express the momentum, continuity, and energy equations in terms of the cross‐sectional averages of concentration, temperature, and superficial velocity. The model integrates the radial fluctuations of the intrinsic variables into the partial differential equations of the model and presents a method for the design and analysis of catalytic reactors at a broad range of Reynolds numbers without the necessity of adjusting the operating conditions to minimize the impact of the radial profiles of velocity, concentration, and temperature. Since the control of the industrial reactors is dependent on the average values of the concentration and temperature, the model can be directly employed for design, optimization, and control processes with the added advantage of time and cost savings for both the numerical resolution and laboratory testing expenses. The model is limited to reaction systems with Péclet numbers of less than 700 with an average void fraction of for which the ratio of the bed length‐to‐particle diameter to particle Péclet number exceeds . The model was applied to the simulation of steam methane reforming (SMR). The results indicate that the average equations predict the responses of the SMR properly and thus the model could be reliably utilized for process design, operation, and control.

Remarks on the issue of structure sensitivity in heterogeneous catalysis: Activity and selectivity

Boudart has set forth the notion of the turnover number, N, i.e., the number of molecules reacting per second per site. In terms of the fundamental aspects of heterogeneous catalysis, per se, the concept of the turnover number is most potent in that variations in morphology (nature and structure) of surface sites with crystallite size variations (or for that matter alloying, heat treatment, etc.) are made manifest by measurements of N; and, as the author suggests, signal practical consequences with respect to catalytic reactor analysis and design, for catalyst systems prone to sintering emerge in the light of the turnover number concept. Finally, the potential importance of relative turnover numbers in affecting selectivity is noted. 9 references.

LABORATORY CATALYTIC REACTORS

A basic requirement in the analysis of catalytic reactors is a rate expression for the reaction concerned. In the design of any equipment the equations to be used contain certain basic physical-chemical coefficients whose values must be known. In the case of physical operations, these coefficients can usually be predicted from available correlations and the design of equipment is often carried out from first principles. But there is no method available by which the kinetic rate parameters of a chemical reaction can be predicted; thus experimental determination of these parameters is unavoidable.