Natural selection, reaction-diffusion process

Inert gas pressure, temperature, and conversion were selected as these are the critical variables that disclose the nature of the basic rate controlling process. The effect of temperature gives an estimate for the energy of activation. For a catalytic process, this is expected to be about 90 to 100 kJ/mol or 20-25 kcal/mol. It is higher for higher temperature processes, so a better estimate is that of the Arrhenius number, y = E/RT which is about 20. If it is more, a homogeneous reaction can interfere. If it is significantly less, pore diffusion can interact. 

Catalyst selection involves two features productivity and selectivity. The process rate is a subtle combination of four limiting steps adsorption/desorption of reac-tants/product, surface reaction between species, diffusion through pores and diffusion through external film. Pore structure, surface area, nature and distribution of active sites play a crucial role in forming the process rate at the level of catalyst... 

Fluid flow, heating and composition, which change by reaction or by transfer at one interface, represent the specificity of the chemical engineering processes. The response of a system to the applied effects that generate the mentioned cases depends on the nature of the materials involved in the process. All the properties of the materials such as density, viscosity, thermal capacity, conductivity, species diffusivity or others relating the external effects to the process response must be included as variables. The identification of these variables is not always an easy task. A typical case concerns the variation of the properties of the materials, in a nonlinear dependence with the operation variables. For example, when studying the flow of complex non-Newtonian fluids such as melted polymers in an externally heated conduct, their non-classical properties and their state regarding the effect of temperature make it difficult to select the properties of the materials. 

The nature of substrate selects the type of dye needed, and methods of dye application. The development of new substrates led to new dyes and dyeing methods and influenced the dyeing technology in a fundamental manner. The dyeing of any substance (e.g., textile fiber) is based on a physico-chemical equilibrium process, namely diffusion and sorption of dye molecules or ions. These processes may be followed by chemical reactions in the substrate, for example, in the application of vat, reactive, azoic, and chrome dyes [9]. 

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