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Ert 316 CHEMICAL reaction engineering multiple reactions. By Noor Amirah Abdul Halim. Type of reactions. Parallel reactions Series reactions Complex reactions (parallel and series reactions) Independent reactions. Desired & undesired reaction. Selectivity & yields.
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Ert 316 CHEMICAL reaction engineeringmultiple reactions By Noor Amirah Abdul Halim
Type of reactions • Parallel reactions • Series reactions • Complex reactions (parallel and series reactions) • Independent reactions
Selectivity & yields Selectivity : the ratio of (reaction rate/mol/flowrate) of desired product to the (reaction rate/mol/flowrate) of undesired product Instantaneous selectivity Overall selectivity Instantaneous yield Overall yield Yield: the ratio of (reaction rate/mol/flowrate) of desired product formed to the (reaction rate/mol/flowrate) the reactant either fed or consumed Batch flow
Design equation for reactors involving multiple reactions reaction rate (r j) is a NET rate of reactions USE only molar flow rate (Fj) and concentration (Cj) DO NOT USE conversion (xj) DO NOT USE stoichiometry table to relate change in CB and change in CA
Parallel reactions • Selectivity for single reactant system Thus, Consider some of reactor operating scenarios to maximize the selectivity ( SD/U (max) )
Need highCAto favor Dproduction ( to increase selectivity) CA~ SD/U CA will always start at high value CA in a perfectly mixed CSTR is always at its lowest value
Need lowCAto favor Dproduction ( to increase selectivity) CA~ SD/U CA in a perfectly mixed CSTR is always at its lowest value
So, CAcannot be used as operating parameters to maximize the selectivity Thus the solution is: E = Activation Energy recall Thus, to achieve high selectivity: * higher energy requires higher temperature
Selectivity for two reactant system For high SD/U, maintain both CA and CB as high as possible