For the heterogeneous irreversible catalytic reaction A(g) + B(g) → C(g) where surface reaction between adsorbed A and B to form adsorbed C is rate-controlling, what is the resulting rate expression (using KA, KB, KC as adsorption equilibrium constants and k as the surface reaction rate constant)?
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Answer: D. k KAKB pApB / (1 + KApA + KBpB + KCpC)2
Explanation
Dual site surface reaction rate control introduces adsorption equilibrium terms for both reactants and products. When the surface reaction between adsorbed A and B is rate-limiting, both reactant sites appear in the denominator. Squaring the denominator terms accounts for dual site participation in the surface reaction mechanism. Heterogeneous catalysis involves reactant adsorption, surface reaction between adsorbed species, and product desorption. Langmuir Hinshelwood mechanisms model catalytic kinetics by assuming specific steps control the overall reaction rate. Adsorption equilibrium constants quantify how strongly chemical species bind to active sites on the catalyst surface.
Designing industrial catalytic reactors requires accurate rate expressions derived from fundamental surface mechanisms. Petrochemical synthesis processes heavily utilize Langmuir Hinshelwood kinetic models for reactor simulation. Understanding rate-controlling steps helps engineers optimize operating pressures and temperatures for maximum yield. Option A lacks product adsorption terms in the denominator, ignoring the presence of adsorbed species C. Option B includes reactant adsorption terms but misses product inhibition effects in the denominator. Option C features product adsorption terms in the denominator but omits the necessary squaring for dual site reactions.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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