Dynamic Analysis of Thermal Behaviour of a Laboratory Reactor Using a Process Simulator

A process simulator was used to study dynamic results from a laboratory‐scale tubular reactor for the oxidation of carbon monoxide (CO) with oxygen over Pt/alumina catalyst. Passive response experiments were used to obtain lumped values of the heat capacity and the overall heat transfer coefficient. Temperature profile experiments were used to obtain the only adjustable kinetic parameter: k°, the pre‐exponential portion of the rate constant. Integral reactor phenomena were studied: step‐decreases in the feed temperature, step‐changes in feed concentration, and ignition of the reactor by pressure. Simulated results provided good agreement with experiments.     

Numerical Investigation of Resonance Behaviour of a Tubular Packed‐Bed Reactor with Non‐Uniform Activity

The effects of periodic temperature perturbations at the inlet of a packed‐bed catalytic reactor were investigated for a system of non‐uniform catalyst activity that could arise through catalyst deactivation. A simplified model consisting of zones of active catalyst and inert packing of similar thermal properties was assumed. Simulations showed that large amplification, expressed as gain, can occur. The largest gain is observed at a resonance frequency. Both gain and resonance frequency depend on the number of layers of active catalyst and inert packing, the depth of the inert packing and catalyst layers.     

Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H₂SO₄ concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H₂SO₄, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%.     

Temperature excursions in packed bed reactors with an axial variation of catalyst activity

Research appears to be growing on a type of structured reactor in which catalyst activity varies or in which different catalysts are arranged in the reactant flow direction. These reactors offer improved selectivity for some classes of complex reactions under non-isothermal conditions or when composition modulation is employed. Our examination of the rather extreme case of alternating layers of inert and active catalyst indicate that this reactor structure accentuates wrong-way temperature excursions after a step-change in temperature and amplifies periodic input temperature disturbances. Experiments used a near adiabatic 2.5 cm diameter reactor packed with 3 mm particles of 0.2 wt.% Pt/Al₂O₃. Inert layers were just the 3 mm alumina particles. Step and triangular wave inputs of constant amplitude were used. Temperature response in the bed was measured by an axial array of computer-monitored thermocouples. Measurements were compared to those made on a homogeneous mixture of catalyst and support under identical input conditions. Simulation studies show that accentuation of the temperature excursions depends on layer thickness. Even first-order reaction kinetics show accentuated temperature excursions when layered beds are used.     

A kinetics study in CSTR using simultaneous temperature scanning and composition modulation: The alkaline hydrolysis of ethyl acetate

This work presents a new technique for reaction kinetic studies of liquid phase reactions in a CSTR. By simultaneously varying the reaction temperature (temperature scanning—TS) and reactant feed concentration (composition modulation—CM) while recording the output concentration, the technique allows, through the least‐square fitting of computer‐generated model data to the experimental time‐series, to obtain from a single experiment the reaction orders as well as both Arrhenius parameters. The alkaline hydrolysis of ethyl acetate was chosen to illustrate the technique, assuming a rate law in the form of a simple power law. The set of parameters that resulted in the minimum sum of squared errors was selected. These values were very close to those reported in literature. The technique saves much time and experimental resources.     

Temperature response to reactant concentration perturbations in a packed‐bed reactor

Unsteady‐state operations are known to enhance the performance of some packed‐bed reactor systems. However, negative effects of this type of operation should not be neglected. Temperature excursions developed during transients may accelerate some deactivation mechanisms, reducing catalyst lifetime and selectivity. Temperature response to perturbations in reactant concentration was studied for CO oxidation over Pt/Al₂O₃ in a packed‐bed reactor. Experiments were conducted in the CO concentration range for which multiple steady states are observed. Temperature and concentration profiles in the packed‐bed reactor at steady state were found to depend on the dynamic history of the reactor prior to the steady‐state condition.