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Gas phase toluene hydrogenation is investigated over Pt/Al 2 O 3 catalyst with temperature ranging from 75 to 125°C and at atmospheric pressure. Strong activity variations are observed during long duration experiments. These variations are thoroughly investigated and a mechanistic model is proposed with dynamic adsorption activity of the reactants, used to explain the decrease in catalyst activity. This model considers competitive adsorption behaviour of the reactants and dissociative adsorption of hydrogen. Such a model can also be used to explain the strong metal-support interaction (SMSI) effect induced by the catalyst support. The decrease in activity after temperature maxima as previously observed can also be addressed by the approach presented. A comparison of activity variation at different residence times i.e. 20-50 kg cat ÁsÁmol -1 and different hydrogen and toluene partial pressures is also simulated.

Acetic acid, a common biomass transformation residue, can be converted into acetone by direct ketonization in the gas phase over g-Fe 2 O 3 (maghemite) pre-activated at 450 1C under air. This reaction was performed in a continuous flow reactor with varying temperature from 250 to 300 1C and different carrier gases. Using N 2 as carrier gas, the activity of the iron based catalyst normally increased with increasing temperature and contact time and remained constant under stationary operating conditions. A slight decrease of activity was observed using a N 2 /CO 2 mixture as carrier gas. A strong enhancement of the activity was observed when H 2 was introduced in the carrier gas, as a N 2 /H 2 or CO 2 /H 2 mixture. This improvement could be attributed to the modification of the oxidation state of the iron catalyst used for which in situ characterisation is still to be performed.

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Undergraduate chemical engineering students should be trained differently from other disciplines in control theory. ASPEN HYSYS provides basic modules for the unit operation with dynamics that can be used in elucidating the intended principles to control students virtually, which are not available in MATLAB (SIMULINK). A total of six workshops are designed. The laboratory course starts by familiarizing students to dynamic feature of the commercial software. Students are then introduced to operational safety aspects, by solving a runaway CSTR model. Importance of transfer functions is elucidated as an approach to integrate with different other electrical devices. Frequency response analysis is then presented using the transfer function to visualize instability. Two experiments are designed for PID controller so that students can envisage the affect of tuning parameters on absolute integrated error, offset, and regulation of manipulated variable. Different tuning methods and their objectives are also explained. The comparison between SIMULINK and HYSYS simulation is discussed. Modules are provided as supplement material. Surveys and direct assessment tools evaluate student's understanding of the course. The results are compared with the previous session using SIMULINK as laboratory tool presenting higher satisfaction with HYSYS. ß 2016 Wiley Periodicals, Inc. Comput Appl Eng Educ 24:887-898, 2016; View this article online at wileyonlinelibrary.com/journal/cae;

Supercritical carbon dioxide (S-CO2) Brayton cycles (BC) are soon to be a competitive and environment friendly power generation technology. Progressive technological developments in turbo-machineries and heat exchangers have boosted the idea of using S-CO2 in a closed-loop BC. This paper describes and discusses energy and exergy analysis of S-CO2 BC in cascade arrangement with a secondary cycle using CO2, R134a, ammonia, or argon as working fluids. Pressure drop in the cycle is considered, and its effect on the overall performance is investigated. No specific heat source is considered, thus any heat source capable of providing temperature in the range from 500 °C to 850 °C can be utilized, such as solar energy, gas turbine exhaust, nuclear waste heat, etc. The commercial software ‘Aspen HYSYS version 9’ (Aspen Technology, Inc., Bedford, MA, USA) is used for simulations. Comparisons with the literature and simulation results are discussed first for the standalone S-CO2 BC. Energy analysis is done for the combined cycle to inspect the parameters affecting the cycle performance. The second law efficiency is calculated, and exergy losses incurred in different components of the cycle are discussed.

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