Complexity and Challenges in Noncontact High Temperature Measurements in Microwave-Assisted Catalytic Reactors

The complexity and challenges in noncontact temperature measurements inside microwave-heated catalytic reactors are presented in this paper. A custom-designed microwave cavity has been used to focus the microwave field on the catalyst and enable monitoring of the temperature field in 2D. A methodology to study the temperature distribution in the catalytic bed by using a thermal camera in combination with a thermocouple for a heterogeneous catalytic reaction (methane dry reforming) under microwave heating has been demonstrated. The effects of various variables that affect the accuracy of temperature recordings are discussed in detail. The necessity of having at least one contact sensor, such as a thermocouple, or some other microwave transparent sensor, is recommended to keep track of the temperature changes occurring in the catalytic bed during the reaction under microwave heating

Minimization of Attrition and Breakage in an Airlift Crystallizer

Minimization of secondary nucleation by attrition in industrial crystallizers is a major challenge. In this work, a novel airlift crystallizer has been designed, constructed, and experimentally tested aiming at the reduction of attrition by using air for mixing instead of a stirrer or a circulation pump. It is experimentally demonstrated that in this crystallizer ideal growth, i.e., growth of crystals without any nucleation, can be approached up to a seeding load of 0.5% and crystal size of up to 600 μm. Attrition is considerably decreased in an airlift crystallizer compared to conventional impeller-mixed crystallizers. This air-mixed crystallizer enables the production of crystals of high quality and offers a large flexibility of the final crystal size by manipulating the air flow rate and the sparger design. Comparison of different designs showed a large effect of a gas disengagement zone on the performance of the crystallizer, especially when large crystals were desired. The disengagement zone allows high circulation velocities and thus good mixing without entrainment of the gas bubbles in the downcomer, approaching a uniform suspension of the crystals

Adsorption of Volatile Organic Compounds. Experimental and Theoretical Study

The adsorption of traces of five volatile organic compounds (VOCs) comprising butanal, 2-ethyl-2-hexenal, 2,6-dimethylcyclohexanone, 2,4,6-trimethylanisole, and 2,4,6-trimethylphenol from liquid toluene was investigated. Twenty-one commercial adsorbents of different classes were tested in batch adsorption experiments using the six-component mixture. The Na form of FAU zeolite (NaY) performed by far the best for the overall removal of these compounds from toluene, although removal of all six compounds to very low concentrations (<50 ppm) might not be feasible (in a single step). To further investigate the adsorption behavior of this zeolite, the ideal adsorbed solution theory (IAST) combined with Monte Carlo (MC) simulations was used. A force field was developed for these compounds that allows the computation of pure-component adsorption isotherms in zeolites using MC simulations. The pure-component isotherms are used as input in an IAST model to predict multicomponent adsorption behavior in zeolites. Simulations of binary and six-component mixture are compared to experimentally obtained adsorption isotherms. We show that (1) NaY zeolite performs best for the overall adsorption of the selected compounds from liquid toluene and (2) a combined molecular simulation–IAST approach can be used for this system to predict the adsorption behavior in NaY reasonably well