Brent E. Handy

Role of Iron Carbonyls in the Inhibition of Oxygen Activation for the Oxidation of CO Catalyzed by Iron Oxide‐Supported Gold

Iron oxide-supported gold samples were prepared by co-precipitation from HAuCl(4) and Fe(NO(3))(3). The activities of the samples as CO oxidation catalysts were tested without thermal treatment and following treatments in flows of He and O(2) at various temperatures. It was found that the untreated samples and those treated in a flow of He at 150 °C were more active than samples that had been treated at 400 °C in either a flow of O(2) or of He. Infrared spectra recorded during CO oxidation catalysis indicate the presence of bonded CO molecules to cationic gold on all samples, whereas spectra of the least active catalysts indicate a predominant presence of Fe(2+) carbonyls, which were highly stable under the conditions of our experiments. Our results indicate that in the least active samples the Fe(2+)-bound CO blocks sites that would otherwise be available for oxygen activation.

Sensor placement in temperature-based control strategies to improve baseline stability in Tian–Calvet microcalorimeters

We address the issue of hardware placement in the development of robust temperature control strategies that can be used to maintain a stable baseline during microcalorimetric experiments. The two different control loops, each defined by the location of sensor within the calorimeter that is used to achieve control, were first developed and then tested in a fully instrumented experimental system. Both control strategies were structured on proportional-integral-derivative controllers, after which calorimetric experiments were carried out to test the efficiency and robustness of the corresponding methodology. Results indicate that sensor placement plays a fundamental role in the controlled baseline stability and that is better to place the sensing device closer to the heater than to the central core. As part of this study, comparisons were also done against a previously reported control scheme based on heat-flow measurements. Results indicate that controlling only one variable, either temperature or heat flow is sufficient to compensate for heater-induced noise, but not for external fluctuations for which a combined strategy may be necessary.

Lewis–Brønsted induction acidity in SBA-15 modified with Zr and P

Abstract In this work, we present the synthesis of SBA-15 materials modified with 6 and 9 mol.% of Zr and P, respectively. Silanol SBA-15 groups were detected by Fourier transform infrared spectroscopy. X-ray diffractograms revealed that the typical hexagonal arrangement of SBA-15 was preserved after Zr and P introduction, and the structure was confirmed by transmission electron microscopy. After the Zr introduction, the morphology of SBA-15 changed from fibrous particles to a semi-spherical shape according to scanning electron microscopy, while nitrogen physisorption revealed the stability of the textural materials after the P introduction. The infrared spectra of pyridine adsorption indicated that the Zr and P incorporation into SBA-15 generated adequate Lewis and Br⊘nsted acidities to carry out methanol dehydration and direct the selectivity towards dimethyl ether, with medium-strong acid sites being responsible for obtaining up to 99% selectivity towards dimethyl ether.

PID-Based Thermal Control in Heat Conduction Micro-Calorimeters

Strategies based on the principle of heat flow and temperature control were implemented, and experimentally tested, to increase the sensitivity of a Tian-Calvet microcalorimeter for measuring heats of adsorption. Here, both heat-flow and temperature control schemes were explored to diminish heater-induced thermal variations within the heat sink element hence obtaining less noise in the baseline signal. PID controllers were implemented within a closed-loop system to perform the control actions in an calorimetric setup. The experimental results demonstrate that the heat flow control strategy provided a better baseline stability when compared to the temperature control. A modified control strategy is then suggested to maintain a stable core temperature and signal noise level in the system.Copyright