Novel nano-semiconductor film layer supported nano-Pd Complex Nanostructured Catalyst Pd/Ⓕ-MeOx/AC for High Efficient Selective Hydrogenation of Phenol to Cyclohexanone
Supported metal as a type of heterogeneous catalysts are the most widely used in industrial processes. High dispersion of the metal particles of supported catalyst is a key factor in determining the performance of such catalysts. Here we report a novel catalyst Pd/Ⓕ-MeOx/AC with complex nanostructured, Pd nanoparticles supported on the platelike nano-semiconductor film/activated carbon, prepared by the photocatalytic reduction method, which exhibited high efficient catalytic performance for selective hydrogenation of phenol to cyclohexanone. Conversion of phenol achieved up to more than 99% with a lower mole ratio (0.5%) of active components Pd and phenol within 2 h at 70 °C. The synergistic effect of metal nanoparticles and nano-semiconductors support layer and the greatly increasing of contact interface of nano-metal-semiconductors may be responsible for the high efficiency. This work provides a clear demonstration that complex nanostructured catalysts with nano-metal and nano-semiconductor film layer supported on high specific surface AC can yield enhanced catalytic activity and can afford promising approach for developing new supported catalyst.
Pd/MgO: Catalyst Characterization and Phenol Hydrogenation Activity
The gas-phase hydrogenation of phenol (423≤T≤573 K) has been studied over a 1% w/w Pd/MgO catalyst prepared by impregnation of MgO with (NH4)2PdCl6. The catalyst precursor was activated by precalcination in air at 473 K followed by reduction in hydrogen at 573 K. Temperature-programmed reduction/desorption (monitoring H2 consumption and NH3, H2O, CO, and CO2 release) has revealed the presence of ammonium carbonate and/or ammonium hydrogen carbonate on the active surface in addition to a metallic palladium component. Whereas the latter was not detectable by X-ray diffraction due to the high metal dispersion, transmission electron microscopy revealed that the mean palladium particle diameter is 1.3±0.2 nm, which corresponds to a palladium dispersion of DPd=71%. Besides conventional and high-resolution transmission electron microscopy, selected area electron diffraction provides some insight into the fine structure of the palladium crystallites. Impregnation followed by calcination is shown to transform MgO to Mg(OH)2 while the additional reduction step generates a surface phase that is composed of both needle-like Periclase MgO and Mg(OH)2. X-ray photoelectron spectrometric analyses of the activated catalyst has established the presence of zero-valent palladium which appears to be electron rich as a result of metal–support interaction; a degree of palladium charging is also evident as well as residual surface chlorine. The effects on fractional phenol conversion and reaction selectivity of varying such process variables as reaction time, temperature, and phenol molar feed rate are considered and the possibility of thermodynamic limitations is addressed. Hydrogenation was observed to proceed in a stepwise fashion with cyclohexanone as the partially hydrogenated product and cyclohexanol as the fully hydrogenated product. The catalyst delivered a 96% selectivity with respect to cyclohexanone production at 423 K but the cyclohexanone yield decreased at higher temperatures as conversion declined and cyclohexanol was increasingly preferred. Conversion and selectivity were both stable with prolonged catalyst use, i.e., time on stream in excess of 55 h.
Commentary: Scholarship as a Way of Life—Character and Virtue in the Age of Big Humanities
From the Renaissance to the nineteenth century, most European scholars considered moral cultivation as the primary purpose of the humanities. The humanities were human not just because they concerned the products of the human mind but also because they transformed scholars and students into better human beings. During the late nineteenth and early twentieth centuries, the rise of Big Humanities questioned this moral purpose. However, Big Humanities also reemphasized the importance of epistemic virtues for scholarship. The language of epistemic virtues helped scholars create new communities of learning and scholarship. Within these communities, the language of virtues established common standards of collaboration and granted scholars a sense of purpose. Many of these scholars also continued to associate epistemic virtues with moral virtues.