Catalysis by Gold: Why Size Matters

Bulk gold is the most inert metal of all, however, when gold is finely dispersed on a support, it can be a very active catalyst for oxidation and hydrogenation reactions. X-ray absorption spectroscopy showed that the smaller the gold particles are, the shorter the gold–gold bond length is. The smaller particles also have an altered electronic structure, as they undergo less hybridization between the s, p, and d orbitals than the larger particles. The d band narrows and moves closer to the Fermi level. As a result, hydrogen, oxygen, and CO adsorb on the metal surface and the nano-sized metal particles can become catalytic

Understanding a Heterogeneous Catalyst in Action

The role of catalysis in the clean production of energy and chemicals will become increasingly important and new catalysts must be developed. To improve the activity, selectivity, and stability of a heterogeneous catalyst, the electronic and geometric structure of the catalytically active site must be controlled. In situ characterization combined with kinetic analysis provides insights into the functioning of a heterogeneous catalyst. This aids the synthesis of a new generation of catalysts that converts new feedstocks, which are derived from sustainable sources, into energy and chemicals

Catalytic Conversion of Methane to Methanol Using Cu-Zeolites

The conversion of methane to value-added liquid chemicals is a promising answer to the imminent demand for fuels and chemical synthesis materials in the advent of a dwindling petroleum supply. Current technology requires high energy input for the synthesis gas production, and is characterized by low overall selectivity, which calls for alternative reaction routes. The limitation to achieve high selectivity is the high C–H bond strength of methane. High-temperature reaction systems favor gas-phase radical reactions and total oxidation. This suggests that the catalysts for methane activation should be active at low temperatures. The enzymatic-inspired metal-exchanged zeolite systems apparently fulfill this need, however, methanol yield is low and a catalytic process cannot yet be established. Homogeneous and heterogeneous catalytic systems have been described which stabilize the intermediate formed after the first C–H activation. The understanding of the reaction mechanism and the determination of the active metal sites are important for formulating strategies for the upgrade of methane conversion catalytic technologies

Вероятностно-детерминированная модель расчета безопасного расстояния при разливе топлива

В статье рассматриваются основные опасные факторы при эксплуатации автозаправочных станций, опасные факторы топливных жидкостей, их физические и физико-химические свойства. Основная задача в статье - проанализировать все возможные риски, возникающие при эксплуатации АЗС, выявить наиболее вероятные неблагоприятные события, способные привести к повреждениям и разрушениям АЗС. Проанализировать возможные сценарии развития аварии для выявления наиболее опасного. Данные исследования позволят в дальнейшем использовать математическую модель для определения радиуса поражения зданий, сооружений и населения, и определения безопасного расстояния для опасных объектов - АЗС.The article deals with the main hazards during the operation of gasoline stations, the dangerous factors of fuel fluids, their physical and physicochemical properties. The main task in the article is to analyze all possible risks arising from the operation of the filling station, to identify the most likely adverse events that can lead to damage and destruction of the filling stations. Analyze possible scenarios for the development of an accident to identify the most dangerous. The given researches will allow to use in the further mathematical model for definition of radius of destruction of buildings, constructions and the population, and definition of a safe distance for dangerous objects - the gas station

Chemicals from Lignin by Catalytic Fast Pyrolysis, from Product Control to Reaction Mechanism

Conversion of lignin into renewable and value-added chemicals by thermal processes, especially pyrolysis, receives great attention. The products may serve as feedstock for chemicals and fuels and contribute to the development of a sustainable society. However, the application of lignin conversion is limited by the low selectivity from lignin to the desired products. The opportunities for catalysis to selectively convert lignin into useful chemicals by catalytic fast pyrolysis and our efforts to elucidate the mechanism of lignin pyrolysis are discussed. Possible research directions will be identified

Modern X-ray spectroscopy:XAS and XES in the laboratory

X-ray spectroscopy is an important tool for scientific analysis. While the earliest demonstration experiments were realised in the laboratory, with the advent of synchrotron light sources most of the experiments shifted to large scale synchrotron facilities. In the recent past there is an increased interest to perform X-ray experiments also with in-house laboratory sources, to simplify access to X-ray absorption and X-ray emission spectroscopy, in particular for routine measurements. Here we summarise the recent developments and comment on the most representative example experiments in the field of in-house laboratory X-ray spectroscopy. We first give an introduction and some historic background on X-ray spectroscopy. This is followed by an overview of the detection techniques used for X-ray absorption and X-ray emission measurements. A short paragraph also puts related high energy resolution and resonant techniques into context, though they are not yet feasible in the laboratory. At the end of this section the opportunities using wavelength dispersive X-ray spectroscopy in the laboratory are discussed. Then we summarise the relevant details of the recent experimental laboratory setups split into two separate sections, one for the recent von Hamos setups, and one for the recent Johann/Johansson type setups. Following that, focussing on chemistry and catalysis, we then summarise some of the notable X-ray absorption and X-ray emission experiments and the results accomplished with in-house setups. In a third part we then discuss some applications of laboratory X-ray spectroscopy with a particular focus on chemistry and catalysis.</p

Operando Photoelectron Photoion Coincidence Spectroscopy to Detect Short-lived Intermediates in Catalysis

Understanding the reaction mechanism is critical yet challenging in heterogeneous catalysis. Reactive intermediates, e.g., radicals and ketenes, are short-lived and often evade detection. In this review, we summarize recent developments with operando photoelectron photoion coincidence (PEPICO) spectroscopy as a versatile tool capable of detecting elusive intermediates. PEPICO combines the advantages of mass spectrometry and the isomer-selectivity of threshold photoelectron spectroscopy. Recent applications of PEPICO in understanding catalyst synthesis and catalytic reaction mechanisms involving gaseous and surface-confined radical and ketene chemistry will be summarized