Higher alcohols through CO hydrogenation over CoCu catalysts: Influence of precursor activation

Bimetallic CoCu model catalysts were investigated for the synthesis of higher alcohols using catalytic CO hydrogenation according to the Fischer-Tropsch technology. Emphasis was placed on revealing the influence of the activation conditions. Accordingly, catalyst precursors were activated in argon, hydrogen, syngas (CO/H2), and CO under atmospheric conditions and at elevated temperatures (370 °C). All catalyst precursors were prepared via oxalate coprecipitation in the absence of a classic support. Alcohol selectivities between 30 and ∼40% (up to ∼50% for the sum of alcohols and alkenes) were obtained with an Anderson-Schulz-Flory (ASF) chain lengthening probability maximizing the slate up to C6. Detailed catalysis and characterization studies were performed using a Co2Cu1 catalyst composition. The catalytic performances of the H2- and syngas-activated Co2Cu1 catalyst were similar. While the CO-activated catalyst shows significantly higher catalytic activity and ASF chain lengthening probability, the alcohol selectivities are lower than those of H2- or syngas-activated ones. All catalysts required time on stream for several hours to achieve steady-state catalytic performance. Co 2Cu1 catalysts were characterized by temperature- programmed decomposition (TPDec), in situ N2 physisorption (Brunauer-Emmett-Teller), transmission electron microscopy (TEM), and in situ X-ray photoelectron spectroscopy (XPS). The data indicate major restructuring occurs during activation. An "onion-like" graphitic carbon shell was observed via TEM for the CO-activated Co2Cu1 catalyst, which probably originated mainly from the Boudouard reaction (2CO + [ ] ad → Cad + CO2). This interpretation is in accordance with the TPDec profiles and XPS results. The latter also indicates that syngas and CO activation lead to higher than nominal Co/Cu surface ratios. The surface segregation of Co in the presence of CO atmospheres is interpreted on the basis of Co@Cu core-shell structured particles. © 2014 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Four decades of joy in mass spectrometry

Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career