Adsorption Studies on Clean and Sulphur-Poisoned Supported Copper Catalysts

The adsorption of methanol, carbon monoxide, and carbon dioxide has been studied in a pulse flow system on "clean" and hydrogen sulphide poisoned alumina-supported copper, a commercial copper/zinc oxide/alumina catalyst, zinc oxide, and alumina surfaces. Adsorption of hydrogen sulphide was also studied, while the interaction of methanol and carbon monoxide with "clean" surfaces of the above catalysts was investigated by FTIR. The catalytic decomposition of methanol on copper-based catalysts resulted in the formation of carbon monoxide, carbon dioxide and hydrogen. The formation of carbon dioxide was attributed to the interaction of the product carbon monoxide with the unreduced oxide on the catalyst surface. Use of a carbon monoxide flow as a reducing agent to ensure the complete reduction of copper-based catalysts surfaces, showed that carbon monoxide and hydrogen are the major products of the decomposition reaction. The reaction of methanol on zinc oxide also resulted in the formation of carbon monoxide, carbon dioxide and hydrogen. Interaction of carbon monoxide with the oxide surface was responsible for the formation of carbon dioxide, as was evident from the change in the oxide colour from grey to blue during methanol interaction, suggesting a conversion of the oxide to a metallic zinc. At higher reaction temperatures and increased methanol exposure, trace amounts of methane were formed. On an alumina surface, methanol interacts dissociatively to form carbon monoxide and methane as major products, together with small amounts of, carbon dioxide and water. Sulphur was found to have a great influence on the catalytic activity. The presence of small concentrations of H2S on the catalyst surface greatly reduced the catalytic activity towards methanol decomposition, but no change in the catalyst selectivity was observed due to this poisoning effect. 14C-labelled carbon monoxide and carbon dioxide were used to study the extent of the adsorption and the effect of sulphur poisoning on copper-based catalysts. The results showed that carbon monoxide interacts with copper-based catalysts forming a strongly held carbonate species, due to the presence of unreduced oxide. Desorption experiments show two adsorption peaks corresponding to a relatively weakly adsorbed and strongly held species. No significant carbon monoxide adsorption was observed on the oxide surfaces. C-carbon dioxide interacts with the catalyst surfaces in a similar way to that of carbon monoxide; significant adsorption occurs on the oxide surfaces. Preadsorbed sulphur reduces the extent of the adsorption of both carbon monoxide and carbon dioxide, by weakening the adsorbate-metal bond, as indicated by the shift of the desorption peaks to lower temperatures. 35S-H2S strongly adsorbs on all surfaces. The adsorption is irreversible on Cu/Al2O3, Cu-ZnO/Al2O3 and ZnO, with zinc oxide bulk zinc sulphide is formed. Trace amounts of water are found to increase the ability of the oxide to adsorb H2S. FTIR investigations of the interaction of methanol shows that, on copper catalysts, methoxy species are formed, while on zinc oxide the methoxy species decompose to form a carbonato species as well as carbon monoxide and carbon dioxide. On alumina bands due to methoxy, formate, CO, CO2 and water are observed. The methoxy species decomposes to a formate species upon being heated

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

Composition System in the experience of the artist Georges Braque

Our research deals ( Composition System in the experience of the artist Georges Braque) addresses Based on the importance of research as an effective energy, the diversity of material and experimentation carried out by the artist George Braque , through his transitional phases in his constructive system between analysis and composition in his artistic output. In its methodological frameworks Chapter I highlighted the problem of research and its importance and came up with several questions for the problem: What constructive composition system is followed by the artist in his achievements for his artistic experience? What techniques and mechanisms do I adopt in shaping his artistic achievement? Influential or associated references in George Braque artistic experience that contributed to the creation of those intellectual variables or theses through his transition stages within the artistic achievement? Is the artist’s experience, an extension or a reference for many contemporary art products, which we are witnessing today in the arena of art formation?

Boolean language operations on nondeterministic automata with a pushdown of constant height

We study the cost of Boolean operations on constant height nondeterministic pushdown automata, i.e., on the ordinary pushdown automata with a limit on the size of the pushdown. For intersection, we show an exponential simulation and prove that the exponential blow-up is necessary in the worst case. For union, instead, we provide a linear trade-off while, for complement, we show a double exponential simulation and prove a single exponential lower bound. The same gaps for Boolean operations with regular languages have been shown for traditional nondeterministic automata with unrestricted pushdown

Boolean language operations on nondeterministic automata with a pushdown of constant height

We study the size-cost of Boolean operations on constant height nondeterministic pushdown automata, i.e. on pushdown automata with a constant limit on the size of the pushdown. For intersection, we show an exponential simulation and prove that the exponential blow-up is necessary. For union, instead, we provide a linear trade-off while, for complement, we show a double-exponential simulation and prove a single-exponential lower bound

Removing nondeterminism in constant height pushdown automata

We study the descriptional cost of removing nondeterminism in constant height pushdown automata - i.e., pushdown automata with a built-in constant limit on the height of the pushdown. We show a double-exponential size increase when converting a constant height nondeterministic pushdown automaton into an equivalent deterministic device. Moreover, we prove that such a double-exponential blow-up cannot be avoided by certifying its optimality. As a direct consequence, we get that eliminating nondeterminism in classical finite state automata is single-exponential even with the help of a constant height pushdown store