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Abstract: Recently the authors developed a microkinetic model of methanol oxidation on silver [A. Andreasen, H. Lynggaard, C. Stegelmann, P. Stoltze, Surf. Sci. 544 (2003) 5–23]. The model successfully explains both surface science experiments and kinetic experiments at industrial conditions applying physically realistic parameters. Unfortunately the rate expression based on this microkinetic model is complex and impractical to apply for reactor engineering purposes. In this paper the rate expression is simplified by a number of approximations to make it suitable for practical applications without loosing significant accuracy. This is achieved by converting from a statistical thermodynamic description to a classical thermodynamic description resulting in a reduction of model parameters from more than 100 to a total of only 26. Further, other assumptions are applied including the most abundant reaction intermediate (MARI) approximation and the irreversible step (IS) approximation. This leads to further reduction in model complexity and in number of parameters. Computations verify that the performance of the model is preserved despite the reduction of the vast amount of parameters. [Copyright &y& Elsevier]

Abstract: After a brief review of the theory of mechanisms and kinetics of catalytic reactions, we formulate a number of mechanisms for the hypothetical reaction A2+2B→2AB and derive analytic expressions for rate of reaction, activation enthalpy, and reaction orders. After a discussion of a number of pitfalls in the analysis of measured kinetic data, we use the models with a range of realistic parameters to analyze degree of rate control, reaction orders, Arrhenius plots, the origin of volcano curves, and the origin compensation effects. Abrupt changes in slope in the Arrhenius plot are traditionally interpreted as the signature of a change in rate limiting step or the onset of diffusion phenomena. One of the main results of our analysis is that simple mechanisms with realistic parameters display such signatures without a change in rate limiting step and in the absence of transport phenomena. Finally, we extend our analysis to more complex reaction mechanisms by analysis of a number of important industrial reactions. [Copyright &y& Elsevier]

There are many publications that seek to explain the causes and effects of dementia for the non-learning disabled population and there is evidence of the benefit of supporting carers and of establishing support groups. However, there is much less published material aimed at people with learning disabilities, and little focus on the specific needs of people who share their homes and lives with other people with learning disabilities who develop dementia. This article is based on group work with residents who had expressed bewilderment at the gradual changes they were witnessing in two of their housemates with dementia with whom they had shared a home and friendships over many years. Employing a wide range of visual aids, equipment, role plays and exercises, we sought to make the explanation of dementia as accessible and concrete as possible. The group also provided a forum for the residents to talk about the effects of living with others who develop dementia. Evaluation showed how a relatively short intervention can result in positive changes for both the people with learning disabilities who develop dementia and their peers. [ABSTRACT FROM AUTHOR]

A simple microkinetic model for the oxidation of methanol on silver based on surface science studies at UHV and low temperatures has been formulated. The reaction mechanism is a simple Langmuir–Hinshelwood mechanism, with one type of active oxygen and one route to formaldehyde and carbon dioxide, respectively. The model explains observed reaction orders, selectivity, apparent activation enthalpies and the choice of industrial reaction conditions. More interesting the model disproves the notion that the mechanism deduced from surface science in UHV cannot be responsible for formaldehyde synthesis at industrial steady-state conditions. The present work therefore seriously questions the prevailing models of formaldehyde synthesis in the literature. One of the reasons for this controversy is that many of the models in the literature are derived from transient experiments exhibiting dynamic effects that are not present at steady state under industrial conditions. [Copyright &y& Elsevier]