Characterisation of heterogeneous catalysts (Chemical Industries Series, Vol.15), Edited by Francis Delannay, Marcell Dekker Inc., New York, 1984, x + 424 pp., Price:SFr 185; ISBN 0-8247-7100-1 (original) (raw)

ChemInform Abstract: The Past, Present and Future of Heterogeneous Catalysis

ChemInform, 2012

This review highlights key catalytic discoveries and the main industrial catalytic processes over the last 300 years that involved commodities, fine chemicals, petrochemicals, petroleum transformation for fuels and energy supply, emission control, and so forth. In the past, discoveries have often followed events such as wars or embargos, whereas the current driving forces of studies, researches and then discoveries aim at a better understanding of catalytic processes, at reducing the costs of raw materials and processes, at developing new catalytic materials and at addressing environmental issues. This review focuses on the history of many catalytic industrial processes, environmental issues, catalytic materials, especially their expected catalytic properties, on catalyst characterisation by physical methods and development of in situ conditions, i.e., characterisation under actual working conditions with reactants and products analyzed on-line. Emphasis is also placed on high selectivity in catalytic reactions and the major challenges for the future, such as environmental issues, energy supply, pollution control for vehicles and industrial plants, air/VOCs/water purification, hydrogen sources and carbon dioxide storage/up grading, transformation of biomass as a promising source of raw materials, and catalytic water splitting perspectives. This review is a survey of heterogeneous catalysis and is not comprehensive but leads to the conclusion that, although many catalysts and catalytic processes have already been discovered and developed over the past century, many opportunities nevertheless exist for new developments, new processes and new catalytic materials. It follows that substantial challenges exist for the younger generation of researchers and engineers, as emphasized at the end of the manuscript.

ChemInform Abstract: Reaction Mechanism and Deactivation Modes of Heterogeneous Catalytic Systems

ChemInform, 2011

Solving the problem of catalyst deactivation is essential in process design. To do this, various aspects of the kinetics of processes with catalyst deactivation, and their different mechanisms, are discussed. Catalyst deactivation often cannot be avoided, but more knowledge on its mechanism can help to find kinetic means to reduce its harmful consequences. When deactivation is caused by coke, the generation of coke precursors is the determining step in the deactivation kinetics. Different types of deactivation were distinguished that lead to different evolution of the process. The phenomenon of non-uniform coking can be linked to catalyst surface non-uniformity. For the class of catalysts with more than one type of active sites, an explanation was suggested for the observed trends in the deactivation modes. For catalytic processes using catalyst particles of industrial size, the influence of intraparticle diffusion resistance is important. The analysis showed that for a number of processes, the decrease of the reaction rate due to deactivation is less under diffusion control. For certain reaction mechanisms, there exist operation conditions where the rate of the process under diffusion control exceeds the rate in the kinetic control regime. A significant problem is the change of selectivity in the course of catalyst deactivation. The selectivity may either decrease or increase, and depends on the reaction mechanism during deactivation. The changes are larger when there is no diffusion resistance. The intentional poisoning of catalysts and its influence on catalyst activity and selectivity for the process of ethylene oxide production was discussed.

Concluding remarks: progress toward the design of solid catalysts

Faraday Discussions, 2016

The 2016 Faraday Discussion on the topic "Designing new Heterogeneous Catalysts" brought together a group of scientists and engineers to address forefront topics in catalysis and the challenge of catalyst design-which is daunting because of the intrinsic nonuniformity of the surfaces of catalytic materials. "Catalyst design" has taken on a pragmatic meaning which implies the discovery of new and better catalysts on the basis of fundamental understanding of catalyst structure and performance. The presentations and discussion at the meeting illustrate rapid progress in this understanding linked with improvements in spectroscopy, microscopy, theory, and catalyst performance testing. The following essay includes a statement of recurrent themes in the discussion and examples of forefront science that evidences progress toward catalyst design. Catalysis and catalyst design Catalysis is the key to control of chemical change, in processes ranging from the biological to the technological. It is used to make products including chemicals, fuels, materials, food, beverages, and personal care products, and together these have a value of roughly 5-10 trillion dollars (US) per year worldwide. Catalysis is also essential for the removal of environmental pollutants such as those generated in motor vehicles and fossil fuel-fired power plants. Thus, the science underlying catalytic technology is essential. Catalysis science is also challenging, because almost all large-scale industrial catalysts are solids. These work at their surfaces-and these surfaces are notoriously nonuniform in both composition and structure, often being substantially different from simple terminations of the bulk material-and they undergo changes when exposed reactants.

The use of a localized heating protocol in heterogeneous catalysis

Journal of Molecular Catalysis A: Chemical, 2003

The catalyzed decomposition of ethylene has been used as a probe reaction to ascertain the advantages of exclusive heating of a supported metal catalyst by a current stimulated technique. This approach has been found to result in the elimination of certain side reactions generally encountered in conventional catalytic reactor systems associated with thermal decomposition of gas phase molecules. We have found that by restricting the heated zone to the catalyst surface the ubiquitous formation of pyrolytic carbon arising from thermal decomposition of hydrocarbons can be effectively mitigated. In addition, major differences in the selectivity patterns were observed from the localized heating system compared to that found when the same catalyst was reacted in a conventional flow system. The difference in behavior of the catalyst under these diverse conditions is rationalized according to the notion that the flow of an electric current through the support not only served to resistively heat the sample, but also induced electronic perturbations in the metal surface atoms.

Characterization of acidic and basic properties of heterogeneous catalysts by test reactions

2005

4.3 Hydrotalcite derived from mixed Mg-Al oxides………………………………………...61 4.3.1 Acid-base properties of the hydrotalcite derived from mixed magnesium aluminium oxides…………………………………………………………………………………63 4.3.2 X-ray diffraction (XRD)……………………………………………………………..64 4.3.3 Infrared spectroscopy (FTIR)………………………………………………………..66 4.3.4 Structural and chemical composition of the mixed magnesium aluminium oxides…68 4.3.5 BET measurements…………………………………………………………………..69 4.4. Methyl butynol conversion……………………………………………………………...73 4.4.1 Catalytic activity of methyl butynol over different silica alumina with different ratios at different reaction temperatures 120 °C, 180 °C……………………………73 4.4.2 Influence of reaction temperature and treatment preparations of the sample reaction behavior……………………………………………………………..77 4.4.3 Influence of the deactivation process on the methyl butynol catalytic activity ……..83 4.4.4 The dependency of the selectivity of 3-methyl-3-buten-1-yne as a function of the conversion depending on the silica content over different l ratios…………………...86 4.4.5 The formation of 3-methyl-3-butyn-2-one as a function of the conversion depending on the silica content over different silica alumina ratios……………………………..87 4.4.6 Correlations and formation of 3-methyl-3-butyn-2-one as primary product over silica alumina solids………………………………………………………………….89 4.5 Effect of water on the conversion of methyl butynol……………………………………93 4.6 Determination of activation energy in the methyl butynol conversion………………….96 4.7 Basicity of hydrotalcite derived from mixed magnisium oxides studied by methyl butynol test reaction……………………………………………………………104 4.8 Conversion of isopropanol……………………………………………………………...108 4.9 Knoevennagel condensation…………………………………………………………….112 5. Conclusions………………………………………………………………..118 6. References…………………………………………………………………122 7. Appendix…………………………………………………………………..128