https://ris.utwente.nl/ws/files/6651605/Lercher96infra-red.pdf

Infrared studies of the surface acidity of oxides and zeolites using adsorbed probe molecules

IR spectroscopy in catalysis

An overview about the effect of co-metal on the performance of Pd in bimetallic catalysts is presented. In the first part, the promotion of monometallic catalysts by addition of a second metal is described from a general point of view in terms of: (i) electronic effects; (ii) geometric effects; (iii) the occurrence of mixed sites; and (iv) the disappearance of the β-PdH phase. The second part presents the main methods to prepare bimetallic catalysts through the unselective and selective depositions of the co-metal precursor and the use of heterobinuclear complexes. The influence of preparation methods on the chemical state and the spatial distribution of both components are highlighted. In the last part, a short overview is given about the influence of co-metal addition on some important reactions in which Pd is the reference active phase: (i) selective hydrogenation of highly unsaturated aliphatic hydrocarbons; (ii) hydrogenation of aromatics or hydrodearomatisation; (iii) hydrogenation of nitrogen-containing compounds; (iv) reactions involving CO; and (v) hydrodechlorination.

Bimetallic palladium catalysts: influence of the co-metal on the catalyst performance

Publisher Summary This chapter discusses the specific poisoning of a catalyst surface. A probe molecule other than the reactant is preadsorbed as a poison and its effect on the catalytic activity studied. From the nature of interaction of this probe molecule with the surface sites one may obtain information regarding the chemical nature of these sites and from the number of poisoning molecules necessary to bring the activity to zero one may estimate an upper limit of the active site density. Besides the obvious difficulty to discriminate between surface sites that purely absorb the probe molecule and those that are involved in the catalytic process as active sites, there are a number of other limitations making it difficult to obtain clear-cut information on the nature of active sites. The chapter describes the proposals that are indispensable for a proper application of this method and the precautions that have to be kept in mind while drawing conclusions from specific poisoning experiments. The chapter illustrates two examples—namely, the dehydration of alcohols and the isomerization of olefins on alumina.

Specific Poisoning and Characterization of Catalytically Active Oxide Surfaces

Review of methods for the catalytic hydrogenation of carboxamides.

Publisher Summary This chapter describes the hydrogenation of nitriles, which is a complicated process, owing to the existence of reactive intermediates comprising several consecutive and competitive reactions of different characters. Some of them are typical hydrogenation reaction promoted by metallic hydrogenation catalysts; others are condensation reactions of acid-base character. The active centers for the hydrogenation and condensation reactions are localized on the surface of the metallic component of the catalyst, and the type of metal used is decisive for the catalyst properties. By changing the reaction conditions the relationships between the rates of hydrogenation and condensation can be influenced and thus the composition of the reaction product can be varied. The net result under the actual reaction conditions employed depends on the type of catalyst and/or on the experimental arrangement. The individual catalysts differ in their responses to a change in reaction conditions, and very often contradictory results are encountered. Addition of ammonia enhances the content of primary amines in hydrogenations catalyzed by nickel or cobalt, promotes the formation of secondary amines on copper catalysts under certain conditions and leads to an increased yield of tertiary amines in hydrogenations catalyzed by platinum or palladium.

Jiří Volf

Papers

Chapter 4 Hydrogenation of Nitriles

Adsorption of amines on alumina

The isosteric heat of adsorption on heterogeneous surfaces