Chapters authored
Kinetic Study of the Partial Hydrogenation of 1-Heptyne over Ni and Pd Supported on Alumina
Part of the book: Hydrogenation
Alkyne Selective Hydrogenation with Mono- and Bimetallic- Anchored Catalysts
Partial hydrogenation of alkynes has industrial and academic relevance on a large scale; industries such as petrochemical, pharmacological and agrochemical use these compounds as raw material. Finding an economic, active and selective catalyst for the production of alkenes through partial hydrogenation of alkynes is thus an important challenge. Mono- and bimetallic catalysts (palladium, ruthenium and nickel) were synthetized by the incipient wetness technique using gamma alumina and an activated carbon as supports. The catalysts were characterized by inductively coupled plasma, hydrogen chemisorption, temperature-programmed reduction and X-ray photoelectronic spectroscopy (XPS). The objective of this work is to study 1-heptyne-selective hydrogenation using supported catalysts influenced by different factors: (a) pretreatment reduction temperature, (b) reaction temperature, (c) type of support, (d) metal loading, (e) precursor salt and (f) addition of a second metal to monometallic palladium catalyst. The Lindlar commercial catalyst, commonly used in these types of reactions, was used for comparative purposes. XPS technique allowed verifying that the presence of electron-deficient species on the catalyst surface with high metal loading affects the conversion and selectivity to the desired product. Nevertheless, the influence of geometrical effects and/or mixed active sites in the catalysts, as well as metal-metal and metal-support interactions, cannot be neglected.
Part of the book: New Advances in Hydrogenation Processes
New Strategies for Obtaining Inorganic-Organic Composite Catalysts for Selective Hydrogenation
Pd/composites are catalysts in which the catalytically active metal phase is located in a small layer on the support surface. The metal distribution obtained on these supports corresponds to a structure commonly known as “egg-shell”. This distribution is optimal for reactions that have heat or mass transfer resistances. The small thickness of the metal layer is mainly attributed to the use of support pellets of mixed organic–inorganic composition, the special interaction between the hydrophobic–hydrophillic support surface and the metal species (Pd or Pt) present in the impregnating aqueous solution. Pd/composite catalysts are active and selective for the reactions of selective hydroge-nation of styrene, 1-heptyne, 3-hexyne and 2,3-butanone, and enantioselective hydrogenation of ethyl pyruvate. These reactions are of interest in both academic and industrial aspects.
Part of the book: New Advances in Hydrogenation Processes