The selective hydrogenation of crotonaldehyde has been investigated over a monometallic Pt/SiO2 catalyst and platinum bimetallic catalysts where the second metal was either silver, copper, or tin. The effects of addition of a second metal to the Pt/SiO2 system on the selectivity to crotyl alcohol were investigated. The Pt-Sn bimetallic catalysts were characterized by hydrogen chemisorption, 1H NMR and microcalorimetry. The Pt-Ag/SiO2 and Pt-Cu/SiO2 catalysts were characterized by hydrogen chemisorption. Pt-Sn/SiO2 catalysts selectively hydrogenated crotonaldehyde to crotyl alcohol and the method of preparation of these catalysts affected the selectivity. The most selective Pt-Sn/SiO2 catalysts for the hydrogenation of crotonaldehyde to crotyl alcohol were those in which the Sn precursor was dissolved in a HCl solution. Sn increased both the rate of formation of butyraldehyde and the rate of formation of crotyl alcohol. The Pt/SiO2, Pt-Ag/SiO2 and Pt-Cu/SiO2 catalysts produced only butyraldehyde. Initial heats of adsorption ((approximately)90 kJ/mol) measured using microcalorimetry were not affected by the presence of Sn on Pt. We can conclude that there is no through metal electronic interaction between Pt and Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn had similar initial heats of adsorption coupled with the invariance of the 1H NMR Knight shift.

The selective hydrogenation of crotonaldehyde to form either crotyl alcohol or n-butyraldehyde was studied using Density Function Theory (DFT). Previous work had demonstrated the promise of a palladium-zinc bimetallic catalyst, in both a monomer and trimer form, in favorably hydrogenating the carbon-oxygen double bond. The study was completed through analyzing the calculated energies of the molecular systems and using their relative values to determine favorable arrangements. The results indicate a strong preference for the adsorption of the carbon-carbon double bond over the carbon-oxygen double bond on both the palladium-zinc monomer and trimer surfaces. Further analysis demonstrated that neither surface catalyst would promote the complete reaction of crotonaldehyde to n-butyraldehyde. Both systems resulted in unsurpassable activation barriers leading the catalyst to be inactive for the hydrogenation of crotonaldehyde.

In this thesis we studied the kinetics of crotonaldehyde hydrogenation on a series of Pt-cerium oxide and Pt-titanium dioxide catalysts to elucidate some mechanistic aspects of partial hydrogenation processes, which occurs on bi-functional catalyst systems. Studies in the literature have shown that the C=O bond hydrogenation of unsaturated aldehydes, more specifically of the crotonaldehyde species, only occurs when a platinum/metal-oxide interface exist, and does not occur on pure platinum or metal oxide surfaces. The mechanism of this process and the determination of the active site of crotonaldehyde have never been investigated. Because the presence of Pt/metal-oxide interfaces lead to this selective C=O bond hydrogenation, the active site is hypothesized to occur on the platinum/metal-oxide interface. However, possibilities of the active site being at the platinum sites or scaling with the metal-oxide sites remains. In this study we show that the active site occurs on the platinum within some distance from the interface of the two phases. We also show in this study that within a region of cerium oxide nanocubes which are uniformly packed on a platinum surface there exist no C=O bond activity, however at the interface between rafts of cerium oxide nanoparticles there exhibits significant enhancements to the C=O bond product. These results provide strong evidence that the chemistry for this C=O bond pathway extends beyond the three phase boundary of the platinum/metal-oxide alone. The results from this study provide insight into fundamental design parameters for designing highly selective bi-functional nanocatalysts.

This work delineates the effect of different reaction variables on the outcome of heterogeneously catalyzed reactions, and explains how to optimize the product yield of specific compounds. Metal catalysis, simple and complex oxides, zeolites and clays are discussed, both as catalysts and as potential supports for catalytically active metals.

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.