Simone Albertazzi

Deactivation of a Pt/γ-Al2O3 catalyst in the partial oxidation of methane to synthesis gas

The deactivation of a Pt/-Al2O3 catalyst used in an industrial plant for the partial oxidation of methane to synthesis gas was investigated. Four samples at different time-on-stream in air were characterized and their catalytic performances were tested in a micro-reactor in order to shed light on the causes and the effects of this deactivation. The high temperatures (about 900 ◦ C) reached while operating in the industrial plant, promoted modifications to the -Al2O3, inducing sintering phenomena and, therefore, deactivation effects. The not used sample showed good values of yield in syngas (compared with equilibrium values), but these performances decreased quickly with time-on-stream.

Catalytic Properties of Hydrotalcite-Type Anionic Clays

This chapter discusses catalytic properties of hydrotalcite-type anionic clays. Layered double hydroxides (LDHs) [or hydrotalcite-type (HT) anionic clays] are natural or synthetic mixed hydroxides with interlayer spaces containing exchangeable anions, relatively simple and cheap to synthesize on both laboratory and industrial scales. LDHs can be considered promising materials for a large number of possible applications because of their high versatility, low cost, easily manipulated properties, wide range of composition and/or preparation variables, which make it possible to produce tailor-made materials to fulfil specific requirements. Mg/A1 mixed oxides offer the possibility of replacing liquid bases, which pose severe environmental problems, with environmentally friendly solid catalysts that can be easily separated and recycled. Hydrogenation is one of the most useful, versatile, and environmentally suitable reaction routes for many organic syntheses (fine chemicals, intermediates, petrochemical industry, etc.) and for the treating of petrochemical feeds.

Role of the Organic Feed and the Support Acidity in Hydrotreating Reactions on Pd–Pt on MCM-41 Catalysts

The reactivity of different organic compounds (naphthalene, alkylnaphthalenes, decalins, tetralin and their mixtures) and the roles of the support acidity and of the noble metals were studied in Pd/Pt on MCM-41 (with different Si/Al ratios) catalysts. The catalytic tests showed that the hydrogenolysis/ring-opening reactions mainly occurred on saturated compounds, while cracking took places mainly on unsaturated compounds. The presence of alkyl side chains on the polyaromatic ring inhibited the hydrodearomatization activity, proportionally to their length and number. Mixtures of naphthalene and methylnaphthalenes gave rise to a competition between the substrates, with a decrease in both hydrogenation and hydrogenolysis/ring-opening activities. Increasing support acidity favoured hydrogenolysis/ring-opening and cracking reactions, smoothing the hydrogenation activity. Noble metals are shown to be necessary not only in hydrogenation, but also in hydrogenolysis/ring-opening reactions.

New catalysts for the syngas production obtained by hydrotalcite type precursor containing silicate

Publisher Summary Ni and/or Rh based catalysts (ex-HT) derived by hydrotalcite precursor are considered to be effective catalysts in the catalytic partial oxidation (CPO) reaction. This chapter discusses new stable ex-HT catalysts prepared by inserting silicate instead of CO 3 2- anions in the interlayer. The amount of silicates is not limited by the charge balance of the cations, because, an excess of silicates leads to the formation of polysilicate anions. The insertion of silicates affects the structure of the calcined samples, because, unlike CO 3 2- , the silicates remain in the structure and contribute to the formation of the final catalysts. Catalysts with innovative structure are obtained by HT precursor prepared using silicate as interlayer anion. The calcined catalysts showed two phases—a mixed oxide type structure and a new M-silicate structure, where the cations of the active metal are partially soluted. The Rh catalyst prepared by HT silicate was more active and selective than the one prepared by CO 3 2- .