57784-35-7Relevant articles and documents
Liquid-phase hydrogenation of citral over Pt/SiO2 catalysts - I. Temperature effects on activity and selectivity
Vannice,Singh
, p. 165 - 180 (2000)
Liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) over Pt/SiO2 catalysts was studied under kinetic conditions free of transport limitations and poisoning effects at 298-423 K and 7-21 atm. The rate of citral hydrogenation exhibited a minimum in activity between 298 and 423 K, and this was attributed to the relative activation energies for the decomposition of the unsaturated alcohol and desorption of CO. At low reaction temperatures (298 K), the rate of citral disappearance was low and CO was slowly accumulated under reaction conditions to block active sites and eventually led to a complete loss of activity. At 373 K, alcohol decomposition was more rapid, but the CO desorption rate was significantly enhanced and a pseudo-steady state was readily established which resulted in minimal additional inhibition and conventional Arrhenius behavior with an activation energy of 7 kcal/mole. The reaction kinetics for each hydrogenation reaction in the reaction network were modeled using a Langmuir-Hinshelwood model invoking dissociative adsorption of hydrogen, competitive adsorption between hydrogen and the reactive organic species, and the observed product distributions at each temperature were described very well. Furthermore, deactivation due to decomposition of the unsaturated alcohols geraniol and nerol, along with CO desorption at higher temperatures, was invoked to account for the unusual rate dependence on temperature.
Alkaline modifiers as performance boosters in citral hydrogenation over supported ionic liquid catalysts (SILCAs)
Salminen, Eero,Virtanen, Pasi,Kordás, Krisztián,Mikkola, Jyri-Pekka
, p. 126 - 131 (2013/01/15)
Supported ionic liquid catalysts (SILCAs) consist of nano-scale catalytic species immobilized in an ionic liquid layer which, in turn, is immobilized on a solid support. In this work, novel SILCAs containing various inorganic alkaline modifiers (e.g. potassium hydroxide) were prepared and applied in citral hydrogenation reactions. The supported ionic liquid catalyst systems demonstrated enhanced reaction rates and improved selectivities toward citronellal in citral hydrogenation. With the addition of an alkaline modifier into ionic liquid layer, the catalyst selectivity increased from 16% to 74%. In fact, a highly selective reaction route toward citronellal was accomplished.
Application of a cross-linked Pd-chitosan catalyst in liquid-phase- hydrogenation using molecular hydrogen
Schü?ler, Stefan,Blaubach, Nico,Stolle, Achim,Cravotto, Giancarlo,Ondruschka, Bernd
, p. 231 - 238 (2013/02/23)
Chitosan was cross-linked with hexamethylendiisocyanate and loaded with Pd which was subsequently reduced with NaBH4. The prepared catalyst was characterized by FT-IR and elemental analysis. The metal content was determined by ICP-MS measurements. Several substrates (cyclohex-2-enone, benzalacetophenone, 1,2-diphenylacetylene, and N-benzylidenaniline) were hydrogenated successfully in ethanol at mild conditions (50 °C, p(H 2) ～6 bar) utilizing a microwave reactor. Reaction parameters like temperature, hydrogen pressure, and the solvent were varied. It was shown that the reduction of the catalyst is crucial for catalytic activity. The catalyst was reused ten times for the hydrogenation of cyclohex-2-enone, without showing a dramatic loss in immobilized metal content. Also the polymeric support material did not show any decomposition.
