Catalyst Separation (catalyst + separation)

Distribution by Scientific Domains


Selected Abstracts


Novel Palladium-Catalysed Hydroamination of Myrcene and Catalyst Separation by Thermomorphic Solvent Systems

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Arno Behr
Abstract Hydroamination is an elegant and atom economical reaction to convert alkenes into amines. One of the few technical realisations of this reaction is the hydroamination of myrcene to diethylgeranylamine, an important precursor of (,)-menthol. However, this so-called "Takasago process" is catalysed by high amounts of alkali metals, especially lithium, which makes it a relatively expensive approach. In the present work, the hydroamination of myrcene with morpholine is catalysed by palladium complexes with bidentate ligands such as bis(diphenylphosphino)butane (DPPB) or bis(2-diphenylphosphinophenyl) ether (DPEphos). The systematic optimisation of the reaction parameters under single-phase conditions led to yields of the 1,4-adducts of higher than 90%. The only side products proved to be the telomers of myrcene, whose formation could be decreased by using appropriate reaction conditions. The method of temperature-dependent solvent systems was successfully applied to separate the palladium catalyst from the amines with a palladium leaching lower than 1.0%. [source]


Highly Active and Recyclable Heterogeneous Iridium Pincer Catalysts for Transfer Dehydrogenation of Alkanes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Zheng Huang
Abstract Pincer-ligated iridium complexes have proven to be highly effective catalysts for the dehydrogenation and transfer-dehydrogenation of alkanes. Immobilization onto a solid support offers significant potential advantages in the application of such catalysts particularly with respect to catalyst separation and recycling. We describe three approaches toward such immobilization: (i) covalent attachment to a Merrifield resin, (ii) covalent bonding to silica via a pendant alkoxysilane group, and (iii) adsorption on ,-alumina (,-Al2O3), through basic functional groups on the para- position of the pincer ligand. The simplest of these approaches, adsorption on ,-Al2O3, is also found to be the most effective, yielding catalysts that are robust, recyclable, and comparable to or even more active than the corresponding species in solution. Spectroscopic evidence (NMR, IR) and studies of catalytic activity support the hypothesis that binding occurs at the para- substituent and that this has only a relatively subtle and indirect influence on catalytic behavior. [source]


Multiphase Systems for the Recycling of Alkoxycarbonylation Catalysts

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006
Jeroen J., M. de Pater
Abstract This review evaluates the various multiphasic systems that have been developed for catalyst recycling in the context of alkoxycarbonylation of alkenes and alkynes. Immobilization of the catalyst on an insoluble support, such as silica, alumina, clay or a polymer, as well as immobilization in the inorganic phase of several liquid/liquid biphasic systems (aqueous/organic, ionic liquid/organic, fluorous/organic or supercritical CO2/organic) has been described. In several cases detailed information on the efficiency of catalyst separation and recycling is available. Most of the work was focused on the alkoxycarbonylation reactions of alkenes, for which several efficient methods for catalyst recycling were demonstrated. The recycling of catalyst through specific precipitation from supercritical CO2 or selective dissolution in a fluorous phase, has received only scant attention but offers many opportunities for further improvement. [source]


Optical and physicochemical properties of silica-supported TiO2 photocatalysts

AICHE JOURNAL, Issue 8 2006
Javier Marugán
Abstract Commercial applications of photocatalysis in slurry reactors employing titanium dioxide particles present the disadvantage of the additional cost associated with the downstream catalyst separation. In past years a significant effort has been made to develop supported titania photocatalysts on particles of larger size in order to facilitate the sedimentation recovery process. In this work, two different silica materials have been used for preparing immobilized catalysts. Their physicochemical characteristics have been compared with those corresponding to two commercially available unsupported titanium dioxide catalysts. However, for reaction kinetics and reactor design purposes, three additional properties must be known: (i) the spectral specific radiation absorption coefficient, (ii) the spectral specific radiation scattering coefficient, and (iii) the asymmetry factor of a model for the angular distribution of the scattered photons (the phase function). They have been determined with specially designed spectrophotometer transmission, diffuse transmittance, and diffuse reflectance experiments and constitute the most significant addition to this contribution. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]


Environmentally Benign Production of Biodiesel Using Heterogeneous Catalysts

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 2 2009
Michikazu Hara, Prof.
Abstract Fuelling the future: The production of esters of higher fatty acids from plant materials is of great interest for the manufacture of biodiesel. Heterogeneous catalysts can provide new routes for the environmentally benign production of biodiesel. Particulate heterogeneous catalysts can be readily separated from products following reaction allowing the catalyst to be reused, generating less waste, and consuming less energy. Diesel engines are simple and powerful, and exhibit many advantages in energy efficiency and cost. Therefore, the production of higher fatty acid esters from plant materials has become of interest in recent years for the manufacture of biodiesel, a clean-burning alternative fuel. The industrial production of biodiesel mostly proceeds in the presence of "soluble" catalysts such as alkali hydroxides and liquid acids. A considerable amount of energy is required for the purification of products and catalyst separation, and furthermore these catalysts are not reusable. This process results in substantial energy wastage and the production of large amounts of chemical waste. Particulate heterogeneous catalysts can be readily separated from products following reaction, allowing the catalyst to be reused and consuming less energy. This Minireview describes the environmentally benign production of biodiesel using heterogeneous catalysts such as solid bases, acid catalysts, and immobilized enzymes. [source]