Ultrasound- and microwave-assisted preparation of lead-free palladium catalysts: effects on the kinetics of diphenylacetylene semi-hydrogenation

The effect of environmentally benign enabling technologies such as ultrasound and microwaves on the preparation of the lead-free Pd catalyst has been studied. A one-pot method of the catalyst preparation using ultrasound-assisted dispersion of palladium acetate in the presence of the surfactant/capping agent and boehmite support produced the catalyst containing Pd nanoparticles and reduced the number of pores larger than 4 nm in the boehmite support. This catalyst demonstrated higher activity and selectivity. The comparison of kinetic parameters for diphenylacetylene hydrogenation showed that the catalyst obtained by using the one-pot method was seven times as active as a commercial Lindlar catalyst and selectivity towards Z-stilbene was high. Our work also illustrated that highly selective Pd/boehmite catalysts can be prepared through ultrasound-assisted dispersion and microwave-assisted reduction in water under hydrogen pressure without any surfactant

Scale-up of an RF heated micro trickle bed reactor to a kg/day production scale

The scale-up of a radiofrequency (RF) heated micro trickle bed reactor for hydrogenation of 2-methyl-3-butyne-2-ol (MBY) over a Pd/TiO2 catalyst has been performed. The axial and radial temperature profiles were calculated using a 2D convection and conduction heat transfer model. The effect of the reactor length, tube diameter and number of parallel tubes on the temperature non-uniformity parameter has been studied. The axial scale-up was achieved by repeating a single periodic unit consisting of one heating and one catalytic zone along the reactor length. The catalyst loading can be increased by an order of magnitude following this approach. A radial temperature difference of 2 K was developed in a reactor with an inner diameter of 15 mm. The scale-up by numbering up allows the accommodation of seven parallel tubes inside a single RF coil. It creates a 7 K difference in the average temperature between the central and the outer tubes which results in a 5% difference in MBY conversion. An overall scale-up factor of near 700 is achieved which corresponds to a production rate of 0.5 kg of product/day

Greener Method to Obtain a Key Intermediate of Vitamin E over Cu-ZSM-5

The catalytic oxidation of 2,3,5-trimethylphenol was performed over transition metals modified ZSM-5 zeolites employing hydrogen peroxide as oxidant under mild reaction conditions. Catalysts samples were characterized by several techniques (XRD, FTIR, BET, AA) and cristallinity and orthorhombic symmetry were confirmed for all of them. Best catalytic results were obtained for Cu-ZSM-5 sample, so further activity studies were done over this material. 2,3,5-trimethyl-1,4-benzoquinone was obtained as the main product of the selective oxidation. Reaction parameters (nature of the solvent, hydrogen peroxide concentration, reaction time, catalyst mass, substrate initial concentration and reaction temperature) were evaluated to reach the optimum reaction conditions. According to the obtained results, an apparent activation energy of 52.33 kJ/mol was calculated.Fil: Saux, Clara. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Renzini, Maria Soledad. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Gómez, Silvina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Pierella, Liliana Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; Argentin

Catalyst Repurposing Sequential Catalysis by Harnessing Regenerated Prolinamide Organocatalysts as Transfer Hydrogenation Ligands

A catalyst repurposing strategy based on a sequential aldol addition and transfer hydrogenation giving access to enantiomerically enriched α-hydroxy-γ-butyrolactones is described. The combination of a stereoselective, organocatalytic step, followed by an efficient catalytic aldehyde reduction induces an ensuing lactonization to provide enantioenriched butyrolactones from readily available starting materials. By capitalizing from the capacity of prolineamides to act as both an organocatalyst and a transfer hydrogenation ligand, catalyst repurposing allowed the development of an operationally simple, economic, and efficient sequential catalysis approach

Biotin – The Chiral Challenge

In this contribution, the first examples of the catalytic highly enantioselective reduction of cyclic meso-anhydrides to lactones and of thioanhydrides to thiolactones are described. The N-benzyl protected key building blocks in the industrial synthesis of (+)-biotin were so far only accessible by usage of expensive reagents in multi-step procedures. In contrast, homogeneous catalytic enantioselective hydrogenation of the corresponding meso-anhydride mediated by a metal phosphane complex proceeds with high optical induction (ee >95%) and excellent yield. The catalytic system provides a generally applicable new method for the preparation of lactones from cyclic anhydrides

Upgrading Bio-Based Acetone to Diacetone Alcohol by Aldol Reaction Using Amberlyst A26-OH as Catalyst

The aldol reaction of bio acetone in presence of a strongly basic ion exchange resin was carried out with and without the addition of water in a temperature range between − 30 °C and 45 °C. The conversion, selectivity and service time of the ion exchange resins were investigated in a stirred batch reactor and a continuous fixed bed reactor. For the batch experiments, both conversion and selectivity increased with decreasing temperature. Furthermore, the addition of water to the reaction medium has a positive effect on selectivity and catalyst service time of the resins. For the continuous flow experiments carried out in a fixed bed reactor, the selectivity towards diacetone alcohol is higher than in a batch reactor. This high selectivity is favored by a short contact time which inhibits as expected most of the consecutive reactions