Petru Filip

Sunflower and rapeseed oil transesterification to biodiesel over different nanocrystalline MgO catalysts

The catalytic activity for the production of biodiesel with three morphologically different nanocrystalline MgO materials prepared using simple, green and reproducible methods was investigated. The nanocrystalline samples studied were MgO(111) nanosheets (MgO (I)), conventionally prepared MgO (MgO (II)) and aerogel prepared MgO (MgO (III)). The methods to produce the catalysts included: (a) 4-methoxy-benzyl alcohol templated sol-gel process followed by supercritical drying and calcination in air at 773 K (MgO (I)), (b) from a commercial MgO that was boiled in water, followed by drying at 393 K, and dehydration under vacuum at 773 K (MgO (II)), and (c) viahydrolysis of Mg(OCH3)2 in a methanol–toluene mixture, followed by supercritical solvent removal with the formation of a Mg(OH)2 aerogel that was dehydrated under vacuum at 773 K (MgO (III)). These catalysts were characterized by TEM, DRIFT, and DR-UV-Vis and tested in the transesterification of sunflower and rapeseed vegetable oils at low temperatures, under different experimental conditions: autoclave, microwave and ultrasound. Working with these materials under microwave conditions provided higher conversions and selectivities to methylesters compared to autoclave or ultrasound conditions. Under ultrasound, a leaching of the magnesium has been evidenced as a direct consequence of a saponification reaction. These systems also allow working with much lower ratios of methanol to vegetable oil than reported in the literature for other heterogeneous systems. The activation temperature providing the most active catalysts was found to vary depending on the exposed facet: for MgO(111) structures (i.e.MgO (I)) this was 773 K, while for MgO (110) and (100) (i.e.MgO (II) and MgO (III)) this was 583 K.

Ultrasound Assisted Metathesis of Monocyclic Olefins with Tungsten-Based Catalysts

The paper describes the effect of ultrasonic irradiation (power ultrasound 50-100 kHz) on synthesis of tungsten-based metathesis catalysts consisting of WC16 and Me4Sn and on the catalyst activity and selectivity in ring-opening metathesis polymerization of cyclooctene and cyclododecene with this catalytic system. An ultrasonic acceleration was observed in the formation of the initiating metallacarbene active species from the catalyst components and in the main polymerization steps, such as initiation and propagation but also in accompanying back-biting reactions, leading overall to polymers and oligomers.

Activation of Cycloolefin Metathesis by Ultrasonic Irradiation

The present research focuses on the impact of power ultrasound on the synthesis of the tungsten-based metathesis catalytic system WCl6/Me4Sn and its activity in ring-opening metathesis polymerization of cyclooctene and cyclododecene. As compared to corresponding silent ROMP reactions with this mild catalytic system, altered reaction kinetics and different product selectivity have been found. Rate acceleration and an enhancement of oligomer formation have been clearly evidenced. The demonstrated possibility of employing technical grade solvents in ROMP induced by WCl6/Me4Sn is a further gain of the ultrasound strategy. Under the right conditions, ultrasound may thus promote greener, more cost effective and sustainable metathetic procedures.

Could the calixarenes be a viable solution for radioactive decontamination of mine waters from Romania

The present paper shall briefly overview the past of the Romanian uranium industry and its current state. Then it will present the features of the radioactive contaminated mine waters and the treatment methods used for their decontamination. The advantages and the disadvantages of the decontamination method will be pointed out. The main updates concerning the calixarenic derivatives behavior towards uranium will be presented.