Silicon carbide equipments for process intensification of silicon reactions.

Bluestar Silicones, one of the worldwide leaders in silicones chemistry, proposes a R&D project, aiming to design new equipment for the transposition of batch to continuous processes. The safety and environmental issues linked to this type of chemicals, and the productivity targets as well require innovative technologies characterized by a fair corrosion resistance and high heat and mass transfer performances. A preliminary prototype of heat exchanger reactor made of silicon carbide plates has been developed by the LGC in collaboration with a SME specialist of SiC, Boostec. It has allowed the pilot feasibility with some reactions of industrial interest for a Bluestar Silicones to be highlighted. Now, it is necessary to pursue this effort and beyond the feasibility step to go on up to the design of an industrial reactor. This project corresponds to a programme of innovative process development in order to design cleaner, safer and less consuming devices

Total catalytic oxidation of a side-product for an autothermal restoring hydrogen process

International audienceThe catalytic total oxidation of toluene is used to bring the required calories to restore hydrogen from methylcyclohexane (MCH). Two coupled reactions, both catalyzed by Pt/alumina, are thus considered in one autothermal heat-exchanger reactor (HER): endothermic dehydrogenation of methylcyclohexane and catalytic combustion of less than 10% of produced toluene (6% for the chemical reaction, about 4% for heat losses). Both reactions are carried out at 350 °C. Methylcyclohexane and toluene light-off curves have been performed in one elementary module. Methylcyclohexane combustion has been eliminated due to its safety drawbacks, although the MCH combustion provides best stability to autothermal HER

Atomistic modelling of entropy driven phase transitions between different crystal modifications in polymers: the case of poly(3-alkylthiophenes)

Polymorphism and related solid-state phase transitions affect the structure and morphology and hence the properties of materials, but they are not-so-well understood. Atomistic computational methods can provide molecular-level insights, but they have rarely proven successful for transitions between polymorphic forms of crystalline polymers. In this work, we report atomistic molecular dynamics (MD) simulations of poly(3-alkylthiophenes) (P3ATs), widely used organic semiconductors to explore the experimentally observed, entropy-driven transition from form II to more common form I type polymorphs, or, more precisely, to form I mesophases. The transition is followed continuously, also considering X-ray diffraction evidence, for poly(3-hexylthiophene) (P3HT) and poly(3-butylthiophene) (P3BT), evidencing three main steps: (i) loss of side chain interdigitation, (ii) partial disruption of the original stacking order and (iii) reorganization of polymer chains into new, tighter, main-chain stacks and new layers with characteristic form I periodicities, substantially larger than those in the original form II. The described approach, likely applicable to other important transitions in polymers, provides previously inaccessible insight into the structural organization and disorder features of form I structures of P3ATs, not only in their development from form II structures but also from melts or solutions

MELT TEMPERATURE EFFECTS ON THE POLYMORPHIC BEHAVIOR OF MELT-CRYSTALLIZED POLYPIVALOLACTONE

Experimental evidence is discussed indicating that in the case of polypivalolactone (PPVL), the time spent in the melt, and the melt temperature from which the samples are quenched to the crystallization temperature, both affect the subsequent crystallization process, and specifically the relative proportions of the α- and γ-modifications. Neither thermal degradation nor heterogeneous nucleation by extraneous substances appear to account fully for the observed phenomena. The results suggest that the surprising features of the polymorphic behaviour of PPVL, as reported, may relate to the persistence of structural organization, the most likely being nuclei of different crystalline forms, at a temperature which is more than 40°C above the phenomenological melting point, i.e. at temperatures comparable to the proposed equilibrium melting temperature of α-PPVL