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International audienceThe efficiency of organometal- (Ti, Zr, Sn, Hf, and Bi) and metal oxide- (Ge and Sb) based catalysts was investigated during the transesterification step of the synthesis of poly(butylene succinate) (PBS). PBS was prepared from succinic acid and 1,4-butanediol via a two-stage melt polycondensation process. The catalytic efficiency of the organometal catalysts was as follows: Ti≫Zr∼ Sn>Hf>Sb>Bi. The germanium and antimony metal oxides displayed desirable catalytic efficiency when were associated with hydroxy acids (lactic acid or glycolic acid), which acted as chelating agents. However, this catalytic system exhibited lower efficiency compared to the titanium system. Furthermore, at high concentrations of hydroxy acids the overall transesterification rate decreased. This effect can be explained by the substitution of PBS hydroxyl end groups by a lactic or glycolic unit, both of which are less reactive during the transesterification reaction. The role of catalytic residues during the storage and processing of PBS was also studied. The reduced viscosity of the PBS samples did not vary when processing at 190 °C from 1 to 10 minutes. However, when stored under ambient conditions, all PBS samples were prone to significant hydrolytic degradation, especially those containing a titanium catalyst. This behavior indicates that zirconium- and germanium-based catalysts could be interesting substitutes for titanium-based catalysts

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Minh, Doan Pham Besson, Michele Pinel, Catherine Fuertes, Patrick Petitjean, CaroleThe effect of addition of Re to activated carbon-supported Ru and Pd catalysts in the hydrogenation of 15 wt% succinic acid aqueous solutions to 1,4-butanediol (BDO) was examined. The yield and selectivity were in the range 62-66% at 160 A degrees C and 150 bar over the Re promoted catalysts. Bio-succinic acid from a fermentation process could be efficiently hydrogenated on 4 wt%Re-2 wt%Pd/C without significant loss of selectivity

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SSDI 0 1 6 5 -0 5 1 3 ( 9 6 ) 0 0 0 0 6 -3 Abstract.Glucose and gluconate aqueous solutions (2 mol/l) were oxidized with air (atmospheric pressure, 333K, pH 7) on active charcoal-supported, platinum catalysts (catalytic ratios substrate/Pt 2 787); some catalysts were promoted with bismuth or gold. The activity of unpromoted Pt/C catalysts for glucose oxidation was comparable with that of Pd-Bi/C catalysts and there was no deactivation; gluconate formed transiently was oxidized into glucarate, the final selectivity did not exceed 50%. The oxidation of gluconate on very well dispersed Pt catalysts prepared by cationic exchange or anionic adsorption leads to higher glucarate selectivities than those previously reported, in spite of the fact that the present solutions were much more concentrated and reduced amounts of platinum were used. Addition of bismuth adatoms by surface redox reaction produces a shift in selectivity towards 2-ketogluconate. Addition of gold adatoms on platinum decreases the catalyst deactivation.

Ring-opening polymerization (ROP) of glycolide was studied in melt conditions and in the presence of two different initiators: 1-dodecanol and 1,4-butanediol and tin(II) 2-ethylhexanoate as catalyst. Its subsequent polymerization provided poly (glycolic acid) with controlled molar masses ranging from 2000 to 42,000 g/mol with well-defined structures characterized by NMR. Their thermal properties were evaluated by DSC analysis, and a glass transition temperature at infinite molar mass (T g1 ) of 44.8 C was thus calculated. From rheological data, the critical molar mass for entanglement, M c , was estimated to be near 11,000 g/mol. Furthermore, in situ polymerizations were also performed between the plates of the rheometer within a same temperature range from 210 to 235 C. The variation of the storage and loss moduli during the polymerization step have been monitored by time sweep oscillatory experiments under an angular frequency x ¼ 10 rad/s. Finally, the development of an inverse rheological method allowed to calculate the bulk polymerization kinetics in the temperature range 200-230 C.