SYNOPSISThe kinetics of the isothermal batch macroemulsion and miniemulsion polymerizations of methy1 methacrylate (MMA) at 50°C have been studied. Hexadecane was used as the cosurfactant or swelling agent. The nucleation mechanisms were observed to be different between macroemulsions and miniemulsions. The effect of surfactant, cosurfactant, initiator, shear, and hold time on droplet nucleation was studied. The miniemulsion particles were found to contain more radicals on average than the macroemulsion particles using certain recipes. This resulted in higher polymerization rates for the miniemulsions at identical particle numbers. The latex-particle-size distributions were similar even though the miniemulsion droplets start out with a high polydispersity of around 1.5. Miniemulsion latexes were found to be more stable under shear. Conductance of emulsions during polymerization was found to be a valuable on-line tool for investigatingparticle nucleation and growth.

The hydroformylation of propene to give predominantly iso-butanal has been achieved; class-leading selectivity is possible even at higher temperatures that deliver fast rates. Racemic Rh complexes of bidentate phospholane phosphites derived from tropos-biphenols and unusual solvent systems are the key to the selectivity observed.

No abstract

A study on how ligand backbone structure has an impact on selectivity, rate, and catalyst stability of hydroformylation catalysts was prompted by some longer-term stability issues being discovered for a phospholane-phosphite with a [−CH 2 O−] backbone. A series of phospholane-phosphite ligands were synthesized. Catalysts made in situ from these ligands and [Rh(acac)(CO) 2 ] were found to give iso-butanal selectivities up to 75% at temperatures between 75 and 105 °C: the latter being a benchmark for iso-selectivity in reactions conducted at industrially meaningful temperatures. A racemic rhodium complex of a bidentate phospholane-phosphite from a tropos-biphenol with an extended backbone showed unusually high stability at high temperatures, combined with even better iso-selectivity in propene hydroformylation relative to the original complex. A related ligand with an electron-withdrawing group maintained the unusually high stability and improved activity. Characterization of the precatalysts of type [RhH(CO) 2 (L)] was accomplished using in situ HPIR spectroscopy and backed up by density functional theory calculations (B3PW91-D3 level) and by NMR studies; the latter showed that the variation of the backbone also had a pronounced impact on the precatalyst structure. A key finding is that it is now possible to prepare phospholane-phosphite ligands that deliver high iso-butanal selectivity and that show no signs of degradation after several days even above typical reaction temperatures. In one stability test, several kilograms of aldehydes were produced with TOF and selectivity being consistent over several days.

The hydroformylation of propene to give predominantly iso-butanal has been achieved;class-leading selectivity is possible even at higher temperatures that deliver fast conversion. Racemic rhodium complexes of bidentate phospholane phosphites derived from tropos-biphenols and unusual solvent systems are the key to the selectivity observed.