Gayan Nawaratna

Effect of hydrocarbon tail-groups of transition metal alkoxide based amphiphilic catalysts on transesterification

In liquid/liquid/solid (L/L/S) systems pertinent to two immiscible reactant liquids mixed with a solid catalyst, the reaction efficacy depends on the mass transfer limitations at the L/L/S phase boundary. Formation of an emulsion in such a system will likely reduce the mass transfer barrier significantly. The stability of such an emulsion system depends on the hydrophilicity of the head group of the catalytic emulsifier toward the more polar liquid reactant and the hydrophobicity of the tail group toward the more nonpolar liquid reactant. This study looks at the effect of the alkyl groups with varying carbon numbers in titanium alkoxide as a catalyst that also has emulsification (amphiphilic) properties to transesterify triglycerides in alcohols. All forms of oligomeric titanium alkoxides tested were highly basic. Those with smaller alkoxide groups (lower carbon numbers) tended to be more basic than those with higher carbon numbers. The chirality did not affect the degree of basicity of the alkoxides. The maximum ester yield noticed was 64.25% (with 63.85% selectivity towards transesterification) with titanium methoxide after 3 hours of reaction. It was observed that higher the number of carbon atoms in the tail group the lower the catalytic ability of the amphiphile towards transesterification. It is expected that longer the carbon-chain in the tail group stronger the emulsification ability of the amphiphile in oil-in-alcohol systems. However, when looking at the efficacy of the amphiphile for the combined emulsification and catalytic ability, it is apparent that the length of the alkoxide group needs to be compromised.

Reforming glycerol under electro-statically charged surface conditions

Catalysis is dependent on electronic interactions that occur between substrate molecules and surface atoms of a catalyst. Although these electronic interactions have been altered by means of adding dopants, the effect of direct extraneous alteration of electronic structure of catalyst-substrate system has not yet been studied. Here, we studied the effects of electrically charging a conductive catalyst surface (Ni–Ce/carbon) and a substrate system (glycerol nanodroplets) on the efficacy of steam reforming. The behavior of the system when the catalysts surface was excited with electrons while the substrates were positively charged was studied at varying temperatures and polarity. It was evident that throughout the temperature ranges tested, the hydrogen yields increased consistently when the system was charged as opposed to reforming under neutral conditions. Reforming under electrically charged surface conditions resulted in a 25% increase in hydrogen selectivity, and 64% increase in substrate conversion. The effects were more pronounced at temperatures below the glycerol boiling point. These results expose the possibility of controlling the outcome of a reaction by extraneous manipulation of the electronic structure of a catalyst/substrate surface.

Effect of Hydrocarbon Tail-group of Alkoxide Catalysts in Transesterification

In liquid/liquid/solid (L/L/S) systems pertinent to two immiscible reactant liquids mixed with a solid catalyst, the reaction efficacy depends on the mass transfer limitations at the L/L/S phase boundary. Formation of an emulsion in such a system will likely reduce the mass transfer barrier significantly. The stability of such an emulsion system depends on the hydrophilicity of the head group of the catalytic emulsifier toward the more polar liquid reactant and the hydrophobicity of the tail group toward the more nonpolar liquid reactant. This study looked at the effect of the alkyl groups with varying carbon numbers in titanium alkoxide as a catalyst that also has emulsification (amphiphilic) properties to transesterify triglycerides in alcohols. It was observed that higher the number of carbon atoms in the tail group, the lower the catalytic ability of the amphiphile towards transesterification. It is expected that longer the carbon-chain in the tail group, stronger the emulsification ability of the amphiphile in oil-in-alcohol systems. However, when looking at the efficacy of the amphiphile for the combined emulsification and catalytic ability, it is apparent that the length of the alkoxide group needs to be compromised.