Different nanostructured supports, based on 1-decyl-2-methyimidazolium cations covalently attached to a polystyrene divinylbenzene porous matrix, were used as carriers to immobilise Candida antarctica lipase B. The suitability of these immobilised lipase derivatives for the synthesis of biodiesel (methyl oleate) by the methanolysis of triolein has been tested in both tert-butanol and supercritical (sc)CO(2) (18 MPa, 45 °C) as reaction media. The use of modified supports with low ionic-liquid loading covalently attached to the main polymeric backbone chains provide structured materials that led to the best biodiesel yields (up to 95 %) and operational stability (85 % biodiesel yield after 45 cycles of 8-4 h) in scCO(2) (45 °C, 18 MPa). The presence of tert-butanol as an inert cosolvent in the scCO(2) phase at the same concentration as triolein was key to avoid poisoning the biocatalyst through the blockage of its active sites by the polar byproduct (glycerol) produced in the biodiesel synthesis.
Lipase B from Candida antarctica (CALB) is able to catalyze C-C bond formation. After immobilization onto a hydrophobic PS-DVB support, the activity increases when compared to that of the soluble or tanthe commercially available Novozyme 435 (being up to 6 fold more active). Our results show that although this activity is not related to the catalytic group, the promiscuous activity of CALB may be tuned via immobilization. In addition, we have show that the secondary structure of both immobilized enzymes is quite different, using FT-ATR-IR spectroscopy.
The controlled radical polymerization of monomeric units containing chiral ionic liquids (CILs) allows the synthesis of intrinsically chiral polymers through a bottom-up design. These polymeric chiral ionic liquids (PCILs) show a well-defined three dimensional structure organized as the result of a complex noncovalent network of hydrogen-bonding contacts driven by the C2 hydrogen atoms of the imidazolium aromatic rings and the OH moieties present in the side functionalities of the main polymeric chain. The exchange of the chloride counter ion by the L-prolinate anion leads to new types of polymeric catalysts, which behave as efficient artificial aldolase biomimetic systems, being highly active and selective for the aldol reaction in water. These new polymeric catalysts are significantly more active than the corresponding monomeric counterpart when the reaction is performed either in water or in the presence of water. The increase in catalytic efficiency can be related to their 3D structure, displaying helical chirality in the polymeric chain as a function of their preparation methodology. Under suitable experimental conditions, these polymers are able to catalyse the consecutive aldol-dehydration process, behaving as synthetic mimics of the aldolase-dehydrogenase enzymatic system. Moderate enantioselectivities can be achieved under suitable conditions.
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The catalytic activity of Rose Bengal (RB) immobilized on supported ionic liquid (IL)‐like phases was evaluated as a polymer‐supported photocatalyst. In these systems, the polymer was designed to play a pivotal role. The polymeric backbone adequately modified with IL‐like moieties (supported IL‐like phases, SILLPs) was not just an inert support for the dye but controlled the accessibility of reagents/substrates to the active sites and provided specific microenvironments for the reaction. The structure of SILLPs could be finetuned to adjust the catalytic efficiency of the RB‐SILLP composites, achieving systems that were more active and stable than the related systems in the absence of IL‐like units.
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