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Institute
Control of porosity and composition of carbon based catalysts prepared by template assisted routes
(2015)
The potential of industrial porous concrete for using as a template for the synthesis of porous carbon materials has been investigated. Carbon replicas of porous concrete have been prepared by carbonization of sucrose. The pores of the resulting carbon materials range from the macropore to the micropore region, pointing to a hierarchy.
Hierarchically structured, porous carbon materials (PCM) were synthesized by sucrose infiltration into template material and subsequent carbonization. Three porous carbon materials were prepared using porous concrete (PCM-01) or silica gel (PCM-02 and 03) as template. Carbon particles from 125 to 200 μm were generated. Surface carboxylic group density was determined with 1.1 mmol/g dry material for each variant. Firstly, tailor-made PCM was evaluated as suitable support for lipase immobilization. Recombinant produced lipase of Thermomyces lanuginosus (TLL) was used as model enzyme. Two independent crude immobilization strategies were applied. Residual activities of up to 8.6 U/g and 31 U/g dry material for adsorptive and covalent immobilization (linkage via EDC) were achieved, respectively. Additionally, TLL was immobilized on commercially available polymethacrylate support showing similar residual lipase activities. Secondly, covalent immobilization was optimized to generate reproducible, highly stable and active immobilizates. Optimized covalent immobilizates showed residual activities of up to 10 U∙g⁻¹ dry carbon material using p-nitrophenyl-palmitate assay and protein loads of up to 45 mg g⁻¹dry carbon material. Covalent bound TLL-PCM showed storage stability for 12 months, remaining 100% of the initial activity. Operational stability resulted in stable and 100% active immobilizates over five consecutive cycles of use. Experiments showed that tailor-made porous carbon material is a promising support for lipase immobilization, which is adaptable in shape and dimension.