The limited availability of fossil resourses mandates the development of new energy
vectors, which is one of the Grand Challenges of the 21st Century . Biocatalytic
energy conversion is a promising solution to meet the increased energy demand of
industrialized societies. Applications of biocatalysis in the gas-phase are so far limited
to production of fine chemicals and pharmaceuticals. However, this technology
has the potential for large scale biocatalytic applications , e.g. for the formation of
novel energy carriers. The so-called solid/gas biocatalysis is defined as the application
of a biocatalyst immobilized on solid-phase support acting on gaseous substrates .
This process combines the advantages of bio-catalysis (green chemistry, mild reaction
conditions, high specicity & selectivity) and heterogeneous dynamic gas-phase
processes (low diffusion limitation, high conversion, simple scale-up).
This work presents the modifications of a PID Microactivity Reference reactor in
order to make it suitable for solid/gas biocatalysis. The reactor design requirements
are based on previously published laboratory scale solid/gas systems with a feed
of saturated vapors . These vapors are produced in saturation
flasks, which were
designed and optimized during this project. Other modifications included relocation
of the gas mixing chamber, redesigning the location and heating mechanism for the
reactor tube, and heating of the outlet gas line.
The modified reactor system was verified based on the Candida antarctica lipase
B catalyzed transesterication of ethyl acetate with 1-hexanol to hexyl acetate and
ethanol and results were compared to liquid-phase model reactions. Products were
analyzed on line by a gas chromatograph with a
flame ionization detector. C. antarc-
tica physisorbed on silica particles produced a 50% conversion of hexanol at 40 C in
the gas-phase. A commercial immobilized lipase from Iris Biotech produced 99% and
97% conversions of hexanol in similar experiments.
This project achieved its goal to design, establish and successfully verify a solid/-
gas biocatalysis reactor. Future work will target optimization of the reactor's operating
conditions and the development of whole cell catalysts for energy production
reactions. Potential experiments include the study of hydrogenolytic carbon dioxide
reduction to methanol by free enzymes or methanogenic organisms , and the
investigation of hydrogen production by water splitting of algae or cyanobacteria.
|Date of Award||May 2012|
- Physical Science and Engineering
|Supervisor||Jorg Eppinger (Supervisor)|
- Solid gas