(603e) Microfiltration of Lignocellulosic Hydrolyzates Using Dead End Filtration to Separate Lignin and Other Inhibitors

Microfiltration
of lignocellulosic hydrolyzates using dead end filtration to separate lignin
and other inhibitors

B. Bhayani,
B.V. Ramarao

Department of paper & Bioprocess
engineering, SUNY ESF

In
the production of biofuels from lignocellulosics, the
biomass is first extracted using dilute mineral acids or hot water. This hemicellulose rich oligomers are hydrolyzed under
treatments at higher temperature and pressure to yield sugar monomers which are
fermented into biofuels such as ethanol, biobutanol or bioplastics.  The initial treatment with either dilute
acids or hot water also allows some of the lignin to pass in particulate,
colloidal or dissolved forms into the sugar solution. Lignin and other phenolic
compounds derived from it are strongly inhibitory to microbial fermentation
processes. They also adhere to polymeric membranes, carbohydrates and other
surfaces, fouling separation membranes. Their removal from the liquor stream
not only facilitates downstream separations but improves the fermentation
profiles of the resulting sugar hydrolyzates. Therefore, methods to separate
lignin from liquors and hydrolyzates form valuable additional operations in the
biorefineries.

A
new approach has been developed which can separate inhibitory components from the
extracts based on the fact that reduction of temperature of the biomass
hydrolyzates can result in the native agglomeration and separation of lignin
containing solids by simple settling and/or filtration which thus can result in
large increases in separation efficiencies for
hydrolyzates. By filtering the extracts at lower temperature (10ºC) it is
possible to obtain higher flux rate than at higher temperatures (20ºC).  As
shown in Figure 1 and Figure 2, the cumulative flow for extracts at 10ºC is
higher than the extracts at 20ºC at two different pressures. The turbidity of
permeate for any given combination of pressure and temperature was less than 10
NTU. It has been hypothesized that the natural flocculation tendency of
extracts increases with decreasing temperature.

In addition to the temperature, the effect
of addition of a flocculent (Polyethylene oxide, PEO) has been
investigated. Substantial enhancement in filtrate flux upon addition of 20 ppm of PEO as seen in Figure 3 is observed.