(675c) Purification of Lignocellulosic Hydrolyzates by Nonionic Polymer Flocculation and Scale up Studies

Lignocellulosic hydrolyzates produced by hydrothermal treatment of wood chips contain hemicellulose sugars, acetic acid and significant quantities of colloidal material. These particles are mostly composed of lignin and its derivatives, which have a wide range of particle size distribution. Separation of these colloidal materials is necessary to improve fermentability of sugars into biofuels and other bioproducts. Flocculation of wood hydrolyzates prior to microfiltration improves their filterability. In this paper we investigated the separation of sugar maple wood extracts at bench and pilot scales ( of 1000 kg) by a non-ionic polymer Polyethylene Oxide (PEO) with two different molecular weights (100 and 1000 kDa).

The rate of flocculation was monitored by sedimentation of the suspensions. The optimal dosage of PEO depended on the temperature and extract concentrations and varied between 20 to 50 ppm.  Although the pH of the extracts was varied from 2 through 10,  the effect on suspension stability was minimal. The optimal temperature for flocculation at optimal polymer dosage was 21.5ºC. The composition of hemicelluloses in the supernatants after flocculation were not altered from the raw extract showing that flocculation does not remove significant amount of fermentable sugars. Hence such pretreatment clarification is not likely to affect downstream bioproduct yields.

Flocculation and clarification with PEO were demonstrated on large pilot scale batches of 1000 kg of extracts. Further the flocculated extract was filtered and the filtrate showed a 99.5% reduction in turbidity, from 12000 NTUs in the raw extract to 50 NTUs in the filtrate.