Spectroscopic characterization of extractives isolated with MTBE from straws.

Application: Mills can use this rapid separation procedure to control pitch problems by removing wood or straw extractives before pulping.

The accumulation of extractives in pulping and papermaking can cause troubles in mills. In alkaline conditions, such as in kraft pulping, the triglycerides are completely saponified, and the free fatty acids and resin acids are dissolved, but sterols and some steryl esters and waxes do not form soluble soap and tend to deposit and cause pitch problems. In neutral and acidic conditions, such as in mechanical pulping, the extractives are difficult to remove, and resinous woods are more of a problem in pitch control.

To identify the extractives that may lead to pitch problems, we analyzed the lipophilic extractives from rye and rice straws. In this continuing study, we examined the two extractives by FTIR, [.sup.1]H and [.sup.13]C NMR spectroscopies, and thermal analysis. Free fatty acids, sterols, waxes, steryl esters, and triglycerides were identified as the major five classes of lipids in the two straw extractives.

The rye straw extract exhibited a much stronger C=C cis stretching band at 1640 c[m.sup.-1] than did the rice straw extract. This finding indicated that the rye straw extractives contained more unsaturated

lipophilic compounds than the rice straw extractives contained. A rather weak band at 1030 c[m.sup.-1] indicated that the two extracts were relatively free of polysaccharides. The thermal analysis showed that the melting temperatures of the extractives occurred between 44.3[degrees]C and 50.0[degrees]C.

Conventional approaches to reducing deposition of wood extractives, such as the debarking or seasoning of logs, are often not sufficient to eliminate pitch problems. Researchers in mills can use the simple separation procedure described to remove wood or straw extractives to control pitch problems.

Xiao-Feng Sun is a postgraduate student at the Centre for Straw and Wood Utilization, The North-Western University of Agricultural and Forest Sciences and Technology, Yangling, The People's Republic of China. Run-Cang Sun is a professor at State Key Laboratory of Pulp & Paper Engineering, South China University of Technology, Guangzhou, People's Republic of China (current address: The Bio-Composites Centre, University of Wales, Bangor, Gwynedd LL57 2UW, UK. Email Run-Cang Sun at [e-mail].