The untreated DMSO- and base-extracted xylans behaved quite similarly in a thermal 

 environment; however, the two types of xylan showed major differences when treated with 

 alkali. Thermal analysis and pyrolysis gas chromatography showed that xylan treated 

 at the 5 percent level of NaOH was quite similar to that which was untreated. Appar- 

 ently the glucuronic acid component of the xylan neutralized about 4/5 of the alkali 

 so the treatment was increased from 5 to 9 percent. The TGA of DMSO- and base-extracted 

 xylan treated with 9 percent NaOH is shown in figure 11. The DMSO -extracted xylan had 

 a higher residue and a slower rate of pyrolysis. This may be due to the greater 

 neutralizing effect of the base-extracted xylan because there are more glucuronic acid 

 units present per unit weight. 



Figure 12 shows the TGA and DTA of DMSO -extracted xylan treated with 9 percent 

 NaOH. The onset of rapid weight loss on TGA showed active pyrolysis to begin at 200° C. 

 The maximum rate of pyrolysis was 0.06 mg./°C. and the residue at 450° C. was 31 percent. 

 There was a net exotherm from 200° to 325° C. during rapid weight loss shown on DTA 

 (fig. 12) . The DTA of base-extracted xylan treated with 9 percent NaOH showed an endo- 

 therm at the onset of rapid weight loss and a subsequent exotherm from 225° to 325° C. 

 (fig. 13). The maximum weight loss rate was 0.07 mg./°C. and the residue at 450° C. 

 was 27 percent . 



Neat DMSO- and base- extracted xylan were pyrolyzed and the products swept directly 

 into the GLC. The major products were identified by the previously described methods 

 (table 6, fig. 14). As expected, much more 2-furaldehyde was produced from xylan as 

 compared to cellulose. The large amount of acetic acid from DMSO-extracted xylan was 

 quantitatively equal to the acetate groups, plus what was produced from the deacetylated 

 product. However, the DMSO-extracted xylan produced twice as much H2O, half as much 

 acetaldehyde and 2-furaldehyde, and some other differences that could not be readily 

 explained . 



The two types of xylan were treated with the additives so that the pyrolysis pro- 

 ducts could be identified, quantified, and compared to those of treated cellulose and 

 wood. Treatment of both xylans with 5 percent ZnCl2 had an effect similar to that 

 found for treated cellulose (fig. 14). There was an increase in furan compounds and a 

 decrease in 2 and 3 carbon carbonyl compounds (table 6). However, the acetaldehyde 

 produced from the ZnCl2 treated DMSO-extracted xylan was about twice that of the un- 

 treated DMSO-extracted xylan. The 2-furaldehyde was increased by 2.2 times for both 

 types of xylan treated with 5 percent ZnCl2, although there was still twice as much 

 2-furaldehyde produced from the base-extracted xylan. 



The effects of 9 percent treatment on both types of xylans also produced results 

 (table 6) generally similar to alkali-treated cellulose (fig. 15). The small carbonyl 

 compounds increased and the furan compound decreased. The compounds showing the 

 greatest increase were acetone, propionaldehyde , and crotonaldehyde . There was also 

 an increase in CO2 and H2O. 



20 



