A summary of the thermal characteristics of cottonwood and its components are 

 presented in table 2. These data indicate that the thermograms of cottonwood reflect 

 the thermal behavior of its major components and the information that is obtained on 

 these chemicals could be extrapolated to the original material with confidence. These 

 data also show that under the experimental conditions (uncatalyzed reactions) lignin 

 is the major source of char, but the carbohydrates are the precursor of the volatile 

 products (tar and gases) . 



Table 2. --The pyrolysis characteristics of cottonwood components 



Component : 



Temperature 

 of initiation 

 di) 



: Maximum : 

 : rate of pyro : 

 : (R) ' : 



Residue 

 at 450° C 





°C. 



mg./°C. 



Percent 



Wood 



175 



C 1 ) 



19 



Cellulose 



320 



.25 



6 



Xylan (DMSO) 



215 



.11 



6 



Milled wood lignin 



175 



.03 



45 



Acid lignin 



200 



.02 



60 



■'■Wood exhibits two definite rates, 

 the other during cellulose pyrolysis. 



one during xylan pyrolysis, 



The most significant point about these data is the importance it places upon the 

 pyrolysis of hemicellulose. Beall 7 touched on this when he concluded, "The hemicellu- 

 loses appear to be the most important component in determining the rates of degradation 

 of both softwoods and hardwoods." In addition to this we can see that xylan pyrolyzes 

 almost completely prior to the beginning of pyrolysis of cellulose. Cellulose has been 

 studied quite extensively in terms of ignition and other phenomena. It is quite clear 

 that the hemicelluloses are of at least equal importance and may even provide the 

 initial volatiles for ignition and combustion. 



PYROLYSIS OF COTTONWOOD CELLULOSE 



In this part of the current study the pyrolysis products from cellulose and the 

 changes due to treatment with ZnCl 2 and NaOH were qualitatively and quantitatively 

 determined under identical conditions in order to: (1) determine the effects of an 

 acidic and an alkali additive on the composition of the volatile products and the 

 pyrolytic reactions; (2) gain basic information about the mechanisms of the reactions 

 involved by comparing these data with similar data from levoglucosan ; and (3) extend 

 the information that has been obtained from wood in which cellulose^ forms the major 

 chemical component. Levoglucosan, 1 , 6-anhydro- g-D-glucopyranose , is currently being 

 studied as a model compound for the secondary pyrolysis reactions of cellulose. 



Treatment of cellulose consisted of adding 5 percent by weight of anhydrous zinc 

 chloride or sodium hydroxide to a powdered sample. A small quantity of tetrahydrofuran 

 was added to help evenly distribute the treatment. The treated material was then dried 

 and stored under vacuum. The treatment procedure for both DMSO and base xylan was 

 similar except it was found that about four-fifths of the sodium hydroxide was neutral- 

 ized, probably by the glucuronic acid component. Therefore, 9 percent sodium hydroxide 

 was used for alkali treatment of xylan. 



F. C. Beall. Thermal degradation analysis of wood and wood components. 1968. 

 (Unpublished Ph.D. Thesis on file at Syracuse Univ., N.Y.) 



8 



