Pyrolysis of cellulose nitrate, sulfate, and phosphate

However, besides these compounds, several other compounds indicated in Table 7.3.1 were identified in the pyrolysate at 750° C [42]. 

Cellulose sulfate has significantly fewer applications than the nitrate. The pyrolysis of cellulose treated with sulfuric acid and containing residual sulfate groups was previously discussed (see Section 7.2). The pyrolysate of this material has a chemical composition similar to that of cellulose pyrolysate. However, the existence of residual sulfate groups favors the reaction  

This reaction is supposed to have an E2 mechanism [32]. Further decomposition of the dehydrated cellulose results in an increased yield of water, char, gases and carbonyl compounds and a simultaneous decrease in levoglucosan formation as compared to pure cellulose pyrolysis. 

Among the esters with organic acids, cellulose acetate is the most important one. Cellulose acetate has numerous uses such as manufacture of yarn, photographic films, lacquers, etc. Cellulose can be acetylated starting with lower levels of esterification up to the formation of cellulose triacetate. The acetate is obtained from the reaction of cellulose with acetic anhydride, usually in the presence of a catalyst such as H2SO4 or HCIO4. Numerous industrial procedures are known for this process [43]. 

Pyrolysis of cellulose acetate has been applied for analytical purposes of the fibers [44], structural elucidation [45], study of thermal stability [46], etc. The main pyrolysis product of cellulose acetate is acetic acid. Several compounds typical in cellulose pyrolysis such as 5-hydroxymethyl-2-furancarboxaldehyde can be seen as its ester with acetic acid. Also, some compounds tentatively identified as dihydroxydioxanes and dihydroxydioxolanes in cellulose pyrolysate are found as acetic acid esters in the pyrolysate of cellulose acetate. Depending on the degree of substitution (D.S.), for D.S 3, free -OH groups are still present in cellulose. This allows the formation of compounds typical for cellulose pyrolysate in addition to the compounds resulting from 

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