Cellulose pyrolysis carbon dioxide yields

Studies on the pyrolysis of starch have attracted attention since 1913. In a historically first report, Bantlin determined the following yields of products from rice starch decomposed at temperatures raised within 7 h from 100 to 500° 12% of coke, 30% of water, 3% of tar, 5% of acetic acid, 6% of various aldehydes, 1.1% of ketones, 13% of carbon dioxide, 8% of carbon monoxide, and some hydrogen and ethylene. Sandomini was the first to study the influence of metal oxides (of Al, Cr, and Zn). He did not observe any appreciable effects of these additives on the decomposition at 270 to 300 of several organic compounds, among them starch and cellulose. 

A study of the cumulative yields of volatile products at various temperatures showed that, after pyrolysis for 18 hours at 156 and 188°, although water was the main product from the starches, carbon dioxide and carbon monoxide were also formed. Limited, pyrolytic degradation must, therefore, have occurred at these temperatures. There was a large increase in all three products at 218.6°, indicating that major decomposition occurs near this temperature. In contrast, cellulose did not form comparable quantities of carbon dioxide and carbon monoxide until temperatures of 260-270° were reached. 

The fast pyrolysis decomposition of cellulose starts at temperatures as low as 150°C. Pyrolysis of cellulose below 300°C results in the formation of carboxyl, carbonyl, and hydro peroxide groups, elimination of water and production of carbon monoxide and carbon dioxide as well as char residue (Evans and Milne, 1987). Therefore low pyrolysis temperatures will produce low yields of organic liquid yields. Fast pyrolysis of cellulose, above 300°C, results in liquid yields up to 80 wt.%. Cellulose initially decomposes to form activated cellulose (Bradbury et al., 1979). Activated cellulose has two parallel reaction pathways, depolymerization and fragmentation (ring scission). The main products from each reaction pathway are rather different as ring scission produces hydroxyacetaldehyde, linear carbonyls, linear alcohols, esters, and other related products (Bradbury et al., 1979 Zhu and Lu, 2010 Lin et al., 2009) and depolymerization produces monomeric anhydrosugars, furans, cyclopentanones, and pyrans and other related products (Bradbury et al., 1979 Zhu and Lu, 2010 Lin et al., 2009). Each reaction pathway is independent and is influenced by pyrolysis temperature and residence time (Bradbury et al., 1979). 

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