Pyrolysis and oxidation of cellulose in a continuous-feed and -flow reactor: Effects of NaCl

A dual-zone, continuous-feed tubular reactor is used to assess the potential for formation of products from the incomplete combustion in thermal oxidation of cellulose. Solid cellulose powder is fed continuously into a volatilization oven, where it fragments and vaporizes under steady-state conditions. The gas-phase polymer fragments flow directly into a second, constant temperature, main flow reactor and undergo further pyrolysis and oxidation. Temperatures in the main flow reactor are varied independently to observe conversion, intermediates, and final products. Combustion products are monitored at main reactor temperatures from 400 to 750 °C at a 2.0-s residence time and fuel equivalence ratios (φ) of 0.25 and 0.8 with four on-line GC/ FID instruments. Polymer reaction products and intermediates are further identified by GC/ MS; 41 species are positively identified in the pyrolysis and oxidation of cellulose, and an additional 59 species are tentatively identified. Increasing reactor temperature at constant fragment reaction time shifts the molecular weight distribution toward lower mass and increases the extent of conversion. Complete conversion (i.e., mineralization) of identified cellulose fragments to CO₂ and H₂O is observed at 2.0-s reaction time and 750 °C under these fuel-lean conditions. The major volatilization products at 400 °C are carbonyl compounds, hydrocarbons, furans; pyrans, and anhydrosugars. Cellulose in the presence of NaCl (5% Cl) shows higher decomposition of levoglucosan and more rapid conversion of heavier initial products to CO₂. The formation of most initial products, i.e., C6 oxygenated species, hydrocarbons (C₅-C₇), light species (C₁-C₄), and CO, is slightly inhibited by NaCl at both φ ≈ 0.25 and φ ≈ 0.8. The formation of C₆ oxygenated species, hydrocarbons (C₅-C₇), and furan derivatives (C₄-C₅) increases at the higher fuel equivalence ratio of φ ≈ 0.8.