A two-dimensional pyrolysis process to concentrate nicotine during tobacco leaf bio-oil production

Pyrolysis is a simple, inexpensive and arguably safer method to recover high-value products from plants relative to solvent extraction processes. In order to optimize pyrolysis conditions to improve the separation of selected compounds, a novel reactor-condenser chain process was developed to isolate nicotine from tobacco leaf. Ground tobacco (Nicotiana tabacum) leaf (<1 mm) was pyrolyzed at 10 °C/min from ambient to 275 °C using a two-dimensional (2-D) mechanically fluidized reactor (MFR). The gases formed in the reactor would either condense in the hot (180, 190, 200 or 240 °C) or the cold (4 °C) condenser based on the boiling point of the chemicals in the vapors produced. The 2-D MFR operating conditions were optimized by a two-step process: (1) vapors were generated between ambient to 275 °C and the hot condenser temperature was varied to determine which yielded the highest nicotine concentration and recovery; and (2) the hot condenser temperature was kept constant while the best reactor temperature cut was determined. Nicotine recovery was optimal with a condenser temperature of 190 °C. A 25% nicotine concentration in the bio-oil was obtained with a nicotine recovery of 92% as the reactor temperature was increased from ambient to 275 °C. Narrowing the reactor temperature range between 260 and 275 °C maximized the nicotine concentration, as the bio-oil had a 56% nicotine concentration, with a nicotine recovery of 21%. The 2-D pyrolysis process represents a significant improvement over solvent extraction and is potentially applicable for valuable chemical recovery from biomass.