Studying Effects of Inorganic Salts On Biomass Pyrolysis Using a Captive Sample Reactor

Pyrolysis and gasification are two promising thermochemical technologies for the conversion of biomass to bio-oil and synthesis gas (syngas) respectively. Understanding biomass pyrolysis behavior is important for designing economical pyrolysis and gasification systems. Inorganic compounds present in biomass have been shown to cause selective formation of pyrolysis products, including catalytic degradation of biomass. In this study, 300 mm poplar sections were soaked in 0.1 M inorganic salt solutions and dried in a vacuum oven overnight at 60 ^oC. Poplar sections were impregnated in 100 mM solutions of various inorganic salts (NaCl, KCl, CaCl₂, NaOH, KOH, Ca(OH)₂, CuCl₂, FeCl₃, Cu(SO₄)₂ and Fe(SO₄)₃. The dried samples were then pyrolyzed in a captive sample reactor (CSR) at 450 ^oC and the poplar samples, both before and after pyrolysis, were analyzed by multiple microscopy modalities. Samples soaked in CuCl₂, FeCl₃, and Fe(SO₄)₃ displayed intriguing morphological and cell wall structural changes before pyrolysis whereas those soaked in alkali and alkaline earth metal salts retained the same morphology as untreated poplar. The morphological changes of post-pyrolysis chars from poplar samples treated with transition metal salts resemble changes observed for non-treated samples at significantly higher temperatures (>900 C). The pyrolysis products produced from these samples using CSR/molecular beam mass spectrometry (MBMS) system will be discussed.