Catalytic pyrolysis of chicken manure over various catalysts

Abstract

In this study, non-catalytic and catalytic pyrolysis of chicken manure (CM) were investigated to understand the pyrolysis kinetics and product distribution of CM by thermogravimetric analysis (TGA) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). TGA and the apparent activation energy changes, calculated using the Ozawa method, indicated that the decomposition of CM was comprised of four reaction stages. The 1st decomposition of CM was likely the decomposition of carbohydrates and lipids, followed by the 2nd decomposition of lignin at high temperatures. The 3rd decomposition was likely involving the decomposition of proteins. At the final stage, metal carbonates in the ash of CM were likely decomposed. Py-GC/MS analysis indicated a decrease in oxygenates, such as furfural, phenol, and fatty acid, after applying acid catalysts. Among the various acid catalysts, HZSM-5(Silica/Alumina = 30), having the strongest acid sites, showed the highest efficiency for the production of aromatic hydrocarbons, followed by HBeta(Silica/Alumina = 25), HY(Silica/Alumina = 30), natural zeolite, spent fluid catalytic cracking catalyst (FCC), and bentonite. Although bentonite and spent FCC were ineffective, natural zeolite showed a catalytic effect on converting oxygenates to aromatic hydrocarbons. On the other hand, the content of a high molecular weight nitrile, hexadecanenitrile, was also increased. Commercial zeolites, HY(Silica/Alumina = 30), HBeta(Silica/Alumina = 25), and HZSM-5(Silica/Alumina = 30), led to higher aromatic formation efficiencies with less hexadecanenitrile formation than other catalysts. These efficiencies were increased significantly by varying the catalyst to CM ratio from 1/1 to 5/1, with a noticeable decrease in hexadecanenitrile.