Biological Mineral Range Effects on Biomass Conversion to Aromatic Hydrocarbons via Catalytic Fast Pyrolysis over HZSM-5

Abstract

A set of 20 biomass samples, comprising 10 genotypes of switchgrass, sorghum, and miscanthus grown in two different soils with high and low poultry manure input conditions and having a wide biological range of mineral content, were subjected to catalytic fast pyrolysis (CFP) over HZMS-5 using pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). The resulting products, including benzene, toluene, ethylbenzene, and xylenes (BTEX), naphthalenes, and gases, including carbon oxides, methane, and olefins, were quantified in terms of product carbon yield and chemical selectivity. The effects of the total ash content as well as the individual mineral components were compared to evaluate the effect of the natural range of these components on the product distribution. While there was considerable variation in the data because of the biological influence, a positive correlation was found between ash content and carbon conversion to aromatic hydrocarbons, which was particularly strong when considering only the switchgrass samples. This large degree of variation may be characteristic only of this sample set. Among individual mineral elements in the biomass, potassium, an essential mineral for plant growth, was found to have a strong negative influence on the carbon conversion to aromatic hydrocarbons, but iron was found to have a positive influence on the conversion to aromatics. Correlations between mineral content, the chemical intermediates from the incipient pyrolysis process, and the final CFP products suggest that the main influence of potassium is on the initial pyrolysis reactions, while iron may affect the catalytic reactions over HZSM-5.