Catalytic co-pyrolysis of industrial hemp stalk and glycerol with HZSM-5 and dolomite: product yields and bio-oil characteristics

This study examined the catalytic fast co-pyrolysis of hemp stalk and glycerol using HZSM-5 and dolomite catalysts to produce diesel-range hydrocarbons. The co-pyrolysis method was used to produce aromatic and aliphatic hydrocarbons (C9-C20) in the diesel fuel range and a high amount of organic phase bio-oil. A bubbling fluidized bed reactor was used for this purpose. The yields and contents of derived bio-oils at different mixing ratios with glycerol (10, 15, and 20 wt.%), different catalysts (HZSM-5 and dolomite), and pyrolysis temperatures (350, 400, 450, 500, and 550 degrees C) were investigated. The co-pyrolysis results showed that the bio-oil yield improved with glycerol. The highest bio-oil yield (46.82%wt.) was achieved through in situ catalytic co-pyrolysis with glycerol (15%wt.) and dolomite at 550 degrees C. In addition, in situ catalytic co-pyrolysis with glycerol and dolomite caused a decrease of 48.84% (GC-MS peak area) in oxygenated compounds compared to direct pyrolysis of hemp stalk. The content of catalytic co-pyrolysis bio-oil mainly consisted of aliphatic hydrocarbons in the C12-C20 carbon range, and it also contains a significant amount of ketones, phenols, and alcoholic compounds. In addition, co-pyrolysis with the use of dolomite in the reactor, mostly methyl elaidate, methyl palmitate, 9-octadecene, and (E)- and 8-heptadecene structures were found in the bio-oil. Moreover, the findings presented in this paper can lead to the development of basic, cheap, and sustainable new methods for integrating pyrolysis oil into existing refinery infrastructure.