Guayule (Parthenium argentatum) pyrolysis biorefining: Production of hydrocarbon compatible bio-oils from guayule bagasse via tail-gas reactive pyrolysis

Abstract Guayule ( Parthenium argentatum ) is a woody desert shrub cultivated in the southwestern United States as a source of natural rubber, organic resins, and high energy biofuel feedstock from crop residues. We used guayule bagasse, the residual biomass after latex extraction as feedstock in a pyrolysis process that employs a reactive gas environment to formulate a special intermediate bio-oil product that allows use of conventional hydrotreating with conventional noble metal catalysts and a simple distillation process to synthesize hydrocarbon (drop-in) fuels. The said guayule-bagasse tail gas reactive pyrolysis (TGRP) process comprises pyrolyzing the guayule bagasse in a fluidized-bed reactor in the presence of a reactive and flammable tail gas (comprising CO ∼ 30%, CH 4  ∼ 16%, CO 2  ∼ 40%, H 2  ∼ 10%, C 2 H 4  ∼ traces) generated in the pyrolysis process and without the use of catalyst to produce bio-oil with C/O molar ratio of 14/1 in organic yields of 34–40 wt% having an energy content of 31–37.5 MJ/kg. When we further processed the said bio-oil by centrifugation, we obtained 85 wt% yield and further 50–65 wt% yields following a continuous hydrotreatment over common noble metals (Pt, Ru or Pd) on a carbon support. Distillation of this mixture yielded >95 wt% hydrocarbon liquid fuel mixture comprising 30.4% gasoline (C 5 –C 7 ), 37% jet (C 8 –C 12 ) and 24% diesel (C 13 –C 22 ). Analysis of a composite mixture of the hydrotreated product from the bagasse showed the majority of the sample (66%) was C 12 and below, which falls within the gasoline (naphtha) range with the greatest fraction of naphtha falling within the C 8 –C 10 range. Beyond C 12 , the molecular weights increased through the diesel range (34%), with C 37 being the highest observable molecular weight. The product met several ASTM standards for drop-in fuels, but the sulfur content (primarily due to latex extraction additives) was relatively high at around 300 ppm, indicating that hydrodesulfurization may be required to be infrastructure ready.