Catalytic Pyrolysis of Pinewood for Improving Hydrocarbon Yield and Oil Stability Using Low-Cost Metal-Supported Catalysts

The objectives of this research are to develop low-cost metal-supported catalysts to improve the hydrocarbon yield in the bio-oil and to reduce the undesired compounds such as aldehydes, ketones, and acids. In this study, a fixed bed reactor was constructed using a stainless steel pipe, a split furnace, and an ice bath condenser for the catalytic pyrolysis of pine sawdust. A low-cost metal-supported catalyst has been developed and characterized using SEM, EDS, and BET analysis methods. In addition, the effects of temperature and catalyst type on the yield and quality of the pyrolysis bio-oil were investigated. The experiment was carried out at 400, 500, and 600°C at 1 atmosphere in the presence of 100 mL/min nitrogen without a catalyst, over HZSM-5 or Ni/HZSM-5. Prior to the pyrolysis, the pine sawdust was sized using a 1.18 mm sieve and dried for 24 hours at 105°C in an oven. The feedstock’s ultimate and proximate analyses were completed using a CHNS-O analyzer, a thermogravimetric analyzer, and a furnace. The output products collected were bio-oil, biochar, and syngas. The bio-oil was collected by condensation and analyzed using Gas Chromatography and Mass Spectrometry (GCMS). The non-catalytic pyrolysis had a high yield (37.44w.%) at 500°C; however, HZSM-5 and Ni/HZSM-5 had a similar amount of bio-oil (36.601 and 35.341 wt.%, respectively) at 400°C. The presence of catalysts has improved the bio-oil viscosity by producing more than 90% of light bio-oil and approximately ≤ 10% of heavy bio-oil. The qualitative analysis is categorized into two subgroups of compounds. The first subgroup was constituted of desired compounds such as hydrocarbons, alcohols, phenols, and derived phenol compounds. The other subgroup represents the undesired compounds such as aldehydes, ketones, and acids. The hydrocarbon content in the heavy bio-oil was relatively high, while alcohols, phenols and their derivatives constituted the major compounds in light bio-oils. The presence of Ni/HZSM-5 has increased the selectivity towards the desired compounds from 49.742% to 80.179% in heavy bio-oils and 34.945% to 56.270% in light bio-oils at 400°C