Pyrolytic Conversion of Olive Mill Wastewater Sludge to Biofuels Using Red Mud as Catalyst

Abstract

Abstract:Olive mill wastewater sludge (OMWS) is an environmental pollutant in olive oil industry. The problem stems from the strong odor and poor biodegradability of OMWS because of its high phenolic compounds. In most Mediterranean countries, olive mill wastewater is stored in evaporation ponds and the residual sludge is landfilled for disposal. To address this environmental pollution problem, fluidized bed catalytic pyrolysis of OMWS was developed to produce pyrolysis liquids that are stable, low viscosity (5-7 cP), neutral pH (6-7), and high higher heating value (41 MJ/kg). The pyrolysis was conducted at 400-500°C in a red mud catalyst bed. The yields of the organic fraction were 29-35 mass%; char/coke yield was 20-29 mass%; and gas yield was 24-37 mass%. The 13 C NMR and GC/MS analyses of the liquid products showed predominance of aliphatic hydrocarbons and small fractions of aromatic hydrocarbons and ketones. The composition of these liquid products is in sharp contrast with most lignocellulosic biomass pyrolysis products which are normally rich in aromatic compounds and have very low aliphatic product content. In the absence of the red mud catalyst, the liquid product was viscous and contained acidic compounds.

Reformulated Red Mud: a Robust Catalyst for In Situ Catalytic Pyrolysis of Biomass

“…The XRD analyses of the raw red mud (fresh) and calcined FRM catalysts before and after pyrolysis show that the major changes occurred in each stage of the treatment. After calcination, the FRM lost some peaks that were attributed to gibbsite (Al(OH) 3 ) and goethite (FeO(OH)) due to dehydration of these components as reported by Agblevor et al 88 After pyrolysis, there were major changes in the structure of the catalyst due to the conversion of almost all the hematite component to magnetite (see Supporting Information, Figure S1). Even though biochar and coke were on the surface of the used catalyst, there was no significant difference in the XRD spectra of the regenerated and used catalysts.…”