Catalytic microwave pyrolysis of orange peel: Effects of acid and base catalysts mixture on products distribution

In the present study, bio-oil has been produced from microwave-assisted catalytic pyrolysis of orange peel (OP). The effects of microwave power or heating temperature (MWP) and ZSM-5, potassium hydroxide (KOH) and mixing of ZSM-5-KOH as a catalyst at different ratios have been examined. Both MWP and the catalyst improved the heating and increased the maximum temperatures of pyrolysis process. Maximum bio-oil yield for non catalytic pyrolysis was (25.7 wt%) and with ZSM-5-KOH mixture catalyst (39.6 wt%) was obtained at 600 W respectively. The higher gas yield might be attributed to that catalytic pyrolysis did the secondary cracking of pyrolytic volatiles and promoted the larger small molecules. The chemical components and functional groups present in the pyrolytic bio-oils are identified by GC-MS, FT-IR, H-1 NMR and elemental analysis techniques. Phenol observed very less percentage with higher acidic and nitrogen compounds in the case of non-catalytic pyrolysis bio-oil, whereas catalytic pyrolysis bio-oil showed a higher percentage of phenol. The aromatic protons 26% (region from 6.0 to 8.5 ppm) was found higher amount for ZSm-5 catalytic bio-oil, which is due to the higher aromatics phenolic monomer compounds. The higher amount of oxygen present in raw biomass reduced significantly when used catalyst due to the oxygen reacts with carbon and produce (CO and CO2) and water.