Microwave-assisted pyrolysis of waste cooking oil for hydrocarbon bio-oil over metal oxides and HZSM-5 catalysts

Qiuhao Wu, Yunpu Wang, Yujie Peng, Linyao Ke, Qi Yang, Lin Jiang, Leilei Dai, Yuhuan Liu, Roger Ruan, Donghua Xia, Li Jiang

Research output: Contribution to journalArticlepeer-review

Abstract

Microwave-assisted pyrolysis of waste cooking oil is an environmentally friendly and economical method for obtaining benzene, toluene, ethylbenzene, and xylene (BTEX) which are important industrial chemicals. This study provides new routes to produce of BTEX and the utilization of waste cooking oil. The effect of catalytic temperatures (350 °C, 400 °C, 450 °C, 500 °C, and 550 °C), types of metal oxide (CoO, NiO, ZrO2, SrO, CeO2, and CaO), catalytic modes (ex-situ mixed catalysis, ex-situ separate catalysis, and in-situ separate catalysis), and ratio of HZSM-5 to metal oxide (HZSM-5 only, 4:1, 2:1, 1:1, 1:2, and CaO only) were studied. Results showed high catalytic temperature promoted the formation of monocyclic aromatic hydrocarbons at the cost of a decrease in bio-oil yield. But the concentration of BTEXS (benzene, toluene, ethylbenzene, xylene, and styrene) only increased from 256.58 mg/ml to 259.55 mg/ml with a temperature increase from 500 °C to 550 °C. Alkaline earth metal oxides (CaO, SrO) showed a significant deoxygenation capability during co-catalysis with HZSM-5. However, when CaO was applied under ex-situ mixed catalysis, the concentration of polycyclic aromatic hydrocarbons was up to 35.47%, which was much higher than 9.18% under HZSM-5 only. Also, the concentration of BTEXS decreased from 256.58 mg/ml (HZSM-5 only) to 167.54 mg/ml (HZSM-5 mixed with CaO). Further investigation of catalytic mode showed that ex-situ separate catalysis was more suitable for co-catalysis of alkaline earth metal oxides and HZSM-5. The concentration of BTEXS were both significantly higher than that of HZSM-5 only, which increased by 121.81 mg/ml for CaO and 108.52 mg/ml for SrO under ex-situ separate catalysis. Further study showed that the highest concentration of BTEXS was 702.20 mg/ml obtained when the ratio of HZSM-5 to CaO was 2:1. It was almost 2.8 times higher than HZSM-5 alone and 42.2 times higher than non-catalytic results.

Original languageEnglish (US)
Article number113124
JournalEnergy Conversion and Management
Volume220
DOIs
StatePublished - Sep 15 2020

Keywords

  • Bio-oil
  • HZSM-5
  • Metal oxide
  • Microwave-assisted catalytic pyrolysis
  • Quantitative analysis
  • Waste cooking oil

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