Bio-oil production from low-rank coal via novel catalytic microwave pyrolysis using activated carbon + Fe₂(SO₄)₃ and HZSM-5 + Fe₂(SO₄)₃

The need for clean-coal technology is still demanding to counter environmental issues. Global coal is dominated by low-rank coal (LRC). Microwave pyrolysis (MP) is an advanced technologies to convert LRC into clean energy such as bio-oil. However, the main pyrolysis challenges are low heating efficiency and the products dominated by heavy-tars. This study focused on MP to treat LRC using AC + Fe₂(SO₄)₃ and HZSM-5 + Fe₂(SO₄)₃ as catalysts and receptor. Effects on product distribution and process conditions (time, temperature, and power) were evaluated. Results showed that AC + Fe₂(SO₄)₃ and HZSM-5 + Fe₂(SO₄)₃ increased the rate of temperature rise and final temperature of MP, causing changes in product distribution. As compared to non-microwave or conventional catalytic pyrolysis (CP) at the same condition (620℃ and 60 min), bio-oil produced from MP + 1.0%AC + 24.6%Fe₂(SO₄)₃ was 47.1%, 13.2% higher than the CP. Meanwhile, using MP + 1.0%HZSM-5 + 24.6%Fe₂(SO₄)₃, 42.5% bio-oil was produced by an increase of 8.6%. Using 1.0%AC + 24.6%Fe₂(SO₄)₃, the maximum bio-oil production was observed at 120 min, 620℃, and 450 W, generating 49.2% bio-oil. Meanwhile, using 1.0%HZSM-5 + 24.6%Fe₂(SO₄)₃, the maximum bio-oil production was observed at 105 min, 620℃, and 525 W, generating 42.2% bio-oil. The outcomes of the studies could be a basis for future clean fuel production utilizing LRC that could reduce global carbon emission.