Abstract
We report a sustainable strategy to cleanly address biomass waste with high-value utilization. Phenol-rich bio-oil is selectively produced by direct pyrolysis of biomass waste corn straw (CS) without use of any catalyst in a microwave device. The effects of temperature and power on the yield and composition of pyrolysis products are investigated in detail. Under microwave irradiation, a very fast pyrolysis rate and bio-oil yield as high as 46.7 wt.% were obtained, which were competitive with most of the previous results. GC-MS analysis showed that temperature and power (heating rate) had great influences on the yield of bio-oil and the selectivity of phenolic compounds. The optimal selectivity of phenols in bio-oil was 49.4 area% by adjusting the operating parameters. Besides, we have made detailed statistics on the change trend of some components and different phenols in bio-oil and given the law and reason of their change with temperature and power. The in situ formed highly active biochar from CS with high content of potassium (1.34 wt.%) is responsible for the improvement of phenol-rich oils. This study offers a sustainable way to fully utilize biomass waste and promote the achievement of carbon neutrality.
Highlights
In China, corn straw (CS) is the most abundant biomass waste, and its annual output has exceeded 216 million tons (Li et al, 2016a)
Albeit the previous works have made great progress, the following challenges are still faced: 1) extra catalyst is associated with the cost and the environmental issue in the synthesis; 2) the selectivity of phenols and yield of bio-oil failed to increase at the same time; and 3) the catalytic effect of biochar produced by microwave pyrolysis and alkali metal from biomass is often ignored
We report the selective and green synthesis of phenol-rich bio-oils from CS waste by rapid pyrolysis without extra catalyst
Summary
In China, corn straw (CS) is the most abundant biomass waste, and its annual output has exceeded 216 million tons (Li et al, 2016a). Idris et al (Idris et al, 2021) reported that the total phenolic compounds were 73.6 area% at low pyrolysis temperature (300°C) using activated carbon as a catalyst, but the yield of bio-oil was only 30.0 wt.%. By adjusting the proportion of catalysts and biomass and cracking conditions, the selectivity of total phenols reached 61.2 area% at 300°C, but the yield of bio-oil was less than 15.0 wt.%. Albeit the previous works have made great progress, the following challenges are still faced: 1) extra catalyst is associated with the cost and the environmental issue in the synthesis; 2) the selectivity of phenols and yield of bio-oil failed to increase at the same time; and 3) the catalytic effect of biochar produced by microwave pyrolysis and alkali metal from biomass is often ignored.
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