Catalytic fast pyrolysis of alkali-pretreated bagasse for selective preparation of 4-vinylphenol

Abstract

Herbaceous biomass has been confirmed as a promising renewable source to produce the valuable phenol compound 4-vinylphenol (4-VP) from low temperature fast pyrolysis process. In this work, a novel and simple method was proposed to increase 4-VP production via alkali pretreatment of herbaceous biomass. Three alkali compounds, i.e., Ca(OH)2, NaOH and Na2CO3, were adopted to pretreat sugarcane bagasse for catalytic fast pyrolysis to selectively produce 4-VP. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were firstly conducted to investigate the effects of alkali type, alkali content, pyrolysis temperature, and pretreatment time on 4-VP formation. Quantitative results of 4-VP yield and selectivity suggested that Ca(OH)2 was the optimal catalyst for bagasse pretreatment. Under pyrolysis temperature of 280°C with impregnation time of 10 min and Ca(OH)2 content of 1 wt%, the highest 4-VP yield of 6.37 wt% and selectivity of 58.90% were obtained, compared with the yield and selectivity of 4.28 wt% and 39.95% from raw bagasse. Furthermore, a lab-scale fixed bed reactor was employed for fast pyrolysis of Ca(OH)2 pretreated bagasse to quantitatively determine the distribution of solid, liquid and gas products. The maximal yield of 4-VP was 6.57 wt% obtained at 310°C. In addition, characterization of Ca(OH)2 pretreated bagasse samples indicated that alkali pretreatment facilitated the release of 4-VP precursor during the impregnation process.