Improved bio-oil distilling effect by adding additives to enhance downstream bio-oil processing and separation

Abstract This work optimized the physicochemical properties of fraction and effectively separated guaiacols compounds from bio-oil. It aimed to improve the quality and application value of bio-oil fraction. Several kinds of additives were added into the walnut shell bio-oil in the same mass ratio before the bio-oil distillation. The results showed that all additives, except for (NH4)2SO4, increased the pH value of fractions by facilitating the conversion of acidic compounds to salts. Adding additives could decrease the content of ketones and furfural in the fraction and increase the stability of fraction. Meanwhile, the moisture content of fractions was decreased and the content of high-value guaiacols compounds was increased. Among these additives, the minimum moisture content (7.48%), the maximum pH (5.10) of fraction and the maximum yield of high-value guaiacols compounds (increased by 85.89%) all were obtained by adding CO(NH2)2. According to this study, among these additives, CO(NH2)2 could be used into bio-oil pretreatments for enhancing downstream bio-oil processing and separation.