High-value utilization of mask and heavy fraction of bio-oil: From hazardous waste to biochar, bio-oil, and graphene films.

At present, it is very common to wear mask outdoors in order to avoid coronavirus disease 19 (COVID-19) infection. However, this leads to the formation of numerous plastic wastes that threaten humans and ecosystem. Against this major background, a novel co-pyrolysis coupled chemical vapor deposition (CVD) strategy is proposed to systematically convert mask and heavy fraction of bio-oil (HB) into biochar, bio-oil, and three-dimensional graphene films (3DGFs) is proposed. The biochar exhibits high higher heating value (HHV) (33.22-33.75 MJ/kg) and low ash content (2.34%), which is obviously superior to that of the walnut shell and anthracite coal. The bio-oil contains rich aromatic components, such as 1,2-dimethylbenzene and 2-methylnaphthalene, which can be used as chemical feedstock for insecticides. Furthermore, the 3DGF800 has a wide range of applications in the fields of oil spill cleanup and oil/water separation according to its fire resistance, high absorbability (40-89 g g-1) and long-term cycling stability. This research sheds new light on converting plastic wastes and industrial by-products into high added-value chemicals.

Two-step pyrolysis of corncob for value-added chemicals and high-quality bio-oil: Effects of alkali and alkaline earth metals.

Two-step pyrolysis (TSP) of corncob(CC) coupled with water and acid washing pretreatment was conducted to investigate the effects of alkali and alkaline earth metals (AAEMs) on TSP by Py-GC/MS. TG-FTIR was used to analyze the pyrolysis characteristics of the samples. The results showed that the removal of AAEMs postponed the pyrolysis process and significantly influenced the distribution of the pyrolysis products. As the content of AAEMs decreased, the bio-oil yield increased and the biochar yield decreased. TSP of CC achieved high selectivities for phenols and ketones in the first step and for hydrocarbons in the second step. TSP of acid-washed corncob (ACC) achieved high selectivities for furans in the first step and for sugars in the second step. Additionally, some value-added chemicals such as furfural (11.54%, ACC), 4-vinylphenol (23.57%, CC) and levoglucosan (43.05%, ACC) were also enriched in TSP. Therefore, a promising polygeneration scheme of TSP for the efficient utilization of biomass was proposed.

Study on the effect of condensing temperature of walnut shells pyrolysis vapors on the composition and properties of bio-oil.

The effect of condensing temperature on composition of bio-oil obtained via fractional condensation was investigated by pyrolysis-condensation experiments of walnut shells at condensing temperatures from 290 K to 370 K. The condensing efficiency of the first stage condenser decreased from 0.59 to 0.12 with increasing temperature. Moisture of bio-oil decreased from 40% to 5%, but the C/O ratio increased from 0.50 to 1.50. Compared with contents observed at the lowest condensation temperature, the maximum content of each component increased by 50%-500%. Combined with variations in condensing efficiency and composition content, the optimum condensing temperature range for declining water in bio-oil was 340-350 K. The condensing temperature associated with the enrichment of acetic acid and furfural was 345 K. The 355 K optimum condensing temperature could be selected to achieve the maximum enrichment of guaiacol and its derivatives.