Synthesis and performance of a novel bio-oil-based dispersant as coal water slurry

Abstract

With pyrolytic bio-oil as raw material, an efficient bio-oil-based dispersant (BOBD) applied to coal water slurry (CWS) has been synthesized successfully by grafting polymerization of the organic fractions from the bio-oil and acrylic acid (AA) in the mild condition. As a comparison, two commercial dispersants, namely poly (styrene sulfonic acid) sodium (PSS) and sodium lignosulfonate (SL) were employed. The structures and properties of the synthesized BOBD were characterized by using FTIR, 1H NMR, GC/MS, GPC, zeta potential, contact angle, and surface tension. The results showed the molecular weight of the BOBD was concentrated at 832 g/mol and 1954 g/mol. The surface tension and contact angle of BOBD aqueous solution were 47.71mN/m−1 and 60.8° respectively. The zeta potential of the suspension prepared from BOBD-water-coal was −67.1 mV. Using BOBD as a dispersant, the apparent viscosity of CWS loading 66 wt% coal dropped to 288 mPa·s at 0.3 wt% BOBD, and the maximum coal content reached 72 wt%. BOBD exhibited better viscosity reduction and stability enhancement capabilities than PSS and SL. The excellent dispersion performance of BOBD was due to the large electrostatic repulsion and steric hindrance derived from the grafted acrylic polymer, which effectively dispersed the coal particles uniformly. The rheological behavior of CWS with BOBD belonged to pseudoplastic fluid. The synthesized BOBD not only had an excellent dispersion performance but also could overcome the shortcomings of secondary pollution caused by PSS and SL containing element sulfur as dispersants in combustion. In addition, the synthetic route possessed simple, environmentally friendly and sustainable characteristics. The research opened up a new way for the utilization of bio-oil.