The influence of urea on composition, microstructure and electrochemical properties of nitrogen-enriched carbon based on polyvinylpyrrolidone/melamine formaldehyde resin

Purpose – The purpose of this paper is to develop porous nitrogen-enriched carbon (NC-U) with high nitrogen concentration and high specific capacitance (Cpe) as the electrode material for supercapacitors. Design/methodology/approach – NC-U was obtained by carbonization of polyvinylpyrrolidone/melamine formaldehyde resin (PVP/MF) with different contents of urea. In comparison, NC-K was also prepared by the KOH activation method. A series of asymmetric supercapacitors with NC as a negative electrode was assembled. The composition, microstructure and electrochemical properties of NC and their supercapacitors were studied. Findings – The results show that NC-U shows irregular particles with a porous honeycomb structure. High Cpe was obtained for urea-treated NC-U because of the improvement of nitrogen, conductivity and specific surface area (S BET ). NC-U50 with 13.15 per cent at nitrogen has the highest Cpe of 148.53 F/g because of the highest concentration of N-6 and N-5. NC-K with higher S BET has lower Cpe than NC-U50 because of its lower nitrogen concentration. When the specific power of the supercapacitor with NC-U50 as a negative electrode is 1,565.56 W/kg, its specific energy is still 4.35 Wh/kg. There is only 5.9 per cent decay in Cpe over 1,000 cycles. Research limitations/implications – NC-U is a suitable electrode material for supercapacitors, which can be used in the field of electric vehicles to solve the problems of energy shortage and environmental pollutions. Originality/value – Porous NC-U based on PVP/MF/urea composites with high nitrogen concentration and Cpe is novel, and it owns good electrochemical properties.

Fast Pyrolysis of Soy Hulls in a Fluidized Bed Reactor: Main Components of the Bio-Oil

The fast pyrolysis is an efficient and promising process of thermal decomposition. The process consists in the reaction of organic materials in the total or partial absence of oxygen to produce condensable vapor, non-condensable gases and char. Bio-oil is generated after vapor condensation and it can be converted into fuels and/or chemicals. Fast pyrolysis of soy hulls was conducted in a batch reactor fluidized bed, made of stainless steel, with internal diameter of 78 mm and 1069 mm height. The fast pyrolysis of soy hulls, mixed with inert (sand), was carried out at approximately 550 °C. Atmosphere with high nitrogen concentration was used. The present study aimed to investigate the chemical composition of the soy hulls bio-oil using gas chromatography and mass spectrometry techniques.