•Porous carbon sphere is firstly made by a novel precursor of waste sugar solution.•Waste sugar solution contains abundant 2-keto-l-gulonic acid.•Porous carbon sphere shows high specific capacitance and stable cycling performance.•The value-added utilization of WSS is achieved for electric double-layer capacitor.Waste sugar solution (WSS), which contains abundant 2-keto-l-gulonic acid, is harmful to the environment if discharged directly. For value-added utilization of the waste resource, a novel process is developed for preparation of porous carbon spheres by hydrothermal carbonization (HTC) of WSS followed by KOH activation. Additionally, the possible preparation mechanism of carbon spheres is proposed. The effects of hydrothermal and activation parameters on the properties of the carbon sphere are also investigated. The carbon sphere is applied to electric double-layer capacitor and its electrochemical performance is studied. These results show that the carbon sphere obtained by HTC at 180 °C for 12 h with the WSS/deionized water volume ratio of 2/3 possess the highest specific capacitance under identical activation conditions. The specific capacitance of the carbon spheres can reach 296.1 F g−1 at a current density of 40 mA g−1. Besides, excellent cycle life and good capacitance retention (89.6%) are observed at 1.5 A g−1 after 5000 cycles. This study not only provides a facile and potential method for the WSS treatment, but also achieves the high value-added recycling of WSS for the preparation of porous carbon spheres with superior electrochemical properties.Download high-res image (239KB)Download full-size image

•Waste sugar residue (WSR) was recycled and was prepared into activated carbon (AC).•Porous ACs were prepared by two-step carbonization/KOH-activation.•AC-600-700-3-2.5 shows the highest specific capacitance of 273.31 F g− 1.•WSR is a potential feedstock for high electrochemical performance AC for EDLC.Waste sugar solution is harmful to the environment and abundant in organic waste, and waste sugar residue (WSR) was obtained by drying waste sugar solution. In order to efficiently solve this issue and created values, activated carbon was prepared by WSR with KOH as activation agent. Carbonization temperature, activation temperature, activation ratio and activation time were investigated, based on the effects of preparation conditions on the electrochemical performance of activated carbon. The electrode material shows superior electrochemical performance, especially when the activated carbon was prepared at the carbonization temperature of 600 °C, activation temperature of 700 °C, activation ratio of 3:1 (KOH:char) and activation time of 2.5 h. It possesses the optimal electrochemical performance with a specific capacitance of 273.31 F g− 1 and a specific surface area of 1953 m2 g− 1. In order to determine the electrochemical stability of activated carbon electrodes, the cycle lifetime was performed at a current density of 1.5 A g− 1. After 5000 cycles, the capacitance retention rate of 90.1% could be obtained. Additionally, the energy density was relatively high at 1.5 A g− 1 (up to 5.09 Wh kg− 1). This study provides a value-added approach for WSR treatment and a potential feedstock for low cost-high performance activated carbons for electric double-layer capacitor.Download high-res image (111KB)Download full-size image

Cerium (Ce)-doped nickel (Ni)-based catalysts supported on modified lignite with HCl were prepared by a co-impregnation method with different Ni/Ce ratios (xNi-Ce/AWSL, where x is 1, 10, 20, 50, and 100, and AWSL is acid-washed Shengli lignite). The promotion effect of Ce with different Ni/Ce weight ratios on structural properties and activity under different atmospheres was investigated in detail. All catalysts were characterized by X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, transmission electron microscopy, and N2 physisorption apparatus. The performance of catalysts was evaluated in a well-designed reactor system for biomass catalytic gasification (BCG). The results indicated that the active component of Ni was dispersed uniformly, and that a high and stable gas yield was obtained over Ce-doped catalysts. Due to the formation of a Ni–Ce alloy, the Ce-doped catalyst with a Ni/Ce weight ratio of 50 : 1 showed the most stable gas yield (69.1%). After carrying out BCG five times, the lowest carbon deposition (weight increase of 1.7%) was obtained under an Ar atmosphere. Spent 50Ni–Ce/AWSL catalyst showed the least carbon deposition, and had the lowest Ni crystallite size (17.3 nm) and smallest average pore size (2.86 nm). The maximum catalytic activity and highest stability for BCG was observed for the catalyst with a Ni/Ce ratio of 50, which showed the best inhibition of carbon deposition.

•Organic oxygen transformation during pyrolysis of Baiyinhua lignite was investigated.•Organic oxygen transformation significantly depended on the pyrolysis temperature.•The tar obtained below 500 °C is rich in organooxygen species, especially phenols.•Above 400 °C, the organic oxygen species mainly released as pyrolysis water and gas.•The oxygen yield in water mainly due to thermal cracking of volatile matter.Fast pyrolysis of a lignite containing a high content of oxygen was investigated to understand the effects of pyrolysis temperature and gas resident time on the yields of pyrolysis products and the distributions of organic oxygen species (OOSs). OOSs in the lignite contain carboxyl, carbonyl, hydroxyl and ether by the results of XPS and FTIR analyses. The tar yield reached the maximum of 15.3% at 500 °C and a gas resident time of 2.5 s. CO2 was found to be the predominant oxygenous gas at 600 °C, and the significant release of CO2 at temperatures lower than 400 °C should be related to the high carboxyl content in the lignite. The CO yield increased significantly with the raising temperature and reached 46.4 mL/g (daf) at 700 °C. The O yield in water was lower than 20% during pyrolysis at 200 °C, and sharply increased to 30.6% at 700 °C because of thermal cracking of volatiles. Above 400 °C, the OOSs are mainly released as pyrolysis water and gas. The OOSs detected in the tar include phenols, ketones, ethers, alcohols, and dibenzofuran and its substitute, among which phenols (phenol, cresol, and xylenol) are the main components with yield up to 27.1% (based on tar) at 500 °C and gas residence time of 10 s. The possible oxygen transformation routes for BYHL pyrolysis are also discussed in this work. Such an approach may lead to the development of efficient lignite upgrading technology.