The pyrolysis of hydrochar from hydrothermal treatment of kitchen waste was investigated, including the process parameters and characteristics of pyrolysis products. A novel process, KOH-assisted catalytic pyrolysis , was proposed to simultaneously produce oil and char products with high quality. The optimum pyrolysis temperature was 550 ℃, at which the three-state products presented better properties. Four zeolite catalysts were investigated to improve the quality of the oil product. SAPO presented the highest promoting effect on aromatic hydrocarbons, whereas HZSM-5 promoted the selectivity of nitrogen components. Upon KOH addition, the selectivity of aromatic hydrocarbons increased from 42.2% to 98.8% for HZSM-5, whereas oxygen- and nitrogen-containing substances disappeared. In addition, the char S BET increased from 7.16 to 1753.57 m 2 /g, with specific capacitance of 206 F/g and methylene blue adsorption capacity of 317.68 mg/g. The results provide a useful background for the development of the treatment of hydrochar.
Xin Liu,Yong-De Yan,Yun Xue,Yue-Lin Wang,Qing-Guo Zhang,Guan-Qing Hu,Fu-Qiu Ma,Jing-Ping Wang
Waste resins produced from nuclear facilities operation always contain organic sulfur and radioisotope 65 Zn, which pose a significant threat for the ecological environment. This study proposed comparative research for treating cation exchange resins doped with Zn 2+ (Zn-CERs) in Na 2 CO 3 -K 2 CO 3 and Na 2 CO 3 -K 2 CO 3 -KOH. The enhanced removal effect of sulfur and Zn 2+ by KOH addition was explored. The energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were carried out to investigate the element distribution and chemical states of C, O, S and Zn on Zn-CERs. The results of thermogravimetric analysis (TG) showed that the oxidation process of Zn-CERs was basically divided into three steps, and Zn 2+ acted as a catalyst for S-C destruction. The relatively mild reaction of Zn-CERs in Na 2 CO 3 -K 2 CO 3 -KOH largely avoids the escape of harmful gases (H 2 S and SO 2 ) caused by the overreaction. The participation of KOH could promote the sulfation of sulfides and sulfites, and the transformational SO 4 2− content reaches a maximum value (26.51 %) at 800 °C. When the temperatures above 700 °C, Zn 2+ and K + combines with SO 4 2− to form K 2 Zn 2 (SO 4 ) 3 . The proposed enhanced molten salt oxidation (MSO) system had excellent retention rates of Zn (99.56 %) and S (87.39 %) at 800 °C, which provides further technical references for the removal of organic sulfur and heavy metals.
The use of porous carbons for selective CO2 separation attracts increasing attention. Owing to low thermostability of porous polymers, low yield is the major concern of porous carbons. To obtain porous carbons with high yield, the development of thermostable porous polymers is highly expected. Herein, high yielded (70% for 700 °C and 64% for 800 °C) Sn-doped porous carbons (SnPCs) have been constructed through KOH-assisted carbonization of Sn-containing polymer. Notably, SnPC-700 (218.5 mg·g–1) demonstrates higher CO2 adsorption capacity than the reference sample prepared without KOH, SnPC-700r (188.3 mg·g–1), indicating the importance of KOH-assisted activation. Carbonization temperature has an effect on the adsorption capacity of resultant materials, and high carbonization temperature leads to better adsorption capacity on CO2. SnPC-800 is able to capture 242.8 mg·g–1 of CO2, which is better than some benchmarks including BILP-7 (193.0 mg·g–1), PAF-1–450 (196.4 mg·g–1), and FCTF-1 (205.5 mg·g–1). More importantly, SnPC-800 demonstrates good selectivity of CO2 over CH4 (31.1). Thus, high yield and good performance upon CO2 adsorption capacity and selectivity over CH4 make SnPCs attractive candidates for the removal of CO2 from natural gas.
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