Improvement of low-temperature NH 3 -SCR catalytic activity over Mn-Ce oxide catalysts supported on sewage sludge char a
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pISSN: 0256-1115 eISSN: 1975-7220
INVITED REVIEW PAPER
INVITED REVIEW PAPER
Improvement of low-temperature NH3-SCR catalytic activity over Mn-Ce oxide catalysts supported on sewage sludge char activated with KOH and H3PO4 Junchao Xu*,**,†, Xiangyang Zhang*, Yunlan Sun***, Hongming Long*,†, and Zhimin Zheng* *Key Laboratory of Metallurgical Emission Reduction & Resources Recycling (Anhui University of Technology), Ministry of Education, 243002 Maanshan, P. R. China **Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, Jiangsu Province, P. R. China ***School of Petroleum Engineering, Changzhou University, Changzhou 213164, Jiangsu Province, P. R. China (Received 25 April 2020 • Revised 1 July 2020 • Accepted 11 July 2020) AbstractPyrolysis is a very potential sludge treatment technology that is low-cost and environmentally friendly; particularly, the pyrolysis sewage sludge char (SC) can be used as a catalyst support. To improve the NO conversion efficiency of sludge char based catalysts, they were activated by potassium hydroxide and phosphoric acid, respectively. The catalysts of activated sludge char with or without Mn-Ce impregnation in the application of NO removal by lowtemperature SCR were investigated. The higher NO conversion efficiency of sludge char based Mn-Ce catalysts at low temperature were obtained. Compared with the 59% NO conversion efficiency of Mn-Ce/SC catalyst, the conversion efficiency of catalyst supported on KOH activated char (SCK) achieved 89% at 220 oC and of catalyst supported on H3PO4 activated char (SCP) reached 87% at 240 oC. The catalysts were analytically characterized using N2 adsorptiondesorption, XRD, FTIR, NH3-TPD and XPS measurements. The higher specific area, excellent dispersion of Mn-CeOx and more Brønsted acid sites are responsible for the higher NO conversion efficiency of Mn-Ce/SCK, while the higher NO conversion efficiency of Mn-Ce/SCP is enhanced by more Brønsted acid sites, oxygen-containing and some unique phosphorus-containing oxygen functional groups. It indicates that sludge char activated by KOH and H3PO4 is a potential low-temperature catalyst support. Keywords: Low-temperature, SCR, Sludge Char, Mn-Ce Catalyst, Chemical Activation
SCR deNOx catalysts [14]. Especially, MnOx has been drawn much attention due to its excellent low temperature catalytic performance. However, pure MnOx catalysts generally have small specific surface area and their structure is unstable, which makes them unsuitable for practical applications [15]. Therefore, it is usually supported on a catalyst support to achieve higher performance. Many studies have investigated MnOx/TiO2 catalysts and the results show that the deNOx efficiency could reach more than 90% at low temperature [16,17]. However, the sulfur and water resistance of MnOx/ TiO2 catalysts is very poor. Moreover, Jin [18] and Sjoerd [19] introduced SO2 and water into simulated flue gas and found that the SO2 could produce ammonium sulfate covering the active
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