Deactivation and in-situ regeneration of Dy-doped Ni/SiO2 catalyst in CO2 reforming of methanol

• Published in: International journal of hydrogen energy Vol. 48; no. 55; pp. 21224 - 21239
• Main Authors: Hoang Duy, Nguyen Phuc, Phuong, Nguyen Nguyen, Bao Ngoc, Le Thi, Tri, Nguyen, Nguyen, Hong-Ha T., Vo, Dai-Viet N., Thuy Phuong, Pham Thi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30-06-2023
• Subjects: CO2 reforming; Deactivation; Dy-doped Ni/SiO2 catalyst; In-situ regeneration; Methanol; In-situ regeneration; Deactivation; CO2 reforming; Dy-doped Ni/SiO2 catalyst; Methanol
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2022.08.096

The self-regeneration of Ni-based catalysts has been considered as a promising approach to maintain not only a continuous but also economical process. However, the effect of catalyst nature, operating temperature, amount and types of carbon deposits on the effectiveness of the in-situ regeneration is still not well-investigated. Therefore, in this work, the self-regeneration ability of the undoped and Dy-doped Ni/SiO2 catalysts, which were prepared by the same impregnation method, were examined in the dry reforming of methanol. The physicochemical properties of the fresh and spent catalysts were analyzed by various techniques such as X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), oxygen temperature-programmed desorption (O2-TPD), transmission electron microscopy (TEM), N2-BET isothermal adsorption. The nature and chemical reactivity of coke deposits formed during dry reforming at various temperatures (550, 600, and 650 °C) and the regeneration possibility of used catalysts through CO2 gasification at these temperatures were investigated by the in-situ temperature-programmed gasification by CO2 (TPCO2). The Dy additive significantly improves the dispersion of the nickel active sites of Ni/SiO2 catalyst, as demonstrated by the decreased Ni crystal size as well as the increased specific surface area and reduction degree of the catalyst. Furthermore, Dy promotion increases the quantity of oxygen vacancies and the nature of oxygen species, thereby improving the catalyst activity and stability. Specifically, methanol conversion dropped from 93% to 96%–61% and 31% for undoped Ni/SiO2 at 600 °C and 650 °C, respectively and from about 99% to 87% (at 600 °C) and 52% (at 650 °C) for Dy-doped catalyst.
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•Self-regeneration ability of Ni-catalysts for CO2 reforming of methanol was studied.•Dy additive significantly improves the performance of Ni/SiO2 catalyst.•Carbon deposits on Dy–Ni/SiO2 were completely removed by CO2 reactant at 600°C.•Activity of Dy–Ni/SiO2 was fully restored after 60 min of turning off methanol.