Search Results (2)

Direct decomposition of NO into N₂ and O₂ is an ideal technology for NO_x removal. Catalyst deactivation by sulfur poisoning is the major obstacle for practical application. This paper focuses on strengthening the SO₂ resistance of metal-exchanged HZSM-5 catalysts, by investigating the metals, promoters, preparation methods, metal-to-promoter molar ratios, Si/Al ratios and metal loadings. The results show that in the presence of SO₂ (500 ppm), Fe is the best compared with Co, Ni and Cu. Cs, Ba and K modification enhanced the low-temperature activity of the Fe-HZSM-5 catalyst for NO decomposition, which can be further improved by increasing the exchanged-solution concentration and Fe/Cs molar ratio or decreasing the Si/Al molar ratio. Interestingly, Cs-doped Fe-HZSM-5 exhibited a high NO conversion and low NO₂ selectivity but a high SO₂ conversion within 10 h of continuous operation. This indicates that Cs-Fe-HZSM-5 has a relatively high SO₂ resistance. Combining the characterization results, including N₂ physisorption, XRD, ICP, XRF, UV–Vis, XPS, NO/SO₂-TPD, H₂-TPR and HAADF-STEM, SO₄²⁻ was found to be the major sulfur species deposited on the catalyst’s surface. Cs doping inhibited the SO₂ adsorption on Fe-HZSM-5, enhanced the Fe dispersion and increased the isolated Fe and Fe-O-Fe species. These findings could be the primary reasons for the high activity and SO₂ resistance of Cs-Fe-HZSM-5. Full article

Hydrodeoxygenation (HDO) of bio-oil is a method of bio-oil upgrading. In this paper, x%CeO₂–Ni–Cu/HZSM-5 (x = 5, 15, and 20) was synthesized as an HDO catalyst by the co-impregnation method. The HDO performances of x%CeO₂–Ni–Cu/HZSM-5 (x = 5, 15, and 20) in the reaction process was evaluated and compared with Ni–Cu/HZSM-5 by the property and the yield of upgrading oil. The difference of the chemical composition between bio-oil and upgrading oil was evaluated by GC-MS. The results showed that the addition of CeO₂ decreased the water and oxygen contents of upgrading oil, increased the high heating value, reduced acid content, and increased hydrocarbon content. When the CeO₂ addition was 15%, the yield of upgrading reached the maximum, from 33.9 wt% (Ni–Cu/HZSM-5) to 47.6 wt% (15%CeO₂–Ni–Cu/HZSM-5). The catalytic activities of x%CeO₂–Ni–Cu/HZSM-5 (x = 5, 15, and 20) and Ni–Cu/HZSM-5 were characterized by XRD, N₂ adsorption–desorption, NH₃-Temperature-Programmed Desorption, H₂-Temperature-Programmed Reaction, TEM, and XPS. The results showed that the addition of CeO₂ increased the dispersion of active metal Ni, reduced the bond between the active metal and the catalyst support, increased the ratio of Bronsted acid to total acids, and decreased the reduction temperature of NiO. When the CeO₂ addition was 15%, the activity of catalyst reached the best. Finally, the carbon deposition resistance of deactivated catalysts was investigated by a Thermogravimetric (TG) analysis, and the results showed that the addition of CeO₂ could improve the carbon deposition resistance of catalysts. When the CeO₂ addition was 15%, the coke deposition decreased from 41 wt% (Ni–Cu/HZSM-5) to 14 wt% (15%CeO₂–Ni–Cu/HZSM-5). Full article