Abstract
The sodium-treated sepiolite (NaSep)-supported rare earth oxide (RE/NaSep; RE = La, Eu, Dy, and Tm) samples were prepared using the rotary evaporation method. Physicochemical properties of these materials were characterized by XRD, SEM, BET, FTIR, XPS, H2–TPR, NH3–TPD, and in situ DRIFTS, and their catalytic activities for formaldehyde (HCHO) (2000 ppm) oxidation were evaluated. The results show that loading of the rare earth oxide on NaSep improved its catalytic performance. Among all the samples, Eu/NaSep performed the best, and complete HCHO conversion was achieved at a temperature of 150 °C and a gas hourly space velocity of 240,000 mL/(g h); a good catalytic activity was still maintained after 45 h of stability test. The catalytic oxidation mechanism of HCHO was studied using the in situ DRIFTS technique. As a result, the effective and stable catalytic performance of the Eu/NaSep sample was mainly due to the presence of hydroxyl groups on the sepiolite surface and the doped rare earth oxides, which contributed to its high performance. HCHO oxidation underwent via the steps of HCHO + O2 → HCOO− + OH− → H2O + CO2. It is concluded that the optimal catalytic activity of Eu/NaSep was associated with the highest Oads/Olatt atomic ratio, the largest amount of hydroxyl groups, the highest acidity, and the best reducibility. The present work may provide new insights into the application in the removal of high-concentration HCHO over the rare earth oxides supported on natural low-cost clays.
Highlights
Formaldehyde (HCHO) is a harmful pathogenic gas emitted from decorative materials and ordinary furniture [1]
Sepiolite (NaSep), Eu/Na-treated sepiolite (NaSep), Dy/NaSep, La/NaSep, and XRDpatterns patternsofofsodium-treated sodium-treated sepiolite (NaSep), Eu/NaSep, Dy/NaSep, La/NaSep, and FTIR is usually used to 3670 analyze the structure of amorphous crystals and short-range ordered materials, which can show the structure of a material more comprehensively.480Figure 2 shows the FTIR
From the in situ DRIFTS results, it was found that hydroxyl groups could quickly adsorb HCHO on the sample surface, and loading of the rare earth oxide could generate a more amount of oxygen vacancies that served as the active sites for HCHO oxidation, as evidenced by its highest Oads /Olatt atomic ratio revealed by the X-ray photoelectron spectroscopic (XPS) analysis
Summary
Formaldehyde (HCHO) is a harmful pathogenic gas emitted from decorative materials and ordinary furniture [1]. A’lvarez et al [10] reported that 0.4 wt % Pd–Mn/Al2 O3 catalyst could completely oxidize HCHO to CO2 and H2 O at 90 ◦ C These catalysts are difficult to be widely utilized due to their high cost. Loading of rare earth is expected to overcome shortcomings of the supported noble metal catalysts and possess several advantages of lower cost and better thermal stability. Zhu et al [12] synthesized the Au–CeO2 catalysts for the oxidation of HCHO and observed good activities of the materials at low temperatures. Na-treated sepiolite (NaSep) as a support to prepare the RE/NaSep (RE = La, Eu, Dy, and Tm) catalysts, and explored their physicochemical properties, catalytic activities, reaction mechanisms, and stability for HCHO (2000 ppm) oxidation at a gas hourly space velocity (GHSV) of 240,000 mL/(g h)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
