Novel Bamboo-Mediated Biosynthesis of MnO<i><sub>x</sub></i> for Efficient Low-Temperature Propane Oxidation
Daifeng Lin, Xiaoshan Feng, Changlin Cao, Hun Xue, Yongjin Luo, Qingrong Qian, Lingxing Zeng, Baoquan Huang, Songwei Yang, Qinghua Chen
Abstract
Small-size MnOx nanoparticles with good reducibility, fast lattice oxygen mobility, and large acid sites are first obtained by bamboo-mediated biosynthesis, showing promising propane (C3H8) oxidation activity. The COO–, −C–O–, and −C═O functional groups in bamboo powder (BP) act as complexing species, and the presence of organic carbon is responsible for bioreduction of Mn ions during calcination. The above bifunctional roles increase the content of Mn2+ in MnOx, which contributes to large amounts of oxygen vacancies and then increases oxygen mobility, and the chief Mn substance of Mn3+ species in the obtained primary phase of Mn2O3 is recognized as the active sites for total C3H8 oxidation. It is revealed that BP treated by sequential NaOH (pH = 13) and HCl solutions (pH = 1) (BP-13-1) is the best media for biosynthesis, where alkaline treatment is to increase the number of complexing species and the acid solution is to eliminate the negative role of alkali metal ions (Na+, K+). As a result, the obtained BP-13-1-mediated biosynthesis of MnOx (MnOx-BP-13-1) shows a much higher reaction rate of 2.96 μmolC3H8 gcat–1 s–1 at 300 °C, while it is only 0.38 μmol C3H8 gcat–1 s–1 for the reference sample MnOx without BP modification. Moreover, MnOx-BP-13-1 shows excellent thermal stability and good resistance against 5 vol % H2O and 5 vol % CO2. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results reveal that CH2CHCH3 is the dominant intermediate species in MnOx-BP-13-1 with a lower reaction barrier compared to unmodified MnOx.