Jie Zhu,Tongxin Qu,Shengli Niu,Jisen Liu,Sitong Liu,Jie Geng,Zihao Yang,Abulikemu Abulizi
The development of reusable heterogeneous catalysts with acid-base bifunctions employing low-cost oil as a raw material is critical for optimizing the biodiesel synthesis process. In the present study, Sr–La/wollastonite bifunctional catalysts with the different Sr/La atomic ratios are synthesized using a straightforward impregnation technique. The results show that the Sr 7 La 3 /wollastonite catalyst establishes a biodiesel yield of 95.35% upon initial use and 85.14% after the fifth cycle of reuse, under the transesterification conditions of a catalyst content of 8 wt.%, methanol to oil molar ratio of 15, reaction duration of 3 h, and reaction temperature of 150 °C. The biodiesel yield of 91.62% is obtained even after the addition of 5 wt.% oleic acid, and the catalyst maintains a high biodiesel yield (>80%) for three reused cycles, which illustrates the good resistance to free fatty acids (FFAs). Meanwhile, the process parameters for transesterification are optimized utilizing Response Surface Methodology combined with Box-Behnken Design (RSM-BBD). With a methanol to oil molar ratio of 17.7 and a catalyst content of 6.4 wt.%, biodiesel yield is 96.08% at 149 °C for 3 h. This study revealed the enormous potential of the Sr–La/wollastonite bifunctional catalyst in biodiesel production.
Zhiyuan Pan,Sihan Feng,Fan Li,Xuejiao Wang,Qi Zhu,Ji-Guang Li
Near-infrared phosphor converted light-emitting diodes (NIR pc-LEDs), as a state-of-the-art type of NIR sources, are finding multifaceted applications, where phosphor is a crucial component. In hope to provide new choices for NIR lighting, we synthesized in this work the two series of Ruddlesden -Popper type layered perovskite phosphors of SrLa 2 Al 2- x O 7 : x Cr 3+ ( x = 0–0.02) and SrLa 2- y Gd y Al 1.984 O 7 :0.016Cr 3+ ( y = 0–2), followed by detailed structure and luminescence investigation. SrLa 2 Al 2- x O 7 : x Cr 3+ was found to emit ∼700–800 nm NIR light under UV excitation and be able to maintain ∼54.3 % of its room temperature intensity at 423 K, which is remarkably higher than those (∼25–30 %@423 K) of the Mn 4+ activated perovskite NIR phosphors. Luminescence regulation was achieved by substituting La 3+ with Gd 3+ , and it was revealed that Gd 3+ may act as a sensitizer to significantly enhance Cr 3+ luminescence (∼346 % at 77 K) through Gd 3+ → Cr 3+ energy transfer, which was confirmed by spectral and fluorescence lifetime analysis. The observed spectral features and the influence of Gd 3+ were rationalized by considering crystal structure, local coordination, and crystal field. Finally, an NIR pc-LED device showing strong ∼700–900 nm luminescence was fabricated to show potential application of the phosphor in night vision and plant lighting.
Jin Chen,Naoyuki Hatada,Wenhao Li,Wenzhuo Chen,Donglin Han
Heavily acceptor-doped perovskite oxides have the potential to activate percolation conduction of protons at reduced temperatures, and the reported percolation proton conductors up to now are restricted to the systems containing high Sc content. However, larger trivalent rare earth elements (e.g., Y) are known to be better dopants for proton conducting zirconates, but their solubility is low. In this work, we propose a new strategy to design the percolation proton conducting perovskites, by introducing La and Y into the Sr and Zr-sites of SrZrO 3 , respectively, leading to the formation of (Sr 1.1- x La x -0.1 )(Zr 1- x Y x )O 2.95 (SLZY, x = 0.1 – 1.0), which takes Pnma and Pna 2 1 orthorhombic structures with x = 0.1 – 0.4 and 0.5 – 1.0, respectively. Interestingly, the conductivity decreases with the Y content increasing from 0.1 to around 0.7 and increases with the Y content further increasing to 1.0. Moreover, the activation energy of the bulk conduction shows the maximum value at x = 0.6. In addition to the expected monotonically increasing activation energy resulted from the enhanced structural asymmetry, these results imply that the trapping effect of protons plays an important role, which is enhanced with Y content increasing from 0.1 to around 0.6. Notably, higher Y content (e.g., x > 0.6) appears to activate the percolation conduction of protons, leading to the decreasing activation energy.
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