Xin Song,Fangjun Shao,Zijiang Zhao,Xiaonian Li,Zhongzhe Wei,Jianguo Wang
Precise regulation of reaction selectivity at high conversions is the key to non-terminated alkyne semi-hydrogenation. Herein, a support modification strategy was employed to incorporate trace amounts of Mg elements into alumina support. The modified support loaded Pd catalyst optimized the activity and selectivity of the non-terminated alkyne semi-hydrogenation reaction. The TEM and XRD characterization of the catalysts demonstrated the entry of Mg elements into the Al 2 O 3 lattice to achieve the modification of the support. For the 2-butyne-1-ol semi-hydrogenation reaction, the Pd 0.5 /Mg 1 @Al 2 O 3 catalyst showed 99 % conversion and 97 % selectivity of the cis product at hydrogen pressure of 0.1 MPa and 25 °C. The introduced Mg element changed the electronic structure of Pd nanoparticles in the catalyst. The precise regulation of the 2-butyne-1-ol semi-hydrogenation reaction was achieved by adjusting the ratio of Pd 0 to Pd 2+ using the synergistic effect of Pd 0 and Pd 2+ .
Yu Jin,Haifeng Wu,Shuai Huo,Siyu Chen,Lili Shen,Hongjie Di,Lianfeng Du,Peng Li
Livestock and poultry farming effluents (LPFE) have become a significant source of pollution in the agricultural water environment, with nitrogen (N) and phosphorus (P) being the major pollutants. The use of inexpensive Mg2 + -modified materials as crystallization carriers can enhance the struvite crystallization and precipitation reaction, enabling efficient recovery of N and P nutrients from LPFE. In this study, Mg2 + -modified corncob biochar (CCBC-Mg) and Mg2 + -modified natural zeolite (NZ-Mg) were assessed for their simultaneous recovery of N and P from LPFE. BET, SEM-EDS, FTIR, XRD and adsorption isotherm and adsorption kinetics modelling were used to study the N and P adsorption properties and mechanisms. The results showed that Mg2 + modification significantly enhanced the simultaneous ammonia nitrogen (AN) and total phosphorus (TP) recovery of the two materials. After modification, corncob biochar (CCBC-Mg) showed the best P recovery performance, while natural zeolite (NZ-Mg) showed the best AN recovery, with adsorption quantities reaching 116.99 mg/g and 47.50 mg/g, respectively. The findings demonstrated that the adsorption processes for both AN and phosphate across all materials adhered to the pseudo-second-order kinetic model and Langmuir isotherm, collectively indicating that monolayer adsorption governed by chemical interactions was the predominant mechanism. CCBC and NZ mainly adsorbed AN and TP by electrostatic attraction and ion exchange, whereas CCBC-Mg and NZ-Mg, mainly relied on struvite precipitation on the material surface. The Mg2 + - modification increased the solution pH and formed Mg-P precipitates on the material surface, providing a favourable alkaline environment and nucleation conditions for the struvite reaction, thereby promoting the simultaneous recovery of AN and TP by the materials. This study could provide a theoretical basis for the design of struvite carrier for the simultaneous recovery of AN and TP from LPFE by the struvite precipitation method, and promote the application of this process in livestock and poultry farming effluent treatments.
In spite of a strong visible light absorbance as far as 600 nm, CaNbO 2 N generally exhibits poor photocatalytic activity under normal conditions because of various structural defects and poor charge mobility. In this work, we have synthesized a series of Mg-modified CaNbO 2 N, i.e. CaNb 1-x Mg x O 2+y N 1-y (0 ≤ x ≤ 0.2), and performed a detailed investigation on their crystal structures, optical absorption and other physicochemical properties. Our results show that there is a slight shrinkage of the unit cell and a blue-shift of absorption edges upon Mg incorporation into CaNbO 2 N. The nitrogen contents as well as defects levels can be effectively tuned by altering the content of Mg. More strikingly, photocatalytic oxygen productions are much improved after Mg modifications under visible light irradiation (λ ≥ 420 nm). An average oxygen production rate as much as ∼126.8 umol h −1 and an apparent quantum efficiency as high as ∼3.4 % at 420 ± 20 nm is achieved for CaNb 0.9 Mg 0.1 O 2+y N 1-y (x = 0.1). These improvements probably stem from a substantial decrease of Nb 4+ defects in CaNbO 2 N as well as slight positive shift of valence band maximum (VBM) after Mg modifications. Meanwhile, photoelectrochemical analysis suggests charge migration is somewhat enhanced in response to Mg modifications.
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