The highly dispersed active sites are desirable to optimize the atom efficiency. In this study, a series of novel cobalt grafted in N-doped carbon (Co-N-C) catalysts for selective oxidation of ethylbenzene are synthesized by heating a solution of cobalt porphyrin and peptides in ionic liquids, which are also characterized by techniques such as FT-IR, XRD, SEM-EDX, HR-TEM, and XPS. The results show that the as-prepared catalysts have an attractive catalytic performance, namely, 40% of ethylbenzene conversion and 75% of selectivity to acetophenone. Especially, the activity and selectivity of the as-prepared catalysts remain almost similar even after the 10th run. Moreover, the modified-complexometry method is verified to improve the dispersion of metal active sites. The remarkable catalytic performance of the as-prepared catalysts is attributed to the highly dispersed active sites and strong interactions between Co and N species in Co-N x moieties.
Tian Liu,Xingrong Zeng,Xuejun Lai,Hongqiang Li,Yanlin Wang
Organosilicon materials with high capacity of organic-to-inorganic conversion at elevated temperature are always favorable in the field of high-temperature-resistant materials, flame retardant materials, chemical engineering and functional materials in electrical engineering. In this work, it was found out that the platinum-nitrogen catalytic system could obviously enhance the organic-to-inorganic conversion efficiency of silicone rubber (SiR) at elevated temperature. The residual rate of Pt/N/SiR (SiR containing 0.33 phr Karstedt's catalyst (Pt) and 2 phr nitrogenous silane (N)) at 1000 °C was significantly improved from 3.0% to 44.8% in comparison with SiR and its thermal stability was also enhanced. DLS , TEM and UV–vis absorption spectrometry revealed that the platinum in Karstedt's catalyst would aggregate at elevated temperature and deteriorate its catalytic activity for organic-to-inorganic conversion of SiR. And the addition of nitrogenous silane can efficiently inhibit the aggregation and retain the high catalytic efficiency of platinum. A thorough TG-FTIR study, together with SEM/EDX and XPS analyses suggested that the platinum-nitrogen system might suppress the intramolecular cyclic transition and enhance the radical coupling between polymer chains of SiR during thermal degradation , which resulted in the high capacity of organic-to-inorganic conversion of Pt/N/SiR at elevated temperature.
Yuezhou Wei,Khalid A.M. Salih,Kamal Rabie,Khalid Z. Elwakeel,Yasser E. Zayed,Mohammed F. Hamza,Eric Guibal
Alginate-PEI beads are functionalized by phosphorylation and applied for the sorption of Nd(III) and Mo(VI). The successful grafting of phosphoryl groups (as tributyl phosphate derivative) is characterized by FTIR and XPS analysis, elemental analysis, titration (pH PZC ), TGA, BET and SEM-EDX analyses. The multi-functional characteristics of the sorbent (i.e., carboxylic, hydroxyl, amine and phosphate groups) contribute in the binding of metal ions having different physicochemical behaviors. The sorption of Nd(III) is strongly increased by phosphorylation, while for Mo(VI) the enhancement is rather limited. Optimum sorption occurs at pH 3–4: maximum sorption capacity reaches up to 1.46 mmol Nd(III) g −1 and 2.09 mmol Mo(VI) g −1 ; sorption isotherms are fitted by the Langmuir equation. The equilibrium is reached within 30–40 min and the kinetic profiles are simulated by the pseudo-first order rate equation. The coefficients of the effective diffusivity are close to the self-diffusivity of Nd(III) and Mo(VI) in water; as a confirmation of the limited impact of resistance to intraparticle diffusion in the kinetic control. The sorbent is selective for Nd(III) over Mo(VI) and other alkali-earth or base metals (at pH close to 2.5–3). Metals can be readily desorbed using 0.2 M HCl/0.5 M CaCl 2 as the eluent. The loss in sorption does not exceed 5% at the fifth cycle, while desorption remains complete. A series of treatments (including acidic leachate, cementation, precipitation, sorption and elution) is successfully applied for the recovery of rare earths from Egyptian ore; with enrichment in the oxalate precipitate of Nd(III), Gd(III), Sm(III) and Eu(III).
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