RESUMEN
To enhance the reaction kinetics without sacrificing activity in porous materials, one potential solution is to utilize the anisotropic distribution of pores and channels besides enriching active centers at the reactive surfaces. Herein, by designing a unique distribution of oriented pores and single crystalline array structures in the presence of abundant acid sites as demonstrated in the ZSM-5 nanorod arrays grown on monoliths, both enhanced dynamics and improved capacity are exhibited simultaneously in propene capture at low temperature within a short duration. Meanwhile, the ZSM-5 array also helps mitigate the long-chain HCs and coking formation due to the enhanced diffusion of reactants in and reaction products out of the array structures. Further integrating the ZSM-5 array with Co3O4 nanoarray enables comprehensive propene removal throughout a wider temperature range. The array structured film design could offer energy-efficient solutions to overcome both sorption and reaction kinetic restrictions in various solid porous materials for various energy and chemical transformation applications.
RESUMEN
The management of plastic wastes has become an urgent issue due to the overconsumption of single-use plastic products. As a promising avenue for plastic waste valorization, chemical recycling by converting plastics into value-added products has attracted tremendous attention. In this paper, the Fe-Ni alloy catalysts via in-situ exsolution were employed for the straightforward microwave plasma-initiated decomposition of plastic wastes for high yield H2 and carbon nanotubes. The partial substitution of Fe by Ni promoted in-situ exsolution of alloy nanoparticles homogeneously. Specifically, characterization results showed that the introduction of Ni modulated metal-support interaction, which further affected the crystalline phase, nanoparticle size and oxygen vacancies. The exsolved Fe-Ni alloy catalyst exhibited the highest catalytic activity, over which 96 % hydrogen of plastic wastes rapidly evolved out in the form of gas products accompanied with high-purity carbon nanotubes. The H2 yield was 415 mmol·g-1Hplastic, which exhibited an over 2 times improvement versus the supported catalyst. Moreover, the successive cycle test displayed the potential for converting plastic wastes into H2-rich fuels and high-quality CNTs continuously. Generally, the in-situ exsolution strategy of Fe-Ni alloy catalysts contributed to the sustainable and high-efficient recycling of plastic wastes into H2-rich gas products and carbon nanotubes under microwave plasma.
RESUMEN
Surface oxygen activities always play an important role in various heterogeneous reaction processes. In this study, the surface oxygen activity of studied perovskite oxides is greatly enhanced after the composition and morphology are tuned. It is worth noting that the surface oxygen activity is enhanced correspondingly, accompanied by higher surface area, better reducibility, and superior low-temperature reactivity of studied catalysts. The sample introduced with nickel atom and nanorods structure possesses higher surface oxygen activity and vacancies with superior performance including T10 at 221 °C and T90 at 243 °C, nearly 90 °C elevations. Double perovskite oxides, especially with nanorods structure are verified to be composed of more surface active oxygen, which could be related to low-temperature redox ability and superior oxygen vacancies. Based on the DFT calculation, introducing nickel element is confirmed to be able to efficiently boost the generation of oxygen vacancies and adsorption of oxygen molecular, in accord with the analysis of characterization. To sum up, the strategy of introducing the nickel atom and nanorods structure could effectively tune the surface oxygen activity and generate more oxygen vacancies, which would be beneficial to the catalytic performance of toluene catalytic oxidation correspondingly.
RESUMEN
Cobalt oxides have been considered as a kind of highly efficient catalyst for the oxidation of volatile organic compounds (VOCs). In this work, lanthanum-cobalt composite oxides were prepared by using the co-precipitation method, and toluene was used as the model compound. Diversified techniques including XRD, SEM, Raman spectra, XPS, H2-TPR, and N2 adsorption-desorption were applied to investigate the physicochemical properties of as-prepared materials. The composite catalysts showed different morphology including larger specific surface area and higher pore volume which would accelerate the adsorption of toluene and improve the amount of active sites on surface. Moreover, the addition of lanthanum could enhance the low-temperature reducibility, and it could be also beneficial to expose more Co3+ and adsorbed oxygen species on the surface of catalysts which could accelerate the oxidation of toluene and lower onset oxidation temperature. 0.05La-Co (with a molar ratio of lanthanum against cobalt is 0.05) showed the best catalytic performance. The complete conversion of toluene was achieved at 225 °C under the condition of toluene concentration = 1000 ppm and SV = 20,000 ml·g-1·h-1. Stability test over 0.05La-Co was conducted at 225 °C and it could maintain the 100% conversion of toluene for 720 min, indicating the excellent stability of as-prepared catalysts. Undoubtedly, lanthanum-cobalt composite oxide is a kind of promising material for the catalytic oxidation of VOCs.
