Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Optimizing zeolitic hierarchical pore structure to boost the direct conversion of aromatics from syngas over the iron-based/zeolite bifunctional catalysts
No full textThe utilization of iron-based/ZSM-5 bifunctional catalysts for converting syngas to aromatics (STA) has garnered significant interest because of its cost-effectiveness. This study aims to elucidate the regulatory mechanism of zeolitic pore structure on the performance of the bifunctional catalyst in STA reaction. The relationship among the mesoporosity and mesoporous diameter of hierarchical ZSM-5 zeolite component, product distribution, and catalyst stability is investigated through a range of analyses techniques, including XRD, SEM, TG, Raman, N2adsorption and desorption. The results demonstrate that as the mesoporosity of zeolite increased to 78.9%, the lifetime of the iron-based/ZSM-5 bifunctional catalyst extended beyond 96 h and maintained the aromatics selectivity over 40% at 2 MPa, 320 degrees C, and 3000 h-1. This outcome can be attributed to the role of high mesoporosity in restraining coke formation in zeolites. Moreover, the reduction in mesopore size from 11.1 to 5.8 nm results in an increased aromatics selectivity from 39.6% to 43.4%, and the fraction of light aromatics rose from 48.8% to 54.5%, indicating that small mesopore size can also expedite the production of aromatics, particularly light aromatics. It is thus concluded that the improvement of aromatics selectivity and stability of iron-based/ ZSM-5 bifunctional catalysts in STA reaction can be achieved by increasing the mesoporosity and decreasing the mesopore size of the zeolite component
Study of efficient catalytic electrode for hydrogen evolution reaction from seawater based on low tortuosity corn straw cellulose biochar/Mo2C with porous channels
No full textPorosity and channel structure has important effects on the performance of hydrogen evolution reaction (HER) of nanostructured electrocatalysts in acid solution and seawater. Mesopore usually helps to enhance the reaction kinetics and mass transfer, while the macroporous channel structure also affects the electrocatalyst. Traditional graphene materials do not have such structure. Therefore, this paper designs a method to synthesize Mo2C composite nanomaterial in situ on corn straw biochar, inspires by the natural channel structure of conducting water, salt and organic matter in plants. Characteristic characterization shows that the material also has a large number of mesoporous and vertical distribution of large porous channel structure, through the decrease of tortuosity and porosity, ensure the catalyst surface electrolyte transport and hydrogen timely escape, alleviate the process of metal ion precipitation blocking pore channel, so as to improve the rate of hydrogen evolution reaction. The results shows that the overpotential of the catalyst was 48 mV and 251 mV under 10 mA cm-2 acidic electrolyte and simulated seawater electrolyte, respectively. This method provides new ideas for the design of efficient electrocatalysts for seawater decomposition, then the HER performance in alkaline and neutral environments needs to be further explored
Efficient selective hydrogenation of terminal alkynes over Pd-Ni nanoclusters encapsulated inside S-1 zeolite
No full textSelective hydrogenation of alkynes is a challenging reaction that requires selective and efficient catalysts to achieve the desired alkenes. The development of general and robust catalysts that can operate under mild conditions and tolerate a wide range of functional groups is still an active area of research. Here, Pd-M bimetallic clusters (M = Ni, Cu, Mn, Fe) encapsulated inside S-1 zeolite were prepared and applied in the selective hy-drogenation of substituted terminal alkynes. Among them, the Pd0.6Ni@S-1 catalyst displayed 91 % selectivity to styrene at the full conversion of phenylacetylene. Derivatives of phenylacetylene containing either electron withdrawing/donating or sensitive functional groups were effectively converted into the corresponding alkenes. The confinement effect of zeolite effectively inhibited the over-hydrogenation reaction and enhanced the stability of the catalysts. Furthermore, the product distribution was solvent-dependent by correlating the reaction selectivity with solvent properties. Apolar solvent showed the highest selectivity to styrene in the selective hydrogenation of phenylacetylene due to the competitive adsorption of apolar solvent and styrene on catalysts
Preparation of Ar-P-N-structured flame retardant via Kabachnik-Fields reaction for fire safety and mechanical reinforcement of polyurethane
No full textFire safety of polyurethanes (PUs) has limited their further practical applications. To address this problem, we designed novel phosphorus-based flame retardants (P-FR) by incorporating aryl (Ar) groups via Kabachnik-Fields reaction, realizing pi-pi interaction-reinforced Ar2 and Ar5. Total heat release and peak heat release rate of PU/Ar5, whose flame-retardancy-index of 5.02 due to reduced combustion time, decreased 23.24 and 9.23 %, respectively, compared with neat PU. Moreover, UL94 rating for PU/Ar5 was improved from V-2 to V-0. These results demonstrate that Ar5 effectively generate a barrier effect that blocks oxygen, fuel, and heat. Sluggish mobility and phase transition are responsible for such enhancement due to a delay effect with the existence of pi-pi interactions and steric hindrance. Encouragingly, tensile strength and toughness of PU/Ar5 were greatly improved by 1345.8 and 670.3 %, respectively, compared with neat PU. We believe that this study could provide a promising method for introducing specific function to flame retardants to enhance fire safety and mechanical properties of composites
Experimental and kinetic modeling study of tar partial oxidative reforming by dielectric barrier discharge plasma using toluene as a model compound
No full textIn this study, partial oxidation of toluene as a biomass tar surrogate was carried out in a dielectric barrier discharge (DBD) plasma reactor. In order to understand the reaction characteristics and thus potential of the approach, the effect of reaction temperature, O2/toluene molar ratio (OTR) and discharge power on performances was investigated by experiments and kinetic modeling. The results showed that the three factors could change the E/n and hence the G-values of species, as well as alter O2 concentration in background gas and input energy, leading to the variation in active species production and thus, the performance. Appropriate high temperatures, as well as higher OTRs and discharge power obtained better performances by promoting toluene destruction and gas product production. Excited N2 species play a crucial role in the process, by means of participating in reactions directly and strongly influencing on the production of secondary active species. At 300 degrees C, the highest toluene conversion of 100.0 % with an energy efficiency of 25.7 g/kWh was achieved without catalysts usage, a comparable performance as compared to the steam reforming by plasma catalysis, demonstrating the potential of this method for the purification of gasification gases. Furthermore, based on the rate of production (ROP) and sensitivity analyses of the model developed, as well as experimental results, the reaction mechanism was proposed
Experimental and kinetic modeling study of tar partial oxidative reforming by dielectric barrier discharge plasma using toluene as a model compound
No full textIn this study, partial oxidation of toluene as a biomass tar surrogate was carried out in a dielectric barrier discharge (DBD) plasma reactor. In order to understand the reaction characteristics and thus potential of the approach, the effect of reaction temperature, O2/toluene molar ratio (OTR) and discharge power on performances was investigated by experiments and kinetic modeling. The results showed that the three factors could change the E/n and hence the G-values of species, as well as alter O2 concentration in background gas and input energy, leading to the variation in active species production and thus, the performance. Appropriate high temperatures, as well as higher OTRs and discharge power obtained better performances by promoting toluene destruction and gas product production. Excited N2 species play a crucial role in the process, by means of participating in reactions directly and strongly influencing on the production of secondary active species. At 300 degrees C, the highest toluene conversion of 100.0 % with an energy efficiency of 25.7 g/kWh was achieved without catalysts usage, a comparable performance as compared to the steam reforming by plasma catalysis, demonstrating the potential of this method for the purification of gasification gases. Furthermore, based on the rate of production (ROP) and sensitivity analyses of the model developed, as well as experimental results, the reaction mechanism was proposed
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