Nano Catalyst Design and Application in Sustainable Chemistry

Heterogenous catalytic process is a complex art of surface, the surface properties, especially the properties of active sites such as geometric structure and chemical environment would drastically influence the reaction performance. Traditionally, most studies for catalyst surface properties rely on the ex situ characterisation which examines catalysts out of reaction condition. However, considering most of the heterogenous catalytic reactions are carried out under a harsh condition, i.e. elevated temperatures and pressures, the surface dynamic change over catalyst under reaction condition is generally not negligible and dominating the reaction performance. Thus, for understanding the real catalyst surface behaviour, we must observe the catalyst during reaction condition. Three different catalytic systems were selected in this research and the combined in situ microscopy and spectroscopy techniques, including in situ TEM, in situ EELS spectroscopy and in situ DRIFTS spectroscopy, were implemented to investigate the catalyst behaviour during the reactions. The first reaction is the oxidative methane coupling reaction over Li/MgO. Then followed by the oxidative methane coupling over La/MgO and ammonia synthesis over Ru/MgO. The in situ TEM provides the information of surface geometric change while the in situ EELS and DRIFTS give the chemical information of catalyst surface as well as adsorbed intermediates. Combined with ex situ characterisation results, the more comprehensive pictures for the mechanism of the investigated reactions can be depicted. The outcome of this thesis bridged the gap between surface geometric-chemical change over catalysts active sites and the reaction performance over heterogenous catalyst, which might even be the guidance for heterogenous catalyst development in the similar systems

Cooperation of hierarchical pores with strong Brønsted acid sites on SAPO-34 catalysts for the glycerol dehydration to acrolein

The hierarchical SAPO-34 zeolites have been prepared with the simultaneous generation of strong Brønsted acid sites (BASs) via a post-synthetic method, which allows the cooperation of the positive effects of both porous structure and acidity in the dehydration of glycerol to acrolein. The cooperation of strong BASs only in enhancing the acrolein selectivity and the hierarchical pores in improving the glycerol conversion has significantly increased the overall acrolein yield to 89.8% on the hierarchical SAPO-34 zeolite at 345 °C and WHSV = 3.7 h−1. This kind of cooperation also limited the catalyst deactivation and prolonged the lifetime of zeolites, which is another significant challenge for glycerol dehydration. The knowledge from this research is very valuable to design the high-efficient nanoporous catalysts for hydrocarbon conversion and bio-refining

CO2 Hydrogenation Using Size-dependent Ru Particles Supported on g-C3N4

Efficient catalysis of CO2 hydrogenation holds significant promise for addressing environmental concerns and advancing sustainable energy solutions. In this study, we report the synthesis of a novel series of Ru-supported on graphitic carbon nitride (g-C3N4) catalysts, with a focus on the impact of ruthenium (Ru) loading on the thermocatalytic performance. Varying Ru concentrations were introduced, including 0.2, 0.5, 1.0, 2.0, and 5.0 wt%, resulting in different Ru particle sizes on g-C3N4 support. Through a multifaceted characterization approach, it was observed that the catalyst containing 1 wt% Ru loading displayed superior performance, with a high density of active sites, indicated by an enhanced CO2 conversion rate of 36.8 % at 450 °C and a CO yield of 25 %. This catalyst also exhibited remarkable CO selectivity of 83 % at 375 °C. Conversely, lower loadings of 0.2 and 0.5 wt % Ru were found to be less effective, yielding minimal CO2 conversion. Loadings above 1 wt% Ru, while achieving high CO2 conversion, demonstrated a preference for CH4 production over CO, indicating lower selectivity for the desired product. This study elucidates the critical role of Ru nanocluster size in the catalytic activity and selectivity, with 1 wt % Ru-supported g-C3N4 emerging as a promising candidate for selective CO generation from CO2 hydrogenation, offering a pathway for the valorization of CO2 as a raw material in the chemical industry

The Influence of CaO and MgO on the Mechanical Properties of Alkali-Activated Blast Furnace Slag Powder

CaO and MgO are both reported as effective activators for blast furnace slag. However, the synergistic effect of these two components on the mechanical properties of alkali-activated blast furnace slag remains unclear. In this study, the flexural and compressive strengths of alkali-activated blast furnace slag powder with MgO and CaO range from 0% to 30% by the mass ratio of alkali-activated blast furnace slag powder are investigated. Moreover, the dry shrinkage rate of alkali-activated blast furnace slag powder is measured. One percent refractory fibers by volume of binder materials are added in the alkali-activated blast furnace slag. Some refractory fibers are treated with water flushing, meanwhile, some refractory fibers are directly used without any treatment. Finally, the scanning electron microscope, the thermogravimetric analysis curves and the XRD diffraction spectrums are obtained to reflect the inner mechanism of the alkali-activated blast furnace slag powder’s mechanical properties. The water-binder ratios of the alkali-activated blast furnace slag powder are 0.35 and 0.42. The curing ages are 3 d, 7 d and 28 d. The measuring temperature for the specimens ranges from 20 °C to 800 °C. Results show that the flexural and compressive strengths increase with the increased curing age, the decreased water-binder ratio and the addition of refractory fibers. The water-treated refractory fibers can improve the mechanical strengths. The mechanical strengths increase in the form of a quadratic function with the mass ratio of MgO and CaO, when the curing age is 3 d, the increasing effect is the most obvious. A higher water-binder ratio leads to an increasing the drying shrinkage rate. The activated blast furnace slag powder with CaO shows a higher drying shrinkage rate. The mechanical strengths decrease with the increasing testing temperature

Influence of Carbon Dioxide Curing on the Corrosion Resistance of Reinforced Cement Mortar under the External Erosion of NaCl Freeze–Thaw Cycle

Carbon dioxide (CO2)-cured concrete is a novel material that can effectively reduce CO2 emissions in the atmosphere. However, limited research has been found to investigate the corrosion behavior of CO2-cured reinforced concrete. In this paper, the corrosion resistance of reinforced cement mortar is investigated. The mortars were cured in CO2 for 1 day~28 days. Water–cement ratios (w/c) of 0.3, 0.4 and 0.5 were designed. The corrosion resistance of inner steel bars was researched by the methods of ultrasonic velocity, electrical parameters (AC electrical resistance, Tafel curve method and AC impedance spectroscopy). Moreover, scanning electron microscope was selected for observing the micro-morphology of CO2-curing mortar. X-ray diffraction spectrum was used to characterize components of steel bars’ passive films. The results show that CO2 can effectively increase electrical resistivity and ultrasonic velocity, thus improving the corrosion resistance of reinforced cement mortar. The enhancement of carbon dioxide curing increases with the increasing w/c. The mass-loss rate, the electrical resistivity and the decreasing rate of ultrasonic velocity increase with the increasing sodium chloride freeze–thaw cycles, indicating the continuous increase in the corrosion degree of reinforcement. The corrosion deterioration degree of steel bars decreases with the increasing CO2-curing time. Specimens with w/c of 0.3 and 0.4 show the highest and lowest corrosion deterioration resistances after sodium chloride freeze–thaw cycles. Microscopic characterization found that CO2 curing could increase the corrosion resistance of the inner steel bars by improving the compactness of the cement matrix. Moreover, the iron oxides on the surface of the passivation film decreased after CO2 curing

Designing Carbon‐Based Porous Materials for Carbon Dioxide Capture

Abstract Rapid industrialization and urban development around the world have significantly increased carbon dioxide emissions, adversely affecting climate and ecosystems. Therefore, carbon capture and storage emerged as a promising route to reduce environmental CO2 concentration. Among various CO2 capture technologies, adsorption through carbon‐based porous materials has attracted particularly strong attention. This is primarily due to their high specific surface area, selective CO2 adsorption, moderate heat of adsorption, tunable morphology, and reduced degradation in moisture. This review critically examines carbon‐based CO2 sorbents derived from diverse sources. The key factors controlling adsorption performance, including the impact of structural and functional properties are discussed. The future research directions in this rapidly emerging field, contributing to the decarbonization of the global economy and society, are highlighted

Tuning Hierarchical ZSM-5 Zeolite for Both Gas- and Liquid-Phase Biorefining

A hierarchical ZSM-5 zeolite with an adjustable mesoporous size is required for many chemical processes including the biorefining of big biomass compounds. In this research, a simple and high-efficiency hard template method has been successfully developed by adopting carbon nanoparticles obtained from carbonation of polyethylene oxide and urea. The abundant −C–O–C– groups on the surface of carbon nanoparticles provide the high hydrophilicity (from −C–O–C– to −C–O–H) in the alkaline synthetic gel solution, which promotes the synthesis of hierarchical ZSM-5 zeolite and the aluminum condensation in the silica framework to improve the Brønsted acidity. The as-synthesized hierarchical zeolites exhibited two sets of channel systems: micropores (∼0.55 nm) are from the MFI framework network, and mesopores (∼12.5 and ∼34.5 nm) result from carbon nanoparticles of 10–40 nm in size, respectively. The hierarchical ZSM-5 with minimized extraframework aluminum species showed catalytic performance with high ethanol conversion (100%) and high stability (lifetime above 30 h) in the ethanol to olefins conversion. Importantly, the diffusion efficiency in ZSM-5 with mesoporous size was remarkably improved, compared to the catalyst with mesoporous size ∼12.5 nm. As the benzylation of mesitylene with benzyl alcohol, the ZSM-5 (∼34.5 nm) sample showed the highest conversion in benzyl alcohol (82.0%) and selectivity in 2-benzyl-1,3,5-trimethylbenzene (74.3%)

Tailoring multiple porosities of hierarchical ZSM-5 zeolites by carbon dots for high-performance catalytic transf

A simple and high‐efficiency method is proposed to synthesize hierarchical ZSM‐5 zeolites with micropore and multistage mesopores by adopting water‐soluble carbon dots (CDots) with various size distributions, such as 1‐stage size distribution of CDots‐1 of around 23 nm, 2‐stage size distribution of CDots‐2 of 6 and 9 nm, 3‐stage size distribution of CDots‐3 of 5, 8, and 18 nm. The abundant OH and COOH groups on the surface of CDots provide high solubility in water. The characterization techniques confirmed that the dual‐porous h‐ZSM‐5 (MIcro–mEsopores) and multi‐porous h‐ZSM‐5 (MIcro–mEso–mEsopores), h‐ZSM‐5 (MIcro–mEso–mEso–mEsopores, M‐IEEE) catalysts are obtained. Notably, the hierarchical ZSM‐5(M‐IEEE) catalyst with micropore of 0.55 nm, two small mesopores of 4.8 and 7.4 nm, and one large mesopore of 17.5 nm show excellent catalytic performance with the highest 1,3,5‐triisopropylbenzene (TIPB) cracking conversion (97.3%) and high stability. Similarly, the h‐ZSM‐5(M‐IEEE) shows the high ethanol to olefins conversion (100%). The improved catalytic activity can be attributed to the more efficient diffusion of reactants and products in the crystals with the help of multistage mesopores, improved anti‐coking stability, combined with the effect of suitable acidity, and the increased accessibility of the acid sites

In Situ Polymerization of Furfuryl Alcohol with Ammonium Dihydrogen Phosphate in Poplar Wood for Improved Dimensional Stability and Flame Retardancy

Fast-growing plantation wood normally possesses some undesirable intrinsic properties, such as dimensional instability, inferior mechanical strength, and flammability, limiting its usage as an engineering material. Herein, we report a green and facile approach for upgrading the low-quality poplar wood via a combined treatment with biomass-derived furfuryl alcohol (FA) and ammonium dihydrogen phosphate (ADP) acting as a flame-retardant additive. Wood/PFA/ADP composites were prepared by impregnation of the FA precursor solutions into the wood matrix, followed by in situ polymerization upon heating to form a hydrophobic FA resin/ADP network within the wood scaffold. In-depth scanning electron microscopy coupled with enregy-dispersive X-ray spectroscopy (SEM-EDX) and confocal laser scanning microscopy (CLSM) analyses reveal the wide distribution of the FA resin/ADP complexes inside the cell walls and also in the cell lumens. The incorporation of hydrophobic FA resin into wood results in reduced water uptake and remarkably enhanced dimensional stability, as well as generally improved mechanical properties. The addition of a small amount of ADP greatly enhances the flame retardancy of the modified wood and also effectively suppresses smoke generation during its combustion by reducing the heat-release rate and promoting char formation, as proven by cone calorimetry. The FA resin/ADP complexes increase phosphorus fixation in wood and reduces its leaching into water, suggesting a long-term fire protection of wood in service. Such modified poplar wood with overall enhanced properties could be potentially utilized as a reliable engineering material for structural applications