γ-Al2O3 loaded with potassium nitrate (KNO3/Al2O3) catalysts were prepared, characterized and employed as a type of heterogenous solid base catalyst in the synthesis of polycarbonate (1,4-butane carbonate)-diol (PBC–OH) via the transesterification of dimethyl carbonate (DMC) and 1,4-butanediol (BD). The relationship between physicochemical properties and catalytic performance for KNO3/Al2O3 in this transesterification reaction was investigated using various techniques. The results demonstrated that the performance of KNO3/Al2O3 catalysts was highly influenced by basic site amount and strength. The medium and strong basic sites were beneficial for this reaction. The catalyst with a KNO3 loading of 35% and a calcination temperature of 700 °C exhibited the best catalytic activity due to its highest basic site amount and appropriate base strength. The highest BD conversion and PBC–OH yield of 80.2% and 68.4% were obtained under optimal reaction conditions. Also, this solid base catalyst was successfully employed in the synthesis of copolycarbonate diols from DMC and two different diols. Different scanning calorimetry results indicated that the thermal properties of the copolycarbonate diols can be adjusted by regulating the average segment lengths, Mn and copolymer composition structure.
In this study, a novel catalyst, S 2 O 8 2− -KNO 3 /TiO 2 , which has active acidic and basic sites, was prepared and used in lignin hydrocracking with a co-catalyst, Ru/C. Ru/C is an efficient hydrogenation catalyst and S 2 O 8 2− -KNO 3 /TiO 2 is a dual catalyst, which could efficiently degrade lignin. This catalytic hydrogenation system can reduce solid products to less than 1%, while giving a high liquid product yield of 93%. Catalytic hydrocracking of kraft lignin at 320 °C for 6 h gave 93% liquid product with 0.5% solid product. Most of this liquid product was soluble in petroleum ether (60% of 93%), which is a clear liquid and comprises mainly of monomeric and dimeric degradation products . These results demonstrated that the combination of the two catalysts is an efficient catalyst for liquefaction of lignin, with little char formation (∼1%). This concept has the potential to produce valuable chemicals and fuels from lignin under moderate conditions.
To manipulate the melting temperature of phase change material for more flexible match with practical applications, two eutectic mixtures of BHO (barium hydroxide octahydrate)-KCl and BHO-KNO 3 were investigated as novel binary inorganic eutectic system in this study. Given that the latent heat of BHO-KNO 3 eutectic mixture was higher than that of BHO-KCl eutectic mixture, then BHO-KNO 3 /EG (expanded graphite) composite phase change material (CPCM) with high thermal conductivity was fabricated by melting impregnation method. The thermal properties and performance were assessed using differential scanning calorimeter , thermogravimetry analyzer and thermal conductivity test. The crystalline structure and morphology were revealed by X-ray diffraction and scanning electron microscopy. These results revealed that the two eutectic mixtures still possessed high latent heat more than 200J/g when containing 10 wt% KCl and 12 wt% KNO 3 , respectively. In light of the similar melting temperatures of the two eutectic mixtures, it could be concluded that melting point altering was related to K + . It was worth noting that for BHO-KNO 3 /EG composite phase change material, EG not only improved the thermal conductivity up to 7.27 W•m -1 •K -1 as an excellent heat transfer enhancement filler, but also reduced the supercooling degree by 7.6 °C as an effective nucleation-site provider.
LiNO3-NaNO3-KNO3-NaNO2has a relatively low phase-change temperature, making it suitable for low-temperature heat utilization systems. This study focuses on the performance optimization of the quaternary molten salt to advance its applicability. A series of nanocomposites consisting of nano-SiO2/MgO and the quaternary salt are prepared. Core thermophysical properties, including phase transition behaviors and thermal transport parameters, are quantified. The incorporation of nano-SiO2/MgO induces moderate adjustments to the melting point and latent heat yet demonstrates an obvious enhancement in specific heat capacity. Optimal doping at 0.7 wt.% SiO2and 0.3 wt.% MgO yields a molten-state specific heat of 1.51 J/(g·K), representing a 6% increase over the undoped base salt (1.42 J/(g·K)). By combining the thermal diffusivity properties of the samples, this study found that the doping of nanoparticles typically induces new structures in molten salts that tend to enhance the specific heat capacity while simultaneously reducing thermal diffusivity.
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