Relationship between pore structure and hydration activity of CaO from carbide slag

CaO needs to show high activity to be used as Ca-sorbent and slagging agent. Hydration activity is an important characteristic to evaluate the activity of CaO. In this study, carbide slag from polyvinyl chloride (PVC) industry was utilized as precursor for preparing high activity CaO. The roles of crystallite grain, average pore diameter (APD) and volume fraction of pore < 200 nm in diameter (VF200) in hydration activity of CaO from carbide slag (CS-CaO) were respectively investigated. The hydrolysis kinetics model of CaO shows a three-dimensional spherically symmetric diffusion model (D4), which suggests that hydration activity was mainly associated with APD and VF200 of CS-CaO with limited correlation to the crystal size. Specifically, the hydration activity of CS-CaO is increased with increasing VF200, while decreased with increasing APD. Under the invariable calcination temperature, the core-shell structure formed by the addition of graphite or CaCO₃ to CS effectively inhibits the sintering of CS-CaO and improves VF200. Consequently, the hydration activity of CS-CaO increased from 22.79℃·min^-1 to 27.19℃·min^-1 and to 29.27℃·min^-1, with addition of 5% graphite or 5% CaCO₃ into carbide slag, respectively.     

Advances of experimental study on gas production from synthetic hydrate reservoir in China

China has entered the area of new normal economy which requires the harmonious development of energy consumption, environmental protection and economic development. Natural gas hydrate is a potential clean energy with tremendous reserve in China. The successful field test of marine hydrate exploitation in South China Sea created a new record of the longest continuous gas production from natural gas hydrate. However, the corresponding fundamental research is still urgently needed in order to narrow the gap between field test and commercial production. This paper reviewed the latest advances of experimental study on gas production from hydrate reservoir in China. The experimental apparatus for investigating the performance of hydrate dissociation in China has developed from one dimensional to two dimensional and three dimensional. In addition, well configuration developed from one tube to complicated multi-well networks to satisfy the demand of different production models. Besides, diverse testing methods have been established. The reviewed papers preliminary discussed the mechanical properties and the sediment deformation situation during the process of hydrate dissociation. However, most reported articles only consider the physical factor, the coupled mechanism of physical and chemical factor for the mechanical properties of the sediment and the sand production problem should be studied further.     

The effect of A-site nonstoichiometry on the microstructure,electric properties,and phase stability of NaNbO3 polycrystalline ceramics

The impact of A-site nonstoichiometry on the microstructure, electric properties, and phase stability of sodium niobate ceramics (Na_1+xNbO₃, x = ?2 to 1 mol %) was investigated. All the components maintained an orthorhombic antiferroelectric (AFE) structure. The grain size increased from 3.9 to 14.3 μm with the variation in x from ?2 to 1. The AFE–FE phase transition electric field dramatically increased from 100 kV cm^?1 at x = 0 to 170 kV cm^?1 at x = ?2, confirming the enlarged energy barrier between AFE Pbma and FE Pmc2₁ phase under external field in A-site deficient components. This is attributed to the lattice compressive stress generated by introducing proper A-site vacancies. Combined results of transmission electron microscopy and Raman spectroscopy indicated that the AFE distortion of Pbma phase was significantly enhanced in A-site deficient components, which jointly contributed to the stability of AFE phase in A-site deficient NaNbO₃ material.     

Aminolysis of ethyl acetate in continuous flow and its reaction kinetics

The aminolysis of ethyl acetate was promoted significantly via continuous reaction in a tubular reactor. N-propylacetamide was thus synthesized without presence of solvent and catalyst. The optimum conditions were obtained as follows:the reaction temperature is 218℃, the reaction pressure is 3.5 MPa, the molar ratio (ethyl acetate:N-propylamine) is 1:1, and the residence time is 350 min. Accordingly, the conversion of ethyl acetate is up to 94.8%. Furthermore, the kinetics of the rapid reaction stage (when the conversion of ethyl acetate is 20%-80%) can be expressed as lnk--4629:44 1/T + 2:1366, and the apparent activation energy is E_a=38489 J·mol^-1.