Mechanisms of isomerization and hydration reactions of typicalβ-diketone at the air-droplet interface

Acetylacetone(AcAc)is a typical class ofβ-diketones with broad industrial applications due to the property of the keto-enol isomers,but its isomerization and chemical reactions at the air-droplet interface are still unclear.Hence,using combined molecular dynamics and quantum chemistry methods,the heterogeneous chemistry of AcAc at the air-droplet interface was investigated,including the attraction of AcAc isomers by the droplets,the distribution of isomers at the air-droplet interface,and the hydration reactions of isomers at the air-droplet interface.The results reveal that the preferential orientation of two AcAc isomers(keto-and enol-AcAc)to accumulate and accommodate at the acidic air-droplet interface.The isomerization of two AcAc isomers at the acidic air-droplet interface is more favorable than that at the neutral air-droplet interface because the“water bridge”structure is destroyed by H_(3)O^(+),especially for the isomerization from keto-Ac Ac to enol-AcAc.At the acidic air-droplet interface,the carbonyl or hydroxyl O-atoms of two AcAc isomers display an energetical preference to hydration.Keto-diol is the dominant products to accumulate at the air-droplet interface,and excessive keto-diol can enter the droplet interior to engage in the oligomerization.The photooxidation reaction of AcAc will increase the acidity of the air-droplet interface,which indirectly facilitate the uptake and formation of more keto-diol.Our results provide an insight into the heterogeneous chemistry ofβ-diketones and their influence on the environment.

Carbonation Reaction of Lithium Hydroxide during Low Temperature Thermal Energy Storage Process

In order to apply lithium hydroxide(LiOH)as a low temperature chemical heat storage material,the carbonation reaction of LiOH and the prevention method are focused in this research.The carbonation of raw LiOH at storage and hydration condition is experimentally investigated.The results show that the carbonation reaction of LiOH with carbon dioxide(CO_(2))is confirmed during the hydration reaction.The carbonation of LiOH can be easily carried out with CO_(2) at room temperature and humidity.LiOH can be carbonated at a humidity range of 10%to 20%,a normal humidity region that air can easily be reached.Furthermore,the carbonation reaction rate has not nearly affected by the increase of reaction temperature.An improved storage method by storing LiOH at a low humidity less than 1.0%can be effectively prevented the carbonation of LiOH.The hydration reaction ratio of LiOH at the improved storage method shows a better result compared to the ordinary storage method.Therefore,the humidity should be carefully controlled during the storage of LiOH before hydration and dehydration reaction when apply LiOH as a low heat chemical storage material.

A coupled model of temperature and pressure based on hydration kinetics during well cementing in deep water

Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl₂Hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat. CaCl2 was used in the system of CHP. We evaluated the heat storage and heat releasing of CHP, and confirmed the practicality from the experimental results. The reactor module employed was an aluminum plate-tube heat exchanger with corrugated fins, and the CaCl2 powder was in the form of a packed bed. Heat storage operation and heat dissipation operation are performed at the same time and supplied to the heat demand destination. At this time, an environmental heat source can be used during the heat radiation operation, and the heat output can release more heat than the heat input during heat storage. The heat discharging and charging characteristics of the reactor module were evaluated experimentally. The coefficient of performance (COP) was calculated for the heat upgrading cycle, and the heat output in the system was determined. A COP of 1.42 and output of 650 W/L, based on the heat exchanger volume, were obtained using a 600 s change time for the heat pump.

Crystal reconstruction of V_(2)O_(3)/carbon heterointerfaces via anodic hydration for ultrafast and reversible Mg-ion battery cathodes

Magnesium-ion batteries(MIBs)have promising applications because of their high theoretical capacity and the natural abundance of magnesium Mg.However,the kinetic performance and cyclic stability of cathode materials are limited by the strong interactions between Mg ions and the crystal lattice.Here,we demonstrate the unique Mg^(2+)-ion storage mechanism of a hierarchical accordion-like vanadium oxide/carbon heterointerface(V_(2)O_(3)@C),where the V_(2)O_(3) crystalline structure is reconstructed into a MgV_(3)O_(7)·H_(2)O phase through an anodic hydration reaction upon first cycle,for the improved kinetic and cyclic performances.As verified by in situ/ex situ spectroscopic and electrochemical analyses,the fast charge transfer kinetics of the V_(2)O_(3)@C cathode were due to the crystal-reconstruction and chemically coupled heterointerface.The V_(2)O_(3)@C demonstrated an ultrahigh rate capacity of 130.4 mAh g^(-1)at 50000 mA g^(-1)and 1000 cycles,achieving a Coulombic efficiency of 99.6%.The high capacity of 381.0 mA h g^(-1)can be attributed to the reversible Mg^(2+)-ion intercalation mechanism observed in the MgV_(3)O_(7)·H_(2)O phase using a 0.3 M Mg(TFSI)2/ACN(H_(2)O)electrolyte.Additionally,within the voltage range of 2.25 V versus Mg/Mg^(2+),the V_(2)O_(3)@C exhibited a capacity of 245.1 mAh g^(-1)when evaluated with magnesium metal in a 0.3 M Mg(TFSI)^(2+)0.25 M MgCl_(2)/DME electrolyte.These research findings have important implications for understanding the relationship between the Mg-ion storage mechanism and reconstructed crystal phase of vanadium oxides as well as the heterointerface reconstruction for the rational design of MIB cathode materials.

Influence of MgO/MgCl_2 Molar Ratio on Phase Stability of Magnesium Oxychloride Cement

Formation, solution and phase change of hydration products in MgO-MgCl2-H2O system was studied with thermodynamics method, and resistance to water immersion and phase change of magnesium oxychloride cement with different MgO/MgCl2 molar ratio was experimented. The results show that pH value of immersion solution of cement paste has a remarkable influence on phase stability of hydration products. A higher pH value leads to a lower solubility and a better phase stability of hydration products. When the solution pH value is higher than 10.37, the precipitation of much Mg（OH）2 crystal induces a worse phase stability of hydration products. With the increasing MgO/MgCl2 molar ratio （lower than 6）, the more amount of MgO in the hydration products enhances the alkalinity of solution and the phase stability is improved. However, when the MgO/MgCl2 molar ratio is higher than 6 and the excessive MgO exsits in the hydration products, the cement paste may be damaged by the excessive crystallization stress of a great deal of Mg（OH）2 formation.

An improved outer pipe method for expansive pressure measurement of static cracking agents

Static cracking agent(SCA)is actively investigated as an alternative to explosive blasting for rock breakage due to its immense expansion property.SCA can eliminate the negative effects of shock,noise and harmful gases encountered in explosive blasting processes.Accurate measurement and deep understanding of the expansive properties of SCAs are important in their industrial application.An improved outer pipe method(OPM),termed the upper end surface method(UESM),is proposed in this paper to overcome the shortcomings of the OPM in the expansive pressure measurement of SCAs.Numerical simulation is used to proof the concept and a mathematical model established to relate the internal pressure and the radial strains at different positions in the upper end surface method test equipment.The new equipment is calibrated using oil pressure and strain measurements.The calibrated equipment is then used to measure the expansion pressure of SCA at three different water contents to proof its potential.The differences in the measurements with OPM and UESM at three different moisture contents are less than 4%.The experimental results confirm the accuracy and applicability of the more user friendly and less expensive UESM in the measurement of the expansive pressures of SCAs.

Evaluation on the natural gas hydrate formation process

Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compared from six parameters,including conversion of water to hydrate,storage capacity,the rate of hydrate formation,space velocity(SV)of hydrate reaction,energy consumption and hydrate removal.The literature was selected by analyzing and comparing these six parameters mentioned above,meanwhile placing emphasis on the three parameters of storage capacity,the rate of hydrate formation and space velocity of hydrate reaction.Through analysis and comparison,four conclusions could be obtained as follows.Firstly,the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters.Secondly,the additive types,the reactor structure and the reactor size had influence on the natural gas hydrate formation process.Thirdly,the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring,spraying and static higee.Finally,it was one key for hydrate removal to realize the hydrate industrial production.

Mechanism of Clay Mineral Affect on Strength of Solidification Sludge

To solve the problem of vast cement and low strength in the treated sludge, clay mineral used for accessorial solidification material was applied to advance strength. The principle of solidification sludge strength because of clay mineral is not clear and has not supported the choice of clay mineral. The mineral and pore water is analyzed in order to contrast clay mineral added or not based on the XRD and pore water chemical character. The result shows that the absorbed quantity of Ca2~ was reduced by sludge because of clay mineral added, the hydrated reaction was advanced and integrated solidified materials was formed.

Preparation of New Cementitious System using Fly Ash and Dehydrated Autoclaved Aerated Concrete

We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner than 75μm and was then heated to temperatures up to 900 ℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction（XRD） was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content（Wn）. The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 ℃ and the dehydrated products are mainly β-C2 S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fl y ash, increasing the replacement level of fl y ash lowered them in AF. The strength contribution rates on pozzolanic effect of fl y ash in AF are always negative, showing a contrary tendency of that of cement-fl y ash system.

Appraising the potential of calcium sulfoaluminate cement-based grouts in simulated permafrost environments

The aim of this study is to appraise the potential of calcium sulfoaluminate(CSA)cement-based grouts in simulated permafrost environments.The hydration and performance of CSA cement-based grouts cured in cold environments(10,0,and−10℃)are investigated using a combination of tests,including temperature recording,X-ray diffraction(XRD)tests,thermogravimetric analysis(TGA),and unconfined compressive strength(UCS)tests.The recorded temperature shows a rapid increase in temperature at the early stage in all the samples.Meanwhile,results of the TGA and XRD tests show the generation of a significant quantity of hydration products,which indicates the rapid hydration of CSA cement-based grouts at the early stage at low temperatures.Consequently,the CSA cement-based grouts exhibit remarkably high early strength.The UCS values of the samples cured for 2 h at−10,0,and 10℃ are 6.5,12.0,and 12.3 MPa,respectively.The UCS of the grouts cured at−10,0,and 10℃ increases continuously with age and ultimately reached 14.9,19.0,and 30.6 MPa at 28 d,respectively.The findings show that the strength of grouts fabricated using CSA cement can develop rapidly in cold environments,thus rendering them promising for permafrost applications.

Single-phase La_(0.8)Sr_(0.2)Co_(1-x)Mn_(x)O_(3-δ) electrocatalyst as a triple H^(+)/O^(2-)/e^(-) conductor enabling high-performance intermediate-temperature water electrolysis

Hydrogen,especially the“green hydrogen”based on water electrolysis,is of great importance to build a sustainable society due to its high-energy-density,zero-carbon-emission features,and wide-range applications.Today's water electrolysis is usually carried out in either low-temperature(<100℃),e.g.,alkaline electrolyzer,or high-temperature(>700℃)applications,e.g.,solid oxide electrolyzer.However,the low-temperature devices usually suffer from high applied voltages(usually>1.5 V@0.01 A cm^(-2))and high cost;meanwhile,the high-temperature ones have an unsatisfied lifetime partially due to the incompatibility among components.Reasonably,an intermediate-temperature device,namely,proton ceramic cell(PCC),has been recently proposed.The widely-used air electrode for PCC is based on double O^(2-)/e^(-)conductor or composited O^(2-)/e^(-)-H^(+)conductor,limiting the accessible reaction region.Herein,we designed a single-phase La_(0.8)Sr_(0.2)Co_(1-x)Mn_(x)O_(3-δ)(LSCM)with triple H^(+)/O^(2-)/e^(-)conductivity as the air electrode for PCCs.Specifically,the La_(0.8)Sr_(0.2)Co_(0.8)Mn_(0.2)O_(3-δ)(LSCM8282)incorporates 5.8%proton carriers in molar fraction at 400℃,indicating superior proton conducting ability.Impressively,a high current density of 1580 mA cm^(-2) for hydrogen production(water electrolysis)is achieved at 1.3 V and 650℃,surpassing most low-and high-temperature devices reported so far.Meanwhile,such a PCC can also be operated under a reversible fuel cell mode,with a peak power density of 521 mW cm^(-2) at 650℃.By correlating the electrochemical performances with the hydrated proton concentration of single-phase triple conducting air electrodes in this work and our previous work,a principle for rational design of high-performance PCCs is proposed.

Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends:Its effects on setting,workability,and strength development

This study extended blending proportion range of ordinary Portland cement(OPC)and calcium sulfoaluminate(CSA)cement blends,and investigated effects of proportions on setting time,workability,and strength development of OPC-CSA blend-based mixtures.Thermogravimetric analysis(TGA)and X-ray diffraction(XRD)were conducted to help understand the performance of OPC-CSA blend-based mixtures.The setting time of the OPC-CSA blends was extended,and the workability was improved with increase of OPC content.Although the early-age strength decreased with increase of OPC content,the strength development was still very fast when the OPC content was lower than 60%due to the rapid formation and accumulation of ettringite.At 2 h,the OPC-CSA blend-based mortars with OPC contents of 0%,20%,40%,and 60%achieved the unconfined compressive strength(UCS)of 17.5,13.9,9.6,and 5.0 MPa,respectively.The OPC content had a negligible influence on long-term strength.At 90 d,the average UCS of the OPC-CSA blend-based mortars was 39.2±1.7 MPa.