MgO对Al2O3瓷性能的影响

研究了ＣａＯ－Ａｌ２Ｏ３－ＳｉＯ３系Ａｌ２Ｏ３ 添加不同量滑石对提高其抗折强度、硬度、耐磨性、密度等性能的影响,探讨了ＭｇＯ在显微结构中所起的作用及影响机理,并找出了形成低温细晶９５Ａｌ２Ｏ３瓷中添加滑石的最佳范围。     

MgO—Al2O3耐火材料的相平衡,显微结构及性能

从沉淀的氧化镁和氢氧化铝中制取四种MgO-Al_2O_3批料,它们的重量比为100/0(MA_1),72/28(MA_2),32/68(MA_3)和0/100(MA_4)。用二步煅烧法将这些批料烧到1600～1700℃,以便于研究它们的相平衡和微观结构。从获得的相图中计算出相平衡的数据,而微观结构则用电子探针显微分析仪分析出来。使它们的液相和微观结构,对煅烧粒粒的致密化参数以及负荷能力进行了分析。可以得出结论,用二步煅烧法将MA_3和MA_4分别烧到1600℃,可以制备出致密的和耐火度高的尖晶石和刚玉粒料,但是用MA_1和MA_2料需要分别烧到1700℃,可产生致密的和高耐火度的方镁石和尖晶石结合方镁石粒料。然而,需要控制添加适量的阳离子添加剂,以使于抑制刚玉、尖晶石与/或方镁石相的间歇式晶粒增大,以便于获得MgO-Al_2O_3煅烧粒料的最大体积密度。     

MgO对95Al2O3瓷性能的影响

本文研究了添加不同量ＭｇＯ对提高刚玉瓷耐磨性，抗折强度，硬度，击穿强度等性能的影射，同时在偏光显微下观察其微观结构，讨论了其影响机是，提出了氧化镁的最佳添加范围。     

钙基材料的制备及其CO2静态吸附应用

烟道气脱碳一直是降低碳排放的重点,由于现行技术的不完备与工艺的复杂性,烟道气脱碳效果与经济性还不是很理想.利用固体废弃物鸡蛋壳制备了钙基吸附材料的前驱体,通过吸附实验发现其有一定的吸附性能,且煅烧后的产品吸附性能明显提高.同时利用单因素实验考察了吸附温度、吸附时间以及循环次数对二氧化碳吸附的影响.结果表明:在600℃条...     

MgO—Al2O3系浇注料的设计

以相关知识和实践经验为依据,探讨了ＭｇＯ－Ａｌ２Ｏ３系中铝镁质（含刚玉－尖晶石质和矾土熟料－尖晶石质）浇注料的基质料的设计和结合剂的合理选择问题。     

K2CO3/金属氧化物吸附CO2的研究

研究了K_2CO_3/MgO和K_2CO_3/Al_2O_3吸附CO_2的性能。研究表明:K_2CO_3/MgO和K_2CO_3/Al_2O_3对CO_2吸附的容量分别为105.8 mg/g和66 mg/g。吸附剂载体是钾基吸附剂吸附CO_2性能差异的原因之一,MgO载体的CO_2吸附容量(42.3 mg/g)大于Al_2O_3(20 mg/g)。钾在不同载体中的物相差异是造成CO_2吸附性能差别的另一原因。在K_2CO_3/MgO吸附剂中,钾仅以K_2CO_3形式存在,在吸附CO_2过程中,CO_2与K_2CO_3以及MgO共同作用生成了K_2Mg(CO_3)_2。而在K_2CO_3/Al_2O_3吸附剂中,不仅有K_2CO_3物相,还检测出KAl(CO_3)_2(OH)_2物相,在吸附CO_2过程中,K_2CO_3转化成KHCO_3,而KAl(CO_3)_2(OH)_2未参与CO_2的吸附。     

Experimental evaluation of Mg- and Ca-based synthetic sorbents for CO2 capture

Hydrogen with high purity can be directly derived from fossil and renewable energy sources, like natural gas, coal and biomass, by the so-called sorption-enhanced reforming (SER) and water gas shift (SEWGS) processes characterized by simultaneous CO₂ capture.     

Promoting effects of CO2 on dehydrogenation of propane over a SiO2-supported Cr2O3 catalyst

The effects of carbon dioxide on the dehydrogenation of C₃H₈ to produce C₃H₆ were investigated over several Cr₂O₃ catalysts supported on Al₂O₃, active carbon and SiO₂. Carbon dioxide exerted promoting effects only on SiO₂-supported Cr₂O₃ catalysts. The promoting effects of carbon dioxide over a Cr₂O₃/SiO₂ catalyst were to enhance the yield of C₃H₆ and to suppress the catalyst deactivation.     

Nanostructured Ca-based sorbents with high CO2 uptake efficiency

Calcium-based carbon dioxide sorbents were made in the gas phase by scalable flame spray pyrolysis (FSP) and compared to the ones made by calcination (CAL) of selected calcium precursors. Such flame-made sorbents consisted of nanostructured CaO and CaCO₃ with twice as much specific surface area (40-60 m²/g) as the CAL-made sorbents. All FSP-made sorbents exhibited faster and higher CO₂ uptake capacity than all CAL-made sorbents at intermediate temperatures. CAL of calcium acetate monohydrate resulted in sorbents with the best CO₂ uptake among all CAL-made ones. At higher temperatures both FSP- and CAL-made sorbents (esp. from CaAc₂·H₂O) exhibited very high initial molar conversions (95%) but sintering contributed to grain growth that reduced the molar conversion down to 50%. In multiple carbonation/decarbonation cycles, the nanostructured FSP-made sorbents demonstrated stable, reversible and high CO₂ uptake capacity sustaining maximum molar conversion at about 50% even after 60 such cycles, indicating high potential for CO₂ uptake. The top performance of flame-made sorbents is best attributed to their nanostructure (30-50 nm grain size) that allows operation in the reaction-controlled carbonation regime rather than in the diffusion-controlled one when sorbents made with larger particles are employed.     

Reducing the Sintering Temperature for MgO–Al2O3Mixtures by Addition of Cryolite (Na3AlF6)

The preparation of near stoichiometric spinel and alumina-rich spinel composites from Al₂O₃and MgO powders with the addition of Na₃AlF₆up to 4 wt% in the temperature range 700°–1600°C was studied; 98 wt% spinel containing 72 wt% Al₂O₃can be produced from the mixture of 72 wt% (50 at.%) Al₂O₃+ 28 wt% (50 at.%) MgO powders with the addition of 1 wt% Na₃AlF₆fired at 1300°C for 1 h. Spinels containing 81–85 wt% Al₂O₃can be produced from either the mixture of 90 wt% (78 at.%) Al₂O₃+ 10 wt% (22 at.%) MgO or the mixture of 95 wt% (88 at.%) Al₂O₃+ 5 wt% (12 at.%) MgO powders with the addition of 4 wt% Na₃AlF₆in the temperature range 1300°–1600°C by using a torch-flame firing for 3 min, followed by quenching in water, while the same system under slow cooling in a furnace results in spinel containing 74–76 wt% Al₂O₃. Microscopic studies indicate that the alumina-rich spinel composites consist of a continuous majority spinel phase and an isolated minority corundum phase, regardless of slow cooling in a furnace or quenching in water.     

Encapsulation of 2-amino-2-methyl-1-propanol with tetraethyl orthosilicate for CO2 capture

Carbon capture is widely recognised as an essential strategy to meet global goals for climate protection. Although various CO₂ capture technologies including absorption, adsorption and membrane exist, they are not yet mature for post-combustion power plants mainly due to high energy penalty. Hence researchers are concentrating on developing non-aqueous solvents like ionic liquids, CO₂-binding organic liquids, nanoparticle hybrid materials and microencapsulated sorbents to minimize the energy consumption for carbon capture. This research aims to develop a novel and efficient approach by encapsulating sorbents to capture CO₂ in a cold environment. The conventional emulsion technique was selected for the microcapsule formulation by using 2-amino-2-methyl-1-propanol (AMP) as the core sorbent and silicon dioxide as the shell. This paper reports the findings on the formulated microcapsules including key formulation parameters, microstructure, size distribution and thermal cycling stability. Furthermore, the effects of microcapsule quality and absorption temperature on the CO₂ loading capacity of the microcapsules were investigated using a self-developed pressure decay method. The preliminary results have shown that the AMP microcapsules are promising to replace conventional sorbents.     

Molecular level understanding of CO2 capture in ionic liquid/polyimide composite membrane

Ionic liquid(IL)/polyimide(PI)composite membranes demonstrate promise for use in CO₂separation applications.However,few studies have focused on the microscopic mechanism of CO₂in these composite systems,which is important information for designing new membranes.In this work,a series of systems of CO₂in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide composited with 4,4-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)-based PI,6FDA-2,3,5,6-tetramethyl-1,4-phenylene-diamine,at different IL concentrations were investigated by all-atom molecular dynamics simulation.The formation of IL regions in PI was found,and the IL regions gradually became continuous channels with increasing IL concentrations.The analysis of the radial distribution functions and hydrogen bond numbers demonstrated that PI had a stronger interaction with cations than anions.However,the hydrogen bonds among PI chains were destroyed by the addition of IL,which was favorable for transporting CO₂.Furthermore,the self-diffusion coefficient and free energy barrier suggested that the diffusion coefficient of CO₂decreased with increasing IL concentrations up to 35 wt-%due to the decrease of the fractional free volume of the composite membrane.However,the CO₂selfdiffusion coefficients increased when the IL contents were higher than 35 wt-%,which was attributed to the formation of continuous IL domain that benefitted the transportation of CO₂.     

CO2甲烷化研究进展

CO_2是造成温室效应的主要气体,作为碳基能源使用的末端形态,CO_2也是种重要的基础碳源。因此,将CO_2转化为能源产品可以快速实现碳的循环,对环境与能源领域意义重大。介绍了CO_2的排放、回收以及资源化利用现状,从催化剂体系、反应机理、合成工艺以及工业化现状等方面系统地介绍了CO_2甲烷化的发展。针对H2供给对CO_2甲烷化应用的限制,分析了电解水制氢再与CO_2进行甲烷化反应的电制气(Pt G)技术的发展现状、工艺路线及其经济性,讨论了该技术在我国应用的可行性。提出随着CO_2捕集与新能源相关技术的发展,Pt G技术会更加成熟,将有望成为未来CO_2资源化利用的重要形式。     

Preparation of nanocrystalline Sr3Al2O6 powders via citric acid precursor

Sr₃Al₂O₆ was synthesized via citric acid precursor. The effects of the molar ratio of citric acid to total metal cations concentration (CA/M) on the formation of Sr₃Al₂O₆ were investigated. Increasing the CA/M promoted the formation of Sr₃Al₂O₆. Single-phase and well-crystallized Sr₃Al₂O₆ was obtained from the CA/M = 1, CA/M = 2 and CA/M = 4 precursor at temperature 1200 °C, 1100 °C and 900 °C, respectively. Differential thermal analysis and thermogravimetric (DTA/TG), X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the precursors and the derived oxide powders. Sr₃Al₂O₆ nanoparticles with a diameter of about 50-70 nm were obtained.     

V2O3/rGO composite as a potential anode material for lithium ion batteries

V₂O₃ is a promising anode material and has attracted the interests of researchers because of its high theoretical capacity of 1070?mAh?g^?1, low discharge potential, inexpensiveness, abundant sources, and environmental friendliness. However, the development and application of V₂O₃ have been hindered by the low conductivity and drastic volume change of V₂O₃ composites. In this work, V₂O₃/reduced graphene oxide (rGO) nanocomposites are successfully prepared through a facile solvothermal method and annealing process. In this synthesis protocol, V₂O₃ nanoparticles (NPs) are encapsulated by rGO. This unique structure enables rGO to inhibit volume changes and improve the ion and electronic conductivity of V₂O₃. In addition, V₂O₃ NPs, which exhibit sizes of 5–40?nm, are uniformly dispersed on rGO sheets without aggregation. The Li⁺ storage behavior of V₂O₃/rGO is systematically investigated in the potential range 0.01–3.0?V. The V₂O₃/rGO nanocomposite can achieve a high reversible specific capacity of 823.4?mAh?g^?1 under the current density of 0.1?A?g^?1, and 407.3 mAh g^?1 under the high current density of 4.0?A?g^?1. The results of this study provide insight into the fabrication of rGO-based functional materials with extensive applications.     

Ca-based sorbent looping combustion for CO2 capture in pilot-scale dual fluidized beds

To demonstrate process feasibility of in situ CO₂ capture from combustion of fossil fuels using Ca-based sorbent looping technology, a flexible atmospheric dual fluidized bed combustion system has been constructed. Both reactors have an ID of 100 mm and can be operated at up to 1000 °C at atmospheric pressure. This paper presents preliminary results for a variety of operating conditions, including sorbent looping rate, flue gas stream volume, CaO/CO₂ ratio and combustion mode for supplying heat to the sorbent regenerator, including oxy-fuel combustion of biomass and coal with flue gas recirculation to achieve high-concentration CO₂ in the off-gas. It is the authors' belief that this study is the first demonstration of this technology using a pilot-scale dual fluidized bed system, with continuous sorbent looping for in situ CO₂ capture, albeit at atmospheric pressure. A multi-cycle test was conducted and a high CO₂ capture efficiency (> 90%) was achieved for the first several cycles, which decreased to a still acceptable level (> 75%) even after more than 25 cycles. The cyclic sorbent was sampled on-line and showed general agreement with the features observed using a lab-scale thermogravimetric analysis (TGA) apparatus. CO₂ capture efficiency decreased with increasing number of sorbent looping cycles as expected, and sorbent attrition was found to be another significant factor to be limiting sorbent performance.