Adiabatic burning velocity of H2–O2 mixtures diluted with CO2/N2/Ar

Global warming due to CO₂ emissions has led to the projection of hydrogen as an important fuel for future. A lot of research has been going on to design combustion appliances for hydrogen as fuel. This has necessitated fundamental research on combustion characteristics of hydrogen fuel. In this work, a combination of experiments and computational simulations was employed to study the effects of diluents (CO₂, N₂, and Ar) on the laminar burning velocity of premixed hydrogen/oxygen flames using the heat flux method. The experiments were conducted to measure laminar burning velocity for a range of equivalence ratios at atmospheric pressure and temperature (300 K) with reactant mixtures containing varying concentrations of CO₂, N₂, and Ar as diluents. Measured burning velocities were compared with computed results obtained from one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics and good agreement was obtained. The effectiveness of diluents in reduction of laminar burning velocity for a given diluent concentration is in the increasing order of argon, nitrogen, carbon dioxide. This may be due to increased capabilities either to quench the reaction zone by increased specific heat or due to reduced transport rates. The lean and stoichiometric H₂/O₂/CO₂ flames with 65% CO₂ dilution exhibited cellular flame structures. Detailed three-dimensional simulation was performed to understand lean H₂/O₂/CO₂ cellular flame structure and cell count from computed flame matched well with the experimental cellular flame.     

O2/CO2和O2/N2氛围下煤粉富氧燃烧数值模拟

在目前煤炭依然作为能源主体的背景下，控制燃煤污染物排放有着重要意义。基于CFD数值模拟，建立伴流燃烧器模型，控制燃料、氧化剂入口流量恒定，设计了O₂/CO₂、O₂/N₂氧化剂氛围中O₂浓度在21%～40%内的多种工况，对煤粉燃烧特性及燃烧产生的污染物进行了研究。分析了不同工况下煤粉燃烧的温度分布、燃烧速率、碳烟、NO_x的生成情况。结果显示，在O₂/CO₂、O₂/N₂两种氧化剂氛围中，随着O₂浓度的上升，煤粉燃烧温度升高、燃烧速率增大，碳烟生成量均增加，同等O2浓度条件下，O₂/CO₂氛围的煤粉燃烧温度和燃烧速率均高于O₂/N₂氛围，碳烟生成量小于O₂/N₂氛围，且O₂/CO₂...     

Oxidative steam reforming of ethanol over Ni/Al2O3 catalysts promoted by CeO2, ZrO2 and CeO2–ZrO2

Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al₂O₃ supports that were either unpromoted or promoted with CeO₂, ZrO₂ and CeO₂–ZrO₂. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO₂ and/or ZrO₂ showed that the variations induced in the Al₂O₃ by the addition of CeO₂ and/or ZrO₂ alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO₂–ZrO₂, improved catalytic activity by increasing the H₂ yield and the CO₂/CO and the H₂/CO values while decreasing coke formation. This results from the addition of ZrO₂ into CeO₂. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products.     

Li2CO3/Na2CO3/K2CO3及其混合熔融盐储热材料热物性分子动力学研究

对Li₂CO₃/Na₂CO₃/K₂CO₃及其二元和三元混合熔融盐的密度、比热容、黏度、热导率进行分子动力学模拟(MD),对比得出模拟结果与现有的实验数据和模拟值相近。结果表明：随着温度的升高,密度逐渐减小,离子之间的距离增加,导致对剪切应力的抵抗力变小,这说明单组分、二元和三元熔融盐黏度的负温度依赖性。对于熔融盐的热导率,单组分和二元熔融盐也呈现出负温度依赖性,而三元熔融盐趋势是随温度的升高呈上升状态。     

O2/CO2/H2O气氛下CO燃烧机理的分子动力学模拟研究

采用反应分子动力学(ReaxFF MD)模拟方法研究了O₂/CO₂/H₂O气氛下CO的燃烧。结果表明：根据化学平衡原理,高浓度CO₂抑制CO的氧化,同时CO₂在高温下参与反应CO₂+H—→CO+OH,进一步抑制CO氧化。在较低温度条件下,较高浓度H₂O的三体效应显著,抑制了CO氧化。另一方面,在较高温度条件下,H₂O参与的H₂O+H—→H₂+OH和H₂O+O—→OH+OH反应占据其化学作用的主导地位,进而促进CO氧化。随着O₂浓度的增加,CO的氧化速度加快。     

O2/N2和O2/CO2气氛下煤半焦-生物质的混燃特性及影响因素

为掌握煤半焦与生物质在O₂/N₂和O₂/CO₂条件下的混燃特性及其影响因素,采用全自动物理化学吸附仪获得了煤半焦-生物质混合燃料的孔隙结构,采用热重实验分析了两种燃料的混燃特性和反应动力学,通过多元线性回归法研究了燃料比、比表面积与混燃特性参数之间的关系。结果表明,O₂/N₂气氛下,掺混生物质可改善煤半焦的着火、燃尽及综合燃烧特性;O₂/CO₂气氛下,掺混生物质能改善煤半焦的着火特性,但会延迟其燃尽。混燃的活化能在低温区和高温区有显著差异,生物质掺混比增大,两个温区的活化能都降低;两种气氛下,低温区的活化能相近,但O₂/CO₂气氛下高温区的活化能显著高于O₂/N₂气氛下的。O₂/N₂气氛下孔隙结构对燃烧特性的影响更显著,而O₂/CO₂气氛下...     

Ag/Al2O3(Li2O)/g-C3N4光催化乙醇制取环氧乙烷

本文制备了一系列Ag/Al₂O₃(Li₂O)/g-C₃N₄复合催化剂,考察了其可见光催化乙醇制取环氧乙烷的性能。Li₂O可调变Al₂O₃表面的酸性,从而降低了主要副产物乙醛的选择性。Ag/Al₂O₃(Li₂O) 在g-C₃N₄上的负载量对产物环氧乙烷的选择性有较大影响,当Ag/Al₂O₃(Li₂O) 负载量为5wt%时,乙醇具有较高的转换率,且环氧乙烷的选择性高达100%。     

稀土固体超强酸SO42-/SnO2-CeO2催化合成生物柴油

以工业棕榈酸和甲醇为原料,采用溶胶-凝胶法制备稀土固体超强酸催化剂SO42-/SnO2-CeO2,催化合成生物柴油。考察了稀土氧化铈添加量、焙烧温度、焙烧时间、硫酸浓度、醇酸质量比、催化剂用量和反应时间对酯化反应的影响。结果表明,当氧化铈添加量为5%时,在2.0 mol/L硫酸浸渍后,于550℃下焙烧3 h制备的催化剂性能最好。正交试验结果表明,合成生物柴油的优化条件为醇酸质量比为15∶25,催化剂用量为棕榈酸质量的4%,反应时间为4 h,在此条件下,酯化率为95.4%。经GC-MS分析,酯产物主要为直链十六烷酸甲酯和10-十八碳烯酸甲酯。     

Thermophysical properties and devitrification of SrO–La2O3–Al2O3–B2O3–SiO2-based glass sealant for solid oxide fuel/electrolyzer cells

Thermal behaviors and stability of glass/glass–ceramic-based sealant materials are critical issues for high temperature solid oxide fuel/electrolyzer cells. To understand the thermophysical properties and devitrification behavior of SrO–La₂O₃–Al₂O₃–B₂O₃–SiO₂ system, glasses were synthesized by quenching (25 − X)SrO–20La₂O₃–(7 + X)Al₂O₃–40B₂O₃–8SiO₂ oxides, where X was varied from 0.0 mol% to 10.0 mol% at 2.5 mol% interval. Thermal properties were characterized by dilatometry and differential scanning calorimetry (DSC). Microstructural studies were performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). All the compositions have a glass transition temperature greater than 620 °C and a crystallization temperature greater than 826 °C. Also, all the glasses have a coefficient of thermal expansion (CTE) between 9.0 × 10⁻⁶ K⁻¹ and 14.5 × 10⁶ K⁻¹ after the first thermal cycle. La₂O₃ and B₂O₃ contribute to glass devitrification by forming crystalline LaBO₃. Al₂O₃ stabilizes the glasses by suppressing devitrification. Significant improvement in devitrification resistance is observed as X increases from 0.0 mol% to 10.0 mol%.     

Reversible hydrogenation/dehydrogenation performances of the Na2LiAlH6–Mg(NH2)2 system

Complex hydrides and Metal–N–H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide–hydride combined system was prepared by ball milling a mixture of Na₂LiAlH₆–Mg(NH₂)₂ in a molar ratio of 1:1.5. The hydrogen storage performances of the Na₂LiAlH₆–1.5Mg(NH₂)₂ system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ∼5.08 wt% of hydrogen, equivalent to 8.65 moles of H atoms, was desorbed from the Na₂LiAlH₆–1.5Mg(NH₂)₂ combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydrogenation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ∼4 moles of H atoms could be reversibly stored in the Na₂LiAlH₆–1.5Mg(NH₂)₂ system perhaps due to the formation of AlN and Mg₃N₂ after dehydrogenation.     

Rh promoted and ZrO2/Al2O3 supported Ni/Co based catalysts: High activity for CO2 reforming,steam–CO2 reforming and oxy–CO2 reforming of CH4

Ni (2.5 wt%) and Co (2.5 wt%) supported over ZrO₂/Al₂O₃ were prepared by following a hydrolytic co-precipitation method. The synthesized catalysts were further promoted by Rh incorporation (0.01–1.00 wt%) and tested for their catalytic performance for dry CO₂ reforming, combined steam–CO₂ reforming and oxy–CO₂ reforming of methane for production of syngas. The catalysts were characterized by using N₂ physical adsorption, XRD, H₂–TPR, SEM, CO₂–TPD, NH₃–TPD, TEM and TGA. The results revealed that ZrO₂ phase was in crystalline form in the catalysts along with amorphous Al oxides. Ni and Co were confirmed to be in their respective spinel phases that were reducible to metallic form at 800 °C under H₂. Ni and Co were well dispersed with their nano-crystalline nature. The catalyst with 0.2% loading of Rh showed superior performance in the studied reactions for reforming of methane. This catalyst also showed good coke resistance ability for dry CO₂ reforming reaction with 3.8 wt% of carbon formation during the reaction as compared to 11.6 wt% carbon formation over the catalyst without Rh. The catalyst performance was stable throughout the reaction time for CH₄ conversions, irrespective of carbon formation with slight decline (～1%) in CO₂ conversion. For dry CO₂ reforming reaction, this catalyst showed good conversion for both CH₄ and CO₂ (67.6% and 71.8% respectively) with a H₂/CO ratio of 0.84, while for the Oxy-CO₂ reforming reaction, the activity was superior with CH₄ and CO₂ conversions (73.7% and 83.8% respectively) and H₂/CO ratio of 1.05.     

All-solid-state lithium secondary batteries with oxide-coated LiCoO2 electrode and Li2S–P2S5 electrolyte

All-solid-state lithium secondary batteries using LiCoO₂ active materials coated with Li₂SiO₃ and SiO₂ oxide films and Li₂S–P₂S₅ solid electrolytes were fabricated and their electrochemical performance was investigated. The electrochemical performace of the all-solid-state cells at a high voltage region was highly improved by using oxide-coated LiCoO₂. The oxide coatings are effective in suppressing the formation of an interfacial resistance between LiCoO₂ and the solid electrolyte at a high cutoff voltage of 4.6 V (vs. Li). As a result, charge–discharge capacities and cycle performance at the cutoff voltage were improved. The cell with Li₂SiO₃-coated LiCoO₂ showed a large initial discharge capacity of 130 mAh g⁻¹ and a good capacity retention of 110 mAh g⁻¹ after 50th cycles at the cutoff voltage of 4.6 V (vs. Li).     

缺陷态Bi2MoO6光热催化CO2和H2O还原成CO的性能

在不同温度下采用乙二醇溶剂热合成法合成Bi₂MoO₆催化剂(BMO-x,x=140、160、180),BMO-160在450℃下煅烧的样品为BMO。用XRD、BET、SEM、EDS、UV-visDRS、XPS、in-situ DRIFTS等表征方法研究其理化特性,建立BMO和BMO-x(x=140、160、180)催化剂的反应性能与孔道结构、材料形貌和缺陷空位的构效关系。结果表明,适宜的溶剂合成温度可以形成更高的孔隙率,调控氧空位的占比,有助于产生更好的催化性能。其中,BMO-160的CO产率更高,这是由于在160℃溶剂热合成温度下制备的样品形貌更优,氧空位占比适中。     

Performance of LaBaCo2O5+δ-Ag with B2O3-Bi2O3-PbO frit composite cathodes for intermediate-temperature solid oxide fuel cells

The composite cathodes LaBaCo₂O_5+δ-x wt.% Ag (LBCO-xAg, x = 20, 30, 40, 50) were prepared by mechanical mixing method for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The experiment results indicated that the addition of a small amount of B₂O₃-Bi₂O₃-PbO (BBP) frit to LBCO-xAg can effectively improve the adhesion and strength of cathode membrane without damaging its porous structure. The BBP frit was proved effective for lowering the sintering temperature of LBCO-xAg to 900 °C. According to the electrochemical impedance spectroscopy and cathodic polarization analysis, the LBCO-30Ag exhibited the best performance and the optimal BBP frit content was 2.5 wt.%. For LBCO-30Ag with 2.5 wt.% BBP frit, the area-specific resistance based on Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte decreased by about 57.6% at 700 °C, 60.5% at 750 °C and 75.9% at 800 °C compared to LBCO, and its cathodic overpotential was 10.7 mV at a current density of 0.2 A cm⁻² at 700 °C, while the corresponding value for LBCO was 51.0 mV. The addition of Ag and BBP frit to LBCO had no significant effect on the thermal expansion.     

O2/CO2气氛下生物质混煤燃烧SO2排放特性的实验研究

在水平管式炉上通过在线烟气分析仪研究了O2/CO2气氛下生物质混合比例、温度、燃烧气氛及氧浓度对生物质混煤SO2排放特性的影响规律。结果表明,O2/CO2气氛下,随着生物质混合比例的增大,生物质混煤SO2释放峰值减小,SO2排放完毕的时间减少,SO2的排放量降低;随着温度的升高,生物质混煤SO2的排放量增加。O2/CO2和O2/N2气氛下随着氧浓度的增大,生物质混煤SO2的排放量均增加。相同氧浓度时,O2/CO2气氛下生物质混煤SO2的排放量略小于O2/N2气氛下的情况,其降低幅度约为5%左右。     

Plasma-reduced Ni/γ–Al2O3 and CeO2–Ni/γ–Al2O3 catalysts for improving dry reforming of propane

Pristine Ni/γ–Al₂O₃ and CeO₂–Ni/γ–Al₂O₃ catalysts were prepared by co-impregnation technique for dry reforming of propane. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to examine the structure and morphology of the catalysts before and after the reforming reactions. The excellent interaction between catalyst active phases was observed in both CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃ stabilized with polyethelene glycol (Ni/γ–Al₂O₃–PEG). Towards C₃H₈ and CO₂ conversion, the CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃–PEG showed improved catalytic activity when compared to the pristine Ni/γ–Al₂O₃ catalyst. Interestingly, high H₂ concentration was achieved with the CeO₂–Ni/γ–Al₂O₃ and high CO concentration with the Ni/γ–Al₂O₃–PEG, which is due to the nanoconfinement of nickel particles within the support and favorable metal-support interaction as a result of plasma reduction. The CeO₂–Ni/γ–Al₂O₃ catalyst exhibited better stability for anti-sintering and coke resistance, thus exhibiting high reactivity and durability in the dry reforming.     

Syngas production by CO2 reforming of coke oven gas over Ni/La2O3–ZrO2 catalysts

Syngas production by CO₂ reforming of coke oven gas (COG) was studied in a fixed-bed reactor over Ni/La₂O₃–ZrO₂ catalysts. The catalysts were prepared by sol–gel technique and tested by XRF, BET, XRD, H₂-TPR, TEM and TG–DSC. The influence of nickel loadings and calcination temperature of the catalysts on reforming reaction was measured. The characterization results revealed that all of the catalysts present excellent resistance to coking. The catalyst with appropriate nickel content and calcination temperature has better dispersion of active metal and higher conversion. It is found that the Ni/La₂O₃–ZrO₂ catalyst with 10 wt% nickel loading provides the best catalytic activity with the conversions of CH₄ and CO₂ both more than 95% at 800 °C under the atmospheric pressure. The Ni/La₂O₃–ZrO₂ catalysts show excellent catalytic performance and anti-carbon property, which will be of great prospects for catalytic CO₂ reforming of COG in the future.     

Methane dry reforming on Ni/Ce0.75Zr0.25O2–MgAl2O4 and Ni/Ce0.75Zr0.25O2–γ-alumina: Effects of support composition and water addition

Nickel catalysts (10wt.%) supported on MgAl₂O₄ and γ-Al₂O₃ were prepared by the wet impregnation method and promoted with various contents of Ce_0.75Zr_0.25O₂. X-ray diffraction (XRD), BET surface area, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), H₂-temperature programmed reduction (TPR) and CO₂-temperature programmed desorption (TPD) were employed to observe the characteristics of the prepared catalysts. Ni/γ-Al₂O₃ and Ni/Ce_0.75Zr_0.25O₂ (5wt.%)–MgAl₂O₄ showed better activity in CO₂ methane reforming with 75.7(0.93) and 75.4(0.82) CH₄ conversions (and H₂/CO ratio). H₂O was added to feed in the range of H₂O/(CH₄ + CO₂): 0.1–0.5 to suppress reverse water gas shift (RWGS) effect and adjusting H₂/CO ratio. The CH₄ conversions (and H₂/CO) increased to 81(1.1) with 0.5 water/carbon mole ratio in Ni/γ-Al₂O₃ and 85(1.2) with 0.2 water/carbon mole ratio in Ni/Ce_0.75Zr_0.25O₂ (5wt.%)–MgAl₂O₄. The stability of Ni/Ce_0.75Zr_0.25O₂ (5wt.%)–MgAl₂O₄ in the presence and absence of water was investigated. Coke formation and amount in used catalysts were examined by SEM and TGA, respectively. The results showed that the amount of carbon was suppressed and negligible coke formation (less than 3%) was observed in the presence of 0.2 water/carbon mole ratio over Ni/Ce_0.75Zr_0.25O₂ (5wt.%)–MgAl₂O₄ catalyst.     

Hydrogen production by biomass gasification in supercritical water over Ni/γAl2O3 and Ni/CeO2-γAl2O3 catalysts

Hydrogen production by supercritical water gasification (SCWG) is a promising technology for wet biomass utilization. Ni catalyst can realize the high gasification efficiency of biomass near the critical temperature of water. In this paper, Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts were prepared by an impregnation method. The catalyst performance for glucose gasification in supercritical water was tested in autoclave reactor. All experiments were carried out in the autoclave at 673 K, 24.5 MPa, and the concentration of glucose was 9.09 wt.%. The catalysts before and after reaction were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurements, X-ray fluorescence spectrum (XRF) and Thermo-gravimetric analyses (TGA) in order to investigate on the chemical property and catalytic mechanism. The experimental results showed that hydrogen yield and hydrogen selectivity increased sharply with addition of Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts. The catalytic activity and H₂ selectivity of Ni/CeO₂-γAl₂O₃ was higher than that of Ni/γ-Al₂O₃ catalyst. The results revealed that carbon deposition and coking led to the deactivation of the catalysts. Ce in the Ni/CeO₂-γAl₂O₃ catalyst had a certain role in the inhibition of carbon deposition and coking.