电流对苯甲醚电催化重整过程的影响

用电催化重整方法和NiCuZn-Al₂O₃催化剂进行生物油模型化合物苯甲醚的水蒸气重整制氢研究,结果表明,在700 oC和4 A条件下,获得的最高碳转化率和氢产率分别为98.3%和88.7%,电催化重整过程中发现的电流促进效应主要归结于重整反应床中温度分布的改变和电阻丝发射的热电子影响. 利用X射线衍射方法分析了反应前后的NiCuZn-Al₂O₃催化剂结构变化. 实验导出的苯甲醚重整反应表观活化能为99.54 kJ/mol,明显高于乙醇、乙酸和生物油轻质组分的重整反应表观活化能.     

Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

利用沉积沉淀法制备出了La改性Al₂O₃催化剂,研究不同焙烧温度对La改性Al₂O₃催化剂用于乙炔气相氢氟化合成氟乙烯反应性能的影响．利用NH₃-TPD、Pyridine-FTIR、XRD和Raman等技术对不同温度焙烧的催化剂进行表征,发现焙烧过程能改变催化剂结构的同时也能调变催化剂表面的酸量．经400 °C焙烧的催化剂显示出最高的乙炔转化率(94.6%)、最高的氟乙烯选择性(83.4%)和较低的积炭选择性(0.72%)．催化剂的高活性与其表面的高酸量有关,同时积炭的选择性也与其表面的酸中心数量有关．     

双金属镍-锰/γ-Al2O3催化剂对甲烷二氧化碳重整反应的影响 (cited: 1)

用浸渍法制备γ-Al₂O₃负载的Ni-Mn双金属催化剂．在500～700 oC按照17:17:2的CO₂/CH₄/N₂比例,以36 mL/min的载气流速进行甲烷二氧化碳重整反应, 利用甲烷二氧化碳的转化率、生成的合成气H₂/CO比例以及长期稳定性等指标评价了催化剂的催化性能． 实验表明, 添加Mn提高催化性能并使双金属催化剂的稳定性更高, 比单金属催化剂更好地抑制焦炭生成,Mn最合适的添加量0.5wt％ ．通过BET、CO2-TPD、TGA、XRD、SEM、EDX和FTIR各种技术对催化剂进行了表征．     

纤维状TiO2/Bi2O3光催化剂的制备及其光催化性能

以C₁₆H₃₆O₄Ti和Bi(NO₃)·5H₂O为原料,以棉花纤维为生物模板,合成了系列纤维状TiO₂/Bi₂O₃光催化剂．采用XRD、SEM、UV-Vis等测试技术对样品的相结构、形貌和吸光性能等进行了表征分析．结果表明,样品中的Bi₂O₃为单斜相和四方相共存的混晶,纤维长度达到毫米级,     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

有机金属化学气相沉积法制备的Ni/Al2O3纳米复合材料的氢吸附

研究了通过有机金属化学气相沉积技术及单源分子前躯体方法制备的Ni/Al₂O₃纳米复合材料的氢吸附(存储). 在冷壁的有机金属化学气相沉积反应器中,通过降解Ni(acac)₂粉末基底上的[H₂Al(OtBu)]₂制备的Ni/Al₂O₃纳米复合材料. 通过X射线粉末衍射、扫描电镜、透射电镜以及能量色散型X射线荧光光谱等技术表征该复合材料. 采用自制Sievert's设备研究该复合材料的氢吸附(存储),可以储存约2.9%(重量比)的氢.     

体光源模拟标定法测O2(1Δ)绝对浓度

 O₂(¹Δ)绝对浓度的测量,一直是SOG和COIL研究中的重要参数之一。体光源模拟标定法测O₂(¹Δ)绝对浓度,是把发光气体以某一流速引入一已知体积的流动光池中,再通过具有低象差失真的光学系统,把该体光源成象在探测器的有效表面上。探测器和测量仪器组成的测量系统,要经过标准光源和电学标定。本方法可测出O₂(¹Δ绝对浓度和其分压,O₂(¹Δ)产率等参数。其中O₂(¹Δ)浓度测量结果的相对误差为20%。     

Reaction of C2HCl2+O2: Combined TR-FTIR Spectroscopy and Electronic Structure

用时间分辨傅立叶变换红外发射光谱(TR-FTIR)和G3MP2//B3LYP/6-311G(d,p)水平的电子结构计算研究了环境化学中重要的二氯代乙烯自由基C₂HCl₂和O₂分子的基元反应通道和机理. 通过0.5 cm^-1高分辨的TR-FTIR发射光谱观察到三种振动激发态产物CO₂、CO和HCl,由光谱拟合得到CO和HCl的振动态分布,结合电子结构计算的反应势能曲线,提出反应机理和能量上最可能的反     

Superacid Catalyst SO42-/ZrO2-La2O3 Prepared by Ultrasonic Co-precipitation and Low Temperature Aging

低温陈化超声波共沉淀法制得SO₄^2-/ZrO^2-La₂O₃前驱体, 经H₂SO₄处理, 在不同温度下焙烧得到纳米晶催化剂SO₄^2-/ZrO^2-La₂O₃;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性.     

使用金属掺杂SnO2(110)作为表面催化剂的电催化CO2还原反应：通过调控Sn:O原子比例来控制产物

电催化CO₂还原反应可以产生HCOOH和CO,目前该反应是将可再生电力转化为化学能存储在燃料中的最有前景的方法之一. SnO₂作为将CO₂转换为HCOOH和CO的良好催化剂,其反应发生的晶面可以是不同的. 其中(110)面的SnO₂非常稳定,易于合成. 通过改变SnO₂(110)的Sn:O原子比例,得到了两种典型的SnO₂薄膜：完全氧化型(符合化学计量)和部分还原型. 本文研究了不同金属(Fe、Co、Ni、Cu、Ru、Rh、Pd、Ag、Os、Ir、Pt和Au)掺杂的SnO₂(110),发现在CO₂还原反应中这些材料的催化活性和选择性是不同的. 所有这些变化都可以通过调控(110)表面中Sn:O原子的比例来控制. 结果表明,化学计量型和部分还原型Cu/Ag掺杂的SnO₂(110)对CO₂还原反应具有不同的选择性. 具体而言,化学计量型的Cu/Ag掺杂的SnO₂(110)倾向于产生CO(g),而部分还原型的表面倾向于产生HCOOH(g). 此外,本文还考虑了CO₂还原的竞争析氢反应. 其中Ru、Rh、Pd、Os、Ir和Pt掺杂的SnO₂(110)催化剂对析氢反应具有较高的活性,其他催化剂对CO₂还原反应具有良好的催化作用.     

含氧有机物催化重整制备纯氢

研究了一种新的利用含氧化合物制备纯氢的催化变换过程,该过程耦合了含氧化合物的催化重整、水煤气变换反应和CO₂去除步骤. 详细研究了重整催化剂的筛选、反应条件以及不同的含氧化合物催化重整行为. 利用所述集成方法获得的最高氢气浓度为99.96vol%和最大转化率为97.1mol%. 此外,通过含氧化合物的解离、催化重整和水煤气变换反应研究,探讨了含氧化合物制备纯氢的相关反应路径.     

On the reaction mechanism of CO2 reforming of methane over a bed of coal char

CO₂ reforming of methane was studied over a bed of coal char in a fixed bed reactor at temperatures between 1073 and 1223 K and atmospheric pressure with a feed composition of CH₄/CO₂/N₂ in the ratio of 1:1:8. Experimental results showed that the char was an effective catalyst for the production of syngas with a maximum H₂/CO ratio of one. It was also found that high H₂/CO ratios were favoured by low pressures and moderate to high temperatures. These results are supported by thermodynamic calculations. A mechanism of seven overall reactions was studied and three catalytic reactions of CH₄ decomposition, char gasification and the Boudouard reaction was identified as being of major importance. The first reaction produces carbon and H₂, the second consumes carbon, and the third (the Boudouard reaction) converts CO₂ to CO while consuming carbon. Equilibrium calculations and experimental results showed that any water present reacts to form H₂ and carbon oxides in the range of temperatures and pressures studied. Carbon deposition over the char bed is the major cause of deactivation. The rate of carbon formation depends on the kinetic balance between the surface reaction of the adsorbed hydrocarbons with oxygen containing species and the further dissociation of the hydrocarbon.     

Characterization of ZrO2-promoted Cu/ZnO/nano-Al2O3 methanol steam reforming catalysts

Three Cu/ZnO/ZrO₂/Al₂O₃ methanol reforming catalysts were investigated using X-ray photoelectron spectroscopy (XPS). The catalysts which contained ZrO₂ from a monoclinic nanoparticle ZrO₂ precursor exhibit both a higher activity toward the methanol steam reforming reaction and a lower CO production rate compared to catalysts composed of an XRD-amorphous ZrO₂ produced by impregnation using a Zr(NO₃)₂ precursor. The presence of a monoclinic phase appears to result in an increased charge transfer between the Zr and Cu species, as evidenced by a relatively electron-rich ZrO₂ phase and a partially oxidized Cu species on reduced catalysts. This electron deficient Cu species is more reactive toward the methanol reforming reaction and partially suppresses CO formation through the reverse water gas shift or methanol decomposition reactions.     

Insight into the reaction mechanism of ethanol steam reforming catalysed by Co–Mo6S8

The production of hydrogen via steam reforming of ethanol (SRE) is favourable for the use of hydrogen as an alternative fuel. Co–Mo₆S₈ possesses high activity and stability for SRE to sustainably produce hydrogen. The competition among reaction pathways related to C–H, O–H, C–C, C–O cleavage and H₂ formation was studied. The adsorption and reaction of related intermediates in the ESR reaction pathway are described. The results indicated that the most feasible route for the decomposition of ethanol catalysed by Co–Mo₆S₈ is CH₃CH₂OH*→CH₃CH₂O*→CH₃CHO*→CH₂CHO*→CHCHO*→CHCO*→CH*+CO*. The CH* can be decomposed into C*+H*, and CO* can be oxidised via the redox mechanism of the water gas shift (WGS) reaction. Thus the final products are CO₂ and H₂. The present result may help people to design an SRE catalyst, which has the ability to break C–C to form CO and H₂, then CO react with H₂O in the WGS reaction generating CO₂ and H₂.     

Effect of CO2 gasification reaction on oxy-combustion of pulverized coal char

For oxy-combustion with flue gas recirculation, as is commonly employed, it is recognized that elevated CO₂ levels affect radiant transport, the heat capacity of the gas, and other gas transport properties. A topic of widespread speculation has concerned the effect of the CO₂ gasification reaction with coal char on the char burning rate. To give clarity to the likely impact of this reaction on the oxy-fuel combustion of pulverized coal char, the Surface Kinetics in Porous Particles (SKIPPY) code was employed for a range of potential CO₂ reaction rates for a high-volatile bituminous coal char particle (130 μm diameter) reacting in several O₂ concentration environments. The effects of boundary layer chemistry are also examined in this analysis. Under oxygen-enriched conditions, boundary layer reactions (converting CO to CO₂, with concomitant heat release) are shown to increase the char particle temperature and burning rate, while decreasing the O₂ concentration at the particle surface. The CO₂ gasification reaction acts to reduce the char particle temperature (because of the reaction endothermicity) and thereby reduces the rate of char oxidation. Interestingly, the presence of the CO₂ gasification reaction increases the char conversion rate for combustion at low O₂ concentrations, but decreases char conversion for combustion at high O₂ concentrations. These calculations give new insight into the complexity of the effects from the CO₂ gasification reaction and should help improve the understanding of experimentally measured oxy-fuel char combustion and burnout trends in the literature.     

Surface chemistry and catalytic activity of Ni/Al2O3 irradiated with high-energy electron beam

The radiation effects induced effects by electron beam (EB) treatment on the catalytic activity of Ni/γ-Al₂O₃ were studied for the carbon dioxide reforming of methane with different EB energy and absorbed radiation dose. Transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to determine the change in structure and surface states of Ni/γ-Al₂O₃ catalyst before and after the EB treatment. Higher energy EB treatment is useful for increasing the proportion of the active sites (such as Ni⁰ and NiAl₂O₄-phase) on the surface. The increase of Ni/Al-ratio indicates that the Ni dispersion on the surface increased with the EB-treatment, resulting in an increase of the active sites, which leads to improving the catalytic activity. XPS measurement also showed a decrease of the surface carbon with EB dose. The maximum 20% increase in the conversion of CO₂/CH₄-mixture into CO/H₂ gas was observed for the catalyst treated with 2 MeV energy and 600 kGy dose of EB relative to untreated.     

Pyrolysis of sewage sludge under conditions relevant to applied smouldering combustion

Pyrolysis of sewage sludge under conditions relevant to applied smouldering combustion was carried out in this study to investigate the influences of gas flow rate, oxidative atmosphere, and inert porous medium involvement on the properties of products. The experiments were carried out at 300–600 °C under atmospheres of N₂, 5% O₂/95% N₂, 10% O₂/90% N₂, and 15% O₂/85% N₂, with Darcy flow rates of 1.0 and 3.5 cm/s, respectively, with dried sewage sludge loaded individually or as a mixture with sand. As a result, both the increment of gas flow rate and involvement of sand leaded to lower yields of char and higher yields of bio-oil and gas under N₂ at temperature of ≤500 °C, due to the enhanced efficiency of pyrolysis reaction and gas transportation. However, when temperature increased to 600 °C, the influencing trends on product distributions changed due to the mechanisms of secondary cracking reaction and volatile-char interaction. The involvement of oxygen in fraction of ≤15 vol% at temperatures of 400–500 °C would lead to the intense decreasing yields of char and bio-oil, and increasing yield of the gaseous (dominated by CO₂ and CO), due to the involved oxidation reaction during pyrolysis. Both increment of temperature and oxygen fraction would lead to the delay of ignition and the increase of activation energy of the produced char, except for that of char produced at 400 °C under 5% O₂/95% N₂, whose calculated activation energy was lower and volatile content was higher compared to that of char produced from pyrolysis at 400 °C under N₂. The bio-oil from pyrolysis under N₂ was dominated by aliphatic acids, phenols, steroids, amides, and indoles, etc., and the involvement of partial oxidation would lead to the weakened formation of aromatics, phenols, and S/Cl/F-containing compounds in bio-oil.     

Catalytic effect of water,water dimer,water trimer,HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2 on the isomerisation of HN(NO2)2 to O2NNN(O)OH: a mechanism study

In this article, the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH without and with catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄ and CH₃CH₂COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H₂O, (H₂O)₂ and (H₂O)₃)-assisted transition states, as well as different values of pK_a for H₂SO₄, HCOOH and CH₃CH₂COOH. Very interesting is also the fact that H₂SO₄-assisted reaction is the most favourable for the hydrogen transfer from HN(NO₂)₂ to O₂NNN(O)OH, due to the smallest pK_a (?3.0) value of H₂SO₄ than H₂O, HCOOH, H₂SO₄ and CH₃CH₂COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H₂SO₄-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH, the apparent activation energy of H₂SO₄-assisted channel also reduces by 9.6 kcal?mol^?1, indicating that H₂SO₄ can affect the isomerisation of HN(NO₂)₂ to O₂NNN(O)OH, most obvious among all the catalysts H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂.     

Effect of gasification reactions on biomass char conversion under pulverized fuel combustion conditions

The effect of gasification reactions on biomass char conversion under pulverized fuel combustion conditions was studied by single particle experiments and modelling. Experiments of pine and beech wood char conversion were carried out in a single particle combustor under conditions of 1473-1723 K, 0.0-10.5% O₂, and 25-42% H₂O. A comprehensive progressive char conversion model, including heterogeneous reactions (char oxidation and char gasification with CO₂ and H₂O), homogeneous reactions (CO oxidation, water-gas shift reaction, and H₂ oxidation) in the particle boundary layer, particle shrinkage, and external and internal heat and mass transfer, was developed. The modelling results are in good agreement with both experimental char conversion time and particle size evolution in the presence of oxygen, while larger deviations are found for the gasification experiments. The modelling results show that the char oxidation is limited by mass transfer, while the char gasification is controlled by both mass transfer and gasification kinetics at the investigated conditions. A sensitivity analysis shows that the CO oxidation in the boundary layer and the gasification kinetics influence significantly the char conversion time, while the water-gas shift reaction and H₂ oxidation have only a small effect. Analysis of the sensitive parameters on the char conversion process under a typical pulverized biomass combustion condition (4% O₂, 13% CO₂, 13% H₂O), shows that the char gasification reactions contribute significantly to char conversion, especially for millimeter-sized biomass char particles at high temperatures.