CO2与水蒸汽对焦炭溶损反应的影响

采用自制气-固相反应测定仪,于950~1200℃温度范围内研究了焦炭与CO2、水蒸汽的溶损反应. 结果表明,焦炭与水蒸汽反应的气化率约为与CO2反应的2~7倍,随温度升高,二者气化率差距缩小;焦炭与CO2或水蒸汽的反应过程受界面反应控制较明显,可用未反应收缩核模型描述,反应的活化能分别为165.48和82.25 kJ/mol;随温度升高,焦炭颗粒由外到内溶损量呈减少趋势,焦炭与水蒸汽反应比与CO2反应更多发生在颗粒表面;不同部位气孔生成方式不同,焦炭与CO2、水蒸汽反应后,边缘部位大于10 mm的气孔所占比例分别增加66.98%和94.01%,中心部位大于10 mm的气孔所占比例分别降低21.22%和3.30%.     

富钙废渣配煤对焦炭溶损反应的影响

将1%富钙碱渣配入焦煤中制备焦炭,采用自制小型垂直固定床反应器研究了900~1200℃下所得焦炭的溶损反应过程. 结果表明,碳素溶损率小于15%时焦炭的溶损反应速率基本不变,碳素溶损率大于15%时溶损反应速率逐渐减小. 焦炭反应后的比表面积随碳素溶损率增加先增大后减小,在溶损率约为15%时最大. 配入富钙碱渣提高了焦炭的溶损反应速率,增大了焦炭的反应性,溶损温度越高,溶损速率增幅越大. 用随机孔模型描述了焦炭的溶损反应动力学过程,基础焦炭和添加1%碱渣的焦炭的溶损反应表观活化能分别为132.15和103.81 kJ/mol.     

基于Aspen plus对气流床以CO_2制高浓度CO能力的研究

借助Aspen plus软件,在进料粉煤10 kg/h、氧气流量6. 3 kg/h、CO2与水蒸气流量1. 5 kg/h、气化压力3. 5 MPa、温度1 450℃的反应条件下,对添加CO2部分替代水蒸气气流床粉煤气化反应的性能进行探究,结果表明CO2/H2O质量比为0. 4时,固定床生产工艺比较发现:合成气总产量、(CO+H2)浓度、CO浓度以及CO2比耗在相同条件下比固定床工艺平均分别高出2. 147 Nm3/h、12. 44%、4. 55%和92. 582 Nm3/k Nm3(CO+H2)     

灰分对焦炭溶损反应起始温度的影响

通过灰分添加实验得到不同灰分含量的焦炭,研究了灰分对焦炭溶损反应起始温度的影响。随着灰分的增加,焦炭的溶损反应起始温度逐渐降低,焦炭灰分由1.63%增加至20%时,溶损反应起始温度由941.6℃降低至927.7℃;Fe2O3、Ca O、Mg O对焦炭溶损反应起催化作用,而Si O2和Al2O3对焦炭溶损反应的影响较小。     

酒糟与煤焦在CO2气氛下的共气化特性

利用固定床反应器研究了酒糟和煤焦在CO2气氛下的共气化特性,考察了实验样品的孔隙结构、表面元素组成及灰分矿物组成. 结果表明,酒糟和煤焦在CO2气氛下共气化过程中存在协同作用,产气中除CO2外,主要产生CO, H2和CH4气体,且在酒糟掺混比例为80%时浓度最高. 气化反应温度和酒糟掺混比例是影响共气化反应的主要因素,酒糟掺混比例相同时,900?1100℃范围内随温度升高,共气化反应活性提高;温度相同时,20%?80%范围内随酒糟掺混比例增加,共气化反应活性增大. 酒糟含69.47%挥发分,且在气化过程中产生大量孔隙及酒糟和煤焦中分别含K和Ca元素对共气化反应起催化作用,是共气化反应活性提高的主要原因.     

BaO对焦炭溶损反应的催化作用机理

提出的焦炭溶损反应模型中,认为焦炭与CO2反应时,边缘碳原子由于存在未配对的sp2电子易发生化学吸附氧,形成平面半醌型含氧络合物Cf(O)和非平面型含氧络合物C(O)Cf(O).由于含氧络合物的生成,使与含氧基团相连的C-C削弱而断裂,络合物分解形成反应产物,即溶损反应发生在碳网的边缘.BaO催化焦炭溶损反应模型中,认为CO2首先和催化剂结合,释放出活性Ba@O,随着Ba@O的分散,Ba@O和焦炭表面的活性炭原子结合生成两种类型含氧中间产物,平面半醌型含氧络合物Cf(Ba@O)和非平面含氧络合物C(Ba@O)Cf(Ba@O),催化溶损反应速率依赖于中间产物中与Cf(Ba@O)相连的C-C键的断裂而分解的速度.在此基础上导出了催化反应动力学方程.     

Nd（C2H5CO2）3·H2O热分解性质的研究

用热重分析(TG),差热分析(DTA),傅里叶红外光谱分析(FTIR)和X射线衍射(XRD)等方法研究了Nd(C2H5CO2)3.H2O的热分解性质。在流动的Ar气中加热到1200℃,水合丙酸钕的分解可以分成6个步骤。在经过脱水反应之后,Nd(C2H5CO2)3首先在250℃和292℃之间生成Nd2(C2H5CO2)4.CO3并释放出二乙基甲酮。当温度升高到315℃,伴随着CO2气体的放出,Nd(C2H5CO2)3立即分解成Nd2O(C2H5CO2)4。在424℃之前,伴随着二乙基甲酮和CO2气体产生,Nd2O(C2H5CO2)4首先分解成中间相Nd2O(CO3)2,并立即转化成分解产物Nd2O2CO3。随着温度升高到770℃,含Nd化合物完全转化成Nd2O3。研究表明,Nd(C2H5CO2)3.H2O在空气中的TG曲线和其在Ar气中的没有任何改变。但是,分解产物二乙基甲酮气体在空气中的燃烧会产生很强的放热效应。与其它稀土金属丙酸盐的热分解的研究结果比较而言,Nd(C2H5CO2)3.H2O的分解性质表现出一些有趣的特点。特别是,在其它丙酸盐中没有发现类似中间相Nd2(C2H5CO2)4.CO3的生成的情况。     

利用CO-CO2-H2混合气体生产碳化铁的实验研究

通过热力学计算,讨论了利用CO-CO2-H2混合气体生产碳化铁的可行性,并在实验室小型流化床反应器内使用CO-CO2-H2混合气体进行铁矿石还原实验,分别讨论了反应温度、系统压力、H2含量、CO/CO2比值等因素对碳化铁生成的影响. 扩大化的公斤级流化床实验表明,当反应时间为150 min时,铁矿石还原度超过95%,反应时间180 min时碳化铁率达到90%左右.     

钢渣基高反应性焦炭气孔结构的溶损演化行为

在工业配合煤中添加1%钢渣制备高反应性焦炭,采用低温氮气吸附法分析高反应性焦炭（HRC）和普通焦炭（BC）在1100℃下溶损不同比率碳素（5%~50%）后焦炭的气孔结构,并结合分形理论研究焦炭溶损反应过程中孔结构的演化特性。结果表明,随着碳素的溶损,HRC的吸脱附曲线的变化幅度比BC的大,吸附等温线由Ⅰ型向Ⅱ型的转变较晚;焦炭的比表面积和微孔孔容随碳素的溶损先增大后减小、总孔容逐渐增大,而HRC的比表面积增率（ΔS _BET /Δx）比BC的大,孔径分布也相对较宽;HRC的分形维数D ₁和D ₂随碳素溶损而变化趋势与BC的有较大差异。这说明高反应性焦炭中的钢渣通过增加了焦炭表面上活性点影响焦炭溶损过程中气孔结构的演化行为。     

双流化床生物质气化动力学建模与分析

为进一步研究双流化床生物质气化器中合成气含量分布,将气化器鼓泡床层分为气泡相和乳化相,依据动力学反应分别进行各相质量和热量衡算,计算结果与实验值吻合较好. 随气化温度升高,CO含量增加,而H2和CO2含量降低;蒸汽与生物质质量比(S/B)增加促进水蒸汽变换和重整反应,消耗CO和CH4,生成H2和CO2,当S/B从0变化到1.2时,CO/H2变化44%,说明S/B增加主要促进了水蒸汽变换反应. 气化温度870℃及S/B=0.75条件下,当气化器高度为0~0.5 m时,H2O含量急剧下降,H2含量急剧上升,CO与CO2含量逐渐上升,当该高度大于0.5 m后,气化反应基本完成.     

Crystallization of zeolite L from Na2O-K2O-Al2O3-SiO2-H2O system

Zeolite L powder was prepared from the substrate mixture of Na₂O-K₂O-Al₂O₃-SiO₂-H₂O system at temperatures of 373-443 K. In order to investigate the factors which influence the synthesis outcome, a reference system which yields zeolite L in a reproducible manner was chosen and subjected to controlled changes in synthesis parameters. The crystalline zeolite L samples obtained were characterized by elemental chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was established that phase purity, morphology, and the size of crystals of crystalline product were affected by molar ratios of the substrate, such as SiO₂/Al₂O₃, (K₂O+Na₂O)/SiO₂, Na₂O/(K₂O+Na₂O), and H₂O/(K₂O+Na₂O). Amorphous silica powder (Zeosil) was the preferred silica source, and the crystallization rate was promoted by introducing gel aging, seeding, and rapid heating rate.     

Photocatalytic activity of Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions

Cu₂O/TiO₂, Bi₂O₃/TiO₂ and ZnMn₂O₄/TiO₂ heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu₂O, Bi₂O₃ and ZnMn₂O₄ are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu₂O/TiO₂ and Bi₂O₃/TiO₂ by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed.     

碳酸钠—过氧化氢—水体系相图的绘制

进行了Na2CO3-H2O2-H2O体系溶解度的测定并绘制成相图,最后对其应用进行了讨论。     

Synthesis and characterization of Y2O3-ZrO2 and Y2O3-CeO2-ZrO2 precursor powders

Thixotropic gels of the precursor powders of the titled compounds have been prepared by the addition of oxalic acid to the mixed solutions of metal salts at room temperature (≈ 27 °C). The clear sols of yttrium-zirconyl oxalate (YZO) and yttrium-cerium-zirconyl oxalate (YCZO) gelled within a few hours and were oven-dried at 40 °C. The various stages of gelation behaviour of the sols are explained on the basis of DLVO theory. By repeptizing the dried gel powders with water, concentrated sols were prepared. The gelation time as a function of chloride ion concentration is discussed for both sols. The nature of the temperature dependence of the dried gel powders was studied by means of thermogravimetric analysis and differential thermal analysis. Powder X-ray diffraction was used to study the crystallization behaviour of the dried amorphous gel powders. It is found that these powders crystallize in tetragonal phase when calcined at 850 °C for 1 h. Estimation of surface area and infra-red characterization have also been carried out for the prepared powders.     

Stable Ti/RuO2-Sb2O5-SnO2 electrodes for O2 evolution

RuO₂-based electrodes are generally known to be unstable for O₂ evolution. In this paper, a stable type of RuO₂-based electrode, Ti/RuO₂-Sb₂O₅-SnO₂, is demonstrated for O₂ evolution. In the ternary oxide coating, RuO₂ serves as the catalyst, SnO₂ as the dispersing agent, and Sb₂O₅ as the dopant. The accelerated life test showed that the Ti/RuO₂-Sb₂O₅-SnO₂ electrode containing 12.2 molar percent of RuO₂ nominally in the coating had a service life of 307 h in 3 M H₂SO₄ solution under a current density of 0.5 A cm⁻² at 25 °C, which is more than 15 times longer than other types of RuO₂-based electrodes. Instrumental analysis indicated that RuO₂-Sb₂O₅-SnO₂ was a solid solution with a compact structure, which contributed to the stable nature of the electrode.     

Preparation and characterization of Cr2O3-TiO2-Al2O3-V2O5 green pigment

Green pigments with high near infrared reflectance based on a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition have been synthesized. Cr₂O₃ was used as the host component and mixtures of TiO₂, Al₂O₃ and V₂O₅ were used as the guest components. TiO₂, Al₂O₃, and V₂O₅ were mixed into 39 different compositions. The spectral reflectance and the distribution of pigment powder were determined using a spectrophotometer and a scanning electron microscope, respectively. It was found that a pigment powder sample S9 with a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition of 80, 4, 14 and 2 wt%, respectively, gives a maximum near infrared solar reflectance of 82.8% compared with 49.0% for pure Cr₂O₃. The dispersion of pigment powders in a ceramic glaze was also studied. The results show that the pigment powder sample S9 is suitable for use as a coating material for ceramic-based roofs.     

Crystal Structure of the LiNaZnP2O7 Compound in the Li2ZnP2O7-Na2ZnP2O7 Glass-Forming System

The crystal structure of the LiNaZnP₂O₇ compound is determined using X-ray powder diffraction (space group Cmcm, a = 12.431 Å, b = 7.589 Å, c = 6.283 Å). The structure has a mixed tetrahedral framework consisting of the diortho groups [P₂O₇] and the tetrahedra [ZnO₄] and [LiO₄], which are joined into chains. The [ZnO₄] and [LiO₄] tetrahedra are distributed in the chains in a random manner, because the zinc and lithium atoms statistically occupy one crystallographic position. The sodium cations are arranged in channels of the tetrahedral framework. The atomic coordinates and interatomic distances in the structure are reported. Original Russian Text Copyright ? 2005 by Fizika i Khimiya Stekla, Shepelev, Lapshin, Petrova, Novikova.     

Al2O3-SiO2-TiO2一ZrO2复合陶瓷膜的制备与表征

采用Sol—Gel法制备出掺杂SiO2，TiO2及ZrO2改性的γ-Al2O3膜，并通过SEM，EPMA，AFM等测试手段对膜结构和性能进行表征。探讨了制膜工艺条件对膜性能及结构的影响。制备的Al2O3复合膜膜厚为1—2μm，结构均匀无缺陷。     

ZrO2/SiO2- and La2O3/Al2O3-supported platinum catalysts for CH4/CO2 reforming

Surface-phase ZrO₂ on SiO₂ (SZrOs) and surface-phase La₂O₃ on Al₂O₃ (SLaOs) were prepared with various loadings of ZrO₂ and La₂O₃, characterized and used as supports for preparing Pt/SZrOs and Pt/SLaOs catalysts. CH₄/CO₂ reforming over the Pt/SZrOs and Pt/SLaOs catalysts was examined and compared with Pt/Al₂O₃ and Pt/SiO₂ catalysts. CO₂ or CH₄ pulse reaction/adsorption analysis was employed to elucidate the effects of these surface-phase oxides.

The zirconia can be homogeneously dispersed on SiO₂ to form a stable surface-phase oxide. The lanthana cannot be spread well on Al₂O₃, but it forms a stable amorphous oxide with Al₂O₃. The Pt/SZrOs and Pt/SLaOs catalysts showed higher steady activity than did Pt/SiO₂ and Pt/Al₂O₃ by a factor of three to four. The Pt/SZrOs and Pt/SLaOs catalysts were also much more stable than the Pt/SiO₂ and Pt/Al₂O₃ catalysts for long stream time and for reforming temperatures above 700 °C. These findings were attributed to the activation of CO₂ adsorbed on the basic sites of SZrOs and SLaOs.