Chemical deactivation of V2O5/WO3–TiO2 SCR catalysts by additives and impurities from fuels, lubrication oils and urea solution: Part II. Characterization study of the effect of alkali and alkaline earth metals

A characterization study on a practice-oriented V₂O₅/WO₃–TiO₂ SCR catalyst deactivated by Ca and K, respectively, was carried out using NH₃-TPD, DRIFT spectroscopy, and XPS as well as theoretical DFT calculations. It was found from NH₃-TPD experiments that strongly basic elements like K or Ca drastically affect the acidity of the catalysts. Detailed DRIFT spectroscopy experiments revealed that these poisoning agents mostly interact with the Brønsted acid sites of the V₂O₅ active phase, thus affecting the NH₃ adsorption. Moreover, these experiments also indicated that the V⁵⁺ = O sites are much less reactive on the poisoned catalysts. XPS investigations of the O 1s binding energies showed that the oxygen atoms of the V⁵⁺ = O sites are affected by the presence of the poisoning agents. Based on these results and on DFT calculations with model clusters of the vanadia surface, the poisoning mechanism is explained by the stabilization of the non atomic holes of the (0 1 0) V₂O₅ phase as a result of the deactivation element. Consequently, V–OH Brønsted acid sites and V⁵⁺ = O sites are inhibited, which are both of crucial importance in the SCR process. The deactivation model also gives an explanation to the very low concentrations of potassium needed to deactivate the SCR catalyst, since one metal atom sitting on such a non-atomic hole site deactivates up to four active vanadium centers.     

燃煤电厂煤粉炉及CFB锅炉PM2.5产生及排放特性的现场实验研究

采用稀释采样方法对一台220 MW煤粉炉(锅炉A)及一台300 MW的CFB锅炉(锅炉B)电袋复合式除尘器前后PM_2.5进行现场采样。通过ELPI测定PM_2.5的粒径分布;采用SEM分析PM_2.5的显微结构;采用EDX及ICP-OES分别对分级PM_2.5中次量及痕量元素含量进行了检测。结果表明,锅炉A和B除尘前后对应的PM_2.5粒数及质量浓度分布均不同;锅炉A和B产生的PM_2.5分别以较为光滑球形和不规则形状为主,锅炉A除尘后PM_2.5呈表面粗糙球形,锅炉B除尘后PM_2.5单颗粒形貌特征不变;锅炉A和锅炉B产生的PM_2.5除尘前后在各粒径段中Si、Al、Fe、Ca和Mg含量基本一致,As、Cd和Se含量随着粒径的减小而增大;除尘后锅炉A产生PM_2.5中As和Se含量增加,且在亚微米PM_2.5中As和Se含量的增加更明显,锅炉B除尘后PM_2.5中As和Se含量基本不变。     

高铁酸钾强化铁锰氧化膜过滤去除水中有机物

前期研究发现铁锰氧化膜(MeO_x)对水中氨氮、铁、锰等污染物具有较高的去除率,但对水中有机物(以COD_Mn计)的去除效果较差。为了提高MeO_x对COD_Mn的去除率,本研究采用高铁酸钾强化MeO_x的催化氧化过程,探究其对水中COD_Mn的有效去除及相关影响因素。实验结果表明：仅投加0.1mg/L的高铁酸钾强化MeO_x过滤,对于进水中20mg/L的COD_Mn,去除率可达到约92.5%;滤速对其具有一定的影响,去除率随着滤速的提高呈下降的趋势,在6～10m/h出水滤速中的COD_Mn均能达到3.0mg/L以下,当滤速达到11m/h时去除率下降到81.65%;较低的p H(约6.51)具有一定的不利影响,COD_Mn的去除率随着p H的降低而逐渐下降;进水中NH₄⁺也会影响COD_Mn的去除,NH₄...     

Evidence for mineral matter forms in coal liquefaction extracts

High- and low-temperature ashes from feed coal, coal extract solution and filter cake from a two-stage coal liquefaction process have been studied by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray fluorescence (SEM/EDX). Hydrocracking experiments using alumina support only, in place of the active Ni/Mo catalyst on alumina, were also carried out, with trace metal analysis of the coal extract solution feed and hydrocracked extracts using atomic absorption and emission spectroscopy. The major mineral transformations occurring were of pyrite to pyrrhotite and the fixation of organic sulphur by calcium carbonate. Mineral particles were not observed in the coal extract solution ashes, even under high magnification, and the study indicated that size alone was not a determining factor as to whether a coal mineral was to be found in a coal-derived liquid. None of the trace metals was deposited on the alumina support under hydrocracking conditions, in marked contrast to the results obtained with the normal Ni/Mo catalyst. These results lead to the conclusion that for the deposition of trace elements to occur a reaction must take place and hence the trace elements must be chemically bound in some form.     

煤灰酸浸渣碳分法制备纳米白炭黑性能研究

为实现煤灰渣资源化高效利用,本文以煤灰酸浸提铝后的高硅残渣经焙烧制得的Na₂SiO₃溶液为原料,采用碳分法制取高附加值的纳米白炭黑。通过单因素法,采用比表面积测试法（BET）、邻苯二甲酸二丁酯（DBP）吸油值测定、透射电镜（TEM）、红外光谱分析（FTIR）、X衍射分析（XRD）等分析表征手段,研究不同的实验条件对制得的纳米白炭黑性能的影响,得到碳分法制取纳米白炭黑的最佳实验工况。实验表明,当硅酸钠溶液中SiO₂质量分数为2%、CO₂通气速率为0.5/min、溶液反应温度为65~75℃、反应终点pH为8时,通过陈化、过滤、洗涤、共沸蒸馏、烘干后,可得到粒径为20~40nm、DBP吸油值为3.10mL/g、比表面积为250m²/g、质量分数91.88%的性能最优纳米白炭黑。     

碱法回收湿法磷酸萃余渣中五氧化二磷的研究

磷酸是一种重要的化工原料。目前,生产磷酸及磷酸盐的方法主要采用湿法,但湿法磷酸中含有大量的杂质,在利用溶剂萃取法净化湿法磷酸的过程中,大量金属离子杂质以不溶性磷酸盐的形式沉淀出来,其中不溶性五氧化二磷的回收利用问题受到广泛关注。采用碱解工艺设计单因素实验,考察了液固比、n（Na₂O）/n（P₂O₅）、反应温度、反应时间对氢氧化钠分解湿法磷酸萃余渣（难溶性金属磷酸盐）效果的影响,并选出适宜的反应条件范围,在此基础上通过二次回归正交实验得到最佳的反应条件。结果表明,最佳反应条件为：液固比为30 mL/g、n（Na₂O）/n（P₂O₅）为3.31、反应温度为82 ℃、反应时间为4.05 h。在最佳的工艺条件下,五氧化二磷的回收率可达到92.48%,反应碱液可进一步作为生产磷酸三钠的原料而加以利用。该研究得到了一种利用湿法磷酸萃余渣的合理方案,并给出了相关参数,为该方案的实际应用提供指导,对萃余渣的利用和环境保护具有重要意义。     

Reactions of coals of different ranks with CO---H2 mixtures with and without sodium aluminate

Well-characterized coals of different H/C atomic ratio and rank were reacted at 365°C with CO, H₂ and CO---H₂ mixtures in water in the presence and absence of sodium aluminate. The optimum H₂/CO ratio for conversion was found to vary with the type of coal. It was <1 : 1 for low-rank and subbituminous coals, whereas the conversion of bituminous coals either did not vary with H₂/CO ratio or reached a maximum at a higher H₂/CO ratio (2 : 1). Even for a bituminous coal there was no advantage in reducing the water/coal ratio below 2 : 1 in NaAlO₂-catalysed reactions. The conversions increased with increasing H/C atomic ratio of the coal and decreasing rank, with or without NaAlO₂. Asphaltene yields increased with increasing coal rank and increasing proportion of CO in the H₂---CO reacting gases. The mechanistic implications of these results are briefly discussed.     

Bioleaching of molybdenum from coal liquefaction catalyst residues

It has been shown that the bacterium Thiobacillus ferrooxidans can solubilize MoS₂ from coal liquefaction catalyst residues. The MoS₂ is formed during the liquefaction process from a molybdenum catalyst precursor. MoS₂ is insoluble; in order to be recovered and reused, it must be converted to a soluble form. T. ferrooxidans can oxidatively solubilize the molybdenum in MoS₂ to molybdate, in which form it can be recovered as a soluble or HCl extractable material. Bioleaching experiments show that with a starting cell concentration of 1.0 × 10⁷ cells ml⁻¹, or greater, a significant amount of the molybdenum in the residue was solubilized. These experiments indicate that the amount of molybdenum biologically solubilized from the liquefaction residues is dependent on inoculum size, with all strains of T. ferrooxidans tested having equal ability, and on the particle size of the residue. An important factor in the solubilization of MoS₂ by T. ferrooxidans is the inhibitory effect of molybdate. Literature reports that as little as 10 ppm molybdate is inhibitory to growth or ferrous iron oxidation. However, leachates containing in excess of 70 ppm molybdenum (equivalent to 116 ppm molybdate) were generated as a result of bioleaching of the liquefaction residue. When cells from previous leaching experiments were used to inoculate flasks containing fresh media and additional liquefaction residue, the bacteria were able to bioleach the fresh residue. Recent experiments have focused on the ability of T. ferrooxidans to produce protective agents in the leachate that minimize the inhibitory effects of molybdate. We found that production of the protective factor(s) did not depend on previous exposure of the cells to molybdenum or liquefaction residue.     

府谷煤CO2催化气化反应性的研究

加入适宜的催化剂可以提高气化反应速率,降低起始气化温度。为了研究不同阴离子（SO₄^2-、CO₃^2-、Cl^-）盐对府谷煤热失重过程的影响,利用热重分析仪对负载了8种催化剂（K₂CO₃、K₂SO₄、KCl;Na₂CO₃、Na₂SO₄、NaCl;FeSO₄、FeCl₂）的煤样进行了CO₂气化实验,其中每克府谷煤的K⁺、Na⁺、Fe²⁺负载量分别为0.001mol。同时采用升温动力学模型进行了数据拟合。实验结果表明：催化剂对煤与CO₂的低温热解并无明显的催化作用,而在高温气化阶段催化效果显著。对于钾盐和钠盐催化剂,当阳离子相同时,其催化活性顺序为：CO₃^2->SO₄^2->Cl^-。对于铁盐催化剂,FeSO₄的催化活性优于FeCl₂。动力学结果发现：负载催化剂煤样的活化能大小符合上述实验规律,分布在169～232.6kJ/mol之间,相比原煤（267.9kJ/mol）都有一定程度的降低。     

660MW燃煤锅炉细微颗粒物中次量与痕量元素的分布特性

应用承重撞击器(DGI)采样系统在南昌某电厂2^#锅炉电除尘器前进行颗粒物采集,并同时采集了原煤样和底灰样。对飞灰的质量粒径分布、底灰和飞灰中次量与痕量元素的分布特性进行了分析。结果表明PM_1.0和PM_2.5质量分别占PM₁₀质量的16.0%~17.4%和46.9%~50.6%;Na、Mg、P、S主要富集在亚微米颗粒物中,Al、Si、Ca、Ti、Fe、K主要富集在超微米颗粒物中;随着颗粒物粒径的减小,As、Cd、Cr、Pb的浓度逐渐增大,且在亚微米颗粒物中的增幅大于超微米颗粒物,Mn在各级颗粒物中浓度相近;As、Cd、Cr、Pb大量富集于亚微米颗粒物之上,Mn在各级颗粒物中富集特性无明显差异,且各痕量元素挥发特性存在以下规律:As>Cd>Cr>Pb>Mn;文中给出了无控制条件下痕量元素的排放因子,PM_1.0中各元素排放比例存在以下规律:As>Cd>Cr>Pb>Mn。     

A multi-scale model for CO2 sequestration enhanced coalbed methane recovery

This paper presents a multi-scale model to simulate the multicomponent gas diffusion and flow in bulk coals for CO₂ sequestration enhanced coalbed methane recovery. The model is developed based on a bi-dispersed structure model by assuming that coal consists of microporous micro-particles, meso/macro-pores and open microfractures. The bi-disperse diffusion theory and the Maxwell-Stefan approach were incorporated in the model, providing an improved simulation of the CH₄—CO₂/CH₄—N₂ counter diffusion dynamics. In the model, the counter diffusion process is numerically coupled with the flow of the mixture gases occurring within macro-pores or fractures in coal so as to account for the interaction between diffusion and flow in gas transport through coals. The model was validated by both experimental data from literature and our CO₂ flush tests, and shows an excellent agreement with the experiments. The results reveal that the gas diffusivities, in particular the micro-pore diffusivities are strongly concentration-dependent.     

Characterization and tribological investigation of sol-gel Al2O3 and doped Al2O3 films

Thin films of Al₂O₃ and doped Al₂O₃ were prepared on a glass substrate by dip coating process from specially formulated ethanol sols. The morphologies of the unworn and worn surfaces of the films were observed with atomic force microscope (AFM) and scanning electron microscope (SEM). The chemical compositions of the obtained films were characterized by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of obtained thin films sliding against Si₃N₄ ball were evaluated and compared with glass slide on a one-way reciprocating friction tester. XPS results confirm that the target films were obtained successfully. The doped elements distribute in the film evenly and exist in different kinds of forms, such as oxide and silicate. AFM results show that the addition of the doped elements changes the structure of the Al₂O₃ films, i.e., a rougher and smoother surface is obtained. The wear mechanisms of the films are discussed based on SEM observation of the worn surface morphologies. As the results, the doped films exhibit better tribological properties due to the improved toughness. Sever brittle fracture is avoided in the doped films. The wear of glass is characteristic of brittle fracture and severe abrasion. The wear of Al₂O₃ is characteristic of brittle fracture and delamination. And the wear of doped Al₂O₃ is characteristic of micro-fracture, deformation and slight abrasive wear. The introduction of ZnO is recommended to improve the tribological property of Al₂O₃ film.     

Trace element partitioning during the firing of washed and untreated power station coals

The effect of coal washing on trace element content and combustion behaviour of four world-traded coals has been studied at rig scale. The inputs and process outputs from a 1 MW combustion test facility, including coal, bottom ash, suspended fly ash, retained ash and flue gas, have been analysed for a standard suite of 17 trace elements. The results suggest that although coal cleaning significantly reduces the total ash content of the coal, the concentrations of individual trace elements are not reduced proportionately. Combustion of the washed coals resulted in increased concentrations of trace elements in the fly ash, although total fly ash loadings were reduced. Cleaning appeared to have little effect on concentrations of gaseous trace elements in the flue gas. The partitioning of the more volatile trace elements such as mercury and selenium between the vapour and solid phase was influenced by the amount of excess oxygen in the furnace, presumably affecting carbon-in-ash levels.The results suggest that the coal cleaning undertaken for these experiments did not significantly reduce the emissions to atmosphere of trace elements. The ultimate emissions will be determined by the efficiency of the dust capture systems.     

甲烷活化与煤热解耦合过程提高焦油产率研究进展

热解是实现煤清洁高效利用的重要途径之一。针对传统煤热解焦油收率低的现状，从煤热解反应机理出发，围绕甲烷催化/等离子体活化与煤热解过程耦合提高焦油收率的研究工作进行综述，重点介绍了甲烷部分氧化、甲烷二氧化碳重整、甲烷芳构化、甲烷水蒸气重整及甲烷等离子体活化与煤热解耦合过程特点以及对焦油产率的影响。结果显示，相对氮气和氢气气氛下热解，耦合过程焦油产率显著提高，并具有煤种普适性。同时借助同位素示踪技术对耦合过程焦油产率提高机理进行分析。结果表明，甲烷经催化/等离子体活化后产生的活性物质通过与煤热解形成的自由基结合，参与了焦油的形成，是焦油产率显著提高的根本原因。耦合反应器的设计和甲烷活化催化剂的开发是今后该过程工业应用的关键。     

枣泉煤分子模型构建及热解的分子模拟

以宁东枣泉煤为研究对象，使用工业分析、元素分析、X射线光电子能谱、¹³C固体核磁等表征手段和计算机辅助，构建获得枣泉煤大分子结构模型。经过分子动力学退火动力学模拟和几何结构全优化，与初始结构相比键长、键角发生明显改变，立体构型显著，芳香层片之间近似平行的排列方式明显。获得的傅里叶变换红外和¹³C固体核磁的实验与计算谱图总体吻合较好，进一步证明了构建模型的合理性。使用反应分子动力学方法模拟枣泉煤的热解过程，考察不同热解终温和升温速率对热解行为的影响。结果发现，随着温度的升高，反应速率逐渐加快。不同升温速率对枣泉煤热解过程中气体的产生有显著影响。在动力学模拟中大多产生C₁₅以下的碎片，大分子的种类则并不多。随着升温速率的增加，气、液、固三相产物整体上都呈现下降的趋势。此外，还根据反应分子动力学模拟结果追踪了热解过程中CO₂的形成机理，获得了三种不同的CO₂形成路径。     

A spectroscopic investigation of the banding or lithotypes occurring in Victorian brown coal seams

Solid-state ¹³C n.m.r. and infrared spectroscopy were used to investigate the gross differences in chemical structural between the five primary lithotypes or coal bands present in Victorian brown coal seams. Examination of a series of coal lithotypes, along with their insoluble kerogen fractions, indicated significant structural variation between the light and dark samples, particularly in their aromaticities and levels of lignin-derived structures. Comparison of K₂₉₂₀ (cm mg⁻¹) and K₁₇₁₀ (cm mg⁻¹) infrared data revealed that the aliphatic C-H content did not exhibit the level of lithotype dependence shown by carbonyl/carboxyl concentration. Correlation with ¹³C n.m.r. data revealed a direct inverse relation between aromaticity and carbonyl/carboxyl content. Aromaticity and carbonyl/carboxyl content are suggested to be the main gross chemical structural properties affecting lithotype classification. Investigation of a depth profile of the light lithotype revealed that gross structural variation between the samples did not result from rank effects. Rather, the depth profile reflects minor depositional variations which did not affect their lithotype classification. The gross chemical characterization of the lithotypes supports paleobotanical interpretation regarding the different depositional environments and inputs responsible for the observed coal banding.     

Characterization and Tribological Investigation of Sol–Gel Titania and Doped Titania Thin Films

Titania (TiO₂) and doped TiO₂ ceramic thin films were prepared on a glass substrate by a sol–gel and dip-coating process from specially formulated sols, followed by annealing at 460°C. The morphologies of the original and worn surfaces of the films were analyzed with atomic force microscopy (AFM) and scanning electron microscopy. The chemical compositions of the obtained films were characterized by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of TiO₂ and doped TiO₂ thin films sliding against Si₃N₄ ball were evaluated on a one-way reciprocating friction and wear tester. The AFM analysis shows that the morphologies of the resulting films are very different in nanoscale, which partly accounts for their tribological properties. XPS analysis reveals that the doped elements exist in different states, such as oxide and silicate, and diffusion took place between the film and the glass substrate. TiO₂ films show an excellent ability to reduce friction and resist wear. A friction coefficient as low as 0.18 and a wear life of 2280 sliding passes at 3 N were recorded. Unfortunately, all the doped TiO₂ films are inferior to the TiO₂ films in friction reduction and wear resistance, primarily because of their differences in structures and chemical compositions caused by the doped elements. The wear of the glass is characteristic of brittle fracture and severe abrasion. The wear of the TiO₂ thin film is characteristic of plastic deformation with slight abrasive and fatigue wear. The doped TiO₂ thin films show lower plasticity than the TiO₂ thin film, which leads to large cracks. The propagation of the cracks caused serious fracture and failure of the films.     

宁东红石湾煤大分子模型构建及量子化学计算

使用工业分析、元素分析、固体核磁（¹³C NMR）、X射线光电子能谱（XPS）、傅里叶变换红外光谱（FT-IR）对宁东红石湾（HSW）煤样进行表征,获得煤样中元素赋存的种类、价态、化学键环境等物质微观结构的关键参数。结果表明HSW煤结构以芳香族为主,占75.96%,桥接芳碳与周碳比为0.315,可知其结构中以萘为主,苯和蒽为辅。氧原子主要以醚氧基（C-O）、羰基（C=O）和羧基（-COO）的形式存在,其中C-O占53.57%。氮原子以吡啶和吡咯的形式存在。苯环的连接方式以三、四取代为主,分别占47.77%、32.97%,脂肪族中环烷烃或脂肪烃-CH₃占优势。确定HSW煤的分子式为C₂₂₁H₁₄₈O₂₈N₂,分子量为3142.32。在此基础上结合计算机辅助实现了二维和三维大分子模型构筑。应用量子化学计算对HSW煤大分子模型进行了优化及核磁共振、红外光谱模拟,验证了所建模型的合理性。最终实现了HSW煤的微观分子结构的实验与量子化学描述。     

选择性透过CO2气体PVA/淀粉膜制备及性能研究

对聚乙烯醇(PVA)/淀粉膜进行接枝改性,引入含有叔胺基团的甲基丙烯酸二甲氨基乙酯(DMAEMA),使其对CO₂气体具有选择性透过功能,并对CO₂透过量进行优化,研究其分子结构与性能的关系。红外光谱、X射线光电子能谱、原子力显微镜照片及透气测试结果证明,加入淀粉接枝DMAEMA共聚物后,PVA/淀粉改性膜对CO₂具有选择透过性。接枝共聚物的接枝率和添加量影响CO₂透过量,当添加1.5%(质量分数,下同)的接枝率为55.3%的接枝共聚物,膜的CO₂透过量由1.577 cm³/(m²·24 h·0.1 MPa)提高到45.786 cm³/(m²·24 h·0.1 MPa),提高了28.03倍。X射线光电子能谱测试结果显示,改性膜透过CO₂后,N1s谱图中399.8 eV处的结合能减小,在401.8 eV结合能增大,可能CO₂与膜上叔胺基团发生反应,实现...     

煤颗粒燃烧过程氧化机理及有机氮转化的分子模拟：以宁东红石湾煤为例

煤燃烧是煤炭资源有效利用的重要方式之一。从原子分子水平上识别煤燃烧的机理,系统把握反应条件的影响,揭示含氮污染物迁移转化的路径对于煤炭高效清洁利用具有重要意义。以前期构建的宁东红石湾煤分子结构模型为基础,采用反应分子动力学模拟方法对煤大分子结构聚集态模型进行燃烧反应模拟,考察化学当量比和反应温度对燃烧过程中结构演变、燃烧反应物和产物的影响,探究有机氮转化路径。研究发现,随着反应不断进行,煤结构的断裂变化非常明显。不同化学当量比和不同温度下煤燃烧的结果表明,化学当量比越大、燃烧温度越高时,O₂分子消耗速度越快,CO₂的生成量也越多。对燃煤过程中含氮气体分子数量的分析表明,HCN是重要的含氮中间产物,NO、NO₂是主要含氮气体产物。本研究还建立了煤燃烧过程中有机氮的转化路径,获得了HCN、NO和NO₂的演变过程。