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2018年  第46卷  第9期

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研究论文
摘要:
Two different ranks of coals (Ximeng lignite, L and Xishan bituminous coal, B) and biomass (cornstalk, C) were selected to investigate effects of heating rate and pressure on structure and oxidation reactivity of chars from pyrolysis. The chars were prepared in a two-step pressurized fixed bed reactor at 900℃ from slow pyrolysis and fast pyrolysis under a range of pressures (0.1-2.0 MPa), which were marked as SC and FC, respectively. Specific surface area, surface morphology, and aromaticity of chars were characterized. Isothermal thermogravimetry was performed to study oxidation reactivity of chars. Results indicate that the char yields of three samples are distinctly varied and pyrolysis pressure and heating rate influence them through different residence time and diffusion rate of volatiles varying with different raw materials. The yields of chars from fast pyrolysis are all lower than those from slow pyrolysis and they increase slightly with increasing pyrolysis pressure from atmospheric pressure to 2.0 MPa. The specific surface areas of L-FC and B-FC are larger than that of L-SC and B-SC. However, the specific surface area of C-FC is smaller than that of C-SC. The morphology of FC is all rougher than that of SC. The aromaticity of B-SC is higher than that of B-FC, while that of L-SC and C-SC is lower than that of L-FC and C-FC derived from pressurized pyrolysis. The evolution of char structure at low heating rate and high pressure results generally in poor reactivity of char. The reactivity of cornstalk char is much higher than that of coal char, which should be correlated to the dispersion and concentration of inorganic matters in the char which is affected by heating rate and pressure.
摘要:
以众唯瘦煤作为主炼焦煤,大同长焰煤萃取物作为添加剂,进行共炭化处理制备坩埚焦。利用偏光显微镜法定量研究焦炭光学显微组分,获得焦炭的各向异性指数(DRAS);采用XRD及分峰拟合的方法研究了焦炭的微晶粒径(Lc)、芳香缩合度(Ia)、石墨化度(g);利用Raman光谱结合分峰拟合的方法研究了焦炭中理想石墨微晶含量(Ig)。对所得焦炭的光学显微组分进行定量分析发现:大同长焰煤热解萃取产物的添加对共炭化焦炭的光学显微组分有显著的影响,利用偏光显微镜法计算出焦炭的DRAS与XRD和Raman计算的焦炭微晶参数呈现很好一致性。并且,焦炭的显微强度与其微观结构关联性极大。
摘要:
将K+、Ca2+、Fe3+的硝酸盐用于处理脱灰和丰煤样(K-DC、Ca-DC和Fe-DC),在热重分析仪中考察了处理煤样的失重特征和气体逸出规律。结果表明,处理煤样的总失重率减少,CO2和H2的浓度较原煤(DC)的高。通过固定床研究了处理煤样热解过程中产物的分配规律,采用元素分析、FT-IR、模拟蒸馏和GC-MS等分析了半焦的结构特征和焦油的组成与品质。结果表明,与DC相比,处理煤样的半焦和气体产率增加,焦油产率降低,相应半焦的不饱和度和缩合程度降低。在各金属组分的作用下,焦油中的轻质组分分率增加,其中,Fe3+的作用最为显著,其值增加了22.4%。GCMS结果表明,长链烷烃含量高达70%,是焦油组分重的主要原因,K和Fe组分可促进其分解。
摘要:
在管式炉中,研究了煤灰对玉米秸秆焦在不同气化条件下钾的固留率和灰渣熔融性的影响。采用电感耦合等离子体发射光谱(ICP-AES)、X射线衍射(XRD)以及灰熔点测定仪等检测表征手段对气化灰渣中的钾元素含量、矿物质组成以及其熔融点进行了分析。实验以高岭土为参考,研究发现,煤灰如同高岭土具有一定的固钾能力,且随着添加量的增加钾固留率呈现增加的趋势,同时灰渣熔点也得到了提升。灰渣产物的XRD组成分析表明,挥发至气相中的钾以及灰渣中以熔融态存在的钾盐与煤灰中的硅铝化合物反应生成了高熔点的KAlSi3O8、KAlSi2O6和KAlSiO4,从而达到固钾的效果并提升了灰渣的熔点。
摘要:
采用等体积浸渍法、浸渍沉淀法和机械化学法(市售载体和自制载体)制备了Cat-1、Cat-2、Cat-3和Cat-4四种催化剂,通过BET、H2-TPR、XRD、XPS和NH3-TPD等表征催化剂的结构特征,考察了各催化剂对煤焦油模型化合物甲苯和芘(3%,质量分数)裂解反应性能的影响。结果表明,四种催化剂均为介孔材料,且Cat-4的介孔有序度更高,比表面积最大,达235 m2/g。Cat-4催化剂中,NiAl2O4尖晶石的还原峰面积最高,占总面积的85.2%,还原后Ni的分散度最大,粒径最小,约为10.0 nm,意味着活性位点多。实验表明,除Cat-1外,其他催化剂对芘的裂解活性基本相当,其中,Cat-4作用下的析碳量最低,为10.84%,经Cat-1、Cat-2和Cat-3裂解后,体系中的析碳量分别较Cat-4增加了35.0%、74.7%和45.7%。可见,机械化学法制备的催化剂不仅具有最高的比表面积利于活性组分分散,而且NiAl2O4尖晶石含量最高,可抑制裂解过程中积炭的生成,因而最适宜于甲苯+芘裂解体系。
摘要:
采用碱性条件下"后处理"脱硅的方法,制备了一系列多级孔Hβ分子筛,考察了NaOH浓度对Hβ分子筛上木质素催化热解性能的影响。结果表明,当NaOH浓度小于0.2 mol/L时,碱处理后的多级孔Hβ分子筛的介孔数量增加,木质素热解液体产物的收率随着NaOH浓度提高而显著增加。当NaOH浓度小于0.5 mol/L时,碱处理可以保持多级孔Hβ分子筛的微孔结构基本不被破坏,木质素催化热解具有较好的脱氧效果;产物以芳烃为主,含氧化合物的收率始终小于3%。当NaOH的浓度增加到1 mol/L时,会造成Hβ分子筛过度脱硅,骨架坍塌;由于Hβ分子筛的多级孔结构被破坏,此时不仅木质素热解液体产物的收率降低,而且脱氧效果变差。
摘要:
制备了KNO3/Al2O3负载型固体碱催化剂,通过XRD、DRIFT、低温氮吸附、ICP和碱度滴定等手段对催化剂表面性质进行了表征,研究了其对大豆油与甲醇酯交换制备生物柴油的催化性能,剖析了在反应过程中该催化剂的催化本质以及失活原因。结果表明,高温焙烧后Al2O3表面KNO3完全分解,形成了大量偏铝酸钾分散在载体表面;在酯交换反应时Al2O3表面的偏铝酸盐等活性组分不断溶出并参与反应,这是该催化剂表现出高活性的主要原因。在反应过程中生成的产物生物柴油和甘油对催化剂的活性有很大影响,其中,生物柴油与活性物种发生的皂化反应是造成催化剂失活的主要原因。
摘要:
甲烷无氧直接制备芳烃和氢气是碳一化学与催化领域中一个极具挑战性的研究课题,具有碳原子利用率高、二氧化碳零排放、工艺流程短和绿色环保等优势,已经成为世界各国研究机构的重要研究方向。本研究基于作者课题组在甲烷无氧芳构化反应的研究工作,结合2013-2017年的相关文献,对目前甲烷无氧芳构化的研究现状进行综合评述。重点讨论甲烷无氧芳构化反应机理与积炭形成、催化剂改性及再生、膜反应器、非钼基催化剂体系等工作,并对甲烷无氧芳构化直接制备芳烃的未来前景进行了展望。
摘要:
采用TEAOH溶液处理MFI结构ZSM-5分子筛、MWW结构MCM-22分子筛,NaOH溶液处理TON结构ZSM-22分子筛、CHA结构SSZ-13分子筛得到四种结构的扩孔分子筛。在反应温度480℃、反应压力0.1 MPa、甲醇与水质量比1:1、甲醇质量空速1.5 h-1的条件下,考察了四种扩孔分子筛的甲醇制丙烯(MTP)催化性能,并采用XRD、N2吸附-脱附、NH3-TPD、TG、UV-Raman和GC-MS等方法表征催化剂的物化性质及MTP反应2 h后的分子筛积炭性质。结果表明,四种分子筛扩孔改性后均出现介孔,其中,T-ZSM-5分子筛在MTP反应中寿命最长;T-MCM-22分子筛寿命次之且失活速率慢;而一维孔道结构N-ZSM-22分子筛和八元环尺寸较小的N-SSZ-13分子筛均失活迅速。受拓扑结构和孔道扩散的影响,MTP反应2 h后,分子筛积炭量增加的顺序为T-ZSM-5<N-ZSM-22<T-MCM-22<N-SSZ-13且可溶焦分子质量随积炭量增加而增重,即从五甲基苯增重到菲、芘等多环芳烃。
摘要:
Density functional theory calculations were used to investigate CO2 adsorption behaviors on Fetet1-and Feoct2-terminated surface of Fe3O4 (111). The results indicated that on the Fetet1-terminated surface, the linear CO2 is favored at 1/5 monolayer (ML), whereas the bent CO2 bonded to surface O, i.e. carbonate structure, becomes possible at higher coverage. On the Feoct2-terminated surface, the bent CO2 is favored; both carbonate and carboxylate structure are formed at both 1/6 and 1/3 ML. Meanwhile, the Fetet1-terminated Fe3O4(111) surface has weak coverage effects, whereas the Feoct2-terminated Fe3O4(111) surface has strong coverage effects; the Feoct2-terminated surface is thermodynamically more favorable than the Fetet1-terminated surface for CO2 adsorption.
摘要:
Fuel desulfurization is an appealing topic for the chemical industry since severe environmental regulations regarding SO2 emissions have been legislated in many countries. In order to reduce the amount of sulfur-containing compounds in fuels, responsible for high SOx emission levels, a green chemistry approach is compulsory. In this paper, vanadium salen and salophen complexes were used in the oxidation of a model aromatic sulfide, such as dibenzothiophene (DBT), in the presence of H2O2 as green oxidant. The oxidative process was successfully coupled with the extraction of the oxidized compounds by ionic liquids. The system resulted highly selective for sulfide oxidation, showing poor reactivity toward the oxidation of alkenes and allowing a significant reduction of S content in a model benzine. To note, the use of microwave in place of standard heating allowed to obtain 98% of DBT oxidation and almost complete sulfur extraction in the model fuel in 1000 s. For these reasons, this system was considered an easy, rapid and clean process to achieve fuel desulfurization.
摘要:
结合分子印迹技术,MOF199为基体,以二苯并噻吩(DBT)为模板分子,甲基丙烯酸(MAA)为功能单体,制备了新型表面分子印迹聚合物材料MOF@SMIP。采用SEM、BET、FT-IR等对其结构和形貌进行表征,在模拟油样中进行吸附评测,吸附平衡时间为1.5 h。MOF@SMIP对DBT吸附量为130.73 mg/g较MOF199吸附量37.79 mg/g有很大提升,同时MOF@SMIP吸附量对比MOF@NIP吸附量(57.13 mg/g)优势明显,印记因子fimp为2.29。吸附行为遵循伪一阶动力学模型说明吸附主要为物理过程。选择性吸附实验表明,MOF@SMIP对目标分子DBT表现出比对结构类似物苯并噻吩(BT)和联苯更高的亲和力,吸附DBT对干扰物BT和联苯的相对选择系数k'分别达到2.55和2.14。
摘要:
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C, Pt/C-ATO, Pd/C and Pd/C-ATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25℃ and in a direct methane proton exchange membrane fuel cell at 80℃. The electrocatalysts prepared also were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic (fcc) structure, and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic (fcc) structure. For Pt/C-ATO and Pd/C-ATO, characteristic peaks of cassiterite (SnO2) phase are observed, which are associated with Sb-doped SnO2 (ATO) used as supports for electrocatalysts. Cyclic voltammograms (CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However, this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism, where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed, which indicates the production of carbon dioxide. Polarization curves at 80℃ in a direct methane fuel cell (DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
摘要:
以三聚氰胺作为合成g-C3N4纳米片的前躯体,以Bi(NO33·5H2O和KBr作为合成BiOBr的原料,采用水热法构建g-C3N4/BiOBr二维异质结可见光催化剂,有效的晶面复合和合适的能带组合有助于增强g-C3N4和BiOBr的可见光催化活性。利用X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)、光致发光光谱(PL)和紫外-可见漫反射光谱(UV-vis DRS)等方法表征其结构、光学性质以及组成结构。在可见光(λ>420 nm)下以光催化降解RhB来评价合成催化剂的光催化活性,结果表明,g-C3N4/BiOBr光催化降解罗丹明B(RhB)的效率高于单体g-C3N4和BiOBr,并对g-C3N4/BiOBr增强可见光催化RhB机理进行解释。