Pyrolysis atmosphere has significant effect on yield and composition of coal tar. A pyrolysis and gasification integrated reactor in laboratory was used to investigate effects of gasification syngas on yield and composition of coal tar. The results show that tar yield of Naomaohu coal reaches the maximum at 600 ℃, and gasification syngas (G-gas) is more beneficial to improve the tar yield at low temperature (550–600 ℃). Especially, 550 ℃ tar yield increases by 4.4% compared with that under N2. With the introduction of G-gas, the yield of tar obtained at high temperature (650–800 ℃) decreases, but the quality of tar obtained at 650–700 ℃ is improved obviously due to the increase of light components. The cracking reaction of aliphatic hydrocarbons and oxygen-containing compounds in volatiles from pyrolysis at 550 and 600 ℃ is intensified by G-gas, thus substituted benzene and naphthalene compounds in coal tar increase. For the volatiles obtained above 650 ℃, the secondary cracking reaction of phenolic compounds is enhanced with the introduction of G-gas, which results in a decrease of phenolic compounds in tar. G-gas is also favorable for the secondary cracking reaction of polycyclic aromatic hydrocarbons in volatiles from pyrolysis at 800 ℃, but more favorable for generation of which in the tar obtained below 700 ℃.
Ultrasonic assisted extraction residue (ER) from Naomaohu lignite (NL) was taken as the research object. ER was subjected to methanolysis at 300 ℃, and the effect of KOH was investigated. Composition of the two alcoholysis products, MP (without KOH) and MPKOH (with KOH) was analyzed by chromatograph/mass spectrometer (GC-MS). Benzyl benzoate (BB) and phenyl acetate (PA) were selected as model compounds (MER) for ER, and the alcoholysis products (BBP, BBPKOH, PAP and PAPKOH) were obtained. Results showed that the yield of MPKOH was 93.39%, while that of MP was only 5.25%, indicating that the addition of KOH greatly improved the yield of alcoholysis product. MP consisted of phenols, esters and alkanes with the relative contents of 17.92%, 34.83% and 5.98%, respectively, while the contents of the above three compounds in MPKOH were 34.8%, 10.17% and 8.71% respectively, indicating that transesterification or ester reduction reaction occurred in the alcoholysis process with the addition of KOH accompanied by alkylation reaction. Analysis of alcoholysis products of model compounds showed that methyl benzoate and benzyl alcohol were predominant in BBP, while methyl benzoate disappeared in BBPKOH, and the relative content of benzyl alcohol accounted for 91.85%; phenols were only detected in PAP, and the relative content of phenol was 87.97%. Whereas, the content of methyl substituted anisole and phenol accounted for the largest share in PAPKOH with the contents of 85.64%. Alcoholysis process of the two model compounds showed that, without KOH, transesterification or ester reduction reaction was occurred in the alcoholysis process. And the addition of KOH not only accelerated the above reaction, but also strengthened the alkylation reaction between the subsequent products and methanol.
In this paper, three-dimensional hierarchical porous carbons (HPCs) were prepared using coal tar pitch as raw material and α-Fe2O3 as template combined with KOH activation. The as-prepared HPC-3 showed large specific surface area (2003 m2/g), which was due to the synergistic effect of the occupation of α-Fe2O3 (certain mesopores and macropores) and KOH activation (abundant micropores). And the assembled electric double layer capacitor by HPC-3 exhibited the largest specific capacitance (295 F/g) and superior cycling stability (specific capacitance retention of 97.8% after 10000 cycles) in 6 mol/L KOH electrolyte. Meanwhile, the high working voltage (3.6 V) and energy density (60.0 (W·h)/kg) were obtained when it was applied to EMIMBF4 electrolyte.
To synthesize simple and efficient catalysts and their application in catalytic conversion of biomass platform compounds to prepare high value-added chemicals has always been the focus of researchers. In this paper, a catalyst composed of iron, manganese, copper and Schiff base ligand derived from amantadine salicylaldehyde was in-situ constructed to catalyze the selective oxidation of 5-hydroxymethylfurfural (HMF) to prepare 5-formyl-2-furancarboxylic acid (FFCA). The ligands and complexes were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and single crystal diffraction, and the reaction conditions such as oxidation reaction time, reaction temperature, molar ratio of MnCl2·4H2O to ligand, oxidant and catalyst dosage, etc, were optimized. Under the optimized conditions, 100% conversion of HMF and the FFCA with a yield of 52.1% can be obtained. Finally, on the basis of the reaction results, the HMF oxidation reaction process catalyzed by Mn metal complexes was analyzed.
Four typical lignins: alkali lignin, lignosulfonate, hydrolyzed lignin and G-type lignin, were selected to study their gasification weight loss characteristics, kinetic mechanism and product characteristics on a thermogravimetric analyzer (TGA) and fixed bed experiments, in order to reveal the influence of lignin sources on their gasification characteristics. The results showed that the homogeneous model fit the gasification reaction process well. Alkali lignin had the highest pyrolytic activity, reacted at lower temperature, and had the lowest activation energy. However, the structure of pyrolytic coke was dense and the gasification reactivity was poor. G-lignin had similar gasification characteristics with alkali lignin. Lignosulfonate and hydrolyzed lignin had two pyrolysis stages, and their coke gasification reactivities were high. For products characteristics, H2 and CO were the main gas products. Alkali lignin had the H2 yield as high as 55 mmol/g, the highest carbon conversion rate (87%), and the minimum residual coke. However, hydrolyzed lignin and G-lignin had lower gas production, but tar and solid residue were relatively more, which was mainly related to the inorganic mineral content and composition.
Fischer-Tropsch synthesis (FTS) is a promising route to produce various olefins and fine chemicals from non-petroleum carbon sources that can be used to produce synthesis gas, such as coal, natural gas and biomass. Cobalt-based catalysts have gained more attention in FTS for the academic research and industrial applications, owing to their excellent catalytic properties such as low water-gas-shift activity, great Fischer-Tropsch reaction activity and high chain growth probability. The structure of the microscopic active site and the surface adsorption of the cobalt-based catalyst during the Fischer-Tropsch progress have an effect on the product distribution and catalytic performance. In this review, we summarized some advancements in the development of cobalt-based F-T catalysts focusing on the effects of particle size, crystal phase, crystal plane and microscopic active site, with emphasis on the research from the types, surface adsorption behavior and characterization techniques of microscopic active site. Some suggestions for the development of cobalt-based F-T catalysts in the future are also given.
Z-scheme photocatalyst holds great promise in photocatalytic H2 evolution. In this work, a ternary Au-OVs-BiOBr-P25 Z-scheme photocatalyst with oxygen vacancies was successfully prepared, in which Au nanoparticles were used as the electron mediators to introduce into BiOBr and P25. The photocatalytic activity of this ternary photocatalyst was evaluated by overall water splitting. The H2 evolution rate of Au-OVs-BiOBr-P25 achieves an amazing value of 384 μmol/(g·h) under UV-vis irradiation. UV-vis DRS and transient photocurrent spectra revealed that the enhanced photocatalytic activity of Au-OVs-BiOBr-P25 was mainly attributed to its widened photo-response range and effective carrier separation. Furthermore, the photocatalytic mechanism was systematically studied by EPR and Photoelectrochemical measurements, which indicated that the overall water splitting occurred through the two-electron pathway. This result will provide us new ideas for developing more efficient photocatalysts for photocatalytic H2 evolution.
Solvothermal synthesis technique is an effective method to create composite materials. In this paper, a series of TiO2@MIL-101(Cr) were prepared by the solvothermal method for photocatalytic denitrification of pyridine in fuel under visible light irradiation. The products were characterized by XRD, FT-IR, SEM, TEM, BET, DRS and ESR. The result shows that 20%TiO2@MIL-101(Cr) has high catalytic activity, the pyridine removal efficiency reaches values as high as 70% after irradiation for 240 min. Finally, we obtained the possible mechanism of photocatalytic denitrification according to the HPLC-MS spectrometry results analysis.
Direct and selective conversion of methane to methanol under mild conditions still faces grand challenges. In this study, Co3O4/WO3 nanocomposite catalysts were synthesized by facile hydrothermal method, combining with surface impregnation process. The structural composition and micro morphology of Co3O4/WO3 composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and UV-visible absorption spectrum. The catalytic performance of Co3O4/WO3 on the conversion of methane to methanol was investigated under visible light illumination at room temperature. The results show that incorporating Co3O4 can remarkably improve the photocatalytic performance of methane conversion. The optimal catalyst 3.0% Co3O4/WO3 exhibits a methane conversion of 2041 μmol/g after visible light irradiation for 2 h, and the according methanol productivity and selectivity reach 1194 μmol/g and 58.5%, which are 4.03 and 2.39 times of single WO3 respectively. This performance is superior to most reported heterogeneous photocatalysts for methane conversion, meanwhile possessing excellent cyclic stability. Combining the results of transient photocurrent and electron paramagnetic resonance (EPR) with the catalytic activity, the intrinsic mechanism of enhanced methane conversion via introducing Co3O4 is revealed, which is of theoretical significance to design light-driven catalysts for methane conversion to methanol.
通过对28个最大镜质组反射率0.30%-2.05%镜煤样品的X射线衍射(XRD) 分析, 获得XRD结构参数, 得到这些参数随反射率增大呈现的阶段性规律。在镜质组反射率小于1.0%阶段, La和Lc急剧增加, d002迅速减小, 含氧官能团的脱落和脂肪长度支链化程度减小占主导; 在1.0%-1.6%阶段, La持续增加, d002先增加后减小, Lc先减小然后趋于平稳, 芳香体系脱氢和调整空间位阻同时进行; 在1.6%-2.0%阶段, d002持续减小, Lc和La的增大, 煤结构演化以芳构化为主。XRD结构参数演化与第一、二次煤化作用跃变关系密切。
以11种炼焦煤为研究对象,分别进行FT-IR和黏结指数G测试。采用PeakFit软件对FT-IR谱峰进行分峰拟合和定量计算,研究炼焦煤特征官能团含量与其黏结性间的关系。结果表明,煤黏结性大小与其FT-IR吸收峰密切相关,特别是3 000-2 800和3 700-3 000 cm-1两个吸收带;脂肪族结构是煤黏结性形成的主要决定因素,通常脂肪链越短或支链化程度越高,越有利于煤的黏结性形成;含-OH(或-NH)的氢键缔合结构可以与脂肪链协同作用,共同决定煤的黏结性能。不论煤分子有多大,只要是结构单元缩合度较小而作为桥键的脂肪链较多的结构形式,在热解过程中就会生成大量适度分子量、以结构单元为基元的液相物质。氢键是煤中主要的分子间作用形式,当若干形成氢键的官能团聚集缔合时,其相互作用会更强,甚至会形成类似超分子的结构;在形成胶质体阶段,这类氢键缔合的结构也会被打破,并形成以胶质体液相为主的物质。这些液相物质的存在,有利于胶质体的流动、黏连和固化成为半焦,从而最终获得优越的黏结性。
利用XRD和FT-IR考察了高温弱还原气氛下Na2O对两种硅铝含量不同的煤灰中矿物质组成的影响, 揭示了Na2O影响煤灰熔融特性的本质.通过FactSage计算了高温下矿物质反应的ΔG, 探讨了Na2O影响煤灰中矿物质组成的机理.结果表明, Na2O对煤灰矿物质组成的影响与原煤灰的硅铝含量密切相关.硅铝总含量82.89%的煤灰, Na2O含量为5%-20%时, 钠长石和霞石的生成是煤灰熔融温度降低的主要原因; 当Na2O含量大于20%时, 导致煤灰熔融温度降低的原因是霞石的生成.硅铝总含量47.85%的煤灰, Na2O含量小于10%时, 没有含钠矿物质生成; 当Na2O含量大于10%时, 主要生成菱硅钙钠石、青金石和含钠的硅铝酸盐矿物, 导致煤灰熔融温度降低.FactSage计算表明生成含Na矿物质反应的ΔG较小, 其在高温下更容易发生.
合成气直接催化转化制备低碳烯烃是C1化学与化工领域中一个极具挑战性的研究课题, 具有流程短、能耗低等优势, 已成为非石油路径生产烯烃的新途径。直接转化方式主要包括经由OX-ZEO双功能催化剂直接制低碳烯烃的双功能催化路线以及经由费托反应直接制备低碳烯烃的FTO路线。综述简述了近年来在合成气直接制备低碳烯烃方面的研究进展, 重点讨论了低碳烯烃的形成机理、新型催化剂的研发及助剂对其催化性能的影响, 并对合成气直接制烯烃的未来进行了展望。
利用高分辨率透射电子显微镜(HRTEM) 分析了三种不同变质程度煤样的结构特征.基于傅里叶-反傅里叶变换方法, 并结合Matlab、Arcgis和AutoCAD软件, 通过图像分析技术, 获得了HRTEM照片的晶格条纹参数.结果表明, 三种煤样的晶格条纹呈现不同特征, 按条纹长度分别归属于1×1-8×8共计八个类型.以3×3为临界点, 在1×1和2×2中, ML-8中芳香层片的比例高于DP-4和XM-3;在3×3-8×8中, ML-8中芳香层片的比例低于DP-4和XM-3.对比HRTEM和XRD参数d002发现, 随着镜质组反射率的增加d002都呈现递减趋势.
分别以β、ZSM-5和USY分子筛为载体,采用浸渍法制备了锰铈催化剂,对其低温NH3-SCR反应性能进行了评价,并采用XRD、BET、NH3-TPD、H2-TPR以及XPS对催化剂进行了表征。结果表明,三种分子筛负载的锰铈催化剂均具有较好的低温NH3-SCR反应活性,其中,Mn-Ce/USY的催化性能最好,在107℃时NOx转化率可达到90%。负载锰铈后催化剂的比表面积和孔体积均有所下降;活性组分MnOx主要以无定型态分布于催化剂表面,且在ZSM-5上检测到聚集的CeO2。催化剂表面弱酸对低温NH3-SCR反应起主要作用,催化剂表面上活性组分的表面浓度和氧化态明显不同,较高的Mn4+/Mn3+原子比和吸附氧表面浓度对提高催化剂的低温NH3-SCR反应活性有利。
采用原位合成法在γ-Al2O3表面合成了锌铝水滑石,再通过顺次浸渍法制备了一系列掺杂稀土改性的M(M=Y、La、Ce、Sm、Gd)/Cu/ZnAl催化材料,并将其应用于甲醇水蒸气重整制氢反应。探讨了稀土掺杂改性对Cu/ZnAl催化剂催化性能的影响,并采用XRD、SEM-EDS、BET、H2-TPR、XPS和N2O滴定等手段对催化剂进行了表征。结果表明,催化剂的活性与Cu比表面积和催化剂的还原性质密切相关,Cu比表面积越大,还原温度越低,催化活性越高。稀土Ce、Sm、Gd的引入能改善活性组分Cu的分散度、Cu比表面积以及催化剂的还原性质,进而提高催化剂的催化活性。其中,Ce/Cu/ZnAl催化剂表现出最佳的催化活性,在反应温度为250 ℃时,甲醇转化率达到100%,CO含量为0.39%,相比Cu/ZnAl催化剂,甲醇转化率提高了近40%。
考察了碱处理、先碱后两步酸处理对HZSM-5分子筛物化性质以及苯与甲醇烷基化反应性能的影响。结果表明, 碱处理在脱除分子筛中非骨架硅的同时, 提高了晶孔的利用率, 也中和了分子筛的强酸中心, 使催化剂活化甲醇的能力减弱, 苯与甲醇反应活性降低; 先碱后两步酸处理既脱除了分子筛中的非骨架铝, 也恢复了一部分强酸中心, 提高了苯与甲醇的反应活性。进一步考察了先碱后两步酸处理中不同碱浓度的影响, 结果表明, 适宜浓度的碱处理后再两步酸处理, 一方面, 能脱除分子筛的非骨架硅铝物种, 使分子筛的颗粒粒径更加均匀; 另一方面, 分子筛的强酸中心有所减少, 降低了催化剂的积炭失活速率, 苯转化率提高15%以上。
通过在一种真实煤灰中添加不同的氧化物或直接用氧化物配制合成灰,探究了不同灰成分对灰熔融特性的影响规律。利用FactSage 7.0对不同灰分的熔融过程进行了热力学模拟,通过熔融过程中的矿物质变化为各种灰成分对熔融特性的影响规律提供理论依据。结果表明,氧化钠对灰熔点的降低作用源于钠长石和霞石对钙长石的取代;氧化镁含量的增加对灰熔点起先降低后升高的作用,当氧化镁含量超过一定时,产生的镁橄榄石能够升高灰熔点;硫对灰熔点的升高作用源于镁橄榄石和硫酸钙对透辉石的取代;氧化钙含量的增加对灰熔点起到先降低后升高的作用,当氧化钙含量超过一定时,硅从熔点较低的矿物质迁移到熔点较高的矿物质中,升高了灰熔点。在与硅氧单元体结合的过程中,氧化钠优先于氧化钙;与氧化钙和硅氧单元体结合的氧化物的优先级为:氧化铝>氧化镁>氧化铁。
针对中低温锅炉烟气脱硝技术需求的特点,采用等体积浸渍法,以V2O5为活性组分、MoO3为助剂,制备了高钒高钼含量的V2O5-MoO3/TiO2型粉末和平板式SCR脱硝催化剂,考察了活性组分和助剂含量对催化剂活性以及抗SO2和H2O中毒性能的影响,对反应前后的催化剂进行了微观表征,并针对最优催化剂研究了其在不同烟气工况下催化剂的脱硝性能。结果表明,提升V2O5负载量可以有效提高催化剂的脱硝活性;MoO3助剂的添加也可以提高催化剂的脱硝活性。XPS、XRF、FT-IR等表征结果表明,MoO3的含量会影响催化剂中V4+/V5+的比值,其相对含量的增加有利于催化剂中非化学计量钒物种的形成以及化学吸附氧比例的增加,钼与钒物种间的交互作用是抑制SO2和H2O对催化剂的毒化作用的关键。3V2O5-10MoO3/TiO2平板式催化剂在温度为200℃、空速为3 500 h-1含SO2和H2O烟气条件下,经30 d连续反应,脱硝效率稳定维持在82%左右,该催化剂在中低温下具有优异的抗SO2和H2O中毒性能以及稳定性。