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2021年 第49卷  第10期

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2021-10 目录
2021, 49(10): 1-8.
摘要:
摘要:
采用二硫化碳、甲醇、丙酮和二硫化碳/丙酮(等体积混合溶剂)对淖毛湖褐煤(NL)进行逐级超声萃取,得到各级萃取物(E1−E4)和最终萃余物(ER)。采用GC-MS对各级萃取物E1−E4中的化合物组成和结构进行分析,发现E1中主要为烷烃、芳烃、醇类化合物和酯类化合物;E2中以烷烃、醇类化合物和酯类化合物为主。醇类化合物、酚类化合物以及酯类化合物是E3中的主要物质,且酯类化合物主要为邻苯二甲酸二酯类化合物。受到CS2和丙酮这两种溶剂协同作用的影响,E4中的烯烃类化合物的相对含量也比较高。采用FT-IR对NL、E1−E4和ER中所含官能团进行表征分析,结果发现,超声萃取过程只是将淖毛湖褐煤大分子骨架中游离的小分子化合物以及与大分子骨架以弱共价键相连的小分子萃取了出来,并未破坏煤样的大分子骨架结构。此外,NL和ER红外数据的分峰拟合结果显示,经过超声萃取后,ER中红外吸收峰的种类并未增加,只是峰的强度发生了改变。通过NL和ER的TG-DTG曲线可知,超声萃取后,NL的失重量由47.09%增加至51.04%,最大失重速率峰由450 ℃提前至430 ℃。NL和ER基于Coats-Redfern模型的热解动力学分析结果表明,经过超声萃取后,ER在快速热解阶段的活化能比NL更低,热解过程更容易进行。
摘要:
A novel and highly active nitrogen-doped porous carbon-supported nickel catalyst Ni@N-PC was successfully developed by a thermolysis of nickel-based zeolitic imidazolate frameworks growing on both sides of graphitic carbon nitride and used for catalyzing hydroconversion of isopropanol soluble portion from ultrasonic extraction of high-temperature coal tar (ISPHTCT). The active nickel nanoparticles were mainly encapsulated on the top of carbon nanotubes and partially dispersed on the surface of carbon nanosheets. Naphthalen-1-ol was used as a model compound to investigate the catalytic hydroconversion activity under different reaction conditions and reveal the mechanism for catalytic hydroconversion. The ISPHTCT and catalytic hydroconversion products of ISPHTCT (ISPCHCP) were analyzed with gas chromatograph/mass spectrometer. The results show that 70% of naphthalen-1-ol was converted at 160 °C and completely converted at 200 °C for 120 min, and the ISPHTCT was greatly upgraded. A total of 180 organic compounds including 33 nitrogen-containing organic compounds, 11 sulfur-containing organic compounds and 39 oxygenates were identified in ISPHTCT, while no obvious nitrogen-containing organic compounds, sulfur-containing organic compounds and oxygenates were detected in ISPCHCP, indicating the excellent performance of Ni@N-PC for heteroatom removal. All the alkenes, cyclenes and alkynes were saturated and the majority of arenes were converted to cyclanes by catalytic hydroconversion over Ni@N-PC, which exhibited high catalytic hydrogenation activity.
摘要:
镶嵌结构沥青焦作为一种特种人造炭材料,是制备高品质各向同性石墨和核石墨的重要原料。镶嵌结构沥青焦的性质在很大程度上决定了其石墨制品的质量。为进一步明确重相沥青中QI含量对其镶嵌结构沥青焦的结构及性质的影响,本研究以九种QI含量迥异的重相沥青为原料,制备了系列镶嵌结构沥青焦。利用偏光显微镜、扫描电镜、XRD、Raman光谱及分峰拟合的方法对镶嵌结构焦的微观结构进行了判定,并对九种镶嵌结构沥青焦的显微强度进行了研究。结果表明,重相沥青中QI含量越高,在液相炭化过程中越有利于镶嵌结构的生成。并且,随着重相沥青QI含量的增加,镶嵌结构沥青焦中趋于规整炭微晶含量逐渐降低,无定型炭含量逐渐增加,强度越大。当重相沥青中QI含量超过7%时,制备的镶嵌结构沥青焦中镶嵌结构总含量(细粒镶嵌、中粒镶嵌和粗粒镶嵌)超过82%,显微强度超过85%。换言之,QI含量超过7%的重相沥青是生产优质镶嵌结构沥青焦的优选原料。
摘要:
Recently, the disposal of waste by beneficial and environmentally friendly methods has attracted great attention. In this work, we have studied the production of high-value carbon nanotubes (CNTs) which have remarkable applications by catalytic pyrolysis of sugarcane bagasse (SCB) as an agricultural waste using a two-stage process. Various reaction factors including the effects of zeolite types (HZSM-5, HMOR, and HY), pyrolysis temperatures (450−700 °C), and SCB/ZSM-5 ratios (3−12) on SCB pyrolysis were investigated to generate CNTs from pyrolysis products. A Co-Mo/MgO catalyst was used for growing CNTs via the decomposition of pyrolysis products. The morphological structure and quality of CNTs were characterized using TEM and Raman spectroscopy, while the fresh Co-Mo/MgO catalyst was characterized by XRD and TPR analyses. The results showed that zeolite type, pyrolysis temperature, and SCB/ZSM-5 ratio had significant effects on the CNTs yield. The optimum carbon yield (24.9%) was achieved using the HZSM-5 catalyst at the pyrolysis temperature of 500 °C and with the SCB/ZSM-5 ratio of 6. TEM observations confirmed the growth of bamboo-like carbon nanotubes (BCNTs) and carbon nano-onions (CNOs) in different proportions according to the reaction parameters. Also, CNTs with the largest diameter distribution range (7−76 nm) were produced using the SCB/ZSM-5 ratio of 6. Raman spectra demonstrated the production of high-quality CNTs under all studied conditions.
摘要:
利用密度泛函理论和过渡态理论,在分子水平上研究了循环流化床锅炉再燃过程中生物质气CO对CaO催化N2O脱除的影响。构建了N2O分子在CaO(100)表面的吸附模型,同时对N2O分子在CaO(100)表面的分解及还原过程进行了探究。结果表明,N2O在CaO(100)表面的异相分解相比于N2O的均相分解所需的能垒更低,CaO的存在有利于N2O的分解;CaO(100)表面的O活性位点被N2O分解产生的原子O毒化,而再燃过程中生物质气CO促进了CaO(100)表面活性位点的再生,有利于CaO对N2O分解的催化作用。
摘要:
大气中二氧化碳(CO2)浓度的急剧增加引起了人们的关注,并提出了许多将CO2转化为高价值化学品的策略。金属有机框架材料(MOFs)由于其独特的孔隙率、大的比表面积、丰富的孔结构、多活性中心、良好的稳定性和可回收性,可用于二氧化碳的捕获和催化转化。基于晶体多孔材料的金属有机骨架(MOF)设计和合成的各种功能纳米材料可以作为多相催化剂或载体/前体来应对这些挑战。在本文中,笔者将主要关注MOFs在催化二氧化碳加氢领域的最新研究进展,包括催化加氢制备一氧化碳、甲烷、甲酸、甲醇和烯烃,分析了基于MOFs的催化剂的合成方法和提高催化活性的原因。介绍了提高新型MOF材料的催化活性和探索新的CO2转化可行的策略。讨论了MOF型催化剂在CO2化学转化中的主要挑战和机遇,对本研究领域中进一步的发展进行了简要的展望。
摘要:
采用柠檬酸溶胶凝胶法制备了Zn掺杂和Zn-Al共掺杂的La2O3催化剂,运用原位表征技术研究了该催化剂在甲烷氧化偶联(OCM)反应中的构效关系。原位XRD表征结果发现,La2O3晶体在高温下沿c轴发生热膨胀。H2-TPR结果显示,La2O3基催化剂中含有两种类型的氧物种,即强结合氧和弱结合氧;XPS结果表明,强结合氧归属于为O。Zn掺杂的La2O3催化剂在高温下形成更多的氧空位,能活化氧气产生更多的强结合氧,因而在OCM反应中表现出较好的催化性能。Al的共掺杂能促进Zn在La2O3中的分散,进一步增加强结合氧数量,提升OCM反应C2+烃的选择性。
摘要:
Effects of calcium content on the performance of HZSM-5 nanoparticles of 150 nm with Si/Al ratio = 230 in the methanol to olefin conversion were investigated. The parent and modified catalysts showed their largest yields of ethylene and propylene at 490 °C and lower WHSV (= 3.3 h−1). The selectivity for propylene over HZSM-5 was 0.45 at 490 °C whereas it was promoted to 0.51 over Ca27-HZSM-5 (Ca/Al = 27). With decreasing temperature from 490 to 440, and 390 °C, the yield of propylene and ethylene remained nearly constant at 0.13−0.14 and 0.10−0.11 over Ca27-HZSM-5, respectively; more narrow than the corresponding range of yields for HZSM-5 (0.10−0.14 and 0.08−0.12). FT-IR results confirmed the formation of oxygenated and poly alkyl aromatic species in the carbon deposits. TG results indicated that oxygenate coke was formed and converted to heavier poly aromatic coke species with time. Increasing Ca in the porous structure of HZSM-5 may lead to heavier aromatic carbonaceous deposits. In general, Ca content positively affected activity through modification of the density, strength, and accessibility of Brønsted and Lewis acid sites. Long-term MTO activity test of HZSM-5 with Ca/Al = 27 showed stable performance over 100 h, although with an oscillatory feature.
摘要:
采用水热合成法制备了甲醇合成甲缩醛的新型Mo-Sn催化剂。该催化剂可以在低Mo含量时实现甲醇低温氧化高选择性制取甲缩醛。通过考察Mo含量对催化剂结构及甲醇低温氧化制甲缩醛性能的影响,发现Mo1Sn10催化剂在甲醇氧化中表现出了较好的催化性能,在140 ℃、常压反应条件下,甲醇转化率为14.2%,甲缩醛选择性达到了88.9%,并且反应过程中无COx生成。采用XRD、Raman、FT-IR、XPS、NH3-TPD及H2-TPR等表征手段对催化剂进行深入研究。结果表明,不同Mo含量的催化剂结构性能存在着明显的差别,较低含量Mo的存在更有利于Mo5+及MoOx的生成,而由此引起的酸性及氧化还原性的变化是催化剂具有良好性能的重要原因。
摘要:
采用硝酸溶液在不同温度和时间下对钠基蒙脱土进行处理,制备了一系列酸活化蒙脱土(Acid-MMT),并以其为固体酸与商品化的Cu/ZnO/Al2O3物理混合组成双功能催化剂用于二甲醚水蒸气重整(SRD)反应。结果表明,与钠基蒙脱土相比,酸活化蒙脱土的结构、织构及酸性均发生了明显的变化,且变化的程度与酸处理条件密切相关。酸活化蒙脱土的结构和酸性明显影响双功能催化剂的SRD反应性能。其中,在80 ℃处理12 h的酸活化蒙脱土(Acid-MMT-80/12)与Cu/ZnO/Al2O3组成双功能催化剂表现出较好的SRD性能,在p = 0.1 MPa,t = 350 ℃,GHSV = 3000 h−1的反应条件下,二甲醚转化率和氢收率分别达到了97%和94%,且在反应10 h内基本保持不变,表现出了较好的稳定性。
摘要:
The effects of K, Ru or La promoters on the structure, surface area, crystal phase, and catalytic behavior during FT synthesis of carburized and uncarburized fused Fe catalysts were studied by XRD, XPS, TPD, N2-physisorption and catalytic reaction evaluation techniques. Addition of K improved selectivity of C5+ products for both the carburized and uncarburized catalysts. Addition of Ru suppressed catalytic activity of the carburized catalyst, but had little influence on the uncarburized one. Addition of La led to the encapsulation of the iron carbide, which consequently severely inhibited the carburization and decreased the activity. While Ru and La promote the formation of light components due to their ability to promote hydrogen adsorption. The performance of the reaction in the experiment indicated that the U-K catalyst had the best product distribution, in which the methane selectivity was 4.04%, and the C5+ selectivity was 75.84%.
摘要:
为了获得较多高活性II型MoS2活性相,采用四硫代钼酸铵原位热分解法制备了MoS2基催化剂,对比分析了Ni源引入方式和热分解气氛对MoS2活性相微观结构、表面元素化学状态和加氢脱氮脱硫性能等的影响。结果表明,同时引入Mo源和Ni源原位沉淀生成无定形NiMoS4后,再热分解有利于Ni取代MoS2片晶边缘的Mo原子,被修饰后的MoS2片晶保持较高的分散度、适宜的长度(3−5 nm)和堆叠层数(2−4层),从而在边缘暴露较多具有加氢和氢解活性的rim和corner活性位点。热分解气氛H2比N2更有利于Ni在热分解过程中取代MoS2边缘的Mo原子,形成更多II型Ni-Mo-S活性结构,有利于喹啉和二苯并噻吩的吸附活化和加氢反应。当加氢反应温度340 ℃、氢压3 MPa、重时空速23.4 h−1、氢油比为600和使用0.1 g NMS-H2催化剂时,喹啉加氢脱氮转化率达23.8%,二苯并噻吩加氢脱硫转化率达93.3%。
摘要:
The n-hexane was used as a model compound to study the catalytic cracking behavior of light hydrocarbon in HZSM-5 zeolites, and the law of product selectivity of real acid-catalyzed reaction was investigated by analyzing the product distributions. The results showed that no pyrolysis reaction was found at 300 ℃. Only the acid catalytic reaction took place by the mechanism of carbocation, whose activity was positively correlated to the amount of Brønsted (B) acid sites. The selectivity of ethane, ethylene and propane was negatively correlated, while that of propylene was positively correlated with the Si/Al ratios and catalyst to oil ratios, suggesting that low acid density might be more favorable for monomolecular cracking reactions. It was worth nothing that the total selectivity of C4 products was much higher than that of C2 products. Combined with the quantum chemistry calculation results, it could be confirmed that the super-stability of ${{\rm{C}}_{{2}}}{\rm{H}}_{{5}}^ {{+}}$ carbenium ion from the monomolecular cracking of n-hexane made it difficult to produce ethylene and ethane through hydrogen transfer reaction. It’s easier to form a C8 carbenium ion (${{\rm{C}}_{{8}}}{\rm{H}}_{{{19}}}^ {{+}}$) with another n-hexane molecule, and then to generate more C4 products. These results revealed the nature of the low selectivity of ethylene in light hydrocarbon catalytic cracking products. It could be concluded that the product selectivity of catalytic cracking of light hydrocarbons could be modulated by controlling reaction paths depending on the catalyst acid properties and the catalyst to oil ratios. This work will provide important theoretical support for the catalyst design and process development of naphtha catalytic cracking.
摘要:
采用巨正则蒙特卡洛(GCMC)模拟方法研究了CO2、CH4和N2在MER型沸石中的吸附性能,模拟结果与实验结果吻合证明模型和力场是可靠的。在此基础上,以纯硅MER型沸石作为对照,采用分子动力学(MD)模拟方法研究了CO2、CH4和N2在K-MER型沸石中的扩散和分离性能。结果表明,CO2、CH4和N2在MER型沸石中存在亚扩散现象,扩散方式为构型扩散,在沸石三维通道中的扩散存在各向异性。沸石与气体之间的作用力和沸石骨架外阳离子均影响气体分子的扩散能力,而沸石骨架外阳离子是影响气体分子扩散能力的主要因素。CO2和N2的自扩散系数随吸附浓度的增加而减小;CH4的自扩散系数随吸附浓度的增大先增加后减小。CO2、CH4和N2的自扩散系数随温度的升高均增加,扩散活化能大小顺序为N2 (16.51 kJ/mol) > CH4 (8.39 kJ/mol) > CO2 (4.38 kJ/mol)。K-MER型沸石膜对CO2/CH4、CO2/N2和N2/CH4分离体系均有良好的分离选择性。气体分子的渗透率~104 GPU(1 GPU = 3.35×10−10 mol/(s·m2·Pa))。
摘要:
Pt/C, PtBi(95∶5)/C, Pd/C, and PdBi(95∶5)/C were synthesized by the sodium borohydride reducing method to produce metal nanoparticles with advanced electronic properties to enhance the ethanol oxidation reaction (EOR) mechanism. The Transmission Electron Microscopy (TEM) images and X-ray photoelectron spectroscopy (XPS) showed that a small Bi content does not affect the nanoparticle size PdBi/C; in contrast, it does affect the PtBi ones. The X-ray diffraction analysis revealed a lattice parameter modification by Bi dope in Pt crystalline structure. Furthermore, the ATR-FTIR results indicated the suppression of carbonate formation and increment in acetate production. The results of polarization and power density curves on DEFC, the material PtBi/C presented the more high power density, almost six times bigger than Pt/C. PtBi/C also has the highest current density (44 mW/cm2) and the lowest onset potential (−0.6 V) in linear sweep voltammetry experiments. It also has the highest final current density in current-time experiments. Hence, PtBi/C is a very promising electrocatalyst for DEFC.
摘要:
以硝酸钴与硝酸锌为原料,加入尿素和氟化钠在反应釜120 ℃下均匀生长在碳纸上得到Zn-Co(OH)2复合前驱体,通过在室温下用5 mol/L NaOH和1 mol/L Na2S溶液将前驱体刻蚀并部分硫化合成了CoSOH/Co(OH)2复合材料,考察其在电解水析氧反应(OER)中的催化性能。利用XRD、SEM、TEM、XPS对催化剂的微观结构及物理化学性质进行了表征。结果表明,该方法可以刻蚀Zn原子,留下氧空位并引入掺杂S元素,氧空位和S掺杂对OER反应起到积极促进作用。同时,非晶的CoSOH也有较好的OER活性。CoSOH与Co(OH)2的协同作用使得材料表现出最优催化效果(过电位η = 310 mV,塔菲尔斜率b = 90 mV/dec)及长时间的电化学稳定性,具有较高的电催化产氧性能。
摘要:
For the Fe-based catalysts in Fischer-Tropsch synthesis, the reduction and activation process of α-Fe2O3 precursor has a significant effect on the catalytic performance. As a crystalline material, the reduction and activation of α-Fe2O3 is assuredly influenced by the exposed crystal plane; however, there is a lack of necessary research in this regard. In this work, α-Fe2O3 nanocrystals of three different morphologies, viz., pseudo-cubic, hexagonal-plate and rhombohedra, were synthesized, which mainly expose the crystal planes of (102), (001) and (104), respectively. The evolution of α-Fe2O3 crystal structure was then investigated in CO atmosphere by using the Operando Raman spectroscopy (ORS). The results show that the α-Fe2O3 (001) plane has a better reductive activity in comparison to the (104) and (102) planes. The SEM, TEM, XPS and XRD characterization and DFT calculation results reveal that CO2 desorption is a decisive step for the reduction of α-Fe2O3; owing to the weak binding ability of (001) crystal plane to oxygen atoms, the desorption of CO2 on the (001) crystal plane is much easier, which can promote the reduction process.