金属有机骨架结构MIL-101的合成及其吸附脱硫的工艺研究

采用水热合成方法合成金属有机骨架化合物MIL-101,利用X射线粉末衍射(XRD),对其产品表征,并研究提高合成产率的影响因素;以MIL-101做为吸附剂,研究吸附脱除汽油模型油中噻吩的最佳工艺条件。实验结果表明,晶化时间提高到10h,pH值为1.5时,MIL-101的合成产率达到60%,产率比文献值提高10%;在空速150h-1,MIL-101质量为0.075g,噻吩质量分数为1×10-3时,噻吩在正辛烷中的穿透容量为0.69%,饱和吸附量为4.62%;MIL-101和4A分子筛分层装柱,并利用N2在100℃对床层进行活化处理,消除了溶解水对吸附脱硫过程的影响;以甲苯为脱附剂,在100℃,空速为100h-1对吸附剂进行再生处理,再生率为96.38%。     

MIL-101(Cr)开式吸附性能实验

采用水热合成法制备水热稳定金属有机骨架MIL-101(Cr),基于太阳能吸附式空气取水选取不同的实验工况,将MIL-101(Cr)、细孔硅胶作为研究对象,相对湿度控制在50%、温度范围5～45℃条件下,测试并对比了MIL-101(Cr)与细孔硅胶的吸附性能。实验表明,35℃、50%RH条件下,吸附过程进行1000min,MIL-101(Cr)水吸附量为22.05g/100g,其吸附量相比细孔硅胶提高93%左右;当系统平衡时,MIL-101(Cr)有效平均吸附速率相比细孔硅胶提高120%左右。此外,在相对湿度（RH）50%、温度范围5～45℃条件下,MIL-101(Cr)的平衡吸附量在11.40～23.47g/100g之间。在所控温度下,MIL-101(Cr)在25℃时平衡吸附量最大,在5℃时平衡吸附量最小,25℃时MIL-101(Cr)的平衡吸附量相比5℃时提高106%左右。该实验可以为四季工况不同温度下MIL-101(Cr)用于太阳能吸附式空气取水提供基础数据。     

Adsorption equilibrium and the effect of honeycomb heat exchanging device on charge/discharge characteristic of methane on MIL-101(Cr) and activated carbon

Experiments were conducted for developing suitable ANG adsorbents for vehicular applications. MIL^-101 and activated carbon samples were respectively prepared by hydrothermal and chemical activation methods. Two samples were undergone structure analysis on adsorption data of nitrogen at 77.15 K, and adsorption data of methane were then volumetrically measured within temperature-pressure range 293.15 K-313.15 K and 0-8 MPa. A conformable vessel in volume 2.5 L was employed for charge/discharge tests under the flow rate 10-30 L·min^-1. It shows that limit isostreic heat of methane adsorption is respectively about 25.15 kJ·mol^-1 and 22.94 kJ·mol^-1 on the activated carbon and the MIL-101, and isosteric heat within the experimental condition is 14-19.5 kJ·mol^-1; employing a smaller charge/discharge flow rate can weaken the temperature fluctuation of the adsorbent bed and increase the charge/discharge amount; employing honeycomb heat exchanging device enhance the thermal conductivity of the adsorbent bed by consuming a negligible part of volume of the vessel. It suggests that a smaller flow rate for charge/discharge should be employed, and MOFs together with the honeycomb heat exchanging device are promising for practical applications.     

氧化石墨烯/二氧化硅复合材料的制备及吸附性能

以改进的Hummers法制备的氧化石墨烯溶液为原料,十六烷三甲基溴化铵为模板剂,正硅酸乙酯为硅源,采用软模板法制备了氧化石墨烯/二氧化硅复合材料。借助红外光谱仪、扫描电子显微镜、X射线衍射仪对样品的物质结构和微观形貌进行分析表征。以亚甲基蓝模拟染料废水,石墨烯/二氧化硅复合材料为吸附剂,研究其在不同吸附时间、反应温度、ρ(亚甲基蓝)、吸附剂投加量、体系pH值下,对体系吸附量和去除率的影响。结果表明,复合材料出现了C—O—Si的特征峰,说明石墨烯与二氧化硅复合成功;且复合材料在温度为35℃,搅拌时间为90 min,pH=4,ρ(亚甲基蓝)=5 mg/L,投加量为50 mg时吸附性能最好,吸附量为22.75 mg/g,去除率为91%。     

MIL-101Cr-F/Cl用于N2O的捕集研究

氧化亚氮（N₂O）是仅次于CO₂和CH₄的第三大温室气体,对其捕集具有资源回收和减排温室气体的双重价值。本文通过添加氢氟酸和盐酸合成了末端具有不同阴离子的MIL-101Cr材料：MIL-101（Cr）-F和MIL-101（Cr）-Cl,通过XRD、BET、SEM等对样品进行了表征,测试并分析了两种样品对N₂O和N₂的吸附性能,进行了选择性和吸附热的计算以及混合气体的穿透模拟。研究结果表明,MIL-101（Cr）-Cl拥有目前最高的N₂O吸附容量（6.43 mmol/g,298 K）和N₂O/N₂选择性（267）,混合气体（N₂O/N₂=0.1%/99.9%）穿透模拟结果显示MIL-101（Cr）-Cl具有更加优异的微量N₂O捕获能力。     

石墨烯/镍复合微结构表面的池沸腾传热特性

采用电刷镀和表面改性技术,在紫铜表面制备了纯镍微结构（TS1）、亲水性石墨烯/镍复合微结构（TS2）以及疏水性石墨烯/镍复合微结构（TS3）。采用扫描电镜和接触角测量仪分别对三类微结构的表面形貌和润湿性进行了表征;以去离子水为工质,对三类微结构表面的池沸腾传热特性进行了实验研究,发现含有石墨烯的TS2和TS3较TS1的沸腾传热性能均显著改善,其中,TS3具有最大的传热系数和最高的临界热流密度,与TS1相比,其最大传热系数和临界热流密度分别提高了135%和97%。分析表明,TS3具有复杂三维堆叠微结构,疏水性微结构减小了气泡成核的活化能,增加了核化密度,是传热系数提高的主要因素,同时,三维堆叠微结构增加了受热表面的毛细吸液再润湿能力,是临界热流密度提高的主要机理。     

可低温驱动的凝胶复合吸附剂的制备及吸/脱附性能研究

以丙烯酰胺单体、碳纳米管和无水氯化锂为原材料,通过原位聚合法制备了一种新型复合吸附剂,该吸附剂呈水凝胶形式。采用扫描电子显微镜和同步热分析仪对吸附剂进行表征,并用恒温恒湿箱测试了复合吸附剂的动态吸附/解附性能以及平衡吸附性能。研究表明,凝胶复合吸附剂在25℃和75%RH下,平衡吸附量高达1.75 g/g,是硅胶基复合吸附剂的2.5倍以上;并在45℃环境中解吸出70%的吸附水量;采用线性驱动力模型拟合计算了相同工况的动态吸附速率,与国内外其他复合吸附剂相比,本文吸附剂的吸附速率系数和吸附量均有很大提升。     

Multiscale modeling of heat conduction in graphene laminates

We developed a combined atomistic-continuum hierarchical multiscale approach to explore the effective thermal conductivity of graphene laminates. To this aim, we first performed molecular dynamics simulations in order to study the heat conduction at atomistic level. Using the non-equilibrium molecular dynamics method, we evaluated the length dependent thermal conductivity of graphene as well as the thermal contact conductance between two individual graphene sheets. In the next step, based on the results provided by the molecular dynamics simulations, we constructed finite element models of graphene laminates to probe the effective thermal conductivity at macroscopic level. A similar methodology was also developed to study the thermal conductivity of laminates made from hexagonal boron-nitride (h-BN) films. In agreement with recent experimental observations, our multiscale modeling confirms that the flake size is the main factor that affects the thermal conductivity of graphene and h-BN laminates. Provided information by the proposed multiscale approach could be used to guide experimental studies to fabricate laminates with tunable thermal conduction properties.     

氧化铁/石墨烯原位复合物对铬酸钾吸附性能研究

采用共沉淀法制备Fe_3O_4磁性纳米颗粒以及通过原位生长法制备Fe_3O_4与氧化石墨烯的复合物,并加入十六烷基三甲基溴化铵形成共价键交联反应化合物。采用X射线衍射仪和透射电子显微镜表征样品的形貌与尺寸,并以铬酸钾为吸附对象,研究吸附温度、吸附时间和溶液p H值对Fe_3O_4吸附性能的影响。结果表明,椭圆形颗粒的Fe_3O_4尺寸约(10~15)nm,与氧化石墨烯复合后,分散性明显提高;在室温和p H=3.5条件下,以Fe_3O_4与氧化石墨烯的质量比2∶1复合物作为吸附剂对铬酸钾的吸附效果达到最佳,每克的吸附容量可达251 mg;复合物经过磁分离、反复吸附循环实验6次后,对铬酸钾的吸附率仅下降10个百分点。     

Hierarchically structural polyacrylonitrile/MIL-101(Cr) nanofibrous membranes with super adsorption performance for indoxyl sulfate

Excess protein-bound uremic toxins (such as indoxyl sulfate [IS]) in the blood could aggravate chronic kidney disease and also predispose to serious cardiovascular disease. In this study, we constructed a novel IS adsorbent polyacrylonitrile/MIL-101(Cr) (PAN-M) nanofibrous membrane with high adsorption capacity and ultra-fast sorption rate for IS. The porous metal–organic framework MIL-101(Cr) were embedded in PAN nanofibers by electrospinning as an adsorbent for easy recovery. It was found that MIL-101(Cr) had a strong electrostatic effect on the SO₃⁻ of IS and could reach the adsorption equilibrium within 5 min. Notably, MIL-101(Cr) showed an extremely high adsorption capacity (~170 mg/g) for IS. The MIL-101(Cr) loading of prepared PAN-M nanofibrous membrane was optimized at 60 wt% and the optimal PAN-M60 exhibited an appreciable IS adsorption capacity (103 mg/g). The removal of IS was enhanced from 35.4% to 62.5% during hemodialysis by using PAN-M60 as adsorbent immersed in dialysate. This efficient adsorption performance can greatly reduce the consumption of dialysate and may shorten the hemodialysis time. This work would provide a fresh perspective on the development of MOF-based adsorbents to improve hemodialysis therapies.     

多种因素对MIL-101(Cr)选择性吸附水溶液中染料的影响

在多种条件下研究了金属有机框架MIL-101(Cr)对阳离子型染料(亚甲基蓝、罗丹明B)和阴离子型染料(甲基橙、酸性铬蓝K)的吸附性质,主要研究了MIL-101(Cr)对亚甲基蓝和甲基橙的选择性吸附作用。结果表明,中性环境下无论在单组分还是双组分体系中MIL-101(Cr)对阴离子型染料的吸附能力均大于对阳离子型的吸附能力。在pH=3,T=300 K的条件下,选择性系数β可达5.9,但随着pH的增加,选择性系数逐渐降低。相比之下,温度对吸附的选择性影响不大。选择性吸附的机理可以解释为:由于表面带正电荷,MIL-101(Cr)对阴离子型染料产生静电吸引作用;相反,对阳离子型染料的排斥作用而降低了其吸附能力。另外,乙二胺改性提高了MIL-101(Cr)对阴离子型染料的选择吸附性能,而草酸改性降低了选择吸附性。     

氨基化MIL-101表面印迹聚合物的制备及其吸附行为

研究了金属有机骨架材料MIL-101表面印迹聚合物的制备方法及其吸附行为。以MIL-101为载体,先通过化学修饰氨基制备了ED-MIL-101材料,再以京尼平苷为模板,甲基丙烯酸为功能单体,二乙烯基苯为交联剂,表面接枝京尼平苷分子印迹聚合物制备了MIPs@MIL-101印迹聚合物。通过傅里叶红外光谱（FTIR）、X射线衍射光谱（XRD）、扫描电镜（SEM）对聚合物进行结构表征,测试了聚合物的等温吸附及吸附动力学性能,探讨了聚合物的固相萃取性能。红外光谱及XRD衍射分析表明了MIL-101氨基化修饰及表面接枝复合材料的成功制备。吸附动力学研究表明当分子印迹聚合物用于吸附京尼平苷时,可在270min内达到吸附平衡。当温度为298K、308K、318K、328K时,印迹聚合物对模板的吸附量分别为55.94mg/g、46.16mg/g、38.98mg/g、31.47mg/g。吸附热ΔH为26.997kJ/mol。分子印迹固相萃取杜仲提取物中的京尼平苷时,总回收率达95.0%。     

High-quality few layer graphene produced by electrochemical intercalation and microwave-assisted expansion of graphite

Few-layer graphene is synthesized from electrochemically-produced graphite intercalation compounds in aqueous perchloric acid. Although anodic intercalation is more efficient in terms of time, cathodic pre-treatment is preferred to avoid the formation of graphite oxide. The materials are characterized by high resolution transmission electron microscopy and scanning electron microscopy, UV–visible, infrared and Raman spectroscopy. We demonstrate that the method, under the experimental conditions used in this work, does not produce damage to the sp² carbon lattice. The synthetic approach using electrochemical-potential control is very promising to obtain, in a controllable manner, graphene with different degrees of oxidation.     

Direct growth of few layer graphene on hexagonal boron nitride by chemical vapor deposition

Few layer graphene was grown on hexagonal boron nitride single crystal flakes by chemical vapor deposition without using metal catalysts. High quality and thickness controllability of the graphene layers are confirmed by Raman spectroscopy and transmission electron microscopy. Chemical vapor deposition of graphene on this perfect-lattice-matching dielectric substrate offers many advantages including cost effectiveness, easy scalability and compatibility with standard intergraded circuit processes and promises an advance to graphene’s applications in microelectronics and optoelectronics.     

Reinforcement of acrylonitrile butadiene rubber using pristine few layer graphene and its hybrid fillers

Unfunctionalized few layer graphene (FLG) nanoplatelets were mixed with acrylonitrile butadiene rubber (NBR) by melt mixing and the properties were compared with composites containing carbon black alone and a 1:1 mixture of FLG and carbon black. Incorporation of a very small amount of FLG significantly improved the cure characteristics of NBR. Compared to graphene, similar loading of carbon black gave higher rheometer torque at the expense of scorch safety whereas hybrid filler gave optimum cure characteristics. There was more than 190% improvement in tensile strength when 5 phr FLG was added to the matrix. On the other hand, to achieve the same strength, five times more of carbon black was needed compared to FLG. In contrast to carbon black, FLG increased the compression set of the rubber. The compositions containing 1:1 mixture of the fillers displayed compression set values in between those containing FLG or carbon black alone. The storage modulus was also found to be optimum for the composites containing equal amounts of FLG and carbon black. FLG loaded composites displayed significant reduction in the creep compliance. Additionally, the helium leak rate of the composites was decreased in presence of FLG due to its platelet structure.     

氧化石墨烯/水性聚氨酯复合薄膜的制备及性能研究

以自制的GO(氧化石墨烯)为填料,WPU(水性聚氨酯)为基体,采用溶液共混和流延成膜法制备了GO/WPU复合薄膜。着重考察了GO含量对GO/WPU复合薄膜力学性能和导热性能等影响。研究结果表明:随着GO含量的增加,复合薄膜的拉伸强度增强、导热系数增大;当w(GO)=4%(相对于复合薄膜质量而言)时,复合薄膜的拉伸强度(20.6 MPa)相对最大、导热系数[为0.208 W/(m·K)]相对最高[这是由于GO均匀分散在PU(聚氨酯)基体中,形成了连续褶皱状网络结构的缘故]。     

Ag/MIL-101催化剂还原对硝基苯酚反应动力学

采用双溶剂浸渍法制备得到了粒径为1.9nm±0.6nm高分散性的Ag/MIL-101催化剂。考察了该催化剂在过量NaBH₄存在下,还原对硝基苯酚生成对氨基苯酚反应中的催化性能。本文通过研究催化剂浓度、底物浓度和温度对催化活性的影响,获得不同条件下的表观反应速率常数k_app,采用Langmuir-Hinshelwood吸附反应模型对所得动力学数据进行拟合,获得本征反应速率常数k,底物吸附常数K_4-NP和K_BH4,底物吸附焓、熵以及真实活化能E_A,k等热力学参数。研究表明,诱导时间t₀直接与该反应速率控制步骤的反应速率常数k有关。     

乙醇在MIL-101上的吸附相平衡及其吸附机理

主要研究了MIL-101材料对乙醇的吸附性能和吸附机理。采用水热合成法制备了MIL-101(Cr),并分别应用N₂静态吸附、X射线粉末衍射(PXRD)、傅里叶红外光谱(FTIR)等分析手段对MIL-101晶形结构、孔隙结构参数进行分析表征。应用静态吸附法测定乙醇和水蒸气在不同温度下的吸附等温线,并讨论乙醇吸附在MIL-101(Cr) 4种吸附位的机理,根据吸附等温线估算出乙醇和水蒸气在MIL-101上的等量吸附热,并测试了乙醇在MIL-101上的吸附循环性能。研究表明,在298 K下,MIL-101的乙醇吸附容量为20.3 mmol·g^-1,远高于传统吸附材料。在低压下MIL-101对乙醇的吸附量高于水蒸气的吸附量,这是由于乙醇的偶极矩和分子动力学直径均比水大,使得乙醇分子在孔道中受到更大吸附力场作用;在低吸附量范围,乙醇在MIL-101上的等量吸附热要高于水蒸气的等量吸附热。在较高吸附压力条件下,主要发生多层吸附或孔填充,受吸附剂的孔容限制效应,尺寸越大的分子被吸附的物质的量会越少,由于乙醇的动力学直径(0.45 nm)大于水分子的动力学直径(0.268 nm),所以在较高吸附压力下乙醇在MIL-101上吸附量要小于水蒸气的吸附量。多次吸附脱附等温线测试显示MIL-101具有良好的乙醇吸附循环性能。     

乙酸为矿化剂制备MIL-101(Cr)及其CO2吸附研究

以氢氟酸为矿化剂制备金属有机骨架MIL-101(Cr)存在过程繁复、危险系数高的问题。文中改用乙酸为矿化剂,使用X射线衍射、热重分析、扫描电镜、氮气吸附-脱附等表征手段研究了材料的物理结构和形态,并采用固定床评价装置测试比较了样品对CO_2的吸附能力。结果表明:当以1.66 g对苯二甲酸和4 g九水硝酸铬为原料并加入18 mL乙酸时制备的MIL-101(Cr)在25℃,0.1 MPa对CO_2的饱和吸附量达到了130.36 mg/g,是传统制备方法的2.5倍,该结果说明采用适量乙酸为矿化剂同样可以制备出对CO_2吸附性能较好的MIL-101(Cr);并在低于1 MPa的不同吸附压力下,随着吸附压力的升高,MIL-101(Cr)和MIL-101(Cr)-A-18的2种材料对CO_2的吸附饱和时间逐渐延长,饱和吸附量增加,说明了高压有利于2种材料对CO_2的吸附。     

Porous MOFs supported palladium catalysts for phenol hydrogenation: A comparative study on MIL-101 and MIL-53

Two metal organic frameworks (MOFs), chromium benzenedicarboxylates MIL-101 and MIL-53, have been synthesized and used as the support of palladium catalysts. The palladium catalysts were characterized by XRD, TEM, and CO chemisorption. MIL-101 is highly hydrophilic and beneficial as support for fine Pd nanoparticles with an average size of 2.3 nm. Microporous MIL-53 is relatively hydrophobic and larger Pd particles with an average size of 4.3 nm were formed on the external surface. Pd/MIL-101 showed better phenol selective hydrogenation activity to cyclohexanone (> 98%) under mild reaction conditions because of its smaller particle size.