二价铬/钼/镍空配位MOFs的CH_4/N_2吸附分离研究

基于金属有机骨架材料中金属空配位对气体的强吸附作用,利用具有较高活性的二价金属Cr~(2+)/Mo~(2+)/Ni~(2+)与均苯三酸(H_3BTC)配位合成了HKUST-1(Cu-BTC)同构系列材料M-BTC(M=Cr、Mo、Ni),并与Cu-BTC对比分析了该类型材料中不同金属空配位对甲烷和氮气的吸附性能。实验结果显示,此三种材料均具有较好的甲烷选择吸附性,其中含Ni~(2+)金属空位的Ni-BTC以其尤为突出的甲烷吸附热值而呈现较好的CH_4/N_2分离潜力;Cr~(2+)空配位虽具有较强活性,但是对于甲烷的选择性吸附性能却低于含Cu~(2+)空位的Cu-BTC材料。结合吸附选择性IAST计算分析得到此三种含较高活性不饱和金属空配位的MOFs材料对于甲烷选择性吸附作用能顺序为:Ni-BTCMo-BTCCu-BTCCr-BTC。     

聚丙烯酸改性凹土对Pb2+、Ni2+和Cr3+的选择性吸附

通过凹土的表面功能化开发高性能低成本的吸附材料,采用溶液聚合法在其表面接枝聚丙烯酸,制备出聚丙烯酸/凹土吸附材料(PAA/ATP),系统考察了PAA/ATP对Pb²⁺、Ni²⁺和Cr³⁺三元混合体系的吸附性能。结果表明:PAA/ATP复合吸附材料的有机物接枝率为14.1%,其结构中出现聚丙烯酸的特征官能团;PAA/ATP吸附Pb²⁺的动力学符合拟二级动力学,即化学吸附是速率控制步骤,说明PAA/ATP对Pb²⁺的吸附是一个有化学作用的过程,吸附过程与Pb²⁺和吸附剂PAA/ATP表面官能团之间的电子转移或电子共用有关;PAA/ATP对Pb²⁺的吸附符合Langmuir吸附等温模型;PAA/ATP对Pb²⁺、Ni²⁺和Cr³⁺的竞争吸附能力依次为Pb²⁺ > Cr³⁺ > Ni²⁺,即对Pb²⁺具有较好的选择性吸附。     

量子化学计算在环境纳米技术教学中的应用

以电镀废水中金属污染物离子的吸附为例,展示了如何在硕士研究生课程“环境纳米技术”中引入量子化学计算的知识,介绍其在材料筛选及吸附作用机理研究中的具体实践。通过金属离子Cr³⁺、Cu²⁺、Ni²⁺、Zn²⁺与配位剂CN^-离子在石墨烯及改性石墨烯表面吸附的教学实例,说明了吸附材料的前线分子轨道会影响吸附效果。Cu²⁺与Cu⁺以及Fe³⁺与Fe²⁺两组离子的吸附行为表明高价金属离子在碳材料表面具有更高的吸附能,这为筛选适宜碳材料进行单一离子选择性吸附提供了理论指导。将量子化学计算引入研究生课堂教学环节有助于提升学生的创新思维与创新能力,学会运用计算化学手段高效地设计实验,筛选适合于具体应用的功能材料,并更直观地开展机理研究。     

CrO x /Ti-Al2O3催化剂结构及其催化丙烷脱氢性能

以模板法制备的Ti改性Al₂O₃为载体制备了CrO _x /nTi-Al₂O₃催化剂,考察了Ti含量对催化剂的结构及其催化丙烷脱氢性能的影响。采用X射线衍射（XRD）、N₂吸附-脱附、透射电子显微镜（TEM）、傅里叶变换红外光谱（FTIR）、拉曼光谱、X射线光电子能谱（XPS）、氨气程序升温脱附（NH₃-TPD）、吡啶红外吸附（Py-IR）等方法对催化剂的结构进行了表征。结果表明,CrO _x /nTi-Al₂O₃催化剂具有均匀的泡沫状介孔结构并含有少量微孔,表面积在180~195m²/g;铬主要以Cr⁶⁺和Cr³⁺形式存在,其中Cr⁶⁺主要以单铬酸盐和双铬酸盐形式存在,Cr³⁺以α-Cr₂O₃晶体和高分散Cr₂O₃形式存在,Ti的加入降低了催化剂表面Cr⁶⁺含量,增加了孔道内高分散Cr³⁺含量;Ti的加入降低了弱酸的强度,生成了少量中强酸,并使催化剂中B酸和L酸中心数量明显减少。少量的Ti（0.5%~1.0%TiO₂,质量分数）可明显提高丙烷转化率和丙烯收率,但过多的Ti（>2%TiO₂）则明显降低丙烯选择性而使丙烯收率降低。CrO _x /nTi-Al₂O₃催化剂表面Cr⁶⁺物种可催化丙烷氧化脱氢,本身还原成Cr³⁺后继续催化丙烷直接脱氢,孔道内部的高分散Cr³⁺可催化丙烷直接脱氢反应,二者结合使催化剂保持了较高的催化活性和较好的稳定性。     

Ni2+掺杂对MgCr2O4材料红外辐射性能的影响

开发高发射率红外辐射材料是高温窑炉节能的重要方向。本工作采用高温固相反应工艺制备Ni²⁺掺杂MgCr₂O₄材料,研究了Ni²⁺掺杂量摩尔分数对MgCr₂O₄材料红外辐射性能的影响,探讨了影响MgCr₂O₄材料红外发射率的机理。结果表明,Ni²⁺能掺杂进入MgCr₂O₄材料晶格,所制备的Mg_1–x Ni_xCr₂O₄(0.1≤x≤0.5)材料产生了晶格畸变,少量Ni²⁺价态发生转变;同时,随着Ni²⁺掺杂量增加,氧空位浓度的增大,禁带宽度减小,所制备材料在近中红外波段的发射率均有提高。x=0.5的材料(Mg_0.5Ni_0.5Cr₂O₄)在...     

钢渣对Ni2+与Cu2+的竞争吸附研究

将转炉钢渣磨碎筛分,从钢渣投加量、吸附时间、酸性条件等方面探究其对水溶液中Ni²⁺的吸附性能及吸附机理,并讨论Cu²⁺对钢渣吸附Ni²⁺的影响。研究结果表明,100 mL浓度为50 mg·L^-1的Ni²⁺溶液,用200目(0.074 mm)0.15 g的钢渣处理30 min,Ni²⁺的吸附率为99.88%。钢渣吸附Ni²⁺的过程符合准二级动力学模型和Freundlich等温模型。钢渣吸附Cu²⁺与吸附Ni²⁺属于竞争吸附,且钢渣对Cu²⁺的吸附能力优于对Ni²⁺的吸附能力。钢渣吸附Ni²⁺的过程以化学吸附为主,伴随着物理吸附,且随着钢渣表层吸附位点的减少,钢渣对Ni²⁺的物理吸附作用会逐渐减弱。该研究对处理工业含Ni²⁺与Cu²⁺的废水具有一定的指导意义。     

不同变质程度超微煤粉对重金属离子的吸附性能

重金属离子由于具有毒性、难以生物降解且可在生物体内累积,严重威胁人类的身体健康。吸附是去除重金属离子的一种可行有效的方法。本文选择褐煤、烟煤、无烟煤3种变质程度不同的煤种,通过高能球磨获得超微煤粉。研究了3种超微煤粉对水溶液中Ni²⁺和Cr⁶⁺的吸附动力学与热力学以及投加量与pH值对吸附效果的影响。结果表明3种煤粉对Ni²⁺、Cr⁶⁺的吸附量均随时间的增加而增加,并且Ni²⁺的处理效果明显好于Cr⁶⁺,在180min时褐煤、无烟煤与烟煤对Ni²⁺、Cr⁶⁺的吸附量分别为3.906mg/g、3.582mg/g、2.983mg/g和1.953mg/g、1.774mg/g、0.487mg/g。3种煤粉对两种重金属离子的吸附均符合二级吸附动力学和Freundlich等温式,随着投加量与pH值的增加,去除效果增加,在相同条件下,褐煤的吸附效果优于烟煤与无烟煤。     

Mn/Cu-BTC催化剂同时脱硫脱硝实验研究

通过水热合成法制得金属有机骨架材料Cu-BTC,采用浸渍法将金属氧化物（Fe、Mn、Ce、Co、Mo）负载在Cu-BTC上得到复合催化剂（X/Cu-BTC）并用于同时脱除模拟烟气中的SO₂和NO。采用N₂物理吸附（BET）、X射线衍射分析（XRD）、热重分析（TG）以及扫描电镜（SEM）等方法对催化剂进行表征。表征结果显示MnO_x的负载使得催化剂的比表面积、孔体积下降,负载前后催化剂的结构保持不变。同时考察了不同金属氧化物负载Cu-BTC同时脱硫脱硝的效果：Mn/Cu-BTC的脱硝最佳,其次为Ce/Cu-BTC。最后对MnO_x与CeO_x的负载量进行了考察,10% Mn/Cu-BTC与10% Ce/Cu-BTC为最佳负载量。在250℃,空速为10000h^-1时,10% Mn/Cu-BTC的脱硫和脱硝效率分别为100%和88%,10% Ce/Cu-BTC的脱硫和脱硝效率分别为100%和75%,表明Mn/Cu-BTC催化剂对于SO₂和NO具有良好的同时脱除效果。     

改性含铝废渣对水中重金属镍的吸附行为

采用Ca(OH)₂对含铝废渣(RAS)进行改性,制备改性含铝废渣(MAS),考察MAS对重金属镍的吸附效果,并利用FT-IR、比表面积分析仪、SEM、XRF等对MAS的结构、形貌进行表征。结果表明：经Ca(OH)₂改性制备的MAS对Ni²⁺的去除效果优于其他吸附材料;在25℃时,当MAS投加量为1.0 g、Ni²⁺初始质量浓度为40 mg/L、pH=5、吸附时间为40 min时,MAS对Ni²⁺的平衡吸附量为3.983 mg/g,Ni²⁺去除率为99.65%,达到《铜、镍、钴工业污染物排放标准》(GB 25467—2010)的排放要求(总镍<0.5 mg/L)。MAS对Ni²⁺的吸附符合二级动力学规律和Langmuir等温吸附模型。Weber-Morris内扩散模型说明,MAS对Ni²⁺的吸附是由膜扩散和内扩散共同控制的。改性后的MAS相较于RAS颗粒更细、比表面积更大、孔径分布更广,对Ni^2+<...     

改性含铝废渣对废水中镍的吸附机理和动力学影响

采用Ca(OH)₂对含铝废渣(RAS)进行改性，制备改性材料(MAS)，对其结构进行表征，并考察其对Ni²⁺的吸附机理和性能影响。结果表明：Ca(OH)₂的引入没有改变RAS的主要官能团，其主要组分为CaTiO₃、FeAl₂O₄和Fe₃O₄，而且改性后的MAS对Ni²⁺的吸附速率由膜扩散和内扩散相互作用，吸附过程是自发吸热过程。     

CH4-N2在MOFs结构材料中的吸附分离性能

针对甲烷氮气的分离难题,通过溶剂热法大量合成了6种典型的由单齿、多齿与多元配体构建的金属有机框架材料,并利用单组分静态与双组分动态吸附法分别研究了甲烷与氮气在材料中的吸附行为。研究结果表明,MOFs材料相对较弱的极性,致使其甲烷氮气的分离选择性明显优于Si/Al分子筛;多齿配体MOFs材料因配体较长,孔道较大,具有与活性炭相当的甲烷氮气分离选择性;MOFs中的不饱和金属位增大了孔道极性,不利于分离性能的提高;单齿甲酸配体构建的超微孔[Ni₃(HCOO)₆]框架具有非常优异的CH₄/N₂分离性能,其选择性高达7.0,是Si/Al分子筛与活性炭的2倍。这为高效甲烷氮气分离材料的设计提供了新的参考依据。     

Boosting selective C2H2/CH4, C2H4/CH4 and CO2/CH4 adsorption performance via 1,2,3-triazole functionalized triazine-based porous organic polymers

Nitrogen-rich porous organic polymers have shown great potentials in gas adsorption/separation, photocatalysis, electrochemistry, sensing and so on. Herein, 1,2,3-triazole functionalized triazine-based porous organic polymers (TT-POPs) have been synthesized by the copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) polymerization reactions of 1,3,5-tris(4-azidophenyl)-triazine with 1,4-diacetylene benzene and 1,3,5-triacetylenebenzene, respectively. The characterizations of N₂ adsorption at 77 K show TT-POPs possess permanent porosity with BET surface areas of 666 m²·g^-1 (TT-POP-1) and 406 m²·g^-1 (TT-POP-2). The adsorption capacities of TT-POPs for CO₂, CH₄, C₂H₂ and C₂H₄, as well as the selective separation abilities of CO₂/N₂, CO₂/CH₄, C₂H₂/CH₄ and C₂H₄/CH₄ were evaluated. The gas selective separation ratio of TT-POPs was calculated by the ideal adsorbed solution theory (IAST) method, wherein the selective separation ratios of C₂H₂/CH₄ and C₂H₄/CH₄ of TT-POP-2 was 48.4 and 13.6 (298 K, 0.1 MPa), which is comparable to other adsorbents (5.6-120.6 for C₂H₂/CH₄, 10-26 for C₂H₄/CH₄). This work shows that the 1,2,3-triazole functionalized triazine-based porous organic polymer has a good application prospect in natural gas purification.     

AC/X-G吸附剂的制备及CH4/N2吸附分离性能

采用浓度为0.2g·ml^-1的葡萄糖溶液对13X沸石/活性炭复合材料(AC/X)进行碳沉积,研究沉积次数对复合吸附剂(AC/X-G)孔结构、表面性质和CH₄/N₂吸附分离性能的影响。通过X射线衍射,77K下的N₂吸附/脱附,扫描电镜,CO₂-TPD以及红外光谱表征样品的晶型、孔结构和表面性质,在298K、100kPa下对其CH₄和N₂吸附等温线进行测定,并将吸附结果与文献中碳材料和13X沸石的吸附性能进行比较。结果表明:随着沉积次数的增加,AC/X-G吸附剂中X型沸石的相对含量降低,微孔比表面积和微孔体积减少。AC/X-G的表面被碳膜覆盖,碱量降低,但出现强碱位和含氧基团C-O键。AC/X-G的CH₄和N₂吸附量下降,但吸附分离系数提高,沉积3次的样品AC/X-G-3的CH₄/N₂吸附分离系数达到3.0,表面的含氧基团有利于提高复合材料的CH₄/N₂吸附分离性能。     

Effect of pore size on CH4/N2 separation using activated carbon

In this paper, a model of activated carbon was established by molecular simulation and the separation performance of N_2 and CH_4 on activated carbon was studied. In order to evaluate the adsorption selectivity and diffusion selectivity of N_2 and CH_4, Grand Canonical Monte Carlo and molecular dynamic methods were used to obtain equilibrium adsorption isotherms and mean square displacements of N_2 and CH_4 on activated carbon with different pore sizes. Research results showed that the difference in adsorption isosteric heat of N_2 and CH_4 at the pore size of 0.46 nm is the largest, which is 5.759 and 7.03 kcal·mol~(-1)(1 cal=4.184 J), respectively. Activated carbon with pore size of 0.46 nm has the best N_2 and CH_4 adsorption selectivity, while its diffusion selectivity is not obvious.     

一维直孔道MOFs对CH4/N2和CO2/CH4的分离

非常规天然气未来可以作为常规天然气的有效补充,其中低浓度煤层气和生物质燃气分别需要脱除大量的N₂ 和CO₂以达到富集和纯化CH₄的目的。本研究针对CH₄/N₂这一对较难分离的气体组合,选取了具有一维菱形孔道的MOFs材料Cu(INA)₂作为吸附剂,将合成的样品做了XRD和TG表征,测试了纯气体CO₂、CH₄和N₂的吸附曲线,利用巨正则系综蒙特卡罗(GCMC)分子模拟和理想吸附溶液理论(IAST)计算了气体的吸附热和该材料对于CH₄/N₂和CO₂/CH₄的吸附选择性系数;3 MPa压力下制备的颗粒样品填装吸附分离装置,进行了混合气体CH₄/N₂ (50%/50%)和CO₂/CH₄ (50%/50%)的穿透试验,分离的结果显示,Cu(INA)₂不仅高选择性地吸附CH₄/N₂混合物中的CH₄(S_CH4/N2=10),而且对CH₄/N₂的分离效果优于CO₂/CH₄。     

In situ XPS investigations of Cu1−xNixZnAl-mixed metal oxide catalysts used in the oxidative steam reforming of bio-ethanol

A series of CuNiZnAl-multicomponent mixed metal oxide catalysts with various Cu/Ni ratios were prepared by the thermal decomposition of Cu_1−xNi_xZnAl-hydrotalcite-like precursors and tested for oxidative steam reforming of bio-ethanol. Dehydrogenation of EtOH to CH₃CHO is favored by Cu-rich catalyst. Introduction of Ni leads to CC bond rupture and producing CO, CO₂ and CH₄. H₂ yield (selectivity) varied between 2.6–3.0 mol/mol of ethanol converted (50–55%) for all catalysts at 300 °C. The above catalysts were subjected to in situ XPS studies to understand the nature of active species involved in the catalytic reaction. Core level and valence band XPS as well as Auger electron spectroscopy revealed the existence of Cu²⁺, Ni²⁺ and Zn²⁺ ions on calcined materials. Upon in situ reduction at reactions temperatures, the Cu²⁺ was fully reduced to Cu⁰, while Ni²⁺ and Zn²⁺ were partially reduced to Ni⁰ and Zn⁰, respectively. On reduction, the nature of ZnO on Cu-rich catalyst changes from crystalline to amorphous, relatively inert and highly stabilized electronically. Relative concentration of the Ni⁰ and Zn⁰ increases upon reduction with decreasing Cu-content. Valence band results demonstrated that the overlap between 3d bands of Cu and Ni was marginal on calcined materials, and no overlap due to metallic clusters formation after reduction. Nonetheless, the density of states at Fermi level increases dramatically for Ni-rich catalysts and likely this influences the product selectivity.     

国外渣油加氢技术研究进展

随着原油劣质化趋势的加剧及环保法规的日益严格,渣油加氢技术已成为炼厂提高轻油收率的关键技术。本文针对目前主要的渣油加氢技术,比较了固定床、沸腾床、悬浮床、移动床四大类型渣油加氢技术的优势和不足,重点分析了国外主要的渣油加氢技术的研究进展,探讨了未来的发展趋势。固定床加氢技术最成熟,在可预见的未来仍将占据渣油加氢的主导地位;沸腾床加氢技术日趋成熟,代表未来渣油加氢的发展方向;移动床加氢技术暂不作为渣油加氢的有效手段;悬浮床加氢技术尚未实现工业化应用,正在建设多套工业装置,具有良好的发展前景。渣油加氢技术与其他重油加工工艺进行优化集成,将会显著提高炼厂的经济效益。     

Characterization and photocatalytic activity of transition-metal-supported surface bond-conjugated TiO2/SiO2

TM/TiO₂/SiO₂ photocatalysts were prepared by the photodeposition method using transition metal salts (TM=Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺) as precursors and the surface bond-conjugated TiO₂/SiO₂ as supporter in N₂ atmosphere, and were characterized by XRD, XPS, UV-Vis diffuse reflection and zeta-potential. Their photocatalytic activities were evaluated using reactive brilliant red K-2G (K-2G) and cationic blue X-GRL (CBX) showing different adsorption behavior on the oxides. Fe, Cu supported TiO₂/SiO₂ can efficiently extend the light absorption to the visible region. XPS analysis verified that the introduction of transition metal lead to the changes of the electronic environmental of Ti cations and the zeta-potential of oxides. As a result, K-2G has higher adsorption on the modified TiO₂/SiO₂ than that on the baked one, while the adsorption of CBX has a little change on the both oxides. At the same time, for the photodegradation of K-2G, Fe³⁺, Co²⁺, Ni²⁺-modified catalysts show that their photoactivities are 3.3–2.2 times higher than the bare one. On the contrast, all transition-metal-supported catalysts have no significant activity improvement except that Fe/TiO₂/SiO₂ shows 1.68 times higher activity for the photodegradation of CBX. The results indicate that the photoactivity could be increased in photodegradation of dyes by changing the performances of adsorption to dyes and absorption to light of photocatalyst.