吸附有苯酚氧化残留物的Cu-Ce/AC吸附 催化剂的氢处理研究

对经苯酚吸附和干态催化氧化过程后吸附有苯酚残留物的活性炭载氧化铜和氧化铈(Cu Ce/AC)进行了氢处理研究。结果表明,氢处理可明显促进残留物的分解,恢复Cu Ce/AC对苯酚的吸附性能,减少在后续苯酚氧化过程中苯酚脱附量。氢处理温度越高,苯酚吸附容量恢复得越好。但氢处理不能恢复Cu Ce/AC对苯酚的催化氧化活性,是由于活性组分晶粒长大所致。     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

介孔碳材料CMK-3的合成及其吸附性能研究——介绍一个综合化学实验

介绍一个集物理化学、分析化学和无机化学为一体的综合实验——介孔碳材料CMK-3的合成及其吸附性能研究。实验通过合成具有高比表面积的介孔碳材料CMK-3,运用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和氮气吸附/脱附技术表征材料的形貌和多孔结构;考察了介孔碳材料CMK-3对水溶液中次甲基蓝染料分子的吸附性能。     

有序介孔炭负载铜基催化剂Cu/CMK-3用于气相甲醇氧化羰基化反应（英文）

通过纳米浇铸法合成了有序介孔炭CMK-3,再通过浸渍法制备了Cu/CMK-3催化剂,并将其用于气相甲醇氧化羰基化反应。N_2吸附-脱附测试、X射线衍射(XRD)以及透射电镜(TEM)的表征结果表明,Cu/CMK-3具有序介孔结构,活性Cu物种均匀分散于CMK-3的表面及孔道中,粒径为10～20 nm,远小于相同条件下制备的铜/活性炭(Cu/AC)催化剂。固定床反应器的活性评价结果显示450℃下制备的Cu/CMK-3催化活性最高,反应10 h内碳酸二甲酯(DMC)的时空收率(STY)达到286 mg·g~(-1)·h~(-1),选择性为76%。长周期活性评价结果表明Cu/CMK-3稳定性较相同条件下制备的Cu/AC有大幅提高,50 h内DMC的STY降低了20%,75 h内降低了28%。     

Cu-Ce/AC吸附-催化剂对所吸附苯酚的催化氧化行为的研究

对活性炭载氧化铜和氧化铈（Cu-Ce/AC）吸附 催化剂在连续吸附-催化氧化苯酚循环过程中的催化氧化活性和失活原因进行了研究。结果表明,Cu-Ce/AC的苯酚吸附性能和催化氧化活性随着吸附 催化氧化循环次数的增加而逐渐降低,经5次循环后,苯酚的初始氧化温度提高约25℃。通过对使用过的Cu Ce/ACs进行XPS、ICP分析, 发现Ce和Cu的流失较小,苯酚残留物覆盖表面Ce和Cu是苯酚催化氧化活性降低的主要原因,残留物主要含有C-O-C和C-OH等官能团。     

不同温度烧制介孔碳作为直接甲醇燃料电池催化剂载体

以嵌段共聚物P123为模板制备介孔氧化硅SBA-15, 并以此SBA-15为模板, 以蔗糖为碳源在不同的温度下(600-900 °C)制备介孔碳CMK-3. 采用浸渍还原法, 以硼氢化钠为还原剂, 制备介孔碳载Pt电催化剂, 即20% (w) Pt/CMK-3. 利用循环伏安法(CV)、计时电流法等测试电催化剂对甲醇的催化氧化性能及稳定性. 预吸附单层CO溶出伏安法研究测试催化剂抗CO中毒能力. 结果表明在烧制温度为900 °C时制备的介孔碳载Pt催化剂具有最好的催化性能和稳定性, 而在烧制温度为700 °C时制备的介孔碳载Pt催化剂对CO有较低的溶出电位.     

有序介孔炭负载铜基催化剂Cu/CMK-3用于气相甲醇氧化羰基化反应

通过纳米浇铸法合成了有序介孔炭CMK-3,再通过浸渍法制备了Cu/CMK-3催化剂,并将其用于气相甲醇氧化羰基化反应。N2吸附-脱附测试、X射线衍射(XRD)以及透射电镜(TEM)的表征结果表明,Cu/CMK-3具有序介孔结构,活性Cu物种均匀分散于CMK-3的表面及孔道中,粒径为10~20 nm,远小于相同条件下制备的铜/活性炭(Cu/AC)催化剂。固定床反应器的活性评价结果显示450℃下制备的Cu/CMK-3催化活性最高,反应10 h内碳酸二甲酯(DMC)的时空收率(STY)达到286 mg·g^-1·h^-1,选择性为76%。长周期活性评价结果表明Cu/CMK-3稳定性较相同条件下制备的Cu/AC有大幅提高,50 h内DMC的STY降低了20%,75 h内降低了28%。     

可重复使用的有序介孔碳-氧化钛吸附-光催化剂用于去除水中苯酚

制备了有序介孔碳-氧化钛吸附-光催化剂,利用可见光高效降解水中苯酚.为去除水中高浓度苯酚,设计了吸附-光催化循环,即暗条件吸附8h,分离催化剂和将固体催化剂置于可见光下辐照8h.经过10次循环,水中高浓度苯酚(200mg/L)几乎可被完全降解.详细讨论了TiO₂晶格中非金属掺杂、介孔碳壁对TiO₂纳米颗粒聚集的阻抑作用、介孔孔道吸附苯酚性能等因素对吸附-光催化剂性能的影响.有序介孔碳-氧化钛复合体有效地结合了物理吸附和光化学降解技术,有望用于降解水中难生物降解的高浓度有机污染物.     

超声辅助浸渍法制备高分散Pt/CMK-3-US加氢脱萘催化剂

以CMK-3介孔碳作为载体,分别采用传统浸渍法、超声辅助浸渍法、载体硝酸处理法和表面活性剂辅助浸渍法备了Pt/CMK-3、Pt/CMK-3-US、Pt/CMK-3-HNO_3和Pt/CMK-3-CTAB催化剂,并通过表征和催化性能评价进行研究。表征方法包括XRD、BET、SEM、TEM和H2-TPR,结果表明Pt/CMK-3中Pt分散性最差,Pt/CMK-3-HNO_3和Pt/CMK-3-CTAB中Pt的分散度较好,但是HNO_3对介孔碳的孔道结构有破坏作用,且Pt/CMK-3-HNO_3和Pt/CMK-3-CTAB中的介孔碳的表面性质具有明显变化,只有超声法可以在很好地保持CMK-3的孔道结构和表面性质的基础上提高铂的分散度,Pt的粒径在3 nm左右。萘加氢催化性能评价结果表明Pt/CMK-3-US的催化加氢活性及产物选择性高于Pt/CMK-3,且明显高于Pt/CMK-3-HNO_3和Pt/CMK-3-CTAB。萘转化率可以达到98%以上,十氢萘选择性可以达到95%以上。     

有序介孔碳CMK-3的化学活化及储氢性能

选用KOH、NaOH、H3PO4对有序介孔碳CMK-3进行了活化,通过X射线衍射、低温氮吸附-脱附等对样品进行了表征,发现活化后样品的结构发生了巨大的变化。有序介孔碳CMK-3的有序性逐渐降低,比表面积明显增大,2 nm介孔明显增多。讨论了CMK-3和KOH质量比、活化温度、不同活化剂对活化效果的影响。储氢测试表明活化能够明显提高CMK-3的储氢性能,77K、100 kPa时的储氢性能高达2.32wt%。     

Adsorption of U(VI) from aqueous solution by sulfonated ordered mesoporous carbon

The sulfonated mesoporous carbon (CMK-3-SO₃H) prepared by functionalizing mesoporous carbon (CMK-3) via vapor transfer method has been explored for the removal and recovery of uranium from aqueous solutions. The influences of different experimental parameters such as solution pH, initial concentration, contact time and temperature on adsorption were investigated. The results showed that CMK-3-SO₃H has the highest uranium sorption capacity at initial pH of 5.0 and contact time of 120 min, and the adsorption process could be better described by the pseudo-second-order model and Langmuir isotherm. Selective adsorption studies showed that the CMK-3-SO₃H could selectively remove of U(VI), and the selectivity coefficients of mesoporous carbon in the presence of co-existing ions, Mg(II), Zn(II), Mn(II), Cu(II), Ni(II), Sr(II) and Hg(II) improved after functionalization.     

In situ introduction of dispersed metallic Ag nanoparticles into the channels of mesoporous carbon CMK-3

An in situ reduction method has been developed to fabricate metallic Ag nanoparticles inside the channels of mesoporous carbon CMK-3.This approach combines function of the CMK-3 surface by oxidation using HNO_3 with the subsequent absorption of Ag~ . The resultant nanocomposite materials were characterized by nitrogen adsorption,X-ray diffraction,Auger electron spectroscopy and transmission electron microscopy.Compared with the conventional impregnation method,our approach shows that Ag nanoparticles of 2-4 nm can be uniformly incorporated into CMK-3.     

有序介孔碳CMK-3负载金纳米微粒复合材料的制备和表征

分别采用等体积浸渍-甲醛还原、等体积浸渍-氢气还原及溶胶负载法在介孔碳CMK-3上负载金纳米微粒;利用透射电镜和粉末X射线衍射仪对比分析了采用3种方法得到的复合材料的微结构和相组成;并测定了采用溶胶负载法得到的不同金含量的复合材料的热稳定性.结果表明,所制备的金纳米微粒的尺寸因制备方法不同而呈现明显差异;负载于复合材料中的金纳米微粒具有很好的热稳定性.     

电化学方法制备高分散Pt/CMK-3及其对甲醇电化学催化性能

采用直接电化学还原法在介孔碳(CMK-3)载体上直接电沉积高分散的铂纳米颗粒,制备CMK-3复合铂纳米颗粒电极(Pt/CMK-3)。 通过透射电子显微镜分析发现,铂纳米颗粒非常均匀的分布在CMK-3上,平均粒径约5 nm。 通过循环伏安测试,分析了催化剂不同负载铂含量时氯铂酸的利用率,在理论铂质量分数为20%时,这种方法制备的Pt/CMK-3所使用的氯铂酸的利用率最高,在1 mol/L CH3OH+0.5 mol/L H2SO4溶液中循环伏安测试电流密度达到382 A/g。 在相同实验条件下,Pt/CMK-3电极对甲醇电催化活性远高于Pt/XC-72(炭黑)电极和用常规电沉积方法制备的Pt/CMK-3电极。     

Sequestration of CO2 using Cu nanoparticles supported on spherical and rod-shape mesoporous silica

The CO₂ sequestration is one of the most promising solutions to tackle global warming. In this study, spherical mesoporous silica particles (MPS-S) and rod-shaped mesoporous silica particles (MPS-R) loaded with Cu nanoparticles were selectively prepared and employed for CO₂ adsorption. For the first time uniform Cu nanoparticles were incorporated into the rod-shaped mesoporous silica particles by post-synthesis modification using both N-[3-(trimethoxysilyl)propyl]ethylenediamine (PEDA) and ethylenediamine (EDA) as coupling agents. The physiochemical properties of the mesoporous and copper grifted silica composites were investigated by CHN elemental analysis, FTIR spectroscopy, thermogravimetric analysis, X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), surface area analysis, scanning, transmission electron microscopy and gas analysis system (GSD 320, TERMO). The mesoporous silica shows highly ordered mesoporous structures, with the rod-shaped particles having a higher surface area than the spherical ones. Copper nanoparticles with an average diameter of 6.0 nm were uniformly incorporated into the MPS-S and MPS-R. Moreover, Cu-loaded mesoporous silica exhibits up to 40% higher CO₂ adsorption capacity than the bare MPS. The MPS-R modified with Cu nanoparticles showed a maximum CO₂ adsorption capacity of 0.62 mmol/g and the humidity showed a slight negative effect on CO₂ uptake process. The enhancement of CO₂ adsorption onto transition metal/mesoporous substrates provides basis for imminent CO₂ sequestration.     

介孔碳负载铂催化剂的分散性和电催化活性

以介孔硅SBA-15为模板, 糠醇为碳源制备了高度有序的介孔碳(CMK-5), 并用微波法合成碳负载的铂纳米粒子的催化剂. 为改善铂微粒的分散性能, 在微波碳载过程中添加了适量的阳离子表面活性剂(CTAB). XRD和TEM测试结果表明, CTAB的加入改善了铂催化剂的分散性, 且使铂微粒的平均粒径降至2.9 nm左右. 循环伏安测试结果显示, 加入CTAB后所得Pt/CMK-5催化剂的电化学活性面积大于未加CTAB的以及商业Johnson Matthey公司的Pt/C催化剂的活性面积.     

Novel coassembly route to Cu-SiO2 MCM-41-like mesoporous materials

A series of mesostructured Cu-SiO2 composites have been synthesized with sodium metasilicate (Na2SiO3) and cuprammonia nitrate (Cu(NH3)4(NO3)2) respectively used as Si and Cu sources. The synthetic procedures were conducted at room temperature, and cetyltrimethylammonia bromide was used as a template. Under our experimental conditions, ordered mesoporous Cu-SiO2 composites could be obtained with a copper content up to 16.8 wt %. Average pore diameters (2.80-3.15 nm), wall thickness (1.30-2.20 nm), and specific surface area (1020-690 m2/g) are found to vary linearly with copper content (0-16.8 wt %). Results of thermal gravimetry-differential thermal analysis reveal the collapse temperature of the order structure starts at approximately 1250 K for mesoporous Cu-SiO2 with 16.8 wt % copper content. As indicated by the outcomes of inductively coupled plasma and X-ray photoelectron spectroscopy studies, copper is mainly incorporated inside the pore wall rather than embedded on the wall surface. Copper species strongly interact with silica, and calcination at high temperatures cannot cause phase separation between silica and copper oxide. Cu status in mesoporous Cu-SiO2 composites is similar to that in copper silicate in neighboring structures. Based on the results, a S+ I- I+ I- mechanism is proposed in which copper entities are surrounded by silicon species during synthesis of the mesostructured composite.     

Effect of size of catalytically active phases in the dehydrogenation of alcohols and the challenging selective oxidation of hydrocarbons

The size of the active phase is one of the most important factors in determining the catalytic behaviour of a heterogeneous catalyst. This Feature Article focuses on the size effects in two types of reactions, i.e., the metal nanoparticle-catalysed dehydrogenation of alcohols and the metal oxide nanocluster-catalysed selective oxidation of hydrocarbons (including the selective oxidation of methane and ethane and the epoxidation of propylene). For Pd or Au nanoparticle-catalysed oxidative or non-oxidative dehydrogenation of alcohols, the size of metal nanoparticles mainly controls the catalytic activity by affecting the activation of reactants (either alcohol or O(2)). The size of oxidic molybdenum species loaded on SBA-15 determines not only the activity but also the selectivity of oxygenates in the selective oxidation of ethane; highly dispersed molybdenum species are suitable for acetaldehyde formation, while molybdenum oxide nanoparticles exhibit higher formaldehyde selectivity. Cu(II) and Fe(III) isolated on mesoporous silica are highly efficient for the selective oxidation of methane to formaldehyde, while the corresponding oxide clusters mainly catalyse the complete oxidation of methane. The lattice oxygen in iron or copper oxide clusters is responsible for the complete oxidation, while the isolated Cu(I) or Fe(II) generated during the reaction can activate molecular oxygen forming active oxygen species for the selective oxidation of methane. Highly dispersed Cu(I) and Fe(II) species also function for the epoxidation of propylene by O(2) and N(2)O, respectively. Alkali metal ions work as promoters for the epoxidation of propylene by enhancing the dispersion of copper or iron species and weakening the acidity.     

Cu‐Based Nanoparticles as Emerging Environmental Catalysts

This account provides an overview of current research activities on nanoparticles containing the earth‐abundant and inexpensive element copper (Cu) and Cu‐based nanoparticles, especially in the field of environmental catalysis. The different synthetic strategies with possible modification of the chemical/ physical properties of these nanoparticles using such strategies and/or conditions to improve catalytic activity are presented. The design and development of support and/or bimetallic systems (e. g., alloys, intermetallic, etc.) are also included. Herein, we report synthetic approaches of Cu and Cu‐based nanoparticles (monometallic copper, bimetallic copper and copper (II) oxide nanoparticles/nanostructures) and impregnation of such nanoparticles onto support material (e. g., Co₃O₄ nanostructure), along with their applications as environmental catalyst for various oxidation and reduction reactions. Finally, this account provides necessary advances and perspectives of Cu‐based nanoparticles in the environmental catalysis.