VO@g-C_3N_4-T高效可见光催化苯羟基化制苯酚

以尿素和乙酰丙酮氧钒为原料,将乙酰丙酮氧钒络合在纳米薄片石墨化氮化碳上,得到系列不同V质量分数的光催化剂(VO@g-C_3N_4-T),将其与石墨化氮化碳(g-C_3N_4)、钒氧化合物负载在石墨化氮化碳上得到的催化剂(VO/g-C_3N_4)进行了催化苯羟基化的性能对比。采用N2吸附-脱附、X射线衍射光谱(XRD)、傅里叶变换红外光谱(FTIR)、扫描电镜(SEM)、能谱(EDS)、电感耦合等离子体-原子发射光谱(ICP-AES)对制备的催化剂进行了表征。考察了所得催化剂可见光下催化苯羟基化制苯酚的性能。结果表明,高比表面积、纳米薄片状的VO@g-C_3N_4-T催化剂具有合适的带差,对可见光下催化苯的C—H活化及羟基化具有较好的催化性能,苯的转化率和苯酚选择性分别可以达到98.4%、91.1%。由于石墨化氮化碳和钒具有较强的相互作用,减少了钒的溶脱,所以该催化剂具有很好的可重复使用性,连续使用5次后,苯的转化率和苯酚的选择性仍然可以达到97.1%和91.0%。     

光催化苯羟基化制苯酚研究进展

苯酚是一种重要的有机化工基础原料,应用广泛。近年来,随着苯酚需求量的增加和生产苯酚的主流工艺——异丙苯法与可持续发展的理念冲突,越来越多的研究者将目光投向苯直接羟基化制苯酚。主要从吸收波长范围在紫外光区和可见光区催化剂的角度介绍光催化苯直接羟基化氧化制苯酚的研究进展,当前光催化苯制苯酚研究中,钒氧化物催化剂和贵金属催化剂活性组分易流失,钒氧化物催化剂寿命短,纳米金催化剂活性衰减快,铁系物催化剂和氧化钛催化体系选择性偏低,这也是今后需要解决的重点。     

高比表面g-C_3N_4/竹叶炭催化氧化环己基苯

将单腈胺浸渍到竹叶上,在N2气氛中600℃焙烧,制备高比表面积的石墨型氮化碳/竹叶炭(g-C3N4/BC),以得到活性稳定、易于循环利用的催化材料。采用XRD、FT-IR、SEM、BET等方法对g-C3N4/BC进行表征。将g-C3N4/BC作为催化剂用于催化氧气氧化环己基苯(CHB)合成苯酚和环己酮。考察了反应温度、氧气压力和催化剂重复使用对反应的影响。结果表明:在g-C3N4/BC催化作用下,110℃、1.1 MPa O2下反应4 h,CHB转化率为16.7%,苯酚和环己酮选择性分别为64.0%和57.0%。催化剂循环使用10次,催化性能没有明显变化。并提出了g-C3N4/BC催化氧化CHB的反应途径和催化机理。     

片状g-C_3N_4可见光响应催化剂的热聚合法制备及光催化活性

以三聚氰胺为前驱体,通过热聚合法制得片状石墨相氮化碳g-C3N4,采用SEM,TEM,XRD和UV-Vis DRS分析了催化剂的组成、形貌和光吸收性能。以甲基橙为模拟污染物,研究了g-C3N4催化剂的可见光驱动催化活性。结果表明,所得g-C3N4为片状结构,多甲基橙具有较好的可见光催化降解活性。     

合成钼钒磷杂多酸的新方法及其催化性能

通过反应含化学计量的MoO3、V2O5和H3PO4的混合液,开发了一种环境友好制备钼钒磷杂多酸H3+nPMo12-nVnO40•xH2O (PMoVn,n=1～3) 的方法。通过ICP元素分析,TG、XRD和IR等表征,证明钒原子取代钼进入了杂多酸的Keggin骨架。在以冰乙酸和乙腈的混合物为溶剂,双氧水为氧化剂,催化苯羟基化制取苯酚的反应中,所制备的催化剂表现出良好的催化活性。其中,PMoV2具有最高的活性,对应的苯转化率为34.5％,苯酚的选择性为100％。     

钒基催化剂催化苯羟基化制苯酚反应机理

苯羟基化制苯酚是C—H键向C—O键转变富有挑战性的课题之一。该文论述了钒基催化剂催化苯羟基化制苯酚反应机理的研究进展。以钒活性中心为主线,着重从自由基、非自由基和双活性催化机理三个方面进行详细分析归纳,同时分析中涵盖了此类催化剂高效性的本质和催化微环境的重要性。由于此类催化体系及催化机理能够为解决苯环上C—H键难活化和苯酚的深度氧化等科学问题提供理论指导。因此,很有必要聚焦经济与安全并存的苯酚合成方法,同时依托已有的催化反应机理,开发更稳定且高性能的催化剂,促进我国丰富的烃类有机化合物资源利用的原始创新。     

钒掺杂β-沸石分子筛催化剂催化苯羟基化制备苯酚反应

通过浸渍法制备了钒/β-沸石系列催化剂,研究了催化剂的制备条件(煅烧温度和煅烧时间)对催化活性的影响。考察了在不同的反应条件(反应时间,催化剂的量,H2O2的量)下钒/β-沸石催化剂对苯羟基化制备苯酚的催化活性。在优化反应条件下得到苯的转化率为9.7%和苯酚的选择性为96%。     

苯和苯酚直接催化羟基化反应研究新进展

叙述了苯直接催化羟基化反应制苯酚、苯酚直接催化羟基化反应制苯二酚的研究 开发的最新进展,介绍了不同氧化剂的试验情况,评述了各类多相催化剂的研究开发成 果。H2O2作为苯及苯酚羟基化反应的氧化剂,具有反应条件温和,产物选择性高,对环境 无害等特点,成为工业催化领域中由苯直接羟基化反应制苯酚、苯酚直接羟基化反应制 苯二酚的主导氧化剂,开发高效的多相催化剂是该绿色合成技术的技术关键。     

新型氮化碳纳米材料的制备与性能测试

类石墨氮化碳(g-C_3N_4)是一种新型的可见光光催化剂,但类石墨氮化碳g-C_3N_4本身有着的一些缺陷,直接造成其光催化效率低。为了消除这些缺陷的存在,提高其光催化效率。本文是将类石墨氮化碳(g-C_3N_4)进行加工处理得到厚度在50 nm左右的薄片,然后通过XRD、SEM和TEM等多种方法对该催化剂进行表征。并在可见光下对罗丹明B进行降解来判断其催化效率。     

不同烷基链长Janus g-C3N4的乳化性能及光催化应用

在石蜡-水乳液界面,使用不同烷基链长的溴代烃对纳米石墨相氮化碳(g-C3N4)单侧接枝改性得到了一系列Janus g-C3N4,用XRD、UV-vis、FT-IR、SEM等进行表征,荧光显微镜、接触角测试其乳化性能,苯甲醇光催化氧化为探针反应考察其催化性能.结果表明:用C4、C8、C12和C16改性的Janus g-C...     

木棉纤维改性氮化碳光催化降解有机污染物

采用一步热解法制备了木棉纤维(KF)改性的石墨相氮化碳(g-C₃N₄)催化剂,并考察了催化剂光催化降解有机污染物的性能。采用XRD、UV-Vis DRS、FT-IR、TEM、XPS、N₂吸附-脱附、PL表征对催化剂进行了结构、形貌、光学性能测试。结果表明,KF改性可以提高催化剂的比表面积,更大的比表面积可以提供更多的活性位点来参与光催化降解过程。UV-Vis DRS结果表明KF改性可以缩小催化剂的禁带宽度,提高催化剂对光能的吸收。在可见光下,KF改性的g-C₃N₄基催化剂对苯酚降解速率常数为0.259 h^-1,是纯g-C₃N₄的4.2倍,且具有优异的催化稳定性和结构稳定性。     

Kapok fiber modified carbon nitride photocatalytic degradation of organic pollutants

A kapok fiber (KF) modified graphite phase carbon nitride (g-C₃N₄) catalyst was prepared by a one-step pyrolysis method, and the photocatalytic degradation of organic pollutants was investigated. The structure and optical properties of KF-CN were characterized by XRD, UV-Vis DRS, TEM, PL, XPS, FT-IR and N₂ adsorption-desorption. The nitrogen adsorption-desorption isotherm results show that the presence of the mesoporous structure can improve the specific surface area of KF-CN. Elemental analysis characterization indicates the biochar modification is conductive to increase the C/N ratio of KF-CN. The XPS characterization also indicates that the introduction of carbon element can change the chemical environment of N element in the lattice of g-C₃N₄ and thus increases the electron density of N element. The photocatalytic degradation of phenol experiment was carried out to investigate the performance of as-prepared kapok fiber modified graphite carbon nitride photocatalysts by using high-pressure sodium lamp as visible light source. The results show the KF(5%)-CN(600) displayed the highest phenol degradation rate constant of 0.259 h^-1, which is 4.2 times of that of neat g-C₃N₄.The activity of KF(5%)-CN(600) does not decrease significantly after 5 cycles, hinting its excellent catalytic stability and structural stability. The possible reaction mechanism was proposed.     

银复合对石墨型氮化碳结构及光催化性能的影响

为了提高石墨型氮化碳(g-C_3N_4)的可见光催化性能,利用水热合成,通过片状g-C_3N_4自组装法制备了银复合的石墨型氮化碳材料,研究了不同硝酸银加入量对Ag/g-C_3N_4复合材料的结构与光催化性能的影响。采用紫外-可见(UV-Vis)分光光度计、X射线衍射光谱(XRD)、红外傅立叶变换光谱(FT-IR)和扫描电子显微镜(SEM)对材料的结构与性能进行表征。结果表明:所得复合材料由于g-C_3N_4自组装行为而形成球状结构,其球形的直径随着硝酸银加入量的增加而减小;与g-C_3N_4相比,复合材料具有高的催化性能,可能由于其银的均匀复合以及所形成的3维结构;而Ag(60)/g-C_3N_4表现出最高的催化活性,原因在于银离子浓度对制备的复合催化剂的光学性质、能带及结构的影响。     

金属改性的FSM-16分子筛催化苯与过氧化氢合成苯酚

研究了金属改性的FSM-16分子筛在催化苯与过氧化氢合成苯酚反应中的应用,其中钒改性的FSM-16分子筛显示了较好的活性和高的选择性。当温度为323 K,反应时间为10 h,n(H2O2)∶n(C6H6)=1∶1,乙酸作溶剂,在催化剂V-FSM-16上得到苯的转化率为5.8%,苯酚的选择性为98.8%。催化剂的红外光谱和XRD的表征表明,钒进入了分子筛的骨架中。     

Mn-P共掺杂氮化碳的制备及其光催化性能研究

采用四水氯化锰、磷酸氢二铵和三聚氰胺为原料制备了Mn-P共掺杂的石墨相氮化碳(g-C3 N4).使用X射线衍射光谱(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、光致荧光光谱(PL)、紫外-可见漫反射光谱(UV-Vis DRS)、电化学阻抗谱(EIS)、瞬态光电流响应等分析测试手段对制备的催化剂...     

Effects of vanadium supported on ZrO2 and sulfolane on the synthesis of phenol by hydroxylation of benzene with oxygen and acetic acid on palladium catalyst

The catalyst system consisting of Pd, transition metal-modified ZrO₂ and acetic acid was found to catalyze the hydroxylation of benzene with molecular oxygen without hydrogen and phenol was formed. Of transition metals employed, only vanadium additive was found to be effective for improving the rate of phenol formation as well as the selectivity, while any other transition metals such as iron, molybdenym, tungsten and yttrium were not promotive. Support effects on vanadium were in the order: V/ZrO₂> V/Al₂O₃> V/SiO₂. The highest rate of phenol formation was obtained at 0.5wt%V/ZrO₂ catalyst. Phenol selectivity was dramatically improved by the addition of sulfolane, while benzene conversion and STY of phenol formation decreased. It is assumed that Pd(II) and Pd(IV) intermediates derived from acetic acid, oxygen and palladium acetate could play an important role in hydroxylation of benzene.     

Influence of temperature on hydroxylation of benzene to phenol using molecular oxygen catalyzed by V/SiO2

Effect of temperature on hydroxylation of benzene to phenol with molecular oxygen as an oxidant was studied over V/SiO₂ using different reductants. The V/SiO₂ with highly dispersed vanadium species was prepared by a sol–gel process and characterized by diffuse reflectance UV–Vis and ESR. This work shows that the onset temperature range of benzene hydroxylation and the temperature reaching the maximum phenol yield differ corresponding to each reductant. The reducing capacity of reductant can be shown by changing temperature and affects, in turn, benzene conversion, product selectivity, and the amount of leaching of V species.     

Transition Metals Supported on Activated Carbon as Benzene Hydroxylation Catalysts

The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over catalyst containing various transition metals impregnated on activated carbon. Iron and vanadium impregnated catalysts gave better yields of phenol compared to copper impregnated catalysts. The activity of transition metals supported on activated carbon catalyst in the production of phenol was V > Fe > Cu. In addition to the role of transition metals in catalyzing the hydroxylation reaction, the hydrophobic nature of the activated carbon surface and also the surface acidity and basicity seems to have enhanced the performance of these catalysts.     

Enhanced performance of g-C3N4/TiO2 photocatalysts for degradation of organic pollutants under visible light☆

Photocatalytic degradation is one of the most promising remediation technologies in terms of advanced oxida-tion processes (AOPs) for water treatment. In this study, novel graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) composites were synthesized by a facile sonication method. The physicochemical properties of the photocatalyst with different mass ratios of g-C3N4 to TiO2 were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 sorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV–vis DRS. The photocatalytic performances were evaluated by degradation of methylene blue. It was found that g-C3N4/TiO2 with a mass ratio of 1.5:1 exhib-ited the best degradation performance. Under UV, the degradation rate of g-C3N4/TiO2 was 6.92 and 2.65 times higher than g-C3N4 and TiO2, respectively. While under visible light, the enhancement factors became 9.27 (to g-C3N4) and 7.03 (to TiO2). The improved photocatalytic activity was ascribed to the interfacial charge transfer between g-C3N4 and TiO2. This work suggests that hybridization can produce promising solar materials for envi-ronmental remediation.