谢艳玲,祝琳华,司甜.埃洛石纳米管的改性方式对其负载的金催化剂在环己烷液相选择性氧化反应中的催化性能的影响[J].分子催化编辑部,2021,35(6):518-528
埃洛石纳米管的改性方式对其负载的金催化剂在环己烷液相选择性氧化反应中的催化性能的影响
Influence of Modification Methods of Halloysite on the Catalytic Performance of Halloysite-Supported Gold Catalysts for Selective Oxidation of Cyclohexane
投稿时间:2021-07-06  修订日期:2021-09-17
DOI:10.16084/j.issn1001-3555.2021.06.003
中文关键词:  催化剂载体  改性  金纳米粒子  环己烷液相选择性氧化
英文关键词:catalyst support  modification  gold nanoparticles  liquid phase selective oxidation of cyclohexane
基金项目:国家自然科学基金(21166010)
作者单位E-mail
谢艳玲 昆明理工大学 化学工程学院, 云南 昆明 650500  
祝琳华 昆明理工大学 化学工程学院, 云南 昆明 650500 hualing67731@126.com 
司甜 昆明理工大学 化学工程学院, 云南 昆明 650500  
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中文摘要:
      为了提高纳米金在埃洛石纳米管(halloysite nanotubes,HNTs)上的负载率并改善负载型金催化剂的稳定性,采用经过有机硅烷(N-(β-氨乙基)-γ-氨丙基三甲氧基硅烷,AEAPTMS)化学改性的埃洛石纳米管(AHNTs)作为载体,利用AEAPTMS上的-NH2能够配位俘获金离子的特点,实现了金的前驱体HAuCl4·4H2O在化学改性埃洛石上的高效负载,经硼氢化钠液相还原获得了化学改性埃洛石AHNTs负载的纳米金催化剂样品1.5%(质量分数) Au/AHNTs(金的实际负载量为1.43%(质量分数)).采用FT-IR和29Si CP/MAS NMR表征了埃洛石的化学改性效果,并采用TEM及XPS分别表征了该催化剂样品上纳米金的粒径分布和催化剂表面金的价态.研究结果表明,平均粒径为2.5 nm金颗粒高度分散在经过化学改性的埃洛石纳米管上,且金元素主要以金属态Au0的形式存在.表征了该催化剂样品在环己烷液相选择性氧化反应中的催化活性和选择性,在反应温度170℃,压力2 MPa下反应2 h,环己烷的转化率达到9.06%,对目标产物环己酮和环己醇(KA油)的选择性达到83.06%,且循环使用4次后,对环己烷的转化率还能达到5.82%,对KA油的选择性维持在81.39%,仍能满足该反应体系对催化剂的活性和选择性的基本要求.与之相比,物理改性的埃洛石载体PHNTs负载的金催化剂样品2.0%(质量分数)Au/AHNTs(金的实际负载量为1.40%(质量分数))在相同的模型反应条件下,虽然新鲜催化剂的活性和选择性略微优于化学改性埃洛石AHNTs负载的金催化剂样品1.5%(质量分数)Au/AHNTs,但其稳定性较化学改性埃洛石所负载的金催化剂差,经过3次循环使用,对KA油的选择性已经下降至71.31%.上述结果表明,埃洛石载体的改性方式对其负载的金催化剂的稳定性有显著影响,经化学改性的埃洛石载体与活性组分金之间较强的相互作用力有助于提高其所负载的金催化剂的稳定性.
英文摘要:
      In order to increase the loading rate of nano-gold on halloysitenano-tubes (HNTs) and to improve the catalytic stability of the gold catalyst, halloysitenano-tube modified by organic silane(N(-β-Aminoethyl) -γ-Aminopropyltrimethoxysilane, AEAPTMS) was used as carrier(AHNTs) to capture gold ions of chloroglucic acid precursor to prepare chemically modified halloysite (AHNTs) -supported gold catalyst 1.5% (Mass fraction) Au/AHNTs, which was reduced by sodium borohydride in liquid phase. The halloysite modified by chemical method were characterized by FT-IR and NMR, and the particle size distribution of nano gold as well as the valence of gold on the surface of gold catalysts were characterized by TEM and XPS respectively. The results showed that AHNTssupported gold nanoparticles with 2.5 nm average particle size were highly dispersed on the carrier mainly in the form of zero-valent gold(Au0). The activity and the selectivity of this catalyst sample for liquid phase selective oxidation of cyclohexane were tested at 170℃ and 2 MPa after reaction for 2 h, the conversion of cyclohexane and the selectivity for cyclohexanone and cyclohexanol(KA oil) achieved 9.06% and 83.06% respectively. Moreover, comparing with the sample of 2.0% (Mass fraction) Au/PHNTs supported by physically modification halloysite (PHNTs), 1.5%(Mass fration) Au/AHNTs showed better stability. The basic requirement of catalytic activity and selectivity for selective oxidation of cyclohexane still can be reached after reused for 4 times on the sample of 1.5% (Mass fraction) Au/AHNTs, the conversion of cyclohexane and the selectivity for cyclohexanone and cyclohexanol(KA oil) respectively were 5.82% and 81.39%. However, under the same model reaction conditions, the gold catalyst sample of 2.0% (Mass fraction) Au/PHNTs showed slightly higher activity and selectivity than 1.5% (Mass fraction) Au/AHNTs, but its stability was lower than the later one. The catalytic selectivity of catalyst 2.0% (Mass fraction) Au/PHNTs for selective oxidation of cyclohexane has declined to 71.31% after reused for 3 times. The above results revealed that the modification methods of halloysite have a significant impact on the stability forits supported nano-gold catalysts. The strong interaction between the chemically modified carrier and the active component goldis helpful to improve the stability of the gold catalysts.
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