Influence of Pore Structure on Catalytic Properties of Mesoporous Silica-supported Co-B Amorphous Alloys in Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Co‐B amorphous alloy catalysts supported on three kinds of mesoporous silica (common SiO₂, MCM‐41 and SBA‐15) have been systematically studied focusing on the effect of pore structure on the catalytic properties in liquid‐phase hydrogenation of cinnamaldehyde to cinnamyl alcohol (CMO). Structural characterization of a series of different catalysts was performed by means of N₂ adsorption, X‐ray diffraction, transmission electron microscopy, hydrogen chemisorption, and X‐ray photoelectron spectroscopy. Various characterizations revealed that the pore structure of supports profoundly influenced the particle size, location and dispersion degree of Co‐B amorphous alloys. Co‐B/SBA‐15 was found more active and selective to CMO than either Co‐B/SiO₂ or Co‐B/MCM‐41. The superior catalytic activity could be attributed to the higher active surface area, because most of Co‐B nanoparticles in Co‐B/SBA‐15 were located in the ordered pore channels of SBA‐15 rather than on the external surface as found in Co‐B/SiO₂ and Co‐B/MCM‐41. Meanwhile, the geometrical confinement effect of the ordered mesoporous structure of SBA‐15 was considered to be responsible for the enhanced selectivity to CMO on Co‐B/SBA‐15, inhibiting the further hydrogenation of CMO to hydrocinnamyl alcohol.     

离子液体中离子型共聚高分子保护的铂纳米粒子催化剂催化肉桂醛选择性加氢

用离子型共聚高分子poly(NVP-co-VBIM Cl-)保护离子液体[bmim]BF4中的铂纳米粒子.以肉桂醛选择性加氢制肉桂醇反应来评价铂纳米粒子的催化活性.结果表明,该体系下得到的铂纳米粒子粒径分布均一,并具有很高的稳定性.在离子液体中,此种高分子保护的铂纳米粒子对肉桂醛加氢制肉桂醇表现出良好的活性(转化率>90%)和选择性(>95%).催化剂可多次循环,其活性和选择性均能良好保持.     

Sn对肉桂醛加氢催化剂Pt/Al2O3的修饰作用

研究了负载型Pt催化剂上肉桂醛加氢反应规律,并对Sn的修饰作用进行了考察.未修饰催化剂Pt/Al2O3上,主要以C=C加氢为主;加入少量Sn修饰剂,肉桂醛加氢活性大幅度提高,而且C=O加氢选择性有所提高.当Sn/Pt摩尔比大于0.8后,虽然C=O加氢选择性仍较高,但加氢活性明显降低.Sn/Pt摩尔比为1的催化剂上,肉桂醛转化率高于96%时,肉桂醇选择性可高达80%.结合XRD与化学吸附等表征结果,表明电子因素和立体因素的综合作用是影响肉桂醛加氢选择性的主要因素.     

纳米nah高化学反应活性

纳米氢化钠;氯苯氢解;肉桂醛选择还原;二甲亚砜金属取代反应;烯烃催化加氢     

Pt (111)面和Pt14团簇上肉桂醛吸附及选择性加氢机理研究

利用密度泛函理论研究了Pt（111）面及Pt₁₄团簇对肉桂醛（CAL）的吸附作用和不完全加氢的反应机理。分析吸附能结果表明,肉桂醛分子以C=O与C=C键协同吸附在Pt（111）面上的六角密积（Hcp）位最稳定,以C=C键吸附在Pt₁₄团簇上最稳定,且在Pt₁₄团簇上的吸附作用较Pt（111）面更强。由过渡态搜索并计算得到的反应能垒及反应热可知,肉桂醛在Pt（111）面和Pt₁₄团簇上均较容易对C=O键加氢得到肉桂醇（COL）。其中,优先加氢O原子为最佳反应路径,即Pt无论是平板还是团簇对肉桂醛加氢均有较好的选择性。同时发现,肉桂醛分子在Pt（111）面的加氢反应能垒较Pt₁₄团簇上更低,即Pt的催化活性及对肉桂醛加氢产物选择性与其结构密切相关,其中,Pt（111）面对生成肉桂醇更加有利。     

1,10-菲啰啉修饰Cu/Al2O3催化肉桂醛羰基高效选择性加氢

肉桂醛作为α,β-不饱和醛的代表性物质,其羰基选择性加氢的高效催化剂设计还存在一定挑战.经过1,10-菲啰啉(L₁)修饰制备的Cu催化剂(Cu/Al₂O₃-L₁),可以在肉桂醛几乎完全转化的情况下实现>95%的肉桂醇选择性.表征和DFT结果表明,1,10-菲啰啉的空间位阻限制了肉桂醛的平面吸附,提高了肉桂醇的选择性,同时其与Cu的相互作用降低了H₂的解离能,提高了催化剂的活性.这项工作强调了含N-配体在催化剂表面修饰中的重要性,并为进一步合理设计高选择性加氢催化剂提供了一些借鉴.     

一锅反应合成1-羟基-3-苯基烯丙基膦(次膦)酸酯

1-羟基膦酸酯类化合物具有显著的生物活性和潜在的医学用途,从五十年代起,不断有新的或改良的合成方法出现。但这些方法并不理想,常伴有副反应等。近年来发展了用     

The Effect of Chemical Reducing Agents in the Synthesis of Sol-Gel Ru-Sn Catalysts: Selective Hydrogenation of Cinnamaldehyde

The influence of chemical reduction on the properties of bimetallic Ru-Sn/SiO₂ catalyst was studied. Prepared sol-gel catalysts were reduced by NaBH₄, KBH₄, H₂, and CH₂O. Physical and catalytic properties of reduced catalysts were compared to non-reduced ones in the liquid-phase hydrogenation of cinnamaldehyde. The influence of boron impregnation was investigated. The observed hydrogenation activity and selectivity towards cinnamylalcohol were effected by reduction pretreatment. The NaBH₄ reduced catalyst exhibited the highest activity and selectivity. Reduction pretreatment influenced the pore sizes, active metal surface as well as content of carbon impurities. Traces of the reduction agents were detected in the catalysts. Boron impregnation presumably improved the catalyst activity, but had a minor effect on the selectivity.     

Ni-Ti Intercalated and Supported Bentonite for Selective Hydrogenation of Cinnamaldehyde

Ni-Ti intercalated bentonite catalysts (Ni-Ti-bentonite) and Ni-TiO₂ supported bentonite catalysts (Ni-TiO₂/bentonite) were prepared, and the effects of Ni-Ti supported and intercalated bentonite on the selective hydrogenation of cinnamaldehyde were investigated. Ni-Ti intercalated bentonite enhanced the Brønsted acid sites strength, decreased the acid amount and Lewis's acid sites strength, which inhibited the activation of the C=O bond and contributed to selective hydrogenation of the C=C bond. When Ni-TiO₂ was supported on bentonite, the acid amount and Lewis's acid strength of the catalyst increased, providing additional adsorption sites and increased the acetals byproducts. Due to the higher surface area, mesoporous volume, and suitable acidity, compared with Ni-TiO₂/bentonite in methanol solvent, 2 MPa, 120 °C for 1 h, Ni-Ti-bentonite exhibited a higher cinnamaldehyde (CAL) conversion of 98.8 %, as well as a higher hydrocinnamaldehyde (HCAL) selectivity of 95 %, and no acetals were found in the product.     

Simultaneous Estimation of Cinnamaldehyde and Eugenol in Essential Oils and Traditional and Ultrasound-Assisted Extracts of Different Species of Cinnamon Using a Sustainable/Green HPTLC Technique

A wide range of analytical techniques are reported for the determination of cinnamaldehyde (CCHO) and eugenol (EOH) in plant extracts and herbal formulations either alone or in combination. Nevertheless, sustainable/green analytical techniques for the estimation of CCHO and EOH either alone or in combination are scarce in the literature. Accordingly, the present research was carried out to establish a rapid, highly sensitive, and sustainable high-performance thin-layer chromatography (HPTLC) technique for the simultaneous estimation of CCHO and EOH in the traditional and ultrasound-assisted methanolic extracts of Cinnamomum zeylanicum, C. burmannii, and C. cassia and their essential oils. The simultaneous estimation of CCHO and EOH was performed through NP-18 silica gel 60 F254S HPTLC plates. The cyclohexane/ethyl acetate (90:10, v v⁻¹) solvent system was optimized as the mobile phase for the simultaneous estimation of CCHO and EOH. The greenness score of the HPTLC technique was predicted using AGREE software. The entire analysis was carried out at a detection wavelength of 296 nm for CCHO and EOH. The sustainable HPTLC technique was observed as linear in the range 10–2000 ng band⁻¹ for CCHO and EOH. The proposed technique was found to be highly sensitive, rapid, accurate, precise, and robust for the simultaneous estimation of CCHO and EOH. The content of CCHO in traditional methanolic extracts of C. zeylanicum, C. burmannii, and C. cassia was found to be 96.36, 118.49, and 114.18 mg g⁻¹, respectively. However, the content of CCHO in ultrasound-assisted methanolic extracts of C. zeylanicum, C. burmannii, and C. cassia was found to be 111.57, 134.39, and 129.07 mg g⁻¹, respectively. The content of CCHO in essential oils of C. zeylanicum, C. burmannii, and C. cassia was found to be 191.20, 214.24, and 202.09 mg g⁻¹, respectively. The content of EOH in traditional methanolic extracts of C. zeylanicum, C. burmannii, and C. cassia was found to be 73.38, 165.41, and 109.10 mg g⁻¹, respectively. However, the content of EOH in ultrasound-assisted methanolic extracts of C. zeylanicum, C. burmannii, and C. cassia was found to be 87.20, 218.09, and 121.85 mg g⁻¹, respectively. The content of EOH in essential oils of C. zeylanicum, C. burmannii, and C. cassia was found to be 61.26, 79.21, and 69.02 mg g⁻¹, respectively. The amounts of CCHO and EOH were found to be significantly higher in ultrasound-assisted extracts of all species compared to its traditional extraction and hence ultrasound extraction has been proposed as a superior technique for the extraction of CCHO and EOH. The AGREE analytical score of the present analytical technique was predicted as 0.75, suggesting excellent greenness profile of the proposed analytical technique. Based on all these observations and results, the proposed sustainable HPTLC technique can be successfully used for the simultaneous estimation of CCHO and EOH in different plant extracts and herbal products.