Electrochemical CaC2-Mediated Conversion of Biochar to C2H2: High Carbon Efficiency and Low Contamination

The carbon to CaC₂ route is promising to provide a sustainable elementary unit, C₂H₂, for the organic synthesis industry, but the traditional thermal reaction process suffers from low carbon efficiency, harmful gas contamination, high temperature operation, and risky CO management. We herein report a high carbon efficiency (ca. 100 %) conversion of biochar to C₂H₂ through an electrolytic synthesis of solid CaC₂ in molten CaCl₂/KCl/CaO at 973 K. The main reactions are carbon reduction to CaC₂ at the solid carbon cathode and oxygen evolution at an inert anode. Meanwhile, the electrolysis removes S and P from the solid cathode, avoiding the formation of CaS and Ca₃P₂ in CaC₂ and consequently eliminating H₂S and PH₃ contamination in the finally produced C₂H₂.     

A Microporous Hydrogen Bonded Organic Framework for Highly Selective Separation of Carbon Dioxide over Acetylene

The separation of acetylene (C₂H₂) from carbon dioxide (CO₂) is a very important but challenging task due to their similar molecular dimensions and physical properties. In terms of porous adsorbents for this separation, the CO₂-selective porous materials are superior to the C₂H₂-selective ones because of the cost- and energy-efficiency but have been rarely achieved. Herein we report our unexpected discovery of the first hydrogen bonded organic framework (HOF) constructed from a simple organic linker 2,4,6-tri(1H-pyrazol-4-yl)pyridine (PYTPZ) (termed as HOF-FJU-88) as the highly CO₂-selective porous material. HOF-FJU-88 is a two-dimensional HOFs with a pore pocket of about 7.6 Å. The activated HOF-FJU-88 takes up a high amount of CO₂ (59.6 cm³ g⁻¹) at ambient conditions with the record IAST selectivity of 1894. Its high performance for the CO₂/C₂H₂ separation has been further confirmed through breakthrough experiments, in situ diffuse reflectance infrared spectroscopy and molecular simulations.     

A near-infrared acetylene detection system based on a 1.534 μm tunable diode laser and a miniature gas chamber

A near-infrared (NIR) dual-channel differential acetylene (C₂H₂) detection system was experimentally demonstrated based on tunable diode laser absorption spectroscopy (TDLAS) technique and wavelength modulation spectroscopy (WMS) technique. A distributed feedback (DFB) laser modulated by a self-developed driver around 1.534 μm is used as light source. A miniature gas chamber with 15 cm path length is adopted as absorption pool, and an orthogonal lock-in amplifier is developed to extract the second harmonic (2f) signal. Sufficient standard C₂H₂ samples with different concentrations were prepared, and detailed measurements were carried out to study the detection performance. A good linear relationship is observed between the amplitude of the 2f signal and C₂H₂ concentration within the range of 200–10,000 ppm, and the relative measurement error is less than 5% within the whole range. A long-term monitoring lasting for 20 h on a 1000 ppm C₂H₂ sample was carried out, and the maximum concentration fluctuation is less than 2%. Due to the capability of using long-distance and low-loss optical fiber, the gas-cell can be placed in the filed for remote monitoring, which enables the system to have good prospects in industrial field.     

一种结合均相和非均相催化剂优势的聚乙炔纳米颗粒负载的钯（II）催化剂

负载型的金属催化剂虽然分离方便,但在反应活性、选择性以及催化剂的结构表征方面均明显不如相应的均相催化剂。将均相催化剂通过不同的化学键固载于高比表面积载体是实现均相催化剂多相化的重要途径,这样可使催化剂兼具均相和多相催化剂的优势。然而要将均相催化剂锚定于特定载体上,通常涉及较为复杂的合成反应,对载体也有严格的要求。因而该法仅仅适用于实验室研究,难以实现规模生产。因此,提供一种简便有效地制备兼具均相和多相催化剂优势的催化剂合成方法非常必要。本文报道一种简便的制备聚乙炔纳米颗粒负载Pd(II)催化剂(NP-Pd(II))的方法,所制催化剂在水相中的Suzuki-Miyaura偶联反应中表现出极高的活性,同时具有便于分离、容易放大制备的特点。在室温下,将乙炔气通入PdCl42-的水溶液中迅速变得浑浊,静置后容器底部有棕色沉淀,同时溶液变为无色透明。固体产物使用水、乙醇等溶剂进行洗涤;干燥之后收集既得聚乙炔纳米颗粒负载的Pd(II)催化剂NP-Pd(II)。使用透射电子显微镜、红外(IR)及拉曼吸收光谱、X射线衍射(XRD)、X射线光电子能谱(XPS)以及X射线吸收光谱(EXAFS)等手段对NP-Pd(II)进行了详细表征。结果显示,在NP-Pd(II)中Pd并非以Pd纳米颗粒形式存在; XRD中没有未Pd纳米晶的特征衍射峰。 IR等表征证明乙炔在Pd的催化作用下发生聚合作用,生成了聚乙炔。 EXAFS结果表明, Pd分别和氯原子以及C=C双键进行配位;同时,没有观察到Pd–Pd键的生成,进一步证明了Pd未被还原为Pd纳米颗粒。 XPS也印证了Pd(II)的价态。形貌上, NP-Pd(II)为直径2–3nm的颗粒,其中的Pd原子均匀分散于聚乙炔纳米颗粒上,使其在反应过程中能够充分地与底物接触,从而在Suzuki-Miyaura偶联反应中表现出极高的活性。更重要的是,由于“憎水效应”, NP-Pd(II)在溶液中以微米级的聚集体形式存在,因而反应后通过离心或者静置从反应体系中分离出来。因此,在NP-Pd(II)催化剂中,每个Pd原子都是潜在的活性中心,这与典型的均相催化剂相似;同时,其独特的形貌使其具备了多相催化剂便于分离的特点。因此, NP-Pd(II)是一种兼具均相和多相催化剂优点的催化剂且其催化剂的制备方法极为简便。乙炔是常用的工业气体,溶剂采用水,制备在室温下即可完成,我们也成功地制备出克级规模的高活性、稳定性的NP-Pd(II)催化剂。     

Pd8簇催化氢化乙炔的反应机理

采用密度泛函理论(DFT)中的B3PW91方法研究了过渡金属Pd₈簇催化氢化乙炔的反应机理. 研究表明: H₂进入Pd₈簇后解离成H原子, 并且只有当H原子吸附在Pd₈簇表面上时, 催化氢化反应才能发生. 过渡金属Pd₈簇催化氢化乙炔的反应机理的研究证实该催化反应从两种反应物出发经过两条不同的反应途径完成催化氢化反应, 两种反应物分别为吸附在Pd₈簇上的乙炔(Pd₈(2H)－CH＝CH)和其同分异构体亚乙烯基吸附物(Pd₈(2H)－C＝CH₂). 两条途径均为多步连续的加氢反应, 不同之处在于从Pd₈(2H)－CH＝CH出发的为单一路径, 解离后的H原子分步依次加成到吸附在Pd₈簇上的乙炔中的C原子上, 直到反应完成生成乙烷. 而从Pd₈(2H)－C＝CH₂出发的路径较为复杂, 分别经过两个不同的过渡态和中间体生成次乙基中间体, 该过程相对应的反应位垒相差约12.552 kJ·mol^-1, 说明这两个过渡态同时存在, 无先后次序. 然后继续加成H原子直到生成乙烷完成反应. 同时, 两条路径分别形成一系列具有应用价值的C₂有机化合物中间体, 其中一些中间体通过分子内质子转移相互转化, 使得原本独立的两条反应路径联系在一起, 成为网状路径.     

NaCl担载Fe催化裂解乙炔制备纳米碳材料

以水溶性NaCl担载Fe作催化剂,于400℃和420C下化学气相沉积法催化裂解乙炔进行了反应.通过X射线衍射仪、扫描电子显微镜和能谱分析仪对催化剂进行了表征,表征结果显示:活性组分Fe被分散成了粒径在10～40nm之间的纳米颗粒;通过扫描电子显微镜和高分辨透射电镜对产物进行了表征,表征结果显示:当裂解温度为400℃时,...     

Carbon-supported binary Li-Sn catalyst for acetylene hydrochlorination

The study of a novel catalyst containing LiCl and SnCl₂ (LiSn/AC) for acetylene hydrochlorination has been reported in this paper. Furthermore, the performance of both high activity (98.3%) and selectivity (>98.0%) are achieved by LiSn/AC catalysts under the reaction temperature of 200 °C and C₂H₂ hourly space velocity of 30 h^?1. The structural characteristics of the Sn based catalysts were deeply researched via BET, XRD, TEM, TPR, C₂H₂-TPD, XPS and TG techniques. According to these characteristic results, we proposed that the presence of Sn²⁺ exhibited better activity and stability than that of Sn⁴⁺ in Sn based catalysts. Additionally, LiCl additives not only can restrain the oxidation of Sn²⁺ and the loss of Sn⁴⁺ in fresh Sn based catalysts but also make the Sn^δ+ (δ = 2,4) species dispersed well on the surface of support. Therefore, the adsorption capacity of C₂H₂ and HCl was enhanced in LiSn/AC, which exhibited the better catalytic performance than that of Sn based catalyst.     

含炔基有机硅共轭聚合物的光谱性能研究

应用荧光光谱、紫外光谱对不同结构的含炔基有机硅共轭聚合物的发光性能进行了表征和研究。探讨了聚合物主链上Si原子取代基的结构以及主链中炔基单元结构对其发光性能的影响,研究结果表明,聚合物可在219～260 nm处有紫外吸收,随着Si原子上取代基共轭性能的增强,以及主链中炔基数目的增多、链段共轭程度的增大,最大吸收波长红移。取代基的影响较小,主链共轭结构对吸收光谱的影响明显。不同主链结构的共轭聚合物在320～353 nm处发出一定强度的荧光。结果显示,聚合物主链共轭基团的结构对发射光谱具有明显的影响,随着主链中炔基数目的增多,最大发射波长显著向长波方向移动。由于此类聚合物的特殊结构使得他们具有良好的热学稳定性,因此这类聚合物具有潜在的光学应用价值。     

Interactions of NiO particles with polycyclic aromatic hydrocarbons and acetylene generated from the pyrolysis of a model fuel

Experiments have been conducted to study the effects of NiO, a prevalent form of nickel in combustion-generated ash particles, on polycyclic aromatic hydrocarbons (PAH) and other hydrocarbons in a fuel product mixture. The fuel product mixture is generated from the gas-phase pyrolysis, in N₂, of the model fuel catechol in a quartz tube reactor at 1100 K and 5 s, a condition that ensures full conversion of the catechol and produces a mixture—of PAH, hydrocarbon gases, and oxygen-containing species—that is representative of the products of practical liquid and solid fuels in pyrolysis and fuel-rich combustion environments. Once formed, the product mixture is passed, at the same temperature, through a bed of ultrafine NiO particles held in place by quartz wool, in the contact zone of the reactor. The products exiting the reactor are quenched, collected, and analyzed by non-dispersive infrared analyzers, gas chromatography, and high-pressure liquid chromatography with diode-array ultraviolet–visible absorbance detection. The results from the experiments at 1100 K show that—compared to the case of no inorganics in the contact zone—when NiO is present: PAH yields are reduced 86% (from 10.8% to 1.48% fed carbon); all of the highly mutagenic 5- and 6-ring PAH are eliminated; and all of the acetylene, the highest-yield hydrocarbon product when NiO is absent, and other hydrocarbons with carbon–carbon triple bonds are eliminated from the gas phase. Most of the surface-bound carbon is released as CO. Similar experiments at 1275 K show that—except for the release of the surface-bound carbon as CO—the selective surface effects of NiO bring about similar results at higher temperature: 89% reduction in PAH yield, elimination of mutagenic 5- and 6-ring PAH, removal of acetylene and acetylenic species, as well as a decrease in the production of solid carbon (not formed at 1100 K).     

An IH-QCL based gas sensor for simultaneous detection of methane and acetylene

Extended wavelength tuning of an IH-QCL (integrated heater quantum cascade laser) is exploited for simultaneous detection of methane and acetylene using direct absorption spectroscopy. The integrated heater, placed within few microns of the laser active region, enables wider wavelength tuning than would be possible with a conventional DFB (distributed feedback) QCL. In this work, the laser current and heater resistor current are modulated simultaneously at 25?kHz to tune the laser over 1279.6–1280.1 cm^?1, covering absorption transitions of methane and acetylene. The laser is characterized extensively to understand the dependence of wavelength tuning on modulation frequency, modulation amplitude and phase difference between laser/heater modulation. Thereafter, the designed sensor is validated in both room-temperature static cell experiments and non-reactive high-temperature-measurements in methane-acetylene-argon gas mixtures in the shock tube. Finally, the sensor is applied for simultaneous detection of methane and acetylene during the high-temperature pyrolysis of iso-octane behind reflected shock waves.