催化发光法同时测定空气中的甲醛、苯和二氧化硫

基于甲醛、苯和二氧化硫在纳米Ti3CeY2O11上的催化发光有交叉敏感现象,在3个波长处分别确定甲醛、苯和二氧化硫浓度与催化发光信号强度的响应关系,再依据发光信号强度的叠加性特征即可获取甲醛、苯和二氧化硫的准确浓度,据此建立了同时测定空气中甲醛、苯和二氧化硫的新方法.3个分析波长分别为420、535和680 nm,敏感材料表面温度为280℃,载气流速为130 mL/min.本方法对甲醛、苯和二氧化硫的检出限(3σ)分别为0.04、0.05和0.10 mg/m3,线性范围分别为0.08~75.60 mg/m3、0.10~101.40 mg/m3和0.30~115.00 mg/m3, 回收率分别为96.4%~103.7%、97.8%~102.5%和97.2%~103.3%.常见共存物,如乙醛、甲苯、硫化氢、氨、甲醇、乙醇和二氧化碳等不干扰测定.连续200 h通浓度均为50 mg/m3的甲醛、苯和二氧化硫混合气体,发光强度的相对偏差≤2%,表明此纳米级复合氧化物对甲醛、苯和二氧化硫的敏感性的寿命长.本方法充分利用了交叉敏感现象,可以实现空气中甲醛、苯和二氧化硫的在线分析.     

Silica supported nanopalladium prepared by hydrazine reduction

Palladium catalysts (1–10 wt.% Pd) supported on silica were prepared by hydrazine reduction of palladium chloride at room temperature. They were characterized by XRD, TEM, EDX, H₂-adsorption, and H₂-TPD and tested in the gas phase hydrogenation of benzene in the temperature range 75–250 °C. A conventional catalyst (1 wt.% Pd) obtained by calcination then hydrogen reduction of the same metal precursor was studied for comparison. Metal particles with a size range 6.8–28.4 nm were obtained. Dispersion, hydrogen storage and activity in benzene hydrogenation increased with decreasing particle size. In comparison, the classical catalyst was found much more dispersed (mean particle size of 1.6 nm) and more active (specific rate 1.6–3.7 times higher) than the homolog hydrazine catalyst. However, unexpectedly, turnover frequency (TOF) calculations indicated a greater reactivity of the metal surface atoms for the hydrazine catalyst. It also stored more hydrogen. These contrasting results are discussed in relation with the metal particle morphology.     

Total Synthesis of the Biologically Active,Naturally Occurring 3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol and Regioselective O‐Demethylation of Aryl Methyl Ethers

3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol ( 2 ), a natural product, has been synthesized for the first time starting from (3‐bromo‐4,5‐dimethoxyphenyl)methanol ( 5 ) in five steps and with an overall yield of 34%. The reaction of some methoxymethyl‐substituted aryl methyl ethers with BBr₃, followed by the addition of MeOH, afforded the corresponding methoxymethyl‐substituted arylphenols in high yields.     

Preparation, characterization, activity and selectivity of highly loaded oxide promoted ruthenium catalysts for selective hydrogenation of benzene to cyclohexene

Summary The influence of promoters and precipitants of the catalyst precursor on the activity and selectivity of the hydrogenation of benzene to cyclohexene catalyzed by highly loaded oxide-promoted Ru/ZrO₂catalysts, carried out in a tetraphase reactor (in the presence of an aqueous solution of ZnSO₄), at 423 K and 5 Mpa, was studied. The effect of hydrogen diffusion on the reaction kinetics and on the selectivity has been taken into consideration, the internal pore diffusion being actually the limiting step. Hydrogen chemisorption measurements indicate that the catalyst activity is not influenced by the Ru dispersion, but rather by weakly chemisorbed species.     

Phase equilibrium measurements of (methane + benzene) and (methane + methylbenzene) at temperatures from (188 to 348) K and pressures to 13 MPa

New isothermal pTxy data are reported for (methane + benzene) and (methane + methylbenzene (toluene)) at pressures up to 13 MPa over the temperature range (188 to 313) K using a custom-built (vapor + liquid) equilibrium (VLE) apparatus. The aim of this work was to investigate literature data inconsistencies and to extend the measurements to lower temperatures. For (methane (1) + benzene (2)), measurements were made along six isotherms from (233 to 348) K at pressures to 9.6 MPa. At temperatures below 279 K there was evidence of a solid phase, and thus only vapor phase samples were analyzed at these temperatures. For the (methane (1) + methylbenzene (3)) system, measurements were made along seven isotherms from T = (188 to 313) K at pressures up to 13 MPa. Along the 198 K isotherm, a significant change in the data’s p,x slope was observed indicating (liquid + liquid) equilibria at higher pressures. The data were compared with literature data and with calculations made using the Peng–Robinson (PR) equation of state (EOS). For both binary systems our data agree with much of the literature data that also deviate from the EOS in a similar manner. However, the data of Elbishlawi and Spencer (1951) for both binary systems, which appear to have received an equal weighting to other data in the EOS development, are inconsistent with the results of our measurements and data from other literature sources.     

The behavior of benzene confined in a single wall carbon nanotube

We present the molecular dynamics study of benzene molecules confined into the single wall carbon nanotube. The local structure and orientational ordering of benzene molecules are investigated. It is found that the molecules mostly group in the middle distance from the axis of the tube to the wall. The molecules located in the vicinity of the wall demonstrate some deviation from planar shape. There is a tilted orientational ordering of the molecules which depends on the location of the molecule. It is shown that the diffusion coefficient of the benzene molecules is very small at the conditions we report here. © 2015 Wiley Periodicals, Inc.     

低碱度共沉淀法制备苯选择加氢Ru-Zn催化剂

在低碱度下采用共沉淀法成功制备了非负载型Ru-Zn催化剂,用于苯选择加氢制环己烯反应.固定氢氧化钠沉淀剂的量,考察了不同氯化锌加入量对催化剂结构和催化性能的影响,采用N2吸附、X射线衍射和程序升温还原等手段对催化剂进行了表征.同时考察了选用具有最佳锌含量的Ru-Zn催化剂时搅拌速度和硫酸锌添加剂等对催化反应性能的影响,最后考察了催化剂多次使用时的反应性能.研究表明, Zn含量16.7%(质量分数)的Ru-Zn催化剂具有最佳的催化性能;在ZnSO4水溶液(0.45 mol/L)中,优化反应条件(哈氏合金釜,1200 r/min,150oC, H2压5 MPa)下反应45 min,苯转化率57%时环己烯选择性可达80%(收率超过45%).钌催化剂中ZnO晶体对于环己烯选择性达到80%非常重要.催化剂回收循环反应5次时反应性能基本不变,表明低碱度下制备的催化剂具有良好的稳定性,显示了工业化应用前景.     

Effect of zeolite pore morphology on solvent-less alkylation of benzene with 1-hexene

In an attempt to convert the carcinogenic benzene which is almost restricted for its use in gasoline, alkylation reaction with olefin 1-hexene has been conducted on various zeolites. Four zeolites having different pore topology and pore size have been applied as solid acid catalysts for effective production of alkylate in a liquid phase, solvent-less low temperature reaction. The textural properties of all the four zeolites (ZSM-5, MOR, BEA, HY) have been characterized for crystal morphology by TEM, crystal structure by XRD and FTIR, BET for surface area, N₂ sorption for porosity and TPD for acidity. Among the zeolite, BEA possessed high surface area (600.61 m²/g) and enhanced meso pores volume (0.3956 cm³/g) as compared to other zeolite samples. The performance of BEA was also observed to be superior in the liquid phase alkylation of benzene with 1-hexene in a batch reactor under autogenous pressure without using any solvent. At the optimum reaction conditions, the benzene conversion was 86.6 wt% and 3-Phenylhexane, 2-Phenylhexane yield were about 47.9 wt% and 38.7 wt% respectively on this catalyst. The BEA also exhibited longer time-on-stream and reusability performance, thus offers an attractive route for converting benzene into valuable (3-Phenylhexane, 2-Phenylhexane) alkylate product useful for the manufacturing of fine chemicals, dyestuff, detergents and scents.     

Refractive index of benzene and methyl derivatives: temperature and wavelength dependencies

Measurements of the refractive index from 288 to 318 K at five fixed wavelengths, from 656.3 to 404.7 nm, are reported for benzene, toluene (methylbenzene), o-xylene (1,2-dimethylbenzene), m-xylene (1,3-dimethylbenzene), and p-xylene (1,4-dimethylbenzene). We also report the temperature and wavelength dependencies of the refractive index obtained from a least-squares routine. The agreement between the measured and calculated refractive indices lies within the experimental uncertainty.     

Infrared laser-produced carbon-phase shield to oxidation of nanosized titanium monoxide

Pulsed infrared laser-irradiation of titanium monoxide leads to ablation and when carried out in gaseous benzene (1-5 Torr) to simultaneous dielectric breakdown of benzene into low molecular carbonaceous species which allow carbothermal reduction of ablated TiO_x particles and their protection by carbonaceous shell. The deposited particles are characterized by Fourier transform infrared Raman and X-ray photoelectron spectroscopy and by electron microscopy and shown to be stable towards oxidation in air. The reported process can find use in protection of gas-phase produced reactive nanoparticles by carbon phase.