固定床反应器上挤条小晶粒TS-1催化丙烯环氧化反应

采用纳米TS-1母液作为晶种, 在四丙基溴化铵(TPABr)-乙胺廉价水热体系中, 合成出晶粒尺寸为600 nm×400 nm×250 nm的小晶粒钛硅分子筛(TS-1), 用挤条法将其成型, 得到的挤条小晶粒TS-1被用于催化固定床反应器中的丙烯环氧化反应. 采用X射线衍射(XRD)光谱, 傅里叶变换红外(FT-IR)光谱, 紫外-可见(UV-Vis)漫反射光谱及氮气物理吸附对挤条成型的小晶粒TS-1进行表征, 并对丙烯环氧化的最优反应条件进行考察. 其中所考察的条件包括: 反应温度, 压力, 丙烯/H₂O₂摩尔比(n(C₃H₆)/n(H₂O₂)), 丙烯、甲醇及H₂O₂的质量空速(WHSV), 以及NH₃·H₂O浓度. 在所考察的范围内, 温度对环氧丙烷(PO)收率的影响较小, 当反应压力为2.0 MPa, n(C₃H₆)/n(H₂O₂)为4时, 可以得到最高的PO收率. 当丙烯、甲醇及H₂O₂的空速分别为0.93、2.5及0.25 h^-1时, PO在产物中的含量最高. 较低的NH₃·H₂O浓度对高PO收率更有利. 在优化的反应条件下, 对比不同晶粒大小TS-1的催化性能, 并考察了挤条小晶粒TS-1的长期运转性能, 连续反应1000 h, H₂O₂转化率及PO选择性仍能维持在95%以上.     

Enhanced photocatalytic performance of magnetite/TS-1 thin film for phenol degradation

Photocatalytic degradation method is an emerging technique for complete removal of pollutants. Several semiconductor photocatalysts are reported as photocatalysts for industrial wastewater treatment in environmental applications. In this study Magnetite/TS-1 composite materials was used for photocatalytic degradation of phenol. Magnetite nanoparticles (MNP) (10 wt%) were dispersed with nanocrystalline Titanium Silicate-1 zeolite (TS-1). The Magnetite/TS-1 composite materials were characterized with various techniques. The structural analysis reveals the presence of MNP and zeolite-MFI phases in Magnetite/TS-1 composite materials. The average particles size of the magnetite nanoparticles is less than 5 nm and that of the composite nanoparticles are in the range of about 90 nm with micropore volume 0.110 cm³/g and the external surface area 120 m²/g. The photocatalytic experiments were carried out in a thin film flow photoreactor under UV radiation. The results showed that Magnetite/TS-1 composite materials exhibited improved activity for the degradation of phenol compared to TS-1. Preliminary studies proves that aeration is necessary for the photocatalytic reaction. The reaction parameters such as flow rate, pH and phenol concentration are optimized as 8 ml/min, pH 7.0 and 75 mg/L respectively. To understand the active species involved in the degradation of phenol radical scavengers such as NaI, benzoquinone and isopropyl alcohol are used to trap hole (h⁺), superoxide anion radical and hydroxyl radical (OH), respectively. From the obtained results it is envisaged that hydroxyl radicals are predominantly involved in complete oxidation of phenol. The extent of degradation of phenol was determined by measuring the amount of CO₂ formed in the reaction. The results confirms that 99.6 % carbon in phenol is converted to CO₂.     

过渡金属改性的Pd/TS-1催化氢、氧直接合成H_2O_2的性能

利用等体积浸渍法制备了M-Pd/TS-1(M=Ce,La,Pt,Fe,Co,Ni,Cr,Mn,Zn,Cd,Cu)系列催化剂,并将制得的催化剂用于常压下氢、氧直接合成过氧化氢的反应。考察了M的类型及负载量对M-Pd/TS-1催化剂催化性能的影响。结果表明,M选Ce时,催化剂的性能最好。Ce的最佳掺入量,n_(Ce)/(n_(Ce)+n_(Pd))=0.5%。对Ce改性与未改性的催化剂进行了TEM及静态化学吸附分析,结果表明,掺入Ce可使Pd在TS-1分子筛表面的粒度及分散度得到改善。考察了n_(O_2)/n_(H_2)比,气体流量,反应时间等反应条件对H_2转化率、H_2O_2选择性及收率的影响。在相对优化的工艺条件下,即n_(O_2)/n_(H_2)=3,气体流量为25 mL·min~(-1),反应时间为3 h时,H_2O_2,的收率可达到25.7%,TOF值为18.7 mol·mol~(-1)·h~(-1),此时溶液中H_2O_2的质量百分数为0.8%。     

The Reaction of o-Benzyne with Vinylacetylene: An Unexplored Way to Produce Naphthalene

The mechanism and kinetics of the reaction of ortho-benzyne with vinylacetylene have been studied by ab initio and density functional CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6-311G(d,p) calculations of the pertinent potential energy surface combined with Rice-Ramsperger-Kassel-Marcus - Master Equation calculations of reaction rate constants at various temperatures and pressures. Under prevailing combustion conditions, the reaction has been shown to predominantly proceed by the biradical acetylenic mechanism initiated by the addition of C₄H₄ to one of the C atoms of the triple bond in ortho-benzyne by the acetylenic end, with a significant contribution of the concerted addition mechanism. Following the initial reaction steps, an extra six-membered ring is produced and the rearrangement of H atoms in this new ring leads to the formation of naphthalene, which can further dissociate to 1- or 2-naphthyl radicals. The o-C₆H₄+C₄H₄ reaction is highly exothermic, by ∼143 kcal/mol to form naphthalene and by 31–32 kcal mol⁻¹ to produce naphthyl radicals plus H, but features relatively high entrance barriers of 9–11 kcal mol⁻¹. Although the reaction is rather slow, much slower than the reaction of phenyl radical with vinylacetylene, it forms naphthalene and 1- and 2-naphthyl radicals directly, with their relative yields controlled by the temperature and pressure, and thus represents a viable source of the naphthalene core under conditions where ortho-benzyne and vinylacetylene are available.     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. I. Effects of reaction conditions on the polymerization rate and polymer molecular weight

The radiation-induced emulsifier-free emulsion polymerization of tetrafluoroethylene was carried out at an initial pressure of 2–25 kg/cm², temperature of 30–110°C, and under a dose rate of 0.57 × 10⁴?3.0 × 10⁴ rad/hr. The rate of polymerization was shown to be proportional to 1.0 and 1.3 powers of the dose rate and initial pressure, respectively, and is maximal at about 70°C. The molecular weight of polytetrafluoroethylene (PTFE) lies in the range of 10⁵?10⁶, increases with reaction time in the early stage of polymerization, and is maximal at 70°C but is almost independent of the dose rate. An interesting discovery is that PTFE, a hydrophobic polymer, forms as a stable latex in the absence of emulsifier. When PTFE latex coagulates during polymerization under certain conditions, the polymerization rate decreases, probably because polymerization proceeds mainly on the polymer particle surface. The observed rate acceleration and successive increase in polymer molecular weight may be due to slow termination of propagating radicals in the rigid PTFE particles.     

A kinetic study of the decomposition of HNO3 and its reaction with NO

The rate of reaction between NO and HNO₃ and the rate of thermal decomposition of HNO₃ have been measured by FTIR spectroscopy. The measurements were made in a teflon lined batch reactor having a surface to volume ratio of 14 m^?1. During the experiments, with initial HNO₃ concentrations between 2 and 12 ppm and NO concentrations between 2 and 30 ppm, a reactant stoichiometry of unity and a first order NO and HNO₃ dependence were confirmed. The observed rate constant for the reaction at 22°C and atmospheric pressure was determined to 1.1 (±0.3) 10^?5 ppm^?1 min^?1. At atmospheric pressure, HNO₃ decomposes into NO₂ and other products with a first order HNO₃ dependence and with a rate constant of 2.0 (±0.2) 10^?3 min^?1. The apparent activation energy for the decomposition is 13 (±4) kJ mol^?1.     

微波法合成氟改性TS-1及其催化环己酮氨肟化性能

通过微波辅助法制备了含氟的TS-1（F-TS-1-M）,并与传统方法制备的氟改性TS-1（F-TS-1-T）,微波处理的TS-1（TS-1-M）和未改性TS-1进行比较.XRD、DR UV-Vis、XPS表明F-TS-1-M和TS-1-M分子筛上的部分非骨架钛转变为骨架钛,这是由于微波的选择性效应可以不同程度地活化Ti—O和Si—O键;¹⁹F MAS NMR证实了F-TS-1-M分子筛中氟元素是以Si-F和SiF₆^2-的形式存在;²⁹Si MAS NMR表明F-TS-1-M分子筛的骨架缺陷位和表面羟基减少,Py-FT-IR结果表明F-TS-1-M的Lewis酸性和疏水性高于F-TS-1-T、TS-1-M和TS-1.在环己酮氨肟化的反应中表现出优异的催化性能.     

Sr5[NbN4]N ‐ A Nitridoniobate(V) Nitride Containing Isolated [NbN4]7‐ Tetrahedra and Octahedral Chains 1(Sr4Sr2/2N7+)

Sr₅[NbN₄]N (transparent, red single crystals) was synthesized by reaction of Sr2N with Nb under nitrogen at ambient pressure and 1223 K. The crystal structure was solved and refined in the space group Pbcm (no. 57), Z = 4, with lattice constants a = 646.6(3) pm, b = 1792.5(9) pm, c = 729.8(4) pm, and R = 0.019, wR² = 0.034. The crystal structure contains both isolated tetrahedra [NbN₄]^7‐ as well as chains of corner sharing octahedra 1(Sr₄Sr_2/2N⁷⁺). Strontium is irregularly coordinated by nitrogen (CN = 4 ‐ 6, Sr‐N: 252.3(4) ‐ 340.8(3) pm); nitrogen is located in a distorted octahedral environment by strontium and niobium (Nb‐N: 194.5(4) ‐ 199.2(2) pm). By formal reduction of the structural building units to their centers a close structural relationship to both the NiAs and the CaSi type structure is evident.     

Pressure dependence of the rate coefficients and product yields for the reaction of CH3CO radicals with O2

Relative rate coefficients for the reaction of acetyl (CH₃CO) radicals with O₂ (k₄) and Cl₂ (k₇) have been obtained at 298 K and 228 K as a function of total pressure, using FTIR/environmental chamber techniques. Measured values of k₄/k₇ were placed on an absolute basis using k₇=2.8×10⁻¹¹ exp(−47/T) cm³ molec⁻¹ s⁻¹. At 298 K, the value of k₄ is constant ((7±2)×10⁻¹³ cm³ molec⁻¹ s⁻¹) at pressures from 0.1 to 2 torr, then increases to a high pressure limiting value of (3.2±0.6)×10⁻¹² cm³ molec⁻¹ s⁻¹, which is approached at pressures above 300 torr. At 228 K, the low-pressure value of k₄ increases by about 20–30%, while the high pressure value remains unchanged. Experiments designed to elucidate the products of reaction (4) as a function of pressure at 298 K indicate that the reaction occurs via a concerted mechanism in which CH₃CO radicals combine with O₂ to give an excited acetylperoxy radical (CH₃COO₂*) which is increasingly stabilized at high pressure at the expense of a low pressure decomposition channel. The yield of acetylperoxy radicals from reaction (4) decreases from >95% at pressures above 100 torr, to about 90% at 60 torr, and 50% at 6 torr. Indirect evidence for formation of OH radicals from the low pressure decomposition is presented, although the carbon-containing coproduct(s) of this channel could not be identified. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 655–663, 1997.     

Voltammetric characterization of structural titanium species in zeotypes

Ti⁴⁺ ions structurally contained in titanium silicalite (TS-1) and ETS-10 samples, two nanoporous materials, have been studied by means of voltammetric measurements. Both structurally tetrahedral and octahedral Ti⁴⁺ ions show electrochemical response. In particular, by using acid solutions, it was possible to distinguish, in TS-1, between signals coming from different titanium species. Finally, it has been proven that the use of acid solutions allows us to discriminate between Ti⁴⁺ ions in TS-1 and in ETS-10 since only the former is able to coordinate water molecules, the reduction of which can be monitored by the presence of a peak at −600 mV/SSE.     

The hydroxyl radical reaction rate constant and products of cyclohexanol

The gas phase reaction of the hydroxyl radical (OH) with cyclohexanol (COL) has been studied. The rate coefficient was determined to be (19.0 ± 4.8) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ (at 297 ± 3 K and 1 atmosphere total pressure) using the relative rate technique with pentanal, decane, and tridecane as the reference compounds. Assuming an average OH concentration of 1 × 10⁶ molecules cm⁻³, an atmospheric lifetime of 15 h is calculated for cyclohexanol. Products of the OH + COL reaction were determined to more clearly define COL's atmospheric degradation mechanism. The observed products and their formation yields were: cyclohexanone (0.55 ± 0.06), hexanedial (0.32 ± 0.15), 3‐hydroxycyclohexanone (0.31 ± 0.14), and 4‐hydroxycyclohexanone (0.08 ± 0.04). Consideration of the potential reaction pathways suggests that each of these products is formed via hydrogen abstraction at a different site on the COL ring. The products and their relative amounts are discussed in light of the predicted yields for each reaction channel. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 108–117, 2001     

A kinetic study of the reactions of the hydrogen atom with the cyclohexadiene isomers in the gas phase

Absolute values of the rate constants for the reaction of hydrogen atoms with cyclic olefins in the gas phase have been measured in a discharge-flow system under 3.5, 16, and 22 torr Ar at 23°C. The attenuation of hydrogen atom concentration in the reaction tube in the presence of a large excess of olefin was measured with an ESR spectrometer, and the products were analyzed by gas chromatography. Cyclic C₆ hydrocarbons were the only significant products obtained when the hydrogen atom concentration was 2.6 × 10^?10 mole/1., the olefin concentration was in the range of 9 to 22 × 10^?8 mole/1., and the pressure was 16 torr Ar. The values for the rate constants for reaction with cyclohexadiene-1,3, cyclohexadiene-1,4, and cyclohexene are, respectively, (9 ± 2) × 10⁸, (12 ± 1) × 10⁸, and (6 ± 1) × 10⁸ l./mole-sec, and they are not changed significantly by a sixfold change in total pressure. The fraction of the total interaction that proceeds by addition is 84% in the cyclohexadiene-1,3 system, but only 18% in the cyclohexadiene-1,4 system, and the cyclohexadienyl radical is therefore the dominant radical species in the latter system. The pattern of interaction between the hydrogen atom and the cyclohexadienyl radical was determined, and comprises 65% of disproportionation, and 13% and 23% of combination to yield cyclohexadiene-1,3 and cyclohexadiene-1,4, respectively. These results are consistent with the general patterns of reactivity emerging from studies of the reactions between free radicals and olefins in related systems.     

The atmospheric chemistry of the HC(O)CO radical

The chemistry of the HC(O)CO radical, produced in the oxidation of glyoxal, has been studied under conditions relevant to the lower atmosphere using an environmental chamber/Fourier Transform infrared spectrometric system. The chemistry of HC(O)CO was studied over the range 224–317 K at 700 Torr total pressure and was found to be governed by competition between unimolecular decomposition [to HCO and CO, reaction (5)] and reaction with O₂ [to form HO₂ and 2CO, reaction (6a), or HC(O)C(O)O₂, reaction (6b)]. The rate coefficient for decomposition relative to that of reaction with O₂ increases with increasing temperature. Assuming a value for k₆ of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, the following expression for the unimolecular decomposition is obtained at 700 Torr, k₅ = 1.4⁺⁹/_−1.1 × 10¹² exp(−3160 ± 500/T). The rate coefficients for reactions (6a) and (6b) are about equal, with no strong dependence on temperature. The reaction of HC(O)C(O)O₂ with NO₂ was also studied. Final product analysis was consistent with the formation of HCO, CO₂, and NO₃ as the major products in this reaction; no evidence for the PAN‐type species, HC(O)C(O)O₂NO₂, was found even at the lowest temperature studied (224 K). The UV‐visible absorption spectrum of glyoxal is also reported; results are in substantive agreement with previous studies. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 149–156, 2001     

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D₄), decamethylcyclopentasiloxane (D₅), and dodecamethylcyclohexasiloxane (D₆) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D₄ and D₅ with the OH radical are 1.9 × 10^?12 (95% confidence interval (CI): (1.7–2.2) × 10^?12) and 2.6 × 10^?12 (CI: (2.3–2.9) × 10^?12) cm³ molecule^?1 s^?1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D₆ is 2.8 × 10^?12 (CI: (2.5–3.2) × 10^?12) cm³ molecule^?1 s^?1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D₅ were 33% higher than for D₄ (CI: 30–37%), whereas the rates for D₆ were only 8% higher than for D₅ (CI: 5–10%). The activation energies of the reactions of D₄, D₅, and D₆ with OH were not statistically different and had a value of 4300 ± 2800 J/mol.     

The linear relations and living feature in cationic ring-opening copolymerization of epoxy/THF system

The cationic copolymerization of diglycidyl ether of bisphenol-A with tetrahydrofuran (THF) initiated by phosphotungstic acid H₃PW₁₂O₄₀ (PW₁₂) was in situ investigated by Fourier transform near infrared spectroscopy. The gelation point of the reaction was determined by rheometrics mechanical spectroscopy. It was found that the conversion of epoxy group at 4,530 and 6,073 cm^?1 increased linearly with reaction time up to a high conversion (~90%), during which gelation (at ~51%) had no effect. The slope-indicating reaction rate of epoxy group also increased linearly with the content of PW₁₂. In addition, the peak splitting pattern of the overlapping C–H vibration region (5,700–6,200 cm^?1) was developed here. The peak-splitting analysis showed that the epoxy behavior agreed with above results, but the reaction rate of THF slowed down gradually with reaction time as the viscosity of the system increased. The results suggest that the kinetic behavior of cationic polymerization shows living feature of the propagating chains in this system and near infrared (NIR) technology could be applied to study such kinetic behavior.     

The first example of aldol reactions between trimethylsilyl enol ethers and aldehydes by the aid of rhodium complex

Crossed aldol reaction of trimethylsilyl enol ether with aldehyde is successfully performed with the aid of catalytic amount of rhodium complex, [(COD)Rh(DPPB)]⁺X⁻ (X = PF₆ and ClO₄) or Rh₄(CO)₁₂, under neutral conditions.     

Radiation-induced heterogeneous polymerization of ethylene in the presence of ethyl alcohol

The radiation-induced heterogeneous polymerization of ethylene in ethyl alcohol was carried out in a reactor with a capacity of 100 ml under the following reaction conditions: temperature, 24 ± 3°C; pressure, 200–400 kg/cm²; amount of ethyl alcohol, 30–70 ml; dose rate, 3.7 × 10⁴?1.05 × 10⁵ rad hr. The effects of amount of ethyl alcohol, pressure, and dose rate on the rate of polymerization at the steady state, the amount of polymerized monomer, the molecular weight of polymer, and the number of polymer chains were studied compared with the results obtained in the polymerization in tert-butyl alcohol. It was found that there is an acceleration period in the early stage of reaction followed by a steady state. The rate of polymerization was maximum when about 50 ml of ethyl alcohol was used. The molecular weight of polymer increased with a decrease in the amount of ethyl alcohol. The dependences of pressure (p) and dose rate (I) on the rate of polymerization at steady state (R_s) and the molecular weight of polymer (M?_n) were expressed as follows; R_s ∝ p^0.74, M?_n ∝ p^0.3?0.4, R_s ∝ I^0.9 and M?_n ∝ I^{?0.1 ?0.0}. The results were analyzed by a kinetic treatment based on a reaction mechanism containing both first-and second-order terminations. The rate constant of first-order termination by radical occlusion was considerably larger than that in the polymerization in tert-butyl alcohol, because the affinity of ethyl alcohol for polyethylene is smaller than that of tert-butyl alcohol. It was found that chain transfer to ethyl alcohol takes place easily and the G value of ethyl alcohol for initiation is larger than 1.5.     

纳米Cu2O催化二苯甲烷二氨基甲酸苯酯无溶剂热分解制备二苯甲烷二异氰酸酯

研究了无溶剂条件下纳米Cu₂O催化二苯甲烷二氨基甲酸苯酯(MDPC)热分解制备二苯甲烷二异氰酸酯(MDI),考察了纳米Cu₂O的制备条件与反应条件对MDPC热分解反应性能的影响.结果表明,水解法制备的纳米Cu₂O在Ar中于300℃焙烧2h,其催化性能最佳;最佳的反应条件为Cu₂O用量为原料总重的0.06%,反应温度220℃,反应压力0.6kPa,反应时间12min,此时MDPC转化率达到99.8%,MDI选择性86.2%.     

Die Reaktion von 4,6-Dinitroisophthalaldehyd und 4,6-Dinitroisophthalonitril mit Pyridin

The reaction of 4,6-dinitroisophthalaldehyde and 4,6-dinitroisophthalonitrile with pyridine 4, 6-Dinitroisophthalaldehyde ( 4 ) gives on reaction with pyridine 4,6-diformyl-3-(1′-pyridinio)-1-phenolate ( 5 ), whereas 4,6-dinitroisophthalonitrile ( 7 ) gives under the same conditions one main product: 3-(1′)-pyridinio-4, 6-dicyano-1-phenolate ( 10 ) and two side products: 2-(1′-pyridinio)-4, 6-dicyano-3-nitro-1-phenolate ( 11 ) and 4, 6-dicyano-3-nitro-1-phenol ( 12 ). The new structures were elucidated by ¹H-NMR. and ¹³C-NMR. spectroscopy.