氟气及其应用

简叙了氟气的性质及其制备方法,介绍了氟气在含氟无机材料、含氟精细化学品、含氟聚合物材料及半导体领域应用,分析了氟气及其在下游产品的应用趋势。认为随着对氟气安全性不断认知和掌控,用氟气氟化将成为氟化工艺中重要方法,在稳定无机氟化试剂制备、含氟有机化合物高效制备、新能源用氟化石墨制备和作为半导体清洁气体等方面发挥重要作用。     

氟气在直接氟化反应中的应用

介绍了氟气的性质及其应用,同时介绍了氟气在无机氟化反应和有机氟化反应中的应用。     

氟化新途径

氟是一种强氧化剂,用氟气氟化芳烃时,往往同时破坏芳烃成焦油,致使氟化芳烃的收率很低。专利EP-A2-0512715公开了将氟气稀释(如氮气)制备芳烃一氟化物的方法,收率很高。以前曾用溶剂低温法来进行芳烃氟化反应,其难点仍然是溶剂被氧化而生成焦油。     

PVC树脂氟化后的加工性能及热稳定性

采用氟气通过PVC树脂层,制得PVC树脂颗粒表面氟化的PVC树脂,研究了氟气流量、通氟气时间、氟气含量对PVC干混料熔融因数F的影响,通氟气时间对PVC干混料热稳定时间的影响,并展望了氟化PVC树脂的应用前景。试验得出的最佳氟化反应条件为:V(N2)∶V(F2)=9∶1,氟气流量为15 mL/min,通氟气时间为4 h;制得的氟化PVC干混料的熔融因数F提高了18%,热稳定时间提高了23%。     

五氟化碘的合成方法研究

对五氟化碘的性质、应用、国内外研究现状及主要制备方法进行了简单的介绍。主要制备方法有固体碘在氟气中的燃烧反应、液体碘在氟气中的燃烧反应、氟气处理烷基碘化物法等,其中碘在氟气中的燃烧反应是最为常用且实现工业化的制备方法。     

氟气在制备含氟有机物中的应用

重点介绍了近年来氟气直接氟化法在制备含氟的脂肪族、芳香族、杂环化合物以及在聚合物表面改性中的应用进展,同时介绍了微反应器技术在直接氟化反应中的应用情况。     

氟化石墨工艺技术研究

气相法制备氟化石墨由于工艺简单、产品纯度高而成为合成氟化石墨最常用的方法。氟化石墨的合成过程涉及高温与活性单质氟气两方面的因素,安全控制十分重要。从原料、反应时间、反应温度、反应设备和纯化方法等方面对合成氟化石墨的工艺技术进行对比,旨在避免生产过程中出现潜在的危险,寻求提高氟化石墨产品质量的新方法,提升氟化石墨整体制备工艺的安全性。     

四氟化硫的制备和提纯方法

评述了四氟化硫的制备和提纯方法。四氟化硫的制备方法按氟来源可分为五种制备方法：氟气氟化法、氟化氢氟代法、有机碱氢氟酸盐氟代法、金属氟化盐氟代法和非金属氟化物氟化法。四氟化硫的提纯方法可分为汞结合法、吸收法和高温老化法。     

电解氟化及其下游精细氟化工产品(待续)

介绍了电解氟化法制备含氟精细化学品的特点,电解氟化得到R_f基团单一,所生成的衍生物有高憎油憎水性、高溶解性、表面改性能力大,虽电耗高、成本较高,但在某些领域具有不可替代性。叙述了含氟表面活性剂和PFOS、PFOA及其衍生物,氟气、氟化石墨及新能源材料,六氟化硫、三氟化氮等电解氟化法制备的含氟精细化学品的特性、用途、发展历程,以及国内外生产、应用概况。     

固相法合成氟化碳纳米管

以聚四氟乙烯为原料,利用固相法对碳纳米管进行氟化,制备功能化的碳纳米管.采用红外光谱(FTIR)、X射线衍射(XRD)、X衍射光电子能谱(XPS)对氟化碳纳米管进行了表征.结果表明在碳纳米管表面生成了C-F键,成功地制取了氟化碳纳米管,氟原子的摩尔分数达到3.59%.此"固相法"不同于以剧毒单质氟气作为氟源的"气相法",它具有制备方法简单、操作安全的特点,对促进碳纳米管的改性和应用具有非常重要的意义.     

Thermal fluorination effects on carbon nanotubes for preparation of a high-performance gas sensor

A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100 ∼ 1000 °C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000 °C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000 °C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs.     

The effect of nanostructure on the thermal properties of fluorinated carbon nanofibres

Using thermogravimetic analysis in air, the thermal properties of fluorinated carbon nanofibres have been investigated. The fluorination level, the C–F bonding, the number of structural defects and the distribution of fluorine atoms in the carbon matrix have been modified using three fluorination routes, (i) a direct process using a flux of pure molecular fluorine F₂ (dynamic process), (ii) a filling of a closed reactor by this reactive gas (static process) and (iii) controlled fluorination using the thermal decomposition of a solid fluorinating agent TbF₄. At given fluorine contents, only the location of the fluorine atoms within the nanofibre changes the thermal stability, which can be increased up to 480 °C; such improvement is obtained when the fluorinated regions are located in the outer shell (tubes).     

油气储运中直接氟化高密度聚乙烯的应用

分析了氟元素和氟碳键的特性,从分子层面上揭示了直接氟化高密度聚乙烯结构特征对阻隔耐油性的影响;综述了直接氟化高密度聚乙烯在油气管道、塑料油箱和油罐基础防渗膜等油气储运领域中的应用;指出制订氟化标准和规范、关注环境保护是当务之急。     

XPS characterization of surface fluorinated poly(4-methyl-1-pentene)

The fluorinated surface layer of poly(4-methyl-1-pentene) membranes exposed to a dilute stream of fluorine gas has been characterized with X-ray photoelectron spectroscopy. The concentration and profile of reacted fluorine as a function of exposure time is determined. A computer routine was employed to deconvolute the poorly resolved carbon spectra after various fluorine exposure times. The concentrations of mono-, di-, and trifluorocarbon groups thus determined were used to propose specific structures of PMP at the surface after 1 and 15 min of fluorination. The carbon spectra collected at electron takeoff angles of 15°, 30°, and 90° were also deconvoluted, giving insight into the placement of fluorine as a function of depth. Oxygen is incorporated into the polymer during the fluorination reaction, and the O1s spectra was deconvoluted to determine how the oxygen is bound.     

A fluorine gas monitoring system for the direct oxy‐fluorination of polyethylene sheets

A new technique is presented to measure the concentration of fluorine in a reaction gas consisting of fluorine, nitrogen, and oxygen in a reaction chamber. The method is described as follows: The gas is directly taken from the chamber using a peristaltic pump and dissolved in a TISAB (total ionic strength adjusted buffer) solution. The concentration of fluorine ion is measured using the selected fluorine ion electrode, the output voltage of which is monitored. The concentration of the fluorine ion and the output voltage follow the Nernst relation so that the measurement of the output voltage of the system enables us to know the concentration of fluorine gas. This technique was applied to monitor the concentration of fluorine gas in the chamber in which a sheet of polyethylene nonwoven fabric was continuously oxy‐fluorinated. The monitored concentration of the fluorine gas as a function of time coincided with the variation of the incorporated fluorine in the sheet measured by X‐ray fluorescence (XRF) spectroscopy after the treatment. This technique can be best used for process control of the continuous oxy‐fluorination of polymeric materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 684–691, 2002     

Changes in the structure and functional groups produced during the fluorination of mesophase microbeads

The mesocarbon microbead (MCMB) fluorides with different fluorine contents were obtained in the temperature range of 100–110 °C in the presence of the mixed gas containing fluorine and nitrogen. The MCMB fluorides were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and elemental analysis. The results showed that the carbon lamination of the MCMBs was severely destroyed, which was indicated by a dramatic increase in the interlayer spacing of the resultant materials from 0.345 nm of the MCMBs to the range of 0.656 to 0.722 nm. Further studies on diversity of functional groups indicated that the whole fluorination reaction process comprises two steps: include a first diffusion of fluorine gas molecules inside the voids formed due to loose packing of MCMB molecules, and then fluorination. The two steps interacted with each other and jointly determined the apparent speed of the reaction. The original lamination structure of the MCMBs was completely destroyed for volume expansion of the resultant materials and diffusion of fluorine/nitrogen mixed gases. The final MCMB fluorides are themselves a conglomeration of particles with diameters ranging from 1 to 3 μm.     

Carbon nanofibres fluorinated using TbF4 as fluorinating agent. Part I: Structural properties

Fluorination of carbon nanofibres (CNFs) under fluorine gas at 480 °C leads to high fluorine content but also to some partial exfoliation. In order to avoid such phenomenon, an alternative route has been performed at temperatures ranged between 420 and 500 °C using a fluorinating agent, i.e. terbium tetrafluoride. The structural properties of the fluorinated CNFs are discussed taking into account the data of ¹³C solid state NMR, Raman spectroscopy, SEM, TEM and XRD. Whatever the fluorination temperature, a fluorinated phase of (CF)_n structural type, is formed contrary to the direct process using F₂ gas for which a (C₂F)_n-type fluorinated phase appeared for fluorination temperatures lower than 450 °C. The progressive release of fluorine atoms from the thermal decomposition of TbF₄ allows an homogenous distribution of the fluorinated part into the CNFs matrix and the formation of a unique (CF)_n type structure. Moreover, for high fluorination temperatures (480 and 500 °C), the fluorination leads to some nanofibres breaking but in no way to exfoliation.     

Gas transport in partially fluorinated low-density polyethylene

Low-density polyethylene film was subjected to direct fluorination on one surface by exposure to a dilute fluorine gas stream for various periods of time. Various analyses indicate partial fluorination of a thin surface layer. The permeability coefficients for He, CO₂, and CH₄ were measured at 35°C. The permeability of He was not changed by fluorination; whereas, values for CO₂ and CH₄ were decreased by as much as two orders of magnitude. The selectivity of transport for gas pairs of different molecular size was greatly improved, suggesting applications of this technique for membrane separation processes.