氟里昂替代物HFC-134a和HFC-152a的多光子电离研究

氟里昂和哈龙等含氯和溴的化合物是导致臭氧层耗损的主要物种 ,其替代物的研究已引起普遍关注 .与此同时 ,国际社会对于全球气候的变化也愈加关注 ,这对今后消耗臭氧层物质 ( ODSs)替代品的选择提出了更高要求 ,即既要满足保护臭氧层的要求 ,又要满足防止气候变化的要求 .目前 ,在制冷行业中已开始使用的消耗臭氧层物质 CFC- 1 2 ( CF2 Cl2 )的替代物主要有氢氯氟烃 ( HCFCs)和氢氟烃( HFCs) ,而 HCFCs是过渡性替代物 ,根据蒙特利尔议定书的规定将于 2 0 4 0年全部被淘汰 [1] ,因此消耗臭氧潜值 ( ODP)为 0 ,全球变暖潜值 ( GWP)…     

医用hfc-134a中微量杂质的定性、定量分析

气相色谱;医用hfc-134a;定性分析;定量分析     

中心切割式多维气相色谱/质谱系统中中点限流器的改进及其在卷烟烟气中苯并[a]芘检测中的应用

对多维气相色谱的核心部件中点限流器进行了改进,用一段0.25mm i.d.毛细管柱取代石墨限流管,Y形玻璃压合连接器取代两孔石墨垫,显著提高了一维色谱保留时间的稳定性,保证了中心切割范围的准确性,且消除了石墨对苯并[a]芘的吸附残留。同时,将本系统应用于卷烟烟气中苯并[a]芘的检测。采用剑桥滤片捕集烟气粒相物,环己烷萃取,以氘代苯并[a]芘为内标,直接用中心切割式多维气相色谱/质谱(MDGC/MS)法测定。该法线性关系良好,其线性范围为1.47～29.4μg/L(r2=0.999 9);重复性好,测得实际样品中苯并[a]芘含量的相对标准偏差(RSD)为1.94%;回收率为90.74%～101.86%;检出限和定量限分别为0.31ng/支及1.03ng/支,可以满足检测要求。应用本系统对2R4F参比卷烟烟气中苯并[a]芘进行了检测,结果与文献报道值基本一致。     

Structures and Properties of trans-1,3,3,3-Tetrafluoro- propene (HFO-1234ze) and 2,3,3,3-Tetrafluoropropene (HFO-1234yf) Refrigerants

The refrigerant trans-1,3,3,3-tetrafluoropropene (HFO-1234ze) is used as a replacement for former cooling agents that have been phased-out due to their global warming potential or ozone depleting potential. Although it is used on a large scale, only a few vibrational data and no structural data of HFO-1234ze are known. We report structure determinations based on low-temperature single-crystal X-ray diffraction data as well as gas-phase diffraction data of HFO-1234ze and HFO-1234yf (2,3,3,3-tetrafluoropropene). Furthermore, vibrational spectra of HFO-1234ze in all phases are described. The results are discussed together with quantum-chemical calculations on the PBE0/cc-pVTZ level of theory. Combustion experiments of HFO-1234ze show carbonyl difluoride, carbon dioxide and hydrogen fluoride to be the main combustion products.     

HFO-1234yf as a CF3 Building Block: Synthesis of Trifluoromethyl Quinoline and Chromene Derivatives from Trifluoromethyl-ynones

Trifluoromethyl ynones derived from the refrigerant gas HFO-1234yf (2,3,3,3-tetrafluoropropene) react with nucleophiles via a Michael-type addition process and the allenolate intermediate formed reacts intramolecularly with a carbonyl group to form heterocyclic derivatives. Thus, reaction of 2-amino and 2-hydroxyl benzaldehyde or ketone substrates with trifluoromethyl ynone derivatives gives trifluoromethyl quinoline and chromene products by a one-pot tandem ring closing sequence, forming pharmaceutically relevant structures from an inexpensive starting material without the need for transition metals or column chromatography. The 2-trifluoromethylquinoline products also show unusual fluxional behaviour, which was explored through 2-D NMR and X-ray crystallographic studies.     

Equation of state for hydrofluorocarbon refrigerant mixtures of HFC-125/143a,HFC-125/134a,HFC-134a/143a and HFC-125/134a/143a

Equations of state (EOSs) in the form of dimensionless Helmholtz free energy have been developed for the binary hydrofluorocarbon (HFC) refrigerant mixtures HFC-125/143a, HFC-125/134a, HFC-134a/143a and for the ternary refrigerant mixture HFC-125/134a/143a in the present work. These EOSs are effective in the temperature and pressure ranges where the experimental measurements covered, i.e., 200 K⩽T⩽413 K, P⩽35 MPa for HFC-125/143a and HFC-125/134a; 243 K⩽T⩽413 K, P⩽17 MPa for HFC-134a/143a and HFC-125/134a/143a. Experimental measurements in both single-phase and two-phase regions are represented by the present EOSs within their estimated uncertainties.     

Destruction of Freon HFC-134a Using a Nozzleless Microwave Plasma Source

In this paper, results of the pyrolysis of Freon HFC-134a (tetrafluoroethane C₂H₂F₄) in an atmospheric pressure microwave plasma are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to produce plasma for the destruction of Freon HFC-134a. The processed gaseous Freon HFC-134a at a flow rate of 50–212 l min⁻¹ was introduced to the plasma by four gas ducts which formed a swirl flow in the plasma reactor (a quartz cylinder). The absorbed microwave power was 0.6–3 kW. The experimental results showed that the Freon was converted into carbon black, hydrogen and fluorine. The total conversion degree of HFC-134a was up to 84% with selectivity of 100% towards H₂, F₂ and C₂, which means that there was no conversion of HFC-134a into other hydrocarbons. The Freon destruction mass rate and corresponding energetic mass yield were up to 34.5 kg h⁻¹ and 34.4 kg per kWh of microwave energy absorbed by the plasma, respectively.     

氟里昂134a的真空紫外光电离和光解离的同步辐射研究

利用同步辐射真空紫外光研究了氟里昂134a(CH₂FCF₃)的光电离和光解离过程,通过测量各离子的光电离效率曲线,得到了该分子的电离能(12.68±0.04)eV和所有碎片离子的出现势,运用Gaussian-03计算了母体和中性碎片及相应离子的电子态、对称性和能量.结合理论计算结果对离子出现势的理论值和实验值进行了比较,分析了母体离子可能的光解离通道.     

Performance of a Diesel Locomotive Waste-Heat-Powered Adsorption Air Conditioning System

An innovative exhausted-heat-powered solid adsorption air conditioning system with zeolite-water as working pair is designed for providing air-conditioning for the driver's cab of a diesel locomotive. Only one adsorber is used in the system and a cold storage water tank is attached to provide cooling during generation process to ensure the continuous cooling output. Experiments on the laboratory prototype have been carried out and a mean cooling power output of about 3.3 kW is obtained when the condensing temperature and the evaporating temperature are 40°C and 7°C respectively. The influences of some operating conditions on the system performance are analyzed by simulation and experiments. The results of the performance testing of the prototype installed in a diesel locomotive are also discussed as well. An average cooling power of 4.1 kW is got under typical summer condition. It is proved that such a system is quite competitive even if a little bit heavier.     

Energy and exergy performance comparison of different HFC/R1234yf mixtures in vapor-compression cycles

Journal of Thermal Analysis and Calorimetry - To increase the COP and volumetric capacity of hydrofluoroolefins while reducing the global warming potential (GWP) of hydrofluorocarbons (HFCs), four...     

Infrared band strengths and their temperature dependence of the hydrohalocarbons HFC-134a,HFC-152a,HCFC-22, HCFC-123 and HCFC-142b

The absolute strengths of the IR absorption bands of five halocarbons, proposed as substitutes of chlorofluorocarbons, have been measured at 293, 273 and 233 K in the wavelength region 600–1500 cm⁻¹. The band strengths were derived from measurements performed using an FT-IR spectrometer operating at 0.1 cm⁻¹ instrumental resolution. The values obtained are compared to those from previous studies. Only a slight temperature dependence was observed, indicating a small increase of the band strengths at decreasing temperatures.