空气中微量1,1,1,2-四氟乙烷吸附分离的分子模拟

利用实验和巨正则系综蒙特卡罗(GCMC)方法研究了N2/HFC-134a(1,1,1,2-四氟乙烷)二元混合物在活性碳纤维(ACF)内的吸附分离.重点讨论了孔径、压强及温度对HFC-134a吸附选择性的影响,为不同条件下吸附空气中的微量HFC-134a提供了理论参考.结果表明:较小孔径、低压以及低温条件有利于HFC-134a的吸附分离.在常温下,HFC-134a在带有孔径分布的活性碳纤维材料内的吸附选择性可以达到62,表明我们所制备的活性碳纤维材料可以较好地分离空气中微量的HFC-134a.特别地,在常温和0.41×105Pa下,0.75nm的碳孔对HFC-134a的吸附选择性达到了230.因此,为了有效地吸附空气中的HFC-134a,推荐使用小孔径的碳材料.     

合成CFC-12替代物HFC-134a的CrF3/AlF3催化剂研究(V)——CrF3与AlF3的相互作用

由于氟氯烃(CFCs)对大气臭氧层的破坏作用,使得开发CFCs无污染替代品的研究成为热门课题.氢氟烃(HFCs,如HFC-134a)是CFCs的理想替代物.     

Y-Mg-Al-F催化剂用于1,1,1,2-四氟乙烷裂解制备三氟乙烯

采用沉积沉淀法制备了Y-Mg-Al-F催化剂,应用XRD、NH3-TPD和Raman光谱等技术手段对催化剂进行表征,并与AlF3催化剂作比较,且将催化剂应用于四氟乙烷(HFC-134a)裂解制备三氟乙烯反应中。 结果表明,1100 ℃焙烧的Y-Mg-Al-F催化剂具有较高的活性和反应稳定性。 反应温度400 ℃时,四氟乙烷转化率大于25%。 催化剂表面酸性和积碳是影响催化剂活性和稳定性的主要因素。     

气相氟化合成1,1,1,2-四氟乙烷的CrOx-Y2O3催化剂的表征与性能

制备了一系列CrOx-Y2O3催化剂用于气相氟化1,1,1-三氟-2-氯乙烷(HCFC-133a)合成1,1,1,2-四氟乙烷(HFC-134a), 并考察了Y(OH)3、YCl3和Y(NO3)3前躯体对催化剂性能的影响. XRD和UV-Vis光谱实验结果表明, Y前躯体对催化剂表面Cr物种有影响, 其中采用Y(OH)3前躯体的催化剂有利于以高分散的Cr6+形式存在. 研究表明CrOx-Y2O3催化剂在预处理和反应过程中, 部分高价CrOx可转化为CrF3. 催化剂中CrF3含量增加, 导致其转化为活性物种的含量相对减少, 所以其催化活性下降.     

气相氟化合成1,1，1，2－四氟乙烷的CrOx-Y2O3催化剂的表征与性能

制备了一系列CrOx-Y2O3催化剂用于气相氟化1,1,1-三氟-2-氯乙烷(HCFC-133a)合成1,1,1,2-四氟乙烷(HFC-134a),并考察了Y(OH)3、YCl3和Y(NO3)3前躯体对催化剂性能的影响.XRD和UV-Vis光谱实验结果表明,Y前躯体对催化剂表而Cr物种有影响,其中采用Y(OH)3前躯体的催化剂有利于以高分散的Cr6+形式存在.研究表明CrOx-Y2O3催化剂在预处理和反应过程中,部分高价CrOx可转化为CrF3.催化剂中CrF3含量增加,导致其转化为活性物种的含量相对减少,所以其催化活性下降.     

含纳米稀土、铁复合粒子润滑油的摩擦学性能

选择了吐温(Tween)-60、司本(Span)-20、司本(Span)-80和聚醚表面活性剂,配制了纳米稀土(RE)和铁粒子的复合润滑油.采用透射电子显微镜(TEM)观察、测定了纳米稀土、铁粒子形貌和粒径.采用磨损试验机测试了含纳米稀土、铁复合粒子润滑油的摩擦学性能.结果表明纳米稀土与纳米铁粒子比例为11,总浓度为0.6%时该润滑油具有最佳的抗磨、减摩性能.并探讨了其抗磨、减摩机制.     

新型含氟聚醚链修饰的咪唑离子液体的合成及其热稳定性

含氟聚醚链修饰的咪唑与碘代烷烃经季铵化反应高产率地制备了4个新型的含氟聚醚链修饰的咪唑碘盐(3a ～3d);通过3的复分解反应合成了一系列新型的含氟聚醚链修饰的咪唑离子液体盐(4a ～4d,5a～5d),其结构经1 H NMR,19F NMR,IR和元素分析确证.热重分析研究表明,4和5具有较高的热稳定性.     

染料聚醚衍生物结构对其在母体分散染料表面吸附行为的影响

针对商品分散染料面临的问题,本课题组曾设计了染料聚醚衍生物类分散剂。本文主要基于前期的研究工作,对母体染料分散体系进行了分析,主要探讨染料聚醚衍生物结构对其吸附行为的影响。基于吸附行为得到的有关结论,用标度理论推导了染料聚醚衍生物在母体染料颗粒表面的吸附层状态,结果表明,饱和吸附时分子中聚氧乙烯醚链均形成了伸展的构象,吸附层厚度随分子量的增加而增加。同时利用空间稳定理论分析分散体系的胶体化学模型,发现影响体系稳定性的主要因素为吸附层厚度;饱和吸附时染料聚醚衍生物均能为染料粒子提供较强的空间位阻。对聚醚和染料聚醚衍生物溶液在染料表面的吸附行为进行了耗散粒子动力学模拟,结果表明,聚醚和染料聚醚衍生物在水溶液中自聚集和在表面的吸附共存,染料聚醚衍生物较聚醚的疏水性更强,自聚集的趋势更强,同时在染料表面的吸附量也更大;染料聚醚衍生物的疏水性越大,相分离和在表面的吸附越易发生。     

CrOx-Y2O3催化剂中Cr物种对氟氯交换反应性能的影响

用沉积-沉淀法制备了CrOx-Y2O3催化剂, 考察焙烧气氛及温度对1,1,1-三氟-2-氯乙烷(HCFC-133a)气相氟化合成1,1,1,2-四氟乙烷(HFC-134a)催化性能的影响. 采用拉曼光谱、X射线粉末衍射(XRD)等表征手段观察了催化剂中铬物种价态的变化情况. 结果表明, 先氮气后空气中不同温度(T)焙烧的催化剂(NAT), 随着空气中焙烧温度的升高, Cr物种由CrO3向YCrO4、YCrO3转变. 500 ℃焙烧的NA500催化剂虽然活性低于直接在空气中350 ℃焙烧的催化剂(A350), 然而前者的反应稳定性明显高于后者. 这归因于YCrO4物种在氟化过程中生成的活性物种既不易流失并且表面不容易结炭.     

新型汽车发动机油用添加剂的研究进展

本文介绍了汽车发动机油用添加剂尤其是多功能添加剂的发展概况、作用机理、种类、结构及应用效果，并对未来润滑油添加剂的发展方向提供了一些参考，为我国润滑油品的高档化发展提出了几点想法。     

亚磷酸酯对新型冷冻机油抗磨性能的影响

本文合成了一系列短链、长链和大分子的亚磷酸酯，用Timken试验机和扫描电镜研究了它们对新型冷冻机油抗磨性能的改进作用。     

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.     

Isothermal phase equilibria for the (HFC-32 + HFC-134a) mixed-gas hydrate system

Isothermal phase equilibria (pressure-composition relations in hydrate, gas, and aqueous phases) in the {difluoromethane (HFC-32) + 1,1,1,2-tetrafluoroethane (HFC-134a)} mixed-gas hydrate system were measured at the temperatures 274.15 K, 279.15 K, and 283.15 K. The heterogeneous azeotropic-like behaviour derived from the structural phase transition of (HFC-32 + HFC-134a) mixed-gas hydrates appears over the whole temperature range of the present study. In addition to the heterogeneous azeotropic-like behaviour, the isothermal phase equilibrium curves of the (HFC-32 + HFC-134a) mixed-gas hydrate system exhibit the negative homogeneous azeotropic-like behaviour at temperatures 279.15 K and 283.15 K. The negative azeotropic-like behaviour, which becomes more remarkable at higher temperatures, results in the lower equilibrium pressure of (HFC-32 + HFC-134a) mixed-gas hydrates than those of both simple HFC-32 and HFC-134a hydrates. Although the HFC-134a molecule forms the simple structure-II hydrate at the temperatures, the present findings reveal that HFC-134a molecules occupy a part of the large cages of the structure-I mixed-gas hydrate.     

An equation of state for hydrogen fluoride

Using a similar approach as Lencka and Anderko [AIChE J. 39 (1993) 533], we developed an equation of state for hydrogen fluoride (HF), which can correlate the vapor pressure, the saturated liquid and vapor densities of it from the triple point to critical point with good accuracy. We used an equilibrium model to account for hydrogen bonding that assumes the formation of dimer, hexamer, and octamer species as suggested by Schotte [Ind. Eng. Chem. Process Des. Dev. 19 (1980) 432]. The physical and chemical parameters are obtained directly from the regression of pure component properties by applying the critical constraints to the equation of state for hydrogen fluoride. This equation of state together with the Wong–Sandler mixing rule as well as the van der Waals one-fluid mixing rule are used to correlate the phase equilibria of binary hydrogen fluoride mixtures with HCl, HCFC-124, HFC-134a, HFC-152a, HCFC-22, and HFC-32. For these systems, new equation of state with the Wong–Sandler mixing rule gives good results.     

Shear viscosity of Stockmayer fluid: Application of integral equations method to Vesovic–Wakeham scheme

In our previous works, we applied the integral equations method to calculate transport properties of nonpolar fluids such as Lennard–Jones (12-6) fluid [R. Khordad, Physica A 387 (2008) 4519, M.M. Papari, R. Khordad, Z. Akbari, Physica A 388 (2009) 585]. The present work is a continuation of our studies on transport properties of polar fluids. We use the Stockmayer potential and examine theoretically the viscosity and pressure of several refrigerant mixtures such as R125 + R143a, HFC-125 + HFC-134a, HFC-125 + HFC-32, and HFC-134a + HFC-32. We solve numerically the Ornstein–Zernike (OZ) equation using the hypernetted-chain approximation (HNC) for binary fluid mixtures and obtain the pair correlation functions. Finally, the density and temperature dependence of shear viscosity and pressure are studied using Vesovic–Wakeham method and compared with experimental results. According to the results obtained from the present work reveals that the integral equations method is suitable for predicting the pressure and shear viscosity of this class of fluids.     

Decomposition of hydrofluorocarbons in a dielectric-packed plasma reactor

This study investigated the decomposition of hydrofluorocarbons (HFCs) having high global warming potentials by using a dielectric-packed-bed nonthermal plasma reactor with barium titanate beads as the packing material. The target HFCs were 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1-difluoroethene (HFC-132a). The effects of several parameters such as reaction temperature, oxygen content, and initial concentration on the HFC decomposition efficiency were evaluated. There was essentially no temperature dependence of the HFC decomposition efficiency in the range 150-250 degrees C. The optimum oxygen content for HFC decomposition was found to be about 0.5 vol %. Variations in the initial concentration did not affect the decomposition efficiency. The decomposition products were analyzed, and some decomposition pathways were elucidated. The energy requirements for the decomposition of HFC-134a and HFC-132a were found to be 0.038 and 0.062 mol MJ-1, respectively, based on the initial concentrations of 200 and 120 ppm (parts per million, volumetric).     

Phase equilibria of 1,1,1-trifluoroethane (HFC-143a) + 1,1,1,2-tetrafluoroethane (HFC-134a), and + 1,1-difluoroethane (HFC-152a) at 273.15, 293.15, 303.15, and 313.15 K

Isothermal vapor–liquid equilibrium data were determined for the binary systems of 1,1,1-trifluoroethane (HFC-143a)+1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1,1-trifluoroethane (HFC-143a)+1,1-difluoroethane (HFC-152a) at 273.15, 293.15, 303.15, and 313.15 K in a circulation-type equilibrium apparatus. The experimental data were well correlated with the Carnahan–Starling–De Santis (CSD) equation of state within ±1.0%. Azeotropic behavior has not been found in any of these mixtures.