神华煤直接液化残渣超临界溶剂萃取研究

利用甲苯、苯和乙醇三种溶剂在反应釜中对神华煤直接液化残渣进行了超临界溶剂萃取,考察了压力、温度、萃取时间、溶剂/残渣比等对萃取产物收率和重质液体萃取组成的影响。结果表明,以甲苯为溶剂进行萃取时,萃取时间对重质液体产率及HS和A收率的影响不大,而温度、压力以及溶剂/残渣质量比都会影响萃取产物的产率及组成。溶剂超临界萃取过程中,有其他组分向HS组分转化,提高了HS的收率。三种溶剂中,苯显示了和甲苯相似的萃取性能,而乙醇的萃取性能相比苯和甲苯则较差,但乙醇萃取得到的重质液体中轻质组分含量高于苯和甲苯。萃取过程中,残渣中的灰分和硫分主要富集至萃取残渣中。     

超临界CO_2诱导相转化法制备聚苯乙烯膜及膜体系的相图计算

以甲苯为溶剂,利用超临界CO_2诱导相转化法制备了多孔非对称聚苯乙烯膜.通过扫描电镜对膜结构进行了表征,探讨了不同温度、压力和铸膜液中聚苯乙烯浓度对膜形态、孔径分布及膜孔隙率的影响;同时,基于Tompa扩展的Flory-Huggins聚合物溶液理论计算了聚苯乙烯/超临界CO_2/甲苯铸膜体系的三元相图.研究表明,在温度为35~65℃、压力为8~16 MPa及聚合物质量分数为15%~35%条件下,制备的聚苯乙烯膜截面呈胞腔状孔结构,孔隙率为53.54%~84.67%,且孔隙率随温度、压力和聚苯乙烯浓度均呈现出先增大后减小的趋势.相图计算结果表明,温度对体系双节线位置的改变影响较小,而压力对其影响相对较大.     

废轮胎和天然橡胶在超临界甲苯中的解聚研究

在300 ℃～360 ℃、3.7 Mpa～7.0 Mpa、反应20 min～90 min、投料比(甲苯与废轮胎或天然橡胶的质量比)5.0～10.0下,分别研究了废轮胎和天然橡胶在超临界甲苯中的解聚,着重考察了解聚率与反应条件的关系、以及解聚产物分布.在临界点附近,解聚率随温度、压力升高而增加;高于临界压力后,压力对解聚率的影响减弱.解聚产物主要为液相物和固相物,液相产物用色质联谱(GC/MS)分析表明,以芳香烃和烯烃类为主,且分子量大多小于300;固相产物经分析以碳黑为主.废轮胎和天然橡胶的解聚产物大部分是相似的,天然橡胶可以完全解聚,在同样条件下废轮胎解聚率低于天然橡胶.超临界甲苯在反应中对实验样品不仅起到溶胀和溶解作用,同时也参与了解聚反应.研究结果为选择解聚介质和操作参数提供了依据.     

苯、甲苯、联苯在水-叔丁醇混合溶剂中的溶解度和疏水作用

在283.15,288.15,293.15,298.15 K温度下,测定了苯、甲苯、联苯在水-叔丁醇混合溶剂中的溶解度,其中混合溶剂中叔丁醇的物质的量分数分别为0.000,0.010,0.020,0.030,0.040,0.045,0.050,0.060,0.080,0.100. 以此为基础计算了苯、甲苯、联苯在不同温度和溶剂组成条件下的标准溶解Gibbs自由能和相关过程的疏水相互作用Gibbs自由能,并从微观上讨论了溶剂结构对溶解度和疏水作用的影响.     

以水、甲苯及其混合溶剂超临界萃取煤的研究

在半连续萃取装置上,以水、甲苯及其混合物为溶剂对黄县褐煤进行了非等温超临界萃取,考察了不同溶剂对萃取过程的影响。结果表明,以甲苯为溶剂的萃取率高于以水为溶剂的。以水为溶剂萃取物中的沥青烯和预沥青烯的H/C原子比高于以甲苯为溶剂的,而O/C原子比则低。在水中加入适量甲苯,能够明显改善萃取效果,大幅度提高萃取率。     

TiO2光催化降解苯和甲苯的动力学研究

利用溶胶-凝胶法制备了粒径约为13nm、晶型为锐钛矿相和金红石相混晶的TiO2光催化剂,并利用此催化剂对挥发性有机污染物苯和甲苯进行了光催化降解研究,对不同的催化剂用量、光源、污染物的初始浓度以及氧气对光催化反应速率的影响进行了研究。结果表明,光催化降解甲苯和苯的反应均符合假一级动力学方程,光强与光催化降解甲苯的反应的速率常数之间呈指数关系,光波长对光催化降解苯的影响也很显著;随着甲苯和苯初始浓度的增加,光催化反应速率常数降低;氧气加快了光催化降解甲苯和苯的速率;对于光催化降解初始浓度为37.6μmol/L的甲苯而言,催化剂的最佳使用量为0.30g,对于光催化降解初始浓度为9.0μmol/L的苯来说,催化剂的最佳用量为0.10g。     

醇在钒基催化剂上的氧化

以过氧化叔丁醇作为氧化剂,研究了醇类(苯甲醇、1-苯基乙醇和环己醇)在钒基催化剂上的氧化反应.制备了含苯磷二酚配体或吡嗪-2-羧酸酯配体的钒配合物,并运用傅里叶变换红外光谱、核磁共振谱、紫外-可见光谱及元素分析对其进行了表征.考察了溶剂对该类反应的影响.发现在甲苯溶剂中进行氧化反应时,苯甲醇被氧化成苯甲醛而不会被深度氧化为苯甲酸;而在乙腈溶剂中,苯甲醛和苯甲酸均有生成.此外,对不同钒磷氧化物的催化活性进行了比较,结果表明,在乙腈溶剂中的产品收率比在甲苯溶剂中高.     

采用相转移催化法制备苯二甲酰亚胺基甲基聚苯乙烯

以邻苯二甲酰亚胺钾盐为亲核取代试剂, 采用相转移催化体系通过Gabriel反应, 将氯甲基聚苯乙烯转变为苯二甲酰亚胺基甲基聚苯乙烯, 考察了各种因素对相转移催化反应的影响规律, 探讨了相转移催化机理. 结果表明, 采用相转移催化体系, 相转移催化剂将邻苯二甲酰亚胺负离子从水相中转移至油相, 与氯甲基聚苯乙烯发生亲核取代, 顺利地将氯甲基聚苯乙烯大分子链上的氯甲基转变成了甲基化的苯二甲酰亚胺基, 成功地实现了高分子的功能化转变. 影响相转移催化反应的主要因素有催化剂种类与用量、溶剂的极性、油相与水相比例及温度等. 当以十六烷基三甲基溴化铵为催化剂且以甲苯为有机相时, 反应效果最佳, 反应温度为50 ℃时, 反应8 h氯甲基的转化率可达到87%.     

溶解沉淀-气相色谱-质谱法测定食品接触用聚苯乙烯塑料中10种有机物

建立食品接触用聚苯乙烯塑料中10种有机物(苯、丙烯腈、甲苯、乙苯、对-二甲苯、间-二甲苯、异丙苯、邻-二甲苯、丙苯和苯乙烯)含量的溶解沉淀气相色谱–质谱检测方法。分别讨论了定量方式、溶解溶剂以及溶解溶剂与沉淀剂甲醇的体积比对10种有机物回收率的影响。样品用N,N-二甲基甲酰胺(DMF)超声溶解,甲醇沉淀,内标法定量可获得良好的定量结果。检测10种有机物的线性范围在0.2～100μg/mL内,相关系数均大于0.999,方法检出限为1.0～2.0 mg/kg,定量限为2.0～4.0 mg/kg;加标平均回收率为81.5%～101.9%,测定结果的相对标准偏差为0.9%～4.7%(n=6)。该方法快速、准确,适用于食品接触用聚苯乙烯塑料中10种有机物含量的检测。     

用渗流理论计算高分子溶液中溶剂的自扩散系数

基于微观渗流理论建立了溶剂小分子在高分子溶液中的自扩散模型,并据此模型对不同温度和浓度下的聚苯乙烯(PS)-苯、PS-甲苯、PS-乙苯和PS-四氢呋喃4个体系中小分子的自扩散系数进行了关联,计算出在不同温度下溶剂分子扩散所需的临界浓度。结果表明,在PS玻璃化温度以下,本模型对于温度和浓度具有很好的适用性和关联精度。     

Characterization of thermal diffusion in polymer solutions by thermal field-flow fractionation: Dependence on polymer and solvent parameters

The thermal diffusion coefficient D_T has been obtained for 17 polymer-solvent combinations, each of them spanning a range of polymer molecular weights, using thermal field-flow fractionation. The polymers examined include polystyrene, poly(alpha-methyl)styrene, polymethylmethacrylate, and polysioprene. The solvents include benzene, toluene, ethylbenzene, tetrahydrofuran, methylethylketone, ethylacetate, and cyclohexane. Although D_T was confirmed as essentially independent of polymer molecular weight, it was found to vary substantially with the chemical composition of polymer and solvent. The results were used to evaluate several thermal diffusion theories; the agreement with theory was generally found to be unsatisfactory. Attempts were then made to correlate the measured thermal diffusion coefficients with various physicochemical parameters of the polymers and solvent. A good correlation was found in which D_T increases with the thermal conductivity difference of the polymer and solvent and varies inversely with the activation energy of viscous flow of the solvent.     

Degradation of polycaprolactone in supercritical fluids

The degradation of polycaprolactone (PCL) was studied in subcritical and supercritical toluene from 250 to 375 °C at 50 bar. The degradation was also investigated in various solvents like ethylbenzene, o-xylene and benzene at 325 °C and 50 bar. The effect of pressure on degradation was also evaluated at 325 °C at various pressures (35, 50 and 80 bar). The variation of molecular weight with time was analyzed using gel permeation chromatography and modeled using continuous distribution kinetics to evaluate the degradation rate coefficients. PCL degrades by random chain scission in subcritical conditions (250-300 °C) and by chain end scission (325-375 °C) in supercritical conditions in toluene. The degradation of PCL in other solvents at 325 °C was by chain end scission under both subcritical and supercritical conditions indicating that the mode of scission depends on the temperature and not on the supercriticality of the solvent. The thermogravimetric analysis of PCL was investigated at various heating rates (2-24 °C/min) and the activation energy was determined using Friedman, Ozawa and Kissinger methods. It was shown that PCL degrades by random scission at lower temperatures and by chain end scission at higher temperatures again indicating that the mode of scission is dependent on the temperature.     

Thermal degradation of copolymers of styrene and acrylonitrile. II. Reaction products

Hydrogen cyanide is a minor product of degradation of copolymers of styrene and acrylonitrile. The liquid products have been separated and identified by combined gas chromatography and mass spectrometry (GC-MS), as styrene, acrylonitrile, toluene, and benzene. The ratio of styrene to acrylonitrile monomers in the products is approximately twice that of the monomer units in the copolymers, and the ratios of styrene to toluene and benzene are the same as are obtained from pure polystyrene. These ratios were determined by using infrared spectral methods. The fraction of products volatile at the temperature of degradation but involatile at ambient temperature was also analyzed by using GC-MS. A series of four dimers and four trimers were fairly reliably identified. The residual material from copolymers containing up to 33.4% acrylonitrile is always soluble in toluene. The 50/50 copolymer and its residues are insoluble in toluene. Yellow coloration develops in the residues from high acrylonitrile copolymers at advanced stages of degradation. Infrared and ultraviolet spectra suggest that this is due to conjugated unsaturation in the polymer chain backbone which may be associated with the liberation of hydrogen cyanide from the acrylonitrile units.     

Effect of solvents on electro-spinnability of polystyrene solutions and morphological appearance of resulting electrospun polystyrene fibers

The effects of solvents and their properties on electro-spinnability of the as-prepared polystyrene (PS) solutions and the morphological appearance of the as-spun PS fibers were investigated qualitatively by means of a scanning electron microscope (SEM). The eighteen solvents used were benzene, t-butylacetate, carbontetrachloride, chlorobenzene, chloroform, cyclohexane, decahydronaphthalene (decalin), 1,2-dichloroethane, dimethylformamide (DMF), 1,4-dioxane, ethylacetate, ethylbenzene, hexane, methylethylketone (MEK), nitrobenzene, tetrahydrofuran (THF), 1,2,3,4-tetrahydronaphthalene (tetralin), and toluene. The PS solutions in 1,2-dichloroethane, DMF, ethylacetate, MEK, and THF could produce fibers with high enough productivity, while the PS solutions in benzene, cyclohexane, decalin, ethylbenzene, nitrobenzene, and tetralin were not spinnable. Qualitative observation of the results obtained suggested that the important factors determining the electro-spinnability of the as-prepared PS solutions are high enough values of both the dipole moment of the solvent and the conductivity of both the solvent and the resulting solutions, high enough boiling point of the solvent, not-so-high values of both the viscosity and the surface tension of the resulting solutions.     

聚苯乙烯热降解机理的理论研究

采用密度泛函理论B3LYP/6-311G（d）方法,对聚苯乙烯（PS）热降解反应机理进行了研究。PS热降解的主要产物是苯乙烯,其次是甲苯、α-甲基苯乙烯、乙苯和二聚体等芳烃化合物。PS热降解反应主要包括主链C-C键均裂、β-断裂、氢转移和自由基终止等反应。针对以上各类反应进行了路径设计和理论计算分析,对参与反应的分子的几何结构进行了优化和频率计算,获得了各热降解路径的标准动力学和热力学参数。计算结果表明,苯乙烯主要由自由基的链端β-断裂反应形成;二聚体主要由分子内1,3氢转移的反应形成;α-甲基苯乙烯由分子内的1,2氢转移后进行β-断裂形成;甲苯由苯甲基自由基夺取主链上的氢原子形成;乙苯由苯乙基自由基夺取氢原子形成。动力学分析表明,苯乙烯形成所需要的能垒低于其他产物形成所需要的能垒,故苯乙烯为主要的热降解产物;这与相关实验结果基本一致。     

Studies on the Mechanism of the Direct Synthesis of Styrene form Benzene and Ethylene

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基于Hansen溶度参数的煤直接液化残渣超临界萃取

以丙酮、 异丙醇和苯为溶剂在超临界状态下对煤直接液化残渣进行萃取, 应用溶度参数分析了超临界萃取环境中溶剂和萃取原料的变化; 基于Hansen拓展方法建立了关联Hansen溶度参数和萃取收率的理论方程. 结果表明, 临界温度较高. 以色散力溶度参数为主的苯的萃取收率明显高于其它2种溶剂; 液化残渣中可萃出组分的理想溶解度随温度的升高而增大, 该效应也是超临界溶剂萃取重质组分时萃取收率提高的重要原因; 萃取收率与Hansen溶度参数之间的回归模型与实验结果具有较好的一致性, 证明Hansen溶度参数理论和Hansen拓展方法适用于描述煤直接液化残渣的超临界萃取过程.     

气相色谱法测定苯、甲苯在聚苯乙烯溶液中无限稀时的活度

<正> 气相色谱法测定二元溶液中挥发性组分在无限稀时的活度已是一个广泛应用的成熟的方法。1969年,Smidsrφd和Guillet首先将此法用于聚合物溶液,并指出柱温必须高于聚合物的玻璃转化温度。对此,我们选择了聚苯乙烯以及其结构基本相同的挥发性组分苯和甲苯,在76—180℃范围内进行了考察。     

气液色谱法研究聚合物/溶剂体系气液平衡

 用气液色谱法测定了聚二甲基硅氧烷（PDMS）／溶剂、聚甲基丙烯酸甲酯（PMMA）／溶剂体系在不同温度下以质量分数表示的无限稀溶剂活度系数和Flory－Huggins相互作用参数。应用UNIFAC和UNIFAC－FV模型对PDMS／溶剂、PMMA／溶剂体系中以质量分数表示的无限稀溶剂活度系数进行了估算。结果表明,用这两个模型预测PDMS／溶剂、PMMA／溶剂体系中的无限稀溶剂活度系数有待修正或采用其它模型进行估算。