PVDF/PMMA共混物非等温结晶动力学和晶体结构

通过差示扫描量热仪（DSC）、X射线衍射仪（XRD）对纯聚偏氟乙烯（PVDF）和PVDF/聚甲基丙烯酸甲酯（PMMA）共混物在不同降温速率下的非等温结晶行为和晶体结构进行表征和分析,并采用Jeziorny法和莫志深法研究了各组样品的非等温结晶动力学。结果表明,PMMA含量过多（PVDF/PMMA质量比为6/4和5/5）会完全抑制PVDF结晶;对于纯PVDF和可结晶的共混物（PVDF/PMMA质量比为9/1、8/2、7/3）样品,随着PMMA含量的增加,共混物结晶温度先升高后降低,结晶速率先少许增大后减小,说明少量PMMA起异相成核作用,可促进共混物结晶,而大量PMMA可明显阻碍分子重排,抑制其结晶;PMMA的加入可促进共混物晶体结构向低维转变;共混物晶体结构主要是α晶型,PMMA含量的增加不改变共混物的晶型,且使共混物结晶度先增大后减小。     

Carbon-coated Ni-Co alloy catalysts: preparation and performance for in-situ aqueous phase hydrodeoxygenation of methyl palmitate to hydrocarbons using methanol as the hydrogen donor

Carbon-coated Ni, Co and Ni-Co alloy catalysts were prepared by the carbonization of the metal doped resorcinol-formaldehyde resins synthesized by the one-pot extended Stöber method. It was found that the introduction of Co remarkably reduced the carbon microsphere size. The metallic Ni, Co, and Ni-Co alloy particles (mainly 10–12 nm) were uniformly distributed in carbon microspheres. A charge transfer from Ni to Co appeared in the Ni-Co alloy. Compared with those of metallic Ni and Co, the d-band center of the Ni-Co alloy shifted away from and toward the Fermi level, respectively. In the in-situ aqueous phase hydrodeoxygenation of methyl palmitate with methanol as the hydrogen donor at 330 °C, the decarbonylation/decarboxylation pathway dominated on all catalysts. The Ni-Co@C catalysts gave higher activity than the Ni@C and Co@C catalysts, and the yields of n-pentadecane and n-C₆–n-C₁₆ reached 71.6% and 92.6%, respectively. The excellent performance of Ni-Co@C is attributed to the electronic interactions between Ni and Co and the small carbon microspheres. Due to the confinement effect of carbon, the metal particles showed high resistance to sintering under harsh hydrothermal conditions. Catalyst deactivation is due to the carbonaceous deposition, and the regeneration with CO₂ recovered the catalyst reactivity.     

聚合物干粉对加气混凝土用抹灰砂浆性能的影响

针对加气混凝土普通抹灰砂浆存在的保水性差、粘结强度低、易开裂空鼓等缺陷,研究了聚合物干粉对加气混凝土用抹灰砂浆性能的影响,并对该影响机理进行了讨论.研究表明,在砂浆中同时掺入羟乙基甲基纤维素醚和聚乙烯-醋酸乙烯酯可再分散乳胶粉,大大改善了砂浆的保水性、提高了和易性和粘结强度,较好地解决了普通抹灰砂浆用于加气混凝土存在的开裂、空鼓甚至脱落等问题.     

天然产物基无铜自抛光防污涂料的制备与性能

随着人们环保意识的增强和环保法规的日益严格,不含重金属防污剂的环境友好防污涂料成为目前研究的热点。文中通过室内的接触角、水解失重和吸水率跟踪测试,研究了3种主链降解型聚丙烯酸锌树脂的表面润湿性能和自抛光性能;并将其与天然产物防污剂(Butenolide)复配制备了天然产物基无铜自抛光防污涂料,通过防污剂释放率测试和浅海浸泡试验对防污剂的释放行为和实海防污能力进行了研究。结果表明：主链降解型聚丙烯酸锌树脂H100Z具有优异的自抛光性能(质量损失可达8.4 mg·cm⁻²)和较低的溶胀程度(吸水率仅为12.3%),可作为Butenolide的载体,实现对其可控、稳定和持续的释放,该防污涂料在南海海域(深圳)和东海海域(厦门)浸泡3个月后均展现出优异的防污效果。     

Kiyoteru Tokuyasu: a pioneer of cryo‐ultramicrotomy

In July 2015 Professor K.T. Tokuyasu passed away in San Diego giving us the opportunity to reflect on the contribution this electron microscopist made to the field of immunocytochemistry. His work provided a sensitive, minimally invasive approach to producing thin sections of biological material for labeling with antibodies. His approach has been applied to a wide range of biological applications and provided important information on cellular processes.     

硅藻精土负载纳米零价铁降解甲基橙废水研究

纳米零价铁/硅藻精土复合材料是一种具有广阔实际应用前景的新型环保材料。以硅藻精土为载体,采用离心法预先吸附溶液中的Fe2+,然后采用液相还原法,制得一种纳米零价铁/硅藻精土环境功能复合材料,结果表明,制备的纳米零价铁/硅藻精土复合材料能够有效降解水中甲基橙;当负载量为5%、催化剂用量为1 g/L、p H值为3.0、甲基橙的质量浓度为20 mg/L、体积为40 m L时,10 min后甲基橙降解率可达90%以上,降解过程符合准二级反应动力学。     

铜基催化剂的制备及其在催化溴甲烷制二甲醚中的应用

采用浸渍法制备了不同载体和金属组分的系列负载型催化剂,考察对溴甲烷制二甲醚的催化活性,并采用XRD、TPR和BET进行表征。结果表明,铜基催化剂催化性能较好,且以Al2O3-1#为载体制备的催化剂催化性能更优。Cu O负载量较低时,具有较高的分散度;高温焙烧使催化剂的活性中心由分散态Cu O转变为晶相Cu O,导致Cu O利用率下降;添加助剂K可显著提高Cu O利用率。优选的催化剂制备条件为:以Al2O3-1#为载体,活性组分Cu O负载质量分数为5%,助剂K负载质量分数为0.8%,焙烧温度为350℃,此条件下制备的催化剂,CH3Br转化率和二甲醚选择性均为100%,催化剂的Cu O利用率达到88.04%;再生10次后,催化剂性能保持稳定,没有明显下降。     

Cu-K/Al_2O_3催化剂上溴甲烷合成二甲醚的失活动力学研究

采用Cu-K/Al2O3催化剂,在固定床积分反应器上进行溴甲烷合成二甲醚的动力学实验,反应温度(463.15~523.15)K条件下,得出主反应的宏观动力学方程:r=1.1+2.8×10-3T-4.4exp(-21.5/RT)pCH3Br,主反应的活化能约为21.5 k J·mol-1。对主反应宏观动力学方程进行统计检验,结果表明,在给定99%的置信度下,方程显著、可信。失活前后的XRD表征结果表明,催化剂晶相由Cu O转变为Cu Br2是导致催化剂失活的主要原因。采用独立失活机理描述催化剂失活速率方程,通过回归得到各项参数,建立了适用于Cu-K/Al2O3催化剂上溴甲烷合成二甲醚的失活动力学方程:r=[-1.1+2.8×10-3T-4.4exp(-21.5/RT)pCH3Br]×exp(-2.1×10-3t)。     

Microkinetic model for the pyrolysis of methyl esters: From model compound to industrial biodiesel

A tool for the generation of decomposition schemes of large molecules has been developed. These decomposition schemes contain radicals which can be eliminated from the model equations if both the μ‐hypothesis and the pseudosteady‐state approximation are valid. The reaction rate coefficients and thermodynamic parameters have been calculated by incorporating a comprehensive group additive framework. A microkinetic model for the pyrolysis of methyl esters with a carbon number of up to 19 has been generated using this tool. It is validated by comparing calculated and experimental yields of the pyrolysis of methyl decanoate and novel rapeseed methyl ester pyrolysis data in the temperature range from 800 to 1100 K and methyl ester partial pressure range from 1 × 10^?3 to 1 × 10^?2 MPa. This modeling frame work allows to not only assess the use of methyl ester mixtures as potential feedstock for olefin production but also their effect as blend‐in or trace impurity. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4309–4322, 2015     

酯类共聚单体对PAN结构及热稳定化行为的影响

采用K2S2O8-NaHSO3氧化还原引发剂和水相沉淀聚合法制备了丙烯腈均聚物(PAN)、丙烯腈-醋酸乙烯酯共聚物(P(AN-VAc))、丙烯腈-丙烯酸甲酯共聚物(P(AN-MA));采用红外光谱、核磁共振、差示扫描量热/热重同步分析仪、X射线衍射仪等手段对聚合物的结构及热稳定化行为进行了研究。结果表明:引入VAc,MA酯类共聚单体对PAN聚合物的立构规整性几乎没有影响,3种聚合物的等规、无规、间规比例均约为1∶2∶1,平均序列长度约为2,呈现典型的无规聚合物结构特征;在空气气氛热稳定化过程中,VAc,MA酯类共聚单体不能以离子形式在低温下引发环化反应,但是都可以起到缓和放热和减少失重的作用,从而提高热稳定化过程的可控性;在相同条件下进行热稳定化处理,P(AN-MA)具有较高的相对环化率和芳构化指数,表明MA更有利于提高热稳定化程度。