沸石催化剂在甲苯甲基化中的择形催化形用

综述了影响甲苯甲基化择形催化的因素,讨论了沸石的内外表面酸中心及酸强度、沸石的孔道、反应物和产物的吸附等因素对提高对二甲苯选择性的影响。     

新法合成对甲苯氧乙基甲醚和苯氧乙基甲醚

酚与氯乙醇反应，再用硫酸二甲酯甲基化合成了对甲苯氧乙基甲醚和苯氧乙基甲醚。考察了原料配比、反应温度和反应时间对产物收率的影响，找到了最佳反应条件。并对ＺＰＢＢＣ催化乙二醇单酚醚甲基化反应进行了讨论。     

High-sensitivity determination of graft ratio of maleic anhydride-grafted polyolefin by anhydride methylation in supercritical methanol followed by H NMR spectroscopy

A wide range of graft ratios in Maleic anhydride (MA)-grafted polyolefin (PO), MA-g-PO, was determined by the combination of the methylation of grafted MA in supercritical methanol with quantification by ¹H NMR spectroscopy. The combination enabled the determination of a graft ratio as low as 0.01 wt% (100 ppm) in MA-g-PO.     

Comparison of two different methods for the separation of lipid classes and fatty acid methylation in reindeer and fish muscle

In the present study different methods for the separation of lipid classes and methylation were compared and evaluated for method optimisation in muscle tissue. Fish and reindeer muscle were tested as fish represents a high proportion of polyunsaturated FA (PUFA) and reindeer a moderate amount of PUFA. Lipids were separated either by solid phase extraction (SPE) into neutral (NL) and polar lipids (PL) or by thin layer chromatography into triacylglycerols (TAG) and phospholipids. All fractions were methylated with or without boron trifluoride (BF₃). The two different separation methods showed differences between PL and phospholipids, while TAG and NL were largely similar. Methylation method did not lead to important differences when comparing within the different separation methods, though methylation with BF₃ generally resulted in similar or higher values of methylated FA, indicating a more complete methylation. The content of PUFA in the muscle tissue did not affect these outcomes. Separation of lipids by SPE, followed by methylation with BF₃ was judged to be the best overall method, though not suitable for analysis of samples with labile fatty acids.     

Lab-Scale Microreactor Plant for the Study of Methylations with Liquid Chloromethane

Chloromethane is an important reagent for methylations in the process industry. However, as a gas suspected of causing cancer, it is rarely used at laboratory scale. Therefore, a setup is presented here for studies in a laboratory under safe and reproducible conditions. The use of a microreactor guarantees high heat transfer rates and a low holdup of the reagent. As a proof-of-concept, the reaction of chloromethane with the secondary amine morpholine in aqueous solution is investigated. By applying elevated pressures, a liquid-liquid system with enhanced solubility of chloromethane in the aqueous phase is accessible.     

Catalytic performance of Cu- and Zr-modified beta zeolite catalysts in the methylation of 2-methylnaphthalene

2,6-Dimethylnaphthalene(2,6-DMN) is a commercially important chemical for the production of polyethylenenaphthalate and polybutylene naphthalate. However, its complex synthesis procedure and high production cost significantly reduce the use of 2,6-DMN. In this study, the synthesis of 2,6-DMN was investigated with methylation of 2-methylnaphthalene(2-MN) over metal-loaded beta zeolite catalysts including beta zeolite, Cu-impregnated beta zeolite and Zr-impregnated beta zeolite. The experiments were performed in a fixed-bed reactor at atmospheric pressure under a nitrogen atmosphere. The reactor was operated at a temperature range of 400–500 °C and varying weight hourly space velocity between 1 and 3 h~(-1).The results demonstrated that 2,6-DMN can be synthesized by methylation of 2-MN over beta type zeolite catalysts.Besides 2,6-DMN, the product stream also contained other DMN isomers such as 2,7-DMN, 1,3-DMN, 1,2-DMN and 2,3-DMN. The activity and selectivity of beta zeolite catalyst were remarkably enhanced by Zr impregnation, whereas Cu modification of beta zeolite catalyst had an insignificant effect on its selectivity. The highest conversion of 2-MN reached81%, the highest ratio of 2,6-DMN/2,7-DMN reached 2.6 and the highest selectivity of 2,6-DMN was found to be 20% by using Zr-modified beta zeolite catalyst.     

壳聚糖三甲基季铵盐的合成及其结构表征

利用壳聚糖分子中氨基的特性,与过量碘甲烷进行彻底甲基化反应合成水溶性的壳聚糖三甲基季铵盐,纯化后进行了结构表征。     

环戊二烯催化甲基化制备甲基环戊二烯催化剂筛选及制备条件的研究

从反应系统的特点考虑,选定了几种具有不同酸碱特性的金属氧化物进行复配处理,在一定条件下进行相应的催化活性试验,并利用正交试验,确定了制备催化剂的最佳工艺条件。结果表明：以９５％及无水乙醇混合制备的Ａｌ２Ｏ３ＭｇＯＫ２ＣＯ３三组分催化剂具有适合的酸、碱中心,是环戊二烯与甲醇催化甲基化合适的催化剂。这种催化剂制备最佳工艺条件为：摩尔比３∶２∶１,焙烧温度７００℃,焙烧时间６ｈ。     

Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and s...     

Hydralazine逆转胃癌细胞株p16基因甲基化及增强其表达的研究

目的: 通过使用甲基转移酶抑制剂肼屈嗪(Hydralazine)作用于胃癌细胞株BGC-823,观察Hydralazine对MTS1/p16基因启动子区CpG岛甲基化、p16 mRNA、p16蛋白表达及细胞增殖的影响;分析p16基因启动子区CpG岛甲基化与p16基因表达两者间的关系,以此考察胃癌细胞株BGC-823 p16基因的失活机制是否与启动子区CpG岛甲基化有关。方法: 对体外培养的胃癌细胞株BGC-823进行分组实验,实验组加入水溶性的Hydralazine,浓度0、10、30、100 μmol/L,对照组不加Hydralazine,96 h 后对两组分别行甲基化特异性PCR法(MSP)、RT-PCR及Western blot检测,以观察p16基因甲基化状态、mRNA、蛋白表达的变化;应用6种不同浓度的水溶性Hydralazine(0、3、10、30、100、300 μmol/L)处理胃癌细胞BGC-823,72 h 后行MTT检测,以观察对细胞增殖的影响。结果: P16基因在胃癌细胞株BGC-823中,启动子区CpG岛呈高甲基化状态,mRNA及蛋白呈低水平表达。Hydralazine阻断甲基转移酶作用后,p16基因启动子区CpG岛呈去甲基化状态,Hydralazine浓度越高,CpG岛去甲基化越明显。Hydralazine阻断甲基转移酶作用后,用药后p16 mRNA表达较前明显增强(P<0.05)。Hydralazine阻断甲基转移酶作用后,用药后p16蛋白表达较前明显增强(P<0.01)。MTT检测到不同浓度的Hydralazine(0、3、10、30、100、300 μmol/L)对细胞增殖的抑制率差异有统计学意义(P<0.05),其量效关系反映出抑癌基因p16去甲基化程度越高,对胃癌细胞株BGC-823的增殖抑制越显著。结论: P16基因动子区CpG岛甲基化是p16基因失活的重要机制。