风化煤的化学降解

在Ｍｎ－Ｍｏ催化剂存在下用ＨＮＯ３氧化对风化煤进行了化学降解研究。考察一降解条件，氧化产物收率及组成性质，结果表明，与原煤相比，氧解产物中极性功能团大量增加，极性溶剂中抽提率显著提高。     

微丝解聚对DNA合成的影响

G_0期细胞在10％血清培养液刺激后向S期行进的早期出现微丝解聚的变化.细胞松弛素B(CB)0.5mg·L~_(-1)使微丝发生部分解聚能加强血清对DNA合成的刺激作用.但随着CB剂量的加大,微丝解聚的加强,便逐步增强对DNA合成的抑制作用.发现用5,10mg·L~(-1)的CB短时间处理G_0期细胞可强烈刺激蛋白激酶C(PKC)活性,虽使微丝暂时完全解聚,但不影响向S期的过渡及DNA的合成.促癌剂TPA(12-tetradecanoyl phorbol-13-acetate)可刺激G_0期细胞PKC活性,并能促进血清对DNA合成的刺激作用,但小剂量CB和TPA促进DNA的合成均依赖于血清的存在。     

The basic processes of depolymerization and its real kinetic analysis

The method of computer-experiments can be applied successfully on the radical depolymerization under inclusion of initiation, depropagation and termination. The comfortable PC-program TA-kin for the non-linear estimation of parameters for TG- or DSC-experiments was applied to the determination of activation parameters of depropagation and termination. Therefore the overall-evaluation of three or more data sets is a prerequisite. The determination of kinetic parameters runs satisfactory if the measured curves are strongly different, e.g. by varying the heating rate, including acceptable experimental errors. Several recommendations for laboratory experts are given. A great support for a very sufficient estimation is the inclusion of simultaneous analysis of the radical concentration.     

Poly(arylene sulfide)s via nucleophilic aromatic substitution reactions of halogenated pyromellitic diimides

Nucleophilic aromatic substitution (SNAr) reactions are exploited to prepare poly(arylene sulfide)s (PAS's) via the reaction of bis-thiolates and dibrominated pyromellitic diimide (PMDI) derivatives. Small-molecule model studies reveal the reaction is well-defined and proceeds in quantitative yield in practical times at room temperature. Variation in comonomer feed ratios allowed some control over target polymer molecular weights in the step polymerization, but control was likely limited by the relatively poor polymer solubility in the dipolar aprotic solvents typically employed to promote SNAr reactions. One substitution pattern produces a steric “pocket” around the PMDI units, inducing a peculiar solubility trend in halogenated solvents; that is, greatly reduced solubility in CHCl₃ relative to CH₂Cl₂ and C₂H₂Cl₄. One example small-molecule readily dissolves in CHCl₃ at room temperature, then rapidly grows poorly soluble crystals revealed by single-crystal XRD to contain CHCl₃ molecules in the steric pockets. Finally, the recently demonstrated depolymerization of phthalonitrile-based PAS's via ipso substitution with monothiolates as chain scission agents yields quantitative molecular weight reduction to monomeric species from the polymers reported here.     

Recent Trends in the Pyrolysis of Non-Degradable Waste Plastics

Waste plastics are non-degradable constituents that can stay in the environment for centuries. Their large land space consumption is unsafe to humans and animals. Concomitantly, the continuous engineering of plastics, which causes depletion of petroleum, poses another problem since they are petroleum-based materials. Therefore, energy recovering trough pyrolysis is an innovative and sustainable solution since it can be practiced without liberating toxic gases into the atmosphere. The most commonly used plastics, such as HDPE, LDPE (high- and low-density polyethylene), PP (polypropylene), PS (polystyrene), and, to some extent, PC (polycarbonate), PVC (polyvinyl chloride), and PET (polyethylene terephthalate), are used for fuel oil recovery through this process. The oils which are generated from the wastes showed caloric values almost comparable with conventional fuels. The main aim of the present review is to highlight and summarize the trends of thermal and catalytic pyrolysis of waste plastic into valuable fuel products through manipulating the operational parameters that influence the quality or quantity of the recovered results. The properties and product distribution of the pyrolytic fuels and the depolymerization reaction mechanisms of each plastic and their byproduct composition are also discussed.     

A simple HPLC-MS method for the quantitative determination of the composition of bacterial medium chain-length polyhydroxyalkanoates

Bacterial poly(hydroxyalkanoates) (PHAs) vary in the composition of their monomeric units. Besides saturated side-chains, unsaturated ones can also be found. The latter leads to unwanted by-products (THF ester, secondary alcohols) during acidic cleavage of the polymer backbone in the conventional analytical assays. To prevent these problems, we developed a new method for the reductive depolymerization of medium chain-length PHAs, leading to monomeric diols that can be separated and quantified by HPLC/MS. Reduction is performed at room temperature with lithium aluminum hydride within 5-15 min. The new method is faster and simpler than the previous ones and is quantitative. The results are consistent with the ones obtained by quantitative (1)H NMR.     

用液相色谱法分析聚对苯二甲酸丁二醇酯的解聚产物

采用超临界甲醇解聚的方法,将聚对苯二甲酸丁二醇酯（PBT）降解为对苯二甲酸二甲酯（DMT）和丁二醇两种单体。利用液相色谱法分析产物DMT,建立了较好的分析方法。其实验操作条件如下：色谱柱为DiamonsilC18,流动相为甲醇-水（3：1,y／y）,检测波长254nm。测定结果为DMT含量在0．005-0．25μg,线性关系良好。该方法具有高色谱分辨率、简单、准确、重复性好等特点。     

A Comparison of Phenolic Monomers Produced from Different Types of Lignin by Phosphotungstic Acid Catalysts

Herein we studied the chemical structure of different types of lignin samples and the potential to prepare phenolic monomers was illustrated by phosphotungstic acid catalysts. Different types of H/G/S lignin components had different structures. The lignin extracted from poplar had the highest molecular weight and β-O-4 aryl ether contents, followed by pine and straw lignin samples. After depolymerization by PTA catalyst, the yields of phenolic monomers detected was 8.06 wt % (poplar), 5.44 wt % (pine) and 4.52 wt % (straw), respectively. Further, the ratios of H/G/S in the phenol monomers were also different, indicating that the S, G and H types structural units were continuously transformed with each other during the reaction. In our study, the change in the types of lignin samples resulted into an improvement of the distribution of phenolic products, and also the selectivity of phenolic monomers significantly.     

超高效聚合物色谱法测定酚化解聚木质素的相对分子质量

超高效聚合物色谱法(APC)是一种新开发的高分辨聚合物表征技术,能在10 min内完成聚合物的高效分辨分离,同时获得聚合物的平均相对分子质量及其分布参数。实验以水溶性热酚化解聚木质素为研究对象,探索了APC测试水性体系高分子相对分子质量及其分布参数的条件。在以弱碱性磷酸盐缓冲液为流动相,采用Waters水溶性ACQUITY APC AQ 450 Å、200 Å、45 Å 3根色谱柱串联,进样量为10 μL,流速为0.5 mL/min的条件下,获得了复杂水相体系木质素磺酸盐解聚产物的平均相对分子质量及其分布参数,且相对标准偏差(RSD)低于1%。结果表明,与传统的凝胶渗透色谱相比,APC方法具有分辨率高、重现性强的优点。本实验为高性能天然高分子的高效分离、结构分析提供了新的方法和途径,同时为木质素的解聚和液化产物调控机理的研究提供了可行的方法。