多元醇缩醛类PP成核剂的应用研究进展

综述了包括山梨醇和木糖醇在内的多元醇缩醛类聚丙烯(PP)成核剂的应用研究进展,比较了三代山梨醇缩醛类成核剂DBS、MDBS和DMSBS在PP中的应用性能,DBS熔点低,对PP增透效果差,使用过程中醛味大;MDBS对PP增透效果好,但使用过程中仍然会产生醛味;DMDBS熔点高,增透效果好,使用中无异味,但加工温度高;以混合醛合成的非对称成核剂PP增透效果好,成本低,使用过程不产生异味;不同代成核剂的物理复配有利于降低成本,提高应用效果;该类成核剂也可用于聚乙烯及其他聚合物的成核改性。对该类成核剂的改进集中在两方面,一方面是对成核剂本身进行改性,如山梨醇与混合醛缩合直接合成具有不对称结构的缩醛,或者将不同品种的缩醛进行物理共混、或者与其他类成核剂进行物理混合,再或者与其他助剂进行复合,目的都是为了发挥不同成分的协同效应,提高成核剂的综合性能;另一方面是对成核剂的加入方式如釜内与釜外,成核剂的分散方式如母粒形式、配成液体形式和成核剂与PP的加工工艺进行研究。在可预见的将来,还没有更好的成核剂可以取代山梨醇成核剂。     

聚乙烯成核剂研究及应用进展

综述了聚乙烯有机成核剂、无机成核剂及无机／有机复合成核剂的研究及在LLDPE或HDPE中的应用进展。其中有机成核剂包括山梨醇缩醛类－DBS、MDBS和DMDBS）、山梨醇、对羟基苯甲酸、聚4－甲氧基－4’－丙烯酰氧苯甲酸苯酯（PMAPAB）液晶、硬脂酸盐（Kst、CaSt2及ZnSt2）和Hyperform HPN－20;无机成核剂为滑石粉。     

山梨醇缩醛类成核剂生产中的废水回用技术

在介绍山梨醇缩醛成核剂合成原理和生产工艺的基础上,重点介绍了该类成核剂生产过程中废水的来源。研究表明,利用常规的絮凝剂及Feton试剂氧化法均无法使废水达到排放标准。在不考虑投资大、施工周期长的生化处理技术的前提下,进行了废水回用试验。小试和工业试验结果表明废水回用不会对产品熔点和白度造成影响。直接将废水回收再利用,每生产1t成核剂,可减少外排污水7t。     

单环羧酸盐聚合物成核剂研究及应用进展

单环羧酸盐属于分散型聚合物成核剂。介绍了以苯甲酸钠、苯甲酸铝和六氢化邻苯二甲酸盐为代表的单环羧酸盐成核剂的合成方法、主要物性及其在聚合物中的应用。苯甲酸钠是最早使用的成核剂之一,具有制备工艺简单、价格便宜、应用广泛的优点;苯甲酸铝是目前仍在使用的增刚成核剂,具有制备工艺较为简单、价格适中的优点;而六氢化邻苯二甲酸盐是目前为止应用性能最好的单环羧酸盐成核剂,具有聚合物结晶温度高、结晶时间短和吸水性差等优点,其不足之处在于合成工艺较为复杂,且价格昂贵。欲提高单环羧酸盐成核剂的使用性能并降低价格,一是要降低HHPA盐的粒度,提高其在聚合物中的分散度和成核效果;二是与同类型的成核剂进行复配;三是与其他类型的成核剂或助剂如抗氧剂复合使用,发挥不同助剂之间的协同效应。     

取代芳基膦酸盐类聚丙烯成核剂合成及应用进展

取代芳基膦酸盐是最重要的聚丙烯成核剂之一。介绍了该类成核剂的发展历程及合成研究进展;以NA-11的合成为例,讨论了取代芳基膦酸盐的合成原理;分析了金属离子对成核剂性能的影响;全面评述了该类成核剂在PP中的应用研究现状,指出与其他助剂的复合化及超细化是该类成核剂应用研究开发的方向;阐述了成核剂在聚合物中的成核机理及成核效果。     

纤维素制备异山梨醇研究进展

异山梨醇可由资源丰富的纤维素直接转化制得,是一种重要的精细化学品,对未来化石能源产品的替代具有重要意义.本文从纤维素转化制备异山梨醇的反应路径、工艺方法、催化剂体系及催化性能影响因素几个方面进行综述,简述纤维素制异山梨醇工艺方法中多步反应与一步反应工艺的区别,论述反应所用二元催化剂及双功能催化剂的特性,分析催化剂酸量、...     

成核剂对CaCl2·6H2O相变材料储热性能的影响

用步冷曲线法和TGA-DSC联用研究了室温冷却开放体系和冰水浴冷却封闭体系两种工况下硼砂、SrCl2·6H2O、Ba(OH)2·8H2O等7种成核剂-CaCl2·6H2O复合体系的储热性能,探讨了工业级CaCl2·6H2O原料中主要杂质NaCl和MgCl2对成核剂成核作用的影响。研究结果表明:两种工况下,锶盐比其他成核剂的成核效果好,可使体系过冷度降低至3-4℃,但其热循环性能不稳定;钡盐为成核剂的复合储热体系循环性能明显优于其他体系,但其过冷现象严重。工业级CaCl2·6H2O中的主要杂质NaCA、MgCl2对PCM存在屏蔽成核效应,使体系储热性能恶化。     

季铵盐聚丙烯酰胺接枝阳离子絮凝剂的研制

本文阐述了季铵盐聚丙烯酰胶接枝阳离子絮凝剂的合成工艺路线和反应过程，较详细地说明了引发剂浓度、ｐＨ值、投料比、反应温度、反应时间等对接枝共聚、叔胺化、季铵化反应的影响，确定了适宜的工艺条件。     

Pt/HZSM-5水相重整山梨醇合成生物汽油的研究

考察了Pt/HZSM-5载体的酸性(硅铝比)、反应温度、反应压力、反应时间等因素对水相重整山梨醇合成生物汽油反应的影响。结果表明:在载体的硅铝比为38、反应温度260℃、压力5.0MPa、反应时间8h的条件下,该反应的总转化率高达95%,烷烃产物中C_(5+)的选择性接近90%,其中异构烷烃的选择性大于50%。     

二氧化碳为原料合成碳酸二甲酯研究进展

以二氧化碳为原料合成碳酸二甲酯(DMC)不仅可以实现二氧化碳的资源化利用,而且对碳减排具有重要意义。酯交换法是目前国内外生产DMC的主要方法,近年来DMC的合成研究主要集中在二氧化碳与甲醇直接合成及尿素醇解法两个方向。酯交换法、尿素醇解法是以二氧化碳与CH_3OH为原料间接合成DMC,以二氧化碳和CH_3OH为原料直接合成DMC属于典型的绿色化学反应,目前仍处于实验室研究阶段。研究有效活化二氧化碳及CH_3OH的催化剂及耦合反应,提高DMC的产率和选择性,是开发以二氧化碳和甲醇为原料制备DMC技术的关键。目前关于甲醇与二氧化碳合成DMC的催化机理基本可以归纳为两类:直接活化二氧化碳的反应机理和先活化甲醇再活化二氧化碳的反应机理。已报道的催化剂主要有有机金属催化剂、碱催化剂、金属氧化物催化剂、负载金属催化剂、醋酸盐催化剂、杂多酸催化剂、光助催化剂。以季铵盐和叔胺为协同催化剂,以PO为耦合剂,采用连续反应工艺,从而实现甲醇的高转化率和DMC的高收率,或许是直接合成DMC工艺实现突破的有效途径。在电场作用下,可以很好地活化二氧化碳。加大电催化研究力度,尽快构建电催化中试装置,或许可以为电化学催化直接合成DMC带来发展机遇。     

Novel gelatinous shape-stabilized phase change materials with high heat storage density

A series of polyol acetal derivatives were synthesized through condensation reactions of aromatic aldehyde with polyols, including sorbitol, mannitol, xylitol, and pentaerythritol. They were examined as gelators in the formation of paraffin-based shape-stabilized phase change materials (PCMs), in which 1,3:2,4-di-(4-methyl) benzylidene sorbitol (MDBS) exhibited excellent thermal stability. Three-dimensional netted structural phase change materials were obtained by paraffin doped with different gelators, which were thermally stable so that no leakage of paraffin occurs even under higher temperature than the melting point of paraffin. It was found that PCMs doped with 3 wt% expanded and exfoliated graphite (EG) exhibited better thermal conductivity, similar phase change temperature and heat storage density.     

Glycerol acetals, kinetic study of the reaction between glycerol and formaldehyde

The acetalization reaction between glycerol and formaldehyde using Amberlyst 47 acidic ion exchange resin was studied. These acetals can be obtained from renewable sources (bioalcohols and bioalcohol derived aldehydes) and seem to be good candidates for different applications such as oxygenated diesel additives. A preliminary kinetic study was performed in a batch stirred tank reactor studying the influence of different process parameters like temperature, feed composition and the stirring speed. A pseudo homogenous kinetic model able to explain the reaction mechanism was adjusted. Thus, the corresponding order of reaction was determined. Amberlyst 47 acidic ion exchange resin showed a fairly good behavior allowing 100% of selectivity towards acetals formation. However, the studied acetalization reaction showed high thermodynamic limitations achieving glycerol conversions around 50% using a stoichiometric feed ratio at 353 K. The product is a mixture of two isomers (1,3-Dioxan-5-ol and 1,3-dioxolane-4-methanol) and the conversion of 1,3-dioxolane-4-methanol into 1,3-Dioxan-5-ol was also observed.     

Pd[P(C_6H_5)_3]_4均相催化精制生物油的试验研究

采用四三苯基瞵合钯为催化剂,对均相催化精制生物油进行试验研究,探讨了反应条件的影响和精制前后各组分的变化及其变化机理.实验表明:反应温度130～140℃、反应时间12h、反应压力5MPa、催化剂与生物油的比值0.002为较佳反应条件;经过此条件精制后,酸、醛和碳碳双键含量(%面积)分别比原始生物油减少90%、88%和48%,酯含量(%面积)增加86%,酮、苯酚、聚糖和呋喃含量几乎不变.     

Hydrogen production by aqueous-phase reforming of glycerol over Ni-B catalysts

A Ni-B amorphous alloy catalyst (AP Ni) was prepared and used in an aqueous-phase reforming (APR) of glycerol. Higher stability and higher selectivity towards H₂ were obtained when compared with Raney Ni. After 130 h’ on stream aqueous-phase reforming of glycerol, the amorphous Ni-B catalyst was transformed to hexagonal closed-packed (hcp) Ni crystallites. The high selectivity towards hydrogen and catalytic stability may be due to the formation of hcp Ni crystallites during reaction and the protection of B₂O₃. The AP Ni catalyst was found to be 35-50% more active in terms of the H₂ production rate and 17-31% more selective toward H₂ as compared to Raney Ni. The reforming reaction at different reaction temperature, feedstock concentration, feedstock flow rate and other biomass derivatives i.e., ethylene glycol and sorbitol, were also investigated over AP Ni catalyst.     

Hydrogen production from sucrose via aqueous-phase reforming

Commercial sucrose was used to produce hydrogen in a combined approach of hydrogenation and aqueous phase reforming (APR). First a mixture of technical sorbitol/mannitol was produced by hydrogenating an aqueous solution of sucrose in a trickle bed reactor over 5 wt % Ru/C. The produced polyols were treated in a continuous reactor at 498 K and elevated pressure deploying a 2.5 wt % Pt/C catalyst to yield hydrogen. The highest hydrogen selectivity was 62%. No large differences were found when comparing a commercial available sorbitol to the technical sorbitol/mannitol mixture in terms of conversion levels and selectivity to the gas-phase products. This was accompanied by a similar distribution of products retained in the liquid phase. The efficiency of APR when utilizing Pt/C was found to be still insufficient for industrial implementation in terms of hydrogen production. Thus, additional efforts should be made to increase the obtained amounts of hydrogen per mole of converted sugar alcohols.     

Structural analysis of bio-oils from sub-and supercritical water liquefaction of woody biomass

Woody biomass was liquefied by water in an autoclave in the reaction temperature range of 280–420 °C with sodium carbonate as the catalyst. The experimental results show that the yield of the main liquefaction product (heavy oil) was significantly influenced by the process conditions. The maximum yield of heavy oil was obtained at reaction temperature 380 °C. The heavy oils obtained at different reaction temperature were analyzed by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS). The analytical results show the heavy oil is complex compound that contain hydrocarbon, aldehyde, ketone, hydroxybenzene and ester.     

降低柴油机排气中氮氧化物含量的催化还原系统的研究

本文提出了一个带二次燃料喷射的NO2催化还原系统，并对其进行了模拟试验。试验中发现，用燃料作还原剂时，以Al3O3为载体的AgAlO2催化剂在NO2的还原反应中表现出较强的活性，是一种较理想的NO2还原反应催化剂。试验中还发现，随着喷入的燃料所产生的醛类的浓度的增加，NO2的转化效率不断增加。     

纤维素催化氢解制取多元醇的研究进展

化石资源日益减少和使用化石资源带来的气候与环境问题促使人们将目光转向可再生的生物质资源。由生物质资源制备高附加值的化学品已成为国内外的研究热点。通过催化氢解将纤维素转化为多元醇化学品是一种可行的手段。本文总结了由纤维素氢解制备多元醇的最新研究进展,重点介绍了纤维素转化为山梨醇/甘露醇、异山梨醇和小分子多元醇（丙二醇和乙二醇）的催化剂体系以及可能的转化途径。最后分析了该领域存在的问题和今后的研究趋势。