低温煤焦油与废旧塑料共熔油化的研究

用自制的反应装置研究了预处理后的低温煤焦油与废旧塑料共熔油化所得到的油品的性质，并分别与低温煤焦油和废旧塑料热裂解油品的性质进行了比较，考察了主要工艺条件对共熔油化过程的转化率和产品性质的影响。结果表明，在适当的添加煤焦油后，从废旧塑料热裂解和催化裂解得到的汽油的质量有所提高，但对柴油的质量影响不大。采用低温煤焦油与废旧塑料共熔油化的工艺不仅为“白色污染”的处理开辟了一条新途径，而且扩大了低温煤焦油的应用     

聚苯乙烯的催化裂解研究

由于塑料性质稳定,难以自然降解,其废弃物不仅严重污染环境,更造成了资源浪费.因此,废旧塑料的再资源化对环境保护和可持续发展有着重要意义.废塑料再资源化回收技术是指将废塑料热裂解或催化裂解、回收燃料油和化工原料的技术~([1,2]).     

用废旧塑料制造高品质燃料油

用废旧塑料制造高品质燃料油美国燃料化学家M. M. Taghiei等人在沙浴中将沸石催化剂与废旧塑料混合。然后将得到的浆状物在“tubingbomb”反应器中进行高压反应。通入氢气并加热到,420C,一小时后,塑料裂解成小分子化合物,可用做高品质燃料油。     

废旧塑料改性再生的研究进展

塑料制品作为一种全球范围内广泛使用的商品,几乎已经渗透到了人类生活中的各个方面.同时,快速累积的废旧塑料对陆地和海洋环境产生了一系列的负面影响.值得注意的是,废旧塑料具有资源和废物双重属性.废旧塑料的回收品质和数量的提高,对于资源的高效利用、可持续发展和环境保护具有重大意义.本文介绍了废旧塑料常用的分选方法,综述了近年...     

乙烯在煤焦及石英砂床层上裂解实验研究

以石油炼制过程中产生的炼厂气与煤共转化利用为背景,采用小型石英管固定床反应装置,在850℃～1000℃下,对乙烯在空床、彬县煤焦以及石英砂床层上的裂解反应进行了研究。结果表明,乙烯裂解产物包括氢气、甲烷、乙烷及裂解炭,反应温度越高,裂解越彻底,生成的氢气越多;850℃～950℃时,乙烯在彬县焦上初始转化率最高,随着反应的进行逐渐降低到一个较低的平衡值,并且与在石英砂上裂解结果接近。这说明新鲜彬县煤焦对乙烯裂解呈现良好的催化作用,但随着反应进行其催化活性由于裂解生成的炭沉积在煤焦表面而逐渐丧失。1000℃时乙烯在石英砂上和空床裂解转化率均可达到94％,即在此温度下乙烯无需催化剂通过热作用即可接近完全裂解。     

杂多酸催化松香裂解反应研究

对杂多酸 (HPA)催化松香裂解反应及反应条件进行了研究 ,并对裂解产生的挥发油进行了气相色谱分析。研究内容包括反应温度、反应时间、催化剂种类及用量对反应结果的影响。结果表明 :在杂多酸催化剂用量大于 0 .0 5%、反应温度高于 1 80℃的条件下 ,杂多酸可将松香裂解为深色油状物 ,同时生成水和挥发性油。杂多酸的种类、用量以及反应温度的改变不影响裂解产生的挥发油的组分构成 ,但影响某些组分的相对比例。裂解反应包括了碳碳键和碳氢键的断裂     

氯化钙催化纤维素热裂解动力学研究

用差示热重分析仪对氯化钙纤维素热裂解动力学催化影响进行了研究。结果表明，氯化钙对焦炭的形成具有强烈的促进效果，使热裂解最终残留物产率从5％提升到10％以上，氯化钙的存在影响到热失重初始阶段活性纤维素的生成，使热重曲线向低温侧移动，并在低温段产生了小的失重速率峰。通过热重分析发现，氯化钙催化条件下纤维素热裂解动力学参数被分为了三段，分别对应于活性纤维素的生成、炭化和活性纤维素转化为挥发分产物三个区间，并依次成为整体失重过程的控制步骤。结合Broido-Shafizadeh机理分析以及与纯纤维素热裂解动力学参数的对比，氯化钙对这三个主要反应步骤都产生了促进效果，其中以催化焦炭的生成最为明显，在促进焦炭化的过程中，降低了气体产物的生成比率。     

加拿大合成原油瓦斯油裂解反应规律与产物生成机理

利用小型固定流化床实验装置研究了加拿大合成原油重瓦斯油(HGO)和轻瓦斯油(LGO)的催化裂解性能和热裂解性能。HGO和LGO催化裂解总低碳烯烃(乙烯+丙烯+丁烯)产率在660℃附近达到最大值,分别为33.8%和35.6%。HGO和LGO热裂解反应程度很大,700℃的转化率分别为66.7%和76.3%。HGO热裂解总低碳烯烃的产率在680℃达到最大值27.9%。通过对比分析催化裂解与热裂解气体产物产率的比值发现,催化剂的加入促进了乙烯和液化气的生成,同时抑制了甲烷和乙烷的生成。研究结果揭示了小分子烃类的生成机理,甲烷和乙烷主要是自由基反应的产物,乙烯和液化气是自由基反应和正碳离子反应的共同产物。     

四氢叶酸辅酶模型1, 2, 3-三取代咪唑啉盐的质谱裂解行为

讨论了１,２,３－不对称取代咪唑啉盐各种离子的生成途径以及取代基对裂解方式的影响并分析了该类化合物的主要裂解方式。在所有中的均ｍ／ｚ＝１２７（１＾＋）的离子峰和有机正离子Ａ峰存在,表明化合物１和２均有机正离子和碘离子形成的盐。化合物１和２的质谱有相似的裂解方式;有机正离子发生失掉氮原子上的一个取代基而保留咪唑啉环产生Ｄ,Ｅ,Ｆ离子的裂解方式。更重要的是咪唑啉环有相同的裂解方式：Ｃ＾２－Ｎ＾３键和Ｃ     

裂解气相色谱—质谱法对聚乙烯醋酸乙烯酯裂解机理的探讨

本文采用裂解气相色谱和裂解气相色谱—质谱法对聚乙烯醋酸乙烯酯(简称EVA)在不同实验条件下的裂解行为进行了探讨,得出了EVA组成与裂片产量的线性关系式,从而不仅证实了E.M.Barrall等人提出的EVA裂解生成醋酸的机理,而且提出了EVA裂解生成甲烷、二氧化     

溶剂对聚氯乙烯-聚乙二醇-KOH体系脱氯行为的影响

废旧塑料的回收利用是当今研究的热点之一.据报道,2007年中国聚氯乙烯(PVC)产量高达960万吨[1],如何合理利用相应产生的废旧PVC是一个十分重要的课题.     

Dechlorination behaviour of flexible poly(vinyl chloride) in NaOH/EG solution

Flexible poly(vinyl chloride) (PVC) was found to be dechlorinated in NaOH/ethylene glycol (EG) solution at moderate temperature and at atmospheric pressure. The degree of dechlorination increased over time with all particle sizes and with decreasing particle size. Decreased particle size resulted in an increased effective surface area, increasing the contact between the material and OH⁻ in the NaOH/EG solution, which contributed to the high degree of dechlorination. The dechlorination of flexible PVC in NaOH/EG solution was expressed as a first-order reaction and proceeded under chemical reaction control. Diisononyl-phthalate (DINP) in the flexible PVC powder decomposed readily into phthalic acid and isononyl alcohol in a short time. For the dechlorination of the flexible PVC, the substitution (S_N2) of chloride by the hydroxyl group was considered to be preferential to the elimination (E2) of hydrogen chloride.     

Dechlorination of poly(vinyl chloride) by 1-butyl-3-methylimidazoliumhydroxide

Highly efficient dechlorination of PVC has been realized at 180 °C and at atmospheric pressure, using 1-butyl-3-methylimidazoliumhydroxide ([Bmim]OH) as an environment-friendly reaction medium: in the absence of an external base or solvent the dechlorination efficiency is as high as 91.2%, while it is only 38.1% for PVC without ionic liquids. The dechlorination process follows first-order kinetics with apparent activation energy of 44 kJ mol⁻¹. Mechanistic analysis provides evidence for the equilibrium presence of carbene species, together with the hydroxide ions in [Bmim]OH, thus enhancing the dechlorination of PVC via a combined elimination and substitution mechanism.     

PP和PVC混合塑料的降解及脱氯研究

对聚丙烯(PP)和聚氯乙烯(PVC)混合物在380 ℃下的热降解进行了研究。检测了PP和PVC混合塑料降解液体产物的沸点分布，并用铁氧化物作为固体吸附剂以除去产品中的氯元素。同时还研究了该混合物在ZSM-5催化剂存在下的降解，与热降解相比，ZSM-5催化剂加快了降解的速率，并且降低了液体产品的沸点。铁氧化物α-FeOOH和Fe3O4则能有效地降低产品中的氯含量。     

Aqueous-phase synthesis of PAA in PVDF membrane pores for nanoparticle synthesis and dichlorobiphenyl degradation

This paper deals with bimetallic (Fe/Pd) nanoparticle synthesis inside the membrane pores and application for catalytic dechlorination of toxic organic compounds form aqueous streams. Membranes have been used as platforms for nanoparticle synthesis in order to reduce the agglomeration, encountered in solution phase synthesis which leads to a dramatic loss of reactivity. The membrane support, polyvinylidene fluoride (PVDF) was modified by in situ polymerization of acrylic acid in aqueous phase. Subsequent steps included ion exchange with Fe²⁺, reduction to Fe⁰ with sodium borohydride and Pd deposition. Various techniques, such as STEM, EDX, FTIR and permeability measurements, were used for membrane characterization and showed that bimetallic (Fe/Pd) nanoparticles with an average size of 20–30 nm have been incorporated inside of the PAA-coated membrane pores. The Fe/Pd-modified membranes showed a high reactivity toward a model compound, 2,2′-dichlorobiphenyl and a strong dependence of degradation on Pd (hydrogenation catalyst) content. The use of convective flow substantially reduces the degradation time: 43% conversion of dichlorobiphenyl to biphenyl can be achieved in less than 40 s residence time. Another important aspect is the ability to regenerate and reuse the Fe/Pd bimetallic systems by washing with a solution of sodium borohydride, because the iron becomes inactivated (corroded) as the dechlorination reaction proceeds.     

Dechlorination of poly(vinyl chloride) using NaOH in ethylene glycol under atmospheric pressure

A solution of NaOH dissolved in ethylene glycol (EG) was effective in the dechlorination of poly(vinyl chloride) (PVC) at atmospheric pressure. The degree of dechlorination increased with increasing temperature, reaching a maximum of 97.8% at 190 °C. The dechlorination proceeded under chemical control and exhibited first-order kinetics with an apparent activation energy of 170 kJ mol⁻¹. The apparent rate constant for dechlorination in 1.0 M NaOH/EG was approximately 150 times greater than that in 1.0 M NaOH/H₂O. In addition, dechlorination was faster at atmospheric pressure in NaOH/EG than under high pressure in NaOH/H₂O. The dechlorination reaction occurs via a combination of E2 and S_N2 mechanisms.     

Radiation-induced dechlorination of hexachlorobenzene

A study on radiation-induced dechlorination of hexachlorobenzene in alkaline ethanol solution was performed. At the beginning a higher efficiency for dechlorination has been found. The dechlorination is a chain reaction. The solubility of radiolytic products in ethanol-water (v/v 1:4) is higher than that of HCB in the same solvent. Hexachlorobenzene could be transfered into the solution and degraded partially if the soil contaminated by hexachlorobenzene was mixed with ethanol, then irradiated with γ-rays.     

Chemical modification of poly(vinyl chloride) by nucleophilic substitution

The reaction of poly(vinyl chloride) (PVC) in nucleophile (Nu)/ethylene glycol (EG) or Nu/N,N-dimethylformamide (DMF) solution was found to result in the substitution of Cl in PVC with Nu from solution, in addition to the straight elimination of HCl, both of which led to the dechlorination of PVC. Examined Nu⁻ were I⁻, SCN⁻, OH⁻, N₃⁻, and the phthalimide anion. For the Nu/EG solution, elimination was favoured over substitution for all Nu⁻. The ratio of substitution to dechlorination was notable, descending in the order OH⁻ > SCN⁻ = N₃⁻ > phthalimide anion > I⁻. For the Nu/DMF solution, the ratio of substitution to dechlorination was high, in the order SCN⁻ > N₃⁻ > I⁻ > phthalimide anion. In both cases, the orders of the ratios were similar to those of the nucleophilic reactivity constant, I⁻ > SCN⁻ > N₃⁻ > phthalimide anion, except for I⁻. The low ratio for I⁻ was attributable to the elimination of HI after the substitution of Cl in PVC with I in solution, because I⁻ is a strong nucleophile, as well as an excellent leaving group. Comparing the effect of EG and DMF on the substitution of Cl in PVC with Nu in solution, the ratio of substitution to dechlorination was higher for I⁻, SCN⁻, N₃⁻, and the phthalimide anion in DMF than in EG. The substitution of Cl in PVC with Nu in solution was found to occur preferentially in DMF versus EG.     

Catalytic stepwise pyrolysis of packaging plastic waste

In this paper the combination of catalytic and stepwise pyrolysis is explored. A mixture of polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC), which resembles real municipal plastic waste, has been pyrolysed in a 3.5 dm³ semi-batch reactor at 440 °C for 30 min using a ZSM-5 zeolite as catalyst. A low temperature (300 °C) dechlorination step has been carried out both with and without catalyst. It has been proved that the application of such dechlorination step gives rise to a 75 wt% reduction of chlorine in the liquid fraction. However, such step has a negative influence on the catalyst, which loses some catalytic activity. The optimum procedure in terms of quality and chlorine content of the products is the combination of first a low temperature step without catalyst, and second the catalytic pyrolysis step.     

具有多级孔道结构、高水热稳定性的含氧化镁Silicalite-1分子筛的合成

通过焙烧将分散在多孔氧化硅母体中的硝酸镁转化成高分散的MgO物种, 然后使用四丙基氢氧化铵(TPAOH)作为结构导向剂, 将含MgO 的母体通过水热晶化合成MgO/silicalite-1 分子筛复合物. X 射线衍射(XRD)、能量X射线光谱(EDX)和透射电镜(TEM)的结果表明MgO物种被均匀地分散在silicalite-1 分子筛晶体中. 将酸处理脱除氧化镁前后的样品在100%水蒸汽800℃ 条件下老化, 结果表明MgO 的引入有效地提高了分子筛的水热稳定性. 此外, 酸洗脱除MgO/silicalite-1分子筛中的MgO提高了分子筛结晶度, 同时引入了一定的介孔. N₂物理吸附-脱附数据证明了酸洗后分子筛中介孔的存在. 水热稳定性的提高和介孔的引入对于在高温下保持催化剂的孔道结构, 提高催化剂的抗积碳能力, 降低催化剂的失活速率以及延长催化剂的使用寿命起着非常重要的作用.