含PVC混合塑料水热反应中的氯迁移特性

聚氯乙烯(PVC)的大量使用导致城市生活垃圾(MSW)中的氯含量相对较高。水热反应将氯尤其是有机氯高效脱除是实现垃圾无害化处理和资源化利用的前提。MSW中塑料组分复杂,有机氯主要来源于PVC,研究影响PVC水热脱氯中氯迁移特性的因素具有重要意义。选取两种型号(HB-65和S-65)的PVC和聚乙烯(PE)、聚丙烯(PP)、聚苯乙烯(PS)、丙烯腈-丁二烯-苯乙烯(ABS)作为原料,研究了PVC自身性能和水热条件对氯脱除的影响规律,考察了塑料混合水热过程中的氯迁移特征。结果表明,PVC自身性能是影响水热脱氯内在因素,水热条件如水热温度、保温时间和反应物浓度是外在因素。塑料因不同的热膨胀性在混合水热过程中存在协同效应,添加PP和ABS使PVCHB-65脱氯率分别下降了71.66%和70.96%,使PVCS-65脱氯率分别下降了19.05%和18.15%;添加PE和PS使PVCHB-65脱氯率分别下降了71.06%和43.06%,使PVCS-65脱氯率分别升高了8.20%和46.70%。     

变压器油中的PCB纳米氢化钠化学脱氯的定量表征

开发了在温和条件下,利用自行合成的纳米氢化钠深度脱除变压器油中的多氯联苯(PCB)技术。总质量分数为0 5%的PCB可以降解到0 028%,降解后的溶液用纳米氢化钠二次处理后,PCB总质量分数可进一步降解到0 0001%。基于GC/ECD的检测技术,评价了纳米氢化钠的脱氯效果以及其去毒性效应。结果表明,氯原子数目越多,分子对称性越差,脱氯反应越快;从五氯联苯脱氯表征发现PCB上的脱氯活性的顺序依次为:对>间>邻;在脱氯过程中,由于高氯原子数的联苯降解为低氯原子数的联苯,纳米氢化钠脱氯技术还降低了PCB的毒性。     

Catalytic coprocessing of LDPE with coal and petroleum resid using different catalysts

Catalytic coprocessing of low density polyethylene (LDPE) with coal and heavy petroleum resid was investigated using four different catalysts that included both hydrotreating and hydrocracking catalysts. Reaction systems that were evaluated included LDPE alone; LDPE with coal; and LDPE, coal, and resid. The catalysts used were NiMo/Al₂O₃, a hydrotreating catalyst with some hydrocracking activity, and the hydrocracking catalysts Zeolyst 753, NiMo/zeolite, and HZSM-5. These catalysts were reacted individually or in combinations of 10 wt.% of each hydrocracking catalyst in NiMo/Al₂O₃. The catalytic reactions were performed at two temperatures, 400 and 430°C, using 1 wt.% of each catalyst or a combination of catalysts on a total feed basis. The effects of the different catalysts on the reaction products were measured in terms of solvent fractionation and total boiling point distribution. Reactions at the higher reaction temperature of 430°C resulted in substantially higher conversion and production of lighter products than the reactions at 400°C. The LDPE reaction system was sensitive to the catalyst type, and yielded increased conversion and lighter products when Zeolyst 753 and NiMo/zeolite were used. By contrast, the conversion and product slate obtained from the LDPE and coal systems were low and showed no effect due to the different types of catalyst. Introduction of resid to the LDPE/coal system increased the reactivity of the system and allowed the catalysts to have a larger effect. The hydrocracking catalysts were the most active in producing more conversion and hexane soluble material. Comparison of the effect of increasing the reaction time up to 5 h with 1 wt.% catalyst loading to the effect of increasing the catalyst loading from 1 wt.% to 10 wt.% for a reaction time of 1 h showed that increased reaction time was much more effective than catalyst loading in converting the solid LDPE to liquid reaction products.     

Catalytic degradation and dechlorination of PVC-containing mixed plastics via Al-Mg composite oxide catalysts

A alumina-magnesium composite oxide catalyst (Al-Mg) was synthesized for catalytic degradation of poly vinyl chloride (PVC) containing polymer mixtures, i.e. polypropylene (PP)/PVC, low-density polyethylene (LDPE)/PVC, polystyrene (PS)/PVC, and LDPE/PP/PS/PVC. In the catalytic degradations the Al-Mg composite oxide catalyst accelerated the rate of polymer degradation and lowered the carbon distribution of liquid products. In addition, it showed good effect on the fixation of evolved HCl and greatly decreased the chlorine content in the oil. These results suggested that the Al-Mg composite oxide catalyst can be effectively used for catalytic degradation and dechlorination of PVC-containing mixed plastics.     

废旧塑料薄膜分离方法的实验研究

以水作为浮选剂对含聚氯乙烯（PVC）、聚乙烯（PE）、聚丙烯（PP）的废旧塑料薄膜进行分离,以实现对PVC的回收。考察了浮选液密度、分离温度、固液比、润湿剂含量、搅拌速度及分离时间等因素对PVC回收率的影响。结果表明,最佳分离条件为：浮选液密度1.04 g/cm3,分离温度30 ℃,固液比1：50,润湿剂含量0.2 %（质量分数,下同）,搅拌速度50 r/min ,分离时间8 s;PVC的最大回收率可达98 %。     

Pt/CeO2 catalysts in selective hydrogenation of crotonaldehyde: high performance of chlorine‐free catalysts

The hydrogenation of crotonaldehyde was conducted in gaseous phase, at atmospheric pressure, on Pt/CeO₂ catalysts prepared from metal precursors containing or not chlorine. The activities and selectivities were studied, at 253 K, as a function of the reduction temperature of the catalyst (473–993 K). The Pt/CeO₂ catalyst, prepared from tetraammineplatinum nitrate, led to 5–20% crotyl alcohol selectivity when the catalyst was reduced at low temperature (473–673 K), while increasing the reduction temperature up to 973 K, the crotyl alcohol selectivity reached more than 80%. Repeating a series of experiments after a re‐calcination treatment at 673 K, the selectivity decreased to only 40% after 473 K reduction to reach again more than 80% after 673 K reduction temperature. A phase transformation of Pt to CePt₅ was observed by XRD analysis after 973 K reduction treatment. Differently on Pt/CeO₂ catalysts containing chlorine, prepared from either chloroplatinic acid or tetraammineplatinum chloride, the crotyl alcohol selectivity never exceeded 30% and did not form alloy up to 973 K reduction temperature. The main results are interpreted considering that the activity of CePt₅ for C=C hydrogenation is low compared to unmodified platinum catalyst and the activation of the carbonyl bond is induced by the presence of oxygen vacancies sites located at the interface between ceria and the metallic particles. The results are in good accordance with the information known at the present time on the metal–support interactions in Pt deposited on CeO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

非临氢降凝催化剂的研究

研制了降凝催化剂FC-DB，在常压非临氢条件下以抚顺石油二厂催化裂化柴油和辽化加氢裂化尾油为原料，考察了温度、空速对降凝效果的影响。催化裂化柴油凝点可降低5-25℃，液体收率98％以上，柴油收率85％以上；加氢裂化尾油凝点可降低36～56℃，液体收率在95％左右，润滑油基础油的收率在90％左右，裂解气产量很少，降凝效果显著。     

STUDY ON THE PYROLYSIS AND RECYCLING OF PVC WASTE AS AN ENERGY SOURCE

The pyrolysis dechlorination of PVC (polyvinyl chloride) has been carried out by batch operation under atmospheric pressure. The kinetics involved in the PVC thermal decomposition was studied by using thermogravimetric technique. Several tests were carried out at the heating rate of 5-10℃/min, the yields of products and the distribution of chlorine were also studied. The kinetic parameters such as activation energies, reaction orders and preexponential factors under nitrogen atmosphere were calculated by applying Friedmans method. The results showed that the PVC thermal degradation is substantially a two-step process. The first step mainly involves dechlorination of the polymers. HCI is the main volatile product and this reaction can be seen as a first-order reaction. A kinetic model for the thermal dechlorination of PVC has been developed.     

离子膜电槽送电初期淡盐水含游离氯高的解决方案

介绍了离子膜电槽送电初期脱氯淡盐水含游离氯的情况，分析了造成脱氯淡盐水中游离氯含量高的原因并确定了解决方案。     

Influence of the different dechlorination time on catalytic performances of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

Catalytic dehydrogenation of propane has recently received considerable attention because of the increasing demand for propene. Among several catalysts, PtSnNa/ZSM-5 catalyst is one of the most suitable ones. In this study, PtSnNa/ZSM-5 catalysts with different content of chlorine were prepared by changing the time of catalyst dechlorination. The obtained catalysts were characterized by X-ray fluorescence (XRF), XRD, nitrogen adsorption, ²⁷Al MAS NMR, NH₃-TPD, H₂ chemisorption and TPR. It was found that with the increase of treatment time, more framework aluminum atoms were removed from tetrahedral positions, leading to the loss of Sn species and the decrease of catalyst acidity. Meantime, the porous properties and the interactions between Pt and Sn of the catalysts changed remarkably, which was disadvantageous to the reaction. Compared with the dechlorinated catalysts, the fresh sample with suitable content of chlorine exhibited the best reaction activity and stability. The average yield of propene was about 30.4% over 45 h for the reaction of propane dehydrogenation at 590 °C. Finally, a model was proposed for the influence of dechlorinated treatment on catalytic properties of PtSnNa/ZSM-5 catalyst for propane dehydrogenation.     

Dechlorination of fuels in pyrolysis of PVC containing plastic wastes

The objective of this work is the study of several dechlorination methods devoted to reduce the chlorine content of the liquids obtained in pyrolysis of PVC containing plastic wastes. A mixture of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyvinyl chloride (PVC) has been pyrolysed in a 3.5 dm³ semi-batch reactor at 500 °C for 30 min. Stepwise pyrolysis carried out at several temperature and time conditions, the addition of CaCO₃ for chlorine capture and a combination of both methods have been studied. Additionally, some thermogravimetric analyses have been carried out in order to establish the best conditions for PVC dehydrochlorination in the presence of other plastics. It has been proved that the application of dehydrochlorination methods plays a significant role in the characteristics of pyrolysis liquids. Stepwise pyrolysis is an effective method for reduction of the chlorine content of pyrolysis liquids; additionally, heavier hydrocarbons and lower quantity of aromatics in the liquids than in conventional pyrolysis are obtained. The addition of CaCO₃ leads to the retention of a significant amount of chlorine in the solid, but more chlorine than in a conventional run is found in the liquids, which contains a higher amount of aromatics.     

Understanding the correlation between calcination temperature and performance in low-temperature methanation over Ni-Zr/Al2O3 catalysts

Low-temperature methanation of CO in the continuous stirred tank reactor (CSTR) over Zr doped Ni/Al₂O₃ catalyst calcined at different temperatures (673, 723, and 823 K) was investigated. XRD, TPR, XPS, ICP, SEM, and S-TPR techniques were employed to characterize the fresh and spent catalysts. Based on the characterization results, it was found that low-temperature (673 K) calcination could effectively prohibit the formation of NiAl₂O₄ spinel, thereby resulting in more reducible NiO particles, which were the essential precursor of methanation active sites over the catalyst surface. Thus, the highest CO conversion of 93.6% was achieved over the 25N3ZA-673 catalyst. In addition, the deactivation rate of 25N3ZA-673 was relatively slow in comparison to 25N3ZA-823 due to the presence of more reducible NiO. The formed nickel carbonyl species (Ni[CO]_x), which quickly decomposed at a higher reaction temperature, was closely related to the catalyst deactivation. Therefore, 25N3ZA-673 possessed much better stability at 593 K than that at 553 K.     

Electrode reaction of the Np3+/Np couple at liquid Cd and Bi electrodes in LiCl–KCl eutectic melts

The electrode reactions of the Np³⁺/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in the LiCl–KCl eutectic melt. It was found that the diffusion of Np³⁺ in the salt phase was the rate-determining step in the cathodic reaction when the concentration of NpCl₃ was less than about 1 wt % and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np³⁺/Np couple at the liquid Cd electrode at 723, 773 and 823 K were observed to be more positive than those at the Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift results from a lowering of the activity of Np in the Cd phase according to the formation of the NpCd₁₁ alloy at 723 K and NpCd₆ at 773 and 823 K. The redox potentials of the Np³⁺/Np couple at the liquid Bi electrode at 723, 773 and 823 K were more positive than those at the Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which is attributable to a lowering of the activity of Np in the Bi phase due to the formation of NpBi₂.     

钯复合膜反应器中异丁烷催化脱氢反应

引　言异丁烷脱氢反应是一个受热力学平衡限制的反应 ,平衡转化率很低 ,若将膜反应器用于该反应 ,则可以通过膜不断地从反应区选择性分离出氢气 ,克服了反应受热力学平衡制约的缺点 ,这样就可降低反应温度和减压程度的要求 ,改善反应的工艺条件 ,从而达到高效和节能的目的 .文献中已分别对钯 /陶瓷复合膜[1,2 ]和钯 -钌 (钌的质量分数为 2 % )合金膜[3]反应器中的异丁烷脱氢反应进行了初步研究 .前文[4 ]已对用改进的化学镀新工艺制备的钯和钯 -银 /陶瓷复合膜进行了表征 ,本文将用钯-银 /陶瓷复合膜反应器进行异丁烷脱氢反应的研究 .本工作…     

基于微波辅助脱除硫醇甲基锡废底料中的氯

以硫醇甲基锡废底料为研究对象,通过元素组成和XRD分析,结合废底料物性特征,设计了微波辅助干馏回收低沸点物质,残渣脱氯后用作锡冶炼精料的基本构思。实验研究表明：干馏可回收质量分数约15.86%的低沸点物质,同时可脱除约31.06%的氯。以残渣中氯含量为考察指标,系统研究了残渣与过氧化氢液固比、氧化静置时间、残渣与浓硫酸液固比、微波强化时间对氯脱除率的影响,结果表明：过氧化氢与残渣液固比为1∶5、氧化静置时间为30min、浓硫酸与残渣液固比为1∶3、微波强化时间为80min时,残渣中氯质量分数为0.59%,氯的脱除率可达到97.48%,满足企业锡冶炼精料氯质量分数＜0.8%要求。通过对微波浸取机制讨论以及残渣XRD、SEM的表征,初步对干馏残渣脱氯过程进行了机理分析,为硫醇甲基锡废底料中氯的脱除提供了理论依据,研究成果具有较好的应用前景。     

Bridging the gap between liquid and vapor phase hydrocracking

Research aimed at fundamental understanding of industrial reactions often leads to important differences, or so-called gaps, between laboratory and industrial conditions. Vapor and liquid phase hydrocracking of parapur, a mixture of linear alkanes in the range from C₉ to C₁₄, has been performed on a Pt/H-USY zeolite at temperatures between 503 and 533 K, total pressures between 1 and 7.7 MPa and molar inlet hydrogen to hydrocarbon ratios from 3 to 300. At these conditions ideal hydrocracking occurs, except for the heaviest components at the highest temperatures, lowest pressures and highest molar inlet hydrogen to hydrocarbon ratios. The individual component product distributions obtained at vapor and liquid phase conditions were identical to those reported in the literature for pure n-alkane hydrocracking. A preferential conversion of the heavier hydrocarbons in the mixture was observed for vapor phase parapur hydrocracking. At liquid phase conditions this preferential conversion of heavier hydrocarbons is still observed, but much less pronounced.A single kinetic model accounting for all these features allows to adequately describe both vapor and liquid phase parapur hydrocracking. It suffices to account explicitly for (i) the non-ideality of the fluid phase, (ii) the destabilization of the physisorbed phase in the catalyst micropores and (iii) the increased strength of the acid sites at the liquid phase conditions. The last two effects are quantified by so-called physisorption and protonation excess.     

Coupled hydrogenation and ring opening of tetralin on potassium modified Pt/USY catalysts

Coupled hydrogenation and ring opening of tetralin (THN) on Pt/USY catalyst were performed on a high-pressure fixed-bed reactor. The effect of reaction temperature in range of 100–300 °C and the nature of the catalyst (metal and acid sites) on the catalytic performance were studied. The results indicated that the extent of hydrocracking, a sequential reaction of ring opening, should be reduced in order to maintain high yields of the ring opening products (ROP). Introduction of the Pt component accelerated the hydrogenation and ring opening of the THN significantly. It was also found to be an effective way to optimize the acid properties of the catalysts by introducing an appropriate amount of potassium to the catalyst, such that the strong acid sites of the catalysts were diminished, and a higher ROP yield could be obtained as a result of the inhibiting of the hydrocracking activity of the catalyst. When the yield of the C10 fractions could be maintained at 90 wt.%, then a maximal ROP yield of 35.6 wt.% could be obtained on a 0.5 wt.% Pt/USY catalyst loaded with 2.0 wt.% of K.     

Prediction of product quality for catalytic hydrocracking of vacuum gas oil

The main objective of this work is to develop a predictive model for predicting the product quality of vacuum gas oil (VGO) hydrocracking process. Experimental data were obtained using a pilot plant hydrocracking catalytic reactor loaded with the same catalyst type used in a local refinery. Two sets of experimental runs were conducted under various operating conditions. The first one consisted of 18 runs and was used for parameter estimation, while the second set consisted of 29 runs and was used for model validation. Distillation curves of the cracked products were obtained using the simulated distillation (SimDist) test. A distribution model based on probability density function was used to develop the predictive model. The distribution model presents the boiling point as a function of the distilled weight fraction. Model parameters were estimated and related to the specific gravity of the cracked product. Model validation results showed that the proposed model is capable of predicting the distillation curves of the hydrocracked products accurately, especially at high operating severity. Simplicity and accuracy of the developed model makes it suitable for online analysis, to estimate the conversion as well as the product distribution of hydrocracking units in refineries.     

Utilization of vegetable oils as an alternative source for diesel-type fuel: hydrocracking on reduced Ni/SiO2 and sulphided Ni-Mo/γ-Al2O3

Vegetable oil hydrocracking was studied in a batch reactor under high hydrogen partial pressure (10–200 bars) at 623–673 K, catalyzed by either reduced Ni/SiO₂ or sulphided Ni-Mo/γ-Al₂O₃. We have established the sequence of reactions which transform a vegetable oil into a diesel-type fuel. We have demonstrated the role of the catalyst in each of these reactions, and the occurrence of thermodynamic equilibria restricting the completion of the transformation. The displacement of these equilibria was achieved by an increase in hydrogen pressure, where molar yields close to 100% were attained. The corresponding product is a mixture of hydrocarbons (essentially normal alkanes in the diesel fraction).     

Pd/Fe对-二氯苯的催化脱氯及其动力学

o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water through catalytic reduction. The dechlorination reaction is believed to take place on the surface site of the catalyst via a pseudo-first-order reaction. The final reduction product of o-DCB is benzene. The dechlorination rate increases with the increase of bulk loading of palladium due to the increase of both the surface loading of palladium and the total surface area. Dechlorination efficiency accounts for 90% at Pd/Fe mass ratio 0.02% and metal to solution ratio about 53.3g-L-1 in 120 minutes. Dechlorination is affected by the reaction temperature, pH, Pd/Fe ratio and the addition of Pd/Fe. Ea is found to be 102.5kJ.mol-1 in the temperature ra,nge of 287-313K.