Aromatization of waste polyolefin pyrolysate over H-ZSM-5 zeolite-supported gallium oxide catalysts

H-ZSM-5 zeolite-supported gallium oxides were studied as aromatization catalysts for polyolefin pyrolysate. The catalysts were prepared by a conventional physical mixing method with a gallium content of 1.0 and 4.5 wt% and were reduced in flowing hydrogen at 585°C. To test their activity, a polyolefin sample was pyrolyzed and passed over a heated catalyst layer; the product was analyzed by gas chromatography/mass spectrometry. A continuous-flow fixed-bed reactor was used for aromatization of a model gas of polyolefin pyrolysate. For chlorine-free sources at 450°C, the catalyst with only 1.0 wt% gallium exhibited activity comparable to a gallium silicate catalyst. For chlorine-contaminated sources, the catalyst with 4.5 wt% gallium sustained catalytic activity for long periods. From the activity test results, it was found that zeolite-supported gallium catalysts prepared by the physical mixing method are suitable for converting polyolefin into aromatic hydrocarbons.     

改性沸石对2,4-二氯苯酚的去除作用

采用溴化十六烷基三甲铵(HDTMAB)制备改性沸石,在与天然沸石对比的基础上,研究了改性沸石在动态条件下去除2,4-DCP的效果。并对影响去除率的主要因素,包括沸石粒径、进水浓度,进水流速,沸石用量,进水pH值等进行研究。结果表明,细粒改性沸石在pH2.5左右时处理低浓度2,4-DCP溶液时,能取得较好的去除效果,流速较低时去除率最高可达80%以上。     

降低超稳分子筛生产污水中氨氮含量工艺研究

通过对催化裂化催化剂活性组分──超稳分子筛的生产工艺过程铵盐消耗的分析,在小试试验的基础上,结合装置实际情况,经优化工艺条件,改进工艺流程,降低交换过程铵盐投料比,并用后工序废液代替化学水用于前工序浆液的调配等手段,使铵盐消耗量由1.8t/t降至0.95t/t,每年可节约467.5万元;同时采用氨氮回收技术将高氨氮污水中氨氮含量由原来的5000mg/L降至200mg/L以下,为最终采用生物法将污水氨氮含量降至15mg/L以下达标排放奠定了坚实基础。     

Transfer of powders into flammable solvents overview of explosion hazards and preventive measures

This paper evaluates and analyses the explosion hazards associated with transfer operations of powders into large containers, hoppers and reactors, which may also contain flammable solvent vapours. The formation and characteristics of explosive atmospheres and the occurrence of process inherent ignition sources, such as static electricity are described. The most commonly applied preventive measures and technical equipment are outlined and discussed including their advantages and disadvantages.     

Prevention and suppression of explosions in gas-air and dust-air mixtures using powder aerosol-inhibitor

The prevention and suppression of explosions is a very topical field of research because annually hundreds of coal mine workers became their victims. In this research a very effective powder “powder for suppression of explosions” (“PSE”) for the suppression of explosions has been developed and tested. The experiments on suppression of explosions of a methane–air mixture (MAM) at a laboratory conditions using “PSE”-powder have been carried out. The possibility of lowering the power of coal-dust explosion with the help of a “PSE”-powder has been investigated. The feasibility of almost instantaneous disperse of powders using intentionally created mini-explosions (ammonal) was investigated. The barrel-suppressor of explosion in the experimental adit (tunnel) was studied and the large-scale tests for suppression of MAM-explosions in experimental adit were also subjects of study.     

改性的膨润土或沸石在废水处理中的应用展望

本文扼要介绍了改性的膨润土或沸石在废水处理中的应用及其吸附水中污染物的性能、机理和规律,指出了今后的研究工作中需要解决的问题,展望了它们在污水处理中的应用前景.     

稀土矿区污染农田土壤治理后稀土元素的赋存形态分析

针对赣南稀土矿区受污染农田土壤,研究添加改良剂沸石治理后土壤中稀土元素的含量及形态分布特征。分别采用酸法消解和Tessier连续提取法对土壤样品(土样)中稀土元素总量及赋存形态进行提取分析,并利用电感耦和等离子质谱仪(ICP-MS)测定其中15种稀土元素含量及其形态含量。结果表明,土样中各稀土元素总量高达1 296 mg/kg,远远高于全国土壤平均总量176.8 mg/kg,稀土钇(Y)含量高达386.01 mg/kg远高于其余14种稀土元素含量,土样中轻稀土元素含量与重稀土元素含量比值为0.66远小于全国土壤中轻稀土含量与重稀土含量比值(3.78),表明该稀土矿属重稀土富钇矿型,且加入沸石不能影响土样中稀土元素的总量变化;矿区农田土壤加入沸石治理前,碳酸盐结合态、有机物结合态、铁-锰氧化物结合态、可交换态和残渣态稀土元素含量分别占总量百分比分别为51.03%、29.6%、10.39%、7.52%和1.46%,加入沸石治理后,以上5种形态的稀土元素含量占总量百分比分别为8.19%、71.54%、9.35%、4.34%和6.58%,表明沸石对矿区农田土壤中稀土元素的形态分布有很大影响,并显著钝化稀土元素在土壤中的生物活性及可迁移性。     

Machining efficiency of powder mixed near dry electrical discharge machining based on different material combinations of tool electrode and workpiece electrode

Powder mixed near dry electrical discharge machining (PMND-EDM) is a novel electrical discharge machining (EDM) process. It is proposed to further improve the machining efficiency of dry EDM. The principle of material removal in PMND-EDM is illustrated and its deionization principle is proposed. The influence of residual heat on MRR is analyzed. The concept of superfluous residual heat is proposed. The material removal rate (MRR), the main index of machining efficiency for PMND-EDM process, is researched. Single factor experiments are performed to get effect of peak current, pulse on time, pulse off time, flow rate, tool rotational speed, air pressure and powder concentration on MRR under different material combinations of tool electrode and workpiece electrode. Thermal phenomena in PMND-EDM are illustrated. Effect of each process parameter on MRR of PMND-EDM is gotten and analyzed based on the deionization principle of PMND-EDM. Differences in MRR under different material combinations are found out. Brass tool electrode and W18Cr4V workpiece gain higher MRR under most of discharge conditions, while the superiority of copper tool electrode and 45 carbon steel workpiece in MRR arise when there is improper heat dissipation. The difference is analyzed based on the deionization principle of PMND-EDM.     

壳聚糖改性4A沸石分子筛颗粒去除低温水中硝酸盐的机理研究

为解决我国北方严寒地区常规工艺难以有效去除低温地下水中硝酸盐污染的问题,以4A沸石分子筛为载体,通过壳聚糖改性制备出一种具有低温去除水中硝酸盐功能的吸附颗粒,有望作为吸附剂应用于常规水处理工艺的提标改造.通过小试试验,研究壳聚糖改性4A沸石分子筛颗粒去除低温水中硝酸盐的反应机理,分析其去除硝酸盐过程的吸附动力学、吸附等温线、吸附热力学,并通过pH_PZC（零电点）测定、FT-IR（傅里叶红外光谱）和XPS（X射线光电子能谱）进一步分析其反应前、后表面物化特性.结果表明:①在温度为8~10℃下,壳聚糖改性4A沸石分子筛颗粒对硝酸盐的吸附平衡时间为8 h,平衡吸附量为1.88 mg/g.②吸附过程符合准二级动力学模型,吸附符合Langmuir和Freundlich吸附等温模型,吸附热力学参数△G0 < 0、△H0>0、△S0>0,表明吸附为熵增加的吸热过程.③壳聚糖改性4A沸石分子筛颗粒的pH_PZC为10.0,FT-IR结果表明,-NH₂和-OH官能团吸附了水中的硝酸根离子,XPS结果表明,N（1s）和O（1s）元素在吸附过程中参与反应.研究显示,壳聚糖改性4A沸石分子筛颗粒分子结构中的-NH₂和-OH基团通过静电结合和氢键作用与硝酸根离子进行吸附反应.      

阿克苏地区含氟地下水治理方法的分析

针对阿克苏地区存在的氟污染饮用水问题,综述了近年来国内外饮用水除氟方法,如石灰沉淀法、混凝沉降法、吸附法、离子交换法、电凝聚法、电渗析法、反渗透法等。介绍了天然沸石的结构特征;分析了沸石处理地下水的作用机理及再生问题;并对今后沸石法处理地下水的研究提出一些建议。