Adsorption of hydrocarbons by ZSM-5 zeolites with different SiO2/Al2O3 ratios: a combined FTIR and gravimetric study

In metal-free ZSM-5, the decrease in the concentration of Bronsted and Lewis acid sites parallels the increase in the SiO₂/Al₂O₃ ratio. In the presence of residual moisture, the adsorption of small alkanes does not markedly depend on the SiO₂/Al₂O₃ ratio in the range from 30 to 150. The acidity is more important for the adsorption of alkenes (propene) which oligomerize following adsorption. The addition of 5 wt.% of La does not significantly affect the strength of the surface acid sites but does decrease their concentration. It causes a transformation, in a part, of the Bronsted acid sites. These new centers could perhaps be assigned to LaO(OH) or La(OH)₂⁺ species which may be formed on the surface in La-containing ZSM-5. La could exchange only the strongest acidic sites without inducing large changes in their total concentration. La addition has a very small effect on the adsorption of small hydrocarbons. The exchange of the protons by Cu²⁺ decreases the concentration of Bronsted acid sites. At a sufficient loading of the ZSM-5 by Cu²⁺, i.e. at an atomic ratio Cu/Al > 1.0, the exchange can almost totally suppress the Bronsted acidity. Another effect of the ion exchange is the suppression of the adsorption capacity of small hydrocarbons due to lowered surface area and internal pore volume. The lowered available internal pore volume also limits the extent of the oligomerization of propene.     

An in situ infrared study of NO reduction by C3H8 over Fe‐ZSM‐5

The interactions of NO, O₂ and NO₂ with Fe‐ZSM‐5, as well as the reduction of NO by C₃H₈ in the presence of O₂, have been investigated using in situ infrared spectroscopy. The sample of Fe‐ZSM‐5 (Fe/Al =0.56) was prepared by solid‐state ion exchange. NO adsorption in the absence of O₂ produces only mono‐ and dinitrosyl species associated with Fe²⁺ cations. Adsorbed NO₂/NO₃ species are formed via the reaction of adsorbed O₂ with gas‐phase NO or by the adsorption of gas‐phase NO₂. The reduction of NO in the presence of O₂ begins with the reaction of gas‐phase C₃H₈ with adsorbed NO₂/NO₃ species to form a nitrogen‐containing polymeric species. A reaction pathway is proposed for the catalyzed reduction of NO by C₃H₈ in the presence of O₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

毒死蜱的合成研究

在特定的催化剂条件下,以３,５,６－三氯吡啶－２－醇钠为原料,合成毒死啤,确定了适宜的工艺条件,收率在９３％以上。     

Fatty acid composition of some pine seed oils

The fatty acid composition of seeds from seven species of the genusPinus (P. pinaster, P. griffithii, P. pinea, P. koraiensis, P. sylvestris, P. mughus, andP. nigra) was established. Pine seeds are rich in oil (31–68% by weight) and contain several unusual polymethylene-interrupted unsaturated fatty acids with acis-5 ethylenic bond. These are thecis-5,cis-9 18:2,cis-5,cis-9,cis-12 18:3,cis-5,cis-11 20:2, andcis-5,cis-11,cis-14 20:3 acids, with a trace ofcis-5,cis-9,cis-12,cis-15 18:4 acid. Their percentage relative to total fatty acids varies from a low of 3.1% (P. pinea) to a high of 30.3% (P. sylvestris), depending on the species. The majorcis-5 double bond-containing acid is generally thecis-5,cis-9,cis-12 18:3 acid (pinolenic acid). In all species, linoleic acid represents approximately one-half the total fatty acids, whereas the content of oleic acid varies in the range 14–36% inversely to the sum of fatty acids containing acis-5 ethylenic bond. The easily available seeds fromP. koraiensis appear to be a good source of pinolenic acid: their oil content isca. 65%, and pinolenic represents about 15% of total fatty acids. These values appear to be rather constant.Pinus pinaster, which is grown on several thousand acres in the southwest of France, is an interesting source ofcis-5,cis-11,cis-14 20:3 acid (7% in the oil, which isca. 35% of the dehulled seed weight), an acid sharing in common three double bonds with arachidonic acid. Apparently,P. sylvestris seed oil contains the highest level ofcis-5 double bond-containing acids among pine seed oils that have ever been analyzed.     

一种重组融合抗菌肽ClavE-HD5的原核表达

根据海鞘Clavanins抗菌肽(ClavE)氨基酸序列和人HD5氨基酸序列,设计了一个融合的新抗菌肽ClavEHD5,通过PCR方法以大肠杆菌偏好密码子合成该融合重组肽的编码DNA,将该DNA克隆到大肠杆菌表达载体pET30α中,构建了ClavE-HD5的融合表达质粒。测序结果表明,克隆分子序列正确,可以表达1个12kDa的带标签融合蛋白。经转化大肠杆菌表达菌株E.coli Rosetta(DE3)后,以IPTG诱导并经Tricine-SDS-PAGE检测发现,凝胶中出现预期大小的多肽带,表明成功表达出重组的ClavE-HD5的融合抗菌肽。     

2-(1-H-四唑)-4’-甲基联苯的合成

以2-氰基-4'-甲基联苯(Ⅱ)为原料,与氨基钠反应得到2-脒基-4'-甲基联苯(Ⅲ),该化合物与水合肼发生取代反应得到4'-甲基-[1,1'-联苯]-2-甲酰胺酰肼(Ⅳ),最后在酸性条件下与亚硝酸钠发生闭环反应得到2-(1-H-四唑)-4'-甲基联苯(Ⅰ),总收率达到81%,其结构经1HNMR和MS确证。     

Ti/IrO_2-Ta_2O_5电解-Fenton耦合法深度降解含酚废水

针对Fenton法处理废水效果不佳、试剂用量较大、投资成本较高的问题,采用形稳电极Ti/Ir O2-Ta2O5电解与Fenton耦合法处理含酚废水。考察了处理时间、p H值、电压、H2O2和Fe SO4·7H2O投加量对废水降解效果的影响,确定了Ti/Ir O2-Ta2O5电解与Fenton耦合法最佳工艺条件,对比研究了电Fenton法与Fenton法降解含酚废水效果。结果表明:随着处理时间、H2O2和Fe SO4·7H2O投加量的增加,苯酚和COD去除率呈现先增加后趋于平缓的趋势;随着p H值的升高呈现先增加后降低的趋势;在较低电压条件下,可获得良好的处理效果。在最佳工艺条件为p H值3.5、槽电压5.0 V、Fe SO4·7H2O投加量0.15 g/L、H2O2投加量0.3 m L/L、反应时间2 min时,处理初始质量浓度为100 mg/L的含酚废水,COD去除率为40.7%,苯酚去除率为94.2%,高于Fenton法苯酚去除率16.2%。电解与Fenton耦合法在较低电压条件下处理含酚废水,处理效果优于Fenton法,具有良好的应用前景。     

变色硅胶与ZSM-5沸石分子筛的吸附脱附特性

针对吸附材料在太阳能吸附空调系统中的应用, 对变色硅胶和ZSM-5沸石对水蒸气的吸附脱附特性进行了实验研究。结果表明, 在一定温度下, 两种吸附材料对水蒸气的吸附速率随相对湿度增大而增加, 但增加幅度逐渐减小。环境温度对材料的吸附脱附性能有重要影响, 低温下易吸附, 高温时易脱附。温度升高, 材料的吸附脱附速率增加, 但平衡吸附量降低, 平衡脱附百分比升高。比较两种吸附材料的吸附特性发现, ZSM-5沸石具有较快的吸附速率, 但是其平衡吸附量低于变色硅胶。与变色硅胶的渐近线型吸附等温线不同, ZSM-5沸石的吸附等温线呈S型。比较两种材料的脱附特性发现, 在温度低于100℃时, ZSM-5沸石的脱附百分比大于变色硅胶。此外ZSM-5沸石能够在高温下进行脱附, 而变色硅胶在高温环境下会失去结晶水而变质, 因此脱附温度必须控制在120℃以下。     

粘结助剂对ZSM-5甲醇制烯烃催化活性的影响

采用机械混合法在H-ZSM-5分子筛中添加不同氧化物粘结剂,考察其对甲醇制烯烃(MTO)催化反应性能的影响,并采用x射线衍射(XRD)、氨气-程序升温脱附(NH3-TPD)实验、傅立叶红外光谱(FT-IR)和热重(TG)分析表征催化剂结构.结果表明:在H-ZSM-5中分别添加不同的氧化物粘结剂SiO2,γ-Al2O3和Kaolin(H-ZSM-5和氧化物质量比2∶1),在催化剂1 g,CH3OH与N2物质的量之比1∶4,催化剂质量与原料流速之比(W/F)为10(g·h)/mol,反应压力0.1 MPa和反应温度723 K的条件下,反应3 h,甲醇转化率为100%;与H-ZSM-5相比,烯烃产物分布发生了变化,添加SiO2使C3=选择性下降,添加γ-Al2O3使C1选择性增加,添加Kaolin使C3=选择性增加,同时添加Kaolin与SiO2(Kaolin和siO2质量比2∶1)的H-ZsM-5具有最高的C2=～C4=选择性,其中C3=选择性为38%.添加氧化物降低了催化剂的总酸量,反应11 h前后催化剂的物相没有发生明显变化,积炭不明显.     

铝源对合成ZSM-5分子筛晶粒大小及形貌的影响

分别采用偏铝酸钠、硫酸铝、异丙醇铝为铝源,四丙基氢氧化铵为模板剂,用水热合成法制备了不同晶粒大小及不同形貌的ZSM-5分子筛.通过XRD、SEM等表征手段对各种锚源合成的分子筛结晶度、晶粒大小及形貌进行了对比分析.结果表明,以偏铝酸钠和异丙醇铝为铝源合成的ZSM-5分子筛晶粒较小,形貌趋于球形,且化学硅铝比与晶化前驱体的硅铝比基本一致;而以硫酸铝为铝源合成的ZSM-5分子筛硅铝比低于投料硅铝比,且晶粒较大.