Surface properties of ZSM-5 modified by phosphorus

Phosphorus modification of ZSM-5 leads to extra framework P⁵⁺ and probably incorporation of +3 valence state of P in the framework. The resulting system has increased Brønsted acidity. Theoretical calculations also favour the postulate that phosphorus in +3 valence state can be incorporated into the lattice.     

6，7-二氢-5H-环戊烷并[b]吡啶

6,7-二氢-5H-环戊烷并[b]吡啶主要用于药物、杀菌剂和抗菌剂的研究,也被广泛应用于制备植物保护剂和合成树脂、防老剂以及塑料制品等。目前因其被作为第四代抗生素头孢匹罗的侧链而成为研究者竞相开发的热点。6,7-二氢-5H-环戊烷并[b]吡啶有实用价值的合成方法主要有N-羟基邻苯二甲酰胺法、丙烯醛法和己二酸二乙酯法。丙烯醛法中6,7-二氢-5H-环戊烷并[b]吡啶的收率为87.4%,具有较好的开发前景。     

On the preparation and properties of CuZSM-5 catalysts for NO decomposition

Equilibrium exchange isotherms were determined for the exchange of Cu²⁺ with NaZSM-5 at varying Cu(Ac)₂ concentrations in solutions of constant volume and zeolite weight. At low Cu²⁺ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary.     

4-(6′甲基苯并噻唑-2′-偶氮)-3,5-二氨基吡唑与钯显色反应的研究和应用

对6种苯并噻唑偶氮吡唑化合物的分析特性进行了探讨,着重研究了4—(6′—甲基苯并噻唑-2′-偶氮)-3,5-二氨基吡唑(MBTAP)与钯离子显色反应的光度性质。在非离子表面活性剂 Brij35存在下与钯离子形成橙红色的配合物。适宜的 pH 值范围为9.0～10.5.配合物的最大吸收波长为510nm,表观摩尔吸光系数为3.01×10~4L·mol~(-1)·cm~(-1)。钯在0～14μg/25mL,范围内服从比尔定律.显色体系可稳定11h。在柠檬酸存在下可消除 Fe~(3+)、Co~(2+)、Cu~(2+)、Ni~(2+)等离子的干扰。     

Kinetic modelling of the catalytic conversion of synthesis gas

A kinetic study for the one-step conversion of synthesis gas to gasoline on a ZnO–Cr₂O₃–ZSM-5 catalyst is described. On this catalyst, three reactions are involved in the overall transformation of synthesis gas: the methanol synthesis, the conversion of methanol to hydrocarbons and the water–gas shift reaction. Under the operating conditions selected for the study, it was found that the water–gas shift was at equilibrium and the methanol was completely converted to hydrocarbons. Consequently, it was postulated that the kinetics of the limiting reaction step, the methanol synthesis on the ZnO–Cr₂O₃ component, was the one that controls the overall reaction rate. Three kinetic model equations describing the rate of synthesis gas conversion on the bifunctional catalyst, were considered to fit the data of the experimental runs performed in a Berty well-mixed reactor. Those equations were derived under very special conditions where the methanol decomposition term could be neglected. It was also observed that in the kinetic equations a term involving the fugacity of CO₂ was required to predict the rate properly. The catalyst deactivation was also taken into account in the analysis.     

水杨醛型腙类试剂测定铝的研究

合成了以水杨醛为母体的４种腙类新荧光试剂，并对其与铝的荧光反应性能进行了比较研究，结果表明，５－溴－水杨醛水杨酰腙是一种优良试剂。它与铝在ｐＨ５．４醋酸－醋酸铵缓冲溶液中形成１３型荧光配合物，其λｅｘ＝３７０ｎｍ，λｅｍ＝４６０ｎｍ。建立的分析方法检测下限为１．１ｎｇ／ｍＬ，相对标准偏差为１．４５％。考察了３０余种共存离子的干扰情况。直接应用于葡萄糖注射液及常见饮料中微量铝的测定，结果满意。     

Evidence for non-site-isolation in ZSM-5 from ion-exchange and catalytic studies

Ion exchange of HZSM-5 samples with alkali metal cations, using metal chloride solutions, results in partially exchanged zeolites, MHZSM-5, M = Li, Na, K or Cs. The degree of exchange is found to increase with increasing ionic radius of the cations. The catalytic properties of the alkalized zeolites were evaluated using the reaction conditions under which the catalytic activity of the HZSM-5 samples in terms of n-hexane cracking is proportional to the aluminium content. From the residual catalytic activity exhibited by the Na-, K- and CsHZSM-5 samples it is concluded that each of the larger Na⁺, K⁺ and Cs⁺ ions is influencing more than one AlO ₄ ^– tetrahedron, implying that the aluminium sites in ZSM-5 are not isolated. The ion-exchange results are then interpreted in terms of non-isolated aluminium sites. The ion-exchange and catalytic properties of the zeolites as a function of aluminium content are also discussed.     

Combustion of methane over palladium ZSM-5 and mordenite catalysts

The effect of Pd-loading on Pd-NaZSM-5 and Pd-NaMordenite catalysts prepared by ion exchange was studied for methane combustion with excess oxygen (1% CH₄, 18% O₂, balance N₂) in the temperature range 40–500°C. Fresh and calcined samples (3 h, 450°C) showed methane conversions proportional to Pd-loading on Pd-NaZSM-5 catalysts, while conversions decreased with Pd-loading on calcined Pd-NaMordenite catalysts. TOF (number of methane molecules converted per second per Pd²⁺ ion) for over exchanged Pd-NaZSM5-116 was low as compared to under exchanged Pd-NaZSM5-80 and Pd-NaZSM5-58 samples. Close TOF's were found for the last two samples at 330°C. TOF differences in Pd-NaMordenite catalysts demonstrate the heterogeneity of Pd⁺² sites due to structurally nonidentical locations of cations. TOF's appear to be related to Na/Pd ratios in both catalyst types. Apparent activation energies for Pd-NaZSM-5 materials are higher than those for Pd-NaMordenite catalysts.     

改性5A分子筛对水中As(Ⅴ)的吸附作用研究

改性5A分子筛是一种高效吸附材料。实验用5A分子筛作为载体,制备了该吸附剂,并表征了其基本性质。结果表明,改性5A分子筛对As(Ⅴ)具有很高的吸附率和选择性;室温下,pH=7时,改性5A分子筛吸附As(Ⅴ)的吸附等温线符合Langmuir型和Freundlich型。     

Effect of the metal oxide loading on the activity of silica supported MoO3 and V2O5 catalysts in the selective partial oxidation of methane

Precipitated silica catalysts loaded with either MoO₃ (0.2–4.0 wt%) or V₂O₅ (0.2–5.3 wt%) have been studied in the selective partial oxidation of methane to formaldehyde with molecular oxygen at 520 °C. The functionality of the SiO₂ surface towards the formation of HCHO is significantly promoted by V₂O₅, while it is depressed by the MoO₃.