Reduction of NO by C1-C4 hydrocarbons at cobalt-containing zeolites

Data are given on the activity of high-silicon zeolites in the reduction of nitrogen oxides by methane and C₂-C₄ hydrocarbons (paraffins and olefins). It was shown that the highest degree of conversion of NO during selective catalytic reduction is obtained at the mixed forms of Co-containing zeolites at temperatures 100°C lower than at the usual Co-containing zeolites of the ZSM-5 type.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 1, pp. 47–50, January–February, 1996. Original article submitted April 3, 1995.     

Selective reduction of nitrogen oxides by C3-C4 hydrocarbons on metal zeolite catalysts

A study was carried out on the activity of high silicon cation-exchanged zeolites containing Period IV metals (Fe, Cu, Zn, and Co) and lanthanides (La and Ce) in the reduction of nitrogen oxides by C₃-C₄ hydrocarbons in an oxidizing atmosphere and the kinetics of this process for the copper and cerium catalysts, which display the highest activity. The catalyst activity is a function of the nature of the cation introduced, extent of exchange of sodium by the corresponding cation, SiO₂/Al₂O₃ ratio of the zeolite, and acidity of the catalyst surface.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 6, pp. 350–354, November–December, 1994.     

The adsorption and localization of mixtures of C4-C7 alkane isomers in zeolites by computer simulation

Grand canonical Monte Carlo and configurational-bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of C(4)-C(7) alkane isomers in ISV and MOR zeolites at 300 K, and the results were compared to that in MFI. Unlike in MFI, the amount of adsorption of the linear and branched alkanes all increases with pressure increasing in ISV and MOR for 0.5-0.5 gas-phase mixtures. The location of alkane isomers is astatic, and it does not exhibit obvious orientation in ISV and MOR. The interaction energy of 2-methylpropane-zeolite is obviously higher than that of n-butane-zeolite in MFI. As to ISV and MOR, the interaction energy between 2-methylpropane and zeolite is a little lower than that between n-butane and zeolite. It can be found that the zeolite MFI behaves quite differently in adsorption from ISV and MOR.     

Methanol conversion of various cation-exchanged forms of high-silica zeolites

Studies of the methanol conversion on various cation-exchanged forms of high-silica zeolites have revealed that the activity and selectivity of the intact pore structure zeolites depend on the cation composition. On decationated forms the selectivity of methanol conversion to aromatic hydrocarbons is much higher than on the hydrogen form, and it decreases with respect to paraffins.

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C1-C4在Pt 催化剂上的多相反应机理

提出并构建了H2和C1-C4碳氢燃料在Pt表面上的详细催化反应机理, 对所构建的机理分别用CH4、C2H6、C3H8以及C4H10等碳氢燃料进行了数值模拟; 并用文献中给定的部分碳氢燃料(如CH4、C2H6 加H2与不加H2, C3H8加H2与不加H2, 以及C4H10加H2)的催化着火与燃烧的实验结果与数值模拟结果进行了对比, 对比结果表明H2会对C3H8以及C4H10的催化起燃以及C2H6的催化燃烧起促进作用, 但所起作用的动力学过程并不是相同的. 此机理能够有效地反映上述燃料的主要催化着火以及催化燃烧特征, 并可以对着火与燃烧整个过程进行动力学分析, 用其来描述C1-C4碳氢燃料的催化着火与燃烧具有一定的合理性.     

Effect of SO2 on the selective reduction of NO by C3 and C4 hydrocarbons on a zeolite containing cerium

Sodium dioxide can accelerate the reduction of NO by hydrocarbons on a Ce-VN zeolite. Acceleration of reduction probably results from formation of hydrogen sulfide which is a more effective reducing agent for NO than hydrocarbons are.L. V. Pisarzhevskii Institute of Physical Chemistry, Ukrainian Academy of Sciences, Ukraine, 252439 Kiev, Science Prosp., 31. Translated from Teoreticheskiya i Épsperimental'naya Khimii, Vol. 32, No. 4, pp. 255–257, July–August, 1996. Original article submitted September 14, 1995.     

Selective catalytic reduction of nitrogen oxides by C1 C3, and C4 hydrocarbons

Data are given on the activity of catalysts containing polyvalent metals in the reduction of nitrogen monoxide by hydrocarbons (CH₄, C₃H₈-C₄H₁₀, C₃H₆) in excess oxygen. It was established that the catalysts H-mordenite and CeO₂-TiO₂ have the highest activity.Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 29, No. 1, pp. 92–94, January–February, 1993.     

整体式Pt基催化剂上CH4选择性催化还原NO的研究

以La-Al2O3(La稳定的γ-Al2O3)、Ce0.63Zr0.37O2(OSM1)及Ce0.5Zr0.3Mn0.2O2(OSM2)为载体, Pt为活性组分, 制备了Pt质量分数为1%的整体式催化剂. 研究了不同载体负载的催化剂对CH4选择催化还原NO反应的性能, 并利用XRD、H2-TPR和XPS对催化剂进行了表征. 结果表明, Pt/OSM1和Pt/OSM2催化剂在氧含量为0.8%时对CH4催化还原NO具有优异的净化性能, Pt/OSM1催化剂上500 ℃时, CH4和NO均达到100%转化; Pt/OSM2催化剂上500 ℃时, CH4和NO的转化率分别达到73%和100%; 而 Pt/ La-Al2O3催化剂只在O2含量较低时(0.4%以下)具有较好活性, 500 ℃以上才可使CH4和NO完全转化. H2-TPR结果表明, Pt与OSM1和OSM2存在的相互作用导致低温还原物相生成. Pt与OSM的相互作用及OSM的储氧性能使催化剂在过量氧存在下对CH4催化还原NO具有优异性能.     

First direct observation of reactive carbenes in the cavities of cation-exchanged Y zeolites

[reaction: see text] Herein we report the first direct observation of reactive carbenes within the cavities of cation-exchanged Y zeolites. Chloro(phenyl)- and bromo(phenyl)carbenes were generated upon laser photolysis of 3-halo-3-phenyldiazirines incorporated within dry zeolites and the absolute reactivity of the carbenes was investigated as a function of counterbalancing cation and coincorporated quenchers in order to elucidate the behavior of these intermediates within zeolites. Product analysis performed upon thermolysis of the diazirine in Y zeolites yielded products that were identified as those derived from the carbene.     

Methanol-based synthesis of hydrocarbons on bifunctional Y-type zeolites

The directions of methanol conversion on Pt, Pd, Zn, Ni metals and Y zeolites and on bifunctional metal-Y-zeolite catalysts have been studied. The increase of the hydrogenation activity of bifunctional catalysts enhances the rate of methanol conversion and decreases the selectivity of hydrocarbon formation.

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Transformations of aromatic hydrocarbons over zeolites

Aromatic hydrocarbons represent an important group of starting materials, intermediates, as well as final products produced in the chemical industry in the range from large processes in petrochemistry up to the synthesis of fine chemicals. This short overview covers the recent achievements in acid-catalyzed transformations of aromatic hydrocarbons with a special focus on alkylation-isomerization-disproportionation reactions in petrochemistry, and acylations or condensations used mainly in synthesis of chemical specialties. In the case of fine chemical synthesis, some zeolite applications in the preparation of important intermediates for pharmaceutical or fragrance products are presented. Advantages and disadvantages of the various types of zeolite are discussed in these reactions from the point of view of their (shape) selective properties, as well as the accessibility of acid sites.     

Stereoselective synthesis of C1-C5 and C4-C5 linked deoxy disaccharides via a ring closing metathesis protocol

The stereoselective synthesis of C-C linked deoxy disaccharides by a short and efficient route is described. An RCM strategy was adopted for the assembly of the required ring skeleton on the sugar unit, while OsO₄ was used to introduce the vic-diol unit.