M. Marczewski

Acidity of sulfated oxides: Al2O3, TiO2 and SiO2. Application of test reactions

The acidic properties of different oxide/SO42− type superacids have been studied. Test reactions indicated that the acid strength of the Al2O3/SO42− system changed considerably with H2SO4 surface content notably −7.05 < H0 < −10 (1%), −10 < H0 < −14 (2–3%), H0 < −14 (4–9%), while for TiO2/SO42− preparations it was high and less dependent on catalyst composition: H0 < −14 (≥1%) and finally for SiO2/SO42− catalysts it was low with −0.75 < H0 < −3.50 (1–9%). Alkane isomerization over Al2O3/SO42− and TiO2/SO42− catalysts was observed to begin with the formation of an unsaturated intermediate state through the action of redox centres. Further alkene transformation into carbenium ion in the presence of Bronsted sites (Al2O3/SO42−) or secondary Bronsted centres (TiO2/SO42−) allows skeletal alkane isomerization to proceed.

Influence of sodium on the physico-chemical properties of oxides. Part I. Insulators — MgO, Al2O3 and SiO2

The effect of sodium on the surface properties of Al2O3, SiO2 and MgO was studied. Evaporation of sodium onto alumina and magnesia results in the formation of superbasic sites (H−≥35).AbstractБыло исследовано влияние натрия на поверхностные свойства Al2O3, SiO2 и MgO. Испарение натрия на поверхность окиси алюминия и окиси магния приводит к об-разованию суперосновных мест (H−≥35).

Superacid alumina catalysts II

The acidity and catalytic activity of alumina doped with AlCl3, CH3AlCl2, PCl5, PCl3, I2, Cl2 and H2PO3F were studied. Vapors of AlCl3 and CH3AlCl2 induce superacid sites in alumina, whereas PCl3 and PCl5 produce less acidic systems, which nevertheless catalyze the skeletal isomerization of alkenes. The modification of Al2O3 with other specified compounds affects only slightly the acidity and catalytic activity of alumina.AbstractИзучались кислотность и каталитическая активность окиси алюминия с добавками AlCl3, CH3AlCl2, PCl5, PCl3, I2, Cl2 и H3PO3F. Пары AlCl3 и CH3AlCl2 приводят к об-разованию сверхкислотных центров в алюминии. PCl3 и PCl5 создают менее кислот-ныи системы, все зе способные к катализу изомеризации алкенов. Модификашия Al2O3 другими веществами влияет лишь слабо на кислотность и каталитическую ак-тивность окиси алюминия.

Oxide catalysts for methane transformations in the absence of oxygen

The possibility of methane transformation to higher hydrocarbons in non-oxidizing atmosphere has been studied. It was found that in the presence of the MnOx−Na/SiO2-HZSM-5 catalytic system methane can be transformed into aromatics with a yield similar to that reported for oxidative coupling conditions.

“Superacid” alumina catalysts. Al2O3−P2O5 and Al2O3−AlCl3 catalysts for the isomerization and cracking of n-hexane

The effect of P2O5 and AlCl3 on the surface properties of alumina was studied. The sublimation of P2O5 and AlCl3 onto alumina surface results in the formation of superacid sites (H0≤−13.7) of the Lewis type, which catalyze the isomerization and cracking of n-hexane at 373 K.AbstractБыл исследован эффект P2O5 и AlCl3 на поверхностные свойства окиси алюминия. Было найдено, что сублимация P2O5 и AlCl3 на поверхность окиси алюминия приводит к образованию сверхкислотных центров (H0≤−13,7) типа Льюиса, которые способны катализировать превращения н-гексана (изомеризация и крекинг) при 373 К.

Alkylation of aromatics. Kinetics of phenol alkylation with methanol

A kinetic study of phenol alkylation with methanol in the presence of γ-Al2O3 has been carried out. A mechanism involving the reaction of phenol and methanol adsorbed on acid-base pair sites is proposed.

Catalytic and physico-chemical properties of Al2O3−H3PO4 system, II. Donor-acceptor properties

Donor-acceptor properties of catalysts containing different quantities of orthophosphoric acid on γ-alumina were studied. The decrease in N2O decomposition rate was found to be parallel with that of one-electron donor sites. Catalysts containing more than 0.4 mmol H3PO4/g Al2O3 exhibit individual surface properties due to the formation of an aluminium phosphate phase in the surface layer.AbstractИзучались донорно-акцепторные свойства катализаторов, содержащих разные колличества ортофосфорной кислоты на γ-Al2O3. Найдено, что скорость разложения N2O уменьшается параллельно к уменыпению количества одноэлектронных донорных центров. Катализаторы, содержащие бодее 0,4 ммоль H3PO4/г Al2O3 обнаруживают индивидуальные поверхностные свойства вследствие образования фазы фосфата алюминия в поверхностном слое.

Influence of sodium on the physico-chemical properties of oxides. Part II. Semiconductors — Cr2O3, TiO2, NiO and ZnO

The effect of sodium on the surface properties of Cr2O3, NiO, TiO2 and ZnO was studied. Sodium partly reduces the oxides of chromium, nickel, titanium and zinc and simultaneously induces new one-electron donor sites.AbstractБыло исследовано влияние натрия на поверхностные свойства Cr2O3, NiO, TiO2 и ZnO. Натрий частично восстанавливает окиси хрома, никеля, титана и цинка и одновременно индуцирует образование новух одноэлектронных донорных мест.

Catalysts for methane transformations into aromatics

The possibility of methane to aromatics transformation in non-oxidizing atmosphere has been studied. It was found that in the presence of the MnOx−Na/SiO2-HZSM-5 and CuO−FeO/HZSM-5 catalyst systems methane can be converted into aromatics with a yield depending on zeolite acidity.

Catalysts for methane transformation in the absence of oxygen, II. Nature of active centers

The activity of supported manganese oxide catalysts doped with copper, chromium and iron oxides in methane to higher hydrocarbons transformation in non-oxidizing atmosphere has been studied. Chromium and iron oxides are more effective promoters than copper oxide. Redox centers of dehydrogenation ability are active in methane transformations.