W. Grzegorczyk

A new preparation technique of catalysts characterized by small metal crystallites

The present study reports a new and original technique for obtaining nickel catalysts characterized by small metal crystallites. The catalysts were prepared on γ-Al2O3. The total surface of the carrier was 37.5 m2/g. The preservation of the appropriate procedure and conditions of preparation allow a large expansion of active nickel surface (mean crystallite size 2.0–3.0 nm) in spite of the quite hard conditions of reduction (773 K and 3 h).AbstractВ данном сообщении приводится новая и оригинальная техника получения никелевых катализаторов, характеризуемых малыми металлическими кристаллитами. Катализаторы были приготовлены на γ-Al2O3. Общая поверхность носителя равнялась 37,5 м2/г. Соблюдение подходящей процедуры и условий приготовления приводит к большому повышению активной поверхности (средние размеры кристаллита 2,0–3,0 нм) несмотря на относительно жесткие условия восстановления (3 часа при 773 К).

Resistance to Coking Determination by Temperature Programmed Reaction of n-Butane with Steam

Resistance to coking is one of the most important characteristics of nickel catalysts used for steam reforming of hydrocarbons, CO2 reforming or methanation of carbon oxides. Microbalance reactors have for a long time played an important role in catalyst deactivation studies, providing coking and coke gasification rates. However, conventional thermogravimetric microbalances have a number of limitations. The aim of this paper is to compare initial temperatures of coking of Ni and Ni-Mo catalysts (with different resistance to coking) obtained in the temperature-programmed reaction of n-butane with steam with the results of coking rates obtained by the traditional thermogravimetric method. The investigations showed great agreement of the results.

Determination of resistance to coking in the steam reforming of hydrocarbons

For a long time the microbalance reactor has played an important role in catalyst deactivation studies, but it has a number of limitations. The initial temperatures of coking of Ni and Ni-Mo catalysts in the temperature-programmed reaction (TPReaction) of n-butane with steam are compared with the results of coking rates obtained by the traditional thermogravimetric method. The investigations show good agreement of the results.

Promotion of nickel catalysts for the steam reforming of methane

The influence of additives (Cu, Fe and Al2O3) on the textural and catalytic properties of nickel in steam reforming of methane is described. The effects of structural promoting by Al2O3 and of electronic promoting by copper are reported. The rate of steam reforming of methane was measured in a gradientless reactor at atmospheric pressure.AbstractБыло исследовано влияние добавок (Cu, Fe и Al2O3) на структурные и каталитические свойства никеля в паровом крекинге метана. Были обнаружены эффекты структурного промотирования Al2O3 и электронного промотирования медью. Измерения скорости парового крекинга метана проводились в безградиентном реакторе при атмосферном давлении.

Effect of hydrogen sulfide on the activity of nickel catalysts for methanation

The resistance of 14 different nickel catalysts to H2S poisoning in CO2 methanation was examined. Experiments were carried out in a quartz reactor of special design, utilizing the methods of temperature difference measurement (DTA) and chromatographic analysis of outlet gases.AbstractУстойчивость 14 различных никелевых каталзаторов по отношению к отравлению H2S была исследована в метанировании CO2. Эксперименты проводились в кварцевом реакторе специальной конструкции, применяя метолы измения изменения температуры и хроматографического анализа газов на выходе.

Influence of added copper on the reduction and surface properties of nickel in Ni/γ-Al 2 O 3 catalysts

Influence of copper additive on the reduction of nickel catalysts and the active nickel surface were studied. The catalyst sample without added copper was prepared by precipitation from nickel and aluminium nitrates with ammonia. The reduction rate, the degree of nickel reduction and the active nickel surface referred to the amount of copper introduced into the system have been determined at 400 and 500 °C. The results confirm the existence and decisive influence of segregation phenomena in the Ni−Cu system on its properties.AbstractОцисывается влияние медных добавок на восстановление никелевых катализаторов и на величины активных поверхностей никеля. Образец катализатора без медных добавок был приготовлен методом высаждения из нитратов никеля и алюминия с помощью аммиака. Скорость восстановления, степень восстановления никеля и активная поверхность никеля находятся в зависимости от количества меди, вводимой в систему при 400 и 500°C. Было найдено, что эти результаты подтверждают присутсвие и влияние явлений сегрегации в системе типа Ni−Cu на ее свойства.

Studies of the molybdenum migration from Ni/Mo catalysts in the presence of steam

Abstract The extent of molybdenum loss was examined as a function of the initial Mo concentration in the Ni–Mo steam reforming catalysts and a partial pressure of water in the reaction mixtures. It was found that molybdenum loss at high temperature (∼800 °C) is prevented by the presence of even small content of hydrogen in the mixture. The kinetic equation describing the rate of Mo loss from the studied catalysts is presented. The possible application of Ni–Mo catalysts resistant to coking in the hydrocarbon steam reforming is discussed.