Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

Catalysis Letters - We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the...     

Selectivity Enhancement to the Exclusive Formation of Ethyltoluenes and Hydrogen During Dehydroalkylation of Toluene with Ethane

The dehydroalkylation of toluene with ethane to the isomeric ethyltoluenes was studied on 0.4Pt/H-ZSM-5 at varying contact times (1/WHSV). At a high contact time of 1.0 h, toluene disproportionation and hydrogenolysis reactions dominate, resulting in low selectivity to the desired ethyltoluenes via the alkylation reaction. However, at a low contact time of 0.12 h side reactions are eliminated, resulting in maximum selectivities to the kinetically favored ethyltoluenes and hydrogen. Results at high selectivities to ethyltoluenes provide significant insight into reaction pathways.     

The Ensemble Effect in Bifunctional Catalysis: Influence of Zinc as Promoter for Pd-H-ZSM-5 Catalysts during the Dehydroalkylation of Toluene with Ethane

The ensemble effect, i.e., the fact that the reaction requiring the largest ensemble of surface metal atoms will be most sensitive to promoting with a second metal, has rarely been studied in bifunctional catalysis. In this contribution, it is shown that, during the dehydroalkylation of toluene with ethane on Pd-H-ZSM-5 catalysts with zinc as promoter, the ensemble effect has only an influence on the side reactions on the metal such as hydrogenolysis, but not on the desired acid-catalyzed alkylation reaction.     

A dual 4-bit 2-Gs/s full Nyquist analog-to-digital converter usinga 70-ps silicon bipolar technology with borosenic-poly process andcoupling-base implant

A dual 4-b analog-to-digital converter (ADC) with Nyquist operation to 2 gigasamples/second (Gs/s) and -29-dBc distortion at 1 GHz is presented. A novel evaluation method using an integral digital-to-analog converter is introduced. A trench-isolated, self-aligned, double-polysilicon bipolar process is used for the chip fabrication. This ADC has a resolution of 3.73 effective bits at 1-GHz analog input signal, without the use of a preceding sample-and-hold. Low-frequency untrimmed distortion is -48 dBc (not including quantizing error), and is independent of the sample rate of 2 Gs/s     

Aromaten: Von wertvollen Basischemikalien zu Überschusskomponenten?

Aromatics: From Valuable Base Chemicals to Surplus Components? With the advent of the second stage of the European Auto Oil Programme in the year 2005, the aromatics content of gasoline has to be reduced significantly, which could lead to an oversupply of aromatics. The sources of aromatic hydrocarbons and their petrochemical use are described. Options for avoiding a surplus of aromatics are discussed, i.e., diminishing the production of aromatics and intensifying their conversion into valuable products. Finally, a novel catalytic process for hydrogenative ring opening of aromatics is introduced which allows the conversion of pyrolysis gasoline from naphtha steamcrackers into a high‐quality synthetic steamcracker feedstock composed of ethane, propane, and n‐butane. There are two process variants, namely the direct conversion of aromatics on bifunctional zeolites or a two‐stage process comprising a conventional ring hydrogenation to cycloalkanes followed by ring opening of the latter on acidic zeolites.     

Direct Proof of Volatile and Adsorbed Hydrocarbons on Solid Catalysts by Complementary NMR Methods

In this paper, both volatile and strongly adsorbed products of heavy hydrocarbon conversion on a zeolite were investigated by gas-phase and solid-state NMR. For this purpose, the reactions were carried out in sealed glass tubes under vacuum to collect the volatile reaction products. This procedure is demonstrated for pure 2-ethylphenol conversion on ultra-stabilized zeolite Y leading to both the formation of light alkanes and deoxygenation products. The above-mentioned method is useful to improve the understanding of heavy hydrocarbon conversion under batch conditions.