Influence of catalysts on the pyrolysis of lignites

In this work the advantages of direct conversion of lignite with zeolite catalysts under inert conditions are shown. The main desired products were low chain hydrocarbons with high added value like olefins and aromatics. The yield of the desired products depends on the used lignite catalyst system. One main factor is the hydrogen content of the lignite and the amount of volatile matter, respectively. For one system yields of 12% propene and butenes were observed. Another main factor is the temperature of the process. Optimal conditions were found at about 500 °C with one specified system. To reduce the tar yield, a high catalyst to lignite ration seems to be suitable. It was considered that this is due to enhanced contact time between the lignite and the catalyst as well as the contact time between tar and the catalyst. Based on additional differential thermal analysis (DTA) fractional coupled with ir and tar analysis a model was proposed for the reaction system.