The hydrocarbons which are easy to reform into hydrogen are hydrocarbons with a chain length of less than six carbon atoms. A new catalyst system which was jointly developed by the group at the University of Stuttgart and Veba Oel opens up a novel route for production of mainly a n-paraffin feedstock with a chain length of less than six carbon atoms from a feed with a high aromatic content.
The ratio between aromatic and paraffin compounds in the feed, controls the outlet temperature of the reactor. The aromatics are converted by hydrocracking. The enthalpy of this step is only used as the energy source, for the hydrocracking process including the evaporation of the feed. The aromatics which tend to create problems in the usual steam reforming reaction, are the energy source in this process for the evaporation of the liquid fuel. The crack reactor does not need any external heat and the outlet temperature at around 400°C is controlled by the ratio between aromatic and paraffin compounds in the fuel itself.
The hydrocrack product can now be easily converted into hydrogen by the use of a membrane reactor concept. The application of high pressure and a high hydrogen partial pressure enables the use of membranes with a Pd layer of less than 10 μm thick. This membrane was developed by our partner Creavis. In comparison to conventional membrane process, this new route provides an economical benefit in terms of Pd content and exchange area. The pressure for the process is mainly produced by liquid pumps, this is also a great advantage in comparison to conventional partial oxidation for fuel cell systems.
With the advent of the European Auto Oil Programme in 2005, the content of aromatics in gasoline will have to be reduced from 42 vol.-% to less than 35 vol.-%. Comparable or even more stringent legislation exists or will be implemented in other parts of the world, for example in California the aromatics content of gasoline is limited to 22 vol.-%. The problem with aromatics in gasoline is that the exhaust gas of internal combustion engines may contain small amounts of aromatics. On the other hand, the high octane numbers of aromatics are very beneficial. Using other components as octane boosters, e.g., methyl-tert.-butyl ether (MTBE), brings about other problems. A potential way out of all these problems is a switch to diesel engines which, however, inevitably leads into the problem of particulate emission. The ultimate solution for all these environmental problems is often seen in the fuel cell technology.
Upon limiting the aromatics content of gasoline and introducing the fuel cell tech
