Procédé Bergius

The Bergius process is a method of production of liquid hydrocarbons for use as synthetic fuel by hydrogenation of high-volatile bituminous coal at high temperature and pressure. It was first developed by Friedrich Bergius in 1913. In 1931 Bergius was awarded the Nobel Prize in Chemistry for his development of high-pressure chemistry. The coal is finely ground and dried in a stream of hot gas. The dry product is mixed with heavy oil recycled from the process. A catalyst is typically added to the mixture. A number of catalysts have been developed over the years, including tungsten or molybdenum disulfide, tin or nickel oleate, and others. Alternatively, iron sulfide present in the coal may have sufficient catalytic activity for the process, which was the original Bergius process. The mixture is pumped into a reactor. The reaction occurs at between 400 and 500 °C and 20 to 70 MPa hydrogen pressure. The reaction produces heavy oils, middle oils, gasoline, and gases. The overall reaction can be summarized as follows: (where x = Degrees of Unsaturation) The immediate product from the reactor must be stabilized by passing it over a conventional hydrotreating catalyst. The product stream is high in cycloalkanes and aromatics, low in alkanes (paraffins) and very low in alkenes (olefins). The different fractions can be passed to further processing (cracking, reforming) to output synthetic fuel of desirable quality. If passed through a process such as platforming, most of the cycloalkanes are converted to aromatics and the recovered hydrogen recycled to the process. The liquid product from Platforming will contain over 75% aromatics and has a Research Octane Number (RON) of over 105. Overall, about 97% of input carbon fed directly to the process can be converted into synthetic fuel. However, any carbon used in generating hydrogen will be lost as carbon dioxide, so reducing the overall carbon efficiency of the process. There is a residue of unreactive tarry compounds mixed with ash from the coal and catalyst.