Hydrocracking is the technically most flexible and the most expensive conversion process in terms of investment and operating costs. This is a catalytic cracking process with the addition of hydrogen at a pressure of 100 to 150 bar, which allows very extensive conversion of the feedstock. Low-boiling gasolines contain a larger number of hydrogen atoms per carbon atom than high-boiling hydrocarbons such as heavy oils. If larger proportions of the heavy oil are to be converted into low-boiling gasolines, then hydrogen must be added to the molecular fragments formed at the same time as the cracking process. This requires increased hydrogen input under high pressure. The process involves passing the preheated feedstock with hydrogen through one or more reactors, in which hydrogenative cracking takes place with the aid of nickel-molybdenum catalysts. The liquid and gaseous products are then separated from the gaseous products and the residual hydrogen is returned to the beginning of the process together with the fresh hydrogen.
Hydrocracking has the advantage that, depending on the catalyst and operating conditions, the desired yield of gasoline, diesel fuel and light heating oil can be achieved. The disadvantages are the high hydrogen requirement and the high pressure. Reactors that can cope with these requirements cause high costs. Therefore, the supply of the hydrocracker with hydrogen usually requires the construction of a separate hydrogen production plant.
Olefins are unsaturated compounds, the names of these compounds end on -ene, such as ethylene or propylene, butylene, butadiene and so on. Compared to paraffins, olefins are unstable and like to react with themselves or other compounds such as oxygen or bromine solution. Olefins are produced through processing feeds via thermal steam cracking or fluid catalytic cracking.
Ethylene and propylene are key intermediate and feedstock for production of polyethylene (PE), polypropylene (PP), mono-ethylene glycol (MEG), polyvinylchloride, styerene and much more.
Industrial hydrodesulfurisation unit reaction in a fixed bed reactor takes place at temperature level of 300 up to 400° C and at pressure ranges from 30 up to 130 bars. There is a catalyst with alumina impregnated cobalt and molybdenium present in this process. Sulfur content is reduced from hydrocarbon fuels such that low sulfur Diesel, ultra low sulfur Diesel and other low sulfur transportation fuels are produced. Compressor duty is bringing feed Hydrogen gas to starting process conditons. And further keep recycle loop on pressure level.
Another important catalytic refining process is reforming. The raw gasoline from atmospheric distillation has an octane rating of 40 to 60, hence a too low a knock resistance to be used for the production of gasoline. Therefore, the goal in reforming is to increase the octane number of gasoline OZ >91. The following reactions occur during reforming:
In catalytic reforming, a platinum catalyst is used to increase the molecular structures of the crude gasoline to the octane number of 95 to 100. This process produces iso-paraffins from straight-chain kerosenes and, to a greater extent, aromatics and hydrogen from ring-shaped kerosenes (naphthenes). The reforming process takes place at temperatures of 490 to 540 °C. The reforming process itself is endothermic, which means that energy has to be constantly supplied via must be supplied via heat exchangers. As a welcome by-product, hydrogen is also produced during reforming, which can be used in other plant components of the refinery network such as desulphurization or hydrocrackers.
The Gas-to-Liquid technology is mainly a three-step process. As a starting point there is an air separation unit to produce oxygen. In a reformer natural gas with oxygen and steam over a catalyst will produce a syngas. Converting the syngas into long chain wax hydrocarbons is done in a Fischer -Tropsch (FT) reactor. Last step is to crack the hydrocarbons into liquids like diesel, kerosene or naphta which are used as environmentalfriendly synthetic fuels.
Isomerization in petrochemistry involves changing the atomic sequence or arrangement of a saturated hydrocarbon is changed to a different isomer, but with retention of its molecular mass. The content of high-octane aromatic components in fuels is limited by legislation, but modern engines require a higher fuel quality. The aim of isomerization is therefore to increase the octane number of n-alkanes. Bifunctional catalysts are used in the isomerization of light gasoline with the components n-pentane and n-hexane, which have both acidic and hydrogenation-active metallic platinum or palladium centers. To avoid cracking and coking reactions, the process is often carried out under hydrogen pressure. Resulting olefins are thereby hydrogenated back to the alkane.