Crude oil and refinery streams desulphurization using slurry dispersed catalysts and ionic liquids (2011)

Petroleum refining is among the most important industries in the world. The oil refinery products contribute in many essential issues in the human life including transportation fuels, heating fuels, petrochemical industries, etc. Although oil refining is an old process started in the mid of the 19th century, new developments and technologies are introduced frequently due to the large amount of studies conducted around the world research centres. Some of the petroleum refining processes gain more attention in terms of research and development in the last couple of decades. For example, the importance of developing the hydrocracking process is increasing due to the increasing amount of heavy unconventional oil reserves. Another hot topic is the development of the hydrodesulphurization process due to the environmental concern about the sulphur oxides emissions produced by using oil refinery streams that contain several organic sulphur compounds. In this work, commercially available slurry catalyst precursors are tested to study the impact of the catalyst preparation conditions on its characteristic and activity. Those types of catalysts are used for hydrocracking and upgrading processes of heavy crude and residue including sulphur and other metal removal. The main subject was to approach the desulphurization activity and selectivity of the catalyst in removing dibenzothiophene (DBT) from model feed. DBT is one of the refractory sulphur compounds in the heavy oil fractions. It was found that changing the preparation conditions in terms of temperature, pressure and sulphiding agent influenced the activity and selectivity of the produced catalyst between the direct desulphurization reaction pathway and hydrogenation reaction pathway in removing DBT. The highest conversion was achieved by using cobalt-molybdenum-sulphide catalyst (Co-Mo-S) where up to 94.0 wt% of the DBT was converted. Adding the same catalyst precursor directly to Arab heavy crude oil, high desulphurization level was achieved where 70 wt% of the sulphur content of the feed has been removed. In addition, there is a high potential to increase this desulphurization level in treating heavy crude by applying the optimum operation conditions used in presulphiding the catalyst precursor. Ionic liquids (ILs) were also employed for sulphur removal from refinery streams by liquid-liquid extraction process. The ILs are organic salts with low melting points, mostly at room temperatures. Although the sulphur extraction level was very low comparing with the conventional hydrotreating process, this process has the advantage of minimizing the operation costs by reducing the reaction severity in terms of temperature and hydrogen consumption. Around 80 wt% of DBT was removed from model compound using one of the tested ILs. The nitrogen removal was also very high where almost 99 wt% of pyridine was removed from the model oil. However, the sulphur extraction level decreased in treating diesel fuel due to several factors such as the aromatic contents of the feed and the existence of several sulphur and metal compounds. To overcome this problem, the extraction process was repeated several times using fresh batches of ILs. This point has driven the importance of developing an efficient regeneration method for the used IL which was also approached in this work.