فهرست نشریات علمی دسترسی آزاد ایران

This study discusses the mechanism and review of studies on the synthesis of nickel-lanthanum catalysts. Catalytic cracking has been identified as a reliable alternative route for the production of light olefins. Although this process is still in the development stage, the results show that catalytic cracking has more advantages than thermal cracking, the most important of which are higher production of ethylene and propylene, lower emissions of greenhouse gases, significant energy savings, and the ability to reduce heavy off-products. In addition, the catalytic cracking process can selectively change the production of light olefins by the type of catalyst. The use of metal oxides such as CaO, Al2O3, SrO, MgO, TiO2, MnO2, Mn2O3, ZrO2, K2O, and I2O3 for light olefin production has been investigated since 1960. Depending on the feed type and reaction conditions, selectivities ranging from 24 to 40 wt% for ethylene and 18 to 22 wt% for propylene have been achieved over metal oxide catalysts. Calcium aluminate (12CaO - 7Al2O3) saturated with K2Co3 and potassium vanadate KVO3 on alumina increased the selectivity of light olefins. Compared with the thermal steam cracking process, the selectivity of ethylene production from naphtha increased by 5 to 10 wt% in the temperature range of 770 to 820 °C. However, despite the use of catalysts, the reaction temperature did not decrease significantly and the higher selectivity of ethylene production was probably not due to catalytic ethylene production. This increase was probably due to the better heat transfer process and the increased rate of coke and heavy hydrocarbons to gas conversion reactions, such that in this reaction, CO and gases were produced by 5 to 20 wt%. The presence of some defects, including catalyst deactivation at high temperatures, high steam consumption, and coke production, made the energy selectivity of this type of catalyst high.