The effect of metal type and loading on n-paraffin hydrocracking conversion and selectivity

• Main Author: Wynne, Peter DT
• Other Authors: Böhringer, Walter
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2014
• Online Access: http://hdl.handle.net/11427/8702

Includes bibliographical references. === With the continued decline in global oil reserves, there is a growing need to develop alternative sources of conventional fuels to complement the current dependence on crude oil feedstocks. Natural gas, coal and biomass have been identified for this purpose. The distinctive advantage of using natural (stranded) gas is that it is turned into a useful product, thereby increasing its value and reducing the environmental impact of simply flaring it. The value-added work up of natural gas is effected by Gas-to-Liquid conversion via the Fischer-Tropsch Synthesis. Long-chain hydrocarbon waxes are produced and these are subsequently hydrocracked into the required middle distillate fuels, preferably diesel, as diesel engines are more efficient than their petrol counterparts. Hydrocracking may be carried out using a bifunctional catalyst, consisting of metal and acid components. Industrially, hydrocracking is used to crack heavy crude oil fractions into the desired fuel range, however, the catalysts used are sulphided transition metals. These are less suitable for cracking Fischer-Tropsch waxes as they would introduce sulphur into a clean feedstock. Moreover, at reaction temperatures of around 250°C, transition metal sulphide catalysts display little activity. Thus, one may consider noble metals such as palladium or platinum, whilst shape selective zeolites may be used as the acid component.