Enhancing Vacuum Residue Production by Using Different Kaolin Geopolymer Catalysts

This study explores the potential of vacuum residue (VR) as an unconventional and renewable source of global transportation fuel. The primary aim is to investigate the cracking of Iraqi VR using an economically feasible and environmentally friendly geopolymer catalyst. Two types of metakaolin, red (designated G1) and white (designated G2), were mixed with alkaline activators to synthesize geopolymers with a hierarchically porous structure (containing interconnected pores of varying sizes). Following synthesis, the geopolymers were subjected to activation through hydrochloric acid (HCl) treatment. Finally, thermal treatment at 750°C for 2 h was applied to the geopolymer powders. This process yielded red kaolin-based geopolymer G1* and white kaolin-based geopolymer G2*. The extensively characterized using various techniques including XRF, XRD, FE-SEM, FTIR, and BET. Significant differences in Si/Al ratios and iron content were observed between the red and white geopolymers. The white geopolymer showed annite-1M phase, while the red geopolymer showed the existence of a zeolite phase, according to XRD analysis. Further investigation using an FE-SEM revealed that both materials had uniformly distributed, different amorphous morphologies. BET analysis subsequently revealed significant differences in surface area between the red geopolymers (60.89 m2/g) and white geopolymers (19.42 m2/g). Cracking the vacuum residual involved utilizing a geopolymer catalyst within a fixed-bed reactor. The resulting hydrocarbon liquid product, collected to a volume of 17 mL, underwent analysis using Gas Chromatography-Mass Spectrometry (GC-MS). The analytical results obtained from GC-MS provide strong evidence for the effectiveness of the white geopolymer catalyst in the conversion of vacuum residue and producing light petroleum fractions. Notably, the white geopolymer catalysts generated 47% more gasoline products than the 30% yield achieved with red geopolymer catalysts. The vacuum residue obtained from the Al-Doura petroleum refinery in Baghdad, Iraq, exhibited a waxy texture, and black color, and contained heavy hydrocarbons with high molecular weights. This residue is known as Doura Vacuum Residue (VR). Interestingly, the red geopolymer catalysts produced gasoline products of higher quality.