Controllably synthesized hydrophobic/oleophilic MOF for improving the efficiency of in situ low-temperature catalytic pyrolysis of heavy oil

In-situ catalytic technology for heavy oil reservoirs has attracted much attention in recent years and shows great potential for efficient exploitation. However, the existing catalysts still have deficiencies in catalytic activity, stability and dispersion in the formation, which restricts their large-scale application. This study introduces a Fe-based MOF modified by oleic acid (OA), which was controllably synthesized into a highly efficient and stable hydrophobic/oleophilic Fe/MOF-OA catalyst. Under the relatively low original formation temperature of 140℃, the viscosity reduction rate of heavy oil can reach 86.5% by using 0.5   wt% catalyst and 1   wt% hydrogen donor, and the asphaltene content can be reduced by 13.82%. Comparing the experiments with and without stirring, results show that the MOF catalyst modified by OA can be better dispersed in heavy oil and achieve stable migration under reservoir conditions. The water contact angle and stability analysis tests confirm the good hydrophobic/oleophilic properties and stability of the OA-modified catalyst. Mechanism analysis shows that after modification by OA, the long-chain alkanes significantly enhance the hydrophobic/oleophilic property of the catalyst, allowing it to fully contact with heavy oil and maximize the catalytic performance of the catalyst. More importantly, this oleophilic catalyst can achieve effective migration and distribution under the spontaneous disturbances in the oil reservoir, avoiding the agglomeration and deactivation of traditional catalysts due to their inability to disperse under formation conditions. Secondly, the grafting of OA long chains can fine-tune the electronic environment of the Fe metal active center, enhance their ability to accept the lone pairs of electrons from heteroatoms in heavy oil components, promote the occurrence of deheteroatomization reactions, and lead to the cleavage of C-S, C-N, and C-O chemical bonds. In addition, compared with traditional in-situ thermal cracking catalysts for heavy oil, Fe/MOF-OA has more outstanding performance in use and economic advantages. This study provides an important theoretical basis and practical strategies for the design of in-situ catalysts for heavy oil. It demonstrates the great application potential of oleophilic MOF in the pyrolysis and upgrading heavy oil.