Oil removal from spent HDT catalyst by an aqueous method with assistance of ultrasound

Advancing total management of oily spent hydroprocessing catalyst: From hazardous waste to circular and eco-sustainable utilization

Hydroprocessing technology is essential for refining crude oil, playing a critical role in improving oil quality. This process consumes large quantities of catalysts, which become spent hydroprocessing catalysts because of deactivation. These spent catalysts, containing substantial amounts of residual oil, coke, and heavy metals, are recognized as challenging hazardous solid waste. However, they also contain critical rare metals and crude oil, making them an important and valuable secondary resource. Managing these ever-growing volumes of spent catalysts to ensure safe disposal of hazardous waste while maximizing circular and eco-sustainable utilization has become a pressing global challenge and key research focus. Therefore, this paper provides a comprehensive review of popular technologies and recent advancements in managing oily spent hydroprocessing catalysts, aiming to achieve the dual goals of environmental protection and maximizing resource utilization. This review first introduces the types and functions of hydroprocessing technology and catalysts and explores the causes and hazards associated with deactivating hydroprocessing catalysts. It thoroughly discusses popular and innovative emerging technologies in deoiling, regeneration, high-value reuse, and recovery metals from spent catalysts, highlighting the strengths and challenges of each method. The review concludes with outlook on future directions, proposing directions and considerations for advancing total management of oily spent hydroprocessing catalyst.

Highly efficient recovery of total components from spent hydroprocessing catalysts (HPCs) with minimal CO2 & SO2 emissions

It is imperative to recover the valuable components of spent HPCs. We have proposed a hydrometallurgical process and recovered 99.9% of V, 99.9% of Mo, and 95% of Al in our previous work. In this study, we focused on the Co and Ni recovery from the alkaline leaching residue of spent HPCs. We characterized the leaching residue by SEM-EDS, XPS, TGA, Laser Particle Size Analyzer, and ICP-OES. The Ni and Co leaching rates both reached around 95% with 2.0 mol/L H2SO4 at 120 °C for 75 min. The impurity of Al in the leachate was removed via solvent extraction with 30% P204 at A/O of 1 and pHequilibrium of 2.0. The Co and Ni in the raffinate was separated via two stages of counter-current extraction with 20% Cyanex 272 at A/O of 1 and pHequilibrium of 5.7. The CoSO4 and NiO products were characterized by XRD, and there are no impurity peaks. We also did DFT calculations, which show the binding energies of Al3+ with extractants are in the order of Al3+-P204 > Al3+-P507 > Al3+-Cyanex 272, and Cyanex 272 exhibits the highest difference in binding energies of Ni2+ and Co2+. The process of Ni and Co recovery from the alkaline leaching residue of spent HPCs was proposed. Only 8 t CO2 and 120 kg SO2 emissions were generated during all the component recovery per ton of the spent HPCs using our proposed process. They are much less than pyro-hydrometallurgical processes.

Mechanism of highly efficient oil removal from spent hydrodesulfurization catalysts by ultrasound-assisted surfactant cleaning methods

The removal of crude oil from spent hydrodesulfurization catalysts constitutes the preliminary stage in the recovery process of valuable metals. However, the traditional roasting method for the removal exhibits massive limitations. In view of this, the present study used an ultrasound-assisted surfactant cleaning method to remove crude oil from spent hydrodesulfurization catalysts, which demonstrated effectiveness. Furthermore, the study investigated the mechanism governing the process with calculation and experiments, so as to provide a comprehensive understanding of the cleaning method's efficacy. The surfactant selection was predicated on the performance in the IFT test, with SDBS and TX-100 finally being chosen. Subsequent calculations and analysis were then conducted to elucidate their frontier molecular orbitals, electrostatic potential, and polarity. It has been found that both SDBS and TX-100 possess the smallest LUMO-HOMO energy gap (ΔE), registering at 4.91 eV and 4.80 eV, respectively, and presenting the highest interfacial reactivity. The hydrophilic structure in the surfactant regulates the wettability of the oil-water interface, and the long-chain alkanes have excellent non-polar properties that promote the dissolution of crude oil. The ultrasonic-assisted process further improves the interface properties and enhances the oil removal effect. Surprisingly, the crude oil residue was reduced to 0.25% under optimal conditions. The final phase entailed the techno-economic evaluation of the entire process, revealing that, in comparison to the roasting method, this process saves $0.38 per kilogram of spent HDS catalyst, with the advantages of operational simplicity and emission-free. Generally, this study shed new light on the realization of efficient oil removal, with the salience of green, sustainable, and economical.

Self-circulation of oily spent hydrodesulphurization (HDS) catalyst by catalytic pyrolysis for high quality oil recovery

In this study, roasted spent HDS ash (sHDSc-A) was used for the first time to catalytically pyrolyze oily spent HDS catalysts (sHDSc) to improve the yield and quality of pyrolysis oil. The results showed that sHDSc-A promoted the decomposition of coke in oily sHDSc, resulting in the recovery of more oil and gas. Meanwhile, sHDSc-A significantly improved the quality of the pyrolysis oil. They inhibited the aromatization of alkanes to increase the saturation of the pyrolysis oil from 59.39% to 74.25% and the H/C radio from 1.62 to 1.72; promoted the decomposition of long-chain alkanes to increase the content of C11-C22 from 41.97% to 61.99%; enhanced the conversion of carboxylic acids to ketones led to the reduction of heteroatomic compounds such as N (56.10%-45.39%), S (66.95%-56.59%), and O (45.26%-26.70%) in the pyrolysis oil. The promotion of sHDSc-A in the pyrolysis process is attributed to the catalytic effect of the metal oxides in sHDSc-A. Among them, Al₂O₃ and Fe₂O₃ can promote decarboxylation of carboxylic acids and reduce O mobility, while MoO₃ and Fe₂O₃ play a significant role in reducing coke and increasing pyrolysis oil. NiO can also promote methane vapor reforming, and thus increase the production of H₂ in non-condensable gas. This study achieves self-circulation of oily sHDSc with a "waste-treatment-waste" strategy that presents the advantage of value-added energy recovery and waste reuse.

Generation behavior of extracellular polymeric substances and its correlation with extraction efficiency of valuable metals and change of process parameters during bioleaching of spent petroleum catalyst

The vital functions of extracellular polymeric substances (EPS) have been well recognized in bioleaching of sulfide ores. However, no report is available about the role of EPS in bioleaching of spent catalyst. To completely and deeply understand the functions of EPS in bioleaching of spent catalyst, the generation behavior of EPS at various pulp densities during bioleaching was characterized by three-dimensional excitation-emission matrix (3DEEM), and its relevance with bioleaching performance and process parameters were analyzed using mathematical means. The results showed that the EPS contain humus-like substances as main component (>70%) and protein-like substances as minor component (<30%). Both total EPS and humus-like substances mainly keep growing over the whole duration of bioleaching at low pulp density of 5.0% or lower; whereas total EPS and humus-like fraction keep declining at high pulp density of 7.5% or higher. Among the total EPS and its components, humus-like substances only have a positive significant correlation with bioleaching efficiencies of both Co and Mo and affect bioleaching process more greatly due to greater correlation coefficient. Biofilm appears at the spent catalyst surface under 2.5% of pulp density mediated by EPS while no biofilm occurs at 10% of pulp density due to shortage of EPS, accounting for the great difference in bioleaching efficiencies between high and low pulp densities which are 48.3% for Mo and 50.0% for Co at 10% of pulp density as well as 75.9% for Mo and 78.8% for Co at 2.5% of pulp density, respectively.