Waste Lube Oil Research Articles

A comparative study on treatment for recycling of waste lubricating oil

In the present work, the recycling of waste lubricating oil by treatment was investigated using three types of acids such as nitric acid, hydrochloric acid, and sulphuric acid. This research aims to gain a high-quality refined lubricant oil using acid as an alternative to distillation process. The characteristics and quality of the treated lubricating oil were compared with the base oil by several parameters such as pour point, cloud point, dynamic viscosity, kinematic viscosity specific gravity and ash content, following American Society for Testing and Materials (ASTM) standards. Initially, filtration was employed to remove the dirt that may be present in the used lubricant oil, followed by adding gasoline to the used lubricating oil and centrifugation at 1500 rpm for 10 minutes. The atmospheric distillation was conducted for complete removal of water and gasoline. Finally, the lubricating oil was treated with the acids (nitric acid, hydrochloric acid, or sulphuric acid) and neutralised with 6% sodium hydroxide before being separated using settling and centrifugation. Results showed that sulphuric acid exceeds nitric acid and hydrochloric acid in treating the waste lubricating oil. Furthermore, treated waste lube oil using 20% sulphuric acid was comparable to the fresh lubricating oil. The results showed that the waste lube oil after acid treatment can be reused.

Fabrication of CoNiMo/γ-Al2O3 from waste aluminum foil to convert waste lube oil to hydrotreated oil

Because of the heavy metal content and other toxic chemicals, used lubricating oil remains one of the most serious environmental concerns. The target of this work is the synthesis of γ-Al2O3 from waste aluminum foil and re-refining waste lubricating oils using solvent extraction pursued by hydrotreatment. The trimetallic CoNiMo/γ-Al2O3 catalyst was prepared via a co-impregnation method. The support and tri-metallic supported alumina are characterized by N2 adsorption–desorption techniques, X-ray diffraction (XRD), Raman spectroscopy, HRTEM, and EDX. The catalyst was evaluated in the hydrotreating of extracted waste lubricating oils. The results confirmed that the solvent to oil ratio of 3 gave the higher performance with the highest percent of sludge elimination at room temperature. Hydrotreating of extracted lube oil was investigated to determine the effect of variables such as temperature, pressure, liquid hour space velocity, and hydrogen to oil feed ratio. The results indicated that the optimum conditions are (temperature 400 °C, Pressure 60 bar, 0.75 h−1 LHSV). The results showed improvement of the hydrotreated waste lubricating oils properties by decreasing the refractive index from 1.480 to 1.460, the total acid number decreased from 8.164 to 0. 459, the Viscosity Index increase from 78 to 129, and the Sulfur content decreased from 6752 ppm to 543 ppm.

Refining and Reuse of Waste Lube Oil in SI Engines: A Novel Approach for a Sustainable Environment

The protection of the environment and pollution control are issues of paramount importance. Researchers today are engrossed in mitigating the harmful impacts of petroleum waste on the environment. Lubricating oils, which are essential for the smooth operation of engines, are often disposed of improperly after completing their life. In the experimental work presented in this paper, deteriorated engine oil was regenerated using the acid treatment method and was reused in the engine. The comparison of the properties of reused oil, the engine’s performance, and the emissions from the engine are presented. The reuse of regenerated oil, the evaluation of performance, and emissions establish the usefulness of the regeneration of waste lubricating oil. For the used oil, total acid number (TAN), specific gravity, flash point, ash content, and kinematic viscosity changed by 60.7%, 6.7%, 4.4%, 96%, and 15.5%, respectively, compared with fresh oil. The regeneration partially restored all the lost lubricating oil properties. The performance parameters, brake power (BP), brake specific fuel consumption (BSFC), and exhaust gas temperature (EGT) improved with regenerated oil in use compared with used oil. The emissions CO and NOX contents for acid-treated oil were 9.7% and 17.3% less in comparison with used oil, respectively. Thus, regenerated oil showed improved performance and oil properties along with significantly reduced emissions when employed in an SI engine.

Efficiency and energetic analysis of the production of gaseous green fuels from the compressed steam and supercritical water gasification of waste lube oils

The gasification of a waste lube oil (WLO), using water under vapor and supercritical states leads to its valorization into green fuels with high energetic power like H2 and CH4. This work investigates how the most important variables of a flow continuous gasification process, temperature, pressure and reaction time, influence the efficiency of gasification and the amounts and characteristics of the gases produced. The study of the influence of these variables on the energetic efficiency of the process was also completed. The highest production yields, 2.4 10−2 molH2goil−1 and 3.0 10−2 molCH4goil−1, were registered at supercritical water conditions (750°C, 250 bar and 1.87 min). The energetic study revealed that the energetic efficiency increased as the reaction time was lengthened. Gasification kinetics were slower as pressure increased but the reaction times inside the flow reactor were longer. A pressure range from 150 bar, steam region, to 250 bar, supercritical region, was identified as optimal since allowed the most suitable balance between kinetics and the reaction times achieved.

Investigation of the rheological properties of waste and pure lube oils

In this study, the rheological characteristics of the waste and pure lube oils were investigated experimentally. Studying these characteristics are useful for understanding the behavior of lubricants and the recycling of waste lube oils. The Fann Model of 50SL rheometer with coaxial cylinders was employed for this investigation. Four different types of waste and pure lube oils were examined, namely: diesel-, petrol-, motorcycle-, and jet-engine oils. The results from the study show that the viscosities of all types of lube oils decrease gradually with temperature and shear rate due to the reduction of the intermolecular forces, which leads to a decline in the flow resistance. At a specific shear rate of 100 s−1 and heating the oils from 50 °C to 90 °C, the viscosity drops almost 60% for pure & waste diesel lube oils, 60–64% for pure & waste petrol lube oils, 48–50% for pure & waste motor-cycle lube oils, and 50–60% for pure & waste jet lube oils, respectively. The well-known Arrhenius relationship was also utilized in studying the temperature effect of the apparent viscosity.

Biofuel from Pyrolysis Waste Lube Oil of Refinery Unit III Using Fly Ash of Coal Combustion as a Catalyst

Lube oil waste obtained from Utilities Unit, Crude Distillation Unit, and Crude Distillation & Light End Unit at Refinery Unit III Plaju Palembang South Sumatra. The process of pyrolysis of lube oil waste using fly ash catalyst is expected to produce fuel oil. Lube oil waste pyrolysis uses Fly Ash catalysts with a total catalyst of 500 g with a temperature range variation of 0-85, 85-16, 165-250, 250-300, and 300-350oC, while pyrolysis of waste lube oil without catalysts with a variation in the temperature range of 0-85, 85-165, 165-250, 250-300, and 300-350 oC. Temperature range variations are referenced based on boiling route solvent fraction (0-85 C), premium fraction (85-165 oC), kerosene fraction (165-250 C) and diesel (250-350 C). Solvent fraction cannot be analyzed because there is no product result whether it is pyrolysis process using catalyst or without catalyst, Premium Fraction is only produced using catalyst, analysis result Octane Number 76.6. Sulfur content, Density and flash point analysis of pyrolysis products using catalysts and without catalysts in accordance with kerosene products in the market. Solar fraction of pyrolysis process using catalyst and without catalyst, Analysis results cetane numbers 43.2 and 45.6 have not met the specifications of solar products

Study on extraction of pollutant free flammable fuel from contaminated automobile waste lube oil

Purpose: of this paper is to investigate the reusability of contaminated waste lubricant oil as flammable fuel by thermal and catalytic cracking process followed by distillation. It also includes the study of using Zeolite and Nickel nano particles as catalyst and its influence catalytic cracking. Design/methodology/approach: A conventional sterilization technique called Autoclaving method, uses high-pressure steam to separate water and other solid waste from the lube oil. It is followed by thermal cracking which breaks the molecular chains and decompose the waste lube oil. The autoclaving process works by the concept that the boiling point of water (or steam) increases when it is under pressure. Findings: Now a days, Industrial and Automobile waste lubricating oils are giving big threat ecology while burning and disposing on bare land. Furthermore, they discharged into the open environment which might make destructive sicknesses to ecology. In water, oil is a visible pollutant, floating as a scum on the surface. Moreover, there is a gradual rise in fuel requirement across the globe, and the consumption of oil assets have driven the researchers to find elective power for internal combustion engines. By the way, diminishing of fossil sources, growing of demand and cost of petroleum based fuels and its environmental hazards as a result of burning or disposing on land have encouraged to investigate possibility of recycling of waste engine oil. Research limitations/implications: A series of process such as filtration, cracking followed by distillation needs expensive experimental setup and regular maintenance as the extracted flammable oil fuel possess significant range of dynamic viscosity values. As all real fluids has its own viscosity, in near future, an investigation is about to do on its behaviour on blending with other flammable fluids. Practical implications: Although the result of this investigation conforming its flammable characteristic of the extracted fuel, the quantity of pollutant free flammable fuel from waste contaminated lube oil being extracted is significant, the cost of catalyst is considerably more, as it plays the most vital part in cracking. This effort likely also reduces foreign exchange, reduces greenhouse emissions and enhances regional development especially in developing countries. Originality/value: The novelty of the work is to prepare pollutant free flammable fuel from waste Lube oil by catalytic cracking process. Here Zoelite and Nickel nanoparticles are used as catalyst which breaks the long-chain molecules of the high boiling hydrocarbon liquids into much shorter molecules.

Treatability of a used Lube Oil from Contaminated Soil

The oily petroleum hydrocarbon discharge lead to the soil pollution, become harmful to both human being and the environment by long run. This present work is carried out systematically to evaluate the efficiency of Brij-35 for washing used lubricant oil. For this study, the soil and waste engine oil which was collected from local service station are characterized. The soil under study was categorized through soil gradient test. The permeability of the soil was also determined. The soil fraction which was obtained by sieving through mm sieve was used for the present analysis. All the characteristic properties of the soil and oil were tested by a prescribed method. The used lube oil density was 0.853 gm/cc at 15C. The interfacial tension of the oil under study was 52.1 mN/m. This important finding helpful in finding the solution for soil contamination by improper disposal of oily hydrocarbon wastes like waste lube oil.

Model Prediction and Optimization of Waste Lube Oil Treated with Natural Clay

In this work, used lube oil was treated using natural acid-free clay. Clay was added at different amounts (5, 10, and 20 g) to 100 mL of waste engine oil at various temperatures (250, 350, 400, and 450 °C) and mixed at a speed of 800 rpm for 30 min. After settling and separation, the treated oil was diluted with kerosene before being examined using a Ultraviolet–visible (UV) spectrophotometer. In order to achieve cost-effective recycling, this process is modeled using the response surface method (RSM). Five regression models (linear, quadratic, Two Factor Interactions (2FI), cubic, and reduced-order quadratic model) were developed, then tested, and examined by calculating the statistical performance indicators (R2, R2adj, Akaike’s Information Criterion corrected (AICc), Bayesian Information Criterion (BIC), and Root Mean Square Error (RMSE)). The results obtained reveal that the modified quadratic model outperforms the rest of the models in terms of the low value of RMSE, the lowest AICc, lowest BIC, and the highest R2 and R2adj. The developed modified quadratic model is optimized successfully to predict optimum operation conditions. Results show that optimum operation conditions are at the minimum area under the curve for UV absorption at 223.358; this can be achieved with a process temperature of 266.246 °C and clay quantity of 5.331 g. This model agreed with experimental data regardless of the effectiveness of red clay in the therapy of lube oil.

Recent advances in waste lube oils processing technologies

Waste lube oils are classified as hazardous waste due to the metal contents derived from the additives and wear. Most lube oils contain up to 20% of additives including antioxidants, anti‐wear, and de‐foaming agents which are generally used to extend the usage of lube oils and enhance engines performance. The most widely‐used additives contain metal as they exhibit efficacy in performance enhancement. However, these additives increase the hazardous level of waste lube oils and are highly toxic when released into the environment. Waste lube oils processing can minimize the toxicity and the complexity of the waste and may produce valuable products at the same time, such as, fuels, solvent, and base oils for production of new lube oils. In this paper, the common technologies for waste lube oils processing, including physical and chemical processes are reviewed. In addition, more recently developed technology such as membrane technologies and their potential application in waste lube oil processing are also discussed. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1867–1881, 2018

Waste lube-oil based fuel characterization in real conditions. Case study: Bottom-trawl fishing vessel powered with medium speed diesel engine

The high-fuel dependency of the shipping industry and its corresponding pollutant emissions need to be addressed within the new de-carbonisation era. Concurrently, the waste-to-energy concept arises to drive sustainable initiatives for energy production. In that sense, in the present study, the feasibility of an alternative fuel oil (AFO) based on recycled-waste lubricating oil was assessed. Tests were conducted on board a bottom-trawler fishing vessel, under real operating conditions. The fishing activity was monitored, and the engine performance, the combustion and injection properties, and the emissions characteristics were studied. The vessel performance when operating on the AFO was compared with that when operating on standard distillate diesel oil (DFO). The results showed that the AFO required preheating up to 70 °C owing to its higher viscosity value, which is considerably higher than the allowed by the ISO 8217 standard for distillate fuels. Therefore, a heating module was installed on board the vessel to ensure optimal performance with the AFO. The fuel consumption was slightly lower for the AFO; however, owing to its higher low-heating value, the engine efficiency was higher when using the DFO. The AFO presented lower combustion pressure than the DFO and a longer combustion period; however, its ignition process occurred earlier. The results suggested that the AFO contained light components which caused the early ignition of the fuel, as well as heavy components, which delayed the end of the combustion. The NOX emissions were considerably reduced with the AFO by 15%; the CO2 emissions were slightly reduced as well; however, CO emissions were higher for the AFO by 15%. By operating under the usual conditions while burning the AFO throughout a year, the vessel would consume 8 t of fuel less, and would emit 21 t of greenhouse gases less. The vessel burnt a total of 40,000 L of AFO, for approximately 300 h, without any operational issue. The results demonstrate that the distillate fuel obtained from lubricating oil is suitable for marine medium-speed engines and enables satisfactory performance.

Changes in Components of Tyre-derived Oil After Sulphur and Heteroatom Removal Using Three Acids

Tyre-derived oil consists of many types of hydrocarbons such as aromatic hydrocarbons and sulphur compounds. Aromatic hydrocarbons can generate gum in the engine, which results in a lower efficiency of the engine and causes black smoke. Moreover, sulphur compounds can also cause air pollution. Conventionally, acid treatment has been adopted by small companies that aimed at reducing aromatics, but it also gives undesired compounds in the tyre-derived oil. It has been reported that sulphuric acid can remove impurity and sulphur compounds in waste lube oil. However, it is suspicious that sulphuric acid used in the acid treatment can also form heteroatom-containing hydrocarbon molecules, such as S compounds, in the oil. So can other acids. In this work, sulphuric acid, nitric acid, and hydrochloric acid were used as chemicals in acid treatment in order to investigate the changes in components in tyre-derived pyrolysis oil. The products were analyzed by using SIMDIST-GC, GC×GC-TOF/MS, and S analyzer. The results showed that the volume of tyre-derived oils decreased about 50 wt.% together with 50 % sludge formation when sulphuric and nitric acids were used. For hydrochloric acid, the volume of tyre-derived oil decreased about 10 wt.%. The tyre-derived oil contained 5% gasoline, 25 % kerosene, 35 % gas oil, LVGO 8 % and HVGO 27 %. The results from GC×GC-TOF/MS were used to explain the changes in oil components before and after treatments.

Rerefining of Waste Lube Oil via Solvent Extraction Followed by Catalytic Hydrotreatment

Rerefining of Waste Lube Oil via Solvent Extraction Followed by Catalytic Hydrotreatment

Characterization and differentiation of chemical fingerprints of virgin and used lubricating oils for identification of contamination or adulteration sources

Lubricating oil plays a critical role to reduce friction and to ensure the machines are more energy efficient in terms of fuel consumption and power output. The use of unqualified lube oil can result in malfunctions and damage to engines and machinery. Since petroleum-based lube oils are among the most valuable refined products, in some regions, fake, used, or waste lube oils have occasionally been deliberately adulterated into lube oil to extend the volume sold. On the other hand, used or waste lube oil is hazardous material, containing contaminants such as metals and polycyclic aromatic hydrocarbons produced by the engine during use. It becomes an environmental problem when it is purposely disposed of or accidentally spilled into the environment. Some jurisdictions now have relevant regulations to prohibit these illegal activities; therefore, forensic analysis of lube oils is essential to differentiate fake and used lube products from virgin oils, to identify and to track the adulteration source, and to identify the source of spilled oil. This work involved a fingerprinting analysis of a suite of oil samples including a virgin lube oil, used motor oils, a waste lube oil from a motor workshop, a regular diesel oil and a biodiesel blend, etc. The chemical fingerprints such as the abundance and distribution profiles of total petroleum hydrocarbon, polycyclic aromatic hydrocarbons (PAHs), particularly the higher molecular pyrogenic PAHs, and biomarkers indicate that the used and the waste lube oils are mixtures of mainly lube oil and a small amount of diesel type fuel. The presence of C16 to C20 fatty acid methyl esters (FAME) with the dominance of C16:0 and C18:1 isomers suggests that the used and the waste lube oils both contain residual palm oil-based biodiesel.

Transformation of tetramethyldisiloxane in used oil alkali treatment conditions: mechanism and kinetic modeling

AbstractBACKGROUNDThe behavior of silicon species in the recycling processes of waste lube oils is of great interest because of the negative effect of silicon compounds on the performance of hydrotreating catalysts and the formation of undesired solid deposits at various locations in the re‐refining units. To operate alkali treatment of silicon‐containing used oils efficiently in the recycling industry prediction of silicon species behavior is required. To this end kinetic modeling of the base catalyzed transformation of a model siloxane compound was done.RESULTSA kinetic model was developed for tetramethyldisiloxane (TMDS) transformation reactions under industrially relevant alkali treatment conditions in dodecane with sodium hydroxide as alkali agent. A reaction scheme describing the main pathways of TMDS transformation was proposed considering experimental and literature data. The studied model compound underwent hydrolysis, condensation and disproportionation reactions with formation of different molecular weight linear siloxanes. The latter were transformed to cyclic siloxanes through sodium silanolates generation. The data obtained experimentally were validated with the advanced kinetic model.CONCLUSIONSThe proposed model fitted experimental data adequately, indicating that it can be used in the design and control of the caustic treatment of used oil containing silicon species. © 2015 Society of Chemical Industry

Hydrotreating of waste lube oil by rejuvenated spent hydrotreating catalyst

Large quantities of catalysts are used in the Egyptian refining industry for the purification and upgrading of various petroleum streams. These catalysts gradually lose activity through deactivation with time and the spent catalysts were usually discarded as solid waste. On the other hand, waste lube oil contains heavy metals coming from undergirded base oil and additives, these metals have carcinogenic effect and cause serious environmental problems. Studies are conducted on the reclamation of metals, rejuvenation and reuse of the spent hydrotreating catalyst (Mo–Ni/Al) which have been used in re-refining of waste lube oil at Alexandria Petroleum Company. Three leaching solvents were used: oxidized oxalic acid, benzoic acid and boric acid at different concentrations (4%, 8% and 16%), different oxidizing agents (H2O2 and Fe(NO3)3) and different modes of addition of oxidizing agents (batch and continuous). The results indicated that 4% oxalic acid+5% Fe(NO3)3 at continuous addition of oxidizing agents was the most efficient leaching solvent to facilitate metal removal and rejuvenate catalyst. The fresh catalyst was applied for re-refining of waste lube oil under different reaction temperatures (320–410)°C in order to compare the hydrodesulphurization (HDS) activity with both the fresh, treated and spent catalysts. The results indicated that the rejuvenation techniques introduce a catalyst have HDS activity nearly approach to that the fresh of the same type.

Investigation of Thermodynamic Parameters in the Thermal Decomposition of Plastic Waste−Waste Lube Oil Compounds

Thermal decomposition properties of plastic waste-waste lube oil compounds were investigated under nonisothermal conditions. Polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were selected as representative household plastic wastes. A plastic waste mixture (PWM) and waste lube oil (WLO) were mixed with mixing ratios of 33, 50, and 67 (w/w) % on a PWM weight basis, and thermogravimetric (TG) experiments were performed from 25 to 600 degrees C. The Flynn-Wall method and the Ozawa-Flynn-Wall method were used for analyses of thermodynamic parameters. In this study, activation energies of PWM/WLO compounds ranged from 73.4 to 229.6 kJ/mol between 0.2 and 0.8 of normalized mass conversions, and the 50% PWM/WLO compound had lower activation energies and enthalpies among the PWM/WLO samples at each mass conversion. At the point of maximum differential mass conversion, the analyzed activation energies, enthalpies, entropies, and Gibbs free energies indicated that mixing PWM and WLO has advantages in reducing energy to decrease the degree of disorder. However, no difference in overall energy that would require overcoming both thermal decomposition reactions and degree of disorder was observed among PWM/WLO compounds under these experimental conditions.

A web-based decision support system for waste lube oils collection and recycling

This paper presents a web-based decision support system (DSS) that enables schedulers to tackle reverse supply chain management problems interactively. The focus is on the efficient and effective management of waste lube oils collection and recycling operations. The emphasis is given on the systemic dimensions and modular architecture of the proposed DSS. The latter incorporates intra- and inter-city vehicle routing with real-life operational constraints using shortest path and sophisticated hybrid metaheuristic algorithms. It is also integrated with an Enterprise Resource Planning system allowing the utilization of particular functional modules and the combination with other peripheral planning tools. Furthermore, the proposed DSS provides a framework for on-line monitoring and reporting to all stages of the waste collection processes. The system is developed using a web architecture that enables sharing of information and algorithms among multiple sites, along with wireless telecommunication facilities. The application to an industrial environment showed improved productivity and competitiveness, indicating its applicability on realistic reverse logistical planning problems.

Comparison between emissions from the pyrolysis and combustion of different wastes

A comparison between different emission rates of various pollutants obtained from various wastes is presented. The studied wastes were the following: polyethylene (PE), tyres, sewage sludges, polyvinyl chloride (PVC), cotton textiles, polyester textiles, meat and bone meals (MBMs), varnish wastes, olive oil solid waste (pomace), waste lube oils and paper waste. The decomposition of these wastes was studied in a horizontal laboratory scale reactor under fuel-rich conditions, and the analysis of the pollutants evolved comprised several compounds such as light hydrocarbons, polyaromatic hydrocarbons (PAHs) and polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs). From the studied wastes, a general behaviour was deduced regarding the evolution of semi-volatile compounds with the increase of temperature, both in pyrolysis and combustion. The results showed that the emissions of some compounds decreased with increasing oxygen ratio. Compounds with this behaviour were mainly volatile hydrocarbons, which were consumed in presence of oxygen. In addition, compounds with oxidized structure were present a maximum with oxygen ratio. Intermediate compounds with very high resistance to the oxygen under the working conditions increased continuously in concentration when the oxygen ratio increased. With reference to behaviour versus temperature there were compounds whose yields decreased with increasing temperature, such as volatile hydrocarbons and semi-volatile compounds. Also some pollutants are promoted at intermediate temperatures, e.g. light hydrocarbons, semi-volatile compounds, many monoaromatic compounds and many polyaromatic hydrocarbons.

Treatment and Reuse of Spent Hydrotreating Catalyst

Large quantities of catalysts are used in the Egyptian refining industry for the purification and upgrading of various petroleum streams. These catalysts gradually lose activity through deactivation with time, and the spent catalysts are usually discarded as solid wastes. Studies were conducted on rejuvenation, reclamation of metals, and reuse of the spent hydrotreating catalyst, Mo-Ni/Al2O3, which has been used in re-refining of waste lube oil derived from the Alexandria Petroleum Company. Its lifetime after several regeneration operations was five years. Selective leaching treatments were carried out with organic oxalic acid in order to rejuvenate the spent catalyst for use in other reactions or metal recovery. The results indicated that 4% oxalic acid oxidized by 5% H2O2 was the most efficient leaching solvent to facilitate the metal removal and the rejuvenated catalyst characterized by the unchanged crystalline phase of the catalyst. Four percent oxalic acid leaching solution gave total active and non-active metal removal 17.4% and 45.6% for coked and decoked catalyst samples, while the selective removal for the active Mo and Ni metals was 69.87% and 24.63%, respectively. The activity of the rejuvenated catalyst was tested for hydrodesulfurization (HDS) of vacuum gas oil under reactor temperature 300°C–380°C and hydrogenation of heptene-2 under different GLC-pulse reactor temperature 200°C–400°C. The results indicated that the rejuvenation technique introduced a catalyst having an HDS-activity that nearly approached that of the fresh catalyst sample of the same type, i.e., 94% and 98%, respectively, and other types that have hydrogenation activity can be used in petrochemical hydroprocessing at lower temperatures. The selective recovery of Mo, Ni, and Al from the spent catalyst was processed well by the aid of acid leaching and gave metal recovery as metal salts. Therefore, this work can provide a complete solution to the environmental problem of spent hydroprocessing catalysts in a profitable way.