Hydrodesulphurization Research Articles

Metal recovery from spent Ni-Mo-V hydrodesulphurisation catalyst in oxalic acid media by mechanochemical treatment

ABSTRACT The spent hydrodesulphurisation (HDS) catalysts used for the removal of sulphur from petroleum products can be a secondary source of especially Mo and V. This work describes the mechanochemical extraction of Mo, Ni, V, Al and P from spent petrochemical catalysts in H2C2O4. The effect of rotational speed, H2C2O4 concentration, ball to the dust weight ratio and solid-to-liquid ratio on the extraction rate of roasted spent catalyst was investigated. The reactions proceed with an increase in H2C2O4 concentration for extraction of Mo, V and P. The reactions for the extraction of Mo, V and P proceed with an increase in H2C2O4 concentration, but the dissolution behaviour of Ni is different from other elements. 87% of Mo, 44% of Ni, 82% of V, 36% of Al and 78% of P were extracted at optimum experimental conditions.

A feasibility study for a circular approach in oil refining: Metals recovery from hydrodesulphurization catalysts

The paper deals with a profitability analysis developed for a plant that recycles spent hydrodesulphurization (HDS) catalysts. Such catalysts contain molybdenum (Mo), nickel (Ni), and vanadium (V), supported by an alumina (Al2O3) carrier. The recycling process is based on a double thermal pre-treatment stage, followed by a series of hydrometallurgical steps that allow recovering Mo and V and a Ni concentrate that need further refining for separation and recovery of the metals.The economic analysis is based on the discounted cash flow method, and the baseline case analyses show that the net present value (NPV) is 14,877 thousand EUR. The selling price of vanadium pentoxide strongly influences the results. Alternative scenarios are also studied to strengthen the results obtained, considering the sensitivity, scenario and risk analyses. Profitability is confirmed in 87% of the considered scenarios, and in about 81.5%, the NPV of the baseline scenario is achieved. Circular economy models can be realized if products are recovered and if there are technologies that can recover metals. This study confirms that an example of a circular economy is met from the proposed viability analysis, and the economic benefits can be significant.

COMPARATIVE STUDY FOR HYDRODESULPHURIZATION (HDS) AND HYDROGENATION OF THE CONSTITUENT ELEMENTS IN LACUSTRINE OIL SHALE DEPOSIT AT TIMAHDIT (MOROCCO)

Hydrodesulphurization (HDS) and hydrogenation are carried out by thermal treatment using hydrogen (H2) with the objective of either removing sulphur from the material, or improving the yield of the organic material, or finally forming hydrides by reaction of the elements contained in the mineral matrix with hydrogen. The reaction kinetics are simpler when hydrogen is used compared to pyrolysis, the order of the reaction is equal to unity (A. Attaoui: 1993). The Timahdit (Morocco) oil shale lake deposit is composed, apart from organic matter (kerogen), of a considerable number of metallic, metalloid and non-metallic elements constituting the mineral matrix. We carried out the hydrogen treatment in a dynamic regime (21°C/mn) in thermogravimetry by the Red-Croft balance (A. Attaoui et al: 2022). The choice of the Z1 layer of the Tarfaya marine deposit was made because of the similarity in the quantity of organic matter between this layer and that of the Timahdit deposit (M2).

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.

THERMAL VARIATION OF THE DIFFERENT LAYERS FORTARFAYA DEPOSIT (MOROCCO) IN HYDRODESULPHURIZATION AS WELL AS HYDROGENATION OF CALCIUM Α, ꞵAND MAGNESIUM AT 550°C AND 750°C.

Hydrodesulphurization (HDS), deuteriodesulphurisation, calcium hydrogenation and deuterium treatment are reactions that occur simultaneously when oil shales are treated with hydrogen. In this work, quantitative monitoring of the target elements (sulphur, calcium and magnesium) was carried out using the dispersive X-ray diffraction technique (a technique coupled with a scanning electron microscope). The treatment of oil shale with hydrogen with the objective, either to improve the products preventing oil shale (gas, oil and solid fuel) or in the particular sense to get rid of some undesirable elements having harmful effects on the course of the exploitations of materials we quote the phenomenon of corrosion. An example of this is hydrodesulphurization, which is a reaction that is used to remove sulphur. This hydrogenation reaction was followed in a first work for the different oil shale layers of Tarfaya (M. Hafid and A.Attaoui: 2022) at a temperature of 550°C. However we were able to raise the temperature to 750°C for this study, in the same sense of the continuity of the action by hydrogen on elements such as calcium and magnesium in the temperature domains this study has been continued.

A comprehensive theoretical investigation on the thiophene hydrodesulphurisation mechanism over sulphided Co–Mo catalysts supported by ZSM-5, FAU, Beta and MCM-22 zeolites

ABSTRACT We have theoretically studied the hydrodesulphurisation (HDS) mechanism of thiophene and its hydrogenated derivatives over sulphided Co–Mo catalysts supported by four zeolites (ZSM-5, FAU, Beta, MCM-22) by a two-layer ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) method. Due to low energy barriers, the thiophene can be hydrogenated to 2,3-dihydrothiophene (2,3-DHT), 2,5-dihydrothiophene (2,5-DHT) and tetrahydrothiophene (THT). Direct desulphurisation (DDS) and hydrogenolysis desulphurisation (HYD) pathways were investigated in detail. The calculated results show that in DDS mechanism of thiophene, the rate-determining step is the C–S bond cleavage. In HYD mechanisms of 2,5-DHT, 2,3-DHT and THT, the rate-determining step is hydrogen transfer on ZSM-5, FAU and Beta zeolites except MCM-22 zeolite. The HYD of 2,3-DHT and THT should occur by the stepwise pathway. But for the 2,5-DHT, the concerted pathway is probably more favourable than the stepwise pathway. The reduced density gradient (RDG), differential charge density (DCD), and local orbital locator (LOL) maps show that for all transition states (TSs), there are complicated van der Waals (VDW) and electrostatic interactions between the organic fragment and the catalytic centre.

Modeling of three-phase radial flow reactor for diesel hydrotreating

• Mixing cell network model presented for industrial-scale three-phase Radial Flow Reactor for diesel hydrodesulfurization. • 2D MCN model was developed for Radial Flow Reactor (RFR) with one and five distributors to predict the product quality and bed temperature profiles. • Reactions like hydrodesulphurization (HDS), Hydrodearomatisation (HDA), and olefins saturation are taken into consideration. A mathematical model for a novel industrial-scale three-phase catalytic Radial Flow Reactor (RFR) has been developed using a two-dimensional mixing cell network (MCN) model. RFR is predominantly used for gaseous phase reactions in the petroleum refining industry. This work discusses the capabilities of three-phase RFR for diesel hydrodesulfurization. The reactions considered for the model development of diesel hydrodesulfurization are hydrodesulfurization, hydrodearomatisation, and olefins saturation. Apart from the well-known advantage of RFR, such as pressure drop, the analysis revealed other benefits such as better product quality, reduced H 2 S inhibition, no requirement of quench, high WABT. Simulations for RFR were performed for different gas distributors and results show that distributor design impacts the performance of reactor.

The effect of acid treatment and calcination on the modification of zeolite X in diesel fuel hydrodesulphurization

AbstractFaujasite (X, Y) zeolites are considered the main and important catalysts in hydrorefining processes. In order to obtain zeolites with higher acidity and volume of mesopores, post‐synthesis modification, dealumination by different pickling techniques (using ethylenediamine tetraacetic acid [EDTA] chelating agent), and thermal treatment (calcination) were employed. The dealumination process led to the removal of the aluminum atoms from the zeolite structure and a rise in acidity while maintaining the zeolite crystalline lattice. X‐ray diffraction (XRD), atomic absorption spectrometry (AAS), Fourier‐transform infrared (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), Brunauer–Emmett–Teller (BET), and temperature‐programmed desorption of ammonia (NH3‐TPD) analyses were performed to study the physicochemical characteristics of the zeolite and catalysts prepared. Atomic absorption spectroscopy showed an increase in the Si/Al ratio in the modified zeolites. Measuring the surface area of zeolite and the volume of the pores through BET‐BJH and t‐plot methods indicated a reduction in the surface area and an increase in the volume of the pores. Under the influence of the dealumination process, the volume of the mesopores in the modified zeolites increased from 0.056 cm3 g−1 in the initial zeolite (Na‐X) to 0.2105 cm3 g−1 (zeolite X1). The acidity of the modified zeolites (X1) increased from 0.32–0.95 mmol NH3/g. The application of the catalysts containing X1 zeolite in the hydrodesulphurization (HDS) process yielded a product with less sulphur (conversion = 87.5%).

A fast and efficient method for the efficient recovery of crude oil from spent hydrodesulphurization catalyst

The deoiling process is a critical issue in catalyst regeneration and recovery of precious metals from spent catalysts. This study developed a fast and efficient method to recover crude oil from spent hydrodesulphurization (HDS) catalysts. We employed four solvents (p-xylene, acetone, dichloromethane, and n-hexane) with different polar and aromatic properties to remove crude oil from the spent catalyst. The effects of environmental factors, such as contact time, ratio of catalyst to solvent, temperature, stirring rate, and particle size on washing efficiency were investigated. The crude oil and solvent in the oil-containing washing solution were then effectively separated and recovered. The recovered solvent was used to evaluate solvent cycle washing performance, and the recovered oil was analyzed by gas chromatography-mass spectrometry. The spent and deoiled catalysts were characterized by scanning electron microscope, interracial rheometer, and contact angle. The results showed that p-xylene, which has similar polarity and aromaticity to the molecular structure of crude oil, achieved an excellent crude oil washing effect. The crude oil washing efficiency of the spent catalyst can exceed 94% in 2 min. Furthermore, the solvent was recycled 10 times, and still maintained a removal efficiency of over 93% for crude oil in the spent catalyst. Compared to crude oil, recovered oil has less viscosity, ash, residual carbon, and a higher heat of combustion, allowing it to be more easily refined and recovered, and to gain more energy as an energy source.

A theoretical investigation on the hydrodesulphurisation mechanism of hydrogenated thiophene over Cu–Mo-modified FAU zeolite

ABSTRACT We have theoretically investigated the hydrodesulphurisation (HDS) mechanism of hydrogenated thiophene over Cu–Mo-modified FAU zeolite using a two-layer ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) study. The thiophene is hydrogenated to 2,3-dihydrothiophene (2,3-DHT), 2,5-dihydrothiophene (2,5-DHT) and tetrahydrothiophene (THT) due to moderate free energy barriers. Hydrogenolysis desulphurisation (HYD) and concerted direct desulphurisation (DDS) are discussed. Ring-opening, hydrogen transfer and C−S bond cleavage steps of thiophene derivatives are involved in the HYD process. The rate-determining steps are the hydrogen transfer step for 2,5-DHT and C−S bond cracking step for 2,3-DHT and THT. The concerted DDS pathway is probably more favourable than the HYD pathway in the desulphurisation of 2,5-DHT. The difference charge density (DCD) analysis reveals that for the ring-opening process, the electrons are migrated from the organic chain to the Cu–Mo catalytic centre. The reduced density gradient (RDG) plots indicate that both steric hindrance and a weak van der Waals (VDW) interaction exist between organic fragment and catalytic centre for all transition states (TSs). The localised orbital locator (LOL) maps suggest that there are strong covalent interactions and weak VDW interactions between the atoms in the forming chemical bonds.

Desulphurisation of dibenzothiophene and 4,6–dimethyl dibenzothiophene via enhanced hydrogenation reaction route using RePd–TiO2/SiO2 aerogel catalysts: kinetic parameters estimation and modelling

Re/Pd-TiO2/SiO2 aerogel catalysts were synthesized by using a sol-gel method and supercritical drying in excess solvent and investigated in the reaction of hydrodesulphurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Both Re/Pd catalysts, obtained with and without the use of mesitylene in the synthesis step, have shown increased conversions of up to 70 % in the desulphurization of 4,6-DMDBT, when compared to conventional Co/Mo hydroprocessing catalysts. This observation is of importance for conversion of highly refractory 4,6-DMDBT and hydroprocessing to produce ultra-low sulphur diesel fuels, ULSD. In order to quantify the extent of desulphurisation, which proceeds via a hydrogenation route, conversions of DBT and 4,6-DMDBT along with evolution of reaction products characteristic for the direct desulphurisation route and the hydrogenation route were monitored by using a gas chromatography?mass spectrometry (GC-MS) analytical technique. The reaction was performed at 630 K and 6 MPa in a batch catalytic reactor. The experimental results were used in the Hougen-Watson kinetic model describing DBT and 4,6-DMDBT desulphurisation on ? and ? active sites. Kinetic parameters of this complex catalytic kinetics were determined by using a Genetic Algorithm method and minimum deviation function. Values of calculated kinetic parameters and values of the ratio of 3-methylcyclohexyltoluene (MCHT and dimethyl biphenyl (DMBPH) expressed as the MCHT/(MCHT+DMBPH) ratio ranging between 0.66 and 0.94, have confirmed that the hydrogenation route is the dominant route for desulphurisation of 4,6-DMDBT.

Modelling of hydrodesulphurization in industrial trickle bed reactor using mixing cell network approach

AbstractA mixing cell network (MCN) was developed for the commercial diesel hydrodesulphurization process (DHDS) in a trickle bed reactor (TBR). The two‐phase model is developed to simulate the performance of an industrial DHDS unit. Major hydrotreating reactions such as hydrodesulphurization (HDS), hydrodearomatization (HDA), and olefin saturation were accounted for in the developed model. The MCN model predictions on axial concentration profiles of sulphur, polynuclear aromatics (PNAs), monoaromatics (MAs), and temperature were found to be in agreement with the real‐time plant data. Further, the predicted results were also compared with the plug flow model to confirm model adequacy. The results obtained in this paper show the efficacy of the MCN model in simulating multiple reactions happening in real industrial scenarios.

Recovery of molybdenum, cobalt and nickel from spent hydrodesulphurization catalyst through oxidizing roast followed by sodium persulfate leaching

The spent hydrodesulphurization (HDS) catalyst is an important secondary source for Ni, Mo, Co and Al metals. The high yield recovery of these metals is quite difficult due to the carbon accumulated on the catalyst surface and the stability of the metal oxides. Therefore, the leaching process in the presence of sodium persulfate (Na2S2O8) was carried out after the roasting pre-treatment to remove the carbon from the spent HDS catalyst structure and convert the metal oxides to the soluble form in this study. The optimum experimental conditions were determined as roasting temperature, 500 °C; roasting time, 120 min.; particle size, +75–30 μm; liquid/solid ratio, 12.5 mL/g; Na2S2O8 concentration, 0.4 M; leaching temperature, 50 °C; leaching time, 90 min and stirring speed, 400 r/min. Recovery of Mo (89.8%), Co (86.5%) and Ni (81.2%) from leach solution were achieved by precipitation method. The liquid film diffusion control mechanism best represents the proposed leaching process. On the other hand, the magnitude of Ea values (<20 kJ/mol) for Mo, Co, Ni and Al metals indicates that the leaching process is controlled by liquid film diffusion mechanism.

Exciting Opportunities for Solid-State 95Mo NMR Studies of MoS2 Nano-structures in Materials Research from Low to Ultra-high Magnetic Field (35.2 T).

Solid-state, natural-abundance 95Mo NMR experiments of four different MoS2 materials have been performed on a magnet B 0 = 19.6 T and on a new Series Connected Hybrid (SCH) magnet at 35.2 T. Employing two different 2H-MoS2 (2H phase) materials, a "pseudo-amorphous" MoS2 nano-material, and a MoS2 layer on the Al2O3 support of a hydrodesulphurization (HDS) catalyst have enabled introduction of solid-state 95Mo NMR as an important analytical tool in studies of MoS2 nano-materials. 95Mo spin-lattice relaxation time (T 1) studies of 160- and 4-layer 2H-MoS2 samples at 19.6 and 35.2 T show their relaxation rates (1/T 1) increase in proportion to B 0 2. This is in accord with chemical shift anisotropy (CSA) relaxation being the dominant T 1(95Mo) mechanism, with a large 95Mo CSA = 1025 ppm determined for all four MoS2 nano-materials. The dominant CSA mechanism suggests the MoS2 band-gap electrons are delocalized throughout the lattice-layer structures, thereby acting as a fast modulation source (ω oτc << 1) for 95Mo CSA in 2H-MoS2. A decrease in T 1(95Mo) is observed for an increase in B 0 field and for a decrease in the number of 2H-MoS2 layers. All four nano-materials exhibit identical 95Mo electric field gradient (EFG) parameters. The T 1 results account for the several failures to retrieve 95Mo spectral EFG and CSA parameters for multilayer 2H-MoS2 samples in the pioneering solid-state 95Mo NMR studies performed during the past two decades (1990-2010), because of the extremely long T 1(95Mo) = ~200-250 s observed at low B 0 (~9.4 T) used at that time. Much shorter T 1(95Mo) values are observed even at 19.6 T for the "pseudo-amorphous" and the HDS catalyst (MoS2-Al2O3 support) MoS2 nano-materials. These allowed useful solid-state 95Mo NMR spectra for these two samples to be obtained at 19.6 T in a few to < 24 h. Most importantly, this research led to observation of an impressive 95Mo MAS spectrum for an average of 1-4 thick MoS2-layers on a Al2O3 support, i.e., the first MAS NMR spectrum of a low natural-abundance, low-γ quadrupole-nucleus species layered on a catalyst support. While a huge gain in NMR sensitivity, factor ~ 60, is observed for the 95Mo MAS spectrum of the 160-layer sample at 35.2 T compared to 14.1 T, the MAS spectrum for the 4-layer sample is almost completely wiped out at 35.2 T. This unusual observation for the 4-layer sample (crumpled, rose-like and defective Mo-edge structures) is due to an increased distribution of the isotropic 95Mo shifts in the 95Mo MAS spectra at B 0 up to 35.2 T upon reduction of the number of sample layers.

Prediction of ultra low sulphur diesel catalyst performance using limited pilot plant data

Due to the presence of refractory sulphur (S) compounds in the gasoil, the achievement of Ultra-low-Sulphur Diesel (ULSD) using the conventional bimetallic catalyst in the Hydrodesulphurization (HDS) process in order to bring sulphur down to less than 10 ppmwt is considered as a tough task/challenge and gain major attention due to the EPA regulations on the transportation fuel industry.In this work, a catalytic testing of four commercial alumina-supported cobalt–molybdenum (CoMo) catalysts were conducted using fixed bed pilot plant reactor using a complex real mixture of straight run gasoil fraction (C12-C20) in order to determine the operating conditions at industrial unit particularly by focusing on the refractory (S) compounds and determining their reaction kinetics parameters. A limited pilot plant real data and a simplified kinetic model were employed to estimate the kinetic parameters for the four tested CA, CB, CC and CD catalysts. A parameter estimation technique with explicit models was also used to determine their highest posterior density intervals. The technique is based on minimization of the sum of the square errors (SSE) between the experimental and predicted data of the residual sulphur concentrations in the product distributions. The results revealed that each catalyst showed, expectedly, different results translated into how longer a commercial run length can be extended.

The Role of tungsten in trimetallic Co-Mo-W/γ-Al2O3 heterogeneous catalysts for efficient hydro-desulphurisation

This study investigates the effect on catalytic activity of inserting tungsten metal (W) into trimetallic W-Mo-Co supported on a Gamma-Alumina (γ-Al2O3) heterogeneous catalyst used for hydrodesulphurisation (HDS) in an oil refinery. Bimetallic Co5Mo15/γ-Al2O3 and a trimetallic Co5Mo14W1/γ-Al2O3 catalysts were synthesised using incipient wetness impregnation. The synthesised trimetallic Co5Mo14W1/γ-Al2O3 catalyst exhibited better catalytic performance, with an 88% hydro-removal percentage of sulphur based on an HDS reaction of petroleum naphtha as compared to the 82% for the bimetallic 5Co-15Mo/γ -Al2O3 catalyst under the same operational conditions at a pressure of 11.5 bar, a temperature 598 K, and a reaction time of 3 hr. This enhanced catalyst activity can be attributed to the presence of tungsten increasing the number of metal sites on the catalyst’s reaction surface.

Aerogel Re/Pd-TiO2/SiO2 and Co/Mo-Al2O3/SiO2 catalysts for hydrodesulphurisation of dibenzothiophene and 4,6-dimethyldibenzothiophene

Re/Pd-TiO2/SiO2 and Co/Mo-Al2O3/SiO2 aerogel catalysts were synthesized using sol-gel method and supercritical drying in excess solvent, and investigated in the hydrodesulphurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). The influence of supercritical drying on the final catalytic properties of the materials was determined by parallel synthesis of aerogels and xerogels for Re/Pd-TiO2/SiO2 catalysts. The sol-gel method and supercritical drying were found to result in amorphous aerogels with relatively high degree of uniformity, of both supports and active phases. Corresponding xerogels were found to be similar to aerogels in terms of composition and structure, but characterized by lower specific surface areas. Catalytic activity of Co/Mo-Al2O3/SiO2 aerogel catalysts in HDS of DBT and 4,6-DMDBT has shown no major improvement in comparison to conventional Co/Mo catalyst. On the other hand, Re/Pd-TiO2/SiO2 aerogels, obtained with the addition of mesitylene or without it, achieved 70 % and 64 % higher conversion of 4,6-DMDBT than conventional Co/Mo catalyst, respectively. Increased catalytic activity can be attributed to well dispersed Re and Pd active phases across the catalyst structure, good incorporation of Ti within silica matrix, increased mesopore volumes and high specific surface areas.

Preparation and Catalytic Activity of Co-Mo/γ-Al2O3 Catalyst for Hydro-desulfurization Reaction

In this study, a bimetallic CoMo spicy supported on γ-Al2O3 heterogeneous catalyst was successfully prepared by an incipient wetness impregnation for Hydrodesulphurization (HDS) reaction of An-Najaf oil refinery heavy naphtha. The structural characteristics of the prepared 5Co-15Mo/γ-Al2O3 catalyst were evaluated by Scanning Electron Microscopy (SEM) and X-Ray Powder Diffraction (XRD) spectroscopies. The surface area, pore volume and pore size were determined by a Brunauer–Emmett–Teller (BET) method. The catalytic activity in the removal of sulphur compound from a heavy naphtha through the HDS at four different reaction temperatures (523, 548, 573, 598 °K) and four different liquid hourly space velocities (3, 4, 5, and 6 hr-1) under a constant ratio of 150 mL H2/1 mL naphtha and a hydrogen gas pressure of 1.5 MPa, has revealed that the prepared catalyst was efficient to remove 82 % of sulphur at 598 °K temperature and 3 hr-1 time. The enhanced selectivity of the CoMo/γ-Al2O3 catalyst through a hydro-treating reaction ascribes to the bimetallic-support interaction and the dispersion of MoS2 particles that leaded to a large edge-to-corner ratio of CoMoS slabs.

Effect of ultrasonication and chelating agents on the dispersion of NiMo catalysts on carbon for Hydrodesulphurization

The effectiveness of the ultrasonication (US) and chelating agents in the dispersion of NiMo supported on activated carbon were examined. Accordingly, NiMo catalysts supported on carbon were prepared through co-impregnation of the support using US or the addition of chelating agents namely citric acid (CA) or ethylenediaminetetraacetic acid (EDTA) to facilitate the dispersion of the metals on the support. A surface area analyzer was used to provide the BET surface area measurements. Fourier-transform infrared spectroscopy (FTIR) and a powder X-ray diffractometer were used for the characterization of the structure of the prepared materials. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analysis of the morphology and surfaces of the mapping of the prepared material was obtained to get insight into the metal dispersion on the support. Results revealed a uniform dispersion of the nickel and molybdenum particles on carbon, especially in the case of using EDTA as a dispersion agent. Hydrodesulphurization of dibenzothiophene on the prepared catalysts was tested in a high-pressure batch reactor 1000 ppm dibenzothiophene in decalin as a model fuel. The results indicated that the chelating agents have a positive impact on hydrodesulphurization (HDS) efficacy and the EDTA has more effect than others. 97 % HDS was achieved using NiMo/AC(EDTA) while 94 % and 92 % were obtained using NiMo/AC(CA) and NiMo/AC(US), compared to 89 % without the use of US and chelating agents.

A Comparative Study on SECA Compliance Options for Maritime Fuel Producers

In January 2015, the Sulphur Emission Control Areas (SECA) regulations changed so that ships that ply the Baltic Sea and the North Sea can no longer use bunker fuel that exceeds 0.1 per cent v/v of sulphur. Many changes have been seen in the maritime sector, especially in the Baltic Sea region (BSR). From studies, the impact is still somewhat negative for some maritime stakeholders, such as small-scale fuel producing companies who must produce fuel that complies with the SECA requirements. The impact analysis of their compliance options shows that hydrodesulphurisation (HDS) option is the most viable option with a commensurable investment return rate, but it is highly risky and expensive considering the incessant plummeting of fuel price and the financial status of such companies. However, even though the situation looks bleak for the small-scale maritime fuel producers, a deeper probe revealed a chance for exceptional opportunities for growth and profit through a change of business model to the maritime energy-contracting model (MEC). The study zooms in on a case study of a fuel producing company and empirically compares the operating costs of the MEC model (as a decentralised option) and the HDS process (as a centralised option) to determine which option will be most economically worthwhile if adopted as a SECA compliance strategy to ensure a rounded and robust choice-making process for maritime stakeholders in such situations.