Hydrodemetallization Research Articles

Template-free synthesis of hierarchical meso-macroporous γ-Al2O3 support: Superior hydrodemetallization performance

The design of hierarchically porous catalytic supports is considered as one of the most efficient strategies to achieve efficient mass transport and thus high catalytic performance in heterogeneous catalysis. As one of the most important catalytic supports, facile synthesis of γ-Al2O3 with hierarchical porosities is of great industrial importance. In this paper, nest-like hollow γ-AlOOH microspheres constructed from numerous hierarchically organized nanowires were synthesized via a template-free simple hydrothermal approach, from which hierarchically porous γ-Al2O3 microspheres with average macropores of 900nm, mesopores of 20nm and a pore volume of 0.93cm3/g were obtained readily. Due to their structural merits, such nest-like γ-Al2O3 microspheres could serve as excellent catalytic support. As a demonstration, a MoNi/γ-Al2O3 supported catalyst was prepared, which was applied for hydrodemetallization (HDM) catalysis. Compared with the catalyst prepared with the commercial γ-Al2O3, our catalyst exhibits superior catalytic performance and longer life due to enhanced diffusion of the reactants.

Hydrodemetallation and Hydrodesulfurization Spent Catalysts Elemental Analysis: Comparison of Wavelength Dispersive X-ray Fluorescence and Atomic Emission Spectrometries.

Petroleum industries continuously consume catalysts on very large scales. The recycling of spent catalysts is thus of major economic and environmental importance and its first step consists of the characterization of the valuable metal content. Wavelength dispersive X-ray fluorescence (WDXRF) analysis is compared with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the analysis of five samples of spent hydrodesulphurization (HDS) and hydrodemetallization (HDM) catalysts. The elements are considered for their economic interest (Co, Ni, Mo, and V) or for the problems that can arise when they are present in the sample in significant quantities (Al, As, P, Fe). First, the systematic comparison of the analysis of known synthetic samples was performed. The originality here is that the samples were first beaded with lithium tetraborate (Li2B4O7) for WDXRF analysis and then dissolved in hot HCl 6M for ICP-AES measurements. With this processing, we were able to clearly identify the origin of analytical problems when they arose. Second, the semi-quantitative protocol of WDXRF is compared with the quantitative procedure. Finally, the analysis of the spent catalysts is presented and the information gained by the systematic comparison of ICP-AES and WDXRF is shared. The interest of the simultaneous determination by the two techniques when such complicated heterogeneous matrices are involved is clearly demonstrated.

Transformation of Nickel Octaethylporphine in Hydrodemetallization Reactions

The transformation of nickel (Ni) porphyrins in hydrodemetallization (HDM) was investigated using 2,3,7,8,12,13,17,18-nickel-octaethylporphine (Ni-OEP) as the model compound, which was dissolved in a white oil. The HDM reactions were carried out in a high-pressure trickle-bed reactor over the oxidic and sulfided NiMo/Al2O3 catalyst. The molecular formulas of Ni compounds in the feed and hydrotreated products were characterized by positive-ion electrospray ionization (+ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The hydrotreated products were separated into two subfractions by silica gel chromatography. Molecular structures of Ni-containing intermediates were investigated by ultraviolet–visible (UV–vis) spectrometry, hydrogen nuclear magnetic resonance (1H NMR), and density function theory (DFT) calculations. The major Ni-containing intermediates of Ni-OEP were dihydrogenated (Ni-OEPH2) and tetrahydrogenated (Ni-OEPH4) porphyrins during the hydrotreating. The structure of ...

CoMoNi Catalyst Texture and Surface Properties in Heavy Oil Processing. Part II: Macroporous Sepiolite-Like Mineral

A set of novel CoMoNi hydrotreating catalysts supported on sepiolite-like mineral and modified by H3PO4 have been prepared and studied in hydrodesulfurization (HDS) and hydrodemetallization (HDM) of heavy Tatar oil with extremely high viscosity and sulfur content. Catalysts had a multiphase composition, represented by calcium/magnesium oxides, silicates, or phosphates, and were found to be of great interest for studying the role of support surface properties in heavy oil hydrotreating. For monitoring the catalyst properties, all the samples have been investigated by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XFS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), CO- and CDCl3-Fourier transform infrared (FTIR), mercury porosimetry, and N2 adsorption methods. The catalyst with a small phosphate content showed higher initial HDS conversion due to the more developed specific surface area, increased Lewis acidity, and better active component distribution; however, ...

Behaviors of metal compounds during hydrodemetallization of atmospheric residue

Behaviors of vanadium and nickel species during hydrodemetallization (HDM) were studied. A Kuwait atmospheric residue and its hydrodemetallized products from a pilot plant at mild and severe reaction conditions were characterized by using GPC coupled with ICP-MS and high temperature GC-AED after separation of them into saturates, aromatics, resins, and asphaltenes. It was found that the HDM reactivity of the vanadium species, especially those with lower molecular weight, was higher than that of Ni species, probably due to the higher polarity of the former than the latter. HDM of the vanadium species in the asphaltene was more difficult than that in the resin. The average molecular weight of metal species through higher temperature HDM was higher than that through the lower temperature HDM, although the metal removal at the higher temperature is higher.

CoMoNi Catalyst Texture and Surface Properties in Heavy Oil Processing. Part I: Hierarchical Macro/Mesoporous Alumina Support

A pair of mesoporous and hierarchical macro/mesoporous alumina-supported catalysts having distinct textural parameters have been chosen to elucidate the effect of texture on activity in hydrodesulfurization (HDS) and hydrodemetallization (HDM) of heavy tatar oil possessing extremely high viscosity and sulfur content. For monitoring catalyst properties, the samples have been investigated by XRD, XFS, XPS, EXAFS, SEM, TEM, FTIR, TPD-NH3, mercury porosimetry, and N2 adsorption methods. Among different factors such as support acidity, active component dispersion, and texture, the last one has been found to play the most significant role in this process. The hierarchical macro/mesoporous catalyst shows lower coking rate of the hydrotreated products, as well as higher HDS and HDM conversions despite its lower active component dispersion and decreased support acidity.

The Influence of Metal Deposits on Residue Hydrodemetallization Catalysts in the Absence and Presence of Coke

Spent hydrodemetallization (HDM) catalysts were collected from pilot-scale reactors with different time-on-stream, and they were treated with an extraction or regeneration method for further investigation. The fresh, spent, and regenerated samples were characterized systematically. Their catalytic performances were assessed using model molecules and Kuwait atmospheric residue as the reactants. Compared with conventional NiMo/Al2O3 catalysts, deposited metal sulfides had a notable increase in their HDM activity but an obvious decrease in their naphathelene hydrogenation activity. With short contact time, metal deposits accelerated residue HDM activity, and they were also involved in the loss of hydrodesulfurization (HDS) activity. At the initial stage of operation, HDM activity was reduced significantly due to the formation of coke. However, coke and metal deposits together contributed to the loss of HDS activity and the rapid fall of long period on-stream HDM activity.

Effect of pore size distribution (PSD) of Ni-Mo/Al2O3 catalysts on the Saudi Arabia vacuum residuum hydrodemetallization (HDM)

To study the effect of pore size distribution (PSD) of Ni-Mo/Al2O3 catalysts on the hydrodemetallization (HDM) activity, catalysts with different PSD were prepared using activated carbon and ammonium bicarbonate as pore-expanding agents and the HDM reaction was carried out in a high pressure trickle-bed reactor and Saudi Arabia vacuum residuum as the feedstock. The catalysts showed good activity of removing metal nickel (Ni) and vanadium (V) when they contain 10–20nm pores, but the catalysts with both 10–20 and >100nm pores have higher activity of removing metal V. The effect of PSD on the removal of different metal compounds were also studied by analyzing different metal compounds distribution in its hydrotreated products. Both Ni and V compounds of small molecular size in the methanol extract and middle molecular size in the dimethylformatmide (DMF) extracts can be easily removed on the catalysts. However, most of the large molecular V and Ni compounds in the toluene extracts were the most resistant to be removed in the vacuum residuum hydrodemetallization. Large molecular V compounds in the toluene extracts can be hydrodemetallized effectively on the catalysts with macropore size (>100nm) distribution. While catalysts with mesopore size distribution (10–20nm) shows a higher HDNi activity for the large molecular Ni compounds in the toluene extracts. Catalyst with both 10–20 and >100nm pore size distribution would be more appropriate for the Saudi Arabia vacuum residuum HDV and HDNi.

Distribution of Vanadium Compounds in Petroleum Vacuum Residuum and Their Transformations in Hydrodemetallization

The distribution of vanadium (V) compounds in the petroleum vacuum residuum (VR) and their transformations in hydrodemetallization (HDM) were investigated. V compounds in the VR and its hydrotreated products were extracted by different solvents in sequence to obtain methanol, dimethylformamide (DMF), and toluene extract fractions. The extracts were further separated into several subfractions using silica gel chromatography with various polar solvents. Positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses was used to characterize V compounds before and after HDM. The contents of V compounds in the methanol, DMF, and toluene extracts were 9.04, 22.19, and 62.58%, respectively. The V compounds in the methanol extract were mainly porphyrin with a molecular formula of CnHmN4V1O1, which were found undergoing side-chain cracking and could be removed through hydrotreating. CnHmN5V1O2 species were found in the DMF extracts, which can be easily converted or removed under severe reaction conditions. The V compounds in the toluene extracts were most resistant for hydrotreating, which were speculated as vanadyl porphyrins with complex substituent groups attached to the core porphyrin structures. The results indicated that a highly active HDM catalyst should possess a highly active hydrogenesis property and macropore size distribution for the different V compounds removed.

Improvement in hydrocracking activity of heavy oil upgrading catalyst by modifications to some specific properties of Y-zeolite

We have been developing zeolite catalysts for fixed-bed resid hydrodesulfurization (HDS) units. The catalysts, named R-HYC, show high resid hydrocracking (HYC) activity by increasing middle distillates and concurrently decreasing bottom fuel oil. To meet refinery demands for lower catalyst cost and improved HYC activity, the newest R-HYC has been developed as R-HYC12, showing more than twofold improved HYC activity compared with the previous R-HYC10, by means of modifications to some specific properties of Y-zeolite. A new sequence combining the developed R-HYC12 with the other, hydrodemetallization (HDM) and HDS catalysts has been proposed to achieve the best resid HDS unit performance.

Transformation of Sulfur Compounds in the Hydrotreatment of Supercritical Fluid Extraction Subfractions of Saudi Arabia Atmospheric Residua

Atmospheric residue from Saudi Arabia (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) experiments. Four extractable subfractions (SFEF 1–4) and an unextractable end-cut were obtained. SFEF 1–4 were subjected to a hydrotreating (HDT) test in a mini-tubular reactor packed with commercial hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts in order to determine the structural composition transformation of sulfur-containing compounds. Experiments were undertaken at a temperature of 360 °C, a hydrogen pressure of 14.7 MPa, a liquid hour space velocity (LHSV) of 0.25 h–1, and a H2/feed ratio of 650:1 (m3/m3). The SFEF subfractions and their products were subjected to analysis of their sulfur and nitrogen contents, using an ANTEK 7000S analyzer, and their saturates, aromatics, resins, and asphaltenes (SARA) compositions were analyzed using open column liquid chromatography. The detailed molecular composition of sulfur heteroatom species was determined by methylation, f...

Impacts of vanadium and coke deposits on the CO2 gasification of nickel catalysts supported on activated carbon from petroleum coke

One of the ways to dispose of spent carbon-based catalysts is gasification. In this study, the kinetics of CO2 gasification of Ni/activated carbon (AC) catalysts, produced from petroleum coke, were investigated at 700–900°C using a thermogravimetric analyzer (TGA). The catalysts were coked by exposure to ethylene at 400–600°C and/or impregnated with 3 or 8wt% vanadium, which is typically deposited during hydrodemetalization (HDM) of heavy oil. The gasification rates of all samples were 30–400 times greater than the rate of gasification of uncatalyzed (i.e., no metal) AC. Rate profiles as a function of conversion were different for all samples, which suggested that nickel was promoted/inhibited as a gasification catalyst in different ways depending on the composition of the sample. Transmission electron microscopy was used to analyze samples before and after gasification. The particle morphologies and chemical analysis (energy-dispersive X-ray) help to explain the different gasification behaviors. In particular, the nickel particles on the coked Ni/AC sample became encapsulated by graphite and sintered over time from 20nm initially to 150nm after 80% conversion (∼10min at 900°C). For the Ni/AC catalysts impregnated with vanadium, the AC support was decorated with ∼10nm nickel particles and wetted with a layer of vanadium after preparation at 500°C. After heating to 900°C, however, sintering of both metals was evident as well as the formation of new vanadium species including vanadium carbide in some areas. The interaction between nickel and vanadium lowered the initial gasification rate but also slowed the deactivation of the nickel during gasification.

Reactor Design of Microwave Assisted Demetallization of Heavy Crude Oil

In the recent years with the deeper exploiting of world-wide crude oil, the heavy and poor trend of which is aggravating, inducing the metal contents in the oil increasing rapidly. Vanadium (V) and nickel (Ni) are the most harmful metals to petroleum processing among these metals, which mainly displays poisonous effect to the catalysts of Fluid Catalytic Cracking (FCC) and hydrogenation. The commonly used technologies to remove these metals can be classified into physical method, chemical method and catalytic hydroprocessing method. Hydrodemetallization (HDM) is widely employed in industry. However, the products of HDM reactions can accumulate in the catalyst pores, causing the formation of deposits which end up obstructing those pores irreversibly, blocking access to the catalyst sites and leading to a progressive loss of catalytic activity. Thus the removal of nickel and vanadium from crude oil has become a challenge in petrochemical processing.This work focuses on these metals removal by using microwave heating technology. A suitable reactor was first developed through numerical simulation technology using COMSOL. It was found that the reactor with a radius of 20 mm shows good coupling with microwaves, and the optimized loading height achieved is 40 mm. Experiments of demetallization were then conducted for Venezuela crude oil using this reactor, the maximum removal rate of 72.4 % and 76.8 % were obtained for Ni and V respectively. However, by using this batch reactor, the temperature distribution is non-uniform within the treated material, a continuous system were therefore developed to overcome the un-even electric field distribution. The reactor was designed as a cylinder with the length of 500 mm, and different crude oil flow rates were simulated, good demetallization rate can be achieved using the same microwave operating conditions.

Application of a three-stage approach for modeling the complete period of catalyst deactivation during hydrotreating of heavy oil

Modeling the catalyst deactivation due to hydrodeasphaltenization (HDAsph), hydrodemetallization (HDM) and hydrodesulfurization (HDS) reactions with time-on-stream (TOS) was carried out by using a model that considers three deactivation stages: start-of-run (SOR), middle-of-run (MOR) and end-of-run (EOR). Experimental data of kinetics, intra-particle mass transfer and conversion affected by deactivation phenomena were obtained from laboratory scale reactor. Loss of activity was studied at constant operating conditions of temperature, pressure, liquid hourly space velocity (LHSV) and H2-to-oil ratio for a range of time-on-stream. It is found that different deactivation patterns are obtained depending on the considered reaction. It is predicted that catalyst exhibits higher rate of deactivation for HDS than for HDM at long TOS.

Characterization and analysis of vanadium and nickel species in atmospheric residues

Metal species (Ni and V) in as-received atmospheric residues (ARs) were characterized through conventional analysis methods as well as through gas chromatography-atomic emission detection (GC-AED) assembled with a high-temperature injector system (HT-GC-AED). The vanadium concentration in all ARs could be successfully measured by electron spin resonance (ESR) corrected with inductively coupled plasma-mass spectroscopy (ICP-MS). HT-GC-AED was attempted to confirm the characteristics of V and Ni species, from which at least five species of vanadium and six species of nickel in as-received ARs were identified, together with several shoulder peaks. In addition, HT-GC-AED analysis of product oils after hydrodemetallization (HDM) of ARs was investigated over both oxide and sulfide catalysts. This analysis provided evidence of a demetallization mechanism for the cracking of the alkyl group attached to the metal porphyrin structure over oxide catalysts. This mechanism contributes to the enhancement of HDM based on the staged reaction over the oxide (1st stage)-sulfide (2nd stage) catalytic system.

Hydrotreatment of two atmospheric residues from Kuwait Export and Lower Fars crude oils

Hydrodesulfurization (HDS) and the hydrodemetallization (HDM) of vanadium and nickel (HDV and HDNi) of two Kuwaiti atmospheric residues (ARs) from contrasting crudes (Kuwait Export, KEC; Lower Fars, LFC) were compared using the same commercial HDM and HDS catalysts in two stage flow reactors (HDM, first stage; HDS, second stage) under 18.5MPa of H2 at 370–395°C. The catalysts were stabilized by passing KEC-AR for 600h.The kinetic parameters of HDS, HDV, and HDNi were analyzed with the removal of sulfur and metals assumed to be 1.0 and 1.2 orders of reactions, respectively, in both reactors. The calculated rate constants were fitted to Arrhenius plots with reasonable linearity. The rate constants of HDS were similar in the first stage, whereas the rate constants of KEC-AR were certainly higher than that of LFC-AR in the second stage. HDS proceeded more rapidly over the HDS catalyst of the second reactor, but the activation energy was higher. The reactive sulfur species of both ARs were removed at similar rates in the first stage, and the differing refractory sulfur species of the two ARs were removed in the second reactor. HDV and HDNi of both ARs appear to progress similarly in both reactors, but the activation energy is higher in the second reactor. Demetallization appears saturated in the second reactor at higher reaction temperatures. Similar HDV and HDNi reactivities between the ARs suggest they share a similar mechanism in which the petroporphyrins must first be liberated from the asphaltene moieties of ARs and be exposed to the catalyst surface. This mechanism indicates that the most refractory metal species require higher activation energies before they are extracted as metal sulfides.The metal accumulation on HDM catalyst suggests that HDV and HDNi share similar reactivity, which contradicts previous notions. The discrepancy may be due to this study’s focus on the initial stage of the run.

Catalytic Performance and Synergetic Effect of Mo-V/Al2O3 in Residue Hy-drotreatment

Mo-V/Al 2 O 3 catalyst samples with different atom ratios of Mo/(Mo+V) were prepared by pore volume impregnation. The catalyst samples were characterized by Raman spectroscopy, H 2 temperature-programmed reduction, and high resolution transmission electron microscopy. The catalytic performance of Mo-V/Al 2 O 3 samples for model molecules (naphthalene) and for real feedstock (Kuwait atmosphere residue) was measured after sulfidation. Hydrogenation (HYD), hydrodemetallization (HDM), and hydrodesulfurization (HDS) were assessed. It can be concluded that Mo and V exhibited a synergetic effect in model molecules HYD and residue HDM reactions. Because the metals and sulfurs exist in different forms in residue and the V–S and V–Mo–S phases are more active for HDM than HDS, it is observed that the Mo-V/Al 2 O 3 catalyst exhibited higher HDM activity and lower HDS activity compared with the Ni-Mo/Al 2 O 3 catalyst.

Transient behavior of residual oil front-end hydrodemetallization in a trickle-bed reactor

A major concern of hydroprocessing operations is that the substantial heat release produces a sharp temperature rise along the reactor, especially under start-of-run (SOR) conditions with fresh catalyst, which may induce local overheating if reaction temperature is not properly controlled by a quenching system. In this context, it is of extreme relevance to understand reactor dynamics in order to establish an optimal start-up strategy. This work presents an analysis of the transient behavior of a front-end fixed-bed hydrodemetallization (HDM) process based on a three-phase dynamic reactor model. The mathematical model was constructed and fitted on the basis of bench-scale experiments. The model accounts for major hydroprocessing reactions, mass-transfer and catalyst deactivation. The model was applied to analyze industrial reactor performance subjected to process parameter variations. The simulations revealed that quenching must start before or as soon as the hydrocarbon front reaches the quench box in order to avoid overheating and that under SOR conditions special care must be taken into account to select the lowest possible feed temperature. It was determined that the safest start-up strategy was to stabilize the catalyst at low temperature followed by a soft temperature increase in order to meet product specifications in a short period of time.

Hydrodesulfurization and hydrodemetallization of different origin vacuum residues: Characterization and reactivity

This work presents an insight on the reactivities of different geographical origin residues in hydrotreatment processes. Hydrodemetallization (HDM) and hydrodesulfurization (HDS) experiments have been performed on different vacuum residue (Arabian Light, Buzurgan, Djeno and Ural) with commercial catalysts under industrial conditions. Depending on its origin each residue appears to have a specific behavior; however, some general trends can also be highlighted.One key reactivity parameter (both for HDM and HDS reactions) seems to be the size of residue molecules that depends strongly on its origin. In fact, diffusion limitations may occur, even in the HDM section.Hydrodesulfurization (HDS) reactions are not completely controlled by diffusion; the nature of chemical structures also appears to be an important parameter for reactivity. A better knowledge of the chemical structures is therefore still necessary to understand these different reactivities.

Hydrodemetallation (HDM) of nickel-5,10,15,20-tetraphenylporphyrin (Ni-TPP) over NiMo/γ-Al2O3 catalyst prepared by one-pot method with controlled precipitation of the components

In this work, a series of NiMo/γ-Al2O3 catalysts is prepared by one-pot method with controlled precipitation of AlCl3·6H2O, (NH4)6Mo7O24·4H2O and NiCO3·2Ni(OH)2·4H2O using urea and ammonium carbonate as additives. The molar ratio of urea to Al varied from 4.1 to 17.2 and the influence of this parameter on the surface and structural properties of the catalysts and HDM activity was studied. HDM of Ni-TPP was carried out in a batch reactor. The catalysts were characterized by BET, XRD, H2-TPR, DRS, XPS, EDS, FT-IR, TG–DTA and NH3-TPD. The results show that urea employed as additive not only improves the solubility of Mo and Ni salt, but also adjusts the hydroxyl concentration and facilitates the formation of molybdate and polymolybdate. The existence of residual chlorine may improve the dispersion of the particles containing Ni and Mo on the surface of porous Al2O3, enhance hydrogen spillover and the acidity of the catalyst. HDM activity varied with the amount of urea to a maximum at urea/Al of 12.3 with activity of 98%. The highest activity occurred at this ratio is mainly due to better porosity, well dispersed active particles, increased octahedral molybdenum/nickel oxides and proper acidity.