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The TEM results revealed that asphaltene tangled structure has nearly disappeared after severe thermal treatment due to alkyl side chain removal, which is also confirmed by the Raman and FTIR analyses.

This study is carried out to synthesize a supported hydrodemetallization (HDM) catalysts. The supports are prepared by mixing peptized alumina with activated carbon. The compositions of the supports (0–75 % activated carbon in alumina), the stepwise drying, and the calcination under the moderate flow of air in a rotating furnace produced supports with large pore volume, which respectively enhanced the metal storage capacity and minimized diffusion limitations of large hydrocarbon molecules (i.e., asphaltene). The presence of carbon in support also helped in reducing coke and metal depositions on pore-mouth and catalytic sites. The optimum textural and mechanical properties of the support are obtained when the carbon-alumina weight ratio is 1:1. The catalysts are synthesized by impregnating the support extrudates with low content of Mo active metal with or without Co or Fe as a promoters metals. FeMo supported catalyst showed better synergy than the CoMo and NiMo catalysts. The FeMo supported catalyst composition (10–75 wt% carbon) indicated best HDM results for an optimum pore diameter. The activity and the stability of the catalysts were evaluated using residual oil and heavy crude oil (Ku crude), which respectively have metal content (Ni and V) of 212 ppm and 567 ppm. The catalyst contains meso- macro-pores along with bimodal-type pore structure and has textural properties such as an average pore diameter of 5–1000 nm, a total pore volume of 0.3–1.5 ml/g, and moderate surface area of 50–200 m2/g.

The impact of thermal cracking reaction on asphaltene structure and morphology has been investigated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural and morphological changes at a microscopic level were monitored by comparing the parent asphaltenes from different vacuum residues (VRs) to their corresponding thermally treated asphaltenes, obtained from the by-product pitch after thermal treatment. The SEM analysis indicated that the asphaltene aggregates extracted from atmospheric residues have smooth and rough surfaces with agglomerate particles and bright inclusions. The SEM images of asphaltene aggregates that are extracted from the pitch samples after mild cracking demonstrated cleavage fracture morphology with obvious reduction in inclusions sizes and intensities. The TEM analysis, on the other hand, indicated that the asphaltenes from residual oils have tangled structures, with edges similar to a cauliflower. The tangled structure is mainly credited to the alkyl side-chains that impede the aromatic sheets from stacking. At mild cracking (400 °C), the asphaltene began to exhibit well-ordered layer structures near the edges due to the rupture of the alkyl side-chains. However, the tangled structure has been preserved in the interior of the sample. As the reaction severity increases (415 °C), the stacking of aromatic sheets became more evident even in the sample interior. At the most severe cracking condition (430 °C), an obvious reduction in the cluster diameter has been observed, which mainly resulted from the reduction in the number of aromatic sheets per stack.

A number of alumina supports were synthesized by using a homogeneous sol–gel precipitation technique. The role of organic additive and its effect on surface active sites as well as textural properties have been analyzed. The support was characterized by N2 adsorption–desorption, X-ray diffraction (XRD). fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric and differential scanning calorimetry analysis (TGA/DSC). The surface functional group characterization was carried out by using isopropanol (IPA) as a probe molecule for the acid–base site identification. The solid was used as support for a catalyst and to compare active metal site genesis as a supported catalyst where thiophene reaction was carried out, and activity was compared with the commercial alumina support. The characterization results indicated that the pore enlarging agent (poly (ethylene) glycol, PEG) improve not only textural properties but also significantly modified surface properties, which was evident during the hydrodesulfurization (HDS) of thiophene.

Recently, significant changes in petroleum sources have been observed where light crude sources are becoming heavy or extra heavy, containing a large number of contaminants (S, N, metals, asphaltene, etc.), and producing a significant fraction of the bottom of the barrel (residue) after distillation. Thus, the future crude slate is a vital issue facing refiners to invest strategically in processing larger quantities of sourer crude. Due to the feedstock, refinery process operations must advance and include next-generation processes and catalysts to fulfill the demand and supply. The qualities of these products primarily meet or satisfy stringent environmental regulations. On the other hand, traditional light crude oil refineries have seen drastic changes into heavy crude oil, which present enormous challenges to the refining industry to process heavier crude oils. The global trend indicated that the world oil refining industry has to face several challenges in demand as well as supply. At the same time, refineries are expected to be under a great deal of pressure to accomplish the market demand for high-quality fuels (i.e., gasoline and diesel). The global demand for diesel fuels is increasing, while fuel oil demand is decreasing. The fuel composition and their efficiency (energy content) remain a decisive factor for the price and the communally acceptable parameter. This review will focus primarily on the relationship between the various parameters of composition, physicochemical properties of crude oil, and their impact on hydroprocessing.

In recent years, the oil market has witnessed high volatility due to unstable demand and supply. Considering the price volatility and stricter environmental regulations, there is a possibility of a decline in the demand for transportation fuels, which will force refiners to explore alternate ways to improve the yield of high-value products, to keep their margins high. In recent years, demand for petrochemicals has witnessed tremendous growth, and there is a dynamic market for olefins and monomeric (building blocks) hydrocarbons. The emerging virgin crude-to-chemicals (CTC) technology can provide an opportunity for integrating operational refineries with chemicals. The integration of refining with the production of high value-petrochemicals can lead to a framework that will add value to both sectors (upstream and downstream). Integration has been proven to be environmentally driven by utilizing various refinery waste and by-products. The importance of thermal and catalytic processes in the integrated refinery is high, particularly the process of integrated gasification combined cycle (IGCC) that generates electricity and by-product as a feedstock for chemicals. On the other hand, high demand for petrochemicals indicated a predictable growth in recent years, mainly driven by the commodity product requirement. Hence, this review critically discusses the current oil price variation, heavy oil production, and technical challenges to convert heavy crude to chemical (c-t-c) or petrochemical (c-t-p). Moreover, considerable flexibility is emphasized as a holistic approach to deal with unconventional feedstock (using thermal and catalytic methods) to produce sustainable feed for the chemical and petrochemicals.

This chapter discusses the effect of support, especially TiO2 and Ti containing mixed oxides with special reference to distillate fuel hydrotreating. Support plays important role in many heterogeneous catalytic reactions including hydrodesulfurization and related reactions. Use of Γ–Al2O3 based support is not only due to favourable catalytic properties but also due to suitable physico-chemical and mechanical properties. SiO2 supported Mo and C0M0 catalysts are one of the earliest catalysts that received considerable attention not so much for their commercial potential but for the contrast they provide in comparison with γ-Al2O3 supported catalysts. TiO2 supported systems exhibited higher activities compared to Al2O3 supported Mo and CoMo systems. However thermal instability, low surface area and poor mechanical properties came in their way of commercial exploitation. The TPR studies indicated that mixed oxide supported catalysts are intermediate in reduction behaviour between Al and Ti. This chapter suggests that both Ti and Al ions are involved in binding the supported molybdenum.

An effect of organic nitrogen compounds on deep hydrodesulfurization catalyst (CoMo/Al2O3) has been carried out using micro-flow reactor at 5 MPa hydrogen pressure, 1.5 h−1 liquid hours space velocity, and 330 to 380 °C temperature. The experiments were conducted in two steps; at first, prepare nitrogen free Kuwaiti straight run gas oil (SRGO) while in the second step is to test hydrotreating (HDT) catalytic activities using synthetic diesel feed to achieve ultra-low sulfur diesel (ULSD). Hence the role of nitrogen compounds and their effect on HDS activity was studied with nitrogen-free SRGO and spiked (added indole and quinoline), which indicated an apparent tendency of strong inhibition effect by basic nitrogen on deep HDS process. Indeed, inhibition and deep HDS conversion are also dependent on the H2 partial pressure and its dissociative species (i.e., Hδ+ and Hδ−). It is expected that basic nitrogen compounds can easily consume Hδ+ ions during hydrotreating which is assumed to be the rationale behind the stronger inhibition of the hydrogenation function. It was found that quinoline has a more noticeable adverse effect than indole, particularly at a lower temperature. HDS activity results indicated that the adsorbed nitrogen species showed more acceptable behavior at a lower temperature while at high-temperature inhibition effect is not very significant, which could be because of the adsorption nature of nitrogen species.

This review focuses on sustainability challenges in oil and gas development, which established a literature-based framework for clean fuel predominantly with reference to MENA region, and identifies the trend for oil and natural gas usage and their effect on the technologies and its human development index. What are the missing gaps for fossil fuel in order to obtain clean fuels, and how can those gaps identify and resolve the environmental issue by using fossil fuel as an energy source? The findings indicate that fossil fuel will remain the major source of energy and transportation fuels, which can be effectively refined using catalytic refining processes along with the CO2 capturing and storage techniques in order to reduce global warming. Sustainable development refers to basic information about the social, economic, and environment aspects of human activity. Among the main driving elements of sustainability are the progress made in technology and the utilization of energy resources. Worldwide, the use of renewable energy sources may increase but has moderate progress. Thus, the fossil fuels are playing a vital role in the energy world but require efficient refining processes to produce high-quality clean fuels for transportation as well as energy production.

Among various CO2-mitigation technologies, membrane-based technology has offered a more energy efficient and eco-friendly process for CO2 separation from large emission sources, in order to reduce CO2 emission level into atmosphere. In general, polymeric and inorganic membranes have been used in gas separation processes, but each has its own pros and cons. Currently, membrane research has addressed the trade-off limitations of membranes in different ways through fabrication of new type of mixed matrix membranes (MMMs) by incorporation of inorganic particles as fillers into polymer matrices. The performance of MMMs depends on textural properties of fillers, molecular sieving effect and membrane–penetrant interactions. The main challenges in the fabrication of MMMs is selection of fillers, which controls the gas separation characteristics of membranes. In this review, the influences of fillers like zeolite, carbon, and metal organic framework in MMMs fabrication and their CO2 permeability and CO2/CH4 and CO2/N2 selectivity were compiled from recent reports. Further, a new protocol is introduced for screening of fillers, which will helps to development of new fillers as well as for fabrication of new MMMs with high CO2 separation capacity.

The main objective of this work is to determine the effect of thermal cracking on asphaltene molecular structure by using nuclear magnetic resonance (NMR). The NMR is used to identify and quantify the structural parameters and the functional groups, which subsequently helped in deriving a hypothetical average structure for the asphaltene molecules. The NMR analysis revealed a number of valuable findings and developed a better understanding about the nature of structural changes that asphaltene molecules undergo during the thermal cracking of vacuum residues (VRs). For instance, the polyaromatic structure of asphaltene in the parent VRs consists of peri-condensed cores interlinked through aliphatic bridges. This peri-condensed polyaromatic core converts to cata-condensed polyaromatic as the reaction severity increases. The NMR analysis confirmed that the observed reduction in the average molecular weight of asphaltene molecules, as reaction severity increases, is mainly due to cracking of the saturated par...

The hydrodemetallization (HDM) activity and the stability of FeMo supported catalysts have been investigated during the hydroprocessing of heavy crude oil. The prototype FeMo catalysts were developed in this study as guard-bed catalysts. Such type of front catalyst is frequently used in complex hydrotreatment to protect the more vulnerable subsequent catalysts. Various prototype supports were synthesized in this study to produce different textural properties. Such textural properties were generated and optimized by using different support compositions (0−75 wt.% activated carbon in alumina) and following a certain support pretreatment methodology for pore expansion. Both the support composition and the pretreatment methodology have significantly contributed in developing an optimized HDM catalyst with a large pore volume and a distinctive bimodal pore structure. The large pore volume substantially improved the metal retention capacity, while the bimodal pore structure remarkably reduced the diffusion limitation, allowing the large hydrocarbon molecules (i.e., asphaltene) to reach the inner catalytic sites to enhance their conversion rates. The presence of carbon in the catalyst support, even after calcination, considerably reduced coke and metal depositions on pore-mouths and catalytic sites. The textural and the mechanical properties of support indicate that the optimum composition is attained when the carbon-alumina ratio is 1:1 (50/50 wt.%). The role of textual properties on catalyst stability was investigated by comparing fresh and spent catalysts. The characterization of spent catalysts indicates that the bimodal type of pore has stable performance with time-on-stream (TOS).

The main objective of this study is to provide an in-depth analysis that reveals the impact of thermal treatment on the different functional groups that exist in asphaltene molecules. This contribution is important to further understand the nature of changes that take place in asphaltenes during distillation and thermal cracking processes. A slight increase was observed in the aromatic −CH groups, compared to aliphatic −CH groups, as crude oil is processed to atmospheric and vacuum residues. A slight decrease was also observed in the intensity ratio between methylene and methyl groups (CH2/CH3) with distillation, which suggests a decrease in the average length of alkyl side chains for asphaltene molecules. The Fourier transform infrared (FTIR) results also suggest the possibility of thiophenic compounds oxidation during the atmospheric and vacuum distillations. More obvious differences were noted between asphaltenes exposed to thermal cracking, separated from the pitch samples, and their parent asphaltene...

Various heavy oils with different amounts of asphaltenes were hydrotreated with a commercial NiMo catalyst in batch reactor at 100 kg/cm2 hydrogen pressure, 400 °C temperature, 750 rpm stirring rate and 4 h reaction time. Fresh, spent and regenerated catalysts were recovered after reaction, washed with toluene, and analyzed by textural properties. Data of adsorption-desorption isotherms were used to calculate hysteresis areas, whereby a semi-quantitative approach to determine the degree of catalyst deactivation is proposed. By comparison of hysteresis areas of spent and fresh catalysts it was confirmed that the higher the asphaltene content in feed, the faster the catalyst deactivation.

The present study aims to develop an eco-friendly methodology for the recovery of nickel (Ni), molybdenum (Mo), and vanadium (V) from the refinery waste spent hydroprocessing catalyst. The proposed process has two stages: the first stage is to separate alumina, while the second stage involves the separation of metal compounds. The effectiveness of leaching agents, such as NH4OH, (NH4)2CO3, and (NH4)2S2O8, for the extraction of Mo, V, Ni, and Al from the refinery spent catalyst has been reported as a function of reagent concentration (0.5 to 2.0 molar), leaching time (1 to 6 h), and temperature (35 to 60°C). The optimal leaching conditions were achieved to obtain the maximum recovery of Mo, Ni, and V metals. The effect of the mixture of multi-ammonium salts on the metal extraction was also studied, which showed an adverse effect for Ni and V, while marginal improvement was observed for Mo leaching. The ammonium salts can form soluble metal complexes, in which stability or solubility depends on the ...

Sulphidation due to sulphur bearing gases such as H 2 S with refinery materials is a serious problem in the petroleum industry. Measuring instruments such as thermocouples (TCs) used in the refining industry to measure and control temperatures in critical areas are also susceptible to sulphidation when exposed to the sulphur bearing process media. The paper presents an investigation carried out to understand the failure of a TC in a temperature programmed sulphidation (TPS) reactor. The TC was incorrectly installed in the reactor without the external protective sheath. As a result of incorrect installation, the TC was exposed directly to sulphidizing gas of H 2 S (5% H 2 S in H 2 ) at a programmed temperature profile (150–1000 °C). The qualitative H 2 S consumption with a change in temperature indicated that the H 2 S reaction with the TC started at about 400 °C, which corresponds to a physical phenomena on the metal surface. The TPS result indicated that the first H 2 S consumption peak in the range 600–780 °C corresponded to the surface phenomena, mostly due to the H 2 S chemisorption reaction on the metal surface. However, the bulk phenomena of sulphidation or corrosion require diffusion as a function of further increase in temperature, hence a mass consumption peak in the range of 780–900 °C is recorded. Detailed investigations of corroded TC were carried out using TPS, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The investigation revealed that the failure of the TC was due to catastrophic sulphidation taken place as a result of incorrect installation. The results further suggest that the TPS technique has the potential to study the sulphidation behavior of metals and alloys.

The main objective of this study is to determine the effect of thermal cracking on asphaltene molecular structure. Hence, n-heptane insoluble fractions were precipitated and collected from three different vacuum residues and their thermally decomposed products. The X-ray diffraction (XRD) analysis provided an understanding of the macro-structure of the asphaltene molecule and revealed the impact of thermal stress on its structural parameters. The XRD analysis indicated that the layer distance between the aromatic sheets (dm) and the distance between aliphatic chains and naphthenic sheets (dγ) were not substantially affected by the cracking severity. Furthermore, the average diameter of the aromatic sheet (La) has not changed much with thermal cracking. This finding was associated with a constant number of aromatic rings in the aromatic sheet (NOar). The cluster diameter (Lc), on the other hand, decreased in size as the severity of cracking increased. The decrease in cluster diameter is due to the loss of aliphatic carbon in the side chains as well as the decrease in the number of aromatic sheet per stack (M).

Different mixed-oxide supports were synthesized using homogeneous co-precipitation methods. Alumina–silica, alumina–titania, and alumina–zeolite supports were prepared and then impregnated with Mo (or W) and Co (or Ni) in order to evaluate their behavior in the dibenzothiophene hydrodesulfurization. Supports and supported catalysts were characterized by atomic absorption and textural properties. The conversion of model compounds (tetralin, 1-methylnaphthalene, and decalin) was investigated with the aim of understanding ring opening reaction over the support in presence of hydrogen. The model test reactions for support as well supported sulfide catalysts were carried out in a batch reactor at 4 MPa and 340 °C. Conversion of cyclo-compounds showed that decalin had the highest conversion followed by 1-methylnaphthalene and tetralin when using a silica–alumina supported catalyst. The hydrodesulfurization results as a function of support variation indicated that high acidity of support has positive effect on the hydrogenolysis of C S bond breaking. Thus, it is inferred that a balance between metal sites of hydrogenation and cracking of the support is critical in order to synthesize a bifunctional catalyst for deep hydrodesulfurization where sulfur removal as well as cetane improvement are mandatory.

During the heavy oil hydroprocessing, a decrease in catalytic activity with time-on-stream (TOS), is due to the metal and carbon deposition on the catalysts. In this investigation, spent catalysts were obtained from the Maya heavy crude hydrotreating unit, as the processing conditions were close to the industrial practice. The catalysts were unloaded after considerable activity decrease, considering the initial activity as base activity. The spent catalysts were characterized by pore size distribution, SEM-EDS, TEM and 13C solid state NMR. Results indicate that catalysts were deactivated mainly due to the deposition of metal and carbon. The sources of deactivation were identified along with the location of foreign species by analyzing the deposited species on the spent catalysts. The nature of the coke and its compositions were derived from 13C CP/MAS and CP/MAS with dipolar dephasing NMR experiments. The wide range of analysis of spent catalysts specify that the catalyst pores were plugged during the heavy oil processing. The deactivation of catalysts were not only due to the carbon deposition but also due to the deposited metal sulfide (VxSy, NixSy) over the existing (CoMoS) active sites. It appear from the results that considerable amount of deactivation is irreversible and non-regeneratable (i.e., metal deposition). Hence catalyst deactivation during heavy oil hydrotreating (HDT) is a function of metal and carbon deposition during time-on-stream. The metal deposition on spent catalysts, e.g. vanadium is on the surface, while Ni distributed deeper into the pore of the catalysts. The removal of Ni and V showed different behavior, which was attributed to an oxygen atom presence to vanadium and its influence on the vanadium porphyrin structure.

This study investigates the recovery of Mo, V, and Ni metals from the industrial spent hydroprocessing catalyst. These catalysts are not viable to regenerate mainly due to the metal deposition. The study was carried out on industrial spent residue hydroprocessing (ARDS) catalysts that contained high levels of metals. In the extraction process, metals were recovered through pyrometallurgical and hydrometallurgical routes. The possibility of recycling of total spent catalyst (TSC) was studied using various steps such as deoiling, drying, grinding, sieving, and decoking. In the subsequent steps, the digested spent catalysts were treated with acid–base reactions in order to separate the various components of the spent catalyst. Using various leaching reaction conditions such as acid–base concentration, reaction pH in aqueous as well as organic mediums was studied. The metals were leached out in the solution while the alumina support was recovered as bulk solid in the form of boehmite. The recovered alumina is...

Pure and mixed oxides (Al 2 O 3 , ZrO 2 , Al 2 O 3 –MgO, Al 2 O 3 –SiO 2 , Al 2 O 3 –TiO 2 , and Al 2 O 3 –ZrO 2 ) were prepared by homogeneous delayed precipitation. The synthesized supports were impregnated by incipient wetness method to obtain CoMo catalysts. Both supports and catalysts were characterized by N 2 physisorption, X-ray diffraction, among other techniques. Acid–base properties were studied with isopropyl alcohol and cumene decomposition. It was possible to assess qualitatively that nature of Al–Si and its respective catalyst was mainly acidic. Conversion of isopropyl alcohol leads to the dehydration products, mostly propylene with a low amount of di-isopropyl ether and acetone. The CoMo/Al 2 O 3 –SiO 2 catalyst showed the highest conversion during cumene cracking. CoMo/Al 2 O 3 –SiO 2 catalyst also was the most active during thiophene hydrodesulfurization followed by CoMo/Al 2 O 3 –TiO 2 catalyst.

International audience; NiMo/SiO2-Al2O3 mixed oxide supported catalysts were investigated for hydroprocessing of heavy crude oil at moderate reaction conditions. Hydrodesulfurization (HDS), hydrodemetalization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions were studied as function of time-on-stream (TOS). The results indicated that HDS of crude oil corresponds to the number of active metal sites (sulfide phases) present in the catalyst, HDN is enhanced when the catalyst presents a combination of well dispersed sulfide phases and weak to moderate acidity. HDM presented a complex behavior indicating that it is affected significantly not only by the dispersion of the sulfide phase but also by the porosity and acidity of the catalyst. As expected, for HDAs both acidity and textural properties are important. The stability of the catalyst with time-on-stream was affected by coke and metals deposition. The supports and fresh catalysts were characterized by nitrogen physisorption, SEM-EDX, and FT-IR of CO and pyridine adsorption. The results confirm that NiMo/SiO2-Al2O3 catalysts are a good option for the hydrotreatment of heavy oils and that the method used here for support preparation can tune the formation of meso- or macro-porosity and the type and strength of the catalyst acid sites. (C) 2012 Elsevier B.V. All rights reserved.

Mixed oxides (Al―Si, Zr―Si, Mg―Si) were synthesized by the sol―gel method at different gelation times. The synthesized supports were impregnated by the incipient wetness method to obtain Ni-Mo, Co―Mo, and Ni-W supported catalysts. Both the supports and catalysts were characterized by N 2 physisorption for determining textural properties, and their catalytic activities were tested with isopropyl alcohol (2-propanol) and cumene decomposition in order to evaluate their acid―base properties. According to the obtained products, it was possible to assess qualitatively that Al―Si and Zr―Si supports and their respective catalysts were mainly acidic. In the case of NiMo/AlSi catalyst, high conversion during cumene cracking particularly at higher temperatures was observed. Cracking activity results indicated that surface acidity predominated due to Bronsted acid sites, which are mainly dependent on the support composition as well as their preparation methods. Conversion of isopropyl alcohol leads to the dehydration products, typically propylene with a very low amount of di-isopropyl ether or acetone. NiMo/AlSi catalyst was evaluated for cumene cracking and its kinetic parameters were obtained by applying the Langmuir-Hinshelwood model. The activation energy was found to be 27.75 kcal mol ―1 while the heat of adsorption calculated with the Van't Hoff equation was ―14.15 kcal mol ―1 taking into account a single-site surface reaction.

Sulfur content of diesel fuel has been cut down to ultra low levels by environmental regulation in many countries with the aim of reducing diesel engine's harmful emissions and improving air quality. As a result, research on the production of ultra low sulfur diesel (ULSD) has gained enormous interest in the scientific community worldwide. The renewed interest in ULSD research is driven by the need, to have a comprehensive understanding of the various factors influencing deep desulfurization of diesel to the ultra low level as well as to find cost-effective ways for ULSD production. This review discusses the recent advancement on ULSD production from both scientific and applied point of view. The key fundamentals and the factors influencing the removal of the least reactive sterically hindered sulfur species from diesel feedstocks are reviewed and discussed in detail. Latest development in deep HDS catalyst and the scientific basis for the improvements in the activity of the new generation HDS catalyst are presented. Advancement in the deep HDS process technologies is reviewed and various options available for revamping and modifying the existing low sulfur diesel HDS units for ULSD production are described highlighting the importance of catalyst selection and hydrogen consumption issues. Special attention has been paid to the progress in the alternative (non-hydrogenation) process concepts and technologies that are being developed for ULSD production.

Thermal analysis of asphaltenes and resins from heavy crude was carried out to understand the way in which they decompose to form coke. Sediments extracted from hydrotreated crude were also analyzed. It was found that asphaltenes produced 47 wt.% of coke, resins 9 wt.% of coke, and sediments decompose quickly toward coke giving the highest yield (66 wt.%). In the case of asphaltenes and resins a free radicals based mechanism is operating when labile points in alkyl chains are broken leading to condensation reactions. Thermal analysis of sediments obtained from hydrotreated crude revealed that they have high tendency to form coke. A non-isothermal technique using various heating rates was applied to study kinetics of asphaltene cracking toward coke formation. An iso-conversional method based on Friedman's procedure was used to calculate the reaction kinetic parameters from thermogravimetric analysis during asphaltene cracking and a set of activation energies and pre-exponential factor was obtained as the reaction progresses. Activation energy ranged from 29.2 to 52.4 kcal/mol.

Large pore diameter Al2O3-SiO2 acidic mixed oxide supports were prepared by using homogeneous co-precipitation method. The acidic properties of supports (oxide) and supported catalysts (sulfided) were chemically probed with cumene cracking (HCR) into propane and benzene at atmospheric pressure and 400 °C. NiMo supported hydroprocessing catalysts activities were also evaluated with heavy Maya crude oil. The use of acidic support is to optimize yield of high octane gasoline components, i.e. selective cracking of complex crude oil molecule. The supported fresh and spent catalysts were characterized by means of N2 adsorption–desorption and SEM–EDX spectroscopic techniques. The results point out that deactivation takes place mainly at the entrance of pore due to coke deposition, while the depositions of vanadium and nickel sulfides mainly depend on the diameter of the pores. The results also indicated that the deactivation due to carbon deposition is carried out at initial hours of the crude oil processing. The large pore diameter catalyst contains higher amounts of deposited species, which are distributed proportionally along the extrudate radius, while for smaller pore diameter catalyst the deposition mainly occurs on the extrudate surface.

Asphaltenes from Maya crude and its hydroprocessed oils at different reaction conditions were precipitated and studied by scanning and transmission electron microscopy (SEM and TEM). In order to better understand the changes occured in asphaltene structure during hydroprocessing the crude oil fractionation procedure with solvents was used to separate asphaltenes based on their solubility properties. Different asphaltene morphologies were observed depending on the mixture of solvents used for fractionating asphaltenes and reaction conditions at which crude oil was hydroprocessed. A comparison between asphaltenes from hydroprocessed and pure Maya crude oil was carried out on the way to distinguish morphological changes at microscopic level. It was observed that removal of alkyl chains during hydroprocessing makes asphaltenes suffer a rearrangement in solid state favoring stacking of aromatic cores as determined by TEM. SEM microscopy allowed different fractions of asphaltenes for seeing that they are constituted by agglomerate particles, porous structures, and smooth surfaces.

The hydrodesulfurization and cracking activity of NiMo sulfided catalysts supported on Al-, Ti-, and Zr-modified SBA-15 was measured using the HDS of thiophene and cracking of cumene as model reactions. The results were used to analyze the effect of each heteroatom on the two reactions, and the existence of a relationship between HDS activity and the catalysts acid properties. The HDS activity of sulfided NiMo catalysts supported on Al-, Ti-, or Zr-modified SBA-15 depends significantly on the nature of the heteroatom used to modify the SBA-15 support. The HDS activity trend displayed by the catalysts was NiMo/Al20-SBA-15 > NiMo/Ti20-SBA-15 > NiMo/Zr20-SBA-15. This trend was similar for the cumene cracking reaction. The results indicate that Bronsted acidity favors hydrodesulfurization.

Defined hexagonal cylindrical pore structure SBA-15 material was synthesized as support for hydrotreating catalysts. The stability of the mesoporous material under acid and basic environments commonly used to prepare hydrotreating catalysts was investigated. The effects of the acid and basic treatments on the stability of SBA-15 and NiMo/SBA-15 catalysts were evidenced by different characterization techniques such as N2 adsorption–desorption, X-ray diffraction (XRD), Raman Spectroscopy and high resolution transmission electron microscopy (HRTEM). Supported NiMo/SBA-15 catalysts prepared by pore volume co-impregnation in acidic, neutral and basic solutions of the Ni and Mo precursor salts were characterized to evaluate the textural and structural changes caused by the method of preparation. Characterization of the support after accelerated stability tests indicates large deterioration of the SBA-15 structural order at basic pH. The characterization results of oxide and sulfided catalysts indicate, for the catalysts prepared at high pH, an increasing presence of β–NiMoO4 phase in the oxide catalysts, and a relatively lower population of MoS2 in the sulfided catalysts. The activity of the different catalysts evaluated in the thiophene hydrodesulfurization reaction was higher for the catalysts prepared at low pH.

Three different supports were prepared with distinct magnesia–alumina ratio x = MgO/(MgO + Al 2 O 3 ) = 0.01, 0.1 and 0.5. Synthesized supports were impregnated with Co and Mo salts by the incipient wetness method along with 1,2-cyclohexanediamine- N , N , N ′, N ′-tetraacetic acid (CyDTA) as chelating agent. Catalysts were characterized by BET surface area, Raman spectroscopy, SEM-EDX and HRTEM (STEM) spectroscopy techniques. The catalysts were evaluated for the thiophene hydrodesulfurization reaction and its activity results are discussed in terms of using chelating agent during the preparation of catalyst. A comparison of the activity between uncalcined and calcined catalysts was made and a higher activity was obtained with calcined MgO–Al 2 O 3 supported catalysts. Two different MgO containing calcined catalysts were tested at micro-plant with industrial feedstocks of heavy Maya crude oil. The effect of support composition was observed for hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions, which were reported at temperature of 380 °C, pressure of 7 MPa and space-velocity of 1.0 h −1 during 204 h of time-on-stream (TOS).

The effect of phosphorus content and preparation methods is studied in this present investigation. Three different methods are employed for preparation of catalysts. The catalysts are characterized by pore size distribution, X-ray diffractogram and temperature programmed reduction. Thiophene hydrodesulfurization (HDS), cumene hydrocracking (HC), gas oil HDS and Maya heavy crude HDS and hydrodemetallization (HDM) activities are performed. It is found that specific surface area gradually decreases with P loading. The addition of phosphorus increases the formation of polymolybdate species which are more active for hydrotreating reaction. It is also observed that reducibility of these species also increases with P loading. However, at higher P loading the crystalline MoO3 is formed at the expense of these multilayer polymeric molybdates. The increment in the activity is more in the catalyst prepared by co-impregnation method. The activity increases with P loading up to 1 wt% P content. At higher loading the activity decreases. It is also noted that P inhibits coke formation on the catalyst during hydrotreating of heavy crude oil. Phosphorus can also modify the Bronsted acidity of the catalyst and hence cumene hydrocracking activity slightly increases.

Al2O3–SiO2 mixed oxide has been investigated as a support for hydrotreating catalyst with variation of its composition [Si/(Si + Al) = 0.06, 0.12, 0.31, 0.56, 0.78] and its interaction with the surface active metals (NiMo). The composition of support and surface species (NiMo) of catalysts were characterized by specific surface area, atomic absorption, SEM-EDX, XRD, temperature programmed reduction (TPR), Raman analysis, scanning electron microscopy (STEM) and transmission electron microscopy (TEM). Incorporation of SiO2 in Al2O3 promotes a weak interaction between the active phases and particularly catalyst that predominated with SiO2 content. The oxide and sulfided catalysts characterization indicated that the effect of support is responsible to form different catalytic sites. Crystallization of MoO3 phases and a relatively longer crystal of MoS2 in the sulfided catalyst were attributed to an increasing SiO2 content in the support. The catalytic behavior of the NiMo supported catalysts is explained in terms of structural changes on the surface due to the support and active metal interactions. The activity of the different catalysts evaluated in the thiophene hydrodesulfurization reaction was higher for the catalyst having lower SiO2 content in the support.

This study presents an effect of zeolite with alumina as a support for heavy oil hydroprocessing. The high surface area, moderately acidic meso- and macro-porous support was prepared with the mixing of alumina and ultra-stable Y zeolite (US-Y). The micro-structure and the composition of the zeolite crystals formed in the bulk of the alumina were examined by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and there were two main crystal phases homogeneously distributed in it. A CoMo sulfide supported catalyst is evaluated for hydroconversion of Maya heavy crude oil at moderate pressure conditions. The combination of ultra-stable zeolite and alumina is able to produce bi-modal type of pores in the catalyst which may contribute to a better combination of hydrodesulfurization (HDS), hydrodemetallization (HDM) and the selective cracking of asphaltene over the acidic catalysts. The characterization of spent catalysts can help as an assistance for the selection of optimum catalyst properties along with the reactor bed length and type of catalyst pore in each bed. The strapping reaction condition indicated that the acidic catalyst for heavy oil can be used more effectively at lower temperature. An increase in temperature showed that the HDM and hydrogenation of asphaltenes (HDAs) conversions are more affected than HDS and HDN. These results indicate occurrence of a thermal cracking of complex molecules like asphaltene and metal porphyrins, which is confirmed by the gaseous selectivity of the hydrocarbons.

Ni–Mo/Al 2 O 3 –MCM-41 supported catalysts have been investigated for modification of MCM-41 by using sol–gel alumina incorporation method. Different catalysts were synthesized with variation of Si/Al molar ratios of 10, 50, 100 and 200. High specific surface area ordered meso-porous solid (MCM-41) was synthesized by using organic template method. In order to modify the low acidity of silica solid, the surface of MCM-41 was modified by incorporation of alumina. The surface acidity of solids modified significantly with variation of alumina content in the supports. The sol–gel method of alumina incorporation was used, which does not modify extensively the pore characteristics of MCM-41 material during the preparation of Al 2 O 3 –MCM-41. The X-ray diffraction intensities indicated that alumina as well as MCM-41 were present in the synthesized supports. Additionally, the hydrothermal stability of the Al 2 O 3 –MCM-41 materials was maintained up to 873 K using sever conditions like 100% water vapor stream. The catalytic activity of the catalysts was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). Selectivity was oriented mainly to the production of biphenyl (BP) and for high Si/Al ratios toward cyclohexylbenzene (CHB) and showed a higher conversion and better selectivity to hydrogenation (cyclohexylbenzene).

The environmental regulation pressure is being increased to reduce precursors of pollution contaminants (sulfur, nitrogen, and aromatics) in fuels to lower levels. There are various processes to upgrade heavy and extra-heavy crude oils, such as solvent deasphalting, thermal conversion, catalytic conversion, distillation, and hydroprocessing. Hydroprocessing not only upgrades the crude oil but also produces synthetic crude oil that has a lower impurities content and a higher liquid yield of products. The fuels upgrading currently is achieved in refinery hydroprocessing units using different new-generation catalysts, along with several modifications of process conditions such as multistage reactors, type of catalyst loading, and reactor internals. However, it has been widely recognized that, for deep removal of these contaminants by hydroprocessing, research must be more oriented to the catalyst developments, rather than the process conditions. Actual commercial catalysts are based on well-known and studied...

The influence of H2S (0–559.6 kPa) on Maya crude hydrotreating is investigated in an integral fixed bed up-flow micro reactor. The added H2S inhibits hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) while asphaltene conversion (HDAs) remained almost unaffected. On the other hand, a promotional effect is found for hydrodemetallization (HDM). The observed variation in HDS and HDM conversions suggests a dual nature of catalytic sites particularly at high partial pressure of hydrogen sulfide. The promotional effect for HDM may be interpreted in terms of adsorption of metal–porphyrins on Bronsted acid sites (sulfhydryl group), which enhance hydrogenation of metal–porphyrins and convert them into the corresponding metal–chlorin structure in a first step of reaction. The final step in the HDM is essentially hydrogenolysis (metal–nitrogen) and requires the presence of an anionic vacancy (CUS). The conversion of asphaltene is also depending on the acidic nature of sulfided catalyst that is remaining either uninhibited or slightly enhanced with H2S.

Hydrodesulfurization (HDS) of dibenzothiophene (DBT) was carried out in a batch reactor at 3.3 MPa and 340 °C. Sulfided catalysts showed a wide range of activity variation as a function of support composition, which established that sulfided active phases strongly depend on the nature and composition of support. The incorporation of MgO, SiO 2 , TiO 2 and ZrO 2 with γ-Al 2 O 3 alters the nature of active phase interactions on the support surface. Therefore, these oxides play a structural promoting role to the support contribution and its interaction towards the active metal geometry. Different preparation methods of catalysts were carried out by using different additives during the impregnation. It is demonstrated that co-impregnation method found better activity than sequential impregnation. The urea additive prepared catalyst provides promising activity compared with other chelating agents. An Al 2 O 3 –B 2 O 3 mixed oxide supported catalyst was tested at high pressure with real feed (Maya heavy oil diluted with hydrodesulfurized diesel). The mixed oxide supported catalyst showed rapid deactivation with time-on-stream than the alumina supported catalyst that may be due to an enhancement in acidic sites. The activity results demonstrated that the number of catalytic sites is a combination of support composition, additive, impregnation pH, drying and calcinations of catalysts.

The term hydroconversion is used to signify processes by which molecules in petroleum feedstocks are split or saturated with hydrogen gas while tumbling boiling ranges and impurities content from petroleum fractions. Hydroprocessing is a broad term that includes hydrocracking, hydrotreating, and hydrorefining. To meet the gradual changes in petroleum stipulate, in particular a reduced demand for heavy fuel oil, advanced technologies for residue hydroprocessing are now extremely necessary. A refining process is needed for treating heavy petroleum fractions (atmospheric or vacuum oil residue) in the presence of catalysts and hydrogen at high pressure. In this article the different technologies for residua processing: thermal, catalytic fixed and ebullated types of hydroconversion are reviewed and discussed. A possibility of combining the advantages of these technologies together with suitable catalyst with enhanced and controlled cracking activity is also analyzed.

CoMo and NiMo supported Al 2 O 3 catalysts have been investigated for hydrotreating of model molecule as well as industrial feedstock. Activity studies were carried out for thiophene and SRGO hydrodesulfurization (HDS) in an atmospheric pressure and batch reactor respectively. These activities on sulfided catalysts were evaluated as a function of promoter content [M/(M + Mo) = 0.30, 0.34, 0.39; M = Co or Ni] using fixed (ca. 8 wt.%) molybdenum content. The promoted catalysts were characterized by textural properties, XRD, and temperature programmed reduction (TPR). TPR spectra of the Co and Ni promoter catalysts showed that Ni promotes the easy reduction of Mo species compared with Co. With the variation of promoter content NiMo catalyst was found to be superior to CoMo catalyst for gas oil HDS, while at low-promoter content the opposite trend was observed for HDS of thiophene. The behavior was attributed to the several reaction mechanisms involved for gas oil HDS. A nice relationship was obtained for hydrodesulfurized gas oil refractive index (RI) and aromatic content, which corresponds to the Ni hydrogenation property.

The support effect was analyzed for hydrodesulfurization CoMo catalysts prepared with EDTA as the chelating agent. Supports with different isoelectric points, γ-Al2O3, Al2O3–MgO, and SiO2, were used. Different sequences of EDTA, Co, and Mo impregnation were used to analyze whether the sequence of addition affected catalytic activity. Changing the order of addition of Co, Mo, and EDTA produced only a small effect on the catalyst HDS activity. The simultaneous impregnation of Co, Mo, and EDTA led to higher HDS activity than sequential impregnations. In contrast, changing the support nature produced important variations in catalytic activity, following the increasing order: Al2O3 < SiO2 < Al2O3–MgO. It was found that the changes in HDS activity with the type of support are related to different levels of promotion of Mo by Co, and to changes in the sulfidation patterns induced by different interactions of the active phase precursors with each support.