Hydrodesulfurization Of Gasoils Research Articles

Tailoring NiMo-Based Catalysts for Production of Low-Viscosity Sustainable Hydrocarbon Bases for Drilling Muds from Secondary Gas Oils

This article presents the prospect of using the process of deep hydrodesulfurization and hydrodearomatization of secondary gas oils using highly active NiMo catalysts to obtain hydrocarbon bases for drilling fluids. Catalysts were synthesized using PMo heteropolyanions, citric acid, and diethylene glycol on alumina carriers with different pore volumes. This study showed that the concentration of the impregnating solution affects the composition and morphology of the active phase particles of the prepared catalyst, while the textural characteristics of the carrier influence the physicochemical properties and catalytic activity of the NiMo/Al2O3 catalysts. The catalyst that was synthesized using a carrier with the largest pore volume and an effective diameter of more than 7 nm exhibited the highest activity. It was demonstrated that the use of such a catalyst allows for the procurement of hydrocarbon bases for drilling fluids from mixtures of secondary gas oils at a hydrogen pressure of 15–20 MPa. This study has practical significance for the development of sustainable and economically efficient methods for the utilization of low-quality petroleum gas oils to produce high-margin environmentally friendly non-fuel petroleum products, as well as contributes to the development of economically efficient technologies for the utilization of petroleum raw materials.

Deep hydrodesulfurization of gas oils with high sulfur content: Experiment and kinetic modeling

The hydrodesulfurization of straight-run gas oils (SRGO-HS) with high content of sulfur (about 2 wt%) and its mixture with light coker gas oil (CGO) has been studied over CoMo/Al2O3 catalyst using a trickle bed down-flow reactor at the 335–365 °C, H2/HC − 300 Nm3/m3, LHSV − 0.8–2.5 h−1 and 3.5–5.1 MPa. The possibility of ultra-low sulfur diesel (<10 ppmS) production using feedstocks with sulfur content exceeding 2 wt% was demonstrated under conditions simulating industrial one. To predict the effect of process parameters on the amount of sulfur in products four kinetic models with different insight into the reactivity of individual S-containing compounds were considered. The first model is simplified kinetics based on power law rate equations, taking into account overall sulfur content, the second group includes LHHW type rate equations. The models 3 and 4 take into consideration the difference in the reactivity of sulfur-containing components. Model 3 classifies the total sulfur into two subgroups Se (easy reactive compounds) and Sr (refractory sulfur compounds - dibenzothiophene and its derivatives). In Model 4 the group Sr is divided into three more subgroups. Kinetic rate parameters i.e. frequency factors, apparent activation energies, and adsorption enthalpies, were estimated by fitting the experimental data obtained using the SRGO-HS/CGO feedstock to the models. All kinetic models predicted the experimentally determined conversions of sulfur with a relatively good accuracy (±20%). The kinetic models were verified by comparing the simulation results with the experimental data obtained using the other oil fractions (SRGO-LS) with lower content of sulfur (1.05 wt%). A better agreement was observed between the experiments and prediction by models 3 and 4.

Study for the production of ultra-low sulfur gas oils on a highly loaded NiMoW catalyst

Deep hydrodesulfurization (HDS) of gas oil has become one of the most important subjects in the production of fuels, as increasingly stringent quality standards for gas oil have been introduced all around the world. We studied the technical conditions (temperature, hydrogen pressure, liquid hourly space velocity, and H2/oil volume ratio) for the deep HDS of fluid catalytic cracking (FCC) and coking gas oils over a highly loaded NiMoW catalyst and compared its activity and the removal of the refractory dibenzothiophenes (DBTs) with those of a commercial NiMo/γ-Al2O3 catalyst and a highly loaded NiMo catalyst. The FCC gas oil, which had a lower sulfur content and simpler composition than the coking gas oil, was relatively easy to process. The coking gas oil and another FCC gas oil, of poor quality with more complex compositions, required more stringent reaction conditions. The sulfur distributions in gas oils hydrotreated to a level of 100, 50, and 10μg/g sulfur were investigated. 4-Methyldibenzothiophene could be totally removed when the coking gas oil was hydrotreated to a level of 50μg/gS. Only 4,6-dimethyldibenzothiophene and 2,4,6-trimethyldibenzothiophene were detected in the deep HDS to a level less than 10μg/gS. This is attributed to the steric hindrance of substituted-alkyls at the 4 and/or 6 positions of DBT. The highly loaded NiMoW catalyst had a higher activity than a highly loaded NiMo catalyst and a commercial NiMo/γ-Al2O3 catalyst, and was more suitable for the production of ultra-low-sulfur gas oils.

Development of improved catalysts for deep HDS of diesel fuels

Deep hydrodesulfurization (HDS) of gas oils continues to attract research interest due to environmental-driven regulations which limit its sulfur content to 10–15 ppm in several countries. This paper highlights some of the recent studies conducted at King Fahd University of Petroleum and Minerals to develop improved HDS catalysts. The first study was focused on the effect of Co/(Co + Mo) ratio in CoMo/Al2O3 catalysts on HDS pathways of benzothiophene (BT) and dibenzothiophene (DBT). Co/Co + Mo ratio exhibited significant influence on the direct desulfurization (DDS) pathway, but showed no influence on the hydrogenation pathway. A Co/Co + Mo ratio of 0.4 exhibited optimum promotion effect of Co for HDS by DDS route and hence overall HDS. The second study investigated the effect of phosphorus addition on simultaneous HDS reactions and their pathways. The results indicate that phosphorus modification of CoMo/γ-Al2O3 catalysts resulted in enhancement of HDS due to increased dispersion of MoO3 and the maximum enhancement was achieved with 1.0 wt % P2O5. Enhancement of HDS rates was in the following order: 4,6-DMDBT (51 %) > 4-MDBT (38 %) > DBT (26 %). In the third approach, a series of NiMo catalysts supported on Al2O3-ZrO2 composites containing 0–10 wt % ZrO2 was synthesized, characterized and evaluated for deep desulfurization of gas oil. An increase of 1.3–2.5 times increase in HDS activity at 320–360 °C was observed due to reduced interaction between Al2O3 and the active metals. A correlation was found between the enhancement of hydrogenation activity of sulfided catalysts and the reducibility of their oxide precursors.

Comparison of P-containing γ-Al 2O 3 supported Ni-Mo bimetallic carbide, nitride and sulfide catalysts for HDN and HDS of gas oils derived from Athabasca bitumen

Phosphorus containing γ-Al 2O 3 supported bimetallic Ni-Mo carbide, nitride and sulfide catalysts have been synthesized from an oxide precursor containing 12.73 wt.% Mo, 2.54 wt.% Ni and 2.38 wt.% P and characterized by elemental analysis, pulsed CO chemisorption, surface area measurements, X-ray diffraction, temperature-programmed reduction and DRIFT spectroscopy of CO adsorption. DRIFT spectroscopy of adsorbed CO on activated catalysts showed that carbide and nitride catalysts have surface exposed sites of Mo ø+ (0 < ø < 3) and Mo δ+ (0 < δ < 2) sites respectively, and these sites are susceptible to sulfidation with H 2S/H 2 mixture at 370 °C. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of the bimetallic Ni-Mo carbide, nitride and sulfide catalysts were compared against commercial Ni-Mo/Al 2O 3 catalyst in a trickle bed reactor using light gas oil and heavy gas oil derived from Athabasca bitumen in the temperature range 340–370 and 375–400 °C respectively at 8.8 MPa. The gradual transformation of Ni-Mo carbide and nitride phases into Ni-Mo sulfide phases was observed during precoking period, and the formed Ni-Mo sulfide phases enhanced the HDN and HDS activities of carbide and nitride catalysts. The γ-Al 2O 3 supported Ni-Mo bimetallic sulfide catalyst was found to be more active for HDN and HDS of light gas oil and heavy gas oil than the corresponding carbide and nitride catalysts on the basis of unit weight.

Experimental and Kinetic Studies of Aromatic Hydrogenation, Hydrodesulfurization, and Hydrodenitrogenation of Light Gas Oils Derived from Athabasca Bitumen

In this work, a systematic experimental and kinetic study of hydroprocessing of light gas oils (LGOs) such as vacuum LGO (VLGO), atmospheric LGO (ALGO), and hydrotreated LGO (HLGO) using NiW/Al2O3 and commercial NiMo/Al2O3 catalysts has been conducted. Experiments were performed by varying temperature from 340 to 390 °C, at a constant pressure and liquid hourly space velocity of 11.0 MPa and 0.6 h-1, respectively. H2/feed ratio was maintained at 550 mL/mL throughout the experiments. Appreciable hydrogenation of aromatics (AHYD) was achieved by the NiW/Al2O3 catalyst at low temperatures and at high severities of hydrotreating. However, the hydrogenation activity of NiMo/Al2O3 was superior to that of the NiW/Al2O3 catalyst. For hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities, higher conversions of 95−98.8 and 96−99 wt %, respectively, were attained for the commercial NiMo/Al2O3 catalyst throughout the temperature range studied. Simulated distillation of the feed showed that VLGO contained the most complex and heaviest compounds followed by HLGO and ALGO. Diesel selectivity in both ALGO and HLGO increased with hydrotreating temperature, but in the case of VLGO, it decreased with temperature. Kinetics studies showed that dearomatization of the HLGO feed was the most difficult, followed by ALGO and then the VLGO. Kinetics of ALGO and VLGO were best described by a pseudo-first-order reaction mechanism while the 1.3 power law kinetics worked well with HLGO.

Performance of spent sulfide catalysts in hydrodesulfurization of straight run and nitrogen-removed gas oils

After the test run of several months two kinds of commercial catalysts (NiMo/Al 2O 3 and CoMo/Al 2O 3) were examined in hydrodesulfurization (HDS) of straight run (SRGO) and nitrogen-removed gas oils, at 340 °C under 50 kg/cm 2 H 2. Hydrogen renewal between stages was attempted to show additional inhibition effects of the by-products such as H 2S and NH 3. Spent NiMo/Al 2O 3 and CoMo/Al 2O 3 catalysts showed contrasting activities in HDS and susceptibility to nitrogen species, according to their catalytic natures, compared to those of their virgin ones. HDS over spent NiMo/Al 2O 3 was significantly improved by removal of nitrogen species, while that over spent CoMo/Al 2O 3 was much improved by H 2 refreshment. The activity for refractory sulfur species such as 4,6-dimethyldibenzothiophene was reduced more severely than that for the reactive sulfur species such as benzothiophenes over spent catalysts. The effects of both two-stage hydrodesulfurization and nitrogen-removal were markedly reduced over the spent NiMo when compared with those over virgin NiMo one. The acidity of the catalysts was correlated with the inhibition susceptibility by nitrogen species as well as H 2S and NH 3. Spent catalysts apparently lost their activity due to the carbon deposition, which covered the active sites more preferentially. The spent NiMo catalyst carried more deposited carbon with larger C/H ratio and nitrogen content. Higher acidity was found to be present on the NiMo catalyst, but this was greatly decreased by the carbon deposition. Additionally, the reactivity of nitrogen species in HDS was briefly discussed in relation to the acidity of the catalyst and its deactivation by carbon deposition.

Hydrodesulfurization of gasoils over NiMo/Al 2O 3–H(or Ni)NaY zeolite hybrid catalysts

A series of hybrid catalysts constituted by NiMo/Al 2O 3 mixed with HNaY or Ni(1.45)NaY zeolite were prepared, and their activities in the hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of an untreated gasoil and a commercially prehydrotreated gasoil were compared to those of conventional NiMo/Al 2O 3. The influence of HNaY zeolite loading on the activity of the hybrid catalysts was investigated with both untreated and hydrotreated feeds. The addition of increasing amounts of HNaY to NiMo/Al 2O 3 resulted in lower activities for the HDS and HDN of the untreated gasoil, being the decrease in HDS similar for all hybrid catalysts and in HDN proportional to the HNaY content. These catalysts have a very stable activity for HDS and decaying activity for HDN of the untreated gasoil. With the prehydrotreated gasoil, a small promoter effect (∼20%) for initial HDS activity was observed with the addition of 5 wt.% of HNaY to NiMo/Al 2O 3, and then a marked decrease with further HNaY loading. However, all catalysts, included NiMo/Al 2O 3, suffered a rapid deactivation under the reactions conditions used, which was attributed to a desulfurization of the catalysts caused by the low conversion level obtained and, therefore, a low H 2S partial pressure in the reactor. The addition of Ni(1.45)Y zeolite to NiMo/Al 2O 3, decreased slightly the HDS and HDN of the untreated gasoil and increased by a factor of about three and nine times the initial and stationary, respectively, HDS of the prehydrotreated gasoil. Analysis of the relative distribution of sulfur species in products explains the observed synergy and the role of the Ni(1.45)NaY zeolite in the deep HDS over hybrid catalysts.

Charge transfer complexes between tetranitrofluorenone and polyaromatic compounds from gasoil: a combined DFT and experimental study

A new method has been recently developed for the hydrodesulfurization of gasoils based on the formation of charge transfer complexes. This method is highly selective towards the removal of alkyldibenzothiophenes from other aromatic compounds present in gasoils. Total energy calculations based on density-functional theory have been performed to study the complexation phenomenon and clarify its high selectivity. DFT calculations improve the understanding of the process and they are also useful for the design of more efficient acceptor derivatives for the desulfurization process. Five charge transfer complexes between a given acceptor and five representative donor compounds present in gasoils have been studied. Three main criteria have been used to characterize the optimized complexes: their complexation energy, their geometry and their electronic structure. The decomposition of total energy showed that the main contribution to the complexation energy comes from the Pauli repulsion and the electrostatic interactions. Hence the charge transfer complexes are not only ruled by charge transfer but also by electrostatic contributions. However, the selectivity of the complexation phenomenon is controlled by the orbital interactions.

00/00689 Reaction order and role of hydrogen sulfide in deep hydrodesulfurization of gas oils: consequences for industrial reactor configuration

00/00689 Reaction order and role of hydrogen sulfide in deep hydrodesulfurization of gas oils: consequences for industrial reactor configuration

00/00688 Preparation and characterization of candidate catalysts for deep hydrodesulfurization of gasoils. Sulfidation and acidity characteristics of supported Ni/W and Ni/Mo catalysts

00/00688 Preparation and characterization of candidate catalysts for deep hydrodesulfurization of gasoils. Sulfidation and acidity characteristics of supported Ni/W and Ni/Mo catalysts

Reaction order and role of hydrogen sulfide in deep hydrodesulfurization of gas oils: consequences for industrial reactor configuration

Deep desulfurization of gas oils to sulfur levels below the currently legislated 0.05 wt.% is rendered difficult by the presence of refractory species as part of a spectrum of sulfur compounds that have widely differing reactivities. This distribution of reactivities is reflected in a high apparent order (approximately 2) in total sulfur for a plug–flow reactor. The consequences of this apparent kinetic behaviour for required catalyst volumes and axial profiles of hydrogen sulfide in a reactor for deep desulfurization are examined. Hydrogen sulfide proved to strongly suppress the conversion rate of sulfur compounds, including that of the refractory alkyl substituted dibenzothiophenes crucial for deep desulfurization. A number of process configurations are discussed that avoids or reduces the problem of hydrogen sulfide inhibition. These include several variants of a two-step process in which the bulk of sulfur is removed in a first step, followed by further desulfurization down to low sulfur levels in a second step with fresh, H 2S-free hydrogen gas. The theoretically most ideal option, that of operation with countercurrent flow of oil and gas, is not possible in packed beds of the usual catalyst particles because of the occurrence of flooding at industrially relevant fluid velocities. Some novel reactor concepts based on special structured packings or monoliths that allow such countercurrent operation are presented.

Preparation and characterization of candidate catalysts for deep hydrodesulfurization of gasoils. Sulfidation and acidity characteristics of supported Ni/W and Ni/Mo catalysts

The uptake of 35 S -labelled H 2S, the thiophene hydrodesulfurization (HDS) activity in pulse and flow system and the acidity measured by infrared (IR) band intensities of adsorbed pyridine were studied after various treatments over NiW/amorphous silica–alumina (ASA), NiW/Al 2O 3 and NiMo/Al 2O 3 catalysts. The Fourier Transformation Infrared (FTIR) measurements indicated that the NiW/ASA catalyst contained some Brönsted and much more Lewis acid sites, whereas less Brönsted acid sites were observed on the alumina supported samples. The concentration of Brönsted and Lewis acid sites decreased after sulfidation. The amount of total sulfur uptake of NiMo/Al 2O 3 catalyst was about twofold of the one of NiW samples. The sulfidation level of the catalysts was much lower in the pulse system than in the flow one and also the thiophene conversion was much lower on NiW catalysts in the former setup than in the latter system. A band was detected in the radiochromatogram of NiW/ASA catalyst during desorption of H 2S in the pulse system which was attributed to weakly adsorbed H 2S on the Brönsted acidic sites. This weakly adsorbed H 2S hindered the isomerization of n-butane in the flow system but not in the pulse system.

Hydrodesulfurization of coker feed

This article presents data on the hydrodesulfurization of heavy coker gasoils, a distillate from the tar obtained in the thermal cracking of resid, heavy vacuum gasoil (350-520/sup 0/C), and blends of these stocks in various ratios. A single-pass flow unit was used with a fixed bed of commercial alumina-cobaltmolybdenum catalyst. Hydrodesulfurization of the gasoils was studied at temperatures of 360-400/sup 0/C, feedstock space velocities of 0.7-1.5h/sup -1/, a pressure of 5 MPa, and a hydrogen circulation ratio of 800 m/sup 3//m/sup 3/. The heavy gasoils obtained in destruction processes were hydrodesulfurized in blends with heavy vacuum gasoil (350-520/sup 0/C) in weight ratios of 70:30 and 50:50. It is determined that dilution with the heavy vacuum gasoil (350-520/sup 0/C) has very little effect on the conditions for hydrodesulfurization of a feedstock of secondary origin. The degree of hydrodesulfurization shows a slight increase only when the distillate from the cracked tar is diluted in a 50:50 weight ratio. When the coker gasoil is diluted with a light vacuum gasoil (350-478/sup 0/C), the same degree of desulfurization is achieved with a 70:30 dilution ratio and a hydrotreating temperature of 380/sup 0/C. The primary coke-forming components in the examined feedstocks are polycyclic aromatic hydrocarbonsmore » and resins. Includes 3 tables.« less