Hydrodesulfurization Of Diesel Research Articles

Regulating the coordination environment of surface alumina on NiMo/Al2O3 to enhance ultra-deep hydrodesulfurization of diesel

Herein, a set of NiMo/Al2O3 catalysts with distinct coordination state of surface alumina were design and prepared by a facile calcination strategy. Various characterization methods were employed to analyze the structural properties of NiMo/Al2O3 catalysts, and the catalytic performances of corresponding catalysts were tested for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The results indicate that the synthesized samples show uniform specific surface area (130 m2·g−1) and pore size (3.5 nm), but varying penta-coordinated aluminum content, which significantly influences the NiMo/Al2O3 catalysts’ surface acidity. Therein, NiMo/Al2O3-600 prepared by calcination at 600 °C exhibits the highest ratio of penta-coordinated aluminum species, which endows more abundant Brønsted acid than that of tetra- and hexa-coordinated aluminum counterparts, thereby substantially promoting the isomerization and direct desulfurization pathways of 4,6-DMDBT HDS, and thereafter considerably boosting the HDS performance of NiMo/Al2O3-600 with 94.5 % 4,6-DMDBT conversion, which is notably higher than that of NiMo/Al2O3-500 (74.4 %) and NiMo/Al2O3-700 (62.7 %).

Boosting ultra-deep hydrodesulfurization of diesel by tuning sulfidation degree of metals on NiMo/AlOOH catalyst

By using a room-temperature discharge-based sulphurization (RT-DS) process, we efficiently tune sulfidation degree of metal on γ-AlOOH-supported NiMo catalyst via simply changing feedstock amount for preparing catalysts, thus preparing a NiMoS/AOH-4 catalyst for hydrodesulfurization (HDS) of diesel. NiMoS/AOH-4 shows an excellent HDS performance, with S content of diesel being reduced from 18000 μg g−1 to 3 μg g−1 and without catalytic efficiency decrease after 1000 h reaction. Moreover, NiMoS/AOH-4 shows higher rate constant, higher turnover frequency but lower activation energy in HDS reaction, as compared with those on widely reported catalysts. The excellent HDS performance of NiMoS/AOH-4 is resulted from the appropriate sulfidation degree of Mo, which creates more abundant catalytic active Ni-Mo-S phases. RT-DS process for preparing NiMoS/AOH-4 proceeds in Ar at room temperature and atmospheric pressure, without using H2S and heating. This makes RT-DS process suitable for large-scale industrial applications to fabricate more efficient HDS catalysts.

Modifying the active phase structure of Ni2P/Al2O3 by Ga introduction for improved hydrodesulfurization of diesel

Modifying the structure of active phase is an effective protocol to improve the catalytic activity of hydrodesulfurization (HDS) catalyst. Here, a variety of mesoporous GaAlOx supports with various Ga doping amount were synthesized by a facile hydrothermal strategy. The corresponding Ni2P supported catalysts were fabricated via a conventional impregnation and temperature-programmed reduction method, and their catalytic performances for 4,6-DMDBT HDS were examined. The experimental analyses show that the introduction of Ga substantially influences the geometric and electrical structure of Ni2P active phase on Ni2P/GaAlOx catalysts. The metal-support interaction is effectively abated with the elevation of Ga doping amount, thereby increasing the d-electron density of Ni species and boosting the pre-hydrogenation (HYD) route, thereupon enhancing the HDS performances of corresponding Ni2P/GaAlOx catalysts. Therein, Ni2P/GaAlOx-0.50 exhibits the highest activity with 70.1% 4,6-DMDBT conversion because of the optimal morphology and percentage of active phase, as well as distinguished redox and acid property. Further increasing the Ga loading, however, inhibits the HDS activity of Ni2P/GaAlOx-1.0 catalyst due to the decrease in the fraction and dispersion of active phases. Therefore, this work may shine light on the understanding of structure–activity of HDS catalyst and thereafter the preparation of HDS catalysts with high efficiency in future.

Diesel Hydrodesulfurization and its Impact on the Fuel Market in Ecuador: A Review

This article examines the hydrodesulfurization process used to produce diesel with low sulfur content in Ecuador. The analysis covers the level of processing in the country, the quality of domestic diesel compared to other nations, and the technical and economic requirements of the process. It also explores the need to modify or upgrade catalysts to achieve deep hydrodesulfurization.. Unfortunately, the review found that sulfur content in Ecuadorian deposits is very high, with 3.53 MMkg produced in 2018. Despite improvements in the country’s refineries, diesel sulfur content has only been reduced to 110 ppm.. Ecuador regulates sulfur emissions through the Ecuadorian standard NTE INEN-1489 (2012). This norm classifies the fuel into three types, diesel #1 (3000 ppm), diesel #2 (7000 ppm), and premium diesel (500 ppm), following the use of diesel both in the industrial and transportation sectors. However, Ecuador seeks to adjust to countries with stricter regulations, such as the European Union. The standard that regulates sulfur emissions in this community is Euro VI, which limits the concentration to 10 ppm. One of the challenges in achieving international standards in the hydrodesulfurization units of the Ecuadorian refineries is to modify or improve the catalytic systems. Trimetallic catalysts, both supported and unsupported, can help overcome this challenge by decomposing the refractory molecules (e.g., dibenzothiophene and 4,6-dimethyldibenzothiophene) found in deep hydrodesulfurization. These catalysts can handle molecules that commonly used catalysts such as CoMo or MoW cannot. Therefore, proposals such as using trimetallic catalysts to achieve deep hydrodesulfurization levels are techno-economic options for Ecuador.
 Keywords: diesel, sulfur, Ecuador, hydrodesulfurization, refineries, catalyst.

Effective reduction of hydrogen consumption in ultra-deep hydrodesulfurization of diesel: Deep insights into the effect of thermodynamic limitations during hydrotreating

Reducing hydrogen (H2) consumption massively while ensuring the ultra-strict product quality is the most critical and extremely challenging issue in diesel hydrotreating process. In this work, the effect of operating parameters (including reaction temperature, reaction pressure, hydrogen/oil (H2/oil) volume ratio and liquid hourly space velocity (LHSV)) on H2 consumption were systematically studied first. Most importantly, the reduction of H2 consumption caused by temperature elevation was calculated upon satisfying the requirements of content of sulfur (S) and polycyclic aromatic hydrocarbons (PAHs) in the diesel quality standards (S≯10 mg/kg, PAHs≯7%) using feedstock with different properties. Results showed that H2 consumption was reduced by 23.1% when the temperature reached 401 °C (compared with temperature being 365 °C) using a diesel feed whose S content, N content and density were 9759.1 mg/kg, 147.1 mg/kg and 0.8626 g/cm3, respectively, while the impact on the catalysts activity, structure and coke deposition behavior was relatively little which was proven by the XPS, TEM, CAT-CS and TG-MS studies on the fresh and spent sulfide catalysts. The significant reduction of H2 consumption was attributed to the different thermodynamic behavior of S and aromatic compounds at relatively high temperature which led to a slightly decrease in hydrodesulfurization (HDS) conversion while a significantly drop in hydrodearomatization (HDA) conversion. This is a promising method to effectively reduce H2 consumption which can greatly benefit the future industrial applications in producing ultra clean diesel products with ultra-low H2 consumption.

Energy Basics of Catalytic Hydrodesulfurization of Diesel Fuels

Currently, Euro 5 (no more than 10 ppm sulfur content) and Euro 6 (less than 10 ppm sulfur content) diesel motor fuels are produced worldwide. High-quality diesel fuels are produced by removing sulfur compounds using a hydrodesulfurization process. This article is devoted to the study of hydrodesulfurization of diesel fuel containing 120 ppm of sulfur compounds in the presence of an Al-Ni-Mo-O catalyst with a 98% diesel fuel purification rate. According to the Langmuir–Hinshelwood–Panchenkov theory, a kinetic model of the process is developed with the calculation of the theoretical change in the entropy and enthalpy of the activation of the hydrodesulfurization process. The mathematical model, for the first time, takes into account the influence of the pressure of substances involved in the process on the transformation of sulfur-containing compounds. A mechanism for diesel fuel hydrotreating from sulfur-containing compounds is formulated using a generalized quantum-chemical principle. The hydrodesulfurization mechanism includes nine stages. The formulated mechanism and developed mathematical model of hydrotreating fully describe the reaction of the hydrodesulfurization of diesel fuel and show the possibility of regulating and controlling this industrially important process.

Modulating the active phase structure of NiMo/Al2O3 by La modification for ultra‐deep hydrodesulfurization of diesel

AbstractHerein, a series of mesoporous NiMo/LaAlOx with various La contents were constructed through a solvent evaporation‐induced self‐assembly protocol, and their catalytic activities were investigated for hydrodesulfurization (HDS) of 4,6‐DMDBT. It has been confirmed that the incorporation of La influences the electronic structure and morphology of NiMoS active phase. The lower amount of La (x ≤ 1.0 wt.%) could facilitate the formation of “Type II” NiMoS phase by weakening the interaction of Mo‐O‐Al leakage and promoting the sulfidation of both Mo and Ni species as well as increasing the ratio of “Type II” NiMoS phase, thereafter boosting the HDS performances. Further increasing La incorporation, however, leads to the generation of inactive NiSx phase and decrease of NiMoS active phase proportion, the HDS activities of corresponding catalysts were suppressed. NiMo/LaAlOx‐1.0 exhibits the highest activity for 4,6‐DMDBT HDS because of its moderate metal‐support interaction, optimal morphology and the largest proportion of “Type II” NiMoS active phase.

Promotion of the acidity and textural properties of NiMo/γ-Al2O3 catalyst by applying fluorine, boron and phosphorus in hydrodesulfurization of diesel fuel

Phosphorus, boron and fluorine were employed as promoters to synthesize the optimized γ-Al2O3 support and NiMo/γ-Al2O3 catalyst. Based on Response Surface Methodology, supports were synthesized with specified contents of promoters using wet impregnation method. Characterization and properties of the samples were determined through BET, TPD, XRD, TGA and EDX analyses. Moreover, the catalytic performance of the NiMo/γ-Al2O3 catalysts was evaluated at the temperature, pressure and LHSV of 350°C, 4.5 MPa and 1.1 h − 1, respectively. The results of experimental design indicated the effects of the promoters on the responses including pore volume, BET surface area and acidity. Based on the results, a model was designed to predict the optimal condition of synthesis. Then, the optimal support was synthesized using 3.99 wt.% of fluorine, 1.7 wt.% of phosphorus and its properties including acidity, BET surface area and pore volume were 1.28 mmolNH3/g, 276.95 m2/g and 0.63 cm3/g, respectively. Based on the developed model, it was concluded that boron-fluorine and phosphorus-fluorine interactions mostly affected the acidity and BET surface area, respectively. Then, properties and catalytic performance of catalyst were evaluated in the HDS process through diesel fuel feeding (sulfur content: 12,100 ppm) and its acidity was 2.2 mmolNH3/g and the efficiency of desulfurization and the coke of catalyst were 81% and 3%, respectively, which confirms better performance in comparison to a commercial catalyst.

Modeling of three-phase radial flow reactor for diesel hydrotreating

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

Comparison of the intraparticle diffusion of DBT and 4,6-DMDBT in HDS over different mesostructured silica-based catalysts

Achieving ultradeep hydrodesulfurization (HDS) of diesel necessitates HDS catalyst optimization. Understanding the catalyst pore structure effects on the diffusion behavior of the organosulfur compound benefits the proper design of the HDS catalysts with maximized apparent reactivities. In the present study, we controllably synthesized three mesoporous silica-based catalysts (NiMo/Zr-SBA-15, FDU-12, and MCFs) with similar intrinsic reactivities (∼13 × 10-4 and ∼ 5 × 10-4 mol•g−1•h−1 for DBT and 4,6-DMDBT HDS) but different pore structures. The diffusion behaviors of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in pore channels were systematically investigated via the reaction kinetic method. The pore channel/cage sizes rather than the pore mouth/window sizes dominated the intraparticle diffusion. The effective diffusion coefficient (De) decreased in the order of NiMo/Zr-MCFs (19.7 cm2•s−1) > NiMo/Zr-FDU-12 (18.2 cm2•s−1) > NiMo/Zr-SBA-15 (8.2 cm2•s−1) for DBT, while NiMo/Zr-MCFs (7.4 cm2•s−1) > NiMo/Zr-FDU-12 (4.4 cm2•s−1) > NiMo/Zr-SBA-15 (4.2 cm2•s−1) for 4,6-DMDBT. The corresponding correlation with pore size suggested that the intraparticle diffusion resistance can be greatly relieved when the catalyst pore/cage size is > 25x larger than the molecule size of the organosulfur-containing compounds. The findings present fresh opportunities for designing silica-based HDS catalysts for efficient HDS reaction.

Kinetics toward mechanism and real operation for ultra‐deep hydrodesulfurization and hydrodenitrogenation of diesel

AbstractAs the hydrodesulfurization (HDS) of diesel achieves ultra‐deepness, our understanding of its kinetics is still far from in‐depth. Therefore, herein, two lumped kinetic models for the ultra‐deep hydrodesulfurization (UHDS) and hydrodenitrogenation (HDN) are established based on experiments under a wide range of operating conditions. Meanwhile, a four‐lump kinetic model of the aromatic hydrosaturation (AHS) is erected. Our kinetic models disclose thermodynamic decisiveness in UHDS, which is unreachable beyond a temperature upper limit or a pressure lower limit. We also reveals the unexpected temperature dependence of organonitrogen inhibition to HDS, for less than 300°C this inhibition becomes even more potent despite nitrogen removal by HDN reactions. Subsequently, the HDS kinetics of total sulfur are deciphered as multi stages existed in the whole reaction coordinate. Accordingly, a four‐stage conceptual model involving mechanism and rate laws is proposed to better understand organonitrogen inhibition, thermodynamics, and kinetics in UHDS.

Ultradeep Hydrodesulfurization of Diesel: Mechanisms, Catalyst Design Strategies, and Challenges

With the increasingly strict diesel standards in the countries of the world, deep processing of diesel oil to ultralow sulfur levels is receiving more and more attention. This paper mainly reviews ...

Role of pore structure on the activity and stability of sulfide catalyst

Effect of pore structure on the activity and stability of sulfide phase in hydrodesulfurization (HDS) of diesel were systematically investigated. A series of alumina with different pore structure were prepared by calcining pseudo boehmite at different temperatures. Various characterizations suggested that the surface concentration of OH groups and Lewis acid sites generally decreased with calcination temperature. The properties of sulfide phase in fresh and spent catalysts were analysis by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The results showed that the concentration of CoMoS species was greatly decreased after the reaction while the average length of MoS2 slabs was substantially increased. The concentration of preserved CoMoS species was proportional to the average pore size of support indicating that the strip-off of Co from CoMoS phase can be reduced when the average pore size is larger. Furthermore, the activity evaluation showed that larger pore structure of support is beneficial for the intrinsic activity and stability of CoMoS phase in the HDS of diesel. The reason was partially attributed to that the pore with larger diameter can reduce the coke deposition on the catalyst so that increase the intrinsic activity and stability of CoMoS sites.

Deactivation of hydrodesulfurization catalysts during reactor startup

AbstractMetal sulfide catalysts for ultra‐deep hydrodesulfurization of diesel generally lose a fraction of their catalytically active sites during reactor startup. The underlying mechanisms are discussed. A laboratory diagnostic tool consisting of three probe molecules is developed for testing metal sulfide catalysts' start‐of‐run (SOR) activity maintenance. It is found that a significant fraction of the active sites on a commercial supported catalyst are deactivated permanently, but this is not the case with a bulk metal sulfide catalyst. The SOR deactivation of the bulk catalyst is completely reversible, while that of the supported catalyst is partially reversible. The diagnostic tool may provide a basis for developing a high‐throughput approach for evaluating and enhancing catalyst SOR stability, thereby increasing plant productivity.

Design Parameters for Diesel Hydro Desulfurization (DHDS)

Apart from all gaseous contaminants in air, sulfur dioxide is considered to be the principal pollutant. The emission of sulfur dioxide is generally caused by combustion of sulfur bearing fuels. This further gets converted into sulfuric acid in atmosphere as a result of its reaction with oxygen and moisture. This air borne acid is responsible to damage steel buildings, bridges and machinery. Hence there is a major need to decrease sulfur percentage in the environment in order to lead a better and healthy living. As we can see the world runs on energy, for which fossil fuels are the main constituents. As these all are the complex network of hydrocarbons, when they are combusted or utilized, the products or effluents are somewhat harmful to the atmosphere. Sulfur is one such effluent, which seriously harms the environmental conditions. So this has to be recovered up to appreciable levels. In India diesel is mostly utilized as fuel and it is up to 70%. So in order to reduce the sulfur content diesel is chosen as fuel oil. The reduction of sulfur is done by hydro desulfurization and the process is termed as diesel hydro desulfurization (DHDS). This is achieved by converting the mercaptane state sulfur to hydrogen sulfide (H2S) by reacting it with hydrogen alone on a cobalt molybdenum catalyst. By this the sulfur content is reduced from 1 wt% to 0.25 wt%. This is further reduced to 0.05 wt% using trickle bed reactors.

Smart Online Fuel Sulfur Prediction in Diesel Hydrodesulfurization Process

In the process industry, online operators usually adjust the entire production process in time according to changes in certain key indicators. However, it is difficult to directly obtain the value of key indicators due to the complex structure and the numerous processes of the process industry. This paper proposes a method to achieve high precision on-line prediction of key indicators in the process industry. The method first performs data preprocessing of multi-source heterogeneous time series data involved in industrial processes based on the professional knowledge, which not only keeps the prediction error within 10%, but also reduces the prediction time. Then a model framework is constructed based on LSTM neural network and the error correction algorithm is proposed to improve prediction accuracy based on real-time error, which directly causes the error to drop by 3%-5%. At the end, a set of multi-mode online training strategies and related trigger conditions are designed to perform predicting online. Diesel hydrodesulfurization is a typical case in the process industry. The effectiveness of the proposed method is empirically studied by applying its actual data sets. Through the comparison with other traditional well-known forecasting models, and models optimized by adjusting parameters, the experimental results demonstrate that the method can achieve the great prediction performance in terms of both accuracy and stability.

Nanoparticle catalyzed hydrodesulfurization of diesel fuel in a trickle bed reactor: experimental and optimization study.

This work focuses on the preparation, simulation, and optimization of the hydrodesulfurization (HDS) of dibenzothiophene (DBT) using a nanocatalyst. A homemade nanocatalyst (3 percent Co, 10 percent Mo/γ-Al2O3 nanoparticles) was used in a trickle bed reactor (TBR). The HDS kinetic model was estimated based on experimental observations over ranges of operating conditions to evaluate kinetic parameters of the HDS process and apply the key parameters. Based on these parameters, the performance of the TBR catalyzed by the nanocatalyst was evaluated and scaled up to a commercial scale. Also, the selectivity of HDS reactions was also modeled to achieve the highest yield of the desired hydrogenation product based on the desirable route of HDS. A comprehensive modeling and simulation of the HDS process in a TBR was developed and the output results were compared with experimental results. The comparison showed that the simulated and experimental data of the HDS process match well with a standard error of up to 5%. The best reaction kinetic variables obtained from the HDS pilot-plant (specific reaction rate expression, rate law, and selectivity) TBR have been utilized to develop an industrial scale HDS of DBT. The hydrodynamic key factors (effect of radial and axial dispersion) were employed to obtain the ratio of the optimal working reactor residence time to reactor diameter.

Cobalt‐promoted MoS2 nanosheets: A promising novel diesel hydrodesulfurization catalyst

AbstractMoS2 has been commonly used as a catalyst in hydrodesulfurization (HDS) of petroleum cuts in crude oil refineries. In this study, the synthesis of unsupported MoS2 and Co‐promoted MoS2 nanosheets produced from molybdenum oxide and thiourea is reported. The synthesized samples were characterized by using x‐ray fluorescence, x‐ray diffraction, Brunauer–Emmett–Teller (BET), temperature‐programmed reduction, thermal gravimetric analysis, and transmission electron microscopy methods, and then they were utilized for HDS of diesel through a fixed‐bed catalytic reactor. Results indicated that a cobalt promoter affected both the number and the performance of active sites of the molybdenum sulfides, and the activity of the promoted MoS2 catalyst was consistently higher than that of the MoS2 catalyst. More significantly, the activity of the promoted catalyst was slightly declined during 48 h continuous HDS reaction, which indicated the stability of this catalyst. Additionally, during 12 h of test run, the HDS activity of the promoted catalyst was about 60% higher than MoS2 one.

Catalytic kinetics for ultra-deep hydrodesulfurization of diesel

A set of rate laws for hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and aromatic hydrosaturation (AHS) of diesel was established to describe ultra-deep HDS in the sulfur concentration range from more than 10,000 ppm to below 10 ppm. High throughput experiments in micro-packed bed reactors with 2 mm inner diameter were conducted using NiMo/Al2O3 catalyst at temperatures from 300 °C to 360 °C, a pressure range of 4.4 MPa to 7.4 MPa, and liquid hourly space velocity (LHSV) between 0.75 h−1 and 12 h−1. To establish the rate laws, the sulfur content was divided into two regions, and the inhibition effects of H2S, nitrogen compounds, aromatics and the virtually refractory compounds were included. All kinetic parameters were estimated by combining genetic algorithm and least square regression to fit experimental data well. Finally, an appropriate operation interval of such reactor was obtained by using the developed model.

Influence of phosphorus content on properties and performance of NiW nanocatalyst supported on activated red mud in atmospheric diesel hydrodesulfurization

The influence of phosphorus promoter addition on structural properties and hydrodesulfurization activity of NiW nanocatalysts supported on activated red mud, called NiW/P-ARM, was studied at atmospheric pressure. Before red mud usage, it was treated by Pratt and Christoverson technique and then NiW/P-ARM nanocatalysts with different phosphorus loadings were prepared by impregnation technique. The prepared samples were characterized by XRF, XRD, FESEM, BET, FTIR and H2-TPR analyses. Base on the obtained results, XRF analysis indicated that activation process remarkably decreased Ca and Na content in the red mud. XRD results indicated the high dispersion of the tungstate, nickel and active phase (NiWO4) species on the surface of activated red mud support. FESEM analysis illustrated that all particles of NiW/P-ARM were less than 100 nm. TPR measurements revealed that phosphorus-promoted nanocatalysts had higher reduction potentials than nanocatalyst without promoter. The catalytic ability of synthesized nanocatalysts was investigated in a fixed bed reactor at atmospheric pressure and 380 °C using Iso diesel and light diesel as the reaction feeds. It was found that NiW/P-ARM with 1.5 wt.% prompter showed higher activity for hydrodesulfurization process and further addition of P promoter decreased the catalytic activity that may be due to the decrease in surface area or agglomeration particles.