Kening Sun,Xixi Ma,Ruijun Hou

Beijing Key Laboratory for Chemical Power Source and Green Catalysis,School of Chemistry and Chemical Engineering,Beijing Institute of Technology,Beijing 100081,China

Keywords:HDS Trickle-bed reactor Heterogeneous model Kinetics Siberian crude oil

ABSTRACT Hydrodesulfurization(HDS)of sour crude oil is an effective way to address the corrosion problems in refineries and is an economic way to process sour crude oil in an existing refinery built for sweet oil.Siberian crude oil transported through the Russia-China pipeline could be greatly sweetened and could be refined directly in local refinery designed for Daqing crude oil after the effective HDS treatment.In this study,the HDS of Siberian crude oil was carried out in a continuous flow isothermal trickle-bed reactor over Ni-Mo/γ-Al2 O3 .The effects of temperature,pressure and LHSV were investigated in the ranges of 320–360°C,3–5 MPa and 0.5–2 h?1,keeping constant hydrogen to oil ratio at 600 L?L?1.The HDS conversion could be up to 92.89%at the temperature of 360°C,pressure of 5 MPa,and LHSV of 0.5 h?1,which is sufficient for local refineries(>84%).A three phase heterogeneous model was established to analyze the performance of the trickle-bed reactor based on the two-film theory using Langmuir-Hinshelwood mechanism.The order of sulfur component is estimated as 1.28,and the order of hydrogen is 0.39.By simulating the reactor using the established model,the concentration of H2 ,H2 S and sulfur along the catalyst bed is discussed.The model is significantly useful for industrial application with respect to reactor analysis,optimization and reactor design,and can provide further insight of the HDS of Siberian crude oil.

1.Introduction

With the rise of unconventional oil recoveries,crude oil improvement is one of the challenges in petroleum industry.The sour crude oil is normally dealt with via conventional refinery process,along with severe corrosion problems.A possible solution for the corrosion problems is to reduce the sulfur content of crude oil before the distillation units by the effective hydrodesulfurization (HDS) method.The hydrotreatment of whole sour crude cannot only improve the fuel quality by simultaneously reducing the contents of impurities (such as sulfur,nitrogen,vanadium,nickel and asphaltene),but also can increase the productivity of middle distillate fractions[1].Hydrotreatment is a powerful technique to reduce the sulfur content in various oil fractions,such as gasoline,kerosene,diesel and heavy residues.However,the crude oil hydrotreating process remains a challenge due to the multiple phases,as well as various compounds and complex structures.The increase of the steric hindrance effect by large molecule diffusion is not conducive to the adsorption of reactant molecules on the inner surface of the catalyst,and the increase of asphaltene content will lead to the increase of coke yield and the decrease of desulfurization activity of the catalyst.Therefore,hydrodesulfurization of crude oil is considered to be one of the most difficult and important problems at present.

Another consideration for the hydrodesulfurization of crude oil is to substitute sour crude oil feed for sweet crude in an existing refinery plant so as to minimize the investment cost.In China,most of the existing refineries were built for sweet crude oil.With the increasing demand for imported sour crude oil,it is necessary to adapt the refinery process and the distillation units to sour crude.For example,with the official construction of the Russia–China crude oil pipeline from Skovorodino distribution station (Russian Far East) to the Daqing station(Northeastern China)[2,3].Daqing petrochemical refinery of China National Petroleum Corporation(CNPC)would refine Siberian crude with significantly low transportation costs;however,the current units are not capable to deal with Siberian crude directly.Daqing petrochemical refinery was originally built for Daqing crude with sulfur content as low as 0.11%,while Siberian crude oil has a sulfur content of above 5000 μg?g?1[4,5].If Siberian crude is directly refined on site,the atmospheric and vacuum distillation columns and the related equipment will be seriously corroded,and the resulting oil fractions will be of high sulfur content,thus leading to unsatisfactory products and more corrosion problems in the following units.Therefore,it is important to develop an economic refining process on site for Siberian crude oil.In order to refine Siberian crude with low investment cost at Daqing site,a hydrodesulfurization(HDS)unit was proposed in front of the atmospheric distillation column,as shown in Fig.1.Although various types of reactor have been reported in the hydrodesulfurization process,trickle-bed reactor(TBR)is still the maturest one.TBR is operated in the plug flow pattern which results in higher conversion efficiency;the pressure drop is low and the outlet product does not require liquid–solid separation;furthermore,TBR is more convenient to make combinations of the hydrodemetallization and hydrodesulfurization reactions which are typical upgrading processes for crude oil.Therefore,TBR is used in the current work for both experimental study and modeling.

TBR has been widely used in the hydrotreatment processes of various oil fractions.Three phases are present inside the reactor,and the modeling is complex due to the reaction kinetics as well as hydrodynamics and mass transfer effects.In 1996,a three-phase heterogeneous model for vacuum oil hydrodesulfurization was proposed in a trickle bed reactor[6],which described the mass transfer at the two-phase interfaces by the two-film theory,and described the reaction kinetics by Langmuir-Hinshelwood mechanism.The model has been adopted in the HDS of atmospheric gas oil fraction [7],vacuum gas oil [6],and Iraqi crude[8].In these systems,the model had a good performance in predicting experimental data in reactor design and optimization,thus reducing the cost and time for the investigation into impacts of operation parameters.

In the study of Siberian HDS process,the kinetic model is an important part for industrial reactor simulation and design.To the best of our knowledge,little has been reported on the hydrotreatment of Siberian crude.By understanding the catalyst properties from the aspects of intrinsic kinetics and diffusion limitations,the performance of HDS could be predicted under different operating conditions.In the current study,HDS of Siberian crude oil was carried out under different reaction conditions in a continuous flow,isothermal trickle-bed reactor.The kinetic parameters were estimated by minimizing the square sum error between the experimental data and the model predicted data using MATLAB software.Finally,the concentration of H2,H2S and sulfur along the catalyst bed were discussed by simulating the reactor using the established model.

2.Experimental

2.1.Reactor setup and oil properties

The hydrodesulfurization of Siberian crude oil was carried out in an iso-thermal trickle-bed reactor,as shown in Fig.2.The Siberian crude oil collected from Russia–China pipeline at Daqing distribution was used as feed.The physical and chemical properties of the feedstock were provided by CNPC Daqing branch and are presented in Table 1.The trickle-bed reactor has an internal diameter of 1 cm and a total length of 30 cm.During the HDS test,H2and crude oil were fed into the reactor in a cocurrent flow mode.The product was cooled by a condenser prior to collection.

2.2.Catalyst preparation and characterization

2.2.1.Catalyst preparation

The catalyst is a typical Ni-Mo sulfide catalyst supported on commercial γ-Al2O3(ZiBoYinghe Co.Ltd.),with a total metal oxide loading of 25 wt%and a Mo/Ni molar ratio of 4.The catalyst was synthesized by sequential incipient wetness impregnation.The precursor solutions were prepared by dissolving ammonium molybdate tetrahydrate(Tianjin Chemical Reagent Co.,Ltd) or nickel nitrate hexahydrate(Dongxiyi Beijing Technology Co.Ltd) in an amount of water just sufficient to fill the pores of 5 g of the support.The precursor solution was then added to the support by dropwise addition and was stirred thoroughly between droplets.The samples were aged for 1 h at room temperature.Afterwards,the impregnated samples were dried at 100°C for 12 h and were calcined at 400°C for 5 h.The as-synthesized catalysts with diameters between 180 and 250 μm were screened for HDS test.

2.2.2.Catalyst characterization

The X-ray powder diffraction(XRD)patterns of the catalyst support and the prepared catalyst were measured by D/max-gamma beta X-ray powder diffraction(XRD)of Nippon Science and Electric Corporation with a wavelength of light source of 0.15406 nm and a scanning speed of 5 min?1.The working voltage and current were 40 kV and 150 mA,respectively.

The Brunauer–Emmett–Teller(BET) surface areas of the samples were measured by N2-physisorption using a BELSORP-max physical adsorbent(Ankersmid B.V.).The samples were first vacuum-activated at 300°C for 4 h,and were then placed in a liquid nitrogen tank for the N2adsorption–desorption test operated at ?200°C.

The catalyst morphology was characterized by scanning electronic microscopy (SEM).Quanta FEG250 scanning electron microscopy of PANalytical Company in the Netherlands was used to observe the micro-morphology of the samples,and all the tests were operated at 20 kV.

2.3.HDS test

In the HDS experiment,2 g of catalyst was loaded into the middle of the reactor,and the rest of the reactor was filled with glass beads.The catalyst bed was measured of 3 cm in length.Prior to reaction,the catalyst was in situ pre-sulfurized with a 3%CS2cyclohexane solution at 400°C for 5 h.Afterwards,the catalyst was cooled to reaction temperature in N2atmosphere.

The test was carried out by varying reaction temperature,pressure and LHSV(based on total catalyst volume)in the ranges of 320–360°C and 0.5–2.0 h?1,3–5 MPa,respectively,in order to study the effect of these variables and to determine the kinetic parameters of the HDS reaction.H2/oil ratio at the entrance of the reaction system was kept at 600 L·L?1.The samples were collected and were diluted with paraxylene prior to analysis.The schematic view of the experimental setup is shown in Fig.2.The sulfur contents of the feedstock and collected liquid samples were analyzed using ZDS-2000A ultraviolet fluorescence sulfur analyzer(Jiangsu Xinke Analytical Instrument Co.,Ltd.).Carbon number distribution in crude oil samples before and after HDS was measured by gas chromatography–mass spectrometry (GC–MS) with a TG-5MS capillary column(length of 30 m,inner diameter of 0.32 mm and membrane degree of 0.25 μm).The inlet temperature was 280°C,the shunt ratio was 50∶1 and the column flow rate was 1.5 mL·min?1.For the mass spectrometry,the solvent is delayed by 3 min,the scanning range is 35–500 amu,the ion source temperature is 280°C,and the transmission line temperature is 280°C.

The reactor was modeled by a three phase heterogeneous model based on the two-film theory using Langmuir-Hinshelwood mechanism.Details of the TBR model are incorporated in the supplemental materials.

Fig.1.Process modification for sour crude oil in an existing refinery built for sweet crude oil.

Fig.2.Schematic setup of HDS experiment.

3.Results and Discussions

3.1.Catalyst characterization

The XRD patterns of the commercial alumina support and the prepared Ni-Mo/Al2O3catalyst are shown in Fig.3.The characteristic diffraction peaks of(311),(400)and(441)crystal planes of γ-Al2O3are observed at 37.5°,45.8°and 67.3°of 2θ for both the support and the catalyst,while Ni-Mo/γ-Al2O3catalysts exhibits a sharp characteristic diffraction peak of NiMoO4at 26.7° [9].The peaks of monometallic oxides are also present.The peaks at 37.3° and 63.4° correspond to NiO while the peak at 36.6°corresponds to MoO3[9].

The surface area,pore volume and average pore size of γ-Al2O3and Ni-Mo/γ-Al2O3are summarized in Table 2.After impregnation,the surface area,pore volume and the average pore size of γ-Al2O3decrease,indicating that the active components are distributed on the pore surface of the support.The surface area and pore volume of Ni-Mo/γ-Al2O3are 189.6 m2?g?1and 0.47 cm3?g?1,respectively.The bulk density was measured as 0.598 g?cm?3.The above information were used in the physical properties of catalysts in the modeling setup.

The morphology of the fresh and used catalysts is exhibited in the SEM images in Fig.4.The catalysts before reaction have a porous structure.During the HDS reaction,crude oil flowed through the catalyst bed;therefore the catalysts after reaction are coated by a layer of liquid oil.Meanwhile,the used catalysts are less porous,probably due to partial collapse of pore structure caused by the high pressure during the HDS reaction.

Table 1 Siberian crude oil properties

Fig.3.XRD patterns of γ-Al2 O3 and NiMo/γ-Al2 O3 .

3.2.Upgrading Siberian crude oil

Siberian crude oil was processed by HDS in the trickle-bed reactor at 340–360°C,pressure range of 3–5 MPa,and LHSV range of 0.5–2.0 h?1.In order to have an overview of the effect of HDS process on oil properties,the carbon number distributions and the metal contents before and after the reaction were measured and are presented in Table 3.After the reaction,the mass fractions of carbon number higher than 21 are reduced by 3.83% in total while the mass fractions of carbon number lower than 16 increase by 3.98%,implying that a small proportion of the crude oil undergoes the hydrocracking reaction during the treatment.The metal contents are also provided in Table 3.

Table 2 N2 -physisorption(BET)results of γ-Al2 O3 and Ni-Mo/γ-Al2 O3

Fig.4.SEM images of the catalysts(a)(c)before and(b)(d)after HDS.

Table 3 Carbon number distribution and metal contents of Siberian crude oil before and after hydrodesulfurization reaction

After the HDS treatment,the metal contents are drastically reduced and fall below the detection limits,indicating the presence of hydrodemetallization reaction during the process.The HDS process usually combines a variety of hydrotreating reactions,which cannot only reduce the sulfur content as well as metal contents,but also can shift the hydrocarbon molecules to lower carbon numbers.The combined reaction in the hydrotreatment would upgrade the crude oil towards light,sweet and clean oil,and would benefit the maintenance of equipment.

3.3.Estimation of kinetic parameters

Although the reactions other than HDS exist in the treatment,the hydrocracking and hydrodemetallization reaction is only a minor part;therefore,they are neglected in the reactor modeling.The three-phase heterogeneous reactor model involves many parameters,such as the properties of gas and liquid,solubility coefficients,diffusion coefficients and mass transfer coefficients.In order to better understand the phenomenon inside the HDS reactor,the reaction rate constants and reaction orders can be estimated by the regression of experimental data.The estimated reaction rate constant increases with increasing temperature,as presented in Table 4.The reaction order of sulfur components is 1.28,and the reaction order of hydrogen is 0.39,which is typical for the lumped model of crude oil.

Table 4 Kinetic parameter values estimated by experimental data regression

Fig.5.Arrhenius equation plot for HDS of Siberian crude oil.

The activation energy(EA,HDS)and pre-exponential factorcan be estimated by the Arrhenius equation.The Arrhenius equation can be rearranged as follows:y=ax+b,where y=lnKHDS,a=?EA,HDS/R,x=1/T,b=The linear plot of x and y is shown in Fig.5 with a satisfactory R2of 0.99992,where the slope gives ?EA,HDS/R,and the intercept givesThe activation energy is obtained as 34.65 kJ?mol?1,and the pre-exponential factor is obtained as 112.35.

3.4.Experimental results and model analysis

The experimental data and simulation results under different operating conditions are summarized in Table 5.It could be observed from the table that the Siberian crude oil can be sweetened under mild conditions.In the temperature range of 340–360°C,pressure range of 3–5 MPa,and LHSV range of 0.5–2.0 h?1,the average desulfurization conversion can reach more than 85%.After the HDS reaction,the oil can meet the requirement of the distillation units in Daqing petrochemical refinery,verifying that the HDS method is very effective and economic in dealing with sour crude on an existing site built for sweet crude.

The absolute error between simulation results and experimental data is listed Table 5.The largest absolute error is 0.11%,indicating that the model can predict the experimental data well in the investigated range.Moreover,the sulfur contents in the product by experimental measurement are plotted against the sulfur contents by simulation as shown in Fig.6.The simulation data shows a linear relationship with the experimental data,and the slope is close to 1.0,indicating a good prediction from the established three-phase heterogeneous model.

It is also observed that the sulfur removal efficiency increases with increasing temperature,increasing pressure and decreasing LHSV.For the HDS of Siberian crude,the operating conditions are relatively mild compared with other crude oils,such as Iraqi crude [8]and Maya crude[10].The effects of temperature,pressure and LHSV are discussed in detail in Section 3.4.1.Furthermore,by the simulation of the reactor,the concentration profiles of H2,H2S,and sulfur components are presented and discussed in Section 3.4.2.

3.4.1.Effect of operating conditions on HDS

3.4.1.1.Effect of temperature.The HDS conversions under different temperatures are plotted in Fig.7.It could be observed that the HDS conversion increases with the increase of temperature.When the temperature increases from 320°C to 340°C,the HDS conversion increases by about 5%;however when the temperature increases from 340°C to 360°C,the conversion does not increase much.The minor conversion increase from 340 °C to 360 °C probably stems from the diffusion resistance.The reaction rate constant increases exponentially with increasing temperature as exhibited in the Arrhenius equation,while the mass transfer coefficients exhibits a polynomial growth(by an order of 2.885)as analyzed by the relevant equations.As a result,the increase in mass transfer rate cannot catch up with the increase in reaction rate at elevated temperature,exhibiting slower increase in conversion within the high temperature range.Furthermore,the effectiveness factor decreases with increasing temperature as shown in Table 6,verifying the mass transfer effect increases with increasing temperature.In addition,the temperature also affects the adsorption equilibrium constant of H2S on the catalyst surface.The adsorption equilibrium constant decreases with increasing temperature,implying a lower H2S coverage on the catalyst surface,which is beneficial for the active site exposure and could enhance the HDS reaction rate.

These theoretical foundations provide the basis for increasing the operating temperature to improve the desulfurization degree.However,excessively higher temperature may not only lead to faster catalyst deactivation,but also increase the energy consumption.In a typical refinery plant,the temperature of the atmospheric column feed is～360°C.If the temperature of HDS product is higher than 360°C,heat exchangers are needed to be set up and excess energy would be consumed.In the current study,the sulfur content could be lowered blow 0.11%(the sulfur content in Daqing Crude)at relatively lower temperature of 320°C–340°C.Accounting for the temperature rise in a trickle-bed reactor,the temperature in the reactor feed should be lower than 340°C from an economic perspective.

3.4.1.2.Effect of pressure.The influence of pressure on hydrodesulfurization reaction is plotted in Fig.8.The HDS conversion increases with increasing pressure as well as temperature.The positive correlation could be attributed to the positive kinetic order for hydrogen(0.39).However,the effect of pressure is negligible in comparison with the effect of temperature.When the pressure increases from 3 MPa to 5 MPa,the HDS conversion only increases by 1%–3%.In the three phase heterogeneous model,the pressure affects the oil density,Henry coefficients and mass transfer coefficients.As the viscosity and density of liquid oil are insensitive to pressure,the molecular diffusivities,Henry coefficients and mass transfer coefficients are not much affected by pressure.The significant effect of pressure is on the mass balance equations in gas and liquid phases.When the partial pressure of H2increases,more H2are present in the liquid phase;therefore,the concentration of hydrogen on the catalyst surface increases with increasing pressure,leading to a higher HDS conversion.However,the effect of pressure is insignificant and has been verified by the low kinetic order of 0.39.Moreover,the concentration of H2S on the catalyst surface also increases with the increase of pressure,thus inhibiting the HDS rate by poisoning the active sites.

3.4.1.3.Effect of LHSV.A comparison of experimental data,obtained by adjusting liquid hourly space velocity(LHSV)in the range of LHSV=0.5–2 h?1,exhibits that the conversion rate decreases with increasing LHSV as shown in Fig.9.LHSV affects the mass velocity of the gases and liquids,thus affecting the mass balance equation.When LHSV increases,the wetting efficiency of catalyst particles decreases,and the conversion decreases due to the partial wetting of catalyst particles.The trickle flow pattern is subdivided into fully and partially wetted zones depending on the flow rate of the liquid.The wetting efficiency is a function of the initial liquid distribution,the geometry of the catalyst,and the mass flow rate.Because the initial liquid distribution and the catalyst in this study are under the same conditions,the wetting efficiency depends on the mass flow rate.Moreover,the LHSV represents the processing load of the reactor.When LHSV increases,one gram of catalyst deals with more crude oil;therefore the HDS conversion decreases in the outlet.

Table 5 Experimental data and simulation results under different reaction conditions

3.4.2.Simulation of the HDS reactor

The established model can be used to simulate the operation of the trickle-bed reactor under different operating conditions when the experimental data are not available.In addition,the simulation results would help us understand the concentration distributions of H2,H2S and liquid sulfur components in the three phases along the catalyst bed,which are not experimentally available for a conventional tricklebed reactor.The HDS simulation was carried out under the highest investigated LHSV of 2 h?1,with temperature of 360°C and pressure of 5 MPa.The operating conditions and transfer coefficients in a reactor are shown in Table 7.

The concentration profiles of H2and H2S in the gas phase are exhibited in Fig.10.It is shown that the partial pressure of H2in gas phase decreases the along the catalyst bed,while the partial pressure of H2S increases along the catalyst bed length.This indicates the hydrogen consumption and hydrogen sulfide production in the process of the HDS reaction.With increasing catalyst bed length,the residence time of crude oil increases,thus pushing forward the HDS progress.

Fig.6.Comparison between experimental and calculated concentrations of sulfur content.

Fig.7.Effect of temperature on HDS of Siberian crude oil.

Table 6 Effective factors at different temperatures

Fig.8.Effect of pressure on HDS of Siberian crude oil.

Fig.9.Effect of LHSV on HDS of Siberian crude oil.

Table 7 Simulation conditions and transport coefficients in a bench-scale trickle-bed reactor

Fig.10.Concentration profiles of H2 and H2 S in gas phase along the catalyst bed.

Fig.11.Concentration profiles of H2 in liquid and solid phase along the catalyst bed.

Fig.12.Concentration profiles of H2 S in liquid and solid phase down through the reactor.

Figs.11 and 12 display the distribution of molar concentrations of H2and H2S in liquid and solid phases along the catalyst bed.With the increase of catalyst bed length,the concentrations of H2in liquid and solid phases both decrease,while the concentrations of H2S in liquid and solid phases both increase.The concentration profiles in the liquid and solid phases are affected by the mass transfer rate at the gas–liquid and liquid–solid interfaces,as well as the intrinsic reaction rate.It was reported that the concentration of H2S would firstly increase and then decrease in the liquid and solid phases as simulated in a pilot tricklebed reactor,and the concentration of H2would firstly decrease and then increase along the catalyst bed,exhibiting a“U”-shaped curve[7,11].The behavior could be explained by the different mass transfer rate along the reactor length.At the entrance of the reactor,the concentration of H2falls quickly owing to the reaction rate;after a certain point along the catalyst bed,H2would concentrate progressively in the liquid phase and this part of reactor is governed by gas–liquid equilibrium.In the current study,a small-scale model was used with the reactor bed length of 3 cm.As a consequence,the concentration profiles do not show the“U”-shaped curve as reported in the pilot plant reactor model.In the HDS reactor,the concentration of H2in solid phase firstly decreases due to the reaction on the catalyst surface,and the concentration in liquid phase then decreases as a consequence of liquid–solid transfer.

The molar concentrations of sulfur in liquid and solid phases are shown in Fig.13.The concentration of sulfur in crude oil decreases along the length of catalyst bed in both liquid and solid phases,and the concentration difference between the liquid and solid surfaces decreases.The concentration difference indicates the liquid–solid mass transfer effect of the crude oil.In the established model,the mass transfer coefficient depends on the properties of crude oil,such as density and viscosity,as well as the mass flow rate of liquid.With the decrease of sulfur content in crude oil,the physical properties are improved,and the liquid–solid mass transfer rate is enhanced,exhibiting a reduced concentration difference between the liquid phase and solid phase[12].

Fig.13.Concentration profiles of sulfur in liquid and solid phase along the catalyst bed.

4.Conclusions

Hydrodesulfurization(HDS)of Siberian crude oil was reported for the first time and was carried out in a continuous flow isothermal trickle-bed reactor using Ni-Mo/γ-Al2O3as catalyst.The effects of temperature,pressure,and LHSVs were investigated in the ranges of 320–360°C,3–5 MPa and 0.5–2 h?1,keeping constant hydrogen to oil ratio at 600 L·L?1.The HDS conversion increases with the increase of reaction temperature and pressure,and decreases with increasing LHSVs.The effect of temperature is obvious while the effect of pressure is insignificant.The sulfur removal could reach up to 92.89%at the temperature of 360°C,pressure of 5 MPa,and LHSV of 0.5 h?1.Other mild conditions can also give considerable HDS conversions of above 84%.From an economic perspective,the reaction temperature should not exceed 360°C,which is the inlet temperature of atmospheric column,in order to reduce the energy consumption and the investment cost for heat exchangers.

A three-phase heterogeneous model including a series of differential equations and algebraic equations is established for the trickle-bed reactor,to describe the HDS process of Siberian crude oil based on the two-film theory using Langmuir-Hinshelwood mechanism.By including the mass transfer equations and kinetic equations in the model,the kinetic parameters were estimated by minimizing the sum of squared errors between the experimental data and simulated data.The pre-exponential factors and activation energies of the reaction were obtained by a linear fitting of the Arrhenius equation.The estimated order of sulfur component is 1.28 and the order of hydrogen is 0.39;the activation energy is 34.65 kJ?mol?1and the pre-exponential factor is obtained as 112.35.The reactor model was then employed to simulate the sulfur content in the product,and the results are in good agreement with the experimental data.Furthermore,the model allows for observing the concentrations along the catalyst bed,and the concentration profiles of H2,H2S and sulfur along the catalyst bed were discussed.

The model could be applied in reactor analysis,optimization,and reactor design,and can provide further insight of the HDS of Siberian crude oil.Furthermore,the HDS of Siberian crude oil under relatively mild conditions significantly reduces the sulfur content,and can meet the equipment requirements of Daqing petrochemical refinery of CNPC.

Acknowledgements

The work was carried out at Beijing Key Laboratory for Chemical Power Source and Green Catalysis.We thank Analysis&Testing Center at Beijing Institute of Technology for the supports on catalyst characterization.

Supplementary Material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cjche.2020.07.021.