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The synthesis of propylene oxide from propylene and hydrogen peroxide and the side reactions of propylene oxide were studied in a broad range of experimental conditions (25–80 °C, 2.5–8.5 bar) in a...

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-Al2O3. 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, H2S and sulfur along the catalyst bed are 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.

The dynamic liquid distribution and holdup in a TBR packed with porous quadrilobe catalyst were studied using advanced Gamma-ray Computed Tomography. A multi-compartment module is used to quantify the maldistribution factor which shows that there is a transition region from high maldistribution to relatively uniform distribution depending on the flowrates. The 3D maldistribution maps show that there is more dynamic liquid close to the column center at high bed height and there is no high correlation between the average dynamic liquid holdup and the bed height. If the gas flowrate increases while keeping the liquid flowrate fixed, the average dynamic liquid holdup decreases; however, if the gas flowrate is fixed, there is no dominant increasing or decreasing trend showing up. A Deep Neural Network model and a pseudo-3D model are developed showing high accuracy for predicting the local dynamic liquid holdup at different bed heights, radius, and flowrates.

At present, a few chemicals can be separated after further processing of high-temperature coal tar (HTCT) distillates, which have a lower utilization. However, hydrogenation to produce clean fuel oil has not been widely reported in literature. Thus, due to the use of new feedstocks and the implementation of more severe environmental legislations, deep hydrodesulfurization (HDS) of HTCT will face formidable challenges. A series of HDS experiments were performed in a continuous isothermal trickle bed reactor in which the reactor temperature was varied from 648 to 678 K, the pressure from 12 to 16 MPa, and the liquid hourly space velocity (LHSV) from 0.25 to 0.35 h–1, and hydrogen-to-oil ratio kept constant at 2000 L/L. Based on the experimental data, possible reaction pathways of HDS reaction were investigated, and a modified Langmuir–Hinshelwood (LH) HTCT desulfurization kinetic model was established. gPROMS software was used to obtain optimal kinetic parameters that are as follows: EA = 26,842, K0 = 93,958, α = −1.14, n = 1.65, and m = 0.86. The model can well reproduce various working conditions and has better prediction accuracy. Some characteristics of HTCT HDS reactions were discovered; the reaction order (n) of HTCT HDS is slightly higher than that of crude oil and medium/low-temperature coal tar (M/LTCT), but the activation energy (EA) is relatively smaller. The established reactor model was used to predict the changes of the concentration of hydrogen, hydrogen sulfide, and sulfur compounds in the gas, liquid, and solid phases along the length of the reactor, respectively. The model was also used to predict the effects of pressure, temperature, and LHSV on the conversion rate of sulfur and catalyst effectiveness factors. The results showed that the LHSV has a greater impact on the conversion rate, and the pressure and temperature are less pronounced at high-severity operating conditions; the effectiveness factor is significantly smaller than that of other HDS processes, temperature has a greater effect on the effectiveness factor, followed by pressure and LHSV. The conclusion can provide a basis for further understanding the HTCT hydrotreating process.

In this study, we developed an efficient technology for the continuous conversion of glucose into methyl lactate over Sn-Beta zeolite with a trickle bed reactor. The catalyst exhibited a high yield...

Phasic maldistribution triggers hot spots within the catalyst bed in a trickle bed reactor. We investigate hot spot formation during hydrodesulphurization of diesel to understand the role of physic...

In this work, a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction–diffusion behaviors in gas oil hydrodesulfurization (HDS). The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat. The reaction rate along the reactor is mainly dominated by the temperature, and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor, leading to the increased internal effectiveness factor. For the fixed catalyst bed volume, there exists a compromise between the catalyst reaction rate and effectiveness factor. Under commonly studied catalyst pellet size of 0.8–3 mm and porosity of 0.4–0.8, an optimization of the temperature and catalyst pellet structures is carried out, and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.

Stationary kinetic methods are not sufficient for studying chemical processes in which solid heterogeneous catalysts and several phases (gas-liquid-solid) are involved, therefore transient experimental techniques are applied to reveal the molecular processes on the catalyst surfaces. Dynamic methods were used to study the kinetics of a heterogeneously catalyzed reaction i.e. the epoxidation of ethylene with hydrogen peroxide as the oxidizing agent and titanium silicalite (TS-1) as the heterogeneous catalyst. No detailed reaction mechanism and kinetic model has ever been proposed for this process. For the kinetic investigation, step response experiments were carried out in a laboratory-scale trickle bed reactor (TBR). A dynamic isothermal model for the TBR was presented together with a dynamic kinetic model based on a proposed surface reaction mechanism, where the key step is the reaction between adsorbed hydrogen peroxide and dissolved ethylene from the liquid phase. The TBR model consisted of dynamic mass balance equations for the components present in the gas and liquid bulk phases as well as adsorbed species on the catalyst surface. The model formed a coupled system of parabolic partial differential equations (gas and liquid phases) and ordinary differential equations (catalyst surface phase). The coupled system of differential equations, describing the concentration profiles from the step response experiments were solved numerically by the method of lines by discretizing the reactor length coordinate with finite differences and solving the large system of ordinary differential equations by a backward difference algorithm suitable for stiff ordinary differential equations. The parameters for surface kinetics, mass transfer and fluid dynamics were determined by non-linear regression analysis using the maximum likelihood approach. The model was able to predict the transient and stationary behavior of the system.

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.

Hydrodesulfurization (HDS), a pivotal process for sulfur removal that is essential in deep processing of crude oil, is typically carried out in steady-state trickle-bed reactors (TBRs). Being famil...

Hydrodesulfurization of heavy oil is usually operated in a trickle bed reactor. Analysis and design of this reactor require modeling both at the macro-reactor scale and micro-catalyst scale. The paper is focused on the catalyst-level modeling and takes into consideration complex catalyst shapes, wettability, and spatial variation in diffusivity due to catalyst pore plugging. Furthermore, the effects of mass transfer from dry and wet zones around the partially wetted catalyst surface are included. Finite element method is used for two-dimensional analysis as it is versatile and can handle complex shapes. The catalyst-level model includes an updating of effective diffusivity with time, and hence the lifetime of a complex shaped catalyst can be predicted. Long-time operation shows that thickness of plugged pore is large and also non-uniform across the two-dimensional catalyst particle with more plugging near the catalyst surface. In addition, the reaction regime changes with time, the fresh catalyst initially being in a diffusion-resistance-free regime and changing to a strong-diffusion-resistance regime at longer operating times. The computational method can be used for optimization of the operating protocol and to design optimum pore size and shape of the catalyst, although these details are not addressed in this paper.

Neutron radiography can visualize heavy oil flows in metallic reactors used to upgrade heavy oils. Thus, we visualized heavy oil flows in a packed bed using real-time neutron radiography to support its capability and to offer basic experimental data necessary for verification and validation of numerical simulations. Atmospheric residue was used as the heavy oil sample and heavy oil and N2 gas were concurrently supplied into a packed bed from above a reactor simulating a trickle bed reactor. Reactor temperatures were set at either 100°C or 250°C to change heavy oil viscosity. The heavy oil flow rate was kept constant at 2.5 mL/min and the N2 gas flow rate was set at either 1 L/min or 3 L/min at 25°C. A series of neutron radiography experiments was conducted at the B-4 neutron imaging facility in the Kyoto University Research Reactor (KUR) with a thermal neutron flux of 5 × 107 n/cm2⋅s. We performed image processing for the neutron radiographs to calculate neutron beam attenuation and clarify flow behavior. Visualization results show differences in flow behavior depending on operating factors. Temperature had a particularly substantial effect on flow behavior because heavy oil viscosity depends strongly on temperature. The flows also showed different behaviors for 1 mm and 3 mm packed particle sizes because the void ratios in the packed bed, which were preliminarily observed by X-ray computational tomography (CT), change with particle size. Channeling flow was observed with 3 mm particles and a temperature of 250°C. Furthermore, this work suggests that neutron radiography can be used to investigate heavy oil flows in metallic reactors.

A detailed, molecule-based trickle bed reactor model has been developed to simulate industrial vacuum gas oil (VGO) hydrotreaters. A feed characterization module is used to calculate the composition of the feed without any detailed experimental component analysis. Feed VGO is represented by a pre-defined set of 120 pure molecules, from carbon numbers C14 to C33, and the proportion of these components is calculated using an optimization algorithm so as to match the physico-chemical properties of the mixture with those of VGO, as measured in the laboratory. This molecular composition is used as an input to model the reactions occurring in a hydrotreating reactor. The main reactions occurring in the hydrotreater such as hydro desulfurization, hydro denitrogenation and aromatic saturation reactions, are modeled. The kinetic parameters for these reactions have been estimated from a comprehensive set of experimental pilot plant data spanning a wide range of process conditions. Simulation results showed that the model reproduces the product distribution by boiling range, composition and the temperature rise in the catalyst bed for a range of operating conditions for industrial refinery units.

Trickle bed reactors (TBRs) are widely used in chemical and oil industries. Owing to complex nature of flow in TBRs, measurements of local liquid holdup distribution are rather limited. While several non-invasive measurement techniques have been used to measure liquid distribution in TBRs, the applicability of Electrical Resistance Tomography (ERT) for quantitative measurement of liquid holdup distribution is not yet verified. In the present work, measurements of local liquid distribution in a laboratory-scale TBR are carried out using ERT for trickle to transition flow regimes. The time-averaged liquid holdup distributions measured using the ERT and BLC methods were compared using the liquid maldistribution factor to demonstrate the feasibility of the ERT to measure liquid holdup distribution. The effect of liquid-distributor configurations (semi-uniform, local and one-sided) was investigated on the radial liquid distribution at different axial locations of TBR. Further, the ability of ERT to measure time-resolved local liquid distribution was verified using multi-point conductivity sensors for artificially created pulsing flow. Also, the comparison of liquid pulse width with multi-point conductivity sensor measurements was carried out and of the dispersion of liquid pulse along the length of TBR was analyzed. The ERT measurements were performed to quantify the effects of gas and liquid flow rates, and particle size on the local liquid holdup. The void-scale flow structure measured by multi-point conductivity sensors was used to analyze the macroscopic (bed-scale) liquid holdup distribution measured by ERT. Thus, the comparison of ERT measurements with time-averaged BLC and time-resolved multi-point conductivity sensor measurements is important to establish the applicability of ERT for quantitative spatial and in particular the time-resolved measurements of liquid holdup in TBRs.

Enhanced weathering (EW) of alkaline minerals can potentially capture CO2 from the atmosphere at gigaton scale, but the reactor design presents great challenges. We model EW with fresh water in a counter‐current trickle flow packed bed batch of 1–10 mm calcite particles. Weathering kinetics are integrated with the mass transfer of CO2 incorporating transfer enhancement by chemical reaction. To avoid flooding, flow rates must be reduced as the particles shrink due to EW. The capture rate is mainly limited by slow transfer of CO2 from gas to liquid although slow dissolution of calcite can also play a role in certain circumstances. A bed height of at least 7–8 m is required to provide sufficient residence time. The results highlight the need to improve capture rate and reduce energy and water consumption, possibly through enriching the feed with CO2 and further chemical acceleration of the mass transfer.

Oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was carried out over Ru/Al2O3 using O2 aqueous alkaline solutions in a trickle-bed reactor. HMF was completely conver...

With whole-fraction low temperature coal tar (LTCT) as raw material, which boiling point range is 209–514 °C. This paper conducts hydrotreatment (HDT) test for 1176 h on trickle-bed reactor (TBR) with commercial NiMo/Al2O3-SiO2 catalyst. The reaction conditions are as follows: reaction temperature 613–653 K, reaction pressure 10–14 MPa, liquid hourly space velocity (LHSV) 0.2–0.4 h−1, and hydrogen-to-oil volume ratio 1000:1. Considering the short life of coal tar HDT catalyst, a kinetic model of whole-fraction LTCT hydrodesulfurization (HDS) including running time (t1) and catalyst half-life (tc) was established. The kinetic parameter estimation was conducted according to the experimental data, and the results are as follows: activation energy 94965 J/mol, reaction order 1.5, and the relative error of the model is less than 5%. Based on the premise of steady state operation, the HDS reaction happened in the three-phase trickle-bed reactor was simulated by combining the mass transfer, reaction kinetics model and physical property data of LTCT. The results show that the experimental and simulated values of sulphur content at the exit of the reactor are within the error range of 5%. By simulating the whole-fraction LTCT HDS reactor, the pattern of changes in the concentrations of hydrogen sulfide, hydrogen and sulfur in gas, liquid and solid phases according to the length of the reactor were obtained. Based on this, this paper discusses on the impacts of each process parameter and hydrogen sulfide partial pressure on LTCT HDS, and works out the reaction characteristics of whole-fraction LTCT HDS different from crude oil fraction. Finally, this paper analyzes the influence of different process conditions on internal gradients of catalyst, and concludes the influence of each parameter on effectiveness factor of particle. The increase of temperature, decrease of pressure or increase of LHSV can all cause the decrease of effectiveness factor, wherein the temperature has the most significant effect on the effectiveness factor, followed by LHSV, and pressure has the weakest effect. These findings contribute to a more in-depth understanding of the features and rules of LTCT HDS, and can also give us some guidance for industrial reactor simulation.

In this study, modeling and simulation of the dynamic behavior of an industrial-scale trickle bed reactor (TBR) with application to a hydropurification process for production of purified terephthal...

This study is focused on the challenges associated with the utilization of heavy oil as refinery feedstock. Various catalytic and non-catalytic methods to achieve higher desulfurization of feed have been widely studied in the past. In this study, we are proposing a new integrated technology that combines selective adsorption of heterocyclic sulfur and nitrogen compounds followed by catalytic hydrotreatment. Glycidyl methacrylate based polymers were developed in bulk and used as an adsorbent for the removal of nitrogen and sulfur species. In the first step, the polymeric adsorbent reduced sulfur and nitrogen content of heavy gas oil through charge transfer complex formation. Optimization of adsorption parameters was done using Taguchi orthogonal array to maximize the removal of catalyst inhibiting nitrogen heterocyclic compounds. Afterwards, hydrotreatment of polymer treated heavy gas oil was studied in a trickle-bed reactor. Functionalized polymer treated feed was hydrotreated using NiMo/γ-Al2O3 catalyst synthesized in lab with 13 wt% molybdenum and 2.5 wt% nickel, and hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) activities were measured. Experiments were performed in the temperature range of 370–390 °C, pressure of 8.96 MPa, 1 h−1 LHSV and H2/oil ratio = 600 (v/v). Prior removal of nitrogen and sulfur compounds using functionalized polymer subsequently favored the hydrotreating activity in the trickle bed reactor. Removal of refractory sulfur and nitrogen species before hydrotreatment has resulted in 94.3 wt% HDS and 63.3 wt% HDN as compared to 93.1 wt% HDS and 60.5 wt% HDN activities at optimum temperature of 390 °C. A total of 42.8% aromatic content was found in untreated HGO which decreased in the polymer pre-treated HGO. The highest HDA was observed for polymer pre-treated HGO feed at 390 °C, where the aromatic content decreased from 23.9% to 21%.

NiAl2O4 spinel-type catalyst was successfully prepared by an incipient wetness impregnation method accompanied with high-temperature calcination at 1273 K for 10 h. The effect of reduction temperatures (773, 923, and 1073 K) on the catalytic activity for palm oil deoxygenations to green diesel was investigated at 573 K and 5 MPa in a trickle bed reactor. The XRD and XANES analyses confirmed the formation of metallic Ni after pre-reduction, which exhibited a variation of reduction degree at different temperatures. The TEM analysis revealed the formation of large particle size of the catalysts reduced at higher temperature. The highest product yield (94.3%) was achieved for the NiAl2O4 reduced at 923 K. Interestingly, the spinel-type catalyst was highly stable for 24 h on-stream, while the fast degradation was found over a reference catalyst, Ni supported on γ-Al2O3. The decarbonylation and/or decarboxylation (DCO/DCO2) reactions were dominant over the hydrodeoxygenation (HDO) pathway over all the catalysts. The high performance of NiAl2O4 spinel-type catalyst could be attributed to the characteristic feature of the well-dispersed metallic Ni species with highly stable spinel structure.

Phenol and phenolic derivatives found in different industrial effluents are highly toxic and extremely harmful to human and the aquatic ecosystem. In the past, trickle bed reactor (TBR), reverse osmosis (RO) and other processes have been used to remove phenol from wastewater. However, each of these technologies has limitations in terms of the phenol concentration in the feed water and the efficiency of phenol rejection rate. In this work, an integrated hybrid TBR–RO process for removing high concentration phenol from wastewater is suggested and model-based simulation of the process is presented to evaluate the performance of the process. The models for both TBR and RO processes were independently validated against experimental data from the literature before coupling together to make the hybrid process. The results clearly show that the combined process significantly improves the rejection rate of phenol compared to that obtained via the individual processes.

Bifunctional hydrodeoxygenation catalysts containing both metal and metal oxide phases are widely employed in biomass upgrading reactions. Determining the oxidation state of metals in such complex reaction media has been challenging. In this work, we developed a high-pressure trickle-bed reactor capable of conducting temperature-programed reduction of catalysts after liquid-phase reactions without exposing the catalyst bed to ambient conditions. Two case studies on metal/metal oxide catalysts employed in key biomass upgrading processes were investigated. The reduction of the RuOx phase in Ru/RuOx/SiO2 occurs at temperatures as low as 115 °C via catalytic transfer hydrogenation reactions using liquid 2-propanol as a hydrogen source. Pretreatment of Ir-ReOx/SiO2 catalyst with H2 in the presence of either liquid cyclohexane or liquid water reduces Re to an oxidation state of +2.6, while the residual ReOx phase cannot be reduced in H2 at up to 900 °C.

In this work, the gas–liquid mass transfer performance of rotating packed bed (RPB) with Al2O3 sphere packing, in term of volumetric liquid-side mass transfer coefficient (kLae), was investigated by CO2-NaOH chemical absorption system. The adsorption performance of Al2O3 spheres was also evaluated by an ink adsorption method. Results showed that the kLae values of RPB with Al2O3 sphere packing were higher than those of RPB with nonporous sphere packing, and over one magnitude order higher than those of trickle bed reactor (TBR) with Al2O3 sphere packing. The ink adsorption, film diffusion and pore diffusion rates of Al2O3 spheres have been greatly improved under the high gravity field, and it has been found that the surface tension was the main driving force of ink adsorption. Moreover, the adsorption kinetics was investigated and the experimental data fitted well with the pseudo-first-order adsorption kinetics model.

This work presents a model for UOP Coker Complex Hydrotreating Process using Aspen HYSYS Petroleum Refining module. The model depends on routinely taken industrial data of process streams during normal operating conditions. Acquired data sets have been tested and screened in order to ensure data validity for building the model and avoiding erroneous results. A detailed kinetic model of hydrotreating reactions in the reactor has been applied. The trickle bed reactor (TBR) model has been validated using 3 months of industrial plant data. In addition, rigorous tray-by-tray simulations for hydrogen sulfide absorption tower and TBR effluent fractionation tower have been utilized to match the performance of the plant’s towers. The model has been used then for studying the effects of different process variables on the plant performance. In addition, the model has been used in optimizing the operating conditions of the process. This optimization showed a potential for notable savings of fuel and energy consumption in the process, while increasing the process productivity.

Phenol is one of the most toxic and harmful pollutants in industrial wastewater streams, the removal of which is therefore of critical importance. The use of reverse osmosis (RO) systems as a means of treating wastewater is continuously growing. This research investigates the effect of operating parameters on the performance of five different multistage RO configurations coupled with a trickle bed reactor (TBR) using model-based simulation. The results were compared, and an analysis was then performed to identify which hybrid TBR and multistage RO arrangement rejected the most phenol content. The basis for comparison was four performance metrics of permeate concentration, rejection, recovery, and specific energy. The study found that the flow rate and concentration have little effect on the operation unless there is a concurrent increase of both. It was also found that the four-performance metrics used were interlinked and affect the quality and quantity of the final freshwater product.

Fil: Manuale, Debora Laura. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Investigaciones en Catalisis y Petroquimica "Ing. Jose Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catalisis y Petroquimica "Ing. Jose Miguel Parera"; Argentina

Product yield optimization in bimodal reaction sequences including degradation has been performed considering three-phase reactors such as the jet loop and trickle bed reactors. The considered reaction network comprises two consecutive homogeneous reaction steps toward intermediates which are converted to the corresponding final products by heterogeneously catalyzed reactions, while the reactant and these intermediates are susceptible to irreversible degradation. In the jet loop reactor, the so-called “homogeneous product” is the main product; hence, the remaining challenge is the reduction of degradation. For the trickle bed reactor, gas−liquid mass phase transfer plays a very pronounced role in its ultimate performance. Higher gas flow rates may be employed in the trickle bed reactor to overcome potential mass-transfer limitations and selectively form the “heterogeneous product”. Lower gas flow rates result in a less effective gas dissolution, and product selectivities change toward the homogeneous product, rendering avoiding degradation difficult.

The catalytic exchange column of countercurrent trickle bed for deuterium removal from hydrogen is simulated based on experimental results along with established reaction and mass transfer models, accounting for the humidification of hydrogen in a catalyst bed filled with platinum/styrene-divinylbenzene copolymer pellets and Dixon rings. Relative deviations of less than 30% are achieved between the experimental and the simulated HD molar fractions at the column outlet. Simulation results indicate that hydrogen humidification exerts a noticeable influence on gas and liquid phase flow rates, leading to an overestimated removal percentage of deuterium when such flow rate variances are neglected. Rate limiting step for the overall gas-liquid isotopic exchange is discussed. Finally, the operation conditions are optimized using the developed model.

In this work, computational fluid dynamics (CFD) has been used to investigate diesel hydrotreating (Hydrodesulfurization (HDS) and Hydrodearomatization (HDA)) in a laboratory scale trickle bed reactor (TBR). In order to investigate these reactions, the 3D model was developed using a multi-phase Eulerian-Eulerian approach, an inter-phase interaction model, a porosity distribution model for the trilobe particles, mass transfer and chemical reactions model. Due to the small dimensions of the reactor, the simulations are carried out at isothermal and transient conditions and the catalyst bed is considered to be fully wetted. In this first phase of the work, a reaction model was used, which was later validated. Then, a counter-current reactor is simulated and the results are compared with a co-current reactor. The analyzed parameters are conversion, pressure drop and liquid holdup and a special attention was given in order to verify how operational changes on pressure, temperature, velocity and gas and liquid flows influence the reactor performance. The influence of porosity on fluid velocity and volume fraction of liquid is also investigated. Finally, the influence of the liquid hourly space velocity (LHSV), temperature, gas-liquid ratio and partial pressure of H 2 S are also discussed. The results for the two types of reactors are similar despite the fact that the counter-current arrangement has achieved lower conversions.

The continuous hydrogenation of a mixture of L-arabinose and D-galactose over a Ru/C catalyst was investigated in a miniaturized packed bed reactor. The reaction is one important step of the transformation process of the naturally occurring hemicellulose arabinogalactan (AG) into valuable sugar alcohols. Process intensification was accomplished by reducing the reactor dimensions to a few millimeters, thus leading to better mass and heat transfer performance. The effect of temperature, pressure and liquid flow rate on the yield as well as byproduct formation will be discussed. Based on a kinetic model derived from batch experiments, a model of the continuous reactor was developed and used for scale-up purposes.

Chemical reactors with new types of packings, such as metallic and ceramic open-pore foams, have become subjects of scientific and engineering interest in the past decades. For trickle bed reactors, the new packing types provide favorable conditions, such as high specific surface area and low pressure drop, which are believed to contribute to an intensification of mass and heat transfer. Here, an attempt was made to model and predict the flow pattern and liquid distribution in a trickle bed reactor with solid foams, using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was adopted, where gas and liquid phases flow co-currently downwards through a reactor with SiSiC ceramic foams as internals. The influence of both mechanical and capillary dispersion was included and studied in detail for foams of two different pore densities and for different initial distribution patterns.

The hydrogenation of Citral in a fixed bed reactor using supercritical carbon dioxide was studied. A numerical model was set up using the commercial software Aspen Custom Modeler®. Applying literature experimental data, a parameter estimation for the kinetic parameters was carried out. A good fit was reached with the presented model. Furthermore, a sensitivity analysis was performed. The influence of process pressure, inlet CO2- and Hydrogen concentration and catalyst particle size on conversion, reactor length, space time yield, yield of the intermediate product 3,7-dimethyl-2-octenal and pressure drop was investigated.

Energy saving is an important consideration in process design for low cost sustainable production with reduced environmental impacts (carbon footprint). In our earlier laboratory scale pilot plant study of catalytic wet air oxidation (CWAO) of phenol (a typical compound found in wastewater), the energy recovery was not an issue due to small amount of energy usage. However, this cannot be ignored for a large scale reactor operating around 140–160 °C due to high total energy requirement. In this work, energy savings in a large scale CWAO process is explored. The hot and cold streams of the process are paired up using 3 heat exchangers recovering significant amount of energy from the hot streams to be re-used in the process leading to over 40% less external energy consumption. In addition, overall cost (capital and operating) savings of the proposed process is more than 20% compared to that without energy recovery option.

While kinetics is independent of either scale or configuration of hydrotreating reactor, hydrodynamics of reactor depend on both. The hydrodynamics of reactor which comprise of phase mass-transfer, catalyst wetting and pressure drop affect its performance significantly and should be addressed adequately while deciding on configuration or scale up issues. This study evaluates and compares the performance of different configurations of commercial VGO hydrotreater by employing mathematical model encompassing kinetics and hydrodynamics. Two configurations have been studied: • Conventional trickle-bed reactor, subdivided into (a) beds in parallel and (b) beds in series. • Pre-saturated one liquid flow (POLF) reactor, subdivided into (a) reactor with single pre-saturator (POLF-SP) and (b) multiple reactors in series with intermittent pre-saturators (POLF-MP). The performance of conventional reactor in series/parallel is found to be superior to POLF configurations. The inferior performance of POLF configurations is attributed to mixed flow behaviour due to recycle as against plug flow behaviour in conventional trickle-bed reactors.

A sorption enhanced-steam methane reforming (SE-SMR) process was investigated in a countercurrent gas–solid trickle flow reactor packed with regularly stacked catalyst. The stacked catalyst was made of corrugated Pt/Ni/Al2O3 plates in the form of static mixers. Experiments were carried out in a temperature range of 550–600 °C, total pressure of 4.0 bar, and water to methane ratio of 4.0 in the reactor feed. Within the investigated conditions, experimental results offered a solid proof of concept for new continuous SE-SMR operation for production of hydrogen where sorbent can be regenerated separately from the catalyst. Experimental data were reasonably well described by a plug flow model for both the gas and solid phases. The mathematical model was further used to optimize the continuous SE-SMR operation: it could be demonstrated that the level of the hydrogen purity in the reactor exit stream could be controlled by a multistage reactor consisting of alternating catalytic active and stainless-steel inert ...

In this paper catalytic hydrogenation of ethylene was studied using liquid propane with 1.5% of ethylene content and hydrogen gas in 30 barg trickle bed reactor under two flow configurations: countercurrent and concurrent. Trickle bed experiments were then performed using an experimental package comprising high pressure pilot reactor, gas chromatograph apparatus, dosing pump and required instrumentation system to compare countercurrent and concurrent sampled data furthermore structured catalyst of alumina–nickel was used as catalytic bed. Trickle bed modeling was achieved using a package of 12 dimensionless two-dimensional homogeneous mass and momentum transfer partial differential equations, the model parameters and kinetic equations. Orthogonal collocation technique was employed to solve developed PDEs. Predicted performance of the trickle bed by mathematical modeling was compared by experimental results and there was good consistency between them. The experimental results showed zero concentration of ethylene through countercurrent flow. Finally, the experimental analysis reports emphasize on zero concentration of ethylene in output of countercurrent bed whilst increasing the Reynolds number did not conclude to nil concentration of ethylene in output of concurrent bed.

Flow regime effect and reactor modeling studies in a gas-liquid downward flow fixed bed reactor were conducted for acetophenone hydrogenation on 1% Rh/Al2O3 catalyst, a relatively complex reaction scheme typical of pharmaceutical applications, using a 7.1 mm ID stainless steel reactor with 0.5 mm catalyst spheres at elevated pressures. A flow regime transition map for trickle and bubbly flows was determined visually in a transparent reactor surrogate and confirmed by monitoring pressure drop fluctuations for different gas/liquid systems, tube/particle materials, and operating pressure and temperature. The flow regime at each operating condition for the opaque stainless steel reactor was identified solely using pressure drop fluctuations. The beneficial effect of bubbly flow on reaction rate was confirmed experimentally at gas and liquid superficial velocity ranges of 0.02–0.19 m/s and 2.5–12 mm/s, respectively, under 80–100 °C, 11–26 bar and 0.04–0.6 M initial substrate concentration. Gas flow rate, temperature, and pressure variations were used to study the effects on reaction performance of partial wetting of the catalyst and of liquid-solid diffusion limited reaction. A reactor model including external/internal mass transfer and flow regime effects was developed using an adjustable parameter to account for partial wetting and flow regime effects. The parameter was fitted using a subset of the experiments, and the model provided good prediction (R2 > 95%) of all remaining experiments.

The homogeneous wet oxidation of phenol, catalysed by Cu(II), has been studied in a trickle-bed reactor. The reactor bed consisted of a ceramic foam made of alumina with a cell density of 20 ppi. This bed is especially suited to promote mass transfer between phases with very low pressure drop. The gas phase (oxygen at 0.6 MPa) was circulated continuously, while the liquid phase (40 mol/m 3 phenol in water) was circulated in discontinuous mode, i.e. with total recirculation of liquid. The experiments were planned to determine the influence of the main operating conditions, i.e. liquid superficial velocity (0.9–3.3 × 10 −3 m/s), Cu(II) concentration (0.41–0.945 mol/m 3 ) and temperature (110–143 °C). Temperature and liquid superficial velocity were found to have the most marked influence in phenol conversion. The use of the foam packing, particularly at high liquid superficial velocities, enhances oxygen mass transfer between phases and increases the efficiency of the process (higher phenol conversion). A mathematical model, based on conservation equations applied to the bulk liquid and liquid film, has been proposed and validated with the experimental results. It has been found that the model is able to predict the experiments within an error of ±10%.

The shale oil hydrogenation experiments were conducted on a fixed-bed reactor with grading of a hydrogenating protective (HP) catalyst, hydrofining (HF) catalyst, and hydrocracking (HC) catalyst. The effects of the reaction temperature and liquid hourly space velocity (LHSV) on product distribution of shale oil hydrotreating were investigated. Three kinds of lumping kinetic models for hydrodearomatization (HDA), hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) were first established and applied in this process. The predicted reactive features and optimized operating conditions for HDS, HDN, and HDA agreed well with experimental results at different catalyst grading ratios, with a relative error of less than 3.8%. In accordance with operating conditions, the model can also be applied in catalyst grading scale calculation, which enhances the theory of shale oil hydro-upgrading application.

Various Ni-based catalysts were tested in the continuous liquid phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in a trickle-bed reactor using water as solvent with the aim to develop an economic and environmentally friendly way for the GVL synthesis. For this purpose, various synthesis methods were used to prepare Ni-based catalysts, which were first screened in batch reactors. Characterization by X-ray diffraction, temperature-programmed reduction, electron microscopy, hydrogen chemisorption, and X-ray absorption spectroscopy showed that slow precipitation using urea resulted in a good Ni dispersion. The dispersion also improved at lower Ni loading, and smaller Ni particles mostly showed an enhanced catalytic performance for the synthesis of GVL. 5 wt % Ni/Al2O3 prepared by wet impregnation showed the highest specific activity for the hydrogenation of LA to GVL (90% LA conversion and 75% GVL yield) featuring an average Ni particle size of 6 nm. Some deactivation of the catalysts was observed, probably due to transformation of γ-Al2O3 to boehmite and sintering of the Ni particles. In addition, reoxidation of Ni particles may additionally lead to deactivation as concluded by comparison with screening studies in batch reactors.

In the present work, a nanocatalyst, γ-Al2O3 nanoparticle-supported CoMo, was prepared experimentally and evaluated through a hydrodesulfurization (HDS) process for removing dibenzothiophene (DBT) from diesel fuel systematically in a trickle bed reactor (TBR). The results of the prepared catalyst characterization tests (scanning electron microscopy, X-ray diffraction (XRD), XRD phase quantification, and Brunner-Emmett-Teller) showed good distribution of active metals (CoMo), difference in surface morphology, and high dispersion of active metals. The catalyst exhibited good metal-support interactions without impacting the surface area significantly. A fully automated TBR reactor was used to evaluate the activity of the prepared catalyst in the HDS process at ranges of operating conditions: temperatures (250-350 °C), pressures (6-10 bar), liquid hourly space velocities (LHSV) (1-3 h-1), and the activity of the prepared catalyst were compared to a commercial catalyst based on Co-Mo/γ-alumina. The results showed an obvious enhancement in the HDS process using the homemade nanocatalyst compared to the commercial catalyst. It has also been found that an increase in temperature led to an increase in the conversion from 68.77 to 91.57%, a little positive effect on conversion when pressure was increased, and a significant decrease in conversion (from 91.57 to 75.58%) as LHSV was increased. A kinetic model was developed for the HDS process to estimate kinetic parameters and apply the parameters in reactor design. The developed model showed that the DBT concentration in diesel fuel can be reduced significantly, 3000-240 ppm, at the optimum experimental conditions.

Among several treatment methods catalytic wet air oxidation (CWAO) treatment is considered as a useful and powerful method for removing phenol from waste waters. In this work, mathematical model of a trickle bed reactor (TBR) undergoing CWAO of phenol is developed and the best kinetic parameters of the relevant reaction are estimated based on experimental data (from the literature) using parameter estimation technique. The validated model is then utilized for further simulation and optimization of the process. Finally, the TBR is scaled up to predict the behavior of CWAO of phenol in industrial reactors. The optimal operating conditions based on maximum conversion and minimum cost in addition to the optimal distribution of the catalyst bed is considered in scaling up and the optimal ratio of the reactor length to reactor diameter is calculated with taking into account the hydrodynamic factors (radial and axial concentration and temperature distribution).

One-step propane partial oxidation to acrylic acid and acrolein has been studied widely. Research on the catalyst systems has been accompanied by investigations of various reactor configurations in order to improve acrylic acid/acrolein yield for achieving industrial applications. Based on the reaction kinetics, lower gas-phase oxygen concentration supports the desired reaction path to the oxygenate products. Therefore, novel reactor concepts that can continuously provide uniform and controllable oxygen concentration have the potential for acrylic acid/acrolein yield enhancement. In this way, alternative reactor technologies from reactor structuring, fluidization to membrane type have been proposed. In this work, the actual state of these efforts is reviewed. The advantages and disadvantages of each concept are pointed out. However, the assessment of a new technology due to the numerous aspects that have to be considered is very difficult. It is suggested that circulating fluidized bed is a much p...

Different flow regimes are known to occur in the interaction of multiphase gas–liquid flows over packed beds of solid particles, such as those observed in trickle bed reactors (TBRs). There are four major flow regimes that are known to occur in downward cocurrent flow in TBRs, namely: trickle, pulse, bubble, and mist flow regimes. In this work, the focus is on macro-scale experimental visualizations and investigations of the flow regimes in a two-dimensional TBR.Experimental observations are made to investigate the development and transition of these flow regimes over a wide range of liquid and gas velocities. Cylindrical particles are placed between two glass plates that are sealed on the sides, and water and air are injected over them using an injection manifold to simulate multiphase flow in a TBR. A diffused light emitting device (LED) light table is used to illuminate the experimental window, while real time images are obtained using a high-speed camera. Flow maps are reported depicting all four regi...

A two-dimensional (2D) computational fluid dynamics model based on discrete lumping approach was used to predict the product yields of a pilot scale vacuum gas oil (VGO) hydrocracking reactor. This model was developed by solving mass conservation equations in conjunction with the continuity and momentum balances in the z-r cylindrical plane. The kinetic parameters of the model were estimated from the experimental data, and validated by using actual values. Results show that the proposed model can appreciably improve the accuracy of the yield prediction in comparison to the predicted value using the 1D model. Moreover, it is confirmed that the order of magnitude of the radial liquid velocity against the axial one is considerably low, and there is no significant pressure drop along the r-direction. Additionally, results show that two-dimensional model is a reliable tool for evaluating the catalyst performance and also for designing commercial reactors.

A trickle bed reactor (TBR) was used to study different process parameters upon hydrogen peroxide direct synthesis. The catalysts used were commercial palladium on active carbon. The influence of pressure (1.75–25 barg), temperature (5–60°C), liquid flow rate (2–13.8 ml·min-1), gas flow rate (3.4–58.5 ml·min-1), catalyst amount (90–540 mg), Pd percentage on the support (5% wt., 10% wt. and 30% wt. Pd/C) as well as promoter concentrations (0.0005–0.001 m) were all varied as process parameters to better understand the behaviour of the system. By contrast, the gas phase molar composition of the feed (4:20:76=H2:O2:CO2) was kept constant. The strong influence between liquid flow rate, gas flow rate and catalyst amount were identified as the key parameters to tune the reaction, and related to the activity of the catalyst. In essence, these parameters must be carefully tuned to control the hydrogen consumption. The maximum productivity (289 μmol H2O2·min-1) and yield (83.8%) were obtained when a diluted bed of 30% Pd/C was applied. The H2O2 hydrogenation was studied in order to understand its role in the H2O2 direct synthesis reaction network. The hydrogenation reaction mechanism and the role of NaBr were identified thanks to the experiment proposed in the present work. Consequently, understanding the whole reaction mechanism from the process conditions studied led to a deeper understanding of all of the phenomena involved in the H2O2 direct synthesis.