Feed Space Velocity Research Articles

The effect of recycle stream on slurry-phase hydrocracking of vacuum residue: An experimental and modeling approach

The effect of the recycle stream on slurry-phase hydrocracking (HCK) of vacuum residue was examined using a continuous bench-scale unit with the aim of attaining process optimization. This was achieved through a model-based approach that links experimental investigations, kinetic modeling, and model-based optimization. The experiments were conducted at various reaction temperatures, liquid hourly space velocity of fresh feed (LHSVFF) and recycle ratios at a pressure of 160 bar, with the fresh feed containing 1000 wt. ppm of molybdenum. The HCK kinetic model was modified to incorporate the recycling effects and accurately predict the experimental data. The adapted model confirmed that the unconverted residue in recycle operating mode (ROM) became more refractory. By implementing the modified kinetic model in a dynamic Simulink model, the prediction accuracy of RES conversions and product yields can be improved by up to 25.1 wt.% in the case of the lowest conversion. A sensitivity analysis using the dynamic model showed that the temperature exerted a greater impact on the RES conversion and recycle ratio in ROM. An operational stability index was also proposed to prevent operation failure in ROM. Finally, an optimal operating condition from the parametric study was found to meet several process goals simultaneously.

HYDROCATALYTIC PROCESSING OF FUEL OILS WITH THE USE OF NANOCATALYSTS BASED ON NICKEL AND ZINC

The article presents the results of a study of hydrocatalytic processing of two fuel oils in the presence of nanocatalytic systems in the form of oil-soluble precursors based on nickel and zinc. The process was carried out on a pilot plant for hydroprocessing with a flow reactor at a temperature of 440 ℃, a hydrogen pressure of 6 MPa, a feed space velocity of 1.0 s-1, and a hydrogen circulation ratio of 1000 nl/l. The catalyst efficiency was evaluated by changes in the material balance, in hydrogenate desulfurization degree, in 450+ °C fraction conversion degree, and by changes in density and hydrogenate refractive index. An analysis of material balances showed that the addition of nanocatalyst precursors increases the 180–350 °C fraction yield, reduces the coke yield on the fixed layer, which is a layer of ceramic balls, and reduces the 450+ °C residual fraction yield. The gas and gasoline fraction yield is slightly reduced. The analysis of hydrogenates showed a decrease in sulfur content, a decrease in density and refractive index in hydrogenates obtained during the hydroprocessing of raw materials with the addition of nanocatalyst precursors. The optimal concentrations of catalysts were experimentally determined; for nickel, the concentration is 0.1 wt %, and for zinc is 0.15 wt %. A comparison of two methods for the synthesis of nanoscale catalytic systems in raw materials was made: directly in the reaction zone in situ and outside the reaction zone ex situ. The method for synthesizing nanoscale catalytic systems outside the reaction zone makes it possible to further increase the feedstock conversion, the hydrogenate desulfurization degree, and the hydrogenate quality.

The effect of testing conditions on the time of establishing a steady-state activity of the catalysts for the second hydrocracking step

Catalysts for the second hydrocracking step were tested under different conditions in order to reduce the time of establishing their steadystate activity. The tests were carried out at a laboratory bench under the conditions close to industrial operation and typical of the second hydrocracking step. The introduction of an additional step at the onset of testing with the increased temperature and feed space velocity as well as the use of a dimethyl disulfide solution in decane as a sulfurization mixture were shown to considerably reduce the duration of experiment. Conditions of the preliminary step were selected so as to preserve the catalyst selectivity toward the diesel fraction.

Hydrogen-permeable DDR zeolite membrane packed with Zn/HZSM-5 catalyst for methane co-aromatization with ethylene

Co-aromatization of methane (CH4) and ethylene (C2H4) over a membrane reactor (MR) using hydrogen-permeable DDR zeolite membrane packed with Zn/HZSM-5 catalyst was studied for the first time. The adopted DDR zeolite membrane showed high H2 selectivity for separations of binary H2/CH4 and trinary H2/CH4/C2H4 mixtures. Typically, the selectivities for H2/CH4 and H2/C2H4 were 40 and 29 for trinary mixture separation at room temperature, respectively. The effects of reaction temperature, methane-ethylene feed ratio, space velocity and H2 removal on the membrane reaction performance were investigated systematically. The membrane reactor can achieve 8.43% methane conversion with BTX selectivity of 80.68% within 1 h under the optimal reaction conditions (reaction temperature 450 °C, methane-ethylene feed ratio 3:2, weight hourly space velocity (WHSV) 800 mL/(gcat h), sweep helium flow rate 15 mL/min). Compared to a fixed-bed reactor (FBR) with similar reaction condition, the achieved methane conversion and BTX yield were improved by ∼42% and ∼10%, respectively, due to the timely removal of H2 from the reaction system. The membrane also showed good stability, and the methane conversion maintained at about 7% for about 30 h. After burning the coke formed on the catalyst, the initial reaction performance can be restored, showing a good regeneration ability.

Steam Conversion of Ethane and Methane–Ethane Mixtures in Membrane Reactor with a Foil from Pd–Ru Alloy

The features of steam conversion of ethane and methane-ethane mixtures containing 5, 10 and 15% ethane in a membrane reactor with a 30 μm thick Pd–Ru foil at temperatures of 1800 and 3600 h–1 and steam/feed rations of 3 and 5 have been investigated. Comparative experiments with “non-membrane” reaction have shown that in the membrane reactor the feedstock conversion to form H2 and CO2 increases and ethane hydrocracking decreases. Increasing the rate of H2 recovery through the membrane by permeate evacuation leads to an increase in the yield of H2 and CO2. With a decrease in the steam/feed ratio from 5 to 3, the ethane hydrocracking and the rate of carbon deposits formation increases. Optimal conditions for steam conversion of ethane and methane-ethane mixtures are T = 773 K, feed space velocity of 1800 h–1 and steam/feed ratio of 5. The established regularities are similar to those obtained earlier for other types of raw materials (mixtures of methane with propane, propane, n-butane, a mixture simulating the average composition of associated petroleum gas) in this membrane reactor.

Micro-mesoporous catalysts based on ZSM-5 zeolite synthesized from natural clay nanotubes: Preparation and application in the isomerization of C-8 aromatic fraction

Micro-mesoporous zeolite with ZSM-5 morphology was successfully synthesized by soft template and template-free methods using natural halloysite aluminosilicate nanotubes as a hard template and a source of aluminum and silicon. Formation of ZSM-5 crystal structure was confirmed by XRD. Textural properties and structural characteristics of functional materials, supports, and Pt-containing catalysts were examined by N2 physisorption, NH3-TPD, Py-FTIR, TEM, SEM, XRF techniques. Specific BET surface area of ZSM-5 zeolite prepared using TPABr as an organic template (ZSM-5(t):HNT) is 583 m2/g, whereas for the template-free counterpart (ZSM-5(tf):HNT) it reaches 225 m2/g. According to the Py-FTIR data, concentrations of Brønsted acid sites for ZSM-5(t):HNT and ZSM-5(tf):HNT are 295 and 93 μmol/g, whereas concentrations of Lewis acid sites are 79 and 41 μmol/g, respectively. Activity and selectivity of Pt catalysts based on the micro-mesoporous ZSM-5 zeolite-derived supports were evaluated in isomerization of C-8 aromatic fraction depending on the process conditions (temperature, feed space velocity). Because of the hierarchical micro-mesoporous structure, both catalysts provide xylenes transformation through the two isomerization routes (intra- and intermolecular). However, for the catalyst based on support synthesized through the template-free methods, the monomolecular reaction route is more preferable, and therefore the number of side reactions (disproportionation, transalkylation, and dealkylation) decreases.

Investigating a HEX membrane reactor for CO2 methanation using a Ni/Al2O3 catalyst: A CFD study

In this contribution, viability of processing of the flue gas streams as a source of carbon dioxide for the thermo-catalytic conversion was investigated. For this purpose, a Ni/Al2O3 commercial catalyst with known chemical kinetics was utilized. Moreover, a transient mathematical model for dynamic catalyst deactivation was developed and validated with experimental results available in the open literature. The developed model was then utilized to understudy an air-cooled membrane reactor. Different tube configurations were understudied and compared to choose the conditions under which high conversion was feasible. Sensitivity analysis revealed that, the space velocity, cooling rate, and feed distribution were all considered to be critical factors. It was revealed that, the presence of membrane resulted in higher conversion through the undertaken reactor. It made it possible to enhance reaction yield of non-membrane reactor through evenly distributing hydrogen along its length. A designed heat-exchanger (HEX) membrane reactor achieved 99% CO2 conversion when the coolant flow rate was reached to 10% of the coolant gravimetric flow rate, feed space velocity was set at 100 h−1 and the feed pressure was set at 10 bars.

Thermocracking of a heavy fraction of the oil residue in a mixture with shale

The process of tar thermal cracking in a mixture with crushed oil shale to obtain components of motor fuels and raw materials for the process of thermal cracking is investigated in this paper. The optimization results of technological parameters (shale concentration, temperature, and duration) are presented and the material balance (mass.%) of the process is made. It was found that during single-stage processing under relatively mild conditions (5 MPa, 425C, feed space velocity of 1.0 h-1), a deep destruction of tar is achieved (the yield of the gasoline fraction from boiling point to 200C is ~12 wt.%; medium distillates with boil. point 200370C-43-44 mass.%; raw materials for thermal cracking with boil. point above 370C ~15-16 wt.% on per the original tar). The generating coke-like products and the V and Ni contained in the raw materials are deposited on the mineral part of the shale and removed from the reaction zone with the liquid products of the process.

Selective removal of boron from industrial wastewater containing high concentration of ammonia by radiation grafted fibrous adsorbent in fixed bed column

Removal of boron from real industrial wastewater containing high concentration of ammonia was investigated using a fibrous adsorbent bearing glucamine groups obtained by green method. The adsorbent was prepared by radiation induced emulsion grafting (RIEG) of glycidyl methacrylate (GMA) onto nylon-6 fibres and subsequent treatment with N-methyl-D-glucamine (NMDG) under controlled conditions. The performance of the obtained adsorbent was tested for adsorption of boron from a real industrial wastewater containing high concentration of ammonia in comparison with a synthetic aqueous solution using in a fixed bed-column under different feed space velocities (SV). The dynamic adsorption data of the fixed column was tested against three most common mathematical adsorption models: Yoon–Nelson, Thomas and Modified Dose-Response (MDR) models to predict breakthrough curves and determine the column design parameters. The results showed that the experimental breakthrough curves were best fitted by MDR model. The adsorbed boron was eluted with 1 M HCl solution and the adsorbent was regenerated for stability evaluation using 5 adsorption/desorption cycles. The results suggest that the obtained adsorbent has a strong potential for industrial pilot scale boron removal applications.

Steam Conversion of Propane in a Membrane Reactor with a Commercial Nickel Catalyst

The propane conversion in a membrane reactor with NIAP–03-01 commercial Ni catalyst at temperatures of 673, 723, 773, and 823 K, feed space velocities of 1800 and 3600 h–1, and steam/propane ratios of 5 and 7 was studied. The Н2 removal through the membrane leads to an increase in the conversion of the feed to Н2 and СО2 formed by the water-gas shift reaction. The conversion in this reaction increases when the rate of the Н2 recovery through the membrane is increased by the permeate evacuation. In the temperature interval 773–823 K, the feed conversion is 100%, and about 90% of high-purity Н2 is recovered from the reaction mixture. An increase in the feed/catalyst contact time leads to a decrease in the feed conversion to the target products and to an increase in the rate of carbon deposit formation. The regularities of the steam conversion of propane in a membrane reactor are similar to those found previously for n-butane with the same catalyst and under the same conditions.

Modeling of Complex Reforming Reaction of Methane by Response Surface Methodology.

The objective of this study was to investigate the effect of feed composition, space velocity, and reaction temperature on methane/carbon dioxide conversion and H₂/CO ratio. Independent variables were feed ratio, flow rate, and reaction temperature while CH₄ conversion, CO₂ conversion, and H₂/CO ratio were set as dependent variables in the complex reaction of methane. As a result of mixed reforming reaction of methane through RSM modeling method, the reaction temperature was found to have the greatest influence. This is because the reaction temperature has the greatest influence on the reaction rate and equilibrium state as a factor directly affecting the thermodynamic value of the catalyst.

Synthesis of Modified Catalyst for Liquid Phase Alkylation of Benzene with Ethylene

Highly efficient binder-free catalysts, based on zeolite Y, for the liquid-phase alkylation of benzene with ethylene have been synthesized. The catalysts have been modified by treating with aqueous solutions of hydrochloric and citric acids to remove extra-framework aluminum formed during the partial dealumination of zeolite Y. The synthesized catalysts have been tested in the alkylation of benzene with ethylene at a temperature of 200°C, a pressure of 2.5 MPa, a benzene : ethylene molar ratio of 5 : 1, and a benzene feed space velocity of 5 h−1. Over the modified catalyst, the ethylbenzene (EB) content in the alkylate increases by 27% and the EB selectivity increases by 5% compared to the initial Y zeolite.

Acrylic Acid Production by Gas-Phase Dehydration of Lactic Acid over K+-Exchanged ZSM-5: Reaction Variable Effects, Kinetics, and New Evidence for Cooperative Acid–Base Bifunctional Catalysis

This study investigates the effects of reaction variables (including space velocity, temperature, and partial pressures of LA and H2O) and acidic and basic additives on the gas-phase dehydration of lactic acid (LA) for acrylic acid (AA) production, using an aluminum-rich K+-exchanged ZSM-5 zeolite (molar SiO2/Al2O3 = 27, K/Al = 1.0, K/Na = 8) identified among many high-silica zeolites as the most efficient catalyst in our prior work (Yan et al. ACS Catal. 2017, 7, 538−550). Under widely varied reaction conditions (340–380 °C, feed GHSV: 9,500–38,000 h–1, 1.8–11.7 kPa LA, 52.0–73.0 kPa H2O), the catalyst offers not only high selectivity for AA (>75 mol %) but also long-term catalytic stability. Rate equations and their associated kinetic parameters for LA consumption and AA production are obtained by measuring the kinetically relevant catalytic rates under high feed space velocity (GHSV ≥ 57,000 h–1). Acidic (CO2, acetic acid, and trifluoroacetic acid) and basic (NH3) additives are added, respectively, to the reaction feed to investigate their effects on performance of the working catalyst. While addition of either CO2 or acetic acid shows no effect on the catalyst performance, the addition of either NH3 or trifluoroacetic acid causes significant decline in both the catalyst activity and selectivity for AA production, due to poisoning of the surface acidic sites by NH3 or basic sites by trifluoroacetic acid. These data well highlight the excellent catalytic performance of the investigated catalyst and offer a new piece of evidence in support of the cooperative acid–base bifunctional catalysis for the LTA reaction.

Detection of Steady State Multiplicity during Dimethyl Ether Conversion Catalyzed by ZnO/γ-Al2O3 Composite: Effect of Coke and Hydrogen Peroxide

The heterogeneous catalytic conversion of dimethyl ether (DME) to 1,3-butadiene and butylenes in the presence of a ZnO/γ-Al2O3 catalyst in a wide range of temperatures, feed space velocities, and reactant concentrations has been studied. It has been found that temperature regions of 380–420 and 440–480°C, which are conventionally designated as low-temperature and high-temperature regions, differ in the laws governing the occurrence of the process associated with the specificity of coking of the catalyst surface and a redistribution of the surface concentration of Bronsted and Lewis acid sites. A hypothesis of a change of the catalytic process mechanism upon the transition of the reaction into the high-temperature region has been put forward and confirmed by the occurrence of a hysteresis detected in this temperature range. The effect of hydrogen peroxide on the hysteresis parameters and the steady state stability during DME conversion has been shown.

Relation of Structural and Chemical Parameters of Tar Hydroconversion Residue to Catalytic Properties of Nanosized Catalysts Based on Mo, Co, Ni, Al Compounds

At a pilot plant with a flow reactor, the hydroconversion of oil vacuum distillation residue (tar) was studied at a hydrogen pressure of 7 MPa, a temperature of 445°C, a feed space velocity of 2 h–1 in the presence of suspensions of nanosized particles of catalysts obtained in situ in the reaction zone from previously prepared in the feed of reverse emulsions of aqueous solutions of precursors: salts of molybdenum, nickel, cobalt, and aluminum. Based on the data of elemental analysis and 1H NMR spectra, the structural parameters of the hydrogenated feed vacuum distillation residues, are determined. The relationship between the structural and chemical parameters of the residues, conversion of raw materials, coke yield, and catalyst composition was established. Tar conversion and unsaturation of the vacuum residue, as structural parameter, increase in the series of Mo–Al, Ni, Mo–Co–Al, Mo, Mo–Co, Mo–Ni, Al catalysts.

The catalytic cracking of the off-spec polyisoprene rubber thermolysis products

The catalytic cracking of the off-spec polyisoprene rubber thermolysis products over a mesoporous zeolite has been studied on a laboratory unit with a fixed-bed reactor. The effect of the reaction temperature and the feed space velocity on the feedstock conversion degree and the yield of gas and gasoline has been studied. The data obtained has shown that at rates below 2 h-1, a high gas generation and a low yield of liquid products are observed, while at rates above 3 h-1, the total yield of gas and gasoline decreases. In the course of the work, it has been noted that the reduction in conditional conversion occurs with an increase in the feed rate. The maximum yield of gasoline observed at a feed rate of 3 h-1 and amounted to 35.6 %, gas yield was inversely proportional to the feed rate, and the coke yield changed slightly. With an increase in the feed rate, the content of C3-C4in gas increases. To achieve high conversion or a high gasoline yield, the optimal feed rate should be 2 and 3 h-1, respectively. The products obtained in this process can be used as the motor fuel components.

Sunflower Oil Hydrodeoxygenation in the Presence of NiMoS/B2O3–Al2O3 Catalysts

It has been shown that borate-containing alumina can be used as a support for sunflower oil hydrodeoxygenation catalysts at 380°C, 4.0 MPa, and a feed space velocity of 1 h–1 with a liquid product yield of 81–85 wt %. It has been found that, with an increase in the boron oxide content in the catalyst, owing to an increase in the catalyst acidity, the fraction of isoalkanes in the products increases to 77–78% and the contribution of decarboxylation/decarbonylation reactions to the formation of the products increases.

Hydrofining of the Overhead Products of the Liquefaction of Coal from the Mamytskoe Deposit

The hydrogenation process of coal distillates with bp 180–360°C in the presence of Mo- and Co-containing catalysts supported on the surface of skeletal nickel (Raney Ni) was studied. It was established that, in the presence of a catalyst containing 5% Mo/Ni-Re + 7% Co/Ni-Re at a pressure of 10 MPa, a temperature of 400°C, and a feed space velocity of 1.0 h–1, phenols and nitrogen bases were completely removed; sulfur and unsaturated compounds were hydrogenated by 95.4 and 94.7%, respectively; and aromatic hydrocarbons were hydrogenated by 69.7%. The hydrofined distillate fractions with bp 180–360°C meet the requirements of GOST [State Standard] R 52368-2005 (Russia) and the EN 590-2004 EU standard for low-sulfur diesel fuel in terms of their physicochemical and operational properties, and hydrotreated gasoline can be used as a component of low-octane gasoline.

Steam Reforming of Methane and Its Mixtures with Propane in a Membrane Reactor with Industrial Nickel Catalyst and Palladium–Ruthenium Foil

Steam reforming of methane and its mixtures containing 5 and 10% propane has been studied in a membrane reactor with an industrial nickel catalyst NIAP-03-01 and a membrane in the form of 30-μm foil made of a Pd–Ru alloy. At T = 823 K and a feed space velocity of 1800 h−1, the almost complete methane conversion is achieved, the selectivity for CO2 is more than 50%, and about 80% H2 is recovered from the reaction mixture. High conversion of CH4 in the membrane reactor under mild conditions allows the steam reforming of its mixtures with C2+ alkanes to be conducted in a single process, as shown by the example of model mixtures containing C3H8. Under selected conditions (T = 773 or 823 K, a feed space velocity of 1800 or 3600 h−1, a steam/methane ratio of 3 or 5, atmospheric pressure), almost complete C3H8 conversion is observed. The main “undesirable” reaction is methanation, leading to a decrease in the CH4 conversion. In the system under study, CH4 is formed with an increase in the feed space velocity. Methanation occurs as a result of C3H8 hydrocracking at a steam/feedstock ratio = 3 or the hydrogenation of CO2 as this ratio is increased to 5. The optimal conditions for steam reforming of methane mixtures containing up to 10% C3H8 are T = 823 K, steam/feedstock ratio = 5, and the feed space velocity of 1800 h−1. Under these conditions involving evacuation of the permeate, the feedstock conversion is complete, the selectivity for CO2 is 50%, and more than 70% H2 is recovered from the reaction mixture.

Study of MoO3-γAl2O3 catalysts behavior in selective catalytic reduction of SO2 toxic gas to sulfur with CH4.

In the present study, a detailed investigation was carried out on MoO3 alumina-supported catalysts behavior in selective catalytic reduction of SO2 to sulfur with CH4. At first, four different molybdenum catalysts with weight rates of 0, 5, 10, and 15 were impregnated on γ-alumina to be characterized using XRD, SEM, BET, BJH, and N2 adsorption. Then, to find the most active catalyst, temperature dependency test was performed on all of the prepared catalysts and the result representing Al2O3-Mo10 as the best catalyst. In next step, the effects of feed gas composition, space velocity, and long-term activity, as an important industrial factor, were tested on Al2O3-Mo10. It was revealed instantaneously from the beginning, MoO3 specie started to convert mainly into MoS2 and MoO2, and a minor part into Mo2C, which is terminated after 750min achieving a stable condition. Thereafter, SO2 conversion and sulfur selectivity increased from 85.8 to 89.4% and 99.4 to 99.7%, respectively. XRD graph of the used catalyst and TPO thermogravimetric/mass-spectra proved possible happening of the proposed mechanism in long-term activity. At the end, mean activation energy was determined based on Arrhenius model in temperature range of 550 to 800°C, with a value of 0.33eV for Al2O3-Mo10.