Conventional Fixed-bed Reactor Research Articles

Microwave-Assisted dry reforming of toluene as a model tar compound using low-cost iron catalyst for syngas clean-up

Gasification of waste feedstock such as biomass, waste plastics suffers from high tar yields during hydrogen-rich syngas production. The presence of tars result in lower quality syngas, lower syngas yields, reactor blockage, reactor down time, and costly maintenance. Therefore, removal of tar from syngas during gasification is essential. Catalytic reforming of tars via in-situ syngas cleanup is an effective way of mitigating tars. This work explores the possibility of microwave-assisted catalytic dry reforming of tars for syngas production. Due to its chemical complexity, toluene, which is one of the main tar constituents, could be used as a model tar compound. Toluene dry reforming was studied using the Fe/Al2O3 catalyst under CO2 under the temperature range of 400–700 ℃. The toluene reforming reaction was conducted using microwave and conventional thermal reactors. Under microwave irradiation, CO2 and toluene conversions are boosted to 80% at 500 ℃. Hydrogen and carbon monoxide yields were approximately five times and ten times higher in the microwave reactor at 500 ℃, respectively, compared to the productions obtained in the conventional fixed-bed reactor at 700 ℃. Filamentous carbon was also produced as a valuable side product to improve the economy of this process and such value-added carbon was only observed in the microwave reactor. Three reaction pathways were observed during microwave reaction: the toluene decomposition produces an initial hydrogen and carbon deposit on the catalyst; the formation of methane and benzene suggests toluene hydrodemethylation as a secondary reaction; and toluene hydrogenolysis forms light alkanes such as methane, and through reforming reaction under CO2 to syngas.

Multiple-objective optimization on ammonia decomposition using membrane reactor

Ammonia plays a key role in the renewable hydrogen economy nowadays, thus, the efficiency of ammonia decomposition for hydrogen production becomes an important research topic. In this study, a numerical model was built to study the performance of ammonia decomposition using a membrane reactor and Ru/Al2O3 catalyst under various operating conditions such as feed NH3 temperature and volume flow rate as well as retentate side pressure. The reactor performance was characterized by ammonia conversion, hydrogen recovery, and recovered hydrogen flow rate. Pre-exponential factor and activation energy of ammonia reaction rate were obtained by equilibrium conversion and two-step parametric sweeping. It was found that ammonia conversion can be increased by about 33% compared to a conventional fixed-bed reactor under the same operating conditions. H2 recovery can be enhanced when the reactant inlet temperature and the pressure difference between the retentate and permeate sides increase. The increase in feed NH3 flow rate (gas hourly space velocity, GHSV) decreased the ammonia conversion and H2 recovery. An optimum GHSV that results in a maximum recovered H2 flow rate can be found. Finally, optimum operation conditions for maximizing the hydrogen recovery and recovered hydrogen flow rate were analyzed using the multi-objective Non-dominated sorting genetic algorithm-II (NSGA-II). It was found that maximum H2 recovery with a value of 79.7% can be obtained under the conditions of inlet temperature of 336 °C, GHSV of 900 h−1, and retentate side pressure of 9.9875 bar. The maximum recovered hydrogen flow rate with a value of 9.55×10−14(mol·s−1) can be obtained under the conditions of an inlet temperature of 394 °C, GHSV of 1315 h−1, and retentate side pressure of 9.9879 bar.

Conceptual design of novel self-heating reactors for bisphenol A (BPA) synthesis with improved performance

This work proposes a novel conceptual design of bisphenol A (BPA) reactors that can prevent crystallization of BPA during reaction by introducing heat pipes or an acetone evaporator into the fixed bed reactor such that the bed temperature distribution can be adjusted via exploiting the reaction heat. Four reactor models describing the spatial distributions of concentration and temperature in the bed are developed for the conventional fixed bed reactor and three improved types, respectively. The validity of the present new designs is demonstrated by simulation covering industrially relevant conditions and the results show that the addition of an acetone evaporator significantly improves the production conditions and reduce energy consumption without decreasing the conversion.

Selective Methanol Oxidation to Green Oxygenates—Catalyst Screening, Reaction Kinetics and Performance in Fixed-Bed and Membrane Reactors

Experimental and simulation-based investigations are carried out for the selective oxidation of green methanol to the oxygenates dimethoxymethane (DMM) and methyl formate (MF), including an initial catalyst screening, the derivation of a reaction kinetic model, and a feasibility study of a fixed-bed and a membrane reactor with oxygen distribution. The catalyst screening of different supports and loading of vanadium revealed a 6.6 wt.-% VOx/TiO2 catalyst offering the highest potential to the formation for the target products. Kinetic experiments performed in a broad range of operation conditions, e.g., residence time, temperature, and oxygen concentration, are used for the postulation of a reaction network, providing the basis for mathematical modeling of the individual five reaction rates with a reduced mechanistic approach. A simulation study based on the derived reaction kinetics and parameters revealed the high potential of a distributed oxygen dosing at high residence times, outperforming the conventional fixed-bed reactor by up to 6% in the yield of DMM and up to 19% in the yield of MF. The formation of DMM is favored at low temperatures, whereas the formation of MF is supported by high temperatures.

Prospect of Direct Dimethyl Ether Production from CO2: Reactor Design Development

The increasing emissions of carbon dioxide (CO2) and volatile hydrocarbons via burning of fossil fuels result in a significant amount of global warming and air pollution. With the concern over the impact of fossil fuel to the environment, the interest in alternative fuel production from the CO2 generated through utilization of new technologies has risen rapidly. Several clean alternative fuels, including dimethyl ether (DME) have been investigated for a more sustainable and greener environment. DME has a high cetane number but produces much lower NOx emission upon combustion. DME is typically synthesized using syngas based on conventional indirect DME route, where the process begins with conversion of syngas into methanol and subsequently dehydrated to DME in separate units. Recently, a direct single-step route to produce DME through dehydrogenation of CO2 and dehydration of methanol by utilising a novel bifunctional catalyst has been investigated. In direct DME, the dehydrogenation and dehydration occur simultaneously in a single reactor, which eliminate the need for a methanol production plant. However, the use of conventional fixed-bed reactor (FBR) for the direct DME synthesis causes many challenges including catalyst deactivation, where water appears in the reaction area, limiting the conversion of CO2 reactants into DME and consequently, the DME yield. It is also essential to manage the exothermic heat generated from the catalyst for better DME yield. In order to overcome these hurdles, several types of reactors have been proposed such as fluidized bed reactor, slurry reactor, microreactor and catalytic membrane reactor. In this paper, different types of reactors are first discussed and its applications related to the direct DME production from CO2 are highlighted. Finally, the challenges and difficulties of reactor development are addressed and future direction is outlined.

Deactivation kinetic study on vapor phase Beckmann rearrangement of cyclohexanone oxime and design of the multi-layer inclined channel bionic reactor

The optimal design of the reaction system of a large-scale industrial vapor phase Beckmann rearrangement of cyclohexanone oxime to caprolactam process requires both deactivation kinetics and reactor optimization. The deactivation kinetics was study in a micro fluidized bed reactor with online catalyst particle sampling system. An empirical coke formation rate equation was obtained based on time evolution of coke amounts. A Langmuir-Hinshelwood kinetics with deactivation factor based on coke amount was developed. Based on the obtained deactivation kinetics, a Multi-layer Inclined Channel Bionic Reactor was designed as a substitute of the conventional fixed-bed reactor. The hierarchical structure has four levels with inclined channel implementation in the third and fourth level to reduce the pressure drop and improve the flow distribution uniformity. The optimized massive structure of the Multi-layer Inclined Channel Bionic Reactor designed for 200 thousand tons of CPL productivity has a total pressure drop lower than 2kPa, and the maximal relative difference of the bed infiltration velocity is about 11 %.

Combustion reactivity of chars pyrolyzed from low-rank coal using a fixed bed reactor installed with internals

Pyrolysis of low-rank coal could contribute toward the goal of upgrading coal quality, chemical feedstock and fuel production. This research investigated the combustion reactivity of char pyrolyzed from a low-rank sub-bituminous coal using a conventional fixed bed reactor and a novel reactor with internals at 0 kPa and − 40 kPa gauge pressures. Proximate and ultimate analyses showed that the novel reactor reduced char’s fuel ratio by 46% and 54% at 0 kPa and − 40 kPa respectively. The chars derived from the novel reactor also had a higher order of carbonaceous structure and active sites, as supported by the increment in both IG/IALL and ID3/(IG+ID2+ID3) area ratios obtained from a Raman spectrometry analysis. From a non-isothermal combustion analysis, it was found that the ignition temperature of char derived from the novel reactor was 24–40 °C and 30–45 °C lower at 0 kPa and − 40 kPa respectively. A micro fluidized bed reactor analyzer was used for an isothermal differential analysis and it showed that chars produced from the novel reactor had an average combustion activation energy of around 77.3 kJ·mol−1, which was 23% and 10% lower than chars obtained from the conventional reactor at 0 kPa and − 40 kPa respectively. Overall, the novel reactor produces chars with more desirable combustion quality and, therefore, provides the opportunity for more low-rank coal to be upgraded and utilized more effectively as a fuel source for energy sustainability.

Process Design and Techno-Economic Assessment of biogenic CO2 Hydrogenation-to-Methanol with innovative catalyst

A small-scale 10 ton per day methanol (MeOH) synthesis plant, from CO2 and hydrogen, is designed and simulated with Aspen Plus and a techno-economic analysis is conducted. The e-fuel (MeOH) is produced in a conventional fixed bed reactor featuring an innovative Cu/Zn/Al/Zr catalyst, converting biogenic CO2 from a biogas upgrading plant with H2 produced by a grid powered PEM electrolyzer. The process is thermally autonomous as a result of heat integration and combustion of purged unconverted reactants. A sensitivity analysis is carried out in order to evaluate and compare the impact of the different technical (purge fraction, Gas Hourly Space Velocity and Pressure of the methanol synthesis) and economic parameters (Capital Charge Factor, electricity and H2 cost) on the Levelized Cost Of Methanol (LCOM). Results show that, although the energy efficiency is greater (47.4 % electricity to methanol conversion) in the scenario with “self-sufficiency” in which all the net heat required by the process is provided by off-gas streams, the case with the highest profitability is the one with maximum methanol yield and, therefore, minimum purge and non-zero thermal energy import (provided by a biogas boiler). The best case scenario features a LCOM equal to 1,361 €/tonMeOH, with a GHSV of 7,500 h−1 and synthesis reactor operating at 70 bar, 250 °C. H2 production cost is the key variable and shall be reduced from the base case value of 5.8 €/kgH2 to 1.6 €/kgH2 in order to make the CO2 to methanol plant competitive with a MeOH market price of 550 €/tonMeOH; synthesis reactor operating conditions have more limited impact from a cost perspective, except for the purge fraction that shall be optimized to maximize the amount of MeOH produced.

High-entropy alloy anode for direct internal steam reforming of methane in SOFC

High-entropy alloy (HEA) anode and reforming catalyst, supported on gadolinium-doped ceria (GDC), have been synthesized and evaluated for the steam reforming of methane under SOFC operating conditions using a conventional fixed-bed catalytic reactor. As-synthesized HEA catalysts were subjected to various characterization techniques including N2 adsorption/desorption analysis, SEM, XRD, TPR, TPO and TPD. The catalytic performance was evaluated in a quartz tube reactor over a temperature range of 700–800 °C, pressure of 1 atm, gas hourly space velocity (GHSV) of 45,000 h−1 and steam-to-carbon (S/C) ratio of 2. The conversion and H2 yield were calculated and compared. HEA/GDC exhibited a lower conversion rate than those of Ni/YSZ and Ni/GDC at 700 °C, but showed superior stability without any sign of carbon deposition unlike Ni base catalyst. HEA/GDC was further evaluated as an anode in a SOFC test, which showed high electrochemical stability with a comparable current density obtained on Ni electrode. The SOFC reported low and stable electrode polarization. Post-test analysis of the cell showed the absence of carbon at and within the electrode. It is suggested that HEA/GDC exhibits inherent robustness, good carbon tolerance and stable catalytic activity,` which makes it a potential anode candidate for direct utilization of hydrocarbon fuels in SOFC applications.

Development of Highly Active Silica-Supported Nickel Phosphide Catalysts for Direct Dehydrogenative Conversion of Methane to Higher Hydrocarbons

The direct dehydrogenative conversion of methane (DCM) to higher hydrocarbons was investigated over silica-supported nickel phosphide catalysts (NixPy/SiO2) over 1023 K. NixPy/SiO2 catalysts were prepared by precipitation method to promote formation of nickel phosphide (Ni2P) as an active phase for the DCM reaction. Characterization studies of the NixPy/SiO2 catalysts with different P/Ni molar ratios were conducted by a X-ray diffraction analysis, a H2-temperature-programmed reduction spectrum, a scanning electron microscopy image, a X-ray absorption spectroscopy and a N2-adsorption measurement. Catalytic activity tests for the DCM reaction were conducted using a conventional fixed-bed reactor. Products of C2H4 (ethylene), C2H6 (ethane), C2H2 (acetylene), C3H6 (propylene), C6H6 (benzene), C7H8 (toluene), C10H8 (naphthalene) and H2 were analyzed by GC-TCD and GC-FID instruments. Different degrees of the Ni2P phase and character were observed for the NixPy/SiO2 catalysts from characterization studies. Data from characterization studies indicated that smaller and dispersed Ni2P particles were obtained by precipitation method as compared to that of impregnation method. NixPy/SiO2 with a molar ratio of P/Ni = 3.0 showed optimum catalytic performance with 3.28% of methane conversion, 1.93% of total product yield, and 60% of selectivity to hydrocarbons. The experimental results of the effects of reaction temperatures on the product distributions and activation energies indicated that the Ni2P phase successfully activated the C–H bond of methane and selectively converted to ethane. Ethane thermally converted to other higher hydrocarbons in the gas phase without the participation of the catalyst.

Catalyst-Free Ceramic–Carbonate Dual-Phase Membrane Reactors for High-Temperature Water Gas Shift: A Simulation Study

Water gas shift (WGS) reaction enhanced by a membrane reactor technology has emerged as a high-efficiency alternative to conventional fixed-bed reactors in integrated gasification combined cycle (I...

Membrane-based catalytic partial oxidation of ethanol coupled with steam reforming for solid oxide fuel cells

The present study was aimed at developing a new ethanol reforming process by integrating oxygen separation, partial oxidation and steam reforming in a membrane reactor. The reactor was constructed with the composite membrane of yttria-stabilized zirconia-La0.8Sr0.2Cr0.5Fe0.5O3-δ of effective area 5 cm2 and Ni–Ru/Al2O3 catalyst of loading 5 wt%. It attained ethanol conversion 99.9%, H2 selectivity 90.8% and CO selectivity 74.6% with ethanol feed rate 30 mL min−1and steam 54 mL min−1 at 800 °C. Running on the as-produced syngas fuel, a solid oxide fuel cell (SOFC) demonstrated a maximum power density of 999 mW cm−2 at 750 °C, which was just slightly lower than on pure hydrogen fuel. Compared with the conventional fixed bed reactor, the membrane reactor explored in the present study showed clear advantages in terms of heat management and syngas concentration, promising for us as ethanol pre-reformer in SOFC.

Ni-containing CeO2 rods for dry reforming of methane: Activity tests and a multiscale lattice Boltzmann model analysis in two model geometries

Experimental and theoretical modeling on low-temperature dry methane reforming over Ni-containing CeO2 rods was studied. The catalyst was characterized by means of N2 physisorption, in-situ XRD, TPR and H2 chemisorption techniques. The characterization studies revealed the distortion of CeO2 flourite structure due to the Ni incorporation. Lattice expansion (due to reduction) and contraction (due to oxidation) suggest the reversible redox nature of CeO2. Ni–O–Ce solid solution formation was evidenced by both XRD and TPR studies. H2 chemisorption study revealed that the catalyst reduction temperature plays a significant role in Ni dispersion. The catalyst showed similar activity trends in two model geometries: a between-two-plates microchannel fixed-bed reactor and a conventional fixed-bed reactor. The activity tests were conducted in the kinetic regime, where conversions of CH4 were not influenced with the gas flow rate. A lattice Boltzmann model for mixed gas flow was developed along with a boundary condition for catalytic sites. The lattice Boltzmann model was used in a multiscale simulation of the studied reaction systems and produced data that qualitatively matched the experiments.

Effect of Temperature on Plasma-Assisted Catalytic Cracking of Palm Oil into Biofuels

Plasma-assisted catalytic cracking is an attractive method for producing biofuels from vegetable oil. This paper studied the effect of reactor temperature on the performance of plasma-assisted catalytic cracking of palm oil into biofuels. The cracking process was conducted in a Dielectric Barrier Discharge (DBD)-type plasma reactor with the presence of spent RFCC catalyst. The reactor temperature was varied at 400, 450, and 500 ºC. The liquid fuel product was analyzed using a gas chromatography-mass spectrometry (GC-MS) to determine the compositions. Result showed that the presenceof plasma and catalytic role can enhance the reactor performance so that the selectivity of the short-chain hydrocarbon produced increases. The selectivity of gasoline, kerosene, and diesel range fuels over the plasma-catalytic reactor were 16.43%, 52.74% and 21.25%, respectively, while the selectivity of gasoline, kerosene and diesel range fuels over a conventional fixed bed reactor was 12.07%, 39.07%, and 45.11%, respectively. The increasing reactor temperature led to enhanced catalytic role of cracking reaction,particularly directing the reaction to the shorter hydrocarbon range. The reactor temperature dependence on the liquid product components distribution over the plasma-catalytic reactor was also studied. The aromatic and oxygenated compounds increased with the reactor temperature.©2020. CBIORE-IJRED. All rights reserved

Low Temperature Dehydration of Glycerol to Acrolein in Vapor Phase with Hydrogen as Dilution: From Catalyst Screening via TPSR to Real-Time Reaction in a Fixed-Bed

Temperature programmed surface reaction (TPSR) was developed as a method for rapid screening of catalysts. In this study, a series of acid catalysts was screened for the low-temperature dehydration of glycerol to acrolein via TPSR. Results suggested that most catalysts show activity of glycerol conversion to acrolein at a greatly different temperature range. HY, SiO2 supported H4SiW12O40 (STA/SiO2), SO42−/ZrO2, and SO42−/TiO2 were observed to be efficient for the conversion of glycerol into acrolein at 210 °C, which was significantly lower than that generally reported (250–340 °C). Moreover, high selectivity of acrolein was gained at 85% and 86% over SiW/SiO2 and SO42−/TiO2, respectively. A new style catalyst, ZnCl2/SiO2, was also found to be highly selective to acrolein and evaluated in a conventional fixed-bed reactor. Especially, stability tests showed that the catalyst life was up to 300 h with no clear deactivation on ZnCl2/SiO2 with hydrogen as dilution.

Hydrogen production with carbon dioxide capture by dual-phase ceramic-carbonate membrane reactor via steam reforming of methane

The existing process for hydrogen production from methane through steam-reforming requires multiple reactors and separators and is thus costly and energy-intensive. This paper reports a new concept of CO2-permselective membrane reactor for promoting hydrogen production via steam reforming of methane (SRM) with CO2 capture. The membrane reactor is made of a ceramic-carbonate dual-phase membrane with a two-layered asymmetric wall structure. Bismuth-yttrium-samarium oxide (Bi1.5Y0.3Sm0.2O3-δ, BYS) was added to the support layer to make it non-wettable by molten carbonate, leaving the samarium-doped ceria (Sm0.2Ce0.8O2-δ, SDC) layer to form a thin (~150 μm) CO2-permselective SDC/molten-carbonate dual-phase layer after molten carbonate infiltration. The output product composition from the membrane reactor confirms that in situ CO2 removal effectively promotes water-gas shift conversion in SRM and thus enhances hydrogen yield. At 900 °C with feed pressure at 1 atm, the membrane reactor achieves 90% hydrogen yield with 84% CO2 recovery, which poses significant improvement when compared with conventional fixed-bed reactor under similar conditions. Analysis of CO2 permeation activation energy suggests that surface reaction rate might have an effect on CO2 permeation flux for the thin SDC/molten-carbonate membranes. Under atmospheric conditions the CO2 permeation with reactive feed for SRM is lower than with non-reactive feed due to lower driving force under reactive conditions in the feed.

CFD modeling of a compact reactor for methanol synthesis: Maximizing productivity with increased thermal controllability

A kinetic model for methanol synthesis was validated for a conventional fixed-bed reactor at the mini-pilot scale by determining a heat transfer coefficient to fit the experimental data satisfactorily. To enhance the thermal controllability of the reaction system, a compact reactor, which utilizes heat transfer with both cooling media and cool feed gas, was introduced. The analysis of detailed profiles of mass, momentum, and heat was conducted by applying the developed kinetic model to the computational fluid dynamics modeling approach. While the accumulation of heat was observed in a conventional reactor because of its limited heat transfer capability, a compact reactor could efficiently remove the generated heat. The space velocity and feed temperature were manipulated to increase the production rate while unstable thermal behavior was prevented, and it was clearly shown that the proposed reactor could produce twice the methanol, with its peak temperature maintained below the conventional one. When the diameter of the catalytic bed in the compact reactor was increased, the reaction remained in the kinetic regime, resulting in high methanol productivity as well as maximum utilization of the bed.

Green synthesis of bio‐ethyl acetate over Egyptian natural red clay as a highly active, selective, and eco‐friendly catalyst

AbstractThe present work focused on the utilization of Egyptian red clay (ERC) without any treatment as a highly efficient, selective, and eco‐friendly catalyst for synthesis of bio‐ethyl acetate in the gas phase. The best conditions used in conventional fixed bed reactor were 130 cm3/min total flow rate of air with 1.6 and 2.1 vol% bio‐ethanol and bio‐acetic acid, respectively, 1 g clay catalyst calcined at 300 and 225°C reaction temperature. Under these conditions, the conversions to ester achieved were about 80 and 98% after 5 and 30 min, respectively, from the initial admission of the reactants into the reactor. The amount and type of surface acidity were identified by isopropanol reaction and chemisorption of basic probes. The results demonstrated that the majority of intermediate strength of BrØnsted acid sites are the key role for the dehydration reaction toward ester formation. The virgin and annealed clay solids were characterized using X‐ray fluorescence (XRF), thermogravimetry (TG) and differential thermal analysis (DTA), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and N2 sorption.

Application of a catalytic membrane reactor to the selective hydrogenation of 1-Butyne

A catalytic membrane reactor (CMR) was applied in order to enhance the selectivity in the hydrogenation of 1-butyne in the presence of 1-butene. The performance of the CMR was studied in batch-wise operation for the hydrocarbon liquid mixture, while hydrogen was continuously fed to keep a constant partial pressure. The reaction was carried out at 44 °C and partial pressures of hydrogen in the range of 1 to 5 bar. The CMR was prepared by impregnating a commercial alumina membrane disk with Pd. Experimental results were compared with those obtained in a conventional fixed bed reactor (FBR), using a commercial catalyst of egg-shell type in its original size, and in a microreactor (MR) with the same commercial catalyst milled to a size of around 40 μm. The CMR presents high activity and selectivity, comparable to the values of the milled commercial catalyst, but significantly higher than for the commercial catalyst in its original size. Kinetic parameters for the hydrogenation of 1-butyne were obtained from the regression of the experimental data. Also, a simulation of a continuous operation of both, CMR and FBR with the commercial catalyst, was carried out to show the advantage in selectivity of the CMR.

Characterisation and design of single pellet string reactors using numerical simulation

The concept of single pellet string reactors (SPSR), where particles are packed in tubes of only slightly larger diameter has been subject of recent studies which demonstrate a renewed interest in this reactor concept, including its use for catalyst testing. However, there remains the need for a thorough characterisation of the reactor performance. In this study, an attempt is made to systematically investigate the flow and conversion behaviour of SPSRs consisting of spherical, non-porous particles in cylindrical confining walls using computational fluid dynamics (CFD). A parameter study with variations on reactor geometry is conducted considering laminar flow and an isothermal, irreversible hypothetical first order reaction taking place at the catalytic particle surface. In addition to reaction simulation, the residence time behaviour is investigated based on numerical tracer experiments. The results showed that conversion close to plug flow can be achieved with SPSRs using favourable parameter settings. Conversion was found to be enhanced in reactors at larger scale, with smaller cylinder-to-particle diameter ratio and with a larger number of catalytic particles. The applicability of existing design criteria for conventional fixed-bed reactors is evaluated. Based on the observations a design criterion for SPSRs is proposed which allows prediction of the deviation to plug flow conversion based on reactor geometry, fluid properties and flow velocity.