Conventional Packed-bed Reactor Research Articles

Experimental and modeling studies on the low-temperature water-gas shift reaction in a dense Pd–Ag packed-bed membrane reactor

In this work, an experimental and modeling study is described, focusing on the performance of a Pd–Ag membrane reactor recently proposed and suitable for the production of ultra-pure hydrogen. A packed-bed membrane reactor (MR) with a “finger-like” membrane configuration has been used for carrying out the water-gas shift reaction (WGS) in the region of low temperature operation using a simulated reformate feed. The experiments were performed under a broad range of operating conditions of temperature (200–300 °C) and space velocity (1200–10,800 L N kg cat −1 h −1); the effect of feed pressure (1–2 bar) was also analyzed, as well as the operating mode at the permeate side: vacuum (30 mbar) or sweep gas (1.0 bar; nitrogen at 1 L N min −1). A one-dimensional, isothermal and steady-state model is proposed, which assumes axially dispersed plug flow pattern and pressure drop in the retentate side and plug flow with constant pressure in the permeate side. An innovative composed kinetic model was also used to describe the catalytic activity of the catalyst for the WGS reaction. In general, the simulation results showed a good agreement to the experimental data, in terms of carbon monoxide conversion and hydrogen recovery (and also outlet retentate composition) using only two fitting parameters related to the decline of H 2 permeability due to the presence of CO. Both simulation and experimental runs showed that the MR achieves high performances, for some operating conditions clearly above the maximum limit for conventional packed bed reactors. The performance reached is particularly relevant when hydrogen is recovered via sweep gas mode (a high sweep flow rate was employed), because a lower partial pressure could be reached than using vacuum pumping. In the first case, almost complete CO conversion and H 2 recovery could be reached.

Isobutane dehydrogenation in a DD3R zeolite membrane reactor

Dehydrogenation of isobutane has been studied in a DD3R zeolite membrane reactor (MR) at 712 and 762 K, using pure isobutane at 101 kPa as feed gas and N 2 as sweep gas. Clear advantage of using the small-pore zeolite DD3R is that it offers an absolute separation of H 2 from isobutane by a molecular sieving mechanism. Experiments in a conventional packed bed reactor served as benchmark. Cr 2O 3 on Al 2O 3 was used as catalyst. The DD3R membrane showed an excellent H 2/isobutane permselectivity (>500 @ 773 K) and a reasonable H 2 permeance (∼4.5 × 10 −8 mol m −2 s −1 Pa). At low residence times isobutene yields 50% above the equilibrium could be obtained. At 762 K and 0.13 kg feed kg cat −1 h −1, the isobutene yield in the membrane reactor (MR) is 0.41, where the equilibrium yield is ∼0.28. The increased performance is attributed to removal of H 2 from the reaction zone by the membrane, up to 85% at the lowest space velocity. The removal of H 2 mildly promotes coke formation, suppresses hydrogenolysis reactions and appears to slightly reduce the catalyst activity. The membrane permeation parameters and reaction rate constants have been estimated independently from membrane permeation and packed bed reactor (PBR) experiments, respectively. From these parameters the behaviour of the MR can be simulated well. Two important dimensionless parameters determine the MR performance primarily, the Damköhler ( Da) and membrane Péclet number ( Pe δ ). For a significant improvement of the MR performance as compared to a PBR Da ≥ 10 and Pe δ ≤ 0.1. DaPe δ should be ≈1 to optimally utilize both catalyst and membrane. In the current MR unit both the hydrogen removal capacity and catalyst activity stand in the way of successful application. Using a more active catalyst and a more favourable area to volume ratio could greatly improve the MR performance. Operation at a higher feed pressure could be a possible solution. Since membranes with higher fluxes are already available, the limited catalyst activity and stability under relative low temperature and H 2 lean conditions are the important limiting factors regarding application of MRs in dehydrogenation reactions.

Tube fitted bulk monolithic catalyst as novel structured reactor for gas–solid reactions

A novel fixed-bed reactor for gas–solid catalytic reactor using bulk monolithic catalyst (BMC), the so-called tube fitted bulk monolithic catalyst (TFBMC), instead of conventional packed bed reactor is presented. From the two types of monolithic catalyst, i.e. washcoated and the one made from bulk catalyst, the first one has been widely discussed in the literature. However, there is scarce report regarding the latter. In this research we have focused on introducing, preparation and application of TFBMC. Here, the two types of monolithic catalysts are compared. The advantages and disadvantages of the proposed concept as compared with packed bed reactor are discussed. Several parameters such as material, structure and preparation method of the catalysts are investigated. As a case study the mold ability and the performance of TFBMC in Fischer Tropsch synthesis (FTS) are explained. The results indicate that the TFBMC has superior advantages over the conventional fixed-bed reactors. Furthermore, the concept employed in fabrication of TFBMC may be easily applied with minimum modification to the conventional fixed-bed reactors which results in more productivity and better performance.

Reaction of primary and secondary products in a membrane reactor: Studies of ethanol steam reforming with a silica–alumina composite membrane

The steam reforming of ethanol over Na–Co/ZnO catalysts was investigated in a conventional packed-bed reactor (PBR) and in a membrane reactor (MR) fitted with silica–alumina composite membranes. Promotion with a moderate amount of Na (0.2–1.0 wt%) produced catalysts with stable ethanol conversion and product selectivity. At 523 K, the main products were H 2 (51%) and CH 3CHO (42%) with minor amounts of CH 4 (0.7%) while above 573 K the main products were H 2 (70%) and CO 2 (15%) with a small amount of CH 4 (2.4%). Higher cobalt loading, higher W:E ratio, higher reaction temperature and lower space velocity enhanced the conversion of ethanol to H 2 and CO 2 while reducing the formation of undesirable acetaldehyde. Contact time studies indicated that acetaldehyde was a primary product of ethanol reforming, while CO 2 and CH 4 were secondary products. The composite membranes were prepared by a chemical vapor deposition (CVD) method and had moderate H 2 permeances ((5.2–6.8) × 10 −8 mol m −2 s −1 Pa −1 at 623 K). The MR produced positive yield enhancements of the secondary products, including hydrogen, but yield reductions for the primary product, acetaldehyde, and this is explained from the effect of the membrane separation on the reaction network. Two membranes with similar permeances but different H 2 selectivity ratios (H 2/CH 4 = 60 and 350) were compared and it was found that the membrane with a higher H 2/CH 4 selectivity ratio gave a higher yield enhancement. A survey of membrane reactor studies indicated that the conversion enhancement in reforming reactions could be described by a parameter denoted the operability level coefficient (OLC) which is related to 1/DaPe.

Enhancing Reaction Selectivity by Intentional Control of Concentration Profile in Catalytic Microreactor

This paper reports the results of a computational fluid dynamics (CFD) simulation for a sequential heterogeneous catalytic reaction by comparing the reaction selectivity in a catalytic microreactor with that in a conventional catalytic packed-bed reactor. The comparative simulation revealed that the catalytic microreactor has an advantage over the conventional reactor in the diffusion control regime, and that the control of concentration distribution of reactants by molecular diffusion in the microspace can enhance the selectivity of the desired product. The concentration distribution was intentionally controlled by the shape of the microreactor. The yield of the desired product in the microreactor was 1.16 times that in the packed-bed reactor. CFD simulation of methanol decomposition was also performed by fitting the parameters with the experimental results. The results of the CFD simulation verified the advantage of the microreactor.

N-Dodecane reforming over monolith-based Ni catalysts: SEM study of axial carbon distribution profile

The extent and nature of carbon deposition that occurs during catalytic reforming reactions of hydrocarbons depends strongly on the reaction conditions and the surface properties of the catalyst. In conventional packed bed reactors it is difficult to track the spatial distribution of carbon and link it to the location of individual catalyst particles. The present work uses monolith-based nickel catalysts to investigate the axial carbon gradient post n-dodecane reforming. The carbon, which was deposited during autothermal reforming (ATR), partial oxidation (POX), and steam reforming (SR) over Ni/cerium-zirconium oxide (CZO)/monolith and Ni/monolith catalysts, was characterized by a combination of temperature-programmed oxidation (TPO), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The amount, location, and type of carbon deposited strongly depended on the type of reforming reaction. The majority of carbon deposition was concentrated inside cordierite pores of the monolith. In general, the catalysts showed the expected trend of increased filamentous carbon deposition down the length of the monolith, reflecting the axial variation in temperature and oxygen concentration, except for POX over Ni/monolith catalyst where massive coating carbon deposition occurred in the upstream section of the monolith.

Modeling and performance assessment of Pd- and Pd/Au-based catalytic membrane reactors for hydrogen production

A mathematical steady-state modeling framework for the isothermal operation of a membrane reactor for methane steam reforming is developed, and a comparative performance assessment of the catalytic membrane reactor (CMR) versus a conventional packed bed reactor (PBR) is accordingly conducted. A detailed literature benchmarking suggests that the models developed in the present study predict total methane conversion levels within 99% of the experimental values reported in the literature. The proposed Pd- and Pd/Au-based CMR model is utilized for the aforementioned performance analysis under a broad range of reactor operating conditions such as temperature (350–750 °C), pressure (2–30 bars), steam to methane ratio (1–15), membrane thickness (1–50 µm), and permeate-side sweep ratio (1–100). In all simulation runs conducted, the superior performance of both the Pd- and Pd/Au-based CMR over the PBR was amply demonstrated. Furthermore, within the proposed CMR modeling framework, an index-based analysis is conducted that concretely quantifies progress towards the attainment of key process intensification objectives. In particular, by appropriately defining the Δ-index, which explicitly captures potential performance and process intensification benefits associated with attainable total CH4 conversion levels under different reactor operating conditions, it is shown that the optimum CMR performance is achieved at high pressure and low temperature operating conditions, which was particularly suitable for the attainment of key process intensification objectives as well as optimum performance target levels.

Epoxidation of propylene with H 2 and O 2 in the explosive regime in a packed-bed catalytic membrane reactor

The vapor-phase epoxidation of propylene with H 2 and O 2 over a highly dispersed Au/TS-1 catalyst was carried out in a packed-bed catalytic membrane reactor. The membrane reactor allowed the use of high concentrations of H 2 and O 2 (40% each) that were well within the explosive regime, and the production rate of propylene oxide was improved by 100–200% compared with that from a conventional packed-bed reactor. At 180 °C, the C 3H 6 conversion was 10% and the PO selectivity was 80%, corresponding to a space–time yield of 150 g PO kg cat −1 h −1 , whereas at 212 °C, the yield increased to 200 g PO kg cat −1 h −1 . The kinetic dependency, r PO = k (H 2) 0.53 (O 2) 0.26 (C 3H 6) 0.18, obtained free from mass transport and heat transfer limitations at these high concentrations was in good agreement with that reported at low concentrations.

Micromachined Methanol Reformer for Portable PEM Fuel Cells

Fabrication procedures for a micromethanol reformer including catalyst preparation, coating, and patterning on a wafer are described. Cu-based catalyst was prepared by coprecipitation method. The effects of precipitation conditions on the catalytic activity and adhesion of coated catalyst on the substrate were tested to find the optimum precipitation condition. For coating purposes, the prepared catalyst was ground into powder and mixed with binder in the solvent. Simultaneous precipitation of catalyst and binder on the wafer produced catalyst layer that is uniform and rigidly found to the wafer surface. The amount of coated catalyst on the wafer was 5–8mg∕cm2 with a thickness of 30μm. By repetition of coating procedure, catalyst mass up to 15mg∕cm2 was obtained with increased reactivity. Patterned catalyst layer was obtained by novel lift-off process of polyvinyl alcohol sacrificial layer. A micromethanol reformer was fabricated using a typical lithography procedure including catalyst coating and patterning process. Typical methanol conversion was higher than the conventional packed bed reactor.

Assessment and optimization of the mass-transfer limitation in a metal foam methanol microreformer

The performances of a methanol steam microreformer, constructed of CuZn metal foam coated by CuZnAlZr catalyst, were compared with those of a conventional packed-bed reactor. By variation of temperature, catalyst thickness and superficial velocity, the external and internal mass transfer in the microreformer was investigated. The external mass transfer can be ignored due to the high mass transfer coefficient of the metal foam. The internal diffusion resistance of the catalyst depends on the calcination temperature and catalyst/Al2O3 binder ratio of catalyst layer over metal foam, due to the development of catalyst pores. With optimum preparation conditions, the critical thickness to eliminate internal mass transfer limitation is about 8 μm. The improved external and internal mass transfer resulted in a methanol conversion increase of about 10% in microreformer compared with packed-bed.

Feasibility Study of the Oxidative Dehydrogenation of Ethane in an Electrochemical Packed-Bed Membrane Reactor

The feasibility of the oxidative dehydrogenation of ethane to ethylene with alumina-supported vanadium oxide catalyst (VOx/γ-Al2O3) in an electrochemical packed-bed membrane reactor was investigated at temperatures between 500 and 620 °C with molar ratios of oxygen to ethane of 0.06−3.10. An oxygen-ion-conducting yttria-stabilized zirconia (YSZ) membrane was employed in a reactor of Au|YSZ|Pt, and the oxygen flux transferred across the membrane was controlled over the faradic coupling of oxygen-ion conduction and the external current between the electrodes. The oxidative dehydrogenation of ethane with electrochemically supplied oxygen in the membrane reactor was compared to that obtained with gaseous dioxygen in a conventional packed-bed reactor. The selectivity to ethylene was found to decrease as a function of supplied oxygen in both investigated operating modes. For all investigated oxygen/ethane molar ratios, the selectivity ratio, SCO2/SCO, was found to be clearly higher in the electrochemical than in the packed-bed reactor mode. The electrochemical oxygen supply significantly promoted CO2 formation, whereas the ethane conversion and ethylene selectivity were almost equal in the two investigated reactors. The experimental results indicate that, in the electrochemical operation, additional oxygen species exist in the system and are especially reactive in the total oxidation reactions.

Decomposition of volatile organic compounds by a novel electrode system integrating ceramic filter and SPCP method

We developed a new efficient apparatus for gas treatment in which a ceramic filter and SPCP (surface corona discharge induced plasma chemical process) were integrated. In this study, the feasibility of the reactor to decompose volatile organic compounds (VOCs) and performance were evaluated. The efficiency was examined against various conditions of initial concentration of VOCs, as trichloroethylene (TCE), toluene and benzene, and by using variable flow rates of carrier gases (air, nitrogen, and mixture of nitrogen and oxygen or water vapor). TCE was decomposed effectively within the reactor system, especially when the carrier gas contains oxygen or water as an oxygen source, whilst the decomposition efficiency was low with the nitrogen carrier. With a sufficient oxygen source, no organic by-products were detected in the treated gas, and TCE was oxidized to inorganic substances. Toluene and benzene were efficiently decomposed as well. For performance evaluation of such non-thermal plasma reactors for VOC treatment, we proposed a new parameter which is derived with substance based energy density, mSED (J/mol). The new parameter has merit to express the performance with a single parameter for a range of discharge power, flow rates, and initial concentrations of the gas to be treated. With the parameter proposed, the evaluation resulted in a new reactor in this study that has as high a performance as a conventional packed-bed reactor, and their performances are higher than pulse corona (PC), and dielectric barrier discharge reactors.

Hydrogen generation in a Pd membrane fuel processor: Productivity effects during methanol steam reforming

Performance analyses are carried out for the palladium membrane fuel processor for catalytic generation of high purity hydrogen. The reactor model includes detailed particle-scale multi-component diffusion, multiple reversible reactions, flow, and membrane transport. Using methanol steam reforming on Cu / ZnO / Al 2 O 3 catalyst as the test reaction, a systematic examination of the effects of operating and reactor design parameters on key performance metrics is presented. Single particle simulations reveal a complex interplay between nonisobaric transport and the reversible reactions (methanol reforming and decomposition, and water–gas shift), which impact overall reactor performance. An analysis of characteristic times helps to identify four different productivity controlling regimes: (i) permeation control, encountered with thick membranes and/or insufficient membrane area; (ii) catalyst pore diffusion control encountered with diffusion of reacting species in larger particles; (iii) reaction control, encountered when intrinsic catalytic rates are too low because of inadequate activity or catalyst loading; and (iv) feed control, encountered when the limiting reactant feed rate is inadequate. The simulations reveal that a maximum in the hydrogen productivity occurs at an intermediate space velocity, while the hydrogen utilization is a decreasing function of space velocity, implying a trade-off between productivity and hydrogen utilization. The locus of productivity maxima itself exhibits a maximum at an intermediate membrane surface to volume ratio, the specific value of which is dependent on the particle size, membrane thickness and reaction conditions. At moderate temperature and total pressure ( 260 ∘ C , 10 bar), particles smaller than 2 mm diameter, Pd membranes with thickness less than 10 μ m , and membrane surface to volume ratio exceeding 500 m 2 / m 3 are needed to achieve viable productivity ( > 50 mol H 2 / m 3 s ) . A comparison between the packed-bed membrane reactor and conventional packed-bed reactor indicates a modest improvement in the conversion and productivity due to in situ hydrogen removal.

Hydrodenitrification with PdCu Catalysts: Catalyst Optimization by Experimental and Quantum Chemical Approaches

AbstractA continuous process for nitrate and nitrite abatement from drinking water by catalytic hydrogenation has been developed in our lab. We describe the experimental process development procedure, and support it with semiempirical quantum chemical methods. Comparisons of activated carbon (ACC) and silica glass fiber (GFC) cloths as supports for mono‐ and bimetallic Pd‐Cu catalysts show the former to be 45‐fold and 15‐fold more active for nitrite and nitrate hydrogenation, respectively, than the latter. Catalysts prepared by selective deposition of Cu on Pd/ACC led to better activity for nitrate hydrogenation than catalysts prepared by co‐impregnation or ion exchange methods. The optimal Cu:Pd atomic ratio was found to be 1:2. The computational results show the following: (i) The dispersion of Pd catalysts supported on ACC is much higher than that on GFC due to the larger surface area and higher density of adsorption sites, and that accounts for the higher activity of PdCu/ACC; (ii) Nanosized Pd particles supported on ACC have a semispherical shape and possess preferentially close‐packed triangular surfaces, while Pd/GFC particles are extended in the direction parallel to the support surface and show both fcc (100) and (111) planes; (iii) The interaction of Cu atoms with both supports is stronger than that of Pd; adsorbed Cu atoms show a greater ability to form monometallic than bimetallic bonds and that should result in poor mixing of the metal upon co‐impregnation, as was observed experimentally; (iv) Cu atoms in bimetallic PdCu particles admit a significant positive charge; the experimentally measured solubility of metal atoms correlates with their calculated charges.The best catalyst (2 wt%Pd‐0.6 wt%Cu/ACC) was employed in a novel continuous flow reactor for nitrate hydrogenation in distilled and tap water. The advantages of the reactor investigated over a conventional packed bed reactor are discussed, suggesting a potential for further process intensification.

A plate-type reactor coated with zirconia-sol and catalyst mixture for methanol steam-reforming

A plate-type reactor with 10 channels is designed for methanol steam-reforming and its performance is investigated in the temperature range 210–290 °C. A catalyst coated with zirconia-sol solution in the channels of the reactor exhibits a good adherence with the substrate that is maintained even after reaction including fast feed flow rates at high temperature. Five plate-type reactors are stacked in order to test their performance for methanol steam-reforming. At 270 °C, hydrogen at 3.1 l h −1 is obtained at a feed flow rate of 2.0 g h −1, which corresponds to results for a conventional packed-bed reactor under various reaction conditions.

γ-MnO2 nano-sieve membrane: preparation, characterization and reaction studies

γ-MnO2 nano-sieve membrane was synthesized using γ-MnO2 nanometer powders by suspending particles sintering method. The results of BET, AFM, and SEM indicate that γ-MnO2 nano-sieve membrane with a thickness of about 2μm is porous (pore size 4nm), and has a smooth surface. The results of XRD and TPR exhibit that the phase transformation which can be suppressed at La/Mn = 0.15, and the activity of oxygen center of γ-MnO2 nano-sieve membrane (La/Mn = 0.15) is slightly lower than that of γ-MnO2 nanometer powders. γ-MnO2 nano-sieve membrane shows a higher separation factor of H2/Ar in the range of 50–300°C. In addition, the γ-MnO2 nano-sieve membrane was applied to the membrane reactor for cyclohexane oxidative dehydrogenation, and the effect of temperature on cyclohexane conversion was investigated. The result shows that cyclohexane conversion in the γ-MnO2 nano-sieve membrane reactor is higher than that in the conventional packed bed reactor.

Combustion of CH 4 over a PdO/ZrO 2 catalyst: an example of kinetic study under severe conditions

A kinetic study on CH 4 combustion over a very active PdO/ZrO 2 catalyst with high Pd loading (10% w/w of Pd) is presented as an example of a demanding problem which requires both the development of appropriate experimental tools and a theoretical insight on surface chemistry. The use of an annular catalytic reactor as a tool to collect kinetic data under unusually severe conditions (high temperature and CH 4 concentration) is described in comparison with the use of a conventional packed bed reactor. In particular, problems related to the biasing effects of mass, heat and momentum transfer are addressed. Kinetic data addressing the effects of CH 4, O 2, H 2O and CO 2 concentration in a temperature range from 400 to 550 °C are analysed by means of a purely empirical power law model and of a formal kinetic model based on literature indication assuming methane dissociative adsorption as the rate controlling step.

Ministructured catalyst bed for gas‐liquid‐solid multiphase catalytic reaction

AbstractA ministructured reactor concept improves the performance of multiphase gas‐liquid‐solid reactions over conventional packed‐bed and trickle‐bed reactors. In the mini‐structured reactor, the catalyst bed is structured at the particle level by dividing the bed into a number of identical, parallel flow channels with the channel walls being catalyzed. The hydraulic diameter of each channel opening is from 0.2 to 2 mm, comparable to the conventional particle size. The mini‐structured reactor can be assembled using monolith catalyst modules that have been a proven material technology for gas‐phase reactions. Two types of gas‐liquid‐solid reactions, olefin hydrogenation and toluene saturation, are used to test the fundamental feasibility of the mini‐structured reactor under steady‐state reaction conditions in a cocurrent down flow mode. The new reactor shows an order of magnitude increase in the activity compared to a trickle‐bed operation for reaction conditions of practical interest. This degree of activity improvement is larger than estimates based on conventional analyses of catalyst geometric surface area and/or characteristic pore diffusion lengths. Individual catalyst particles are significantly underutilized in a trickle‐bed reactor. More ideal contacting of gas, liquid and catalyst, as well as the enhancement of overall mass‐transfer processes in the mini‐structured reactor, makes it possible to dramatically improve the gas/liquid multiphase reaction performance over solid catalysts.

Towards ideal NO/sub x/ control technology using a plasma-chemical hybrid process

The plasma-chemical hybrid process developed was extremely effective and economical in comparison with the conventional selective catalytic reduction (SCR) system and other technologies for NO/sub x/ removal from flue gas emissions. A series of experiments was performed to quantify all the reaction by-products such as N/sub 2/O, CO, HNO/sub 2/, HNO/sub 3/, and NO/sub 3//sup -/ and to evaluate NO/sub x/ removal efficiency. The optimum plasma reactor and its operating characteristics were investigated with regard to reaction by-products and NO/sub x/ removal efficiency using the ordinary ferroelectric packed-bed plasma reactor and the barrier-type packed-bed plasma reactor. The oxidation from NO to NO/sub 2/ without decreasing NO/sub x/ concentration (i.e., minimum reaction by-products) and with least power consumption is the key for the optimum reactor operating condition. The produced NO/sub 2/ was totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ with Na/sub 2/SO/sub 3/ scrubbing. The barrier-type packed-bed plasma reactor having 1.5 mm diameter electrode and 3 mm diameter BaTiO/sub 3/ pellets showed the superior NO oxidation without producing the by-products over the conventional packed-bed reactor. The barrier-type packed-bed plasma reactor followed by the chemical reactor showed extremely low operating costs (less than 1/6 of the SCR process) and achieved nearly 100% NO/sub x/ removal with less than 6 ppm of N/sub 2/O and 5 ppm of CO.

ChemInform Abstract: Millisecond Chemical Reactions and Reactors

Short contact time chemical reactors have many features which are very different from conventional packed bed reactors in that temperatures are determined by inlet parameters only, performance is nearly unchanged over wide variations in flow rate, and highly nonequilibrium products can be obtained at high conversions. Chemical reactions occur in regions of large gradients in composition and temperature, so the kinetics of the processes cannot be simply extracted from experiments. We illustrate these systems with recent examples of oxidative dehydrogenation of ethane at 85% ethylene selectivity and cyclohexane partial oxidation to oxygenates and olefins at 80% selectivity. A major feature of both reaction systems is the probable existence of two zones in the monolith where oxidation reactions occur close to the entrance and successive reactions such as homogeneous pyrolysis occur after all O2 is consumed and the surface is passivated with carbon. For the single gauze reactor only homogeneous oxidation occurs after the gauze where the temperature decreases strongly and quenches further decomposition of olefins and oxygenates. Considerations of scaleup of these reactors for large-scale chemicals production are discussed.