Contact Time Catalytic Partial Oxidation Research Articles

Techno economic analysis of a micro Gas-to-Liquid unit for associated natural gas conversion

Flared and vented natural gas in remote regions of the world contribute ¿1% of the total CO2 emissions. High investment costs to build facilities to treat this gas and labor costs to operate the infrastructure are deterrents to addressing this environmental burden. Here we report a techno-economic analysis of a commercial mobile manufacturing plant that processes 2400 m3 d-1 of methane via a tandem short contact time catalytic partial oxidation (CPOX) and a single-pass Fischer–Tropsch fluidized bed to produce 7 bbl d-1. Starting from methane and air, a thermodynamic analysis identified the optimized operating conditions considering both carbon yield, CO/H2 ratio and adiabatic conditions. We studied the flammability limits of the mixture at operating pressures and temperatures. The economic analysis itemizes costs for all equipment rather than applying scale-up power law or factors. The greatest contributors to direct costs are the compressors and the CPOX reactor. Operating CPOX at 2.0 MPa reduces reactor volumes but to achieve 90% conversion and selectivity requires operating this unit above 900 °C. Avoiding syngas compression and upstream syngas conditioning reduces capital costs. The capital cost (CAPEX) reaches 570 000 USD when the whole process operates at 2.0 MPa. Considering numbering-up, the price of the 100th unit approaches 360 000 USD thus the MRU increases profitability. We demonstrate how thermodynamics constrains methane conversion and syngas selectivity. A large part of achieving low CAPEX is operating a single pass process, building multiple units, and replacing the methane to heat the treater at the oil tank battery with the incondensable gas leaving the three phases separator downstream the Fischer–Tropsch reactor.

Short Contact Time Catalytic Partial Oxidation of Methane over Rhodium Supported on Ceria Based 3-D Printed Supports

Three different ceria containing catalyst supports and an alumina (control) support have been deposited with rhodium and used in the short contact time catalytic partial oxidation of methane. The g...

Hybrid Catalytic Combustion of Methane/Hydrogen Mixtures

Hybrid catalytic combustion technology, which is a staged process comprising a preliminary catalytic partial oxidation (CPO) step followed by a homogeneous flame combustion with interstage heat removal, was tested for the first time with mixtures of methane and hydrogen. Short contact time CPO experiments were run to elucidate the effect of the progressive substitution of methane with H2 in the fuel feed to the structured catalytic reactor, which was operated under self-sustained conditions at high temperature. Furthermore, a prototype radiant hybrid burner was realized and safely operated at atmospheric pressure with up to 80% vol. of H2 in the fuel and a primary equivalence ratio in the range 2.4–4.0. Outstanding NOx emission levels were attained with pure methane feed, which were also confirmed with H2-rich fuels, due to the effective reduction of both thermal and prompt NOx formation.

Short contact time catalytic partial oxidation of biogas – A comprehensive study on CO2 and N2 dilution

The short contact time catalytic partial oxidation of methane diluted with nitrogen and/or carbon dioxide to act as a surrogate for biogas conversion was carried out. Experiments were carried out under varying operating conditions to determine the possible use of the products in pyrolysis.Carbon dioxide has a larger effect on the product selectivities and back face temperature of the catalyst compared to nitrogen for equal dilutions. Carbon dioxide is consumed in the reactor whereas nitrogen is not. Since carbon dioxide likely takes part in endothermic reactions, the temperature of the catalyst is lower as is the conversion of methane and selectivity to carbon monoxide and hydrogen.The product stream is at an appropriate composition and temperature for subsequent use in a pyrolysis reactor. The presence of hydrogen and carbon monoxide will result in the removal of oxygen from bio-oils that are produced in the pyrolysis reactor.

Optimal Design of A CPO-Reformer of Light Hydrocarbons with Honeycomb Catalyst: Effect of Frontal Heat Dispersions on the Temperature Profiles

This paper extends a previous investigation on the thermal behavior of CH4-CPO reformers with honeycomb catalysts. Modeling and experimental studies on the short contact time catalytic partial oxidation (CPO) of CH4 to syngas from our and from other groups have shown that Rh-catalysts rapidly deactivate at the very high temperatures, close to 1000 °C, that establish in the inlet zone of the reactor. We have previously shown that a significant reduction of the surface hot-spot temperature can be obtained by properly designing the catalyst: beneficial effects are observed at increasing opening of the honeycomb channels, which decreases the rate of O2 inter-phase mass transfer, and at increasing catalyst activity, which promotes the rate of the endothermic reactions. In this work, we explore the effect of the reactor configuration, namely the effect of heat dispersion from the glowing front face of the monolith. Three reactor configurations were compared in CH4-CPO experiments: (i) a configuration with perfect continuity between the front heat shield (FHS) and the catalytic module, which behaved close to an ideal adiabatic reactor, (ii) a configuration where the FHS was separated from the catalytic monolith and (iii) a configuration where the FHS was at large distance from the catalytic module. State of the art experimental tools, including the spatially resolved measurement of temperature and concentration profiles were used to characterize the thermal behavior of the various configurations. Detailed kinetic modeling supported the analysis of data. The results showed that, at the expense of a small loss of thermal efficiency, a very moderate loss of performance in terms of conversion and selectivity, but, remarkably, an important reduction of the surface inlet temperatures were achieved. Preliminary experiments with propane/air mixtures suggest that the adoption of a moderately dispersive reactor can represent a promising solution for the stable operation of catalytic units treating heavier fuels than methane.

Optimal design of a CH 4 CPO-reformer with honeycomb catalyst: Combined effect of catalyst load and channel size on the surface temperature profile

Previous experimental and modeling work on the short contact time catalytic partial oxidation (CPO) of CH 4 to syngas [1] pointed out that a key issue (and a weakness) of the process is represented by the hot spot that establishes on the catalyst surface at the reactor inlet. In this work, we show that the interplay between surface chemistry and mass transfer can be exploited to minimize the extent of surface hot-spots. By increasing the channel diameter and the catalyst load of a Rh-coated honeycomb monolith, we obtained a reduction of the rate of O 2 conversion (mass-transfer limited) and a selective enhancement of the rate of CH 4 conversion through endothermic reactions. The resulting temperature profile was significantly flatter. Detailed model analysis and spatially resolved temperature and concentration profiles within the honeycomb channels demonstrate the concept.

Effect of Sulfur Poisoning in High Pressure Catalytic Partial Oxidation of Methane over Rh−Ce/Al2O3 Catalyst

Short contact time catalytic partial oxidation (CPO) of methane has received increasing attention in industrial applications. Understanding of the catalytic system under high pressure and in the presence of sulfur represents a key challenge of this technology. This paper discusses CPO performance using a Rh−Ce catalyst supported on washcoat alumina foam under industrial relevant operating conditions (pressure up to 160 psig and different sulfur levels up to 16 ppm in methane). A long-term experimental run cycling between sulfur-free and sulfur injection conditions was conducted to examine the influence of sulfur on the catalyst. Sulfur effects were also evaluated under different sulfur levels and with different feed compositions. A dual zone reaction model was used to explain the effects of pressure, sulfur level, and the O/C ratio on CPO catalytic performance. Engineering challenges and requirements of the CPO process for industrial applications were discussed on the basis of recent advances in the understanding of CPO chemistry.

Hydrocarbons valorisation to cleaner fuels: H 2-rich gas production via fuel processors

This paper presents a panoramic overview of the experimental work carried out at Politecnico di Torino on the development of structured catalytic reactors for the production of H 2-rich streams from hydrocarbons, to be fed to PEM-FCs: short contact time catalytic partial oxidation (SCT-CPO) reactor for syngas production, micro-channelled reactors for syngas CO clean-up, water gas shift (WGS) and preferential oxidation (PROX). Concerning the reactor for methane SCT-CPO, 10% Ni deposited on irregular γ-Al 2O 3 particles presented the best performance (CH 4 conversion > 90%; H 2 selectivity > 95%) compared to 0.5% Rh deposited over γ-Al 2O 3 spheres. As regards the HT-WGS reaction, the best performance was obtained with the catalyst 1% Pt/(CeO 2 + TiO 2): it reached the thermodynamic equilibrium (inlet CO: 10% b.v.; WHSV = 40 Nl h −1 g cat −1) in the temperature range 450–525 °C, allowing the abatement of almost 60% of the CO present in the fed gas stream. Finally, the best performance towards CO-PROX reaction was obtained with the catalyst 1% Rh/(Al 2O 3 + 3A zeolite): it reached the complete CO conversion (inlet CO: 0.5% b.v.; WHSV = 40 Nl h −1 g cat −1; λ = 3) in the temperature range 130–160 °C, thus assuring an easy controllability of the system.

Influence of steam on the flammability limits of premixed natural gas/oxygen/steam mixtures

Synthesis gas (Syngas) is an intermediate in a variety of industrial processes. Its production is energy and capital intensive and any improvement of existing technologies allowing simpler and economic production is of great interest. Recently, a new method known as short contact time-catalytic partial oxidation (SCT-CPO) has been developed into a commercial technology [1–4]. SCT-CPO is an entirely heterogeneous catalytic process converting premixed flammable feedstocks inside a very small reactor. In order to ensure safety and a high selectivity towards CO and H 2 it has been important to determine and understand flammability properties of the gaseous reactant mixtures. Here we report on the results obtained within a windowed tube reactor equipped with multiple photodetectors and pressure transducers that has allowed the study of ignition, flame propagation, and explosion characteristics of gas mixtures similar to those used as reactants in the SCT-CPO reactor. The tests were conducted at various pressures with different amounts of steam and two different compositions of natural gas (NG). A flammability boundary for each mixture, based on normalized pressure and mole fraction of steam, was determined. The results conclude that these mixtures’ flammability could be suppressed in two very different ways. Depending on the adiabatic flame temperature of the mixture, suppression could be caused by steam's chemical influence increasing chain-termination or by a large amount of steam decreasing the reaction zone temperature.

Effect of the Catalyst Load on Syngas Production in Short Contact Time Catalytic Partial Oxidation Reactors

Short contact time catalytic partial oxidation (SCT-CPO) of natural gas is a promising technology for synga? production, representing an appealing alternative to existing processes. This process is likely to become more important in the future due to its advantages in thermodynamics, mildly exothermic overall reaction, and H 2 /CO ratio of 2, ideal for downstream processes. Rh catalysts are preferred among those based on noble metals because they avoid coke deposition. However, Rh is very expensive. Thus, the design of nanocomposite catalysts with the minimum Rh load for a feasible industrial process is the aim of the present work: 0.25, 0.5 and 1% Rh load were considered. The catalytic reactor is made of a fixed bed of Rh deposited on both Al 2 O spheres in an egg-shell configuration and Al 2 O 3 irregular particles in an egg-yolk configuration. The weight hourly space velocity (WHSV) was varied from 130 to 460 N L h -1 g cat -1 . The 0.5% Rh in the egg-yoll configuration allowed the highest CH 4 conversion (>90%) and H 2 selectivity (>98%) values at any tested WHSV.

Rh-based catalysts for syngas production via SCT-CPO reactors

Short contact time catalytic partial oxidation (SCT-CPO) of natural gas is a promising technology for syngas production, representing an appealing alternative to existing processes. This process is likely to become more important in the future due to its advantages in thermodynamics, mildly exothermic overall reaction, H 2/CO ratio of 2, ideal for downstream processes. The present work refers to an experimental study of syngas production from CH 4 and O 2 via a SCT-CPO reactor made of a fixed bed of Rh/Al 2O 3 spheres, with Rh deposited in egg-shell or egg-yolk configuration. In the WHSV range from 120 to 470 Nl h −1 g cat −1, five different fixed bed structures were investigated. The best performances in term of CH 4 conversion and H 2 selectivity, together with no coke formation, were obtained with an physical mixture of egg-shell and egg-yolk catalysts at WHSV values of 150–300 Nl h −1 g cat −1.

Fuel processor based on syngas production via short contact time catalytic partial oxidation reactors

Short contact time catalytic partial oxidation (SCT-CPO) of natural gas is a promising technology for syngas production, representing an appealing alternative to existing processes. The high conversion and selectivity observed since the earlier works in this field can make this process attractive. Moreover, the SCT-CPO reactors can be autothermally operated and the possibility to use air as oxidant appears a feasible route to reduce syngas production costs: these two issues make possible the use of a SCT-CPO reactor as the reformer of a fuel processor for H2 production for fuel cells.The present work refers to an experimental study of syngas production from CH4 and O2 via a SCT-CPO reactor made of a fixed bed of Rh/α-Al2O3 spheres. The main obtained results are: (i) an increase in GHSV produces an enhancement of transport rates and this in turn determines an improvement in CH4 conversion, despite the reduction in residence time; (ii) the catalyst pellets get hotter than the gas phase thus favouring the H2 and CO production; syngas formation is in fact both thermodynamically and kinetically promoted at high temperatures; (iii) a similar improvement of conversion was obtained with a reduction of the catalyst particle size, thanks once again to an increase in the heat transport and a higher geometrical surface area of the catalyst itself. By a slight increase of the O2 fed to the reactor, H2 and CO yields can be maximised and a complete CH4 conversion achieved.

Issues in H 2 and synthesis gas technologies for refinery, GTL and small and distributed industrial needs

H 2 and synthesis gas have been extensively utilised for more that 70 years in chemical and refinery industries. Their uses are becoming today more complex being influenced by strategic, political, economic and sustainability considerations. Issues that would benefit from innovations in the synthesis gas production concern the: (a) clean fuel production and the heavy residues utilisation, (b) the gas to liquid initiatives and (c) the desired but not yet accomplished electric energy production with fuel cells. The technological needs will be examined and their accomplishment will be discussed considering the utilisation of the short contact time–catalytic partial oxidation technologies.

Crossing the breakthrough line of ethylene production by short contact time catalytic partial oxidation

A novel catalyst (Pt-LaMnO 3) for the oxidative dehydrogenation of ethane to ethylene in short contact time reactors was developed by Istituto di Ricerche sulla Combustione (CNR) in cooperation with Snamprogetti, with a multi-layered structure consisting of a thin layer of Pt deposited onto a layer of LaMnO 3 perovskite supported over monolithic carriers. Such structured catalyst was tested in a head-to-head comparison with state-of-the-art Pt and Pt-Sn systems, under autothermal process conditions, showing enhanced performances both in terms of high temperature stability and yields to ethylene. The development of a durable, high-performance catalyst undertaken in this work may be beneficial to making catalytic ethane ODH more economically viable and represents a further step towards its pre-commercial implementation.

Hydrogen production from propane in Rh-impregnated metallic microchannel reactors and alumina foams

Rh-impregnated alumina foams and metallic microchannel reactors have been studied for production of hydrogen-rich syngas through short contact time catalytic partial oxidation (POX) and oxidative steam reforming (OSR) of propane. Effects of temperature and residence time have been compared for the two catalytic systems. Temperature profiles obtained along the central axis were valuable in understanding the different behaviour of the reactor systems. Gas phase ignition occurs in front of the metallic monolith at furnace temperatures above 700 °C, leading to lower hydrogen selectivity. Lowering the residence time below 10 ms for the microchannel monolith increases the syngas selectivity. This probably due to quenching of the gas phase reactions at high linear gas velocity, and suggests that microchannel reactors have potential for isolating kinetic effects and minimising gas phase contributions. The Rh/Al 2O 3 foam systems show higher initial syngas selectivity than the Rh-impregnated microchannel reactors, but deactivate rapidly upon temperature cycling, especially when steam is added as a reactant.

Modeling a Transport Phenomena Limited Reactivity in Short Contact Time Catalytic Partial Oxidation Reactors

The present paper describes a computational study of the short contact time catalytic partial oxidation of methane in fixed-bed reactors employing a rhodium-based catalyst. A monodimensional model was developed, and its validation was carried out on the basis of two experimental sets of literature data. Transport phenomena limited conditions and a local equilibrium reactivity along the catalytic bed were assumed. The last assumption provided an acceptable simplification to describe the complex microkinetic reactions taking place on the catalyst surface. The model results were satisfactorily in agreement with the measured values of conversion, product selectivity, and solid-phase temperature profiles along the fixed bed, at different space velocities and catalyst particle sizes. The numerical analysis, which allowed one to highlight the principles governing the system, also pointed out the existence of a local solid−gas temperature difference occurring within the catalytic bed. This difference dropped to zero when the reactions were completed. Finally, particular attention was devoted to the relationship between the reactor performance and transport phenomena, emphasizing the role of thermal conductivity and radiation within the fixed bed.

Short contact time catalytic partial oxidation of methane: analysis of transport phenomena effects

The physico-chemical features of short contact time catalytic partial oxidation (SCT-CPO) of methane to produce synthesis gas have been examined with experimental and theoretical modelling activities. The experiments have been performed in a fixed bed reactor equipped with IR thermography and thermocouples for a detailed temperature mapping of the solid and of the gas phases. The theoretical analysis has been developed considering a diffusion–reaction system where transport phenomena and chemical kinetics have been coupled and it has been demonstrated that in the reaction system, a transfer controlled operating regime is established where the oxygen transport from the bulk gas phase to the catalyst is the rate limiting step and where local temperature differences are originated between the solid phase surface and the gas phase.