Catalytic Partial Oxidation Process Research Articles

Fisher–Tropsch Synthesis for Conversion of Methane into Liquid Hydrocarbons through Gas-to-Liquids (GTL) Process: A Review

The interest in Gas-to-Liquid technology (GTL) is growing worldwide because it involves a two-step indirect conversion of natural gas to higher hydrocarbons ranging from Liquefied Petroleum Gas (LPG) to paraffin wax. GTL makes it possible to obtain clean diesel, naphtha, lubes, olefins, and other industrially important organics from natural gas. This article is a brief review discussing the state-of-the-art of GTL, including the basics of syngas manufacturing as a source for Fischer-Tropsch synthesis (FTS), hydrocarbons synthesis (Fischer-Tropsch process), and product upgrading. Each one is analyzed, and the main characteristics of traditional and catalysts technologies are presented. For syngas generation, steam methane reforming, partial oxidation, two-step reforming, and autothermal reforming of methane are discussed. For Fischer–Tropsch, we highlight the role of catalysis and selectivity to high molecular weight hydrocarbons. Also, new reactors technologies, such as microreactors, are presented. The GTL technology still faces several challenges; the biggest is obtaining the right H2:CO ratio when using a low steam-to-carbon ratio. Despite the great understanding of the carbon formation mechanism, little has been made in developing newer catalysts. Since 60–70% of a GTL plant cost is for syngas production, it needs more attention, particularly for developing the catalytic partial oxidation process (CPO), given that modern CPO processes using a ceramic membrane reactor reduce the plant’s capital cost. Improving the membrane’s mechanical, thermal, and chemical stability can commercialize the process. Catalytic challenges accompanying the FTS need attention to enhance the selectivity to produce high-octane gasoline, lower the production cost, develop new reactor systems, and enhance the selectivity to produce high molecular weight hydrocarbons. Catalytically, more attention should be given to the generation of a convenient catalyst layer and the coating process for a given configuration.

Computational Study of the Catalytic Partial Oxidation Process for Producing Synthesis Gas From Methane at Different Flow Velocities

Computational Study of the Catalytic Partial Oxidation Process for Producing Synthesis Gas From Methane at Different Flow Velocities

How CO2 poisons La2O3 in an OCM catalytic reaction: A study by in situ XRD-MS and DFT

Oxidative coupling of methane (OCM) is a catalytic partial oxidation process that converts methane directly into more valuable C2 products (ethane and ethylene). The mechanism related to selectivity and conversion is still not clear. Previous results suggested that the bulk structure change of the La2O3 catalyst is related to OCM activation performance. This work is focused on investigation of carbonates and the reaction products simultaneous formation over La2O3 catalyst utilizing coupled in situ XRD-MS. Semi quantitative analysis clearly reveals a positive dependence between CO2 and C2 products light-off temperature and the initial bulk La2O2CO3 concentration, indicating a strong correlation between carbonates and La2O3 catalyst poisoning. The activity of the La based catalyst is associated to its oxide form rather than to its oxycarbonate form. Based on operando results a two-step bulk La2O2CO3 decomposition model resulting in surface carbonates presenting on the catalyst surface between 500 °C and 800 °C is proposed. DFT calculations further confirm the proposed model and indicate surface carbonates do inhibit catalytic methane activation. It is concluded that CO32− species located in surface region of the catalyst operate as a direct La2O3 catalyst poison in the highly motivating OCM reaction.

Ethylene oxidation on unpromoted silver catalysts: Reaction pathway and selectivity analysis using DFT calculations

Chemical conversions in catalytic partial oxidation processes of light hydrocarbons are responsible for the production of numerous industrial chemicals, plastics, and intermediates. These processes are relatively expensive to perform, and are typically operated at high thermodynamic inefficiency, so the development of novel, highly efficient catalysts would prove to be very cost effective. Herein, our study focused on surface catalytic mechanisms of the ethylene oxide (EO) formation process. Periodic plane-wave Density Functional Theory (DFT) methods were used to analyze related reaction mechanisms on the Ag(111) surface facet with low coverage. Energetic changes of related species and pathways were calculated. Key surface species are identified to suggest the factors for the observed selectivity during EO formation. Our results are consistent with previous kinetic modeling efforts in the literature which did not employ DFT analysis. Lastly, our study demonstrates how fundamental theoretical investigations and multi-scale modeling techniques are currently impacting the advancement of rational catalyst design and microkinetic modeling techniques in the light hydrocarbon processing industry.

Catalytic partial oxidation of ethanol over Rh-coated monoliths investigated by the axially resolved sampling technique: Effect of H2O co-feed

The catalytic partial oxidation (CPO) of ethanol with H2O co-feed was studied in a laboratory scale adiabatic reactor on Rh/α-Al2O3 catalysts deposited on honeycomb monoliths. In order to understand the behavior of the homogeneous and the heterogeneous reactions taking place in the CPO process, axial temperature and concentration profiles were collected using a spatially resolved sampling technique. The effect of steam co-feed was studied at C/O ratio of 0.65, varying the H2O molar concentration in the feed from 0% to 10 %. H2O was added to the system by replacing part of the diluting N2, keeping a constant ethanol concentration. At increasing H2O feed content, ethanol conversion grew close to 100 %. The water gas shift reaction was promoted, which resulted in increased H2 yield and H2/CO ratio. Globally, thermal effects of the water co-feed were negligible. Noteworthy, a significant drop of the concentration of cracking products such as CH4, and C2H4 in the initial part of the reactor was observed in the presence of water co-feed. Beneficial effects on the catalyst stability were also observed by performing tests of CH4-CPO (a reference reacting system that, due to the sensitivity of the temperature profile to the catalyst activity, is used to detect catalyst deactivation processes in between ethanol CPO tests) and by TPO measurements on the used catalysts. Less pronounced drift of the temperature-profile in CH4-CPO and lower carbon deposition were in fact associated with the water co-feed operation of the reactor.

Thermal Deactivation of Rh/α-Al2O3 in the Catalytic Partial Oxidation of Iso-Octane: Effect of Flow Rate

Catalytic partial oxidation (CPO) of logistic fuels is a promising technology for the small-scale and on-board production of syngas (H2 and CO). Rh coated monoliths can be used as catalysts that, due to Rh high activity, allow the use of reduced reactor volumes (with contact time in the order of milliseconds) and the achievement of high syngas yield. As the CPO process is globally exothermic, it can be operated in adiabatic reactors. The reaction mechanism of the CPO process involves the superposition of exothermic and endothermic reactions at the catalyst inlet. Thus, a hot spot temperature is formed, which may lead to catalyst deactivation via sintering. In this work, the effect of the flow rate on the overall performance of a CPO-reformer has been studied, using iso-octane as model fuel. The focus has been on thermal behavior. The experimental investigation consisted of iC8-CPO tests at varying total flow rates from 5 to 15 NL/min, wherein axially resolved temperature and composition measurements were performed. The increase of flow rate resulted in a progressive increase of the hot spot temperature, with partial loss of activity in the entry zone of the monolith (as evidenced by repeated reference tests of CH4-CPO); conversely, the adiabatic character of the reformer improved. A detailed modelling analysis provided the means for the interpretation of the observed results. The temperature hot spot can be limited by acting on the operating conditions of the process. However, a tradeoff is required between the stability of the catalyst and the achievement of high performances (syngas yield, reactants conversion, and reactor adiabaticity).

Composite Rh/Zr0.25Ce0.75O2-δ-ƞ-Al2O3/Fecralloy wire mesh honeycomb module for natural gas, LPG and diesel catalytic conversion to syngas

The reactions of catalytic autothermal and steam conversion of n – C16H34 (model compound simulating diesel fuel), and partial oxidation of natural gas and LPG were studied using 0.24wt%Rh/(12wt%Zr0.25Ce0.75O2-δ-ƞ-Al2O3)/Fecralloy wire mesh honeycomb modules. The experiments were carried out in a flow setup in the temperature range of 550–960 °C and at atmospheric pressure. It was shown that the observed syngas (CO + H2) productivities were 65 and 53 m3Lcat−1h−1 (STP) at GHSV of 100,000 and 80,000 h−1 in natural gas and liquid petroleum gas catalytic partial oxidation processes, respectively. The product distributions were still close to the calculated equilibrium values. The catalyst activity was very high and, potentially, the maximum syngas productivity may even exceed experimentally demonstrated values.It was shown also that 0.24wt%Rh/(12wt%Zr0.25Ce0.75O2-δ-ƞ-Al2O3)/Fecralloy catalyst provided complete n-hexadecane conversion with the maximum syngas (CO + H2) productivity of 6.2 m3Lcat−1h−1 (STP) at GHSV of 13,300 h−1. The proposed concept of hydrogen-rich gas production from various hydrocarbon feedstocks in a multi-fuel catalytic reformer over single composite catalyst was proved feasible. The produced synthesis gas can be supplied as a fuel for power generation units based on high-temperature solid oxide fuel cells.

Online Kinetics Study of Oxidative Coupling of Methane over La2O3 for Methane Activation: What Is Behind the Distinguished Light-off Temperatures?

Oxidative coupling of methane (OCM) is a catalytic partial oxidation process that converts methane directly to valuable C-2 products (ethane and ethylene). The main difficulties from further investigation of this reaction are due to the nature of its high operating temperature and the severe reaction exothermicity. In this work, an especially designed online characterization setup is applied for this reaction, which achieved both precise bed temperature control and real-time product measurement. High-resolution temperature-dependent product rates of OCM (CO2, ethane, and ethylene) were obtained, and their behavior vs reaction conditions as well as the activation energy barriers above their onset temperatures are clearly differentiated over a recently reported high performance nanorod La2O3 catalyst. Different from general expectation, CO2, resulting from full methane oxidation, dominates all the products in the lower temperature region, whereas the C-2 species are only formed at much higher temperatures. Further analysis indicates that the selectivity and apparent activation energy for both COx and C-2 products are strongly influenced by the oxygen concentration and temperature. In combination with density functional theory calculations and additional experimental measurements, significant insights are brought to this high-temperature reaction of wide interest.

Catalytic Partial Oxidation of Iso-octane over Rh/α-Al2O3 in an Adiabatic Reactor: An Experimental and Modeling Study

Catalytic partial oxidation (CPO) of hydrocarbons represents an interesting technology for hydrogen production on mobile systems. We investigated the CPO of 2,2,4-trimethyl pentane (iso-octane), chosen as surrogate for gasoline. CPO experiments were carried out in a laboratory scale autothermal reformer with honeycomb monolith catalysts (2% Rh/α-Al2O3), equipped with probes for spatially resolved measurements of temperature and concentration. The iso-octane CPO process follows a reaction pathway which mainly consists of the exothermic combustion reaction and the endothermic steam reforming. The chemical reaction is very fast, and sharp gradients of temperature and concentration establish at the catalyst inlet. Similarly to the CPO of light hydrocarbons, the consecutive reaction mechanism results in the formation of a hot spot of temperature at the catalyst inlet. However, compared to light hydrocarbons, this phenomenology is specifically emphasized in the case of iso-octane, because of the higher overall ...

Modeling of natural gas partial oxidation in an in-house developed pilot scale catalytic reactor based on local thermodynamic equilibrium concept

A numerical model based on the concept of local thermodynamic equilibrium was developed to describe the catalytic partial oxidation processes in reactors with performance that exceeds laboratory scale. The developed model describes heat transfer in the catalytic porous layer and steel shell of the catalytic reactor, which has external heating. Computer simulation based on this model facilitates prediction of spatial temperature profiles and reactive mixture composition inside the reactor. The predictions of the numerical model are in agreement with the mixture composition at the reactor outlet as measured during steady-state working regimes in the context of different flow rates that ranged from 1.7 to 5.1Nm3/h.

Direct production of flexible H2/CO synthesis gas in a solid electrolyte membrane reactor

The development of novel configurations for the production of synthesis gas (syn-gas) of flexible H2/CO ratio is of great importance to reduce the cost for the synthesis of synfuels and high-value chemicals. In this work, we propose a radically novel approach to the direct production of syn-gas with flexible H2/CO ratio based on the solid electrolyte membrane reactor (SEMR). For that purpose, a single-chamber solid electrolyte membrane reactor based on yttria-stabilized zirconia (YSZ) has been developed (Pt/YSZ/Pt), where both active Pt catalysts–electrodes were exposed to the same reaction atmosphere (C2H5OH/H2O = 0.7 %/2 %). The application of different polarizations at temperature range (600–700 °C) allows to control the H2/CO ratio of the obtained syn-gas, i.e., the ratio was varied between 1.5 and 12 under polarization conditions. Unlike conventional catalytic partial oxidation processes, the H2/CO adjustment was managed without the requirement of external O2 feeding to the reactor. An increase in the applied current or potential caused the H2/CO ratio to increase vs. the open-circuit conditions where ethanol reforming occurred on the Pt catalyst–electrodes which is due to an increase in the rate of the electro-catalytic processes. On the other hand, a decrease in the H2/CO ratio at a fixed potential was achieved at higher temperatures due to the further reaction of the produced H2 with the rest of the species present in the gas phase, leading to a decrease in the faradaic efficiency. The proposed configuration may be of great interest especially for biorefinery applications where H2, syn-gas and electricity may be produced from bioethanol.

Precious metal-promoted Ni–Mg–Al–Fe–O catalyst for hydrogen production with fast startup via catalytic partial oxidation of butanol

The layered double hydroxides (LDH)-derived Ni–Mg–Al–Fe–O catalyst with/without precious metals of Rh, Ir, Ru and Pt was prepared by co-precipitation and impregnation, and tested in catalytic partial oxidation (CPOX) of butanol for fast and variable hydrogen production. The results of X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR) indicate that the Ni–Mg–Al–Fe–O catalyst without reduction has an induction period up to 8 h at 700 °C in the CPOX process because of the slow reduction of Ni species in solid solution of Mg(Ni)O during the CPOX process. With promotion of Rh in Ni–Mg–Al–Fe–O, there was high initial activity near 4.1 mol-H2/mol-butanol because the reducibility was improved and the Ni0 species emerged in the beginning and remained stable, suggesting that the Rh-NMAF catalysts can be a promising candidate with high initial activity and stability in CPOX of butanol for hydrogen production, especially for variable hydrogen supply for on-board applications. The Ni–Mg–Al–Fe–O catalyst promoted by Ir, Ru and Pt also showed potential in CPOX of butanol for hydrogen production.

Crude glycerol as a raw material for the liquid phase oxidation reaction

In the present work, crude and partially purified glycerol fractions received from large biodiesel production plant were used as a raw material in the catalytic partial oxidation process. Before using, each fractions were carefully characterized in order to identify and quantify the major contaminants. Depending on the purification degree, the weight concentration of glycerol in the different fractions varied from 40.3% to 98.2%, the methanol content did not exceed 29.1%, mineral salts (determined as ash) varied from 0.03% 6.6%, while the residual organic matter (non-glycerol and non-methanol, named here MONG-NM) was between 0.7% and 22.1%. The reaction of glycerol oxidation was carried out in the liquid phase over a commercial 1wt.% Pt/Al2O3 catalyst. The effect of each identified impurity type was independently studied, both in the presence and absence of base in the reaction mixture. The results indicated that MONG-NM is the most problematic compound, as it strongly hinders the reaction. As the post-reaction analysis of spent catalyst (Elemental Analysis and XPS) showed practically negligible leaching of platinum and lack of important changes in its oxidation state, the most probable explanation for observed decrease in glycerol conversion is blocking of glycerol access to the catalyst active sites by adsorbed heavy-weight components of MONG-NM. An attempt of regeneration and reusing of spent catalyst proved that such poisoning can be reversed by simple washing of catalyst with organic solvent enable to dissolve hydrophobic fatty acid derivatives. The mineral salts also have a detrimental effect on the glycerol oxidation process, but much tinier than that of MONG-NM. In contrast, the presence of methanol in the feed promoted the process reactivity, which was attributed to improved oxygen solubility in the methanol–water solutions (at least in the analysed range of methanol concentrations ≤5wt.%).

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.

Study on a Coupling Reactor for Catalytic Partial Oxidation of Natural Gas to Syngas

In the current paper, engineering issues for catalytic partial oxidation of natural gas to syngas have been investigated in a pilot plant. In contrast to the microreactor for catalyst evaluation, for a large scale fixed bed reactor operated under high temperature and pressure, attentions should be paid to: introduction method of feeding gases, preheat temperature of feeds, and the coupling of exothermic oxidation reactions with endothermic reforming reactions. As indicated by thermodynamic calculations at a pressure of 2.0 MPa, the reaction temperature should reach at least 1273 K in order to obtain a yield of CO higher than 80 percent. To reach such a high reaction temperature under adiabatic conditions, the feeding gases need to be preheated to a temperature within the range of 773-923 K. With safety considerations of explosion potential, a newly designed nozzle that can premix reactant gases well and thus is suitable for natural gas catalytic partial oxidation process, has been adopted in this pilot unit. A thermally coupled fixed bed reactor is then proposed and proved to be feasible based on thermodynamic calculations and experimental validations.

Study on a Coupling Reactor for Catalytic Partial Oxidation of Natural Gas to Syngas

In the current paper, engineering issues for catalytic partial oxidation of natural gas to syngas have been investigated in a pilot plant. In contrast to the microreactor for catalyst evaluation, for a large scale fixed bed reactor operated under high temperature and pressure, attentions should be paid to: introduction method of feeding gases, preheat temperature of feeds, and the coupling of exothermic oxidation reactions with endothermic reforming reactions. As indicated by thermodynamic calculations at a pressure of 2.0 MPa, the reaction temperature should reach at least 1273 K in order to obtain a yield of CO higher than 80 percent. To reach such a high reaction temperature under adiabatic conditions, the feeding gases need to be preheated to a temperature within the range of 773-923 K. With safety considerations of explosion potential, a newly designed nozzle that can premix reactant gases well and thus is suitable for natural gas catalytic partial oxidation process, has been adopted in this pilot unit. A thermally coupled fixed bed reactor is then proposed and proved to be feasible based on thermodynamic calculations and experimental validations.

Effects of H 2O and CO 2 addition in catalytic partial oxidation of methane on Rh

The autothermal catalytic partial oxidation (CPO) of methane was performed at short contact times (∼8 ms) over three Rh-based catalysts: 5 wt% Rh/ α-Al 2O 3, 5 wt% Rh/2 wt% γ-Al 2O 3/ α-Al 2O 3, and 5 wt% Rh/2 wt% Ce/2 wt% γ-Al 2O 3/ α-Al 2O 3. The effects of H 2O addition (10%, 20%, and 40% of the total feed) and CO 2 addition (20% and 35%) were studied over a wide range of inlet C/O ratios (0.75–1.2) by means of the capillary sampling technique. Over Rh/ α-Al 2O 3 samples, spatially resolved concentration profiles revealed that the rate of CH 4 reforming is independent of the concentration of H 2O and CO 2. Differences in the product distribution followed the behavior expected from water gas shift (WGS) chemistry: in H 2O-rich tests, the production of H 2 and CO 2 increased at the expense of H 2O and CO, while the opposite was observed in CO 2-rich tests. CPO experiments with a simultaneous feed of H 2O and CO 2 (40% H 2O, 20% CO 2, 20% CH 4, C/O = 1) provided direct evidence that H 2O is the preferential co-reactant of CH 4 in reforming and that CO 2 reforming is absent. Addition of a γ-Al 2O 3 washcoat to the catalyst significantly enhanced the rate of steam reforming while revealing the limits of Rh WGS activity. Products were equilibrated for nearly all cases examined over the Ce-promoted catalyst, indicating that WGS kinetics, either forward or reverse, have an important role in the CPO mechanism, particularly with H 2O and CO 2 co-feed. The experimental results clearly illustrate the flexible nature of CPO process. They show that the H 2/CO can be varied within a wide range of values in a one-step process, and syngas production is sustainable under highly diluted conditions.

Rh–Ni synergy in the catalytic partial oxidation of methane: surface phenomena and catalyst stability

Ni, Rh and Rh/Ni containing catalysts obtained from hydrotalcite type precursors have been studied in the partial oxidation of methane. The catalysts have been characterised by HRTEM to evaluate the effectiveness of the preparation method in the dispersion of the metal. The tests carried out in the partial oxidation of methane at a residence time of 12 ms did not allow to enlighten significant differences of activity among the catalysts due to the proximity of the results with those obtained at the thermodynamic equilibrium. New tests at very low residence times have allowed the catalyst evaluation in conditions far from the thermodynamic equilibrium and in which oxygen is still present. The catalytic bed length and the amount of catalyst have been chosen after the analysis of the thermal profile with the IR thermography. The IR thermography was used with the different catalysts to measure the maximum surface temperature trend as a function of the residence time. The tests carried out at very short residence times allow to compare the catalysts in conditions where O 2 is not totally converted and enlighten the high activity of the Rh/Ni catalysts in which the Ni is maintained in the reduced state by the Rh. The comparison of the catalysts have also been carried out studying the endothermic dry reforming at low residence times. The study of the dry reforming of methane have also been related to the evaluation of the activity of the consecutive reaction of the catalytic partial oxidation process, without the effect of a large heat production. Finally, the dry reforming was also used to measure the coke formation on the most active catalysts.

Solid electrolyte sensor for studying the behaviour of a partial oxidation catalyst

Oxygen-ion conducting solid electrolyte cells were prepared with Pt reference electrodes and Fe 2O 3–Sb 2O 4 working electrodes. The working electrode served as both electrode and catalyst during the partial oxidation of propene. The electrochemical cell allowed thermodynamic catalyst surface oxygen activities to be followed and acted as a sensor of catalyst state. It is clear that the catalyst was much more selective for acrolein formation at lower oxygen activities as indicated by the sensor signal. There is evidence to suggest that the oxygen activity measured by the sensor is as a result of the presence of adsorbed oxygen and not lattice oxygen. Based on the results it appears that potentiometric sensors could provide important additional information for catalytic partial oxidation process monitoring and control.

99/03107 Distributed injection catalytic partial oxidation process and apparatus for producing synthesis gas

99/03107 Distributed injection catalytic partial oxidation process and apparatus for producing synthesis gas