Low-temperature Oxidation Reaction Research Articles

A study on oxygen consumption mechanism of air-foam flooding in low-temperature oil reservoir

Air flooding/air-foam flooding recovery technology has been attracting attention in oilfield development. The key point to the application of this technology is to ensure that the oxygen injected with the air can be fully dissipated inside the reservoir to lower the explosion risk in production wells and reduce the oxidation of the pipeline. It is generally believed that the oxygen and crude oil can react more in low-temperature-oxidation (LTO) reactions above 80 °C. As a large amount of oxygen would be spontaneously consumed at this temperature, this technology is mainly used in reservoirs where the temperature is greater than 80 °C. In the fractured low-permeability reservoir of China's Yanchang oilfield, where the reservoir temperature is only approximately 30 °C, a wide range of crude oil LTO would not be triggered theoretically. However, we found that the oxygen content of the associated gas in the gas channeling wells is significantly lower than that in the air. This phenomenon suggests that, there are other factors that could consume oxygen apart from the LTO reaction. To verify this assumption, an oxygen dissipation core flooding experiment at 30 °C and 80 °C was carried out to evaluate the oxygen consumption at different temperatures. At the same time, in order to determine the main controlling factors and dissipation mechanisms of oxygen dissipation, theoretical analyses and experimental studies were carried out from the aspects of reductive mineral oxidation reaction in the rock surface and formation water, the physical absorption of the micropore and the dissolution of the reservoir fluid. The results show that at the same experimental conditions, the oxygen consumption at 30 °C is 38.14% lower than that at 80 °C. The oxygen consumption factors in the low-temperature reservoir mainly include the chemical reactions between the oxygen and reducing minerals, dissolution and retention of formation water and oil, adsorption of Van der Waals forces in the reservoir and physical electronic adsorption of the hydrogen-sulfur bonds and carbon-sulfur bonds. In Chang 6 Reservoir of Ganguyi oilfield, formation water could theoretically consume 56 mg/L (1.75 mmol/L) oxygen through dissolved Fe2+. The dissolution by formation water could absorb 11.85 mmol/L oxygen (experimental value). The dissolution by oil could absorb 69.25 mmol/L oxygen (experimental test value), and the oxygen physical adsorption rate of rock pore surface was 1.26 mmol/L. Together with the pilot test data, the results show that the LTO reaction of the stratum crude oil barely occurs in the reservoir at low temperature (30 °C). However, a large amount of oxygen dissipation could still be achieved. This study demonstrates that air-foam flooding could break the applicable limit temperature and could also be applied in low-temperature reservoirs.

High performance diesel oxidation catalysts using ultra-low Pt loading on titania nanowire array integrated cordierite honeycombs

High performance of an ultra-low Pt loading diesel oxidation catalyst can be achieved by using a combination of novel nano-array structured support, precise control of ultrafine active Pt particles, and an addition of H2 as a promoter into the exhausts. Highly stable mesoporous rutile TiO2 nano-array was uniformly grown on three-dimensional (3-D) cordierite honeycomb monoliths using a solvothermal synthesis. Atomic layer deposition was employed for precise dispersion of ultrafine Pt particles (0.95±0.24nm) on TiO2 nano-array with a Pt loading of 1.1g/ft3. Despite low Pt loading, the Pt/TiO2 nano-array catalyst shows impressive low-temperature oxidation reactivity, with the conversion of CO and total hydrocarbon (THC) reaching 50% at 224 and 285°C, respectively, in the clean diesel combustion (CDC) simulated exhaust conditions. The excellent activity is attributed to the unique nano-array structure that promotes gas-solid interaction and ultra-small Pt particle dispersion that increase surface Pt atoms. We also demonstrate that addition of more H2 into the exhaust can lower light-off temperature for CO and THC by up to ∼60°C and ∼30°C, respectively.

Effect of titania surface modification of mesoporous silica SBA-15 supported Au catalysts: Activity and stability in the CO oxidation reaction

As part of an ongoing effort to understand the deactivation and improve the stability of metal oxide-supported Au catalysts in the low-temperature CO oxidation reaction while maintaining their high activity, we have investigated the influence of a mesoporous silica SBA-15 substrate on the activity and stability of Au/TiO2 catalysts, which consist of a SBA-15 support surface modified by a monolayer of TiOx with Au nanoparticles on top. The extent of the TiOx surface modification was systematically increased, while the Au loading and the Au particle sizes were largely kept constant. Employing kinetic measurements at three different temperatures (30°C, 80°C, 180°C) and a number of ex situ methods as well as in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for catalyst characterization, we found that the activity of these catalysts increases significantly with the Ti concentration and with reaction temperature. The tendency for deactivation remains essentially unchanged. Detailed in situ DRIFTS measurements reveal that the Au nanoparticles are largely formed on the TiOx surface-modified areas of the SBA-15 support and that the tendency for surface carbonate formation is very low. The observed deactivation may at least partly be related to the accumulation of molecularly adsorbed H2O species, in particular at low temperatures (30°C). These are likely to be formed from surface hydroxyl groups, they may affect the reaction either by blocking of active sites or by blocking the adsorption of reactants on the substrate. Other effects, such as reaction induced changes in the titania layer, must however, play a role as well, both at 80°C and in particular at 180°C, where accumulation of adsorbed species is negligible. The mechanistic ideas are supported by reactivation tests subsequent to calcination at 400°C, which were found to fully restore the initial activity.

Express-method for measuring the octane number of gazolines on the basis of the thermal effect of the cold-flame oxidation reaction

A determination method for the octane number of gasolines by measuring the thermal effect of the low temperature oxidation reaction is proposed. In order to lower the analysis temperature, the reaction has been carried out with ozone on the thermistor surface at a temperature of a gas-vapor mixture equal to the end boiling point of gasoline.

Numerical study of air assisted cyclic steam stimulation process for heavy oil reservoirs: Recovery performance and energy efficiency analysis

Cyclic steam stimulation (CSS) has been widely applied asan effective technique for heavy oil reservoirs, but it is increasingly concerned in recent years for its limited oil recovery performance, low energy efficiency, high water consumption and great environmental footprints due to greenhouse gas emissions. The hybrid injection of air and steam in terms of low temperature oxidation (LTO) is an innovative technique for the development of heavy oil reservoirs, which can be operated based on the conventional well configuration and was firstly proposed as an enhanced oil recovery (EOR) process for mature heavy oil reservoirs encountered with low reservoir pressure, poor steam sweep efficiency and high water cut. In this study, numerical simulation study is conducted to evaluate the potentials of air assisted cyclic steam stimulation (AACSS) process as an alternative to CSS technique for heavy oil reservoirs. Effects of oil viscosity, LTO reaction and operated air to steam ratio on the well performance are examined for typical heavy oils. The results indicate that AACSS process can effectively improve oil recovery, enhance the energy efficiency and reduce CO2 emissions in comparison with CSS alone, which can be attributed to the thermal effect due to oil oxidation, reservoir repressurization and gas driving offered by air injection, and the AACSS process can be more economically and environmentally attractive than CSS alone. The production performance of AACSS process for ultra heavy oil reservoirs can be more pronounced in comparison with that of ordinary heavy oils, and the LTO characteristics of different oils and the feasible air to steam ratio are reservoir specific for field operation.

A comprehensive experimental and kinetic modeling study of n-propylbenzene combustion

This work presents a comprehensive experimental and kinetic modeling study on the combustion of n-propylbenzene. Flow reactor pyrolysis of n-propylbenzene at 0.04, 0.2 and 1 atm and laminar premixed flames of n-propylbenzene at 0.04 atm with equivalence ratios of 0.75 and 1.00 were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry. Jet stirred reactor (JSR) oxidation of n-propylbenzene at 10 atm with equivalence ratios of 0.5, 1.0, 1.5 and 2.0 was investigated with gas chromatography. A detailed kinetic model for n-propylbenzene combustion with 340 species and 2069 reactions was developed and validated against the data measured in this work. Model analyses such as rate of production analysis and sensitivity analysis were also performed to reveal the key pathways in the consumption of fuel and formation of polycyclic aromatic hydrocarbons (PAHs). The analysis results demonstrate that the benzylic CC bond dissociation reaction is crucial for the decomposition of n-propylbenzene in the pyrolysis and rich flame. Low temperature oxidation reactions play important roles in the high pressure JSR oxidation of n-propylbenzene. In addition, the formation pathways of PAHs are strongly related to the fuel structure, especially for the formation of bicyclic PAHs such as indene and naphthalene. Furthermore, the present model was also validated against previous experimental data of n-propylbenzene combustion under a wide range of conditions, including ignition delay times, laminar flame speeds, extinction strain rates, speciation profiles in atmospheric pressure JSR oxidation, flow reactor oxidation and high pressure shock tube pyrolysis and oxidation.

Effect of direct injection dimethyl ether on the micro-flame ignited (MFI) hybrid combustion and emission characteristics of a 4-stroke gasoline engine

The low temperature combustion is required for an internal combustion gasoline engine to achieve higher thermal efficiency and lower NOx emissions. The gasoline controlled auto-ignition (CAI) has been extensively researched to achieve low temperature combustion but its lack of control in combustion process has limited its applications. To overcome this problem, dimethyl ether (DME) is directly injected into the cylinder to generate multiple micro-flame ignition sites and regulate the entire heat release of premixed gasoline mixture. This micro-flame ignited (MFI) hybrid combustion was achieved in a 4-stroke gasoline engine in this work. The results show that the heat release process consists of three stages: stage I of low temperature oxidation reactions, followed with a short delay of a few crank angles by stage II of high temperature reactions of DME and the main combustion of premixed gasoline mixture in stage III. With the increased amount of DME in the late injection, the start of main combustion advances and the combustion duration reduces for both single and split injections, which results in lower HC and CO emissions. The introduction of split DME injections improves the combustion process and reduces HC and CO emissions as well as the maximum thermal efficiency.

The decomposition of mixed oxide Ag2Cu2O3: Structural features and the catalytic properties in CO and C2H4 oxidation

The mixed silver-copper oxide Ag2Cu2O3 with a paramelaconite crystal structure is a promising material for catalytic applications. The as-prepared sample of Ag2Cu2O3 consisted of brick-like particles extended along the [001] direction. A combination of physicochemical techniques such as TEM, XPS and XRD was applied to investigate the structural features of this mixed silver-copper oxide. The thermal stability of Ag2Cu2O3 was investigated using in situ XRD under different reaction conditions, including a catalytic CO+O2 mixture. The first step of Ag2Cu2O3 decomposition was accompanied by the appearance of ensembles consisting of silver nanoparticles with sizes of 5–15nm. Silver nanoparticles were strongly oriented to each other and to the surface of the initial Ag2Cu2O3 bricks. Based on the XRD data, it was shown that the release of silver occurred along the a and b axes of the paramelaconite structure. Partial decomposition of Ag2Cu2O3 accompanied by the formation of silver nanoparticles was observed during prolonged air storage under ambient conditions. The high reactivity is discussed as a reason for spontaneous decomposition during Ag2Cu2O3 storage. The full decomposition of the mixed oxide into metallic silver and copper (II) oxide took place at temperatures higher than 300°C regardless of the nature of the reaction medium (helium, air, CO+O2). Catalytic properties of partially and fully decomposed samples of mixed silver-copper oxide were measured in low-temperature CO oxidation and C2H4 epoxidation reactions.

Thermal Conductivity Impact on Thermal Stability of Reactive Materials

The impact of thermal conductivity on the thermal stability of a combustible material is studied in a stockpile modelled in a long cylindrical pipe. Two combustible material systems, one with constant thermal conductivity, the other one with variable thermal conductivity, are compared to analyse thermal stability in each case. A combustible material is the one that contains carbons or hydrocarbons that readily react with the oxygen of the system. Low-temperature oxidation or exothermic chemical reaction is the primary cause of spontaneous ignition. This is a theoretical study that involves mathematical approach to do the investigation. The nonlinear partial differential equations for heat transfer are solved numerically using the Finite Difference Method (FDM). Effects of embedded kinetic parameters on the temperature of the system are depicted graphically and discussed accordingly.

Chemical-structural properties of the coke produced by low temperature oxidation reactions during crude oil in-situ combustion

Chemical-structural properties of the coke produced by crude oil low temperature oxidation (LTO) reactions during in-situ combustion are still highly lacking due to the difficulty in coked sand characterization. This study proposed an experimental methodology to prepare the useful LTO coke with the chemical-structural properties studied using a combination of Energy-dispersive X-ray spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) techniques. The XRD and the HRTEM analyses showed the LTO coke mainly consisted of highly disorder amorphous structures with limited amount of poorly order ‘onion-like’ structures. The LTO coke was found to contain numerous oxygen functionalities and highly-substituted aromatic rings. The concentration of the carbonyl showed no significant decline with the LTO temperature increasing to 310°C. Nevertheless, the carbon structure with sp3-rich characteristics was found to selectively consumed by O2 to reduce the amount of coke deposition, and enriched the aromatic layer systems as inferred by Raman and FTIR analyses. There was a good agreement between the amount of the ‘onion-like’ structures viewed from HRTEM and the changes in the ether bridging groups. Additionally, the changes in the coke chemical-structural properties agreed with the measured coke reactivity by Thermogravimetric analyses.

Catalytic effect of in-situ preparation of copper oxide nanoparticles on the heavy oil low-temperature oxidation process in air injection recovery

ABSTRACTIn situ prepared hydrophobic CuO nanoparticles, about 84.3 nm in mean diameter, was synthesized and used to catalyze heavy oil low-temperature oxidation (LTO) reaction. Experimental results showed the average oxygen consumption rate with CuO nanoparticles addition increased by 1.4 times, and the residue oxygen content in tail gas in autoclave was decreased from 8.76% to 3.9% compared to the blank experiment (without CuO nanoparticles). In addition, the CuO nanoparticles could facilitate the cleavage reaction during LTO. This study can provide guidelines to improve effectively the safety of air flooding technology in the heavy oil.

The effect of low-temperature oxidation in air-assisted steam flooding process for enhancing oil recovery

ABSTRACTAir-assisted steam flooding is a new promoting technique for enhanced oil recovery compared to the other traditional thermal recovery methods. In this study, five experiments, including one steam flooding experiment, three combined steam–air flooding experiments, and one combined steam–N2 flooding experiment were studied, under the conditions of 180 °C and back-pressure valve of 8 MPa, with sand-packed model. The volume fraction of mixed gas in these four combined steam–air (or N2) flooding experiments were 80% steam+20% air, 60% steam+40% air, 40% steam+60% air, and 60% steam+40% N2, respectively. The experimental results showed that air-assisted steam flooding could enhance the oil displacement efficiency when the volume fraction of air and steam was in a certain number, and the optimal condition is 60% steam+40% air. Furthermore, water cut curves and saturate, aromatic, resin, and asphaltene (SARA) analysis results also demonstrate that the low-temperature oxidation reaction in air-assisted steam flooding process advantageous to profile control of generating high viscosity “PLUG” to seal high-permeability channel in reservoir.

Theoretical kinetic studies for low temperature oxidation of two typical methylcyclohexyl radicals

To improve the understanding of low temperature oxidation of methyl cyclohexane, the potential energy surfaces for O2 addition to two of its radicals (tcy-C6H10(*)CH3 with a tertiary radical site and ortho-cy-C6H10(*)CH3 with a secondary radical site in the ortho position to the methyl substitution) have been investigated by high level quantum chemical calculations. The reaction kinetics was studied by the ab initio transition state theory based on master equation methodology. The relationship between low temperature oxidation reactivity and molecular structures was explored, typically in terms of the barrier heights of 1,5 H-shift for peroxy radicals. The computed phenomenological rate constants reveal that the ROO stabilization dominates the fates of two methyl cyclohexyl radicals reacting with O2 at pressures higher than 1atm over the studied temperature range. The balance between ROO stabilization, HO2 elimination, QOOH stabilization, and OH formation was further revealed by branching ratios of these four types of reactions. This study extends kinetic data for cyclic alkanes oxidation in a wide range of pressure and temperature.

Acid-modified clinoptilolite as a support for palladium\u2013copper complexes catalyzing carbon monoxide oxidation with air oxygen

Samples of natural clinoptilolite were modified by an acid–thermal method at nitric acid concentrations of 0.25, 0.5, 1.0, and 3.0 M and a contact time of 30 min. A series of catalysts, K2PdCl4–Cu(NO3)2–KBr/S (S = 0.25H-CLI, 0.5H-CLI, 1H-CLI, and 3H-CLI) was obtained. All samples were investigated by X-ray phase and thermogravimetric analysis, FT-IR spectroscopy, water vapor ad/desorption and pH metric method. Besides, K2PdCl4–Cu(NO3)2–KBr/S samples were tested in the reaction of low-temperature carbon monoxide oxidation. It have been found that, owing to special physicochemical and structural-adsorption properties of 3H-CLI, it promotes formation of the palladium–copper catalyst providing carbon monoxide oxidation at the steady-state mode down to CO concentrations lower than its maximum permissible concentration at air relative humidity varied within a wide range.

An Improved Kinetics Model for In Situ Combustion of Pre-Steamed Oil Sands

In situ combustion (ISC) has been recently evaluated as a follow-up process to steam assisted gravity drainage (SAGD) with the expectation to combine the advantages of SAGD and ISC. Before the design of such a hybrid process, it is important to understand the chemical reactions between air (or oxygen) and residual oil within a SAGD chamber in the presence of water and steam in order to simulate the process with a reasonable degree of confidence. In this study, an improved reaction kinetics scheme, in terms of Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractions, is proposed to represent the complex chemical reactions during ramped temperature experiments. From the results of a set of laboratory ramped temperature oxidation (RTO) tests, the oxidation behavior at different temperatures has been carefully analyzed. On the basis of the analysis, a reaction kinetics model consisting of low temperature oxidation, thermal cracking, and high temperature oxidation reactions has been developed. This model...

Analysis of the effects of copper nanoparticles on in-situ combustion of extra heavy-crude oil

Catalyzed in-situ combustion of extra heavy crude-oil was studied. The effects of copper nanoparticles (Cu-NP) on combustion were quantified by measuring crude-oil oxidation kinetics and elucidated by capturing front and fuel deposition behavior. Ramped temperature oxidation experiments, coupled with isoconversional analysis, helped measure reaction kinetics. Improvement in the rate of combustion was seen when the nanoparticles were present at a concentration of 1000ppm in the aqueous phase. Chiefly, the apparent activation energy of the high-temperature oxidation region decreased. Cu-NP also serve as a reaction inhibitor of low-temperature oxidation (LTO), which is of interest because LTO reactions increase the viscosity of the virgin oil downstream of the combustion front. As a result of this, the alteration of LTO reactions, and the change in fuel formation, the presence of Cu-NP help maintain a greater front temperature. Thermogravimetric analysis shows that the oxidation behavior of the nanoparticles, namely the change of surface and bulk oxidation state, determines the rate and temperature that low-temperature oxidation and high-temperature oxidation occur for the median particle size distribution. Finally, potentiometric titration of the produced fluids shows that Cu-NP change the type of oil produced and decrease the amount of water created during the process.

Thermal characterization of crude oils in the presence of limestone matrix by TGA-DTG-FTIR

In present work oxidation of two heavy oils in limestone matrix was studied using simultaneous thermogravimetry (TGA), derivative thermogravimetry (DTG) and FTIR-spectroscopy techniques in the temperature range from 25 to 900°C. Before the measurements, the composition and properties of crude oils and limestone were evaluated. Obtained TG and DTG curves shows four different reaction regions: low temperature oxidation (LTO), fuel deposition (FD), high temperature oxidation (HTO) and decomposition of limestone. LTO reactions were accompanied by evaporation of light hydrocarbons, which was confirmed by appearance of stretching vibration bands of C-H groups in FTIR-spectra of evolved gases. Formation of carbon dioxide was observed for all oxidation reaction regions according to spectroscopic data. At the same time, CO was formed only in HTO region for both studied crude oils. Despite the different composition two crude oils have practically the same reactions intervals and peak temperatures. However, crude oil with higher API-gravity has a greater mass loss at the LTO and evaporation regions. The conversion of heavier oil with higher content of asphaltenes is larger during the high-temperature oxidation step.Three different kinetic models (Arrhenius, Coats & Redfern and Ingraham & Marrier) were used for analysis of TGA-DTG curves in LTO and HTO regions. Activation energy values of the crude oil samples were varied between 6.9–10.6kJ/mol in low temperature oxidation and 91.8-.0–181.9kJ/mol in high temperature oxidation regions. For two crude oils activation energies are similar in low temperature oxidation region. In high temperature oxidation region, crude oil with higher content of asphaltenes has larger activation energy.

Variations in in-situ combustion performance due to fracture orientation

In-situ combustion (ISC), being one of the most successful thermal enhanced oil recovery methods, is highly sensitive to reservoir heterogeneities. In the present study, we investigated the impact of fracture orientation on ISC performance through one dimensional combustion tube experiments on a Canadian bitumen, which possesses good burning characteristics. Two ISC experiments with fractures oriented perpendicular and parallel to the air injection direction were conducted at identical initial and experimental conditions. Fracture formation was visualized with X-ray computed tomography. Temperature profiles, gas compositions, and oil and water production data were recorded continuously during the experiments. Oil upgrading was quantified through viscosity measurements and weight percent of Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractions. SARA fractions were further characterized using Fourier Transform Infrared Spectroscopy (FTIR). Metal content of produced water samples was determined with Inductive Coupled Plasma-Mass Spectroscopy (ICP-MS). Our results show that both fracture types interrupted stable propagation of the combustion front; while the oxygen utilization rate was detected to be lower in the presence of parallel fractures. Thus, parallel fractures led to poorer ISC performance, resulting in lower combustion front velocity and oil production rate compared to perpendicular fractures. Furthermore, the lower oxygen utilization rate increased the interaction between displaced oil and oxygen at lower temperature regions, resulting in Low Temperature Oxidation (LTO) reactions. The produced oil density for parallel fractures was found to be higher than for perpendicular fractures. This difference was attributed to the structural differences in aromatics fraction, mainly determined through FTIR analysis. On the other hand, for both fracture orientations it was observed that the oil-water interaction in terms of metal content of produced water was insignificant due to high temperature oxidation (HTO) reactions.

High activity and negative apparent activation energy in low-temperature CO oxidation – present on Au/Mg(OH)2, absent on Au/TiO2

Aiming at a better understanding of the unusual low-temperature CO oxidation reaction behavior on Au/Mg(OH)2 catalysts, we investigated this reaction mainly by combined kinetic and in situ IR spectroscopy measurements over a wide range of temperatures, from −90 °C to 200 °C.

Displacement mechanisms of air injection for IOR in low permeability light oil reservoirs

Air injection into light oil reservoirs has been proven to be a valuable improved oil recovery (IOR) process and is being successfully implemented worldwide in many oilfields. It specially offers unique technical and economic opportunities for tertiary or secondary oil recovery in light oil reservoirs with low permeability in which conventional water injection techniques have been unsuccessful and/or uneconomical. This paper provides a comprehensive overview on the oxidation and IOR process of air injection into low permeability light oil reservoir based on detailed analysis of some field projects and the results of laboratory testing and reservoir simulation of a typical light oil reservoir, the Q131 Block. The reaction mechanisms of low temperature oxidation (LTO) and high temperature oxidation (HTO or in-situ combustion) are particularly addressed in this study. Air flooding displacement efficiency experiment was carried out without water injection, and an oil recovery of more than 40% of hydrocarbon pore volume (HCPV) was observed. A series of high-pressure oxidation experiments using the typical light oil were conducted in the temperature range of 98°C to 180°C. The results showed high oxidation and carbon dioxide (CO2) conversion rates, which are both favourable in terms of oxygen consumption. A conceptual full field compositional reservoir simulation model of the targeted low permeability block was also used to examine the reaction schemes, thermal effect of LTO reactions and IOR mechanisms. [Received: March 22, 2014; Accepted: February 7, 2016]