High-pressure Differential Scanning Calorimetry Research Articles

Oxidation Characteristics and Kinetics of Shale Oil Using High-Pressure Differential Scanning Calorimetry

In situ combustion (ISC) has received much attention in the area of the development of shale oil reservoirs in recent years. The primary mechanism of interest for ISC is the oxidation kinetics of t...

Exothermicity of hydrothermal carbonization: Determination of heat profile and enthalpy of reaction via high-pressure differential scanning calorimetry

Hydrothermal carbonization (HTC) is known for being exothermic, an aspect that can lower the external energy demand necessary to face thermal losses and therefore be conducive to the overall HTC process thermal efficiency. Also, heat profiles can help explore kinetics and generally provide an insight into the HTC process. Despite the potential of the HTC exothermicity, only a few studies examined it and with different methodologies. This work aims to deepen this aspect by exploring heat profiles, enthalpy of reaction, and comparing two experimental methods by performing an experimental campaign using a power-compensated high-pressure differential scanning calorimeter (DSC). Three substrates (glucose, cellulose, and grape seeds) were hydrothermally carbonized at 180, 200, 220, and 250 °C at a biomass to water mass ratio of 0.25. To determine net heat profiles and enthalpies, water thermal effects were removed using two approaches, consisting of running a thermal program on the water alone or the exhaust, i.e. the products after the reaction. An instrument baseline considering both a zero-line and a time-drift was considered. Results show that both methods allow inferring similar enthalpy values at low operating temperature, while at high temperature a difference in the heat capacity of the liquid phase (due to the production of compounds dissolved in the liquid phase and absorbed on the solid) can affect the results related to the exhaust approach. In both cases, higher temperatures favor the exothermic peak intensity, the curve sharpening, and the increase (in absolute value) of reaction enthalpies. These are in the ranges −0.20 ÷ −0.86 MJ/kg, −0.61 ÷ −1.33 MJ/kg, and −0.42 ÷ −1.53 MJ/kg for glucose, cellulose, and grape seeds, respectively.

High pressure differential scanning calorimetry of poly(lactic acid) in presence of CO2 up to 100 MPa

For the processing of sustainable polymers with compressed CO2 to produce innovative products, knowledge of the thermodynamic properties of the polymer-CO2 system is essential. In this work, the thermal behaviour of three different poly(lactic acid) (PLA) grades, 2003D, 3251D and 8052D, from NatureWorks was determined experimentally using high pressure differential scanning calorimetry (HP-DSC) at CO2 pressures up to 100 MPa. After the HP-DSC had been extensively calibrated using potassium, sodium and indium, the thermal transition temperatures of the biopolymers were determined as a function of CO2 pressure. The melting and crystallization temperatures of the PLA grades were found to be up to 84 K lower in the presence of CO2. In addition, the crystallinity of the three biopolymers was investigated. It was shown that the degree of crystallinity was dependent on both the melting temperature and the CO2 pressure. In fact, a striking parabolic dependency which is also correlated with D-lactide content and molar mass was observed.

Rapid screening method for hydrate agglomeration and plugging assessment using high pressure differential scanning calorimetry

Gas hydrate formation during subsea oil and gas production can result in flowline blockages, which present enormous economic and safety risks. Certain crude oils have natural anti-agglomerant (AA) properties, which facilitate their non-plugging behavior over a defined operating window. Thus, it is crucial to be able to easily screen a crude oil system for its tendency to form hydrate plugs. In this paper, we present a Hydrate Plugging Assessment (HPA) technique that can be used as a rapid screening method to evaluate the plugging tendency using a high pressure differential scanning calorimeter (HP-DSC). The technique requires a small crude oil sample (~15 mg), and the experimental time is relatively short. In this work, HP-DSC tests were conducted on 13 crude oils (22 to 45 ˚API). Tests were conducted at various water contents, salinity, chemical dosage (without/with AAs), and different hydrate structures. The results show that an increase in water content destabilizes the emulsion, and increases the hydrate plugging risks. An increase in salinity decreases hydrate plugging tendency. Different hydrate crystal structures showed that for a similar water content, salinity, and driving force, structure II (sII) hydrates have a slightly greater agglomeration tendency compared to structure I (sI) hydrates. Finally, the effect of combining a low stability oil with a high stability oil showed that the resulting emulsion retained the high stability property, paving the possibility for natural oil treatment. In summary, these studies show that the HPA technique is a cost-effective and attractive method to evaluate hydrate plugging tendency.

Effect of Ring-Configuration on Pyrolysis and V2O5Catalyzed Oxidation of Polycyclic Aromatic Hydrocarbons

Conversion of polycyclic aromatic hydrocarbons (PAHs) through oxidative ring-opening can be used as a potential strategy for upgrading of aromatic-rich fractions of heavy oil and bitumen. At the core of such a process is the oxidation of PAHs to produce quinonoids, further oxidation of quinonoids to form ring-opened carboxylic acids, and finally decarboxylation of the carboxylic acids. The fused ring systems in PAHs include linear and angular ring-configurations, which affect pyrolysis and oxidation selectivity. This study evaluated the effect of the ring-configuration of PAHs on pyrolysis and on oxidation over a metal oxide catalyst (V₂O₅). Pyrolysis takes place in parallel with catalytic oxidation, and so it has an effect on the observed conversion chemistry. Liquid-phase pyrolysis and V₂O₅-catalyzed conversion of anthracene, phenanthrene, anthraquinone, and phenanthrenequinone were studied individually. All experimental work was conducted under a nitrogen atmosphere to avoid autoxidation. Results from high-pressure differential scanning calorimetry (HP-DSC) as well as from batch oxidation reactions indicated differences in reactivities due to the ring-configurations of both PAHs and their corresponding quinonoids. The reactivity sequence over V₂O₅ for PAHs was anthracene > phenanthrene as the increase in π-sextets in anthracene provided additional driving force toward oxidation. On the contrary, the reactivity over V₂O₅ of the corresponding quinonoids was phenanthrenequinone > anthraquinone. The angular configuration of phenanthrenequinone led to the carbonyl groups to be adjacent and to the carbons participating in that C–C bond to have an aliphatic nature, which increased the reactivity of the bond. The angular ring-configuration of phenanthrenequinone favored intramolecular ring-closing reactions, while the linear ring-configuration of anthraquinone exhibited higher stability toward oxidation. Conversion of anthraquinone led to products of oxygen removal via anthrone as well as to some ring-opened products. Compared to pyrolysis, V₂O₅ accelerated the conversion of PAHs and their corresponding quinonoids. Regardless of the ring-configuration, catalytic oxidation of PAHs over V₂O₅ did not favor production of ring-opened products. The study highlighted the importance of a hydrogen source, possibly water, for a successful ring-opening.

Safety Concerns for MOF Syntheses—Understanding the Behavior of DMF Mixtures at Elevated Temperature and Pressure

Herein we report how various metal–organic framework (MOF) reaction mixtures behave at elevated temperature and pressure. Adiabatic calorimetry and high-pressure differential scanning calorimetry e...

Continuous Extraction of Black Liquor Salts under Hydrothermal Conditions

In hydrothermal valorization of black liquor (BL) from the Kraft process, the separation of inorganic salts is pivotal to prevent them from fouling downstream equipment such as reactors and for the cost-efficient recycling of salts into pulp cooking chemicals. In this work, the phase behavior of the inorganic salts present in BL was studied in supercritical water and the conditions for the separation from BL were optimized. A high-pressure differential scanning calorimetry study indicated the concomitant precipitation of salts and the formation of a second salt-rich liquid-like phase. The potassium-to-sodium ratio was found to strongly impact the phase behavior of the salt mixture. Potassium was found to prevent salt precipitation and to lead to the formation of a second liquid-like phase alone. At K/(K + Na) ≥ 0.4, a steady salt separation could be achieved, enabling the continuous extraction of up to 96% of the salts in a concentrated brine effluent.

Influence of Water Saturation, Grain Size of Quartz Sand and Hydrate-Former on the Gas Hydrate Formation

The development of technologies for the accelerated formation or decomposition of gas hydrates is an urgent topic. This will make it possible to utilize a gas, including associated petroleum one, into a hydrate state for its further use or to produce natural gas from hydrate-saturated sediments. In this work, the effect of water content in wide range (0.7–50 mass%) and the size of quartz sand particles (porous medium; <50 μm, 125–160 μm and unsifted sand) on the formation of methane and methane-propane hydrates at close conditions (subcooling value) has been studied. High-pressure differential scanning calorimetry and X-ray computed tomography techniques were employed to analyze the hydrate formation process and pore sizes, respectively. The exponential growth of water to hydrate conversion with a decrease in the water content due to the rise of water–gas surface available for hydrate formation was revealed. Sieving the quartz sand resulted in a significant increase in water to hydrate conversion (59% for original sand compared to more than 90% for sieved sand). It was supposed that water suction due to the capillary forces influences both methane and methane-propane hydrates formation as well with latent hydrate forming up to 60% either without a detectable heat flow or during the ice melting. This emphasizes the importance of being developed for water–gas (ice–gas) interface to effectively transform water into the hydrate state. In any case, the ice melting (presence of thawing water) may allow a higher conversion degree. Varying the water content and the sand grain size allows to control the degree of water to hydrate conversion and subcooling achieved before the hydrate formation. Taking into account experimental error, the equilibrium conditions of hydrates formation do not change in all studied cases. The data obtained can be useful in developing a method for obtaining hydrates under static conditions.

Phase Behaviour of Methane Hydrates in Confined Media

In a study designed to investigate the melting behaviour of natural gas hydrates which are usually formed in porous mineral sediments rather than in bulk, hydrate phase equilibria for binary methane and water mixtures were studied using high-pressure differential scanning calorimetry in mesoporous and macroporous silica particles having controlled pore sizes ranging from 8.5 nm to 195.7 nm. A dynamic oscillating temperature method was used to form methane hydrates reproducibly and then determine their decomposition behaviour—melting points and enthalpies of melting. Significant decreases in dissociation temperature were observed as the pore size decreased (over 6 K for 8.5 nm pores). This behaviour is consistent with the Gibbs–Thomson equation, which was used to determine hydrate–water interfacial energies. The melting data up to 50 MPa indicated a strong, essentially logarithmic, dependence on pressure, which here has been ascribed to the pressure dependence of the interfacial energy in the confined media. An empirical modification of the Gibbs–Thomson equation is proposed to include this effect.

Insights into the self-preservation effect of methane hydrate at atmospheric pressure using high pressure DSC

The self-preservation effect of CH4 hydrate can facilitate the solidified storage and transport of natural gas at mild temperature and pressure conditions. However, the factors affecting the self-preservation of CH4 hydrate are complex and the impacts are not well known. In this work, a high pressure micro-differential scanning calorimeter (HP μ-DSC) was employed to elucidate the impact of preservation time, preservation temperature, and heating rate on the self-preservation of CH4 hydrate at atmospheric pressure (0.1 MPa) from the perspective of thermal analysis. It was found that CH4 hydrate can be stably preserved at 0.1 MPa in the temperature range from 253.15 to 268.15 K, and the self-preservation effect of CH4 hydrate was independent of the preservation time while no heat was injected into the preservation system. This will avail long-distance storage and transport of natural gas under low energy consumption conditions. In addition, two dissociation regimes of CH4 hydrate were identified when varying the heating rate from 0.1 K/min to 1 K/min. At the small heating rate of 0.1 K/min, the ice layer melted prior to the dissociation of CH4 hydrate. When the heating rate was increased to 0.5 and 1 K/min, the ice layer and CH4 hydrate melted simultaneously. Therefore, a large heating rate can be used to recover CH4 quickly from the dissociation of CH4 hydrate and thus the operating time will be saved.

Metal-Organic Framework HKUST-1 Promotes Methane Hydrate Formation for Improved Gas Storage Capacity.

The large demand of natural gas consumption requires an effective technology to purify and store methane, the main component of natural gas. Metal-organic frameworks and gas hydrates are highly appealing materials for the efficient storage of industrially relevant gases, including methane. In this study, the methane storage capacity of the combination of methane hydrates and HKUST-1, a copper-based metal-organic framework, was studied using high pressure differential scanning calorimetry. The results show a synergistic effect, as the addition of HKUST-1 promoted hydrate growth, thus increasing the amount of water converted to hydrate from 5.9 to 87.2% and the amount of methane stored, relative to the amount of water present, from 0.55 to 8.1 mmol/g. The success of HKUST-1 as a promoter stems mainly from its large surface area, high thermal conductivity, and hydrophilicity. These distinctive properties led to a kinetically favorable decrease in hydrate growth induction period by 4.4 h upon the addition of HKUST-1. Powder X-ray diffraction and nitrogen isotherm suggests that the hydrate formation occurs primarily on the surface of HKUST-1 rather than within the pores. Remarkably, the HKUST-1 crystals show no significant changes in terms of structural integrity after many cycles of hydrate formation and dissociation, which results in the material having a long life cycle. These results confirm the beneficial role of HKUST-1 as a promoter for gas hydrate formation to increase methane gas storage capacity.

Improving heavy oil oxidation performance by oil-dispersed CoFe2O4 nanoparticles in In-situ combustion process for enhanced oil recovery

In this work, bimetallic oxide CoFe2O4 nanoparticles were synthesized by the hydrothermal method. CoFe2O4 nanoparticles were coated by oleic acid (CoFe2O4@oleic acid) to provide the oil-dispersed catalyst for accelerating heavy oil oxidation in in-situ combustion (ISC) process for enhanced oil recovery (EOR). The synthesized CoFe2O4 and CoFe2O4@oleic acid nanoparticles were characterized by XRD, Mössbauer spectroscopy, and high-resolution field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) analysis system, etc. The catalytic performance of CoFe2O4 and CoFe2O4@oleic acid nanoparticles in heavy oil oxidation process was studied by TG-FTIR and high-pressure differential scanning calorimetry (HP-DSC) as well as kinetics calculation using isoconversional methods (KAS, OFW, and Friedman). The results showed that CoFe2O4@oleic acid nanoparticles were gradually decomposed during the oxidation process and formed CoFe2O4 nanoparticles that have most likely cationic distribution Co0.1Fe0.9[Fe1.1Co0.9]O4. CoFe2O4@oleic acid nanoparticles showed a much higher catalytic activity than CoFe2O4, which benefits from the uniform dispersion and distribution of CoFe2O4@oleic acid and its decomposed products (CoFe2O4) in the entire oxidation process of the heavy oil. It significantly shifted the FD and HTO reaction into lower temperatures, enhanced the heat release, and reduced the energy barriers of FD, thus promoting the formation of coke and its combustion with high efficiency. The high catalytic activity together with its low cost make this catalyst a good candidate for its wide use in the ISC process for improving its combustion efficiency and success rate for heavy oil production.

Effect of Temperature on the Chemical Composition and Physicochemical Properties of Diester Aviation Lubrication Oil

High temperature is the main factor responsible for degrading the lubrication and antiwear properties of aero-lubricating oils. Accordingly, this study assessed the effects of thermal treatment of diester aviation lubricating oil and the associated mechanism. Fourier-transform infrared spectroscopy and gas chromatography/mass spectrometry analyses showed that low-molecular-weight compounds, such as monoesters, diesters, alcohols, and olefins, were the primary degradation products. An assessment of the degradation mechanism of bis(2-ethylhexyl)decanedioate showed that pyrolysis, resulting in the cleavage of β-C–H and C–C bonds, was the main process involved. Additional investigation using advanced polymer chromatography showed that the molecular weights of oil samples changed slightly at high temperatures, while the viscosity and viscosity-temperature index values were relatively stable. High-pressure differential scanning calorimetry established that the thermal oxidation stability of these oils decreased above 250°C. Finally, variations in the chemical compositions of the oil samples were found to be highly correlated with changes in physicochemical properties during thermal processing, with the formation of low-molecular-weight polar compounds greatly increasing the acid numbers of the oils.

Fabrication of biodegradable poly (lactic acid)/carbon nanotube nanocomposite foams: Significant improvement on rheological property and foamability

Recently, biodegradable macromolecules have been highly desired as a promising alternative for traditional oil-based plastics to work out the eco crisis and biological health problems triggered by microplastics. Herein, we presented a simple, effective, environmentally friendly and CO2-based foaming methodology for fabricating ultra-low-density poly (lactic acid)/carbon nanotube (PLA/CNTs) nanocomposite foam. By the gradual incorporation of CNTs, three kinds of networks generated in PLA/CNTs nanocomposites and had a distinct reinforcement influence on their melt viscoelasticity, which testified by transmission electron microscope, electrical conductivity and rheological property measurements, severally. Specifically, the storage modulus of PLA/CNTs nanocomposites were 3 orders of magnitude higher in contrast to pure PLA. Interestingly, relative to that under regular differential scanning calorimetry (DSC), a double melting peak phenomenon appeared in the high-pressure DSC curves of diverse PLA specimens. Biodegradable PLA/CNTs nanocomposite foam was successfully fabricated with a super-high volume expansion ratio (VER) of 49.6 times, which could offer a promising strategy for developing other thermoplastic polyester foams with ultra-high VER to obtain some unique functional attributes.

Evaluation of heat release caused by low-temperature oxidation of heavy oil and its SARA fractions under isothermal conditions

During in-situ combusiton, the oils in most of the area before the combustion front encounter low-temperature oxidation (LTO) reactions under relatively isothermal conditions in a long time, and heat release of LTO significantly influences the quality of formed fuel. This work is aimed at examining the heat release of LTO of one Xinjiang heavy oil and its saturates-aromatics-resins-asphaltenes fractions using isothermal high-pressure differential scanning calorimetry tests. Furthermore, the widely-accepted LTO reaction pathways of hydrocarbons are summarized. The results indicated that the Xinjiang heavy oil, aromatics, and resins experienced the increased heat release from 200 to 250 ℃ and from 300 to 350 ℃ due to their elevated oxidation rate, and the decreased heat release from 250 to 300 ℃. Thus, to build a stable combustion of the oil, it is key to overcome the action energy barriers between 250 and 300 ℃.

Research on thermal decomposition characteristics of H foaming agent with different moisture contents

N, N-Dinitroso pentamethylene tetramine, also known as H foaming agent, is a self-reactive chemical substance commonly used in the rubber industry. Decomposition, explosion and combustion may be caused by the presence of fire or high temperature. As a high-risk chemical that is strictly regulated in China, H foaming agent has ever triggered multiple accidents. During the study of the decomposition thermal process of H foaming agent, it was found that the presence of moisture content at different levels had a significant effect on its thermal stability. The thermal characteristics of H foaming agent under different moisture contents was studied through the test means such as adiabatic calorimetry and high-pressure differential scanning calorimetry. Through isothermal calorimetry experiment, it was found that the decomposition of H foaming agent had obvious auto-catalytic characteristics. In the moisture content within the range of 0–40%, with the increase of moisture content, the initial exothermic temperature Tonset of the mixture system of H foaming agent and water decreased, while the time from initial heat release to rapid temperature rise of the reaction system (induction period) was gradually prolonged, and the temperature increment of the reaction system was increased gradually. As the proportion of moisture content in the system increased, the adiabatic temperature rise ΔTad of the mixture system of H foaming agent and water gradually decreased, meanwhile the time to maximum rate under adiabatic condition (TMRad) gradually decreased. The research results have guiding significance for finding the reasonable moisture content of H foaming agent in the drying process and determining the upper temperature limit during storage and transportation.

Acrylate-Based Hybrid Sol-Gel Coating for Corrosion Protection of AA7075-T6 in Aircraft Applications: The Effect of Copolymerization Time.

Pre-hydrolysed/condensed tetraethyl orthosilicate (TEOS) was added to a solution of methyl methacrylate (MMA) and 3-methacryloxypropyltrimethoxysilane (MAPTMS), and then copolymerised for various times to study the influence of the latter on the structure of hybrid sol-gel coatings as corrosion protection of aluminium alloy 7075-T6. The reactions taking place during preparation were characterised using real-time Fourier transform infrared spectroscopy, dynamic light scattering and gel permeation chromatography. The solution characteristics were evaluated, using viscosimetry, followed by measurements of thermal stability determined by thermogravimetric analysis. The optimal temperature for the condensation reaction was determined with the help of high-pressure differential scanning calorimetry. Once deposited on 7075-T6 substrates, the coatings were evaluated using a field emission scanning electron microscope coupled to an energy dispersive spectrometer to determine surface morphology, topography, composition and coating thickness. Corrosion properties were tested in dilute Harrison’s solution (3.5 g/L (NH4)2SO4 and 0.5 g/L NaCl) using electrochemical impedance spectroscopy. The copolymerization of MMA and MAPTMS over 4 h was optimal for obtaining 1.4 µm thick coating with superior barrier protection against corrosion attack (|Z10 mHz| ~ 1 GΩ cm2) during three months of exposure to the corrosive medium.

Kinetic analysis of hydrothermal carbonization using high-pressure differential scanning calorimetry applied to biomass

Assessing kinetic parameters of hydrothermal carbonization still requires several tests and time-consuming analyses, usually relying on few data points. With a view to containing the experimental effort and testing the accuracy of models based on continuum curves, high-pressure differential scanning calorimetry was used for the first time to assess the heat release profile, the overall enthalpy change, and the kinetic parameters of a hydrothermal carbonization process in two substrates: digestate and sludge. The process-related thermal effect was established from the difference between the calorimetric curves for the unreacted samples during a first run and for the reacted samples obtained through a second run. The parameters of a kinetic model built on the Arrhenius reaction were adjusted on the basis of the calorimetric curves, adopting an nth-order and an autocatalytic reaction model. Activation energy values of 139.16 and 161.68 kJ/mol, pre-exponential factors around 2.15 × 1011 and 2.52 × 1014 s−1, reaction orders of about 2.68 and 2.46, and R2 values of 0.86 and 0.94 were obtained for digestate and sludge, respectively. Results were consistent with the available literature. Autocatalysis was negligible for both substrates, so the process could be modeled effectively as a single Arrhenius nth-order reaction with significant loss of precision. Coupled with more traditional approaches, this newly-proposed method may pave the way to describing the set of reactions taking place during hydrothermal carbonization by means of their enthalpy values, improving our knowledge of the process’s chemistry and kinetics.

Producción de bio-hidrógeno con catalizadores metálicos

Many applications, including energy applications, require handling pressurized hydrogen gas. However, an alternative option allows the use of a donor that generates hydrogen in situ (either by transfer and / or catalytic reforming), instead of using molecular hydrogen. Ethanol and formic acid, which are biorefinery streams, were used as donors. The effect of metallic catalysts of Pd and Pt, supported on C, g-Al2O3 and zeolite USY, on the generation of hydrogen was evaluated using different ratios between the active phase and the donor, and different times and temperatures of reaction in a high pressure reactor (up to 1000 psi). The catalysts were characterized by DRX, SEM, FTIR and FRX. At the same time, High-Pressure Differential Scanning Calorimetry (HP DSC) was performed for the most promising systems with a ramp of 10 °C/min. Gas chromatography was used to analyze the production of hydrogen. Findings show that the system that generates more hydrogen, with 88%, is 5% Pd/C over 30% formic acid at 300 °C, 500 rpm and a ratio catalyst mass to donor from 1 to 10 (0.028 m).

Thermal behavior and non-isothermal decomposition reaction kinetics of catalyzed hniw-cmdb propellant

The thermal behavior under pressure of 0.1, 4, and 7 MPa and non-isothermal decomposition reaction kinetics under pressure of 4 and 7 MPa of the composite modified double base propellant containing hexanitrohexaazaisowurtzitane (HNIW-CMDB propellant) was investigated by differential scanning calorimetry (DSC). The results showed that there are two exothermic peaks on DSC curve under 0.1 MPa. The exothermic peak temperature decreases with surroundings pressure increasing. There is only one exothermic peak on every high pressure DSC curve. The exothermic peak temperature under every pressure increases with heating rate increasing. The exothermic decomposition kinetic parameters of the propellant changed while the reaction mechanism function didn’t change when catalyzer was added into propellant or testing surroundings changed. The kinetic equation of exothermic decomposition reaction mechanism under 4 MPa and 7 MPa are Avrami-Erofeev (n=2/3).