Light Hydrocarbon Mixtures Research Articles

Application of functionalized carbon nanofibers as a modifying additive to motor oil

Due to the widespread of lubricants, improving their tribological characteristics remains an important practical task. Among the promising modifying additives, carbon nanomaterials attract special attention. Such materials are found to improve the antifriction characteristics of lubricants and oils. In the present research, carbon nanofibers were synthesized via catalytic pyrolysis of a mixture of light hydrocarbons (C2-C4) over the NiCu catalyst. In order to form functional groups on the surface of carbon nanofibers, they were treated with diluted acids HCl, HNO3, and H2SO4 as well as with concentrated HNO3. The functionalized samples were comprehensively characterized by a set of physicochemical methods including atomic absorption spectroscopy, scanning and transmission electron microscopies, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, temperature-programmed desorption/oxidation, and Raman spectroscopy. As defined, the surface oxygen concentration in the samples varies from 3.5 to 16.3 at.%. It was shown that the addition of modified carbon nanofibers to a motor oil leads to an improvement in its tribological characteristics. In particular, the most effective additive was the sample treated with diluted HNO3. The motor oil with this modifying additive exhibited the heating temperature decreased by 10 °C and the contact spot area on the stationary body decreased by 20 %.

Direct Ethylene Purification from Cracking Gas via a Metal–Organic Framework Through Pore Geometry Fitting

The direct one-step separation of polymer-grade C2H4 from complex light hydrocarbon mixtures has high industrial significance but is very challenging. Herein, an ethylene-adsorption-weakening strategy is applied for precise regulation of the pore geometry of four tailor-made metal–organic frameworks (MOFs) with pillar-layered structures, dubbed TYUT-10/11/12/13. Based on its pore geometry design and functional group regulation, TYUT-12 exhibits exceptional selective adsorption selectivity toward C3H8, C3H6, C2H6, C2H2, and CO2 over C2H4; its C2H6/C2H4 adsorption selectivity reaches 4.56, surpassing the record value of 4.4 by Fe2(O2)(dobdc) (dobdc4− = 2,5-dioxido-1,4-benzenedicarboxylate). The weak π–π stacking binding affinity toward C2H4 in TYUT-12 is clearly demonstrated through a combination of neutron powder diffraction measurements and theoretical calculations. Breakthrough experiments demonstrate that C2H4 can be directly obtained from binary, ternary, quaternary, and six-component light hydrocarbon mixtures with over 99.95% purity.

METHODS FOR INCREASING THE CONDENSATE RECOVERY COEFFICIENT WHEN DEVELOPING GAS CONDENSATE FIELDS

This article will discuss methods for increasing the condensate recovery coefficient and the concept of condensate recovery. Gas condensate is a cold hydrocarbon reservoir that includes natural gas as well as liquid hydrocarbons, often in the form of liquid condensate. During reservoir extraction, liquids are mixed from mixtures of light hydrocarbons (eg methane, ethane, propane) and denser liquid hydrocarbons (known as condensates). Gas condensates are found in underground reservoirs, where temperature and pressure conditions allow the gas to condense into liquid form as it moves from the formation to the surface. Such situations are often observed in tanks where there is a combination of increased pressure, high temperatures and a specific gas composition. The condensate production indicator from the reservoir describes the level of gas condensate extraction from gas condensate and oil and gas condensate fields. A distinction is made between instantaneous condensate production (determined at a certain point in time) and final production (at the end of commercial exploitation of the field). To quantify condensate production, the condensate production indicator is used - this is the ratio between the given definition of condensate and the reserves taken from the reserves of the field based on its study (expressed as a percentage or fraction of units). This indicator is used to extract recoverable condensate reserves. In addition, it is taken into account when developing a project for a gas condensate or oil and gas condensate field, taking into account the efficiency of the technology used. The completeness of condensate removal in some cases determines the reasonableness of developing the selected system. The main features of the behavior of gas condensate systems are associated with the corresponding phenomena reflected in the phase diagrams of reverse condensation and evaporation. These features lead to the fact that when the pressure in the gas condensate system decreases to a level below the saturation pressure, condensation of heavier hydrocarbons (condensate) occurs. If the pressure in the gas condensate formation during development is maintained at the initial level (or the pressure at the beginning of condensation), then phase transitions occur only in the formation zones adjacent to the well. This requires taking into account changes over time, such as changes in filtration characteristics in the bottomhole zones of wells. When developing a gas condensate field to the point of depletion, condensate begins to fall out everywhere in the reservoir. However, the condensate that falls often has little effect on the gas saturation coefficient of the entire formation. Consequently, when developing a gas condensate field until depletion (with a low condensate content in the gas), filtration flows can be considered as single-phase, since the precipitated condensate remains motionless. Low condensate saturation of the formation leads to slight changes in its capacitive and filtration characteristics. In the zone of the bottomhole space of the formation, two-phase filtration occurs. Keywords: gas, gas condensate, heavier hydrocarbons, dew point, the condensate recovery coefficient.

Pore chemistry and geometry control in a metal azolate framework for one-step ethylene purification from quinary gas mixture

In the petrochemical industry, obtaining polymer-grade ethylene from complex light-hydrocarbon mixtures by one-step separation is important and challenging. Here, we successfully prepared the Metal–Azolate Framework 7 (MAF-7) with pore chemistry and geometry control to realize the one-step separation of ethylene from cracking gas with up to quinary gas mixtures (propane/propylene/ethane/ethylene/acetylene). Based on the tailor-made pore environment, MAF-7 exhibited better selective adsorption of propane, propylene, ethane and acetylene than ethylene, and the adsorption ratios of ethane/ethylene and propylene/ethylene are as high as 1.49 and 2.81, respectively. The pore geometry design of MAF-7 leads to the unique weak binding affinity and adsorption site for ethylene molecules, which is clearly proved by Grand Canonical Monte Carlo theoretical calculations. The breakthrough experiments show that ethylene can be directly obtained from binary, ternary, and quinary gas mixtures. These comprehensive properties show that MAF-7 is expected to achieve one-step purification of ethylene in complex light hydrocarbon mixtures.

A new correlation to calculate the viscosity of binary mixtures of heavy or extra-heavy crude oil and light hydrocarbons using the Arrhenius-Lederer equation

Heavy crude oils are commonly mixed with lighter crude oils to reduce heavy oil viscosity and to ensure the flow through the pipeline system. Viscosity, as is well known, is a crucial property for designing and sizing offshore and onshore facilities for producing and transporting crude oil. When not available experimentally, the viscosity of mixed crudes can be obtained from theoretical approaches such as the Arrhenius-Lederer equation depending only on bulk properties (density and viscosity) of mixture components, and an adjustable parameter (α), which allows calculations to match experimental data. This work presents a new correlation for calculating the rescaled parameter proposed by Lederer for the Arrhenius equation to determine the viscosity mixtures of heavy and light hydrocarbons. The proposed correlation was developed considering experimental data of binary mixtures of paraffinic hydrocarbons, diesel, and heavy oil over a wide range of temperature conditions (from 293 to 343 K), fluid density ratios (from 1.014 to 1.40), and viscosity ratios (1.3 to 311,000). For viscous fluids, which exhibited non-Newtonian behavior, viscosity on the first Newtonian region is considered. The correlation was tested to predict the viscosity of biodiesel-diesel, heavy crude oil-diesel, bitumen-heptane, and eicosane-decane binary mixtures from 308 to 448 K and pressures up to 10 MPa. Finally, for assessing the predictive capabilities of the new correlation, the viscosity of several mixtures was estimated. The first consisted of mixtures formed by three oils at different compositions, whereas the last consisted of a recombined live oil and supercritical CO2. Predicted viscosities are in better agreement with experimental data than those estimated from Shu’s correlation. The total mean absolute percentage error was 6.66 and 19.32 for the proposed and the Shu correlation, respectively.

CO2 Decomposition in Microwave Discharge Created in Liquid Hydrocarbon

The task of CO2 decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO2 is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H2, C2H2, C2H4, CH4, CO2, and CO. No oxygen was found in the products. The mechanisms of CO2 decomposition in the discharge are considered. The formation of H2 occurs simultaneously with the decomposition of CO2 in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

Kinetic modeling of the steam reforming of light hydrocarbon mixture from waste resources: Effects of gas composition on hydrogen production

Steam reforming of a light hydrocarbon mixture, which might be produced during the pyrolysis of waste resources, was experimentally conducted over a commercial Ni-based catalyst. Two different gas compositions were considered as simulated gases to utilize waste resources, and kinetic data were generated at a variety of temperatures, space velocities, and steam-to-carbon ratios to develop a kinetic model by fitting the experimental data. Experimental observations indicated that the inclusion of higher chains resulted in low methane conversion compared to those of the other chains, and the model demonstrated that the increased hydrogen production rate by higher chains enhanced methanation, resulting in a decreased methane conversion. The increased fraction of higher chains decreased the steam-to-carbon ratio for methane, resulting in a decreased methane conversion. Further analysis showed that despite the decrease in methane fraction, hydrogen production could be increased by 4% with a 10% methane fraction in the light hydrocarbon mixture, indicating that the direct reforming of a light hydrocarbon mixture from waste resources with no pre-reforming might be feasible.

CO2-Selective Capture from Light Hydrocarbon Mixtures by Metal-Organic Frameworks: A Review

CO2 represents a typical impurity in light hydrocarbon feedstocks, which affects the quality of subsequent chemical products. Owing to their highly similar nature, industrial separation requires large amounts of energy. Adsorptive gas separation based on porous materials is considered an efficient alternative, as it can offer faster kinetics, higher selectivity, long-term stability and more energy-efficient regeneration. For the adsorption separation method, preferential CO2 capture from gas mixtures in one step is more energy-efficient for direct purification than light hydrocarbons, saving about 40% energy by eliminating energy-intensive post-regeneration processes such as countercurrent vacuum blowdown. Therefore, CO2-selective adsorbents are more sought-after than light hydrocarbon-selective adsorbents. Metal-organic frameworks (MOFs) have been demonstrated as outstanding physisorbents for CO2 capture due to their configurable channels for CO2 recognition, structural flexibility and large specific surface area. Many highly selective CO2 adsorption behaviors of MOFs have been reportedly achieved by precise modulation of pore size, pore chemistry or structural flexibility. In this review, we discuss the emerging development of MOFs for CO2-selective capture from different light hydrocarbon mixtures. The challenges of CO2 recognition and the strategies employed to achieve CO2 selectivity over light hydrocarbon mixtures by MOFs are summarized. In addition, the current challenges and prospects in the field of MOFs for CO2 capture are discussed and elaborated.

超微孔碳吸附剂实现天然气中丙烷和乙烷的高选择性提取

The separation of light hydrocarbon mixtures and the extraction of C3H8 and C2H6 from natural gas are of significant importance in natural gas purification and upgrading. Microporous carbon adsorbents are promising in light hydrocarbon separation. However, the fabrication of uniform ultramicropores to boost separation selectivity remains challenging. Herein, we fabricated a series of poly(vinylidene chloride)-resin-derived ultramicroporous carbon adsorbents with a relatively uniform pore size (5.2–5.3 Å) by activator-free pyrolysis. The optimal C-PVDC-800 exhibited record-high ideal adsorption solution theory (IAST) selectivity for C3H8/CH4 (3387) and C2H6/CH4 (75) and Henry’s selectivity for C3H8/CH4 (369) among all reported adsorbents under ambient conditions, combined with ultrahigh uptake of C3H8 (3.9 mmol g−1, 0.05 bar) and C2H6 (2.67 mmol g−1, 0.10 bar) at low partial pressures and 298 K. More importantly, fast gas adsorption kinetics favorable for fixed-bed adsorption applications was realized. Breakthrough experiments and cycling tests further confirm the superb separation performance of the extraction of C3H8 and C2H6 from natural gas.

Efficient Utilization of Hydrocarbon Mixture to Produce Aromatics over Zn/ZSM-5 and Physically Mixed with ZSM-5

A mixture of saturated and unsaturated light hydrocarbon was used as feed gas for the production of aromatics. Natural gas liquids (NGL) from gas fields and hydrocarbon molecules obtained in the middle of conversion processes could be considered a kind of light hydrocarbon mixture. Therefore, for the conversion of the mixture into aromatics compounds, Zn-impregnated ZSM-5 catalysts were prepared and evaluated by employing different loading of Zn. In addition, the catalytic performance was tested and compared by charging physically mixed two different kinds of catalysts in the bed. The NH3-TPD result showed that the impregnation of Zn led to an increase in the number of medium-strength acid sites, whereas those of weak and strong acid sites were decreased. From the results of the catalytic activity tests, 0.5Zn/ZSM-5 showed the highest aromatics yield. As the amount of Zn loading was further increased to 1 wt.%, the yield of aromatics decreased. The test result in the case of the physically mixed catalysts showed a slightly lower yield in terms of total aromatics, but showed the highest BTX yield. To reveal the relative contribution of each hydrocarbon conversion to aromatics yield, each C2 compound was separately tested for aromatization over Zn/ZSM-5.

Expanded Reactor Engineering Calculations for the Oxidative Coupling of Methane

The catalytic activation of CH4 by limited amounts of O2 produces a mixture of synthesis gas (CO, H2) and light hydrocarbons (C2Hx), the relative amounts of each depending on catalyst type and process conditions. Using an elementary reaction mechanism for the oxidative coupling of methane (OCM) on a La2O3/CeO2 catalyst derived from the literature, this study replaces the activating O2 with moist H2O2 vapor to reduce synthesis gas production while improving C2Hx yields and selectivities. As the H2O2 content of the activating oxidant rises, more of the CH4 conversion occurs in the gas phase instead of with the catalytic surface. In a packed bed reactor (PBR), the use of H2O2 allows the PBR “light-off” to occur using a lower feed temperature. In exchange for a small decline in CH4 conversion, C2Hx selectivity increases while synthesis gas production drops. In a continuous stirred tank reactor (CSTR), H2O2 improves C2Hx over synthesis gas across a wider range of feed temperatures than is possible with the PBR. This suggests the CSTR will likely reduce OCM preheating requirements.

Designed synthesis of porous carbons for the separation of light hydrocarbons

The separation of light hydrocarbon mixtures (C1–C3) generated from petrochemical industry is vital and challenging process for obtaining valuable pure chemical feedstocks. In comparison to the energy intensive conventional separation technologies (cryogenic distillation, absorption and hydrogenation), the adsorptive separation is considered as a low energy cost and high efficiency process. Porous carbons have been demonstrated as excellent adsorbents for the separation of light hydrocarbons, owing to their designable structure and tailorable properties. This review summarizes the recent advances of using porous carbons as adsorbents for the separation of light hydrocarbons, including methane/nitrogen, methane/alkane, methane/carbon dioxide, ethylene/ethane and propylene/propane. We discuss the separation mechanisms and highlight the material features including pore structure, surface chemistry and target molecular properties that determine the separation performance. Furthermore, the challenges and development direction associated with carbonaceous adsorbents for light hydrocarbon separation are discussed, meanwhile the guidelines for the design of porous carbons are proposed.

An improved Wilson equation for phase equilibrium K values estimation

Abstract Phase equilibrium K values are either estimated with empirical correlations or rigorously calculated based on fugacity values determined from an equation of state. There have been several empirical analytical equations such as Raoult’s Law, the Hoffman Equations (Hoffman A, Crump J, Hocott C. Equilibrium constants for a gas condensate system. J Petrol Technol 1953;5:1–10) and their modifications and the well-known Wilson Equation (Wilson G. A modified Redlich–Kwong equation of state applicable to general physical data calculations. In: AIChE National Meeting Paper15C, May 4–7, Cleveland, OH; 1969). along with several modifications. This work presents a new modification of the Wilson Equation for estimating phase equilibrium K values, predominantly for light hydrocarbon mixtures. The modification is based on correlating a subset of a database of K values, established from convergence pressure data. Results show the method to accurately correlate and predict the K value data, within 10% on average. Moreover, the predicted K factors provide remarkable results for such a simple model when used in a variety of phase equilibrium calculations. The results also show that the new model compares favorably with existing empirical analytical methods. Such a model would provide excellent initial estimates for rigorous thermodynamic calculations.

Rational Tuning of Ultramicropore Dimensions in MOF-74 for Size-Selective Separation of Light Hydrocarbons

The separation of light hydrocarbon mixtures is one of the most important yet energy-intensive processes in the petrochemical industry. Solid adsorbent materials could potentially not only lower energy costs but also offer higher efficiency as an alternative means to traditionally energy-intensive separation methods such as distillation, absorption, and extraction. Here, rational augmentation of the metal–organic framework, Mg-MOF-74, was designed in silico to enhance kinetic selectivity of the material, while imposing a minimal reduction in the adsorption working capacities for light hydrocarbons. From the computer-aided design, we synthesized 2,4,6-tri(4-pyridyl)-1,3,5-triazine-inserted Mg-MOF-74 (tpt-Mg-MOF-74) and successfully characterized the structure. This material can kinetically separate ethane/propane with an unprecedented diffusive selectivity of ∼49 owing to its distinctive pore size and provides evidence that metal–organic framework need not sacrifice pore volume for enhanced kinetic selectivity in separation applications.

Light emission from microwave discharges in liquid hydrocarbons at the initial stages of their development

AbstractTime‐resolved optical techniques (spectrograph, high‐speed camera, photodiode) were used for scrutinizing the initial stages of the microwave discharge (2.45 GHz, 200–500 W) achieved in liquid alkanes (CnH2n + 2). Petroleum solvent Nefras S2 80/120 (a mixture of light hydrocarbons with boiling temperatures ranging between 33°C and 205°C) was considered to be representative of alkanes. The discharge was ignited in the liquid, at the end of a molybdenum antenna located under ambient conditions above the liquid. The discharge displaced sequences of light pulses of different shapes and amplitudes, randomly distributed in time. The minimum pulse duration is 0.5 ms. At times close to 1 ms, the spectrum comprises emission bands of the C2 molecule, lines of hydrogen, and the C+ ion, but there is no continuum associated with the emission of the formed solid carbon‐containing particles. In a number of cases, an anomalous spectrum of the C2 molecule was recorded, with no such sequences having been observed before.

Sequestration of light hydrocarbons in Ionic Liquids at high-pressures: Consistency and thermodynamic modeling

Ionic liquids are applicable in the recovery of valuable products, remotion of polluting agents, and used in many CO2-capture techniques. In this work, high-pressure vapor-liquid equilibria of twenty-one binary mixtures of light hydrocarbons + IL has been modelled with Peng-Robinson/Stryjek-Vera equation of state applying Wong-Sandler mixing rules and van Laar model for the gamma-phi approach and Perturbed Chain-Statistical Associating Fluid Theory equation of state for the phi-phi approach. Critical properties were determined using a group contribution method. Adjustable characteristic pure component parameters were obtained using predicted vapor pressures and saturated liquids densities values. Experimental data, obtained from literature, were subjected to thermodynamic consistency area test. For the thermodynamic modelling, adjustable parameters were fitted between predicted and experimental bubble pressure. Van Laar and interaction parameters were regarded as temperature-dependent. Results obtained for both models, in terms of the main deviations between experimental and calculated pressures, were reasonably satisfactory.

Metal-Organic Framework Materials for Light Hydrocarbon Separation.

In practical industrial applications, the separation of light hydrocarbon mixtures is a very important technology. In recent years, some progress has been made in metal-organic framework materials for light hydrocarbon separation, but further research is still needed. This Minireivew presents a systematic discussion on the latest developments and separation mechanisms of metal-organic framework materials for C2 and C3 mixtures, discusses the problems faced by metal-organic framework materials in the study of light hydrocarbon adsorption and separation, and provides a reference for the design, preparation and process development of low-carbon hydrocarbon adsorption and separation materials in the future.

Oil and gas seepage offshore Georgia (Black Sea) – Geochemical evidences for a paleogene-neogene hydrocarbon source rock

Numerous hydrocarbon seep sites at the continental shelf, slope, and in the deep water basin are known to feed the Black Sea water reservoir of dissolved methane. In this study, we identified the likely sources of gas and oil that are emitted at four sites located on the continental slope offshore Georgia in the Eastern Black Sea at 830 to 1,140 m water depth – an area with gas seepage only (Batumi seep area) and three areas of coupled gas and oil seepage (Iberia Mound, Colkheti Seep, and Pechori Mound). The geochemistry of bulk parameters, organic fractions and individual hydrocarbon biomarkers in near-surface sediments and of gas/oil expelled from the seafloor was analyzed and jointly interpreted to assign most likely hydrocarbon source rocks in the studied region. Presence of oleanane in shallow oil-impregnated sediments and oil slicks attests that the source rock at all sites is younger than Mid Cretaceous in age. We conclude that hydrocarbons ascending at all the four seepage areas originate from the Eocene Kuma Formation and/or the Oligocene–Lower Miocene Maikop Group, which are considered the principal hydrocarbon sources in the Eastern Black Sea region. Distributions of crude oil biomarkers in shallow sediments suggests moderate to heavy biodegradation. C1/C2+ ratios (10–4,163) along with stable C and H isotopic ratios (δ13C–CH4 ‒46.3 to −53.1.3‰ V-PDB; δ2H–CH4 ‒159 to −178‰ V-SMOW) indicate gas mixtures of oil-associated thermogenic and secondary microbial light hydrocarbons that are discharged from the four seep sites. Light hydrocarbons discharged at the Batumi Seep area are characterized by significant enrichments of methane, but have almost similar δ13C–CH4 values if compared to the other study sites. Such methane enrichments likely result from a comparably higher degree of petroleum degradation and associated formation of secondary microbial methane.

Maximization of the power production in LNG cold energy recovery plant via genetic algorithm

This paper presents an optimization model via genetic algorithm (GA) to maximize the power generation potential of a liquefied natural gas (LNG) cold energy recovery plant. LNG releases a large amount of cold energy during vaporization prior to transport for service, and this cold energy can be effectively utilized to generate power using a heat engine. We performed a thermodynamic analysis for a power generation system combining the organic rankine cycle (ORC) driven by LNG exergy and the direct expansion cycle. Both LNG and the working fluid in the combined ORC are light hydrocarbon mixtures, and their physical properties were estimated using the Peng-Robinson equation. We conducted a thorough investigation of the effects that the working fluid composition brought about on the thermal efficiency of the heat engine through an analysis using Aspen HYSYS interfaced with a GA-based Matlab solver. The results showed that optimization of the working fluid composition led to an increase of 58.4% in the performance of the combined ORC in terms of the net work.

High-Throughput Computational Screening of Metal–Organic Frameworks for the Separation of Methane from Ethane and Propane

Efficient separation of mixtures of light hydrocarbons is an industrially demanding but challenging process. In this study, we present a high-throughput computational screening of ∼12,000 experimen...