Supercritical Propane Research Articles

Solubility of Sulfur in Supercritical Propane–Butane Mixture

Solubility of Sulfur in Supercritical Propane–Butane Mixture

Energy efficient method of supercritical extraction of oil from oil shale

The only method currently used for producing oil from oil shale is high temperature retorting, which is wasteful of energy and gives oil with a high content of heavy oil. The novel method of extraction used in this study, involving supercritical propane with tetrahydrofuran as a co-solvent, solves the problem of the high cost of producing oil by conventional high temperature retorting. El-Lajjun oil shale from Jordan was used to evaluate the reaction yield and the characteristics of the product. At supercritical propane temperature and pressure (100 °C and 4.3 MPa), the yield was high and comparable to that for the conventional retorting method (>350 °C). As the temperature increased to 200 °C, the oil yield increased with pressure. The oil obtained was high in aliphatic hydrocarbons but with significant amounts of ethers, some carbonyls and sulfur-oxygen compounds. Hydrodeoxygenation and hydrodesulfurization of the produced oils using NiMo-Al-SBA-15 catalysts significantly enhanced the quality of the oil by decreasing the oxygen and sulfur contents and increasing the aliphatic and diesel fractions.This work leads to an enduring breakthrough technology that substantially reduces costs, waste, energy and the environmental impact of using oil shale as a raw material for liquid fuel production using Green Technology. Recovery of THF is high (>95%) and re-use of THF and propane would be essential for commercial application.

Accurate prediction of thermal conductivity of supercritical propane using LSSVM

ABSTRACT Recently supercritical fluids have found impressive applications in different industries. According to this, researchers have been interested to study thermophysical properties of supercritical fluids. Due to high price and time consuming process of experiments related to supercritical condition, the attention to computational study were increased. In present contribution, a new LSSVM-GA model were proposed to estimate the thermal conductivity of supercritical propane. The thermal conductivity data were extracted from open literature. By Applying LSSVM-GA on 380 data points and finding optimum parameters, the estimated values of thermal conductivity of supercritical propane were compared with experimental data and it was confirmed that the predictive modeling performed in acceptable manner based on reported errors and fitting parameters. Consequently, the model is reliable that can be utilized to forecast the thermal conductivity of supercritical propane.

Thickening compressed liquid and supercritical propane with bisurea DMHUT N,N'-(4-methyl-1,3-phenylene)bis[N-(1,5-dimethylhexyl)urea] for enhanced oil recovery or waterless hydraulic fracturing

N,N'-(4-Methyl-1,3-phenylene)bis[N-(1,5-dimethylhexyl)urea] or DMHUT, a low molecular weight bisurea with branched alkyl substituents, is capable of thickening high-pressure propane, which could lead to improvements in its performance during miscible enhanced oil recovery and waterless hydraulic fracturing. DMHUT dissolves in supercritical propane upon heating to 115 °C at high pressure (34.5 MPa). Upon cooling to temperatures as low as 25 °C the solution remains a transparent, stable, single phase that exhibits remarkably high viscosity. For example, at a mass fraction of 0.5 wt% at 40 °C and 34.5 MPa, falling ball viscometry indicates that the bisurea-propane solution is more than 400 times as viscous than pure propane. The thickening efficiency of DMHUT has been found to be superior under most conditions to other small associative molecules and polymers known to thicken propane: tributyltin fluoride, hydroxyaluminum di(2-ethylhexanoate), ultra-high molecular weight poly α-olefin, or conventional crosslinked phosphate esters based on long-chain alkyl-substituted phosphate esters.

On the phase and structural variability of directly injected propane at spark ignition engine conditions

This paper presents an experimental and theoretical examination of directly injected (DI) propane at a wide range of conditions relevant to spark ignition engines. The investigated conditions comprise the injection of sub- and supercritical propane, with the latter representing a plausible, operational extreme during engine heat soak.Optical imaging is first used to study a wide range of observed spray behaviors, highlighting the sensitivity of DI propane to the engine operating condition. These varying behaviors then prompt further consideration of the thermodynamics involved. This extends thermodynamic arguments recently proposed by the authors in another work, and is able to explain when supercritical injection contains the liquid phase, when shock structures appear and when the spray collapses. Spray regime diagrams are then proposed in order to generalize the observed behaviors. These diagrams reveal several, often overlapping regimes that demarcate choked and unchoked injection, collapsed and multi-plume sprays, and the appearance or disappearance of the liquid phase immediately outside of the injector.

Densities and Phase Equilibria of Hydrogen, Propane, and Vegetable Oil Mixtures: Experimental Data and Thermodynamic Modeling

Heterogeneous catalytic gas–liquid reactions are intensified when carried out in the homogeneous fluid phase by means of a supercritical cosolvent. For instance, supercritical propane is used to enhance the yield in hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data on the reactive mixture H2 + sunflower oil + propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK–PR equations of state, respectively. The isochoric method provides not only PvT information under the reaction conditions but also the reactive system compressibility, which is a key variable to attain enhanced transport properties in supercritical reactors.

On the Fuel Spray Transition to Dense Fluid Mixing at Reciprocating Engine Conditions

This paper presents a theoretical and experimental study of direct fuel injection at conditions relevant to spark ignition (SI) and compression ignition (CI) engines. The focus of this work is to identify the conditions under which fuel droplet formation should occur or be suppressed. An experimental investigation of the injection of sub- and supercritical propane into gaseous nitrogen is first discussed. This includes study of one case in which the fuel remained supercritical with respect to temperature and pressure throughout the injection event, and which appears to be the first time that truly supercritical hydrocarbon fuel injection is examined experimentally. A nondimensional parameter τ representing the ratio of the time scales of droplet formation and droplet evaporation is also proposed and used to explain the observed occurrence or suppression of fuel droplets at different conditions. While instants of τ < 1 suggest that droplets should always be observed in any plausible SI or CI engine design, τ > 1 also occurs during the bulk delivery of heavier hydrocarbons in CI engines. In such cases, this should justify simplified modeling of the spray as a dense fluid that mixes with its surroundings, ignoring droplet transport during the less important parts of the injection event.

Phase equilibria of methyl esters in supercritical propane

High pressure phase equilibria measurements using a static synthetic view cell for methyl decanoate, methyl dodecanoate, methyl hexadecanoate, methyl octadecaonate and methyl docosanoate in supercritical propane were conducted between 376.6 and 412.4K at methyl ester mass fractions between 0.0178 and 0.660. The data show a linear increase in phase transition pressure with an increase in temperature at constant composition and, within the experimental range, total solubility was achieved below 8.1MPa for all systems. Comparing the various data sets, an increase in phase transition pressure with increasing hydrocarbon backbone is noted, indicating that propane is able to fractionate a mixture of methyl esters.

Architectural Effects on the Solution Behavior of Linear and Star Polymers in Propane at High Pressures

A star polymer with a divinylbenzene core and statistically random methacrylate copolymer arms is synthesized with reversible addition–fragmentation–transfer method and fractionated with supercritical carbon dioxide and propane to obtain fractions with low molecular weight polydispersity. The phase behavior and density behavior are experimentally determined in supercritical propane for fractionated star polymers and the corresponding linear copolymer arms at temperatures to 423 K and pressures to 210 MPa. Experimental data are presented on the impact of the number of arms, the backbone composition of the lauryl and methyl methacrylate repeat units in the copolymer arms, and the divinylbenzene core on the polymer–propane solution behavior. The star polymer is significantly more soluble because of its unique structure compared with the solubility of the linear copolymer arms in propane. The resultant phase behavior for the two homopolymers and the copolymer arms in propane are modeled using the perturbed ch...

SBA-15 grafted with 3-aminopropyl triethoxysilane in supercritical propane for CO2 capture

Supercritical propane (SC-propane) was found to be a promising solvent for grafting (3-aminopropyl)triethoxysilane (APS) onto synthesized SBA-15 for CO2 capture. The influence of operating conditions in SC-propane for CO2 adsorption at different pressures (8.3–13.8MPa), temperatures (85–120°C), and periods of time (4–16h) were evaluated. The CO2 adsorption conditions under different partial pressures, temperatures and moisture were evaluated. The results showed a reduction in pore characteristics and an increased amount of grafted APS with increasing pressure and temperature after grafting. After grafting in SC-propane at 11.0MPa and various temperatures for 16h, a 3–20% increase in the amount of grafted APS and a 6–49% increase in the CO2 adsorption capacity over the toluene refluxing was observed. The time required for grafting in SC-propane could be reduced while maintaining higher nitrogen content and CO2 adsorption capacity compared with grafting in toluene refluxing.

CO2 Capture by Mesoporous SBA-15 Grafted with 3- Aminopropyl Triethoxysilane in Supercritical Propane

Supercritical propane (SC-propane) was found to be an appropriate solvent to graft 3-aminopropyl triethoxysilane (APS) onto our own synthesized SBA-15 for CO2 capture. SC-propane grafting provides several advantages, including non-toxicity, low cost, less reaction time, and usability under wide ranges of pressure and temperature over toluene. Besides, SC-propane can be completely removed when pressure is released after grafting. In this study, the grafting in propane was carried out at the selected pressure and temperature. The grafting in SC-propane exhibited an improvement for amount of the grafted APS and CO2 adsorption capacity over those using the conventional toluene refluxing method.

Minimizing Costs in Near-Critical Bioethanol Extraction and Dehydration Processes

In the present work, we propose a model-based cost optimization for three capacities of bioethanol extraction–dehydration plants with supercritical propane. We consider alternative integration schemes between process streams as different nonlinear programming problems (NLP) for energy minimization. In particular, we analyze integration between a heat pump option for the top vapor of the first distillation column with the beer column reboiler, which can provide reduction in total energy consumption, as well as lower final product cost. Capital and operating costs were evaluated for the analyzed schemes. Thermodynamic predictions are performed with an upgraded group contribution with association equation of state (GCA-EOS). We demonstrate that ethanol dehydration with supercritical propane can be a sustainable alternative that is energetically and economically competitive with other technologies.

Measurement and Modeling of the Solubility of Tetramethylthiuram Disulfide and 2-Nitrophenyl Disulfide in Compressed Propane

The solubility of tetramethylthiuram disulfide (TTDS) and 2-nitrophenyl disulfide (NPDS) in sub- and supercritical propane has been experimentally determined in a static view cell, for temperatures between (347 and 393) K and pressures in the range (4.8 to 12.9) MPa. The solubilities of TTDS varied from (0.09 to 0.67) mg of solute per gram of propane, whereas those of NPDS were from (0.06 to 0.70) mg of solute per gram of propane within the experimental range studied. It was found that larger values of the solubility were obtained at higher pressures. Regarding the temperature effect, for NPDS the solubility rose with increasing values of the variable in the whole experimental range analyzed, while for TTDS higher solubilities were found at 370 K (the critical temperature of propane). The solubility values obtained for these compounds were compared to those of anthracene, carbazole, and dibenzothiophene (DBT) in propane. It was observed that TTDS and NPDS solubilities are similar to those of carbazole and...

Simulation and Analysis of an Ethylene Slurry Polymerization System Using Supercritical Propane

In this paper, a model for an ethylene slurry polymerization system using supercritical propane as a solvent is developed by adopting a set of thermodynamic and kinetic parameters using fundamental chemical engineering principles and Polymers Plus software. The Ziegler–Natta catalyst is characterized by assuming the existence of multiple types of catalyst sites and deconvolution data from gel permeation chromatography to determine the most probable chain-length distribution and relative amounts of polymer produced at each site type. A set of suitable reaction subclasses and kinetic constants for different site types that fit plant conditions is developed, validating our model. The values calculated for production rate, ethylene conversion, residence time, H2/C2H4 molar ratio in the reactor, number-average molecular weight, and polydispersity index are all close to actual values, verifying that our model accurately describes plant conditions.

Solubility of Dibenzothiophene in Sub- and Supercritical Propane

The solubility of dibenzothiophene (DBT) in sub- and supercritical propane has been measured using a static view cell at pressures from (2.7 to 8.0) MPa and temperatures from (298 to 405) K. The values of the mole fraction of DBT varied from 1.3·10−3 to 4.8·10−2 over the experimental range studied. These values are 2 orders of magnitude higher than those reported in the literature for DBT in CO2 at similar values of reduced pressure and temperature, which is indicative of the excellent solvent properties of propane for the extraction of polyaromatic compounds, compared to CO2. On the other hand, when comparing the solubility of DBT in propane to that of other polyaromatic hydrocarbons (PAHs), it is found that DBT solubility (sulfur PAH) is at least 1 order of magnitude larger than that of anthracene, which in turn is 1 order of magnitude larger than that of carbazole (nitrogen PAH). These results can be mainly attributed to the effect of the vapor pressure of the solutes and, to a lesser extent, to their ...

Changes in the chlorophyll and carotenoid content and composition of ground thyme leaves as a function of supercritical carbon dioxide and subcritical propane extraction

This work was conducted to study the changes in the content and composition of chlorophylls and carotenoids in ground thyme leaves as a function of supercritical carbon dioxide and sub-critical propane extraction. the results indicated that the maximum oleoresin yield could be obtained with supercritical carbon dioxide at 400 bar and 35 or 55 °C and sub-critical propane at 50 bar. Pigment solvating capacity of supercritical carbon dioxide increased with the increase of extraction pressure. Substantial variation was noticed in pigment composition between raw material, oleoresin and residues (powders after extraction). Chlorophyll b, chlorophyll a and the Mg-free derivatives were the dominant pigments in the raw material with other derivatives being minor constituents. After extraction with supercritical carbon dioxide at 35 °C and pressures higher than 200 bar, epimerisation and oxidation of chlorophylls lead to marked accumulation of artefacts in the residues. The content of oxidized chlorophylls was incr...

Phase Equilibria of Long-Chain Carboxylic Acids in Supercritical Propane

This paper presents data on the phase behavior of long-chain acids (octanoic acid, decanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, and docosanoic acid) in supercritical propan...

Separation of alkanes and alcohols with supercritical fluids. Part I: Phase equilibria and viability study

The chemical conversion of detergent range alkanes (12–14 carbon atoms) to alcohols is often incomplete and results in a large amount of residual alkane. This paper shows that these alkanes and alcohols can be separated by supercritical fluids. Ethane, propane and carbon dioxide were selected as possible supercritical solvents while n-tetradecane and 1-dodecanol were selected to represent the alkane–alcohol mixture, as these would be the two most difficult compounds to separate in a C12 to C14 alkane–alcohol mixture. A phase behaviour study and relative solubility analysis revealed that both ethane and carbon dioxide show promise in separating n-tetradecane and 1-dodecanol. Propane was eliminated as possible solvent because the phase behaviour of n-tetradecane and 1-dodecanol in supercritical propane is too similar. A pilot plant study showed that both supercritical ethane and carbon dioxide can be used to separate n-tetradecane and 1-dodecanol, with indications that supercritical ethane may affect a superior separation. An economic analysis, considering the energy requirements, revealed that the most important parameter with regard to energy consumption is the solvent-to-feed ratio. The process utilising ethane is more energy intensive, yet the energy requirements for both processes compare well with other petrochemical separation processes using supercritical fluids. Further investigations with both ethane and carbon dioxide should be conducted to determine which of these two solvents are superior and to optimise the operating parameters.

Measurement and Modeling of the Solubility of 9H-Carbazole in Sub- and Supercritical Propane

The solubility of 9H-carbazole in sub- and supercritical propane has been measured using a static view cell at pressures from (4.3 to 10.0) MPa and temperatures from (323 to 405) K. The mole fraction of 9H-carbazole varied from 4·10−5 to 4·10−4 over the experimental range studied. The solubility of 9H-carbazole in propane is 1 order of magnitude higher than that of 9H-carbazole in CO2 for similar values of the reduced pressure and temperature, which highlights the excellent solvent properties of propane relative to CO2 for the extraction of polyaromatic compounds. The experimental solubility data were correlated with the Peng−Robinson equation of state using six different sets of mixing rules for the estimation of the mixture parameters aM and bM. Good fits of the experimental results were obtained for all of the mixing rules tested, especially for those involving two adjustable parameters; the absolute average percentage deviation (AAPD) was 16.4 % for the best fit. In addition, the empirical equation of...

Branched polyethylenes fractionated in supercritical propane

A series of polyethylenes (PEs), were synthesized in the presence of a palladium catalyst containing bulky diimine ligands (VERSIPOL™) yielding amorphous PEs. The different PE samples were characterized by Size Exclusion Chromatography (SEC) with on line light scattering, NMR, viscometry or small angle neutron scattering (SANS) techniques to assess the molar mass, molar mass distribution (MMD), radius of gyration (or hydrodynamic radius) and degree of branching. Selected PE samples were fractionated in supercritical propane by isothermal increasing the pressure profile. In most cases, PE fractions with a sharper MMD than the original PEs were obtained. The average absolute molar masses of the resulting fractions increased steadily with increasing extraction pressure. Their dilute solution properties were compared with those of unfractionated PEs. Structural analyses confirmed the homogeneity of the degree of branching within a raw PE sample.