High Cloud Point Research Articles

Fuel property evaluation of unique fatty acid methyl esters containing β-hydroxy esters from engineered microorganisms

Unique fatty acid methyl esters (FAME) containing β‑hydroxy esters were produced using an engineered microorganism by glucose fermentation. This study investigated the properties of the unique FAME mixture both neat and in blends with conventional diesel, as well as properties of β‑hydroxy esters. The unique FAME blend contained relatively shorter-chain FAME (average fatty acid chain carbon number 14.6) with 58 % monounsaturated fatty acids and 9 % saturated and monounsaturated β‑hydroxy acid chains. The unique FAME had significantly lower distillation T90 (321 °C versus 352 °C) and higher cetane number (56.7 versus 52) compared to soy biodiesel. Cloud points were within method repeatability. Unexpectedly (because of the lack of methylene-interrupted double bonds), the unique FAME had low oxidation stability (1.5 h) as determined by Rancimat induction period. Stability could be improved through addition of commonly used antioxidants. We speculate that monounsaturated β‑hydroxy FAME may be the source of this instability. Blends with conventional diesel up to 50 vol% showed similar kinematic viscosity (within method repeatability) as blends of conventional FAME. The unique FAME had no effect on distillation T90 even at the 80 % blend level. A 30 vol% blend into conventional diesel had a Rancimat induction period of only 2 h, very nearly the same as the neat unique FAME sample. The addition of antioxidants produced blends of acceptable stability. Based on an assessment of the properties of individual β‑hydroxy FAME molecules, they have higher boiling point, higher cloud point, lower cetane number, and potentially lower storage stability than analogous FAME not having the β‑hydroxy group. Removing them from the fuel product in the production process may result in a biodiesel product with superior properties to what is on the market today.

ReaxFF study of the decarboxylation of methyl palmitate over binary metallic nickel-molybdenum catalysts

ABSTRACT Biodiesel has emerged as a possible replacement for fossil-based fuels, particularly in the transportation industry. Because of its high oxygen content, it has several limitations including high viscosity, pour point and cloud point. Converting biodiesel to hydrocarbons is one method of improving the poor flow properties. In this study, Reactive Force Field (ReaxFF) molecular dynamics was used to study the decarboxylation of methyl palmitate on α-NiMoO4, β-NiMoO4 and Ni3Mo catalysts. The results show that the reactions are faster in the presence of α-NiMoO4 and β-NiMoO4, and the number of stable products, carbon dioxide and ethene was higher than they were without the catalyst. With Ni3Mo catalyst, there is rapid initial formation of CO2 and C2H4 until a maximum is reached followed by a decrease in their quantity. The C2H4 was found to decompose to C2H2 and H2 while CO2 was reduced to CO. All reactions were found to follow first-order kinetics, from which the activation energies (Ea) were determined. The Ea drops from 36.89 kcal/mol for uncatalyzed reaction to 25.66, 19.34 and 11.69 kcal/mol for the α-NiMoO4, β-NiMoO4 and Ni3Mo catalysed reactions, respectively. The Ni3Mo catalysed system’s Ea was also closest to the experimentally reported value of 10.11 kcal/mol [1].

Development of Linagliptin Ultra Fine Solid Supersaturated Bio-SNEDDS Using Triangular Mixture Design for Enhancement of Oral Bioavailability: Impact of P-gp Inhibition

Linagliptin (LIN) is a newly developed dipeptidyl peptidase 4 (DPP-4) inhibitor oral antidiabetic drug. LIN is considered a P-gp substrate, thus suffers from poor bioavailability (< 30%). The aim of this study was to develop and characterize LIN bioactive self-nanoemulsifying drug delivery system to circumvent its poor bioavailability and enhance its therapeutic efficacy.
 Methodology: In this study, we developed solid supersaturated bioactive self-nanoemulsifying drug delivery system (Ss-bio-SNEDDS) of LIN, using clove oil as an oil phase, cremophor CO 40 as a surfactant, labrasol as a co-surfactant and Hydroxy-propyl-B-cyclodextrin (HPBCD) as a precipitation inhibitor (PI); all components are of established P-gp inhibition activity. Optimization was performed by means of triangular mixture design based on particle size, poly dispersity index (PDI) and percent transmittance. The two optimized formulations (F4 and F8) were designated and evaluated for stability and cloud point. Also, the effect of pH on particle size and PDI was assessed. Additionally, examination of particles’ surface morphology of the two optimized formulations was performed by transmission electron microscope (TEM). The prepared liquid supersaturated-SNEDDS (s-SNEDDS) were converted into solid supersaturated-SNEDDS (Ss-SNEDDS) via adsorption on microcrystalline cellulose (MCC). Further evaluations were carried out, including in vitro drug release, in vitro precipitation and in vivo studies.
 Results: The optimized formulations F4 and F8 manifested promising characteristics concerning particle size (< 50 nm), PDI (< 0.3) and percent transmittance (> 99%). Stability study showed no phase separation or precipitation with rapid emulsification time. The two optimized formulations showed high cloud point temperature (above 70°C). TEM images of F4 and F8 showed spheroid like appearance with relatively smooth surface. Results of the in vivo study in rats revealed a significant increase in AUC of solid-F4, solid-F8 and solid supersaturated-F4 (S-F4, S-F8 and Ss-F4) by 2.32, 2.89 and 2.54 folds, respectively compared to LIN solution; with a noticeable reduction in blood glucose level at each point.
 Conclusion: In a nutshell, Ss-bio-SNEDDS are considered as auspicious nano-carriers for LIN with the virtue of augmented bioavailability and possible dose reduction.

Amide-decorated carbon dots as sensitive and selective probes for fluorescence enhancement detection of cadmium ion

As highly toxic metal ions, cadmium ions (Cd2+) are prevalent in varying concentrations around the world. The establishment of an accurate and effective method for Cd2+ determination with high sensitivity and selectivity is of particular concern. The present work fabricated a fluorescence chemosensor for the detection of Cd2+ based on functionalized carbon dots (CDs), which were hydrothermally prepared using amidated hyperbranched-polyethyleneimine (HPEI). As investigated by FTIR, NMR, and XPS, the stably grafted amide groups endowed the CDs with thermosensitivity and high cloud point due to the change in hydrophilic-hydrophobic behaviors. The CDs chemosensor with optimal amidation degree exhibited high sensitivity, selectivity, and stability in the determination of Cd2+ from various water environments. Notably, the fluorescence intensity enhanced with the increase of Cd2+ concentration, originating from the improved structure rigidity caused by the interactions between grafted amides and Cd2+. These impressive features made the CDs not only sensitive to detecting Cd2+ in low-concentration solutions with a limit of detection of 3.41 nM (the lowest known value for Cd2+ detection) but also accurate for the quantification in high-concentration solutions with a detectable Cd2+ concentration of 6.0 × 10−2 M. Owing to the broad detection range, the CDs developed in present work show great potential applications in various scenarios.

Development and Evaluation of Self-Emulsifying Drug-Delivery System-Based Tablets for Simvastatin, a BCS Class II Drug.

Self-emulsifying drug-delivery systems (SEDDSs) are designed to improve the oral bioavailability of poorly water-soluble drugs. This study aimed at formulating and characterization of SEDDS-based tablets for simvastatin using castor and olive oils as solvents and Tween 60 as surfactant. The liquids were adsorbed on microcrystalline cellulose, and all developed formulations were compressed using 10.5 mm shallow concave round punches. The resulting tablets were evaluated for different quality-control parameters at pre- and postcompression levels. Simvastatin showed better solubility in a mixture of oils and Tween 60 (10:1). All the developed formulations showed lower self-emulsification time (˂200 seconds) and higher cloud point (˃60°C). They were free of physical defects and had drug content within the acceptable range (98.5%-101%). The crushing strength of all formulations was in the range of 58-96 N, and the results of the friability test were within the range of USP (≤1). Disintegration time was within the official limits (NMT 15 min), and complete drug release was achieved within 30 min. Using commonly available excipients and machinery, SEDDS-based tablets with better dissolution profile and bioavailability can be prepared by direct compression. These S-SEDDSs could be a better alternative to conventional tablets of simvastatin.

Fuel properties of low-erucic acid pennycress (LEAP) oil biodiesel

Biodiesel is a renewable biobased fuel obtained from transesterification of plant seed oil with methanol. This fuel has physical properties that make it attractive as an alternative fuel for compression-ignition (diesel) engines. In the United States (US), there is a need to increase the production of sustainable and environmentally friendly biofuels, including biodiesel, to supplement fossil fuels. To meet these challenges, emphasis is being placed on expanding the use of low-cost non-food oils as feedstocks for biodiesel. Low-erucic acid pennycress (LEAP) was developed from field pennycress as a cover crop for use in the Upper Midwestern US. The objective of the present study was to convert LEAP oil to biodiesel (fatty acid methyl esters [FAME]) and evaluate its fuel properties. The same process was applied to FAME made from natural field pennycress (FPC) oil as a baseline for comparison of results. The LEAP oil-FAME (LEAP-ME) had a kinematic viscosity at 40 °C (KV40) that was lower than that of FPC oil-FAME (FPC-ME), and nearly equivalent to the KV40 of soybean oil-FAME (SME). The total saturated-FAME (SFAME) concentration of LEAP-ME (5.40 mass%) was greater than that of FPC-ME. Since SFAME have high melting points, this caused LEAP-ME to have a higher cloud point (CP) than FPC-ME. However, the CP of LEAP-ME (−6.8 °C) was lower than those of canola oil-FAME (CaME; −2.5 °C) and SME (−2.8 °C). The oxidative induction period at 110 °C (IP110) of LEAP-ME was poor (0.83 h), indicating that it would need to be treated with antioxidants before distribution as an alternative diesel fuel.

Safety Study on Wax Deposition in Crude Oil Pipeline

The Shunbei crude oil pipeline is prepared to use the unheated transportation process to transport waxy crudes. However, the wax formation in the pipeline is unknown. In order to predict the wax deposition of the pipeline, the physical property experiment of Shunbei crude oil was carried out through field sampling. The density, freezing point, hydrocarbon composition, and viscosity–temperature characteristics of crude oil are obtained. The cloud point and wax precipitation characteristics of the crude oil were obtained using the differential scanning calorimetry (DSC) thermal analysis method. Then, the wax deposition rate of the pipeline was predicted by two methods: OLGA software and wax deposition kinetic model. Finally, the optimal pigging cycle of the pipeline was calculated on this basis. The results show that: Shunbei crude oil is a light crude oil with low wax content, a low freezing point, and a high cloud point. Comparing the OLGA simulation results with the calculation results of the Huang Qiyu model, the development trend of wax deposition along the pipeline was the same under different working conditions. The relative error of the maximum wax layer thickness was 6%, proving that it is feasible for OLGA to simulate wax deposition in long-distance crude oil pipelines. Affected by the wax precipitation characteristics of Shunbei crude oil, there was a peak of wax precipitation between the pipeline section where crude oil temperature was 9.31–13.31 °C and the recommended pigging cycle at the lowest throughput was 34 days in winter and 51 days in spring and autumn.

Effect of dicationic ionic liquids on cloud points of tergitol surfactant and the formation of aqueous micellar two-phase systems

A cloud point evaluation was performed for the nonionic surfactant Tergitol 15-S-7 in aqueous solutions of McIlvaine buffer (pH 7.0). Cloud point temperatures of the selected nonionic surfactant were studied in relation to the effect that the addition of dicationic ionic liquids (ILs) had on the systems. The dicationic ILs with different alkyl spacer lengths were derived from 1, n-bis(3-methylimidazolium-1-yl)alkane bromide ([BisAlk(MIM)2][2Br]) — in which Alk = But, Hex, Oct, and Dec. The dicationic ILs with longer alkyl spacer chains (Alk ≥ 6) led to an increase in the Tergitol’s cloud point values, due to their ability to fold their structures in solution, which increase the interactions of ILs with tergitol in the mixed micelles. This increase was even more pronounced when the concentration of the dicationic ILs was increased. Furthermore, the addition of dicationic ILs increased the micelles size; however, the hydrodynamic diameter of mixed micelles did not depend on the length of the ILs’ alkyl spacer chains. The Tergitol/IL systems with lower critical micellar concentration values will result in higher cloud point values, due to the greater colloidal dispersion stability.

Rapid synergistic cloud point extraction for simultaneous determination of five polar phenols in environmental water samples via high performance liquid chromatography with fluorescence detection

A novel method was established for preconcentration and determination of the following five polar phenolic compounds: phenol, o-, m-, and p-cresol and 2,4-dimethylphenol. After separating and enriching the analytes by rapid synergistic cloud point extraction (RS-CPE), high performance liquid chromatography (HPLC) was carried out, and the components in surfactant-rich phase supernatant were detected fluorometrically. N-Pentanol, an alcohol with high polarity and rapid cloud point reduction effect, was used as the synergistic reagent, and the straight chain non-ionic surfactant Tergitol 15-S-7 was selected as the extractant. The pH, surfactant, salt concentration, revulsant and synergistic reagent were optimized. Under the optimum conditions, the correlation coefficients among target substances were all>0.998. The relative standard deviation range was 1.7%–5.0%, and the detection limit range was 0.061–0.166 μg/L. The proposed method is simple, economical, highly efficient and sensitive. It was successfully applied to the extraction and determination of polar phenolic compounds in environmental water samples, and the recoveries ranged from 85.6% to 108%.

Improved hepatoprotective activity of Beta vulgaris L. leaf extract loaded self-nanoemulsifying drug delivery system (SNEDDS): in vitro and in vivo evaluation

Objective Beta vulgaris L. (beetroot) is a vegetable plant rich in phytochemical compounds such as phenolic acids, carotenoids and flavonoids. The objective of the current study is the development and optimization of self-nanoemulsifying drug delivery systems (SNEDDSs) to enhance the hepatoprotective activity of beet leaf (BL) extract. Methods Total flavonoids content was estimated in the BL extract and its solubility was evaluated in various vehicles to select proper component combinations. Pseudo-ternary phase diagrams were constructed employing olive, linseed, castor and sesame oils (oil phase), Tween® 20 (Tw20) and Tween® 80 (Tw80) (surfactants (SAs)) as well as dimethyl sulfoxide (DMSO) and propylene glycol (PG) (co-surfactants (Co-SAs)). Optimization of formulations from the phase diagrams took place through testing their thermodynamic stability, dispersibility and robustness to dilution. Results Four optimized BL-SNEDDS formulations, comprising linseed oil or olive oil, Tw80 and DMSO at two SA/Co-SA ratios (2:1 or 3:1) were chosen. They exhibited high cloud point and percentage transmittance values with spherical morphology of mean droplet sizes ranging from 14.67 to 16.06 nm and monodisperse distribution with negatively charged zeta potential < −9.51 mV. The in vitro release profiles of the optimized formulations in pH 1.2 and 6.8 were nearly similar, with a non-Fickian release mechanism. In vivo evaluation of BL-SNEDDSs hepatoprotective activity in a thioacetamide-induced hepatotoxicity rat model depicted promoted liver functions, inflammatory markers and histopathological findings, most prominently in the group treated by F7. Conclusion The results indicate that SNEDDS, as a nanocarrier system, has potential to improve the hepatoprotective activity of the BL extract.

High Cloud Point Polyvinylaminals as Non-Amide-Based Kinetic Gas Hydrate Inhibitors

In recent years, we have explored non-amide-based classes of kinetic hydrate inhibitor (KHI) polymers to determine if the same level of performance can be achieved as commercial KHI polymers, which...

Vinyl lactam-based copolymers and terpolymers as high cloud point kinetic hydrate inhibitors in methane-THF-water system

A series of vinyl lactam-based polymers were synthesized and then evaluated as kinetic hydrate inhibitors (KHIs) in methane-tetrahydrofuran (THF)-water system. The inhibition performance of synthesized KHIs was examined and compared with commercially-available KHIs using a high-pressure rocking cell. The VCap/1-vinyl-2-pyrrolidone (VP) copolymer with a molar ratio of 3:1 could reduce hydrate growth rate by 18% greater than poly(N-vinylcaprolactam) (PVCap). Moreover, the modification of this copolymer with 3-mercaptopropionic acid (3-MPA) led to producing the novel KHI that more effectively decreased hydrate growth rate than non-modified copolymer. Moreover, the addition of 2-Dimethylaminoethyl methacrylate (DMAEMA) as a third monomer to the polymerization mixture improved the performance of the copolymers by 20%. Cloud point measurements revealed that all the synthesized copolymers, the modified copolymers and the terpolymers had higher cloud point in comparison with PVCap, such that cloud point temperature (Tcl) for mercaptoacetic acid (MAA)-modified copolymer and 3-mercaptopropionic acid (3-MPA)-modified copolymer was 43 and 20 °C higher than that of PVCap and these modified copolymers could be developed as novel high cloud point kinetic hydrate inhibitors even in saline solutions.

Extraction of polyunsaturated fatty acids to reduce the iodine number of biodiesel products

In the last ten years, Indonesia has succeeded in realizing the production and commercialization of oxygenated biofuel/bioethanol and bioethanol, even has applied mixing biodiesel into diesel to up to 20%-volume (or known as a B20 mixture). This success has at least helped reduce imports of fuel oil (BBM) such as diesel and gasoline, but no more than 20%. The rest (i.e., at least 80%) must still be imported and will cause severe pressure on the country’s balance of payments because the current volume of fuel imports is no less than 50% of domestic needs. The quality of Indonesian biodiesel products generally still has a high cloud point and low oxidation stability. Diesel engine fuel consists of a mixture of methyl ester fatty acids (FAME: Fatty Acids Methyl Ester). Many constituent components are limited or not large (consist of 7-14 carbons). The essential constituents are the methyl esters of lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acids. Methyl esters of polyunsaturated fatty acids (linoleic, linolenic, eleostearic) are inferior because they have a low cetane number and low oxidative stability. While methyl esters of saturated fatty acids have a superior demonic rate but have a high melting point (bad, higher than the requirements given by SNI). Related to the amount of unsaturated fat in biodiesel, it can reduce the quality of biodiesel, such as acid numbers, moisture content, and the emergence of sludge. Based on the current condition of biodiesel quality, to improve the quality of biodiesel produced can be done by reducing the number of unsaturated fats present in the biodiesel product. The initial step that has to be done is separation biodiesel products into saturated biodiesel with the characteristic iodine number <30-40 and unsaturated biodiesel with an iodine number > 70 through a fractionation process. Extraction was carried out using AgNO3 with variations in the ratio of biodiesel feed to solvents. The best ratio of biodiesel:AgNO3 to eliminate the levels of polyunsaturated free fatty acids in biodiesel products is 1:2 with an iodine value of 47.38 gr I2/(100 gr oil)

Sulfonated chitosan as green and high cloud point kinetic methane hydrate and corrosion inhibitor: Experimental and theoretical studies

In this work sulfonated chitosan (SCS) was introduced as a promising green kinetic methane hydrate and corrosion inhibitor to overcome the incompatibility problem between inhibitors. Evaluation of hydrate inhibition performance of SCS with high-pressure autoclave and micro-differential scanning calorimeter revealed that hydrate formation was delayed 14.3 ± 0.2 times and amount of hydrate formed was decreased to 30 % compared to water. The weight loss experiments showed that SCS provides corrosion inhibition efficiency of 95.6 ± 0.1 at 5000 ppm concentration. SCS is able to increase polarization resistance and decrease corrosion current density according to electrochemical measurements. Study of surface morphology by SEM-EDX and profilometer showed that SCSs suppress corrosion rate and reduce the surface roughness of carbon steel. Quantum chemical study confirmed that the pendant groups caused by chitosan modification interact with carbon steel surface. The findings of this research can provide new opportunities to develop biodegradable materials as KHIs/CIs for flow assurance in oil and gas pipelines.

Utilization of &lt;i&gt;Moringa oleifera&lt;/i&gt; oil for biodiesel production: A systematic review

A major energy challenge currently is the depletion of global oil reserves which is gradually resulting in the decline of conventional diesel production. Several alternative fuels and renewable energy sources have been proffered with biodiesel constituting a promising option. Biodiesel has garnered increasing attention because it is renewable, biodegradable, non-toxic, and it is characterized by low carbon monoxide particulate and hydrocarbon emissions compared to the conventional diesel. In recent times, several scientific writings have documented the utilization of Moringa oleifera as feed stock for biodiesel production. Moringa oleifera (horseradish) is a multipurpose tree species and one of the most widely cultivated crops in tropical and sub-tropical areas of the globe. Databases used for this review include Google Scholar, Scopus, WorldCat.org, Microsoft Academic and Science Direct. A total of 216 articles were retrieved and 18 studies were ultimately retained after qualitative analysis. The analytic output shows the seed oil has favorable characteristics for use as biodiesel. The fatty acid composition of the oil makes it suitable for both edible and non-edible applications. Also, the percentage of oleic acid (70%) in Moringa oil is quite high compared to other crops which possess about 40% oleic acid. Moringa seed oil exhibit a high oxidative stability and its thermal stability exceeds other oil crops like sunflower oil, soybean oil amongst others. Biodiesel produced from M. oleifera seed oil exhibit enhanced oxidative ability, high cloud point and a higher cetane number of approximately 67 than for most biodiesels. Moringa oleifera biodiesel can be stored for a long period of time and it is safe for transport.

Improving the Properties of Pure Vegetable Oils to Use Directly in Diesel Engines

Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel). biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel. In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles). diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils. The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines. Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study. Characteristics of the viscosity, density and the surface tension versus fuel temperature are established. Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.

Improving the Properties of Pure Vegetable Oils to Use Directly in Diesel Engines

Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel). biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel. In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles). diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils. The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines. Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study. Characteristics of the viscosity, density and the surface tension versus fuel temperature are established. Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.

Optical investigation of mixing-controlled combustion using a novel transgenic plant oil

Fuels derived from plant oils hold promise as alternatives to petroleum-derived fuels due to their renewable production strategies, and potential to reduce net carbon emissions. Due to their high viscosity and cloud point, and low volatility however, direct use of plant oils in engines, without transesterification, poses a challenge. Recently, genetic modification has been used to alter plant lipid biosynthesis, producing novel oils that may overcome some of these challenges. In this study, 3-acetyl-1, 2-diacyl-sn-glycerol (Ac-TAG), extracted from a strain of transgenic Camelina Sativa, was studied in an optically-accessible diesel engine. Simultaneous high-speed shadowgraphy and OH* chemiluminescence imaging data were collected to obtain measurements of jet development, liquid penetration, ignition location, and flame liftoff length. A conventional diesel fuel and untransformed neat camelina oil were run at the same conditions as the Ac-TAG fuel for comparison. Even though the Ac-TAG fuel had significantly lower viscosity than the neat camelina oil, no significant differences were observed between Ac-TAG and neat camelina oil in any of the quantities studied. Relative to diesel, the biofuels had greater liquid penetration, shorter liftoff lengths and ignition delay, and consistently ignited farther upstream.

Systematic Study of Polyglyoxylamides as Powerful, High-Cloud-Point Kinetic Hydrate Inhibitors

A series of polyglyoxylamides (PGAms) have been synthesized and investigated for performance as kinetic hydrate inhibitors (KHIs) in slow constant cooling high-pressure rocking cell experiments using a structure II-forming synthetic natural gas mixture at 76 bar initial pressure. We found that the KHI performance improved as the size of the alkyl pendant group was increased. The best performing PGAm, poly(pyrrolidinyl glyoxylamide) (PPyGAm-I), gave an onset temperature of 8.2 °C at 2500 ppm. The KHI performance was improved by increasing the polymer concentration or by adding the high-flash-point solvent n-butyl glycol ether (nBGE) as a synergist. For example, using 7500 ppm of PPyGAm-I, the onset temperature was lowered to 3.8 °C (giving a subcooling of 15.7 °C, compensating for the drop in pressure at To). A mixture of 2500 ppm PPyGAm-I and 7500 ppm nBGE gave an onset temperature of 5.1 °C. Combined with a high cloud point (TCl = 79 °C), this makes PPyGAm-I a strong candidate for potential industrial us...

Hexafluoroisopropanol/Brij-35 based supramolecular solvent for liquid-phase microextraction of parabens in different matrix samples

A novel supramolecular solvent (SUPRAS) based on hexafluoroisopropanol (HFIP)/Brij-35 was proposed for liquid-phase microextraction (LPME) of parabens in water samples, pharmaceuticals and personal care products. Brij-35 is a cost-effective and non-toxic non-ionic surfactant, but it has a high cloud point (>100 °C). HFIP, with the features of strong hydrogen-bond donor, high density and powerful hydrophobicity, was used as the cloud point-reducing agent and self-assembling and density-regulating solvent of Brij-35. Upon adding HFIP into the Brij-35 aqueous solution, the cloud point of Brij-35 was decreased to below room temperature, and the SUPRAS was formed in the bottom over a wide range of HFIP and Brij-35 concentrations at room temperature. The SUPRAS was composed of Brij-35, HFIP and water, having a density larger than water, and it showed a large spherical structure of positive micellar aggregates (2–8 μm). The HFIP/ Brij-35 SUPRAS-based LPME procedure was non-thermodependent and could be performed at room temperature with centrifugation using normal centrifuge tubes, being very simple. In the extraction of six parabens, the HFIP/ Brij-35 SUPRAS-based LPME method showed short extraction time (3.3 min), low solvent consumption (0.3 mL), and large enrichment factor (26–193). The method of HFIP/ Brij-35 SUPRAS-based LPME with HPLC-DAD gave good linearity for the quantification of parabens with correlation coefficients larger than 0.9990. The limits of detection based on a signal-to-noise ratio of 3 were from 0.042 to 0.167 μg L−1. The recoveries for the spiked real samples were in the range of 90.2–112.4% with relative standard deviation less than 8.9%. Except for tap water, one or several paraben (s) were detected in all the other real samples.