Two dimensional Zn-stilbenedicarboxylic acid (SDC) metal-organic frameworks for cyclic carbonate synthesis from CO<Subscript>2</Subscript> and epoxides

A two-dimensional Zn-based metal-organic framework has been synthesized by using Zn(II) ions and H₂SDC (4,4′-stilbenedicarboxylic acid) under solvothermal conditions. The framework having a trinuclear Zn₃-(RCO₂)₆ SBUs connected by the 4,4′-stilbenedicarboxylic acid to form a hexagonal network, shows a two-dimensional structure and displays high thermal stability up to approximately 330 °C. The role of Zn²⁺ (from Zn-SDC) for epoxide activation and Br-ion (from TBABr) for ring opening of epoxide was studied for the cycloaddition reaction of CO₂ and propylene oxide (PO) under ambient conditions. Zn-SDC was found catalytically efficient towards CO₂-epoxide coupling under ambient reaction conditions with high selectivity towards the desired cyclic carbonates under solvent-free conditions. The effects of various reaction parameters such as catalyst loading, temperature, CO₂ pressure, and time were evaluated. Zn-SDC was easily separable and reusable at least five times without any considerable loss in the initial activity. A plausible reaction mechanism for the cycloaddition reaction was also proposed based on literature and experimental inferences.     

Conversion of oils to monoglycerides by glycerolysis in supercritical carbon dioxide media

Glycerolysis of soybean oil was conducted in a supercritical carbon dioxide (SC-CO₂) atmosphere to produce monoglycerides (MG) in a stirred autoclave at 150–250°C, over a pressure range of 20.7–62.1 MPa, at glycerol/oil molar ratios between 15–25, and water concentrations of 0–8% (wt% of glycerol). MG, di-, triglyceride, and free fatty acid (FFA) composition of the reaction mixture as a function of time was analyzed by supercritical fluid chromatography. Glycerolysis did not occur at 150°C but proceeded to a limited extent at 200°C within 4 h reaction time; however, it did proceed rapidly at 250°C. At 250°C, MG formation decreased significantly (P<0.05) with pressure and increased with glycerol/oil ratio and water concentration. A maximum MG content of 49.2% was achieved at 250°C, 20.7 MPa, a glycerol/oil ratio of 25 and 4% water after 4 h. These conditions also resulted in the formation of 14% FFA. Conversions of other oils (peanut, corn, canola, and cottonseed) were also attempted. Soybean and cottonseed oil yielded the highest and lowest conversion to MG, respectively. Conducting this industrially important reaction in SC-CO₂ atmosphere offered numerous advantages, compared to conventional alkalicatalyzed glycerolysis, including elimination of the alkali catalyst, production of a lighter color and less odor, and ease of separation of the CO₂ from the reaction products.     

Zirconium-based isoreticular metal-organic frameworks for CO<Subscript>2</Subscript> fixation via cyclic carbonate synthesis

Two highly stable isoreticular metal-organic frameworks comprising chains of zirconium coordinated with linkers of 1,4-H₂BDC (1,4-benzenedicarboxylic acid) and 4,4′-H₂BPDC (4,4′-biphenyldicarboxylic acid), denoted as MIL-140A and MIL-140C, were synthesized. The catalytic activity of these frameworks was studied for the coupling reaction of CO₂ and epoxides to produce cyclic carbonates under solvent-free conditions. Excellent activity was observed for both catalysts: they yielded high epoxide conversion with >99% selectivity toward the cyclic carbonate, and were fully reusable even after four cycles without any considerable loss of initial activity. The enhancement in the catalytic activity was explained based on acidity/basicity studies. The influence of various reaction parameters such as catalyst amount, reaction time, reaction temperature, and CO₂ pressure was also investigated. Reaction mechanism was proposed on the basis of experimental evidence and our previous DFT (density functional theory) studies.     

CO2-facilitated transport membranes prepared by blending polyvinyl alcohol and various water-absorbing agents

This study describes the production of a membrane by blending polyvinyl alcohol (PVA) and water-absorbing agents for the selective permeation of CO₂ by optimizing the type of water-absorbing agent and its ratio to PVA. A CO₂-facilitated transport membrane is prepared by adding an aqueous cesium carbonate solution to a coated polymer blend matrix. When sodium polyacrylate (PAANa) is blended with PVA as a water-absorbing agent, the resulting membrane shows promising heat and pressure resistances and a relatively high CO₂/He separation performance. Particularly, the CO₂/He selectivity of the membrane composed of PVA, PAANa, and another water-absorbing agent exceeds 400 under a total pressure of 0.1 MPa and a CO₂ partial pressure of 0.08 MPa at 85°C. Moreover, the CO₂/He selectivity is approximately 100 even under a total pressure of 0.7 MPa and a CO₂ partial pressure of 0.56 MPa. Thus, a high-performance CO₂ separation membrane at 85°C is produced.     

Lipase-catalyzed hydrolysis of canola oil in supercritical carbon dioxide

The effect of pressure, temperature, and CO₂ flow rale on the extent of conversion and the product composition in the enzyme-catalyzed hydrolysis of canola oil in supercritical carbon dioxide (SCCO₂) was investigated using lipase from Mucor miehei immobilized on macroporous anionic resin (Lipozyme IM). Reactions were carried out in a continuous flow reactor at 10, 24, and 38 MPa and 35 and 55°C. Supercritical fluid chromatography was used to analyze the reaction products. A conversion of 63–67% (triglyceride disappearance) was obtained at 24–38 MPa. Mono-and diglyceride production was minimum at 10 MPa and 35°C. Monoglyceride production was favored at 24 MPa. The amount of product obtained was higher at 24–38 MPa due to enhanced solubility in SCCO₂. Complete hydrolysis of oil should be possible by increasing the enzyme load and/or decreasing the quantity of the oil substrate. There was a drop in triglyceride conversion over a 24-h reaction time at 38 MPa and 55°C, which may be an indication of loss of enzyme activity. Pressure, temperature, and CO₂ flow rate are important parameters to be optimized in the enzyme-catalyzed hydrolysis of canola oil in SCCO₂ to maximize its conversion to high-value products.     

Experimental and modeling studies on the solubility of sub‐ and supercritical carbon dioxide (scCO2) in potato starch and derivatives

The solubility of CO₂ in native potato starch (NPS) and potato starch acetate (SA) at two different temperatures (50°C and 120°C) and various pressures (up to 25 MPa) was determined using a magnetic suspension balance. Within the experimental window, a maximum solubility of 31 mg CO₂/g_sample for NPS and 79.4 mg CO₂/g_sample for SA was obtained. The CO₂ sorption behavior is highly depending on the temperature and pressure. The solubility data were modeled with the Sanchez Lacombe equation of state (S‐L EOS). The swelling (S_w) values, as predicted using the S‐L EOS, were relatively small and a maximum value of 6.1% was obtained for SA at 25 MPa and 120°C. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Effect of gas permeation temperature and annealing procedure on the performance of binary and ternary mixed matrix membranes of polyethersulfone,SAPO‐34, and 2‐hydroxy 5‐methyl aniline

This study investigated the effect of annealing time and temperature on gas separation performance of mixed matrix membranes (MMMs) prepared from polyethersulfone (PES), SAPO‐34, and 2‐hydroxy 5‐methyl aniline (HMA). A postannealing period at 120°C for a week extensively increased the reproducibility and stability of MMMs, but for pure PES membranes no post‐annealing was necessary for stable and reproducible performance. The effect of operation temperature was also investigated. The permeabilities of H₂, CO₂, and CH₄ increased with increasing permeation temperature from 35°C to 120°C, yet CO₂/CH₄ and H₂/CH₄ selectivities decreased. PES/SAPO‐34/HMA ternary and PES/SAPO‐34 binary MMMs exhibited the highest ideal selectivity and permeability values at all temperatures, respectively. For H₂/CO₂ pair, when temperature increased from 35°C to 120°C, selectivity increased from 3.2 to 4.6 and H₂ permeability increased from 8 to 26.5 Barrer for ternary MMM, demonstrating the advantage of using this membrane at high temperatures. The activation energies were in the order of CH₄ > H₂ > CO₂ for all membranes. PES/SAPO‐34/HMA membrane had activation energies higher than that of PES/SAPO‐34 membrane, suggesting that HMA acts as a compatibilizer between the two phases. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40679.     

Effects of preparation parameters on CO2/N2 gas permselectivity of polyether thin film composite membrane

In this work, ether oxide (EO)-based multilayer composite membranes were prepared via interfacial polymerization (IP) of trimesoyl chloride (TMC) and polyetheramine (PEA) on polydimethylsiloxane precoated polysulfone support membrane. The effects of preparation parameters, such as monomer concentrations, reaction time, and heat-treatment temperature on the membrane performance were investigated. The optimal preparation parameters have been concluded. The results showed the increasing monomers concentration of both PEA and TMC can lead to the decrease of CO₂ permeance and increase of CO₂/N₂ selectivity. The optimal monomers concentration was found. When monomer concentrations are higher than the optimal values, the CO₂ permeance decreases continually while CO₂/N₂ selectivity only shows a very limited improvement with the further increase of monomers concentration. The reaction time has similar effects on membrane performance as the monomers concentration. The effect of heat-treatment temperature was also studied. With the increasing heat-treatment temperature, the CO₂ permeance shows a decrease tendency, while the CO₂/N₂ selectivity shows a maximum at 80 °C. When PEA is 0.013 mol L⁻¹, TMC is 0.020 mol L⁻¹, reaction time is 3 min, and heat-treatment temperature is 80 °C, the optimum preparation conditions are achieved with CO₂ permeance of 378.3 gas permeation unit (GPU) and CO₂/N₂ selectivity of 51.7 at 0.03 MPa. This work may help to design and fabricate gas separation membranes with desired performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47755.     

Isothiocyanate derivatives of soybean oil triglycerides: Synthesis,characterization, and polymerization with polyols and polyamines

In this article, a novel two step synthesis of soy oil based isothiocyanate is described. Allylicaly brominated soybean oil (ABSO) was reacted first with ammonium thiocyanate in tetrahydro furan to form allylic thiocyanates. These compounds were then converted to isothiocyanated soybean oil (ITSO) by a thermal rearrangement. Conversion was found to be 70%. The structure of the ITSO was characterized by IR and ¹ H‐NMR techniques. Then ITSO was reacted with ethylene glycol, glycerol, and castor oil to produce polythiourethanes and ethylene diamine and triethylene tetra amine to produce polythioureas. Thermal properties of the products were determined by DSC and TGA techniques. DSC traces showed T_g's for ethylene glycol polythiourethane at ?39 and 58°C, for glycerol polythiourethane at ?39 and 126°C, for castor oil polythiourethane at ?38°C and ?17°C, for ethylene diamine polythiourea at ?45°C, and for triethylene tetra amine poly thiourea at ?39°C. Additionally, DSC analysis of polythioureas showed an endotherm at around 100°C. All of the polymers started to decompose around 200°C. Tensile properties of the polymers were determined. Polythiourethanes showed higher tensile strength and lower elongation when compared with their urea analogs. Stress at break values of the polymers were 1.2 MPa for glycerol polythiourethane, 0.6 MPa for ethylene glycol polythiourethane, 0.5 MPa for ethylene diamine polythiourea, and 0.9 MPa for triethylene tetra amine polythiourea polymers. Unfortunately, polymers synthesized showed poor solvent resistance. All polymers swelled and disintegrated in CH₂Cl₂ in 5 h. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Direct Conversion of Glycerol into 1,3-Propanediol over Cu-H4SiW12O40/SiO2 in Vapor Phase

Using a SiO₂ supported copper and H₄SiW₁₂O₄₀ catalyst, it is demonstrated that glycerol can be directly converted to 1,3-Propanediol (1,3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent. The formation of 1,3-PD is proved to proceed through the designed reaction pathway: (step 1) dehydration of glycerol to 3-hydroxypropanal on acid site of supported H₄SiW₁₂O₄₀ (step 2) hydrogenation of 3-hydroxypropanal on supported copper metal. The effect of temperature, weight hourly space velocity, pressure, and initial water content was investigated to obtain the optimum conditions. The glycerol conversion and products distribution greatly depended on these factors. Both the 1,3-PD and 1,2-Propanediol selectivity improved with increasing hydrogen pressure. At 210 °C, 0.54 MPa and 83.4% conversion, the selectivity of 1,3-PD was up to 32.1%, together with a 22.2% selectivity of 1,2-Propanediol. The cyclic acetal, an important kind of byproducts, was identified by Gas Chromatogram–Mass Spectrometer (GC–MS).     

Ni/NaX: A Bifunctional Efficient Catalyst for Selective Hydrogenolysis of Glycerol

Non-noble metal Ni/NaX catalyst was prepared and used in the hydrogenolysis of aqueous glycerol. Characterization by XRD, SAED, H₂ chemisorption, ICP and NH₃-TPD techniques disclosed that the proper strong acid sites were responsible for the high activity and selectivity. Over Ni/NaX catalyst, conversion of glycerol reached 86.6% with 94.6% selectivity to glycols including 1,2-proplyene glycol and ethylene glycol under 6.0 MPa H₂ pressure at 200 °C after 10 h reaction. Additionally, the effects of time, temperature, and H₂ pressure were investigated in detail.     

Deacidification of black cumin seed oil by selective supercritical carbon dioxide extraction

The deacidification of high-acidity oils from Black cumin seeds (Nigella sativa) was investigated with supercritical carbon dioxide at two temperatures (40 and 60°C), pressures (15 and 20 MPa) and polarities (pure CO₂ and CO₂/10% MeOH). For pure CO₂ at a relatively low pressure (15 MPa) and relatively high temperature (60°C), the deacidification of a highacidity (37.7 wt% free fatty acid) oil to a low-acidity (7.8 wt% free fatty acid) oil was achieved. The free fatty acids were quantitatively (90 wt%) extracted from the oil and left the majority (77 wt%) of the valuable neutral oils in the seed to be recovered at a later stage by using a higher extraction pressure. By reducing the extraction temperature to 40°C, increasing the extraction pressure to 20 MPa, or increasing the polarity of the supercritical fluid via the addition of a methanol modifier, the selectivity of the extraction was significantly reduced; the amount of neutral oil that co-extracted with the free fatty acids was increased from 23 to 94 wt%.     

Carbonation of Epoxidized Soybean Oil Improved by the Addition of Water

Carbonated soybean oil was synthesized from epoxidized soybean oil and CO₂ at atmospheric pressure and with tetrabutylammonium bromide (TBABr) as catalyst. Kinetic parameters, i.e., rate constants, activation energy and pre-exponential factors were determined. The effects of catalyst concentration and water content were studied. The reaction followed first-order kinetics with respect to epoxide at 100–140 °C. A steep increase in conversion (ca. 30 %) was obtained by increasing the amount of catalyst from 3 to 5 %. Further increasing the amount of catalyst to 7 % increased the conversion less than 10 %. The reaction proceeded faster when water was added; reaction times with water were ca. 70 % of the reaction times without water. Titration, FTIR and ¹H-NMR analyses indicated ca. 90 % conversion and ca. 88 % selectivity towards the carbonate after 70 h at 120 °C with 5 % mol TBABr and 1:3 molar ratio of water to epoxide.     

Phase equilibrium of the CO2/glycerol system: Experimental data by in situ FT-IR spectroscopy and thermodynamic modeling

Phase equilibrium experimental data for the CO₂/glycerol system are reported in this paper. The measurements were performed using an in situ FT-IR method for temperatures ranging from 40 °C to 200 °C and pressures up to 35.0 MPa, allowing determination of the mutual solubility of both compounds. Concerning the CO₂ rich phase, it was observed that the glycerol solubility in CO₂ was extremely low (in the range of 10⁻⁵ in mole fraction) in the pressure and temperature domains investigated here. Conversely, the glycerol rich phase dissolved CO₂ at mole fractions up to 0.13. Negligible swelling of the glycerol rich phase has been observed. Modeling of the phase equilibrium has been performed using the Peng–Robinson equation of state (PR EoS) with classical van der Waals one fluid and EoS/G^E based mixing rules (PSRK and MHV2). Satisfactory agreement was observed between modeling results and experimental measurements when PSRK mixing rules are used in combination with UNIQUAC model, although UNIFAC predictive approach gives unsatisfactory representation of experimental behavior.     

Epoxy resin modified with soybean oil containing cyclic carbonate groups

Carbonated soybean oil (CSO) containing five‐membered cyclic carbonate groups has been obtained in the reaction of epoxidized soybean oil with carbon dioxide in the presence of KI activated by 18‐crown‐6 under 6 MPa CO₂ pressure at 130°C. The CSO was used for modification of bisphenol‐A based epoxy resin. The composition epoxide‐cyclic carbonate was cured using polyamine hardeners by one‐step and two‐step procedures. All cured compositions were characterized for their thermal and mechanical properties and compared with the parent epoxy network. The optimal properties were obtained for compositions containing CSO and cured by one‐step method when phase separation takes place. The mechanical properties were discussed in terms of morphology observed by SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2904‐2914, 2006     

Production of bio-epoxide and bio-adhesive from non-edible oil

Epoxidation of Nahor oil was performed by H₂O₂ in the presence of acid catalyst at 50 °C. It was possible to obtain around 70% epoxide yield within 8 hrs of reaction. Amberlite IR 120H showed better epoxide yield compared to H₂SO₄ and Dowex 50 WX8. The performance of carboxylic acids was found to be in the order of formic acid>acetic acid>propanoic acid. The curing of epoxidized nahor oil involved using ethylenediamine (EDA) and diethylenetriamine (DETA). The adhesive property of the cured resins was tested and compared with commercially available glue. The force required to detach the cardboard joint was about 36.3 N for DETA-cured resin.     

Carbon dioxide: a renewable feedstock for the synthesis of fine and bulk chemicals

The syntheses of carbon dioxide (CO₂) based industrially important chemicals have gained considerable interest in view of the sustainable chemistry and “green chemistry” concepts. In this review, recent developments in the chemical fixation of CO₂ to valuable chemicals are discussed. The synthesis of five-member cyclic carbonates via, cycloaddition of CO₂ to epoxides is one of the promising reactions replacing the existing poisonous phosgene-based synthetic route. This review focuses on the synthesis of cyclic carbonates, vinyl carbamates, and quinazoline-2,4(1H,3H)-diones via reaction of CO₂ and epoxide, amines/phenyl acetylene, 2-aminobenzinitrile and other chemicals. Direct synthesis of dimethyl carbonate, 1,3-disubstituted urea and 2-oxazolidinones/2-imidazolidinones have limitations at present because of the reaction equilibrium and chemical inertness of CO₂. The preferred alternatives for their synthesis like transesterification of ethylene carbonate with methanol, transamination of ethylene carbonate with primary amine and transamination reaction of ethylene carbonate with diamines/β-aminoalcohols are discussed. These methodologies offer marked improvements for greener chemical fixation of CO₂ in to industrially important chemicals.     

A transient kinetic study of ethylene epoxidation over Ag/SiO2

Transient kinetics of ethylene epoxidation over a Ag/SiO₂ catalyst has been studied at relatively low temperatures (110-130‡C) using an automated square pulse cyclic reactor. It is observed at this low temperatures that the formation of CO₂ and H₂O was retarded compared to epoxide formation. The 100% selectivity toward ethylene oxide was obtained after hydrogen treatment of the catalyst surface. It indicates that maximum selectivity of 6/7 based on classical molecular oxygen hypothesis should be carefully reviewed. The participation of both atomic and molecular oxygen to epoxide formation was posiulated, but the former probably after recombination with subsurface oxygen.     

Direct conversion of CO2 with diols,aminoalcohols and diamines to cyclic carbonates,cyclic carbamates and cyclic ureas using heterogeneous catalysts

CO₂ has a large effect on global warming by greenhouse gases, and development of an effective technique for the reduction of CO₂ is a crucial and urgent issue. From the chemical viewpoint, CO₂ is regarded as a stable, safe and abundant C1 resource, and the transformation of CO₂ to valuable chemicals is promising not only for reduction of CO₂ but also for production of useful chemicals. This mini‐review focuses on the direct conversion of CO₂ with diols, aminoalcohols and diamines to cyclic compounds such as cyclic carbonates, cyclic carbamates and cyclic ureas, and in particular discusses the mechanisms for these reactions over heterogeneous catalysts. © 2013 Society of Chemical Industry     

Synthesis of organic carbonates from alcoholysis of urea: A review

Organic carbonates are green compounds with a wide range of applications. They are widely used for the synthesis of important industrial compounds including monomers, polymers, surfactants, plasticizers, and also used as fuel additives. They can be divided into two main classes: cyclic and linear carbonates. Dimethyl carbonate (DMC) and diethyl carbonate (DEC) are the important linear carbonates. Carbonyl and alkyl groups present in DMC and DEC make them reactive and versatile for synthesizing various other important compounds. Ethylene carbonate (EC), glycerol carbonate (GC) and propylene carbonate (PC) are well-known cyclic organic carbonates. Phosgenation of alcohols was widely used for synthesis of organic carbonates; however, toxicity of raw materials restricted use of phosgenation method. A number of new non-phosgene methods including alcoholysis of urea, carbonylation of alcohols using CO₂, oxy-carbonylation of alcohols, and trans-esterfication of alcohols and carbonates have been developed for synthesizing organic carbonates. Carbonylation of alcohols is preferred as it helps in utilization and sequestration of CO₂, however, poor thermodynamics due to high stability of CO₂ is the major obstacle in its large scale commercialization. Oxy-carbonylation of alcohols offers high selectivity but presence of oxygen poisons the catalyst. Recently, alcoholysis of urea has received more attention because of its inexpensive abundant raw materials, favorable thermodynamics, and no water-alcohol azeotrope formation. Also, ammonia evolved in this synthesis route can be recycled back to urea by reacting it with CO₂. In other words, this method is a step towards utilization of CO₂ as well. This article reviews synthesis of DMC, DEC, GC, PC, and EC from urea by critically examining various catalysts used and their performances. Mechanisms have been reviewed in order to give an insight of the synthesis routes. Research challenges along with future perspectives have also been discussed.