Ethylene Oxide Conversion Research Articles

Hybrid anionic block copolymerization: From organocatalysis‐streamlined crossover to internally microphase‐separated aggregates

AbstractPolyolefin‐b‐poly(ethylene oxide) (PEO) represents the most widely investigated amphiphilic block copolymers. So far, one‐pot continuous synthesis of such hybrid block copolymers has only been fulfilled by anionic polymerization through sequential addition of vinyl monomers and ethylene oxide (EO). It still remains challenging to achieve altogether high block efficiency, high polymerization efficiency, and high molar mass for PEO. Here, we report a one‐pot hybrid block copolymerization approach to polyisoprene/polystyrene(PI/PS)‐b‐PEO, in which PI/PS are formed by sBuLi‐initiated anionic vinyl‐addition polymerization, then in situ employed as macroinitiators for the anionic ring‐opening polymerization (ROP) of EO aided by an organic Lewis pair. The cooperative (dual‐ion‐complexing) catalytic effect of organobase and triethylborane is proven, for the first time, effective for lithium alkoxide initiator system, allowing to achieve at room temperature high ROP activity (complete EO conversion and PEO of 3–64 kg/mol reached in 1–6 h), narrow molar mass distribution, controlled block lengths and composition. Density functional theory calculation shows that phosphazene bases are particularly effective, compared with N‐heterocyclic bases, for complexing with Li+ and enhancing the nucleophilicity of oxyanion. The rate of ROP is also affected by Li+‐induced aggregation of the chain‐end ion pairs, which though can be offset by adequate catalyst loadings. The versatility of this approach is further demonstrated in the one‐pot synthesis of tri‐/tetrablock ter‐/quaterpolymers constituted by PI, PS, PEO, and poly(propylene oxide). Of great interest, PS‐b‐PI‐b‐PEO triblock terpolymer with a specific composition is found to form internally microphase‐separated micellar aggregates when dispersed in water.

Mechanistic insight into epoxide methoxycarbonylation catalyzed by Co complexes

The epoxide methoxycarbonylation is essential for the synthesis of advanced aldehydes and polyols, but the reaction mechanism has not been well resolved yet. In this work, we have established more detailed mechanism pathways for ethylene oxide methoxycarbonylation over Co-based complexes, the reaction pathway of the main by-product acetaldehyde, and examined the effect of nitrogen-containing heterocycles on the pathways using DFT calculation and experimental study. The conversion of ethylene oxide and product selectivity is sensitive to the structure of nitrogen-containing heterocycles. The addition of pyrazole as a ligand generated the highest conversion (98.3%) and dramatically inhibited by-product (e.g., acetaldehyde, 2-methoxyethanol) formation with the highest selectivity of methyl 3-hydroxypropionate (84.3%). The calculations reveal that the epoxide ring opening is the rate-determining step and the homonuclear ion pair mechanism is the most energetically preferred pathway. The ligand with promoting effect on the methyl 3-hydroxypropionate formation rate can lower the energy barrier of the ring-opening step with a proportional correlation established.

Design of a continuous device for ethoxylation reaction: The choice between micro and milli scale

A laminar flow model was developed to investigate the reaction kinetics of 1-dodecanol ethoxylation promoted by KOH, elaborating the data collected in microreactors. A generic laminar flow model was coded, and a sensitivity analysis was conducted highlighting the good flexibility of the model to simulate a wide range of conditions. Ethylene oxide diffusivity and liquid mixture viscosity were determined by applying existing correlations, carefully considering the change in viscosity with ethylene oxide conversion, temperature, and feed ethylene oxide/1-octanol ratio. The model was tested on literature data obtaining in every case good results. The obtained kinetic data were demonstrated to be in line with the ones obtained in separate investigations conducted in a fed-batch reactor, demonstrating that there was a real need in adopting the laminar flow reactor approach, as it allowed to retrieve of more precise information about the intrinsic kinetics of the ethoxylation reaction, when working with microreactors, compared with the ones obtainable with a plug-flow ideal fluid-dynamic model. The developed model was used to simulate the behavior of a milli-reactor (this device allows to reach sufficient productivity for industrial application) and it was forecasted the possibility to use continuous ethoxylation milli-reactors using fluid-dynamic conditions characterized by a high Reynolds number (>10000).

Tin Active Sites Confined in Zeolite Framework as a Promising Shape-Selective Catalyst for Ethylene Oxide Hydration.

Shape-selective stannosilicates have been post-synthesized for the hydration of epoxide to diols. A simple acid treatment has been employed to remove extensively the interlayer double four ring units, converting the three-dimensional (3D) UTL germanosilicate into a 2D layered IPC-1P intermediate. Isomorphous incorporation of tetrahedrally coordinated Sn active centers was realized via solid-liquid treatment of IPC-1P with diammonium hexachlorostannate aqueous solution, which was accompanied by the spontaneous condensation of neighboring silica-rich cfi layers upon calcination and structural construction of a 3D PCR structure. Sn-PCR stannosilicates with tunable Sn contents were thus prepared. With Sn-derived robust Lewis acidity confined in the intersecting 10- and 8-ring channels, the Sn-PCR (Si/Sn molar ratio of 77) catalyst served as a shape-selective nanoreactor for the hydration of ethylene oxide (EO) into ethylene glycol (EG), exhibiting a remarkable EO conversion (99.5 %) as well as a steady EG selectivity (>98.4 %) at greatly reduced H2 O/EO molar ratio and near-ambient reaction temperature.

Confirmation of the full conversion of ethylene oxide to 2-chloroethanol in fumigated foodstuffs: possible implications for risk assessment

This study describes the extension of a gas chromatography mass spectrometry (GC-MS) method, initially devoted to the analysis of ethylene oxide (EO) in ice cream, to a larger range of food items including herbs, spices, vegetables, inorganic salts, food supplements, thickeners, etc. Results are reported as EOTotal according to EC 2015/868 definition (expressed as EO equivalents as the sum of native EO and 2-chloroethanol (2-CE) after acidic hydrolysis) with a limit of quantification at 0.01 mg/kg regardless of the food item. Its ruggedness was demonstrated through fortification experiments on hundreds of samples. Re-analysis of 146 positive food samples without hydrolysis demonstrated that not EO but 2-CE is the predominant analyte detected in the different processed ingredients suspected to have been previously treated with EO. A series of eight contaminated dried herbs and spices were also re-analysed by four ISO 17025 accredited commercial laboratories making use of different analytical strategies for EO determination in foods. Each laboratory reported EOTotal levels within the same concentration range, but the resulting reproducibility ranged from 23% to 41% depending on the sample. Additionally, we show that results of free EO from methods based on conversion to 2-iodoethanol may lead to artefactual detection of native EO (false positive). An official method of analysis applicable for different food matrices would be useful to avoid discrepancies of results. Altogether, these data re-enforce the fact that in absence of native EO in food items, risk assessment of EO in foodstuffs should consider the predominance of 2-CE. A toxicological risk assessment using the food additive xanthan gum as a case study is discussed.

Plasma-enhanced catalytic oxidation of ethylene oxide over Fe–Mn based ternary catalysts

In this work, Fe–Mn based ternary catalysts (Fe–Mn-X, X = Ce, Co and Cu) were evaluated in the plasma-catalytic oxidation of ethylene oxide (EO) using a cylindrical dielectric barrier discharge (DBD) reactor. The addition of transition metal dopants to the Fe–Mn catalyst significantly improved the performance of plasma-catalyzed EO oxidation compared to the reaction using plasma only and the Fe–Mn catalyst. The highest EO conversion (91.9%) and CO2 selectivity (78.9%) were obtained over the Fe–Mn–Co catalyst at a specific energy input (SEI) of 730.2 J l−1. Moreover, the presence of water vapor improved EO conversion and CO2 selectivity in the relative humidity (RH) range of 0–60%, while further increasing the RH to 80% reduced EO conversion. The interactions between Fe, Mn and dopants increased the specific surface area and pore volume of the Fe–Mn-X catalyst, while maintaining the crystalline structure of the catalysts. The presence of the dopants enhanced the reducibility of the Fe–Mn-X catalysts and produced more surface adsorbed oxygen (Oads) on the catalyst surfaces. Moreover, the interactive effects among the Fe, Mn and dopants facilitated the plasma-catalytic oxidation reactions via enhanced surface reactions. The coupling of plasma with the Fe–Mn–Co catalyst reduced the formation of organic by-products in the plasma-catalyzed oxidation of EO.

SYNTHESIS OF ETHYLENE CARBONATE FROM ETHYLENE OXIDE AND CO2 IN THE PRESENCE OF ZINC PHENOLATES / IONIC LIQUID CATALYSTS

The synthesis of cyclic carbonates by the cycloaddition reaction of CO2 with epoxy compounds is one of the most promising directions in the utilization of CO2. The present work studies the synthesis of ethylene carbonate by the cycloaddition reaction of ethylene oxide with carbon dioxide in the presence of zinc-phenolate catalysts of the formula ZnY (where, Y – methylene-bis, thio-bis and dithio-bis alkyl phenols), ionic liquids of the formula RLX (where, R – H atom or C1 –C8 alkyl groups; L – cations of [NMP]+, [MIM]+, [Py]+ or alkyl amine; X – anions of Br–, НСОО–, СН3СОО–), or binary catalysts Zn-phenolate/ionic liquid, using selected optimal zinc phenolate and ionic liquid catalysts, or by using synthesized ionic liquid catalysts of the formula R2L2X2ZnY. In the presence of these catalysts the conversion of ethylene oxide is 32.0–99.0%, the selectivity for ethylene carbonate is 81.0–100.0%, the catalyst productivity is 210.0–1501.0 g EC/g Cat, and TOF is 891.0–12000.0 mol EC/mol Cat·h. Organic carbonates have a fairly large market (about 1.8 million tons/year) and are widely used as solvents, selective reagents, intermediates (for the synthesis of pharmaceuticals and agricultural preparates), fuel additives, as well as monomers in polymer synthesis

Enabling Oxygen-Sulfur Exchange Reaction to Produce Semicrystalline Copolymers from Carbon Disulfide and Ethylene Oxide.

This work describes the first example of semicrystalline poly(thiocarbonate)s from carbon disulfide (CS2 ) and ethylene oxide (EO), two mass producible low-cost monomers. Lewis acid/base pairs (LPs) exhibit high activity (EO conversion up to >99%, 8h) in catalyzing the copolymerization under low Lewis pair/monomer ratio of 1:1500. Oxygen-sulfur exchange reaction (O-S ER) during the copolymerization of CS2 and EO, the generation and mutual copolymerization with COS, CO2 , and episulfide, is harnessed to introduce crystallizable segments [SC(O)O and SC(S)S] in the copolymer. The type of Lewis base is found to have a great impact on the chain microstructure and the crystalline properties. The formed copolymers with melting point from 117.7 to 245.3°C are obtained. The maximum crystallinity is estimated to be 78% based on the powder wide-angle X-ray diffraction pattern. This work provides a general method to prepare semicrystalline sulfur-containing polymers.

Sustainable Dimethyl Carbonate Production from Ethylene Oxide and Methanol

AbstractA large‐scale dimethyl carbonate (DMC) production process from ethylene oxide (EO), CO2, and methanol was simulated and optimized. Unlike most industrial processes of DMC production, the direct conversion of EO and CO2 to ethylene carbonate (EC) and EC transesterification to DMC were performed in a single reactor. The reaction volume and the reactor operating pressure were selected as decision variables and evaluated. The key performance parameters, e.g., conversion per pass and CO2 intensity, were compared with conventional commercialized routes or novel promising processes in the literature.

Synthesis of ZSM-22 and Testing Its Catalytic Properties in the Ethylene Oxide Isomerization Reaction

The influence of the key parameters of the synthesis of a TON-type zeolite (ZSM-22) with or without an organic structure-directing agent on its phase composition has been established. The optimal composition of the reaction mixture and the crystallization time of ZSM-22 in the presence of 1,6-diaminohexane under static conditions have been determined. The dynamics of the formation of an impurity ZSM-5 by cocrystallization during the synthesis with stirring has been revealed. For zeolite ZSM-22 synthesized using the template-free procedure, the most important factors affecting the crystallinity and the crystallization time are the synthesis temperature, the amount of seed, and agitation of the reaction mixture. The zeolites synthesized according to the both procedures have been examined in the reaction of isomerization of ethylene oxide to acetaldehyde. Zeolite ZSM-22 obtained without adding the template is not inferior in activity to the zeolite of the same structure prepared in the presence of 1,6-diaminohexane. Moreover, it exhibits higher selectivity of ethylene oxide conversion to acetaldehyde. The complete conversion of ethylene oxide has been observed on ZSM-22 zeolites of both types at a reaction temperature of 400°C, the selectivity of its conversion to acetaldehyde being at least 93%.

Catalytic Synthesis of Triethanolamine in a Microchannel Reactor

Experimental studies of ammonia oxyethylation in a flow microchannel reactor are performed in broad ranges of temperatures (70–180°C) and residence times (0.47–3.3 min). The main products of the reaction between ethylene oxide (EO) and ammonia are monoethanolamine (MEA), diethanolamine (DEA), and target triethanolamine (TEA). It is shown that EO conversion grows along with residence time τ and reaches 90% at τ = 3.3 min. The highest selectivity toward MEA and DEA is observed at a temperature of 70°C and τ = 3.3 min. High selectivity toward TEA (84%) is achieved at short τ (0.47 min) and the maximum temperature (180°C). The TEA yield grows along with temperature and the residence time to reach 62% at τ = 3.3 min and temperatures of 155–180°C. Mathematical modeling of the ammonia oxyethylation process allows the kinetic constants of individual stages to be calculated. Differences between the obtained kinetic parameters and the literature data, due probably to using a microchannel reactor that ensures high parameters of heat and mass transfer instead of a traditional bulk triethanolamine synthesis reactor, are revealed.

Isomerization of Ethylene Oxide into Acetaldehyde on Zeolite with MTT (ZSM-23 Type) Structure

It was shown for the example of ZSM-23 zeolite with Si/Al = 50 that medium-porous zeolites with MTT structure are effective catalysts for gas-phase isomerization of ethylene into acetaldehyde. At 300–400°C, a nearly 100% conversion of ethylene oxide is observed, and the selectivity of its conversion to acetaldehyde exceeds 90%. The main by-products of the reaction are crotonic aldehyde and dioxane. ZSM-23 zeolite exhibits a higher selectivity and stability as compared with ZSM-5 zeolite having a 3D MFI structure. This zeolite provides an output of more than 28 g of acetaldehyde per gram of the catalyst per hour.

Catalytic Synthesis of Triethanolamine in a Microchannel Reactor

The process of ammonia oxyethylation was studied in a microchannel reactor at wide ranges of temperature (70–180 °C) and contact time (0.47–3.3 min). Monoethanolamine (MEA), diethanolamine (DEA), and the target triethanolamine (TEA) were the main products of the reaction between ethylene oxide (EO) and ammonia. The EO conversion was shown to increase with lengthening contact time (τ), it being 90 % at τ = 3.3 min. The highest selectivity to MEA and DEA was observed at 70 °C and τ = 3.3 min. A high selectivity to TEA (84 %) was reached at short τ (0.47 min) and maximal temperature (180 °C). The yield of TEA increased as temperature was elevated and contact time lengthened to reach 62 % at τ = 3.3 min and 155–180 °C. Mathematical modeling of the process allowed kinetic constants of individual stages to be calculated. The difference between the calculated and literature kinetic parameters could be accounted for by the specific features of the microchannel reactor providing, unlike traditional reactors for synthesis of triethanolamine, high heat and mass transfer.

Lewis Acid Catalysis Confined in Zeolite Cages as a Strategy for Sustainable Heterogeneous Hydration of Epoxides

We report a heterogeneous catalysis strategy to the sustainable hydration of epoxides by designing robust Lewis acid catalysts confined in zeolite cages as natural shape-selective nanoreactors. In the case of ethylene oxide hydration, Sn-H-SSZ-13 zeolite exhibits remarkable catalytic performance, with an ethylene oxide conversion above 99% and a monoethylene glycol selectivity above 99%, at approaching stoichiometric water/ethylene oxide ratios and near-ambient reaction temperatures. It is revealed by theoretical studies that partially hydroxylated Sn species are the preferred Lewis acid sites for the hydration of ethylene oxide. The concept of Lewis acid catalysis confined in zeolite cages may be applied in the future in the chemical industry to develop energy-saving and environmentally benign processes.

Triethanolamine synthesis in a continuous flow microchannel reactor

Abstract Triethanolamine synthesis from ammonia and ethylene oxide in a continuous flow microchannel reactor has been studied in a wide range of temperatures and residence times. Microchannel reactor performance has been compared to that of conventional tubular reactor. In the microchannel reactor ethylene oxide conversion and triethanolamine yield appear to be higher due to the more efficient mixing of initial reagents and far more intensive heat transfer.

Layered niobic acid with self-exfoliatable nanosheets and adjustable acidity for catalytic hydration of ethylene oxide

Layered niobic acids (H x K 1− x Nb 3O 8, x = 0–1) are reported as new solid acid catalysts for the selective hydration of ethylene oxide (EO). They are prepared by simply calcinating Nb 2O 5–K 2CO 3 mixture followed by an ion-exchange process in HNO 3 solution of different concentrations. The highest selectivity for monoethylene glycol (MEG) is achieved over 95% with EO conversion of >99% at x of 0.7 under H 2O/EO ratio of 8. Combined with the results of first-principles density functional theory calculations and Hammett indicator method, it is revealed that the suitable acid strength is more crucial for MEG selectivity than acid amount. Furthermore, a self-exfoliation of layered HNb 3O 8 is also found during EO hydration, which proves to be another important factor for its good catalytic performance by exposing the abundant acid sites among the Nb 3 O 8 - nanosheets. The thermal stability investigation of HNb 3O 8 also indicates a careful selection of characterization and application way for this layered niobic acid.

Synthesis of dimethyl carbonate from CO2 and ethylene oxide catalyzed by K2CO3-based binary salts in the presence of H2O

We systematically screened binary catalysts for synthesis of dimethyl carbonate (DMC) from CO2, CH3OH and ethylene oxide (EO) in the presence of H2O by two-step transesterification process, and found the commercial quaternary ammonium salts/K2CO3, pyridinium salts/K2CO3 and KI/K2CO3 were effective binary catalysts for two-step synthesis of DMC with no need for separation of ethylene carbonate (EC). Near 100% conversion of EO and 82% yield of DMC were obtained under mild reaction conditions. However, the imidazolium salts were not compatible with inorganic alkaline possibly because of the reactive C(2)–H in the imidazolium ring. Furthermore, the KI/K2CO3 could be easily recovered and reused 12 times without obvious loss of its catalytic activity. The process avoids EC separation, and represents a simple, ecologically safer, cost-effective and energy-saving route for synthesis of DMC with high product quality, as well as easy catalyst recycling.

Quaternary Ammonium Ionic Liquids as Bi-functional Catalysts for One-step Synthesis of Dimethyl Carbonate from Ethylene Oxide, Carbon Dioxide and Methanol

One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, 1H and 13C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bi-functional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results. One kind of novel quaternary ammonium ionic liquids has been developed and for the first time used as bi-functional catalysts in the one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide, CO2 and methanol. Normally, stronger basicity could be obtained by altering anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly.

Studies on mechanism for homogeneous catalytic hydration of ethylene oxide: Effects of pH window and esterification

Abstract Selective hydration of ethylene oxide (EO) was investigated with several inorganic salt systems as homogeneous catalysts. By optimizing reaction conditions, the highest monoethylene glycol (MEG) selectivity of 98% was obtained with >99% EO conversion at a water/EO molar ratio = 10. The effects of pH value and anion addition–esterification on MEG selectivity were systematically studied, and a comprehensive mechanism was proposed based on the results. The conclusion should be useful in developing high performance catalysts for the manufacture of MEG by EO hydration at a low water/EO ratio.

Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization

Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCB-EO) and 1-benzocyclobutene-1′-phenylethylene (BCB-PE) through Diels−Alder cycloaddition at 235 °C. Surface-functionalized MWNTs-g-(BCB-EO)n and MWNTs-g-(BCB-PE)n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO)n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE)n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO)n and MWNTs-g-(BCB-PS)n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FT-IR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites. The TEM images showed the presence of thick layers of polymer up to 30 nm around the MWNTs. The living nature of the growing polystyryllithium was used to produce diblock copolymer grafts using sequential polymerization of isoprene on the surface of MWNTs.