Oxetane Research Articles

Unlocking enhanced gas storage capacity in tuned methane hydrates: Exploring eutectic compositions and water-to-hydrate conversion

The tuning effect of gas hydrates has received widespread interest as a promising approach for energy gas storage due to its unique features for enhancing gas storage capacity and formation conditions. However, its practical application has been stagnant because the effect of various factors has still not been revealed to induce the tuning effect. Here, we provide the dominant factors and optimized conditions related to the tuning effect to achieve the practical enhancement of gas storage capacity under mild formation conditions (272.0 K, 2.35 MPa). Based on the tetrahydrofuran (THF)/trimethylene oxide (TMO) + CH4 hydrates, dominant factors that can affect tuning effects such as eutectic composition, the concentration of the promoter, formation methods, and conversion of water-to-hydrate were experimentally examined by employing the in-situ Raman spectroscopy. The tuning effects of hydrates formed from the aqueous solutions (water-borne) were slowly advanced, unlike all hydrates formed from iced particles (ice-borne) which extremely rapidly induced them. It suggests that the eutectic point was the primary factor in water-borne hydrates, whereas the tuning effect in ice-borne hydrates is mainly governed by the formation rate and stochastic nature. Interestingly, our experiments confirmed for the first time that the gas uptake of water-borne tuned gas hydrates may be higher than those of untuned hydrates (i.e. 5.56 mol% stoichiometric concentration). This work provides not only the dominant parameters but also promising strategies for the practical application of tuning effects to efficient hydrate-based gas storage.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.

Investigating two synthetic routes for gas hydrate formation to control the trapping of methane from natural gas

Gas hydrate is considered as an emerging technique for natural gas storage and CH4 separation from natural gas, because assorted nano-sized cages of gas hydrate allow selective trapping of specific gaseous guests such as CH4, C2H6, and C3H8. When a mixture of CH4, C2H6, and C3H8 forms gas hydrates with a liquid promoter at 5.6 mol%, sII large cages (sII-L) can be fully occupied by a promoter, while only CH4 remains in the hydrate phase by occupying sII small cages (sII-S). Based on this, can CH4 be selectively stored or separated from natural gas? Here, we aimed to elucidate the cage-filling behavior of gaseous and liquid guests in CH4 + C2H6 + C3H8 hydrates formed with the addition of tetrahydrofuran (THF), trimethylene oxide (TMO), or 1,3-dioxolane (DIOX). We examined feasible strategies for synthesizing gas hydrate focusing on ice-borne or water-borne route. Our results suggested that ice-borne gas hydrates were a promising option for CH4 separation, because only CH4 was trapped in ice-borne gas hydrates. In contrast, C2H6 and C3H8 shared sII-L with promoters in water-borne gas hydrates. Although partial occupation of sII-L by C2H6 and C3H8 reduced CH4 purity in the hydrate phase, it resulted in enhancing the CH4 uptake in THF hydrate formed via water-borne route, unlike TMO and DIOX. The present findings will broaden the understanding of the cage occupation behavior in ternary gas hydrates formed with liquid promoters, and provide feasible strategies for synthesizing gas hydrates for storing natural gas or CH4 separation from natural gas.

Zr(IV) Catalyst for the Ring-Opening Copolymerization of Anhydrides (A) with Epoxides (B), Oxetane (B), and Tetrahydrofurans (C) to Make ABB- and/or ABC-Poly(ester-alt-ethers).

Poly(ester-alt-ethers) can combine beneficial ether linkage flexibility and polarity with ester linkage hydrolysability, furnishing fully degradable polymers. Despite their promising properties, this class of polymers remains underexplored, in part due to difficulties in polymer synthesis. Here, a catalyzed copolymerization using commercially available monomers, butylene oxide (BO)/oxetane (OX), tetrahydrofuran (THF), and phthalic anhydride (PA), accesses a series of well-defined poly(ester-alt-ethers). A Zr(IV) catalyst is reported that yields polymer repeat units comprising a ring-opened PA (A), followed by two ring-opened cyclic ethers (B/C) (−ABB– or −ABC−). It operates with high polymerization control, good rate, and successfully enchains epoxides, oxetane, and/or tetrahydrofurans, providing a straightforward means to moderate the distance between ester linkages. Kinetic analysis of PA/BO copolymerization, with/without THF, reveals an overall second-order rate law: first order in both catalyst and butylene oxide concentrations but zero order in phthalic anhydride and, where it is present, zero order in THF. Poly(ester-alt-ethers) have lower glass-transition temperatures (−16 °C < Tg < 12 °C) than the analogous alternating polyesters, consistent with the greater backbone flexibility. They also show faster ester hydrolysis rates compared with the analogous AB polymers. The Zr(IV) catalyst furnishes poly(ester-alt-ethers) from a range of commercially available epoxides and anhydride; it presents a straightforward method to moderate degradable polymers’ properties.

Hydrogen bonding networks and cooperativity effects in the aqueous solvation of trimethylene oxide and sulfide rings by microwave spectroscopy and computational chemistry.

The intermolecular interactions responsible for the microsolvation of the highly flexible trimethylene oxide (TMO) and trimethylene sulfide (TMS) rings with one and two water (w) molecules were investigated using rotational spectroscopy (8-22GHz) and quantum chemical calculations. The observed patterns of transitions are consistent with the most stable geometries of the TMO-w, TMO-(w)2, and TMS-w complexes at the B2PLYP-D3(BJ)/aug-cc-pVTZ level and were confirmed using spectra of the 18O isotopologue. Due to its effectively planar backbone, TMO offers one unique binding site for solvation, while water can bind to the puckered TMS ring in either an axial or equatorial site of the heteroatom. In all clusters, the first water molecule binds in the σv symmetry plane of the ring monomer and serves as a hydrogen bond donor to the heteroatom. The second water molecule is predicted to form a cooperative hydrogen bonding network between the three moieties. Secondary C-H⋯O interactions are a key stabilizing influence in trimers and also drive the preferred binding site in the TMS clusters with the axial binding site preferred in TMS-w and the equatorial form calculated to be more stable in the dihydrate. Using an energy partition scheme from the symmetry-adapted perturbation theory for the O, S, and Se containing mono- and dihydrates, the intermolecular interactions are revealed to be mainly electrostatic, but the dispersive character of the contacts is enhanced with the increasing size of the ring's heteroatom due to the key role of longer-range secondary interactions.

Biochemical and microbiological analyses of Burukutu (native beer) and a brand of factory-based lager beer (STAR)

Consumption of Burukutu (native beer) among the people of the area of study is a norm. The techniques applied in its production are crude and non scientific. As a result, undesirable compounds, which may themselves be toxic, could be produced as components of the ‘brew’. Also, microbes present may be pathogenic. Ten samples were aseptically collected. A composite of 2 ml portions of each of nine (9) Burukutu samples was prepared for microbial count and identification. In the case of organic metabolites and alcohol content, individual samples were analysed. Spectrophotometry was applied to determine the alcohol content; mass spectrometry method was used to identify the metabolites generated. Nutrient agar and indole test were applied for aerobic plate count and microbial identification. The results obtained revealed three isolates in all the samples thus: Escherichia coli, Bacillus species and Saccharomyces cerevisiae. The alcohol content ranged between 2.0-2.6% (v/v). Metabolites generated in both Burukutu and factory-based lager beer included glycerine, 1-pentanol, methanol, 1-glyceraldehyde, trimethylene oxide, 1-butanol, toluene, benzene acetic acid Propanoic acid, 2-hydroxy ethyl ester, Heptafluorobutyric acid, n-Pentyl ester, 4-butoxy-5,7-dinitrobenzo[1,2,5] Thiadiazole, Benzene acetic acid, 2 butyl ester, ethyl alcohol. Both Burukutu contain undesirable metabolites which may synergise with alcohol making it toxic to the system. Personal and environmental hygiene will help reduce levels of contaminants in alcoholic beverages otherwise pathogenic microbes could grow in the liquor being consumed.

Indium-Catalyzed Synthesis of 1,2-Dihydroquinolines through Rearrangement of Oxetanes

Key words oxetanes - anilines - indium catalysis - dihydroquinolines

Analysis of the Coriolis perturbed rovibrational spectrum of the C[sbnd]O asymmetric stretch and C[sbnd]C symmetric stretch of trimethylene oxide

Rotationally-resolved vibrational spectra of trimethylene oxide (c-C3H6O) were recorded using synchrotron radiation from the Canadian Light Source between 400 and 1200 cm−1 with a resolution of 0.000959 cm−1. The dense spectra are composed of transitions arising from excitation of several fundamental vibrations as well as hotbands and combination bands involving the very low frequency ring puckering (ν18) vibration at ~53 cm−1. To date, 3452 transitions have been assigned corresponding to the CO asymmetric stretch (ν23) at ~1008 cm−1 and the CC symmetric stretch (ν6) at ~1033 cm−1 which are coupled via second order c-type Coriolis interaction. An additional perturbation from a lower energy state was observed and attributed to a first order b-type interaction with a state that is likely the combination of the CC asymmetric stretching (ν24) at ~937 cm−1 and ring puckering motions. An additional 916 transitions involving the CO stretching mode were assigned to two hotbands that originate in the first and second excited ring puckering states of trimethylene oxide. Accurate band centers for the ν6, ν23, ν23 + ν18, ν23 + 2ν18 and ν24 + ν18 vibrational states were determined and are compared with harmonic and anharmonic frequency estimates at the MP2 and DFT B3LYP levels using the 6-311++G(d,p) basis set. The analysis of additional features at lower frequency is in progress and will be reported in a subsequent article.

How Does the Guest—Host Hydrogen Bonding Affect the Thermal Properties of Clathrate Hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest-host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest-host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest-host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

How does the guest—host hydrogen bonding affect the thermal properties of clathrate hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest—host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest—host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest—host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

VUV excited-state dynamics of cyclic ethers as a function of ring size.

The vacuum ultraviolet (VUV) absorption spectra of cyclic ethers consist primarily of Rydberg ← n transitions. By studying three cyclic ethers of varying ring size (tetrahydropyran, tetrahydrofuran and trimethylene oxide, n = 6-4), we investigated the influence of ring size on the VUV excited-state dynamics of the 3d Rydberg manifold using time-resolved photoelectron spectroscopy (TRPES), time-resolved mass spectroscopy (TRMS) and ab initio electronic structure calculations. Whereas neither the electronic characters nor the term energies of the excited-states are substantially modified when the ring-size is reduced from n = 6 to 5 to 4, the excited-state lifetimes concomitantly decrease five-fold. TRPES and TRMS allow us to attribute the observed dynamics to a Rydberg cascade from the initially excited d-Rydberg manifold via the p-Rydberg manifold to the s-Rydberg state. Cuts through potential energy surfaces along the C-O bond reveal that a nσ* state crossing brings the s-Rydberg state along a path to the ring-opened ground state. The observed difference in excited-state lifetimes is attributed to an increasing slope along the repulsive C-O bond coordinate as ring size decreases.

Investigation of tuning behavior of trimethylene oxide hydrate with guest methane molecule and its critical guest concentration

Due to the promising storage capacity for CH4, the method of natural gas storage and transportation using solid gas hydrate is recognized as an alternative to conventional liquefied natural gas process. To make this alternative more viable, however, it is necessary to further shift the formation temperature and pressure of natural gas hydrate closer to ambient conditions. Although there is a trade-off between storing more CH4 and mitigating the formation conditions, it is known that adding specific liquid molecules such as tetrahydrofuran, as a secondary guest to CH4 hydrate could lead to favorable thermodynamic stability while still affording promising CH4 storage capacity via a mechanism known as the tuning phenomenon. Here, this study focused on trimethylene oxide (TMO) + CH4 hydrate to reveal its unique guest occupation patterns for potential application to natural gas storage and transportation. The occurrence of the tuning behavior on the TMO + CH4 hydrate was observed for the first time. Most importantly, the tuning factor referred to as the CH4 occupation ratio between the large and small cages of sII hydrate, exhibited a value of 0.73 at the critical guest concentration, which is the largest value reported to date. The phase equilibria of the TMO + CH4 hydrate were provided for TMO concentrations ranging from 1.0 to 5.56 mol%. The spectroscopic data obtained from synchrotron HRPD, dispersive Raman, and 13C solid-state HPDEC MAS NMR spectrometry provided experimental evidence of the distinct enclathration characteristics of CH4 and TMO molecules during the tuning phenomenon. These findings provide fundamental knowledge on the tuning effect and lend useful insights for designing and developing gas hydrate-based natural gas storage and transportation process.

The thermal properties of binary structure sI clathrate hydrate from molecular dynamics simulation

ABSTRACTIn this work, we present temperature dependence of lattice parameter and normalised lattice parameter in the atmospheric pressure and 120 bar and also pressure dependence of unit cell volume and normalised unit cell volume at 150 and 250 K for variety guests with different size, polarity and guest–host hydrogen bonding capability such as trimethylene oxide (TMO), ethylene oxide (EO), formaldehyde (FA), cyclobutane (CB), cyclopropane (CP) and ethane (Et) in the large cages with CH4 in small cages of sI clathrate hydrates by molecular dynamics simulations. The obtained values of lattice parameters for the guest species are compatible with the experimental values. These clathrate hydrates are simulated with TIP4P/ice four-site water potential. Herein, isobaric thermal expansivity and isothermal compressibility are calculated at a temperature range of 50–250 K and a wide pressure range. These structural properties have been compared for guests which they are isoelectronic and have similar masses but with different size and polarity. We use molecular dynamics simulations to relate microscopic guest properties, like guest–host hydrogen bonding to macroscopic sI clathrate hydrate properties. The temperature dependence of thermodynamic properties such as constant-volume and constant-pressure heat capacity is presented in the atmospheric pressure for these guest species.

Ring-Size Effects on the Stability and Spectral Shifts of Hydrogen Bonded Cyclic Ethers Complexes

In order to investigate ring-size effects on the stability and spectral shifts of hydrogen bonded cyclic ethers complexes, the strength of hydrogen bonds in gas phase complexes formed between 2,2,2-trifluoroethanol (TFE) and selected cyclic ethers were examined using FTIR spectroscopy. TFE was chosen as hydrogen bond donor in these complexes, while trimethylene oxide (TMO), tetrahydrofuran (THF) and tetrahydropyran (THP) were selected as hydrogen bond acceptors. Comparable OH-stretching red shifts were observed in the three kinds of complexes. The difference of red shifts is so small (<7 cm−1) for TFE−TMO/THF/THP complexes that one can conclude that their stabilities and the strength of the hydrogen bonds are nearly similar and do not show any marked dependence with the ring size of the hydrogen bond acceptor. The equilibrium constants for the complexation were determined, and atoms-in-molecules (AIM) and natural bond orbital (NBO) analyses were performed to further investigate the intermolecular interactions. Regardless of the ring size, hydrogen bonds in the complexes showed similar strength, in agreement with the observed OH-stretching red shifts.

Understanding cyclic by-products and ether linkage formation pathways in the transesterification synthesis of aliphatic polycarbonates

An overall picture of the reaction pathways towards the side products and final polymers during the transesterification synthesis of biodegradable aliphatic carbonates (APCs) were delineated for the first time. Catalysed by sodium ethoxide, the normal reaction between α,ω-diols (carbon number n=2–6) and diethyl carbonate generates APC oligomers with propagating terminal alkoxide anions. These anions can backbite at the nearest carbonate carbons or the nearest carbonate α-CH2 carbons in the same APC chains, eliminating corresponding cyclic carbonates or cyclic ethers. Also, each alkoxide anion can randomly attack a carbonate α-CH2 carbon in another APC chain, generating ether linkages in the final polymers whose percentages are about 100%, 1.35%, 0.08% and 0% for n=2, 3, 4 and 5, respectively. The content of cyclic carbonates shows a similar decreasing trend; ethylene carbonate (n=2) even predominates over the final polymer while trimethylene carbonate (n=3) and 1,4-butylene carbonate (n=4) are only minor by-products. Moreover, the latter two cyclic carbonates are not stable enough and can further decarboxylate, forming relatively high amount of allyl alcohol and tetrahydrofuran, respectively. However, trimethylene oxide (n=3) and tetrahydropyran (n=5) are minor cyclic ethers. The thorough understanding of the chemical process is essential to improve the APC synthesis.

Molecular Dynamics Study of Guest–Host Hydrogen Bonding in Ethylene Oxide, Trimethylene Oxide, and Formaldehyde Structure I Clathrate Hydrates

Molecular dynamics simulations are used to study the guest–host hydrogen bonding and guest dynamics in the clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. Two water models, the SPC/E and TIP4P/ice, were used in the simulations. Binary hydrates are constructed with these guests in the large 14-sided cages and methane placed in the small 12-sided cages of the structure sI clathrate hydrates. The results of these simulations are compared with the nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane, respectively, for TMO, EO, and FA. These simulations show that oxygen atoms of the cyclic ethers and carbonyl oxygen of formaldehyde form hydrogen bonds to differing degrees with cage water hydrogen atoms. The TMO size is larger than that of the EO and FA molecules and the closer proximity of the atoms of this large guest to the cage water molecule enhances the probability of guest–host hydrogen bonding in the ...

On the phase behaviour of oxetane-CO2 and propargylic alcohols-CO2 binary mixtures by in situ infrared micro-spectrometry

The phase behaviour of carbon dioxide/propargylic alcohols and carbon dioxide/oxetanes mixtures has been investigated using in-situ FTIR microspectrometry that allows us determining the evolution of the concentration of each component in the liquid phase as a function of temperature and pressure. It was at the same time possible to look inside the cell and to visualize the expansion of the liquid phase during the increase of the pressure. The measurements were performed at three different temperatures (40, 70 and 100°C) for pressures ranging between 0.1 and 15MPa. Propargylic alcohol (PA), 2-methyl-3-butyn-2-ol (MBOL), 3-butyn-1-ol (BOL) and trimethylene oxide (TMO) were selected as these molecules are used in the synthesis of cyclic or polycarbonates by coupling with CO2. Thus, we determined the CO2 sorption and the concentration of the substrate in the liquid phase. Thanks to these measurements, we established the pressure-composition phase diagram for the liquid phase of these substrate/CO2 binary mixtures.

Silaboration of Oxetanes and Unactivated Epoxides

Silaboration of Oxetanes and Unactivated Epoxides

Synthesis of Highly Functionalized Oxetanes

Key words oxetanes - O–H insertion - rhodium - catalysis - diazomalonates

Polymer synthesis by solid-acid catalyst based on heteropolyacid ammonium salt

Ring-opening polymerizations of four kinds of monomers such as glycidyl phenyl ether, oxetane (OX), e-caprolactone (CL), and 2,2-dimethyltrimethylene carbonate were performed with a silica-supported catalyst based on heteropolyacid ammonium salt, (NH4)3PW12O40/SiO2. Preparation of the catalyst was done by an impregnation of (NH4)3PW12O40 onto SiO2 in aqueous ammonia, followed by its calcination. Selectivities for skeletal isomerizations of 1-butene exhibited a strong acidity of the (NH4)3PW12O40/SiO2. Among four monomers, the OX and CL were the promising monomers for this polymerization system. The resulting poly(OX) and poly(CL) with number-average molecular weight (M n) of 2900–6500 and 5500–8600 were obtained in 65–80 and 93–96 % yields, respectively. Furthermore, copolymerization of OX and CL successfully proceeded, affording poly(OX-co-CL) with compositions of OX:CL = 63:37, 50:50, and 37:63 having M n = 2400–3800 in 64–84 % yields.