Dibutyl Ether Research Articles

O-18 - Improvements in separation of antimony-119 from bulk tin target using a novel dibutyl ether resin

O-18 - Improvements in separation of antimony-119 from bulk tin target using a novel dibutyl ether resin

Effectiveness of co-solvents in boosting LDPE depolymerization in diesel

Plastic pollution is increasing as the management of plastic waste has become a global challenge. The possibility of turning plastic waste into fuel at low temperatures has been successfully reported in our recent research. However, the low recycling ratio and higher fuel viscosity were the main limitations. The focus of this research was to improve the depolymerization process of low-density polyethylene (LDPE) in diesel by introducing various amounts of co-solvents. The resultant product can be directly used as transportation fuel without further refining. Several co-solvents were examined in the LDPE/diesel blend: di-butyl ether, a-pinene, toluene, and o-xylene under various pressures (1, 5, 10, and 20 bar). The quality of fuel products was evaluated using differential scanning calorimetry (DSC), an Anton Paar MCR302 rheometer, and a bomb calorimetric thermometer. The degradation behavior of LDPE in diesel is affected by the co-solvents, and the highest dissolution occurred with 10 wt% co-solvent in diesel. Among the tested reactor pressures, the most effective pressure was 10 bar resulting in 92.4% LDPE dissolution. The addition of co-solvents improved the quality of the fuel blend in terms of the kinematic and dynamic viscosities compared with the PD/LDPE blend. The higher heating value (HHV) of the resultant fuel blend was higher compared to non-solvent, pure diesel-derived LDPE fuel blends. The values of HHV for PD, PD/LDPE (10% a-pinene and 1 bar), PD/LDPE (10% xylene and 1 bar), and PD/LDPE (10% xylene and 10 bar) were 45.24 MJ/kg, 45.60 MJ/kg, 46.05 MJ/kg, and 46.14 MJ/kg, respectively.

Waste PVC upcycling: Transferring unmanageable Cl species into value-added Cl-containing chemicals

The upcycling of waste polyvinyl chloride (PVC) is a grand challenge because of the unmanageable Cl species. Here, we develop a Cl-transfer strategy to upcycle waste PVC into value-added organic chlorides and PE-like polymer with various Cl acceptors (tetrahydrofuran, dibutyl ether and butanol) over Ru/Al2O3 catalyst. The high utilization efficiency of Cl (> 80 %) can be obtained over Ru/Al2O3 at 180 °C, 2Mpa H2 with tetrahydrofuran as an acceptor within tens of hours. The excellent performance is attributed to key features including Al2O3 for the C-O bond activation and metal Ru for C-Cl bond activation and H2 dissociation. The remaining PE-like polymer after removing Cl could be regarded as PE-like feedstock and further converted into methane through the same Ru/Al2O3 catalyst. The Cl-transfer system also enables the upcycling of several common PVC-contained wastes and works well in the scale-up test. This work offers a catalytic path to integrate waste PVC plastic into the supply chain of organic chlorides under the context of circular economy.

A comparative study for the n-butanol/n-octanol and n-butanol/ di-n-butylether fueled dual-fuel engines with different injection timings

In this study, numerical simulations were performed to compare the combustion and emission characteristics of n-butanol/n-octanol (B/O) and n-butanol/di-n-butylether (B/D) dual-fuel engines at the different start of injection (SOI) timings. The three-dimensional dual-fuel engine simulation was implemented by coupling KIVA-CHEMKIN with a multi-component chemical reaction mechanism containing n-butanol, n-octanol, and di-n-butylether (DnBE). The reliability of the numerical models was verified by comparing the simulated and experimental in-cylinder pressure, heat release rate (HRR), and emissions. Then B/O and B/D dual-fuel engines with different premixed n-butanol ratios (B0, B10, B20, B30, and B40) were simulated at 1500 rpm with normal SOI timing (7 deg BTDC) and advanced SOI timing (20 deg BTDC), respectively. It has been found that an increased ratio of premixed fuel would increase the peak cylinder pressure due to the higher oxygen content of n-butanol. The change of SOI timing has a significant effect on the B/O engine and a minor influence on the B/D engine. When the SOI timing is advanced from 7 deg BTDC to 20 deg BTDC, the B/O engine changes from premixed to premixed-diffusion combustion phase. In addition, the B/O engine exhibits a more significant reactivity-controlled combustion mode under advanced SOI timing. In terms of emissions, the B/O engine emits more CO than the B/D engine, which is due to the fact that n-octanol is less volatile, resulting in more local high equivalence ratio areas in the cylinder. Since the in-cylinder combustion temperature and combustion duration of the B/O engine are less than those of the B/D engine, the NOx emissions of the B/O engine are lower. With advanced SOI timing, the addition of premixed n-butanol can reduce both CO and NOx, but the emission values are still high and further optimization is needed.

Green-solvent-processed formamidinium-based perovskite solar cells with uniform grain growth and strengthened interfacial contact via a nanostructured tin oxide layer.

Green-solvent-processed perovskite solar cells (PSCs) have reached an efficiency of 20%, showing great promise in safe industrial production. However, the nucleation process in green-solvent-based deposition is rarely optimized, resulting in randomized crystallization and much lowered reported efficiencies. Herein, a nanostructured tin oxide nanorods (SnO2-NRs) substrate is utilized to prepare a high-quality formamidinium (FA)-based perovskite film processed from a green solvent of triethyl phosphate (TEP) with a low toxic antisolvent of dibutyl ether (DEE). Compared with SnO2 nanoparticles, the oriented SnO2-NRs can accelerate the formation of heterogeneous nucleation sites and retard the crystal growth process of the perovskite film, resulting in a high-quality perovskite film with uniform grain growth. Furthermore, a chlorine-terminated bifunctional supramolecule (Cl-BSM) is introduced to passivate the increasing interfacial defects due to the vast contact area in SnO2-NRs. Correspondingly, the substrate design of SnO2-NRs with Cl-BSM increases the power conversion efficiency (PCE) of green-solvent-processed PSCs to 22.42% with an open-circuit voltage improvement from 1.02 to 1.12 V, which can be attributed to the uniform grain growth and reduced carrier recombination at the SnO2-NRs/perovskite interface. More importantly, the photo and humidity stabilities of the unencapsulated device for up to 500 and 1000 hours are also achieved with negligible interfacial delamination after aging. This work provides a new perspective on the future industrial scale production of PSCs using environment-friendly solvents with compatible substrate design.

Inner Lithium Fluoride (LiF)-Rich Solid Electrolyte Interphase Enabled by a Smaller Solvation Sheath for Fast-Charging Lithium Batteries

Fast-charging lithium-ion batteries (LIBs) have been severely hampered by the slow development of their electrolytes. Herein, we demonstrate that the size effect of solvent sheath would pose a great effect on the fast-charging performance of LIBs. Three similar ethers, including diethyl ether (DEE), dipropyl ether (DPE), and dibutyl ether (DBE), were mixed with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and lithium bis(fluorosulfonyl)imide (1 M) to form an electrolyte for fast-charging LIBs, respectively. The results showed that it is more difficult to form ternary graphite intercalation compounds (GICs) in the electrolyte with a larger solvation sheath. The DEE electrolyte can form stable GICs and generate an inner LiF-rich solid electrolyte interphase (SEI), lowering the diffusion barrier of Li+. Therefore, the graphite anode powered by the DEE electrolyte can maintain a capacity of 190 mAh g-1 at 4 C after 500 cycles. This kind of size effect of solvation sheath is also applicable to lithium metal batteries.

UV light enhanced catalytic performance of heteropolyacid-TiO2 systems

A series of catalysts based on TiO2 polymorphs were designed with tungstophosphoric acid H3PW12O40 (HPW), either alone or with addition of Fe2O3. These HPW@Fe2O3@TiO2 nanocomposites showed satisfactory performance in the dehydration of n-butanol at 120 – 200 °C in gas-phase under both the thermocatalytic and the photothermocatalytic conditions. The highest catalytic activity in this reaction was achieved over HPW supported on the home-designed TiO2 (HPW/hp), on hp with the addition of Fe2O3 (HPW/Fe/hp) and on the hydrophobic titanium oxide T805 (HPW/T805). The main product turned out to be cis-butene, apart from trans-butene, di-n-butyl ether (DNBE) and butyraldehyde that have also been detected. The influence of the light on the course of the catalytic alcohol conversion was discussed. Basing on proposed energy diagram with electron and hole transfer paths for the HPW@Fe2O3@TiO2 catalysts the probable mechanism of charge transfer upon UV irradiation was proposed.

Experimental study of castor biodiesel ternary blends with ethanol, butanol, diethyl ether and dibutyl ether in a diesel engine

Experimental study of castor biodiesel ternary blends with ethanol, butanol, diethyl ether and dibutyl ether in a diesel engine

Critical Review of the Various Reaction Mechanisms for Glycerol Etherification

This review provides in-depth coverage of numerous mechanisms available for the etherification process of glycerol, including alcohol solvent, olefin solvent and solvent-free routes along with products that are formed at various stages of the reaction. Mono tert-butyl glycerol ether (MTBG), di tert-butyl glycerol ether (DTBG), and tri tert-butyl glycerol ether (TTBG) are the three general ether compounds obtained through tert-butyl alcohol (TBA) etherification. Glycerol etherification with n-butanol results in the formation of glycerol ether products that are linked to the substituted butyl groups. These products include two mono-butyl glycerol ethers, two di-butyl glycerol ethers and a tri-butyl glycerol ether. Two mono-benzyl glycerol ether isomers, two di-benzyl glycerol ether isomers and tri-benzyl glycerol ether are the most reported results when benzyl alcohol is used as a solvent in the etherification reaction. The etherification of glycerol with 1-butene involves a series of equilibrium reactions to produce mono-ethers, di-ethers, and tri-ethers, whereas the etherification of glycerol with isobutene is carried out via tert-butylation of glycerol, yielding similar glycerol ether products when TBA is used as a solvent. As the by-product may be easily removed, the solvent-free glycerol etherification approach may have several advantages over the other conventional methods. Therefore, further studies on base-catalyzed glycerol etherification that employs a solvent-free reaction route may reveal a method for improving the conversion, selectivity, and yield of reaction products. This review study is crucial in improving knowledge of numerous mechanisms and how they relate to the effectiveness of the product’s catalytic process.

Dual-fuel engines fueled with n-butanol/n-octanol and n-butanol/DNBE: A comparative study of combustion and emissions characteristics

The dual-fuel combustion mode has drawn much attention due to its high thermal efficiency and low emissions. In this study, to realize the dual-fuel combustion, n-butanol was selected as the port-injected fuel (PIF); whereas two C8-biofuels, i.e., n-octanol and di-n-butyl ether (DNBE), were used as the direct-injected fuels, respectively. A comparative study between n-butanol/n-octanol and n-butanol/DNBE fueled dual-fuel engines in terms of their combustion and emissions characteristics was numerically carried out with the KIVA4-CHEMKIN code. The energy fractions of PIF varied from 0 to 0.4 at 1500 rpm and 2280 rpm. The results show that with the PIF increasing, the peak pressure and CO emissions increase, while the combustion duration gets shorter. Though adding more n-butanol contributes to a lower global fuel reactivity, the ignition delay is still shortened. Compared with the n-butanol/n-octanol engine, the n-butanol/DNBE engine exhibits a shorter ignition delay due to the high reactivity of DNBE. Also, it has a lower maximum pressure rise rate and longer combustion duration for its diffusion combustion phase. Consequently, a higher indicated thermal efficiency and much lower CO emissions are observed in the n-butanol/DNBE dual-fuel engine, with the expense of a slight increase in NOx emissions.

A Dual‐Phase Electrolyte for High‐Energy Lithium–Sulfur Batteries

AbstractDissolution of lithium polysulfides (LiPSs) is essential for fast cathode kinetics, but detrimental for anode stability, especially under lean electrolyte conditions. In this work, the phase separation phenomenon between solvents with different polarities (tetramethyl sulfone [TMS] and dibutyl ether [DBE]) is utilized to enable the design of a dual‐phase electrolyte. High‐polarity, high‐density TMS–lithium bis(trifluoromethanesulfonyl)imide–ammonium trifluoroacetate as the cathode electrolyte strongly solvates LiPSs, which propel the sulfur redox reaction. Moreover, the composite of DBE and a polymeric ion conductor serves as the anode electrolyte. The addition of DBE in the anode side effectively prevents the crossover of corrosive species (LiPSs and ammonia trifluoroacetate), enabling a significant improvement in Li‐metal anode stability. The electrode‐specific dual‐phase electrolyte design provides electrochemical performance superior to conventional electrolytes. Without additional electrode engineering, pouch cells assemble with the dual‐phase electrolyte cycle under a lean electrolyte (4 µL mg−1) and low‐Li‐excess condition (N/P = 3) for 120 cycles.

A comparative study on the combustion process and emissions formation of a CI engine fueled with isomers n-octanol and di-n-butylether

Two C8 biofuels, n-octanol (OCT) and di-n-butylether (DnBE), have attracted much attention due to their potential to replace diesel. In this work, compression ignition (CI) engines fueled by OCT and DnBE were numerically compared in terms of combustion characteristics and emissions formation. The KIVA4-CHEMKIN code package was used to model the combustion process in the cylinder. To realize detailed chemistry calculation, a multi-component reaction mechanism including OCT and DnBE was implemented in the code. Also, a mono-variate spherical soot model based on the moment projection method was integrated to handle the soot particle dynamics calculation. The engines fueled with OCT and DnBE were operated under the same condition. The comparison results suggest that the DnBE fueled engine exhibits a shorter ignition delay than the OCT fueled engine due to the rapid evaporation process and high cetane number of DnBE. As a result of earlier ignition, the DnBE fueled engine shows a mixing-controlled combustion regime and a longer combustion duration. The DnBE fueled engine generates more NO emissions because of its higher peak in-cylinder temperature and longer combustion duration. In the bowl region of the combustion chamber, a leaner mixture could be observed for the OCT fueled engine. Consequently, the OCT fueled engine produces less particle number and mass, but higher CO emissions.

Smoke point prediction of oxygenated fuels using neural networks

Smoke point (SP) is an important fuel property that characterizes the propensity of aviation jet fuels and kerosene to form soot. In the present study, an artificial neural network (ANN) model based on the artificial intelligence principle was developed to predict the SP of fuels with oxygenates (ethers and alcohols) and hydrocarbons (e.g., paraffins, olefins, naphthenes, aromatics, and their blends). An experimental dataset of 366 fuel mixtures comprising 113 pure compounds, 8 types of gasoline and diesels, and 245 fuel blends was used to improve the SP-prediction performance of the ANN model. One hundred and ten of the fuel blends used were various jet fuel surrogates collected from the literature. Experimental SP of 40 new mixtures consisting of diethyl ether, dibutyl ether, dioctyl ether, diphenyl ether, and methyl tert-butyl ether along with gasoline and diesel was measured as part of this work. The molecular composition of the fuels was expressed as the weight % of eight constituent functional groups present in the fuel. These functional groups along with two additional parameters (branching index and molecular weight) were provided as ten inputs to the model. The functional groups present in the gasoline and diesel samples were determined using high-resolution 1H nuclear magnetic resonance spectroscopy. The data were randomly split into three sets: training (70 %), validation (15 %), and test (15 %). The model was initially trained and validated simultaneously, and then; it was tested. A positive linear relation was observed between the measured and predicted SPs, as indicated by a correlation coefficient of 0.98. The mean absolute error of the predicted SP was 4.5. Results showed that the SP of the fuels depended on the aforementioned parameters that served as inputs for the model. The proposed model can be used to predict the SP of pure and blended form fuels containing the aforementioned functional groups.

Comparative study of perhydropolysilazane protective films

ABSTRACT Silicon dioxide thin films are a promising alternative to protective glass in solar cells. In this work, one-layer and four-layer thin films of a perhydropolysilazane (PHPS) were spin-coated from solution in dibutyl ether and cured by exposure to moderate temperatures or ultraviolet (UV) light to obtain glassy SiOx layers. Optical and morphological properties as well as their long-term stability were studied using XPS, FTIR, UV-Vis spectroscopy, and SEM microscopy with EDX analysis. The results showed that the process of converting PHPS layers to SiOx continues after the completion of the curing procedure for both methods. However, the composition of the thermally cured films is similar to silicon oxide, while the UV-cured samples demonstrate a composition similar to silicon dioxide due to differences in the reactions occurring during the curing process. The prolonged transformation process opens up possibilities for creating self-improving protective coatings based on PHPS.

Effect of diesel blended with di-n-butyl ether/1-octanol on combustion and emission in a heavy-duty diesel engine

Two kinds of C8 isomers, di-n-butyl ether (DNBE) and 1-octanol, as potential oxygen-containing alternative fuels, show important value in the trade-off between efficiency and emission. In the present work, the effects of DNBE/1-octanol with different proportions (0, 10%, and 20%) blended into diesel on the combustion characteristics, fuel economy, and emission characteristics in a six-cylinder heavy-duty diesel engine were studied at low, medium, and high loads. 1-Octanol with a 20% blending ratio showed different combustion characteristics in the cylinder compared with the other fuels. The economic analysis showed that the brake specific fuel consumption of DNBE–diesel blend fuels was higher than that of 1-octanol–diesel blend fuels, while brake thermal efficiency was the opposite tendency. The emissions of nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) were affected by the types of blend fuels, blending ratios, and loads. In comparison with 1-octanol–diesel blend fuels, the addition of DNBE in diesel promoted the emission of nitrogen oxides, but inhibited the emissions of soot, HC, and CO. DNBE– and 1-octanol–diesel blend fuels increased the weighted brake specific fuel consumption but decreased the weighted brake thermal efficiency compared with diesel in the World Harmonized Stationary Cycle test cycle of Euro VI regulation. The weighted NOx, HC, soot, and CO emissions of blend fuels depended on the types of blend fuels and blend ratios. The weighted NOx, HC, and soot emissions were reduced by blending 1-octanol into diesel, while the weighted CO emission was increased. The weighted CO and soot emissions of diesel blended with DNBE were reduced than that of diesel.

Prediction of emissions and performance of a diesel engine fueled with waste cooking oil and C8 oxygenate blends using response surface methodology

Extracting energy from waste and utilizing it as a transport fuel is a sustainable option to reduce fossil fuel dependency that could also give a solution to waste management. In the present study, used cooking oil from restaurant is collected and converted to biodiesel was later tested in a diesel engine along with three oxygenates viz., di-n butyl ether (DNBE), 2-ethyl-hexanol (TEH) and 1-octanol (OCT). This study aim to minimize the emissions of a diesel engine with these C8 oxygenates and also to provide a comparative analysis on the effects of their addition to the biodiesel individually on performance and emission of a single cylinder diesel engine. A response surface methodology (RSM) based optimization using a 3-factor × 3-level full factorial experimental design was employed to find the optimum combination of compression ratio, exhaust gas recirculation (EGR) and oxygenates with an objective to minimize NOx and smoke opacity with maximum performance. Three compression ratio (16:1, 17.5:1 and 19:1), three EGR rates (0%, 10% and 20%) and three fuel blends D80-WCOME15-DNBE5 (b) D80-WCOME15-TEH5 (c) D80-WCOME15-OCT5 were used. Multiple regression models developed using RSM for NOx, smoke opacity and BTE were found to be statistically significant. Interactive effects between compression ratio and EGR on responses for all blends were compared. From desirability approach, D80-WCOME15-OCT5 injected at compression ratio 19:1 with 10% EGR rate delivered optimum performance and emission characteristics with maximum desirability of 0.967.1-Octanol was found to be the best among di-n butyl ether and 2-ethyl-hexanol for this purpose. Confirmatory tests validated the models to be adequate with an error in prediction within 6%. With reference to diesel, D80-WCOME15-OCT5 injected at compression ratio 19:1 with 10% EGR rate reduced smoke opacity by 29.38% and increased NOx emissions by 4.07% with an improvement in BTE by 1.22%. With respect to D80-WCOME20, the same blend reduced smoke opacity by 34.7% and increased NOx emissions by 5.1% with 1.3% lower BTE.

Recoverable low fluorine content palladium complex-catalyzed Suzuki-Miyaura and Sonogashira coupling reactions under thermomorphic mode

The reaction of [PdCl2(CH3CN)2] and bis-5,5'-(RfCH2OCH2)-2,2′-bpy (1), where Rf = n-C4F8H, in the presence of dichloromethane (CH2Cl2) resulted in the synthesis of low fluorine content Pd complex, [PdCl2 [5,5′-bis-(RfCH2OCH2)-2,2′-bpy] (2). The Pd-catalyzed Suzuki-Miyaura and Sonogashira coupling reactions of several aryl halides with their respective reagents were selected to demonstrate the feasibility of catalytic activity and recycling usage with 2 as the catalyst by using dibutyl ether (DBE) as the solvent at 140–145 °C under the thermomorphic mode. The Pd complex 2-catalyzed Suzuki-Miyaura reactions of different aryl iodides with phenylboronic acid derivatives have showed good recycling results though its activity was observed to decrease after the fifth cycle. Similarly, 2-catalyzed Sonogashira reactions of several aryl iodides with phenyl acetylene have also displayed good recycling results for a total of up to 8 cycles, with a high yield and TON. The electronic effect studies from substituents in both Suzuki-Miyaura and Sonogashira coupling reactions showed that electron withdrawing groups on the aryl iodide speed up the reaction rate. Furthermore, the catalytic activity of the Pd complex (2) showed a better result with the more reactive aryl iodide compared to the less reactive aryl bromide and chloride. To our knowledge, this is the first example of recoverable low fluorine content Pd-catalyzed Suzuki-Miyaura and Sonogashira reactions under the thermomorphic mode.

Solvent selection criteria for temperature-resilient lithium–sulfur batteries

All-climate temperature operation capability and increased energy density have been recognized as two crucial targets, but they are rarely achieved together in rechargeable lithium (Li) batteries. Herein, we demonstrate an electrolyte system by using monodentate dibutyl ether with both low melting and high boiling points as the sole solvent. Its weak solvation endows an aggregate solvation structure and low solubility toward polysulfide species in a relatively low electrolyte concentration (2 mol L-1). These features were found to be vital in avoiding dendrite growth and enabling Li metal Coulombic efficiencies of 99.0%, 98.2%, and 98.7% at 23 °C, -40 °C, and 50 °C, respectively. Pouch cells employing thin Li metal (50 μm) and high-loading sulfurized polyacrylonitrile (3.3 mAh cm-2) cathodes (negative-to-positive capacity ratio = 2) output 87.5% and 115.9% of their room temperature capacity at -40 °C and 50 °C, respectively. This work provides solvent-based design criteria for a wide temperature range Li-sulfur pouch cells.

Combustion characteristics and emissions formation of a compression ignition engine fueled with C8 biofuels blends

ABSTRACT Energy scarcity and pollution problems have prompted researchers to search for renewable and clean energy sources for compression ignition (CI) engines. Two C8 biofuels, i.e., n-octanol and di-n-butylether (DnBE), are both promising to be the diesel fuel candidates because of their good ignition ability. However, their physical and chemical properties are different from each other. Thus, the combustion process of a CI engine could be optimized by manipulating the blending ratio of n-octanol and DnBE. In this work, to investigate the effects of n-octanol and DnBE blends on the combustion characteristics and emissions formation in a CI engine, the numerical investigation was carried out by the coupled KIVA4-CHEMKIN code. A multi-component reaction mechanism was implemented in the code to mimic the combustion of the fuels. Different DnBE/n-octanol blends were designed by varying the DnBE from 10% to 90% with an interval of 10% on an energy basis. Then the CI engine fueled with pure n-octanol, pure DnBE, and their blends was simulated at the engine speeds of 1500 rpm and 2280 rpm, respectively. Results suggest that blending more DnBE in octanol can shorten the ignition delay, increase peak pressure, mitigate pressure rise rate, and prolong the combustion duration. The emitted CO of the n-octanol fueled CI engine is high at both speeds. Blending DnBE in n-octanol can reduce CO emissions but inevitably leads to a rise in NO. More importantly, soot-free combustion can be achieved by fueling either n-octanol or DnBE. Finally, the optimal DnBE blending ratio is selected at 50%, of which IMEP can be improved by 6.12% and 6.9%, and CO can be reduced by 69.91% and 65.98% with acceptable increases in NO at 1500 and 2280 rpm, respectively. This implies that the optimization of CI engines can be achieved by adjusting the blending ratio of n-octanol and DnBE.

Acrylic acid conformers and their interactions with dibutyl ether

Fourier Transform Infrared spectra of pure acrylic acid (ARA), dibutyl ether, and their binary solutions at various acid concentrations have been recorded. Density functional theory calculations on ARA monomers and dimers have been carried out. In addition to the cis–cis and trans–trans dimers, cis–trans dimers also exist in liquid acid. The dimer ring formed by carboxyl group has an asymmetry. The experimental asymmetric and symmetric hydroxyl and carbonyl stretching bands have been assigned. Shifts suffered by the absorption bands in binary solutions have been analyzed in view of the formation of heteromolecular hydrogen bonds.