Cyclohexyl Formate Research Articles

Design and Synthesis of Free-Radical/Cationic Photosensitive Resin Applied for 3D Printer with Liquid Crystal Display (LCD) Irradiation.

In this work, aiming at a UV-curing 3D printing process with liquid crystal display (LCD) irradiation, a novel free-radical/cationic hybrid photosensitive resin was designed and prepared. After testing, the results showed that the acrylate monomers could be polymerized through a free-radical mechanism, while the epoxides were polymerized by a cationic curing mechanism. During the process of UV-curing, the acrylate and epoxide polymers were crosslinked and further locked together by non-covalent bonds. Therefore, an interpenetrating polymer network (IPN) structure could be formed through light-curing 3D-printing processes. Fourier transform infrared spectroscopy (FT-IR) revealed that the 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl formate and acrylic resin were both successfully involved in the UV-curing process. Furthermore, in order to make the 3D-printed objects cured completely, post-processing was of great importance. The results from the systematic study of the dynamic mechanical properties of the printed objects showed that the heating treatment process after UV irradiation was very necessary and favorable for the complete cationic polymerization of UV-6110 induced by Irgacure 261. The optimum heating treatment conditions were achieved at a temperature of 70 °C for 3 h.

Measurements and Correlation of Isobaric Vapor–Liquid Equilibria for the Binary Systems of Cyclohexanol + Cyclohexyl Formate and Cyclopentanol + Cyclopentyl Formate under Various Pressures

Data of vapor–liquid equilibria are essential in the design of a separation unit in the technology of cyclic alkene indirect hydration in the presence of formic acid. This work aims at measuring th...

The rotational spectrum of cyclohexyl formate, chemically prepared within a supersonic expansion

The pulsed supersonic jet expansion microwave spectra of the parent and of the CD=O monodeuterated species of cyclohexylformate have been measured in the 6.5–18 GHz range. The samples have been obtained by direct esterification of HCOOH (or DCOOH) with cyclohexyl alcohol during a supersonic expansion in a microwave cavity. Most of the observed transitions are split into two component lines, due to the tunnelling motion connecting two equivalent gauche forms. The tunnelling barrier has been determined to be B2 = 267 (10) cm−1. Structural information has been obtained from the 6 available rotational constants.

Effect of Crystal Form Control on Improving Performance of Cu3(BTC)2 Immobilized Phosphotungstic Acid in Esterification of Cyclohexene with Formic Acid

The esterification of cyclohexene with formic acid is the first step for indirect hydration to cyclohexanol. In the work reported in this study, phosphotungstic acid (HPW) was incorporated into the metal–organic framework Cu3(BTC)2 through a one-step hydrothermal synthesis method to catalyze the esterification reaction. The crystal structure of composite HPW–Cu3(BTC)2 was modulated during the preparation process to convert the catalyst from the {111} crystal facets of the original regular octahedral structure to the {100} crystal facets of the cubic structure using p-toluic acid (pTA) as the regulator. The conversion of the crystal facets reduces the formation through holes while exposing more active sites of HPW. When the mass ratio of the modulator to the organic ligand terephthalic acid was 20, the crystal facets of the catalyst were completely covered by the {100} crystal facets. After the crystal transformation, the conversion of cyclohexene was increased to 86.8%, and the selectivity of cyclohexyl formate was 84.2%. Agglomeration occurred after the catalyst was used twice in the esterification reaction. HPW was incorporated into the metal-organic framework Cu3(BTC)2 through a one-step hydrothermal synthesis method and used for catalyzing the esterification reaction of cyclohexene with formic acid. The crystal structure of composite HPW–Cu3(BTC)2 was modulated during the preparation process to convert the catalyst from the {111} crystal facets of the original regular octahedral structure to the {100} crystal facets of the cubic structure using p-toluic acid (pTA) as the modulator.

Mechanisms for the formation of ester compounds in the liquid-phase oxidation of cyclohexane

The channels of formation of ester compounds in the liquid-phase oxidation of cyclohexane are reviewed. At least 99.8% cyclohexyl esters of mono- and dicarboxylic acids are formed as a result of cyclohexanol acylation with mixed anhydrides including residues of all compounds with carboxyl groups present in the oxidized cyclohexane. The formation of mixed anhydrides is related to the fast reacylation of adipic anhydride with carboxylic acids. Alcoholysis of mixed anhydrides containing the formic acid residue with cyclohexanol leads mainly to cyclohexyl formate. The formation of e-caprolactone during cyclohexane oxidation is the result of the Baeyer–Villiger oxidation of cyclohexanone with peroxy acids through α-hydroxy-α-hydroperoxy ester. A decrease in the yield of e-caprolactone is reached under the conditions of decomposition or reduction of peroxy acids in the presence the compounds of variable valency metals or sulfur-containing reagents, respectively. The cobalt(II) and manganese(II) compounds stimulate the homolytic decomposition of α-hydroxy-α-hydroperoxy ester during which no lactone is formed. The cyclization of 5-hydroxypentanoic acid, which was formed by the oxidative transformations of cyclohexanone, leads to δ-valerolactone. The compounds of variable valency metals slightly affect the yield of δ-valerolactone. The mechanism of ester formation associated with the acylation of oxiranes formed by the radical chain oxidation of carbonyl compounds at the β-CH bonds was proposed.

Measurements and Correlation of Liquid–Liquid Equilibria for the Ternary System Cyclohexanol + Water + Cyclohexyl Formate at 298.2–338.2 K

Cyclohexanol is an important intermediate in production of adipic acid and e-caprolactam. On the industrial scale, cyclohexanol is produced by several methods that suffer from considerable drawbacks, such as a low conversion of the initial substance, low selectivity of the process, or explosion risks in the oxidation unit. To design a new process of indirect hydration of cyclohexene in the presence of formic acid, it is necessary to know the given system properties. In this paper, the data of liquid–liquid equilibrium (LLE) are presented for the system of cyclohexanol + water + cyclohexyl formate under atmospheric pressure and within a temperature range from 298.2 to 338.2 K. The experiments were conducted in a temperature-controlled glass cell and the received data were correlated with the nonrandom two-liquid (NRTL) and universal quasichemical equations in order to obtain binary interaction parameters describing LLE of the given system. The measured data accuracy was specified by the Bachman and Othmer–...

Phosphotungstic acid immobilized on sulphonic-acid-functionalized SBA-15 as a stable catalyst for the esterification of cyclohexene with formic acid

Abstract Phosphotungstic acid (HPW) was immobilized on a sulphonic-acid-functionalized SBA-15 mesoporous molecular sieve through a one-step hydrothermal synthesis method, using non-ionic surfactant pluronic P123 as a structure-directing agent in acidic media, tetraethoxysilane (TEOS) as a silicon source and 3-trimethoxysilyl-1-propanethiol (MPTMS) with hydrogen peroxide (H2O2) oxidized to a sulfonic acid group. The obtained composite material HPW-SBA-15-SO3H has a high specific surface area, large pore volume and increased strong acidity. The effect of raw-material ratio on the catalyst was investigated. Catalysts that were prepared under optimal conditions of a molar ratio of (MPTMS)/ (MPTMS + TEOS) of 1:10, a molar ratio of (H2O2)/(MPTMS) of 18:1 and a mass ratio of (HPW)/(TEOS) of 1:10 exhibited an excellent catalytic activity in the esterification reaction of cyclohexene with formic acid. The cyclohexene conversion exceeded 86.7% and the cyclohexyl formate selectivity was 98.1% after 6 h at 353 K with a mole ratio of cyclohexene to formic acid of 1:3 and a catalyst dosage of 5.7% (w/w). The composite catalyst had a higher catalytic stability than the sulfonic-acid-functionalized SBA-15 and SBA-15-immobilized HPW individually. The cyclohexene conversion reached 72.0% even after reused four times. Fourier transform infrared and temperature-programmed desorption of ammonia revealed that a strong interaction existed between the sulfonic-acid group and the HPW, which prevented acid-active component of HPW and sulfonic-acid group loss from the carrier.

Integrated reaction and separation in a continuous middle vessel column for enhancing indirect hydration of cyclohexene to cyclohexanol

This study introduced economically-viable continuous reactive distillation (RD) design alternatives for cyclohexanol production through the indirect hydration of cyclohexene. The feasibility concept of batch RD was employed for generating the new design alternatives. The first alternative process utilized a continuous stripper for recovering the stable node product of cyclohexyl formate in the esterification reaction and then employed a continuous middle vessel column (MVC) for recovering the stable and unstable node products of cyclohexanol and formic acid in the hydrolysis reaction. The second design had a single MVC-type column having the reactive rectifying zone and the middle vessel reactor for the two respective reactions. The simulation results showed the two alternative sequences required less energy duty than the previously proposed RD process. However, compared to the prior RD process, the life cycle cost (LCC) of the first alternative design increased about 30% due to high equipment costs and the LCC of the second process decreased nearly 40% because of low equipment costs and energy requirements.

Synthesis of Different Shapes ZnFe₂O₄–BiOCl Nanocomposites for Photocatalytic Reduction of CO₂ in Cyclohexanol.

Nanosheet and hierarchical microsphere nanostructures of ZnFe₂O₄–BiOCl nanocomposites with various ZnFe₂O₄ contents were prepared through hydrothermal deposition method. The morphology and structure of the as-prepared samples were systematically characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, Brunauer-Emmert-Teller method, and photoluminescence spectra. The photocatalytic activities of the two different shapes of ZnFe₂O₄–BiOCl composites have been evaluated by photocatalytic reduction of CO₂ in cyclohexanol under UV light irradiation. The results showed that cyclohexanol was oxidized to cyclohexanone (CH), and CO₂ was reduced and then reacted with cyclohexanol to produce cyclohexyl formate (CF). The ZnFe₂O₄–BiOCl composites with different shapes showed much higher CF and CH yields than those of pristine BiOCl and mechanically mixed samples, respectively. When the ZnFe₂O₄ content in the composites reached 9%, two different shapes of ZnFe₂O–BiOCl composites both achieved the highest photocatalytic activities. In contrast, the activities for photocatalytic reduction of CO₂ in cyclohexanol over hierarchical microsphere ZnFe₂O₄–BiOCl composites were higher than those of nanosheet structure samples. The higher activities over hierarchical microsphere composites could be attributed to its unique hierarchical structure, large illumination area, and low Photoluminescence (PL) emission intensity, which were beneficial for the separation of photogenerated charge carriers. This work provided a novel approach for the design and construction of highly efficient photocatalyst and reaction system for photoreduction of CO₂.

ZnFe2O4 deposited on BiOCl with exposed (001) and (010) facets for photocatalytic reduction of CO2 in cyclohexanol

ZnFe2O4-BiOCl composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CO2 in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFe2O4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the directprecipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to ∙CO 2 - . The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe2O4-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.

Esterification of cyclohexene with formic acid over a peanut shell-derived carbon solid acid catalyst

A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and elemental analysis, which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations. Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g. The carbon solid acid catalyst showed better performance than HZSM-5 for the esterification of cyclohexene with formic acid. At a 3:1 molar ratio of formic acid to cyclohexene, catalyst loading of 0.07 g/mL of cyclohexene, and reaction time of 1 h at 413 K, the cyclohexene conversion was 88.4% with 97.3% selectivity to cyclohexyl formate. The carbon solid acid catalyst showed better reusability than HZSM-5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene, which deactivated HZSM-5. The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing –SO3H groups and then it remained constant in the following reuse.

Photocatalytic reduction of carbon dioxide over ZnFe2O4/TiO2 nanobelts heterostructure in cyclohexanol

A series of ZnFe2O4/TiO2 heterostructure photocatalysts with different mass percentages of ZnFe2O4 were synthesized through hydrothermal deposition method. The photocatalysts were characterized by SEM, TEM, XRD, XPS, and UV–vis DRS techniques. It is observed that ZnFe2O4 nanoparticles grew on the TiO2 nanobelts, and the obtained nanocomposites have ordered nanobelt structure with a high crystallinity. The photocatalytic activities of the nanocomposites were tested by photocatalytic reduction of CO2 in cyclohexanol under UV light (main wave length at 360nm) irradiation. The experimental results showed that the main products were cyclohexanone (CH) and cyclohexyl formate (CF). Compared with pure TiO2 and ZnFe2O4 samples, the obtained ZnFe2O4/TiO2 nanocomposites showed much higher photocatalytic performance. The loading amount of ZnFe2O4 was an important factor affecting the generation yields of the products. When the loading amount of ZnFe2O4 reached 9.78%, the ZnFe2O4/TiO2 heterostructure sample displayed the highest activity. The Z-scheme system reaction mechanism was proposed to explain the photocatalytic activity of the ZnFe2O4/TiO2 heterostructure sample.

Photocatalytic reduction of CO2 in cyclohexanol on CdS–TiO2 heterostructured photocatalyst

A nanosheet of CdS–TiO2 with heterojunction was prepared by a two-step hydrothermal synthesis method and used as a photocatalyst for reducing CO2 in cyclohexanol. This heterostructured composite has been characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy (DRS). The activity of the CdS–TiO2 composite was tested in a batch slurry bed reactor. The results showed that CO2 absorbed in cyclohexanol was reduced to cyclohexyl formate (CF) on conduction band and the absorbent cyclohexanol was oxidized to cyclohexanone (CH) on valance band of the photocatalyst. It was revealed that the highest formation rates of 20.2μmol/(gcath) and 20.0μmol/(gcath) for CF and CH could be obtained when TiO2/CdS with the molar ratio of 8 was used. Overall, this work provides a novel pathway for photocatalytically reducing CO2 and preventing the catalyst from photocorrosion.

Development of a Novel Catalytic Distillation Process for Cyclohexanol Production: Mini Plant Experiments and Complementary Process Simulations

A new, two-step process concept for the production of cyclohexanol by indirect hydration of cyclohexene using formic acid as a reactive entrainer is suggested, and its principle technical feasibility is demonstrated. The first step of this process is based on an ester formation reaction of cyclohexene with formic acid. This reaction was carried out in a mini plant stainless steel catalytic distillation column of 2.35 m height. The column was packed with noncatalytic structured packings (SULZER-DX) and catalytic structured packings (KATAPAK-S). The experiments were conducted under low-pressure conditions (<0.6 bar) to avoid formic acid decomposition. Concentration and temperature profiles were obtained under steady-state conditions. Up to 98.3% conversion of cyclohexene and 75.5 mol % ester concentration in the bottom product of the column was obtained. In a similar manner, the second step of the process, i.e. the hydrolysis of the cyclohexyl formate formed in the first step, was investigated experimentall...

Formation of formic acid and cyclohexyl formate in oxidation of cyclohexane

The consistency of the suggested mechanisms of formic acid formation with the composition of products formed in the industrial process of cyclohexane oxidation was examined. The role of formic acid in the formation of cyclohexyl esters of mono-and dicarboxylic acids was elucidated.

On the difference between isobaric and isochoric heat capacities of liquid cyclohexyl esters

The isobaric heat capacities and densities are determined for cyclohexyl formate (CHF), cyclohexyl acetate (CHA), cyclohexyl propionate (CHP), cyclohexyl butyrate (CHB), and cyclohexyl valerate (CHV). The speed of sound in liquid cyclohexyl acetate is also measured. The approach to evaluate the isochoric heat capacities of the liquids using the enthalpies of vaporization and the molar volumes is proposed. The isochoric heat capacities of the liquid esters are found from the above data. The ( C p− C v) differences for the esters are calculated using the lattice model.

Comprehensive Study of Vapor Pressures and Enthalpies of Vaporization of Cyclohexyl Esters

Vapor pressures and standard molar enthalpies of vaporization were determined for five cyclohexyl esters: cyclohexyl formate, cyclohexyl acetate, cyclohexyl propanoate, cyclohexyl butyrate, and cy...

Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene in batch and distillation column reactors: ion-exchange resins as catalysts

Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene was carried out in the presence of cation-exchange resins as catalysts. Effect of various parameters, e.g. speed of agitation, catalyst particle size, catalyst loading, types of catalyst, temperature, mole ratio of the reactants, was studied to optimise the reaction conditions. The reaction of formic acid, with different concentrations in aqueous solutions, with cyclohexene was studied. Experiments were carried out in the presence of homogeneous catalyst, p-toluene sulphonic acid ( p-TSA), to compare results with the heterogeneous catalyst. A comparison of anhydrous esterification between acrylic acid and that of methacrylic acid with cyclohexene has been reported. The conversion of formic acid in aqueous solutions to cyclohexyl formate, by reaction with cyclohexene, in a distillation column reactor (DCR), packed with an acidic ion-exchange resin catalyst was studied; the effect of variables such as feed flow rate, molar ratio of reactants, amount of catalyst in the reboiler, concentration of formic acid, location of the feed point, etc., was studied. A comparison between the rate of esterification of formic acid with cyclohexene in batch mode and in distillation column reactor has been made. An attempt was also made for the selective esterification of formic acid with cyclohexene from a mixture of formic acid and acetic acid in a DCR.

Study on insect-repellent components in the volatile oils castor leaves

This paper studied the insect-repellent components from castorleaves. By Gc-Ms and UV, IR analysis, four components were identified: 2-hexanal, cyclohexyl formate, 5-methyl hexanal, 4,4-dimethyl hexanal, among them, 2-hexanal was the main insect-repellent component.

Alumina‐ and Y‐zeolite‐catalyzed reaction of cyclohexanol with tert‐butylhydroperoxide

AbstractThe use of γ‐alumina and exchanged Y‐zeolites as catalysts in the liquid‐phase oxidation of cyclohexanol by tert‐butyl hydroperoxide (tBHP) has been studied. With γ‐alumina, cyclohexanone is formed, whereas the zeolites NaCeY and NaLaY give cyclohexyl formate as the main product. This compound is thought to originate from a zeolite‐mediated rearrangement of tBHP to acetone and methanol, oxidation of methanol to formic acid and electrophilic addition of formic acid to cyclohexene (formed in situ from cyclohexanol).