In the production of purified terephthalic acid (PTA), the acetic acid solvent dehydration system is a typical heterogeneous azeotropic distillation system. In this work, a rigorous process simulation of the complete industrial acetic acid solvent dehydration process is conducted. To achieve both the bottom- and top-product specifications, remove the accumulated p-xylene (PX), and recycle the methyl acetate (MA) despite feed flow rate disturbances, a suitable control strategy of this complete system is proposed. The control strategy requires only a side draw and organic reflux to control the tray temperatures of the dehydration column, the bottom heating steam to control the tray temperature of the PX purification column, and top-product reflux to control the tray temperature of the entrainer recovery column; this strategy can be easily implemented in industry for wider applications. From dynamic simulation and analysis, the control strategy can maintain the product purities, overcome the drawback of the PX imbalance, achieve the transition to the desired operation more quickly, and better maintain the stability of the overall solvent dehydration system under a disturbance in the upper-zone feed streams.

Surface-functionalized magnetic nanoparticle supported dual Brønsted acidic ionic liquid was synthesized by immobilizing 1-(propyl-3-sulfonate) imidazolium hydrogen sulfate [SO3H-(CH2)3-HIM][HSO4] onto the surface of Fe3O4@SiO2 using 3-chloropropyltrimethoxysilane as the “linker”. The structure of the catalyst was characterized by XRD, FT-IR, SEM, TEM, and VSM. The results demonstrated that the Fe3O4 particle was well retained in the silica matrix, presenting a core–shell structure with strong magnetic responsiveness. Meanwhile, the ionic liquid was successfully immobilized on the support. The as-prepared catalyst could disperse well in the reactants and showed good performance in esterification of oleic acid with short-chain alcohols and transesterification of soybean oil. Moreover, the catalyst could be easily separated from products by additional magnetic force without obvious mass loss and maintain satisfactory catalytic activity after being recycled eight times.

La1−xCexCrOδ (0 ≤ x ≤ 0.3) composite oxides with three-dimensionally ordered macroporous (3DOM) structures were constructed by a colloidal crystal template method and characterized via XRD, FT-IR, FESEM, N2 adsorption–desorption, XPS, H2-TPR, and O2-TPD techniques. The catalytic performances of the as-prepared samples for soot oxidation were further evaluated. In the case of unsubstituted species, the crystal size of LaCrO3 increased with the increasing calcination temperature, which resulted in the destruction of the 3DOM structure. The introduction of Ce delayed the crystal phase transition from LaCrO4 monazite to LaCrO3 perovskite and inhibited the growth of the crystal size; thus, the collapse of the 3DOM structure was inhibited. Moreover, the concentration of active and lattice oxygen species was further enhanced. The optimization of the structure and intrinsic properties of the catalyst impels the enhancement of its catalytic performance for soot removal.

•K and Mn loaded on 3DOM La0.8Ce0.2FeO3 was successfully prepared.•The presence of K and Mn increased the concentration of active oxygen species.•The introduction of K and Mn enhanced the redox property of the catalyst.•The K–Mn/3DOM La0.8Ce0.2FeO3 catalyst could lower T50 of soot to 377 °C.Three-dimensionally ordered macroporous (3DOM) La0.8Ce0.2FeO3 perovskite was successfully constructed through a colloidal crystal template way. And the K–Mn/3DOM La0.8Ce0.2FeO3 catalyst was obtained by an incipient-wetness impregnation method. The physicochemical characterizations of the material were conducted by means of XRD, FESEM, TEM, N2 adsorption–desorption, H2-TPR, XPS and O2-TPD techniques, and the catalytic performance was evaluated for soot removal. The intact well-ordered macroporous skeleton was remained after K and Mn were loaded, which offered an ideal environment for soot combustion. The generated K2Mn4O8 was well decorated on the skeleton of the 3DOM perovskite, which could increase the concentration of surface oxygen species and enhance the reducibility of catalyst. The as-prepared catalyst exhibited good catalytic performance for soot removal, and could lower the T50 of soot to 377 °C.Download high-res image (157KB)Download full-size image

Three-dimensionally ordered macroporous (3DOM) La0.8Ce0.2Mn1−xFexO3 perovskites were successfully prepared by a colloidal crystal template method and KNO3-supported 3DOM La0.8Ce0.2Mn1−xFexO3 catalysts were prepared by a wetness impregnation method. Physicochemical properties of these catalysts were characterized by XRD, FT-IR, FESEM, TEM, BET, H2-TPR, O2-TPD, and XPS techniques and their catalytic performances were evaluated by soot combustion. All these perovskites possessed a well-ordered 3DOM structure, and KNO3 was highly dispersed on the skeleton of the supporters without changing the morphology and crystal structure of the perovskites. The 3DOM structure provides an increased contact area between the catalyst and soot. Besides, partial replacement of Mn by Fe into the perovskites increased the surface area and reducibility. The introduction of K ions increased the amount of active oxygen species in the catalysts, which could accelerate soot combustion at low temperature. On the other hand, the NO3− species brought by KNO3 were beneficial to the reaction at high temperature. Among all the samples, the 3DOM K/La0.8Ce0.2Mn0.6Fe0.4O3 exhibited the highest catalytic performance with the lowest T50 at 379 °C.

A magnetically recyclable catalyst was prepared by embedding magnetic nanoparticle in poly(phosphotungstate-based ionic liquid) matrix. The obtained hybrid material was characterized by XRD, FT-IR, SEM, TEM, TGA, and VSM. The results indicated that Fe3O4 was successfully implanted in multilayer poly(ionic liquid), and the catalyst possessed open active sites (see SEM) to reactants and a high magnetization value. The combination of poly(ionic liquid) matrix with magnetic nanoparticle enhanced the structure stability and favored the separation performance. Esterification of oleic acid with ethanol was conducted in the presence of prepared catalyst, and the Box–Behnken response surface methodology was applied for maximizing the oleic acid conversion by optimizing process variables at 90 °C. Under the optimum conditions (reaction time, 5 h; catalyst amount, 13 wt %; alcohol/acid molar ratio, 12:1), the conversion of oleic acid reached 93.4%. Besides, the catalyst presented fine reusability after six runs and could be facilely recovered in magnetic field based on its superparamagnetism property.

A novel heterogeneous catalyst [HVIm-(CH2)3SO3H]HSO4@HKUST-1 (IL@HKUST-1), with both Lewis and Brønsted acid sites, was developed for the esterification of oleic acid with short-chain alcohols. HKUST-1 was chemically modified with ethanedithiol, and the vinyl-containing ionic liquid was then grafted onto the carrier through thiol groups. The catalyst IL@HKUST-1 was characterized by XRD, N2 adsorption–desorption, FT-IR, SEM, TG, elemental analysis, and ICP. The results proved that HKUST-1 had typical microporous structure, and the thiol groups were incorporated into the channels of the carrier. Through the reaction of vinyl and thiol, the ionic liquid was successfully immobilized onto SH-HKUST-1 by chemical covalent bonds. The catalyst was applied in the esterification of oleic acid with ethanol, and the optimal conditions were determined as follows: molar ratio of ethanol to oleic acid 12:1, catalyst amount 15 wt% (based on oleic acid), reaction time 4 h, and reaction temperature 90 °C. Under the conditions, the conversion of oleic acid was 92.1%. After 5 times of recycling, there was no significant decrease in conversion, showing a certain stability and good reusability of the catalyst. The catalyst also exhibited high catalytic activity in esterification of oleic acid with other short-chain alcohols.

Isobaric binary vapor–liquid equilibrium (VLE) data for diethyl carbonate with ethylbenzene and xylene isomers are measured at 101.33 kPa by using a modified Rose still. The binary VLE data are tested to be thermodynamically consistent by the Herington method and the point-to-point test of the Fredenslund method. Taking account of the nonideality of the vapor phase, the activity coefficients of the components are calculated. All systems present a positive deviation from ideality. The experimental VLE data are well correlated by the nonrandom two-liquid (NRTL), universal quasichemical activity coefficient (UNIQUAC), and Wilson equations. The calculated vapor-phase compositions and temperature agree well with the experimental values. These experimental data can provide basic thermodynamic data for practical application in developing the distillation simulation of diethyl carbonate with ethylbenzene and xylene isomers.

•The catalyst possessed macropore and multi-layered ionic liquid matrix.•Fe3O4 was applied as hard template for the first time.•A high biodiesel yield of 92.6% was obtained under mind conditions.•The catalyst allowed for a convenient separation with good reusability.An efficient poly (ionic liquid) catalyst for biodiesel production was synthesized from Brønsted acidic ionic liquid 1-vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate [VSIM][HSO4] through free radical polymerization from a novel approach, where Fe3O4 particles acted as hard template. The template could be easily removed in short time and macrospores formed after the removal of Fe3O4. The structure of the polymer was characterized by different techniques and the results demonstrated that the macroporous polymeric network was multi-layered and exhibited repeating units of SO3H and HSO4 with fine separation efficiency, as a novel heterogeneous acidic catalyst. The catalytic performance of the macroporous polymer was assessed in the esterification reaction of oleic acid for biodiesel production and the Box-Behnken response surface methodology (RSM) was applied for maximizing the biodiesel yield by optimizing process variables at 80 °C. Under the optimum conditions (reaction time was 4.5 h, catalyst amount was 8.5 wt%, and alcohol/acid molar ratio was 12:1), a high biodiesel yield of 92.6% was obtained. The polymeric catalyst also showed favorable reusability after six runs. The combination of macrospores with poly (ionic liquid) would significantly reduce the limitation of mass transfer in biodiesel production compared with other porous solid acidic catalysts.Multi-layered macroporous poly (ionic liquid) with repeating catalytic units proves to be a novel and efficient heterogeneous acidic catalyst for biodiesel production.

A magnetically recyclable and efficient catalyst for biodiesel synthesis was fabricated by confining the Brønsted ionic liquid 1,4-butanediyl-3,3′-bis(3-sulfopropyl) imidazolium dihydrogensulfate in an amino-functionalized magnetic metal–organic-framework composite (Fe3O4@NH2-MIL-88B(Fe)) through a simple and efficient strategy via the amino groups. The catalyst was systematically characterized, proving ionic liquid was grafted in the amino-functionalized carrier, and the catalyst was spindle-shaped with superparamagnetism (7.2 emu/g). The prepared catalyst with high acidity (1.76 mmol H+ g–1) exhibited good catalytic activity in biodiesel synthesis from oleic acid and ethanol with a yield of 93.2%, optimized by Box-Behnken response surface methodology. The fine catalytic performance of the catalyst was mainly due to the combination of the characteristics of the ionic liquid and the structure of Fe3O4@NH2-MIL-88B(Fe). Moreover, the catalyst was recycled without significant loss of activity after being used for six runs and could be magnetically separated in magnetic force without obvious mass loss.

The reaction kinetics of the transesterification of methyl acetate with n-propanol is described by pseudohomogeneous (PH) kinetic model, which can successfully correlate with the experimental data. The influence of temperature as well as catalyst loading and initial molar ratio of n-propanol to methyl acetate on this reaction is studied under the condition of eliminating both internal and external mass transfer resistances. On the basis of the PH kinetic model, the influences of design parameters are studied, such as recycle flow rate, the number of stages of the reactive distillation column (RD), and theoretical stages of the conventional distillation column. These parameters are further optimized to minimize total annual cost in the RD process.

Isobaric vapor–liquid equilibrium (VLE) data for the sec-butyl acetate + acetic acid binary system, as well as the sec-butyl acetate + acetic acid + water ternary system, were measured at 101.33 kPa using a modified Rose still. The second virial coefficients and apparent fugacity coefficients were calculated to analyze the nonideal behavior in vapor phase caused by the association of acetic acid, which were corrected by the chemical theory and Hayden–O’Connell method. The binary experimental data were tested for thermodynamic consistency by the Herington method and the point-to-point test and correlated by the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models using the nonlinear least-squares method. The model parameters of the binary system were used to correlate the ternary VLE data. The ternary correlated values obtained in this way agreed well with the experimental values.

Three-dimensionally ordered macroporous (3DOM) La0.8Ce0.2Mn1−xFexO3 perovskites were successfully prepared by a colloidal crystal template method and KNO3-supported 3DOM La0.8Ce0.2Mn1−xFexO3 catalysts were prepared by a wetness impregnation method. Physicochemical properties of these catalysts were characterized by XRD, FT-IR, FESEM, TEM, BET, H2-TPR, O2-TPD, and XPS techniques and their catalytic performances were evaluated by soot combustion. All these perovskites possessed a well-ordered 3DOM structure, and KNO3 was highly dispersed on the skeleton of the supporters without changing the morphology and crystal structure of the perovskites. The 3DOM structure provides an increased contact area between the catalyst and soot. Besides, partial replacement of Mn by Fe into the perovskites increased the surface area and reducibility. The introduction of K ions increased the amount of active oxygen species in the catalysts, which could accelerate soot combustion at low temperature. On the other hand, the NO3− species brought by KNO3 were beneficial to the reaction at high temperature. Among all the samples, the 3DOM K/La0.8Ce0.2Mn0.6Fe0.4O3 exhibited the highest catalytic performance with the lowest T50 at 379 °C.

La1−xCexCrOδ (0 ≤ x ≤ 0.3) composite oxides with three-dimensionally ordered macroporous (3DOM) structures were constructed by a colloidal crystal template method and characterized via XRD, FT-IR, FESEM, N2 adsorption–desorption, XPS, H2-TPR, and O2-TPD techniques. The catalytic performances of the as-prepared samples for soot oxidation were further evaluated. In the case of unsubstituted species, the crystal size of LaCrO3 increased with the increasing calcination temperature, which resulted in the destruction of the 3DOM structure. The introduction of Ce delayed the crystal phase transition from LaCrO4 monazite to LaCrO3 perovskite and inhibited the growth of the crystal size; thus, the collapse of the 3DOM structure was inhibited. Moreover, the concentration of active and lattice oxygen species was further enhanced. The optimization of the structure and intrinsic properties of the catalyst impels the enhancement of its catalytic performance for soot removal.