Dehydration Of Acid Research Articles

Feasibility of zeolites in converting butyric acid into propylene for biorefineries

ABSTRACTThe biorefinery has been recognized as a new industry to produce both energy and chemical materials such as olefins and BTX from renewable resources. In this context the conversion of butyric acid over zeolites was investigated for establishing a new production route of propylene. Propylene was mainly generated by decarbonylation and dehydration of butyric acid. Our study proved that H-ZSM-5 (750) and silicalite were the best industrial catalyst among the tested ones. For H-ZSM-5 (750), the selectivity of propylene reached 64.2 C% and the ratio of the yield for propylene to theoretical yield (75 C%) became 85.6%.

Process optimization of an industrial acetic acid dehydration progress via heterogeneous azeotropic distillation

Abstract The simulated process model of the HAc dehydration process under actual overloaded condition was conducted by amending the model of standard condition in our previous work using the process data collected from actual production. Based on the actual process model, the operation optimization analysis of each plant (HAc dehydration column, decanter and NPA recycle column) was conducted using Residue Curve Maps (RCMs), sensitivity analysis and software optimization module. Based on the optimized parameters, the influence of feed impurity MA and the temperature of decanter on the separating effect and energy consumption of the whole process were analyzed. Then the whole process operation optimizing strategy was proposed with the objective that the total reboiler duty QTotal of C-1 and C-3 reaches the minimum value, keeping C-1 and C-3 at their optimized separation parameters obtained above, connecting all the broken recycle and connection streams, and using the temperature of D-1 as operation variable. The optimization result shows that the total reboiler duty QTotal of the whole process can reach the minimum value of 128.32 × 106 kJ·h− 1 when the temperature of decanter is 352.35 K, and it can save 5.94 × 106 kJ·h− 1, about 2.56 t·h− 1 low-pressure saturated vapor.

PVA modified filled copolymer membranes for pervaporative dehydration of acetic acid-systematic optimization of synthesis and process parameters with response surface methodology

The separation potential of acrylic copolymer membrane was significantly improved by modifying it with polyvinyl alcohol (PVA) and nano sized sodium montmorillonite (NaMMT) clay. Accordingly, several membranes were prepared from the polymers synthesized by emulsion polymerization of acrylonitrile (AN) and acrylic acid (AA)in the presence of varied concentrations of PVA and NaMMT clay in the reaction mixtures. The synthesis parameters, i.e., comonomer ratios, wt% of PVA and wt% of clay were optimized by three level factorial design of response surface methodology (RSM) with respect to flux and separation factor for 90wt% acetic acid in water. The membrane prepared with optimized synthesis parameters, viz., with AN: AA molar ratio of 5:1, PVA and clay of 5wt% each (of total monomer wt.) was further subjected to dehydration of acetic acid at varied process conditions, i.e., feed concentration, temperature and downstream pressures. The process parameters were also optimized with similar RSM. The optimized membrane showed long time stability with high flux and separation factor, i.e., 0.520kg/m2h and 203, respectively for 90wt% acid in water at 30°C and 1.5 kPa downstream pressure.

Efficient Conversion of Bio‐Lactic Acid to 2,3‐Pentanedione on Cesium‐Doped Hydroxyapatite Catalysts with Balanced Acid–Base Sites

AbstractWe report the design and synthesis of cesium‐doped hydroxyapatite for direct and high‐yield conversion of biobased lactic acid to 2,3‐pentanedione (72.3 %). Cs species derived from CsNO3 at high temperature of calcination is introduced into the hydroxyapatite structure to regulate its acid–base properties. It is found that a balance of acid–base chemistry favors the condensation of lactic acid to 2,3‐pentanedione. As a result, the undesired reactions such as lactic acid dehydration, decarbonylation, and coking are suppressed. Instead, a concerted catalysis between surface basic site and acidic site for lactic acid condensation to 2,3‐pentanedione dominates on the cesium‐doped hydroxyapatite catalyst, leading to a highly selective process for direct conversion of bio‐lactic acid to 2,3‐pentanedione.

Charge transfer and recombination kinetics at WO3 for photoelectrochemical water oxidation

The photoelectrochemical properties of nanostructured, porous WO3 films deposited by screen printing have been characterized by steady-state and small signal modulation methods as a function of film thickness. Monoclinic WO3 with a wide particle size distribution between 50 and 500 nm was synthesized by a very simple method, via the dehydration of tungstic acid. Related to the open morphology and relatively large feature sizes, the optimal thickness for light harvesting and current collection is about 12 μm for front-side and about 20 μm for backside illumination. Intensity-modulated photocurrent spectroscopy (IMPS) shows that the rate constant for charge transfer to the electrolyte solution is larger than that for surface recombination in most of the applied potential range, illustrating the promise of the material. However, charge collection is found to be an important process that can limit the photocurrent, especially for thicker electrodes in the photocurrent onset potential region.

An All-Purpose Porous Cleaner for Acid Gas Removal and Dehydration of Natural Gas

In this issue of Chem , Mohamed Eddaoudi and co-workers report a novel but simple crystalline porous superstructure that effectively removes all acidic gases and water from natural gas without taking any damage from the reactive guests.

Dehydration of Lactic Acid: The State of The Art

AbstractThe dehydration of lactic acid to produce acrylic acid is a renewable alternative to the mostly used production of acrylic acid from propene. In this review, the recent developments and state of the art for the dehydration of lactic acid to acrylic acid are presented and critically commented. The most recent publications on the topic are discussed inetail with respect to the observed catalysts and process performance data. Among the different catalysts developed, three main groups can be distinguished: zeolites, sulphates, and phosphates. The latter, especially hydroxyapatites, have recently attracted the attention of academics in particular. The three families of catalysts are discussed and the recent developments and technical drawbacks in the gas phase dehydration are reported.

A Fine-Tuned MOF for Gas and Vapor Separation: A Multipurpose Adsorbent for Acid Gas Removal, Dehydration, and BTX Sieving

Summary The development of highly stable separation agents is recognized as a decisive step toward the successful deployment of energy-efficient and cost-effective separation processes. Here, we report the synthesis and construction of a metal-organic framework (MOF), kag -MOF-1, that has adequate structural and chemical features and affords a stable adsorbent with unique and appropriate adsorption properties for gas processing akin to acid gas removal, dehydration, and benzene-toluene-xylene (BTX) sieving. A combination of X-ray diffraction experiments, adsorption studies, mixed-gas breakthrough adsorption column testing, calorimetric measurements, and molecular simulations corroborated the exceptional separation performance of kag -MOF-1 and its prospective use as a multifunctional adsorbent. The unique adsorption properties of kag -MOF-1, resulting from the contracted pore system with aligned periodic array of exposed functionalities, attest to the prominence of this new generation of ultra-microporous material as a prospective practical adsorbent toward cost-effective and more simplified gas and vapor processing flowcharts for natural gas upgrading and flue gas scrubbing.

From HCOOH to CO on Pd catalyst: theoretical study

The present theoretical and experimental results in the literature for formic acid (HCOOH) oxidation into CO on Pd(111) cannot rationalize the well-known, easy CO poisoning. The present study reexamines HCOOH oxidation on Pd(111) by performing density functional theory calculations. Upon a thorough search, we present a new adsorption configuration of HCOOH on Pd(111). From the calculated energy pathway, we proposed that CO arises from the reduction of the hydrogenation product CO2 and direct dehydration of formic acid during HCOOH oxidation on Pd(111), with latter step being energetically easier. The present theoretical study rationalizes the early experimental findings and provides insights into the deactivation problem of Pd catalyst in the process of HCOOH oxidation.

Novel energy saving strategy for separating acetic acid – water in extractive distillation with N-methyl acetamide as entrainer

The design of homogeneous extractive distillation for acetic acid (AA) dehydration with N-methyl acetamide (NMA) as entrainer was investigated. It belongs to the classification of 0.0-1. The main challenge is that NMA and AA will lead to another pinch point, probably leading to energy cost and total annual cost (TAC) increase. Through analyzing thermodynamic insight, we have proposed a new strategy: low recycling entrainer purity for the extractive distillation of class 0.0-1 with no univolatility line existing. The strategy could save energy cost by avoiding the approach of the pinch point between AA and NMA. We have run sequence iterative optimization method for the process optimization. The total eleven variables are optimized. Results show that energy consumption and TAC are reduced by 50.6% and 52.1%, respectively. The results also reveal that a suitable shift of the feed tray locations improves the efficiency of the separation, even when less entrainer is used.

Synthesis of the Tripeptide Antibiotic Resormycin

A short and efficient synthesis of resormycin, a metabolite of Streptomyces platensis MJ953-SF5 with herbicidal and antifungal activity, is described. The key step in our synthetic approach is a late-stage stereospecific dehydration of a β-hydroxy amino acid to install the Z-olefin. Because of the modular nature of the synthesis, access to analogues for biological evaluation is readily available.

Combined Ab Initio, Kinetic Modeling, and Shock Tube Study of the Thermal Decomposition of Ethyl Formate.

The potential energy surfaces (PESs) and reaction rate constants of the unimolecular decomposition of ethyl formate (EF) were investigated using high-precision theoretical methods at the CCSD(T)/CBS(T-Q)//M06-2X/6-311++G(d,p) level of theory. The calculated PESs of EF dissociation and molecular decomposition reactions indicate that the intramolecular H-shift to produce formic acid and ethylene is the dominant decomposition pathway. A detailed chemical kinetic mechanism for EF pyrolysis was constructed by incorporating the important reactions of EF and its radicals into an existing mechanism previously developed for small methyl esters. The updated mechanism was first used to reproduce CO, CO2, and H2O concentration time histories during EF pyrolysis in the shock tube reported by Ren et al. [ Ren , W. , Mitchell Spearrin , R. , Davidson , D. F. , and Hanson , R. K. J. Phys. Chem. A 2014 , 118 , 1785 - 1798 ]. The rate of production and sensitivity analyses show that the competing dehydration and decarboxylation channels of the intermediate formic acid control the final product yields of EF pyrolysis. The EF mechanism was further validated against the shock tube data of OH, CO, CO2, and H2O time histories measured during EF oxidation (equivalence ratio Φ = 1.0) at 1331-1615 K and 1.52-1.74 atm. This revised EF mechanism captured all of the species' time histories over the entire temperature range. Such modeling capability was due to the more accurate rate constants of EF reactions determined by high-precision theoretical calculations and a high-fidelity C0-C2 basis mechanism.

Ileectomy-induced Bile Overaccumulation in Mouse Intestine.

Intestinal resection is a common therapeutic approach for human diseases such as obesity, inflammatory bowel disease, Crohn's disease, and colon cancer that often results in severe short bowel syndrome-like adverse effects including bile acid diarrhea, dehydration, electrolyte disturbances, and nutrient malabsorption. Here we introduce a murine ileal resection model, termed ileectomy, to evaluate tissue communication and the maintenance of systemic homeostasis. After ileal resection, circulating blood is permanently devoid of the ileum-specific endocrine hormone fibroblast growth factor 15 (FGF15), which releases its endocrinal inhibition of bile acid synthesis in the liver. In combination with the increased production and abolished reabsorption of bile acids after removing the ileum, mice that underwent surgery suffer from bile salt overaccumulation in the intestine and associated diarrhea, morbidity, and mortality. Novel usage of the surgery model introduced in this study may provide mechanistic and functional insights into ileal control of systemic metabolic regulation in physiology and disease.

Tunable interlayer spacing of composite graphene oxide-framework membrane for acetic acid dehydration

Minute amount of poly(vinyl alcohol) (PVA) was used to cross-link graphene oxide (GO) nanosheets to prepare composite graphene oxide-framework (GOF) membranes with a nacre-like structure. The PVA provided additional increase in viscosity of GO suspension which made the solution casting of a large-area composite GOF membrane possible. The membranes were applied to separate an acetic acid-water mixture through pervaporation. The ATR-FTIR and XPS analyses confirmed the covalent bonding between GO and PVA as ether bonds were formed. This influenced the changes in water contact angle where it increased from 40.8° (pristine GO) to 62.7° (GO-PVA8wt%). X-ray diffraction showed that d-spacing of GOF was higher than GO due to the intercalation of PVA. The d-spacing of GO layer from dry to wet state has a difference of 2.59 Å but addition of PVA lowered the difference to 0.38 Å. The newly formed covalent bonds between GO and PVA might suppressed the stretching of d-spacing. It shows that the swelling was prevented and the interlayer spacing can be tuned. The composite GO-PVA8wt% membrane has a short d-spacing and provided an outstanding pervaporation performance at 80 °C with a permeation flux of 463.9 g m−2 h−1 and water concentration in permeate of 97.7%.

Mixture of D-Vine copulas for chemical process monitoring

Complex dependence structures often exist in chemical process multivariate data. Although they are difficult to capture, vine copula shows good performance and stronger flexibility in depicting the highly nonlinear dependencies. To identify and fully understand the complex dependence patterns in multivariate data, a mixture of D-vine copulas (MDVC) is proposed. By using the expectation-maximization (EM) algorithm and stepwise semi-parametric (SSP) estimation for parameter estimation, the proposed model can depict the complex dependence structures in multivariate data. The highest density region (HDR) and the density quantile approach (DQA) are both used to construct the highest density region distance-based probability (HDRP) index to achieve a real-time process fault monitoring. The effectiveness and benefits of the proposed model are illustrated with a numerical example, the Tennessee Eastman (TE) benchmark process and a real acetic acid dehydration distillation system for fault detection. The results show that the proposed mixture of D-vine copulas can achieve good performance in chemical process fault monitoring.

Optimal design of extractive distillation for acetic acid dehydration with N-methyl acetamide

A distinctive strategy for entrainer recycling is proposed in this work for acetic acid (AA) dehydration by extractive distillation by using N methyl acetamide (NMA). The use of standard entrainers such as DMF or DMSO has the main drawback of forming an azeotrope with acetic acid. However, the vapour liquid equilibrium AA – NMA exhibits a tangential pinch point at NMA end composition. The new strategy rises from the thermodynamic analysis of the ternary diagram that which involves no azeotrope. As a result, acetic acid with high purity can be obtained by the recycling of the entrainer with a relaxed constraint in its purity. Optimization studies are discussed by using two approaches: two-step optimization method with Sequential Quadratic Programming (TSOM case) and the multi-objective genetic algorithm. The multi-objective genetic algorithm allowed the computation of the optimal acetic acid dehydration with an impurity of 3% in the recycled entrainer. Significant cost savings are achieved thanks to the optimization of both columns together. Energy consumption is reduced by 12.8% and 56.9% whereas TAC is saved by 28.4% and 56.3% compared with optimal case TSOM (impurity content 1%) and a published “Case Ref” (impurity content 0.01%), respectively.

Bacterial Cellulose Supported Alumina Catalyst for Ethanol Dehydration

An ultrafine three-dimensional nanofiber network structure of a very high porosity endows bacterial cellulose (BC) to function as support for heterogeneous catalysis. A novel catalyst of BC supported alumina (Al2O3) was developed by soaking purified BC hydrogel in aluminum nitrate (Al(NO3)3) aqueous solution, dehydration (hot air drying and freeze-drying) and calcination. The Al/BC catalysts reveal interior meso–macro porous structures with average pore diameters in the range of 17–34 nm. The catalytic activities were examined through an ethanol dehydration reaction in the gas phase at atmospheric pressure in the range of 200–400 °C. The effects of acidic metal loading and dehydration methods were investigated. Increasing Al loading from 12 to 50% resulted in a decreased surface area but an increase in pore size. At the same Al loading, the catalysts with a dehydration process by hot air drying presented higher Al concentrations on the outer surface compared with those by freeze-drying. At high temperature of 400 °C, Al/BC catalysts with 25 wt% Al loading and dehydrated by freeze drying (25Al/BC FD) and 50 wt% Al loading, dehydrated by hot air drying (50Al/BC TD) exhibited the highest ethanol conversions of 65.7–66.4% and ethylene yields of 43.26–44.24%, respectively, whereas at low temperature of 200 °C, Al/BC catalysts with 25 wt% Al loading with either dehydration method exhibited the highest diethyl ether yields of 40.02–41.60%.

Exfoliated HNb3O8 nanosheets of enhanced acidity prepared by efficient contact of K2CO3 with Nb2O5

Although exfoliated HNb3O8 nanosheet (e-HNb3O8) is known to be a powerful catalyst in acid-catalyzed reactions, the preparation technique has limitations in its high-yield production. We herein report the enhanced exfoliation efficiency and recovery of e-HNb3O8 by contacting Nb2O5 solid with a diluted K2CO3 solution before ball milling (mechanochemical activation). The so-obtained e-HNb3O8 showed a larger specific surface area, a higher density of total acid sites and an improved catalytic performance in the dehydration of 2-heptanol and formic acid, compared to the corresponding sample prepared by the conventional solid-state mixing. The ball-milled K2CO3–Nb2O5 mixtures, layered KNb3O8, ion-exchanged HNb3O8 and exfoliated HNb3O8 samples were characterized by PXRD, TEM-EDS, TGA-MS and SEM-EDS. The characterization results revealed more intercalated K+ ions in KNb3O8 particles as well as more homogeneous K2CO3–Nb2O5 mixture when the employed preparation technique was used. This is achieved by more infiltration of K2CO3 into Nb2O5 lattice before ball milling, thereby resulting in the above positive findings. Therefore, our approach has great potential to be extended to other niobate-containing nanosheet-type materials.

Biobased process intensification in selective synthesis of γ-butyrolactone from succinic acid via synergistic palladium–copper bimetallic catalyst supported on alumina xerogel

Biomass-based processes are gaining importance for sustainable chemical industry. The economic aspects of products from valorization of succinic acid are important. Selective synthesis of γ-butyrolactone is challenging, and catalyst development is a stumbling block. The synergistic effect of palladium–copper supported on alumina xerogel is demonstrated to obtain higher yield of γ-butyrolactone during successive dehydration and hydrogenation of succinic acid. The catalytic performance studies were carried out in slurry batch reactor, and 2.5% Pd–2.5% Cu on alumina xerogel was found to be active, selective and reusable catalyst. The catalyst was characterized by FTIR, XRD, TPD-NH3, BET nitrogen analysis, XPS and TEM at various stages of synthesis to understand the structure activity relationship. A kinetic model was developed for selective synthesis of γ-butyrolactone and validated. The activation energy for the reaction was found to be 11 kcal/mol.

Synthesis and characterization of polyamide membrane forthe separation of acetic acid from water using RO process

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute permeation was carried out under applied pressure of 5 bar at 25oC. Surface properties of TFC membrane were characterized by ATR-FTIR, SEM and AFM. The performance test indicated that 3.5 wt% of MPD, 0.35 wt% of TMC and curing temperature of 75oC are the optimum conditions. Moreover, the permeate flux was 4.3 L/(m^2 h) and acetic acid rejection was about 43% at these conditions.