Aqueous Solutions Of Succinic Acid Research Articles

Characterization by X-ray absorption spectroscopy of bimetallic Re–Pd/TiO2 catalysts efficient for selective aqueous-phase hydrogenation of succinic acid to 1,4-butanediol

Re–Pd catalysts supported on TiO2 (P25 or DT51) prepared by successive impregnation (SI) or by Re deposition on Pd/TiO2 by catalytic reduction (CR) were characterized by XANES and EXAFS at the Pd and Re edges. These samples were shown to be efficient for the selective hydrogenation in aqueous solution of succinic acid (SUC) to 1,4-butanediol (BDO) (T = 160 °C, P(H2) = 150 bar). This study clearly highlights the need for in situ re-activation of Re-based systems before their characterization or use, since Re species are fully re-oxidized (Re7+) by contact with air. The XANES quantitative analysis at the Re LIII-edge reveals that after in situ reduction, the Re average reduction state is in most cases inferior or equal to +3, indicating the presence of a mixture of Re3+ and Re0 species in all reduced catalysts. EXAFS study indicates that the Re species are mainly located at the Pd-support interface for the CR sample, whereas a part of Re entities is also deposited as isolated forms on the support in the case of the SI catalyst. The Re–Pd/DT51-SI system leading to the best BDO yield displays a specific arrangement of the Pd and Re species (Re deposit on Pd sites of high coordination). In this sample, the Re0 species, present in none negligible proportion, would contribute similarly as Pd metal to the efficient transformation of SUC towards GBL, which is further converted to BDO on sites involving Pd0 and oxidized Re3+ species nearby.

Mass transfer and droplet formation regime in a countercurrent mini-channel extractor

Countercurrent extraction is an efficient separation operation to be widely used in chemical industry. However, it is a challenge to realized countercurrent extraction in microchannel. Liquid-liquid countercurrent extraction was successfully realized in mini-channels with internal diameters of 3 mm–7 mm. Aqueous solution of succinic acid was used as continuous phase and flowed downward along the channel by gravity, n-butanol was used as dispersed phase and flowed upward by buoyancy. The droplet flow behaviors and the mass transfer characteristics were investigated systematically. The superficial velocitiesof aqueous solution ranged from 2.64 × 10−4 m/s–1.32 × 10−3 m/s, the orifice velocities of organic liquid ranged from 0.175 m/s to 1.40 m/s. The internal diameters of mini-channels varied from 3 mm to 7 mm, the lengths of mini-channels varied from 200 mm to 400 mm, and the nozzle diameters were between 0.11 mm and 0.29 mm. Three droplet formation regimes were observed, including down-dripping, dripping and jetting. Two flow patterns including monodispersed droplets pattern and chaotic droplets pattern were also observed. The volumetric mass transfer coefficients KLa were between 1.56 × 10−4 and 1.28 × 10−2s−1, which are 2–10 times of that in traditional extractors. An empirical correlation was developed based on the dimensionless analysis. It predicted the volumetric mass transfer coefficients within the deviation of ±20%.

Assessment of the Total Volume Membrane Charge Density through Mathematical Modeling for Separation of Succinic Acid Aqueous Solutions on Ceramic Nanofiltration Membrane

Nanofiltration of aqueous solutions of succinic acid with the addition of sodium hydroxide or magnesium hydroxycarbonate has been investigated experimentally and modeled with the comprehensively described Donnan–Steric partitioning model. The experimental retentions of acid at the same pH varied between 16% and 78%, while the estimated total volume membrane charge densities were in the range of −35.73 and +875.69 mol/m3. This work presents a novel insight into the modeling of nanofiltration and investigates the relations between the estimated total volume membrane charge densities, ionic strength, and component concentration on the performance of ceramic membrane. In addition, this study takes into consideration other parameters such as pH regulation and viscosities of solutions.

Технология получения белкового концентрата овса посевного с высокими физико-химическими и функционально-технологическими характеристиками

The current intensive industrialization has changed the food preferences of consumers. As a result, there is a growing demand for high-grade high-nutritional meat and dairy products, which, in its turn, triggered an increase in the demand for grain crops and led to higher animal feed prices. All these affected the price and quality of the finished product, since farms are trying to stay profitable. As a consequence, the high cost of animal proteins make producers look for other sources of protein with similar qualities. Common oat (Avena sativa L.) remains the most cultivated species. Oats are a source of high-quality protein with an optimal amino acid balance. The paper features a oat protein technology (Avena sativa). The research defined the parameters of the protein extraction process. For acid and alkaline methods, the following optimum parameters were revealed: temperature – 40 ± 2°C, hydraulic module – 1:10, time – 90 minutes, active acidity of the acid extraction – 2.0 units, active acidity of alkaline extraction
 – 9.0 units. The authors managed to obtain protein substances with the molecular weight > 50 kDa. The optimal parameters of ultrafiltration of the protein extract were as follows: pore diameter = 100 kDa at pH 8.0 and 0.5 MPa. The ultrafiltration conducted under these conditions showed that the content of high molecular fractions (globulins and albumins) increased from 39.12% to 55.15% for the extract obtained by alkaline method, whereas the content of low molecular weight fractions (prolamins and glutelins) decreased from 60.88% to 44.85%. Ultrafiltration of protein extracts obtained by alkaline and acidic methods made it possible to concentrate protein fractions with a molecular weight ≥ 50 kDa. When a 10% aqueous solution of succinic acid was used as a precipitator, the protein precipitation degree equaled 89.3%. The paper introduces a new oat protein purification method. The optimal multiplicity of purification by RP-HPLC was 4 purification cycles. For the alkaline extract, the total content of high molecular weight fractions (50.0–120.0 kDa) was 72.7% and the total content of low molecular weight fractions (15.0–49.0 kDa) was 27.3%. For the acid extract, the total content of high molecular weight fractions was 72.9%, while the content of low molecular weight fractions was 27.1%. Oat proteins obtained by alkaline and acid extraction demonstrated a high foaming ability (148–177%) at pH = 6.0–9.0, as well as a good fat and water retention capacity. The oat proteins were found to have a high content of protein and essential amino acids similar to animal proteins. A comparative analysis showed that oat protein can act as an alternative substitute for animal proteins.

Succinic acid in aqueous solution: connecting microscopic surface composition and macroscopic surface tension.

The water-vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. It was found that succinic acid has a considerably higher propensity to reside in the aqueous surface region than its deprotonated form, which is effectively depleted from the surface due to the two strongly hydrated carboxylate groups. From both XPS experiments and MD simulations a strongly increased concentration of the acid form in the surface region compared to the bulk concentration was found and quantified. Detailed analysis of the surface of succinic acid solutions at different bulk concentrations led to the conclusion that succinic acid saturates the aqueous surface at high bulk concentrations. With the aid of MD simulations the thickness of the surface layer could be estimated, which enabled the quantification of surface concentration of succinic acid as a multiple of the known bulk concentration. The obtained enrichment factors were successfully used to model the surface tension of these binary aqueous solutions using two different models that account for the surface enrichment. This underlines the close correlation of increased concentration at the surface relative to the bulk and reduced surface tension of aqueous solutions of succinic acid. The results of this study shed light on the microscopic origin of surface tension, a macroscopic property. Furthermore, the impact of the results from this study on atmospheric modeling is discussed.

Study of Monometallic Pd/TiO2 Catalysts for the Hydrogenation of Succinic Acid in Aqueous Phase

A series of 2 wt % Pd/TiO2 monometallic catalysts were prepared by varying some parameters, such as the nature of the precursor salt, the titania support, and the preparation method. The structural and textural properties of the catalytic systems were fully characterized by several physical and chemical techniques (inductively coupled plasma optical emission spectrometry, N2 physisorption, H2 chemisorption, transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, powder X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, and gas phase reaction of cyclohexane dehydrogenation). The catalytic performances were further estimated for the hydrogenation of an aqueous solution of succinic acid (SUC) performed in a batch reactor at 160 °C and under 150 bar total pressure. The results showed that all the Pd catalysts are very selective to produce γ-butyrolactone, the first hydrogenated product. However, the rate of succinic acid conversion is a function ...

Esterification of bio-based succinic acid in biphasic systems: Comparison of chemical and biological catalysts

Different chemical and biological catalysts were screened for the biphasic esterification of aqueous solutions of succinic acid with 1-octanol. Among them, DBSA, Nafion NR-50 and Novozym 435 were found to be the most attractive catalysts. The pH, the temperature and the catalyst concentration had high impacts on the reaction rates. The optimization of the reaction conditions with a single-variable approach for the chemical catalysts and a Response Surface Methodology for the enzyme allowed an increase of the rates by a factor 1.5 for DBSA, 2.3 for Nafion NR-50 and 1.3 for Novozym 435. Real fermentation broths produced from recombinant Escherichia coli could be successfully esterified with conversions up to 93% for DBSA and 70% for Nafion NR-50 and Novozym 435 as catalysts. Finally, DBSA was selected as the cheapest and most active option. Besides, the esters were isolated with a purity of 83% from fermentation broth solutions. DBSA also catalyzed the esterification of succinic acid from fermentation broth with many alcohols creating a broad spectrum of interesting esters. The esters might then be used as end-product, hydrolyzed back to pure succinic acid or hydrogenated.

Electrochemical characterization of surface complexes formed on Cu and Ta in succinic acid based solutions used for chemical mechanical planarization

Open-circuit potential measurements, cyclic voltammetry and Fourier transform impedance spectroscopy have been used to study pH dependent surface reactions of Cu and Ta rotating disc electrodes (RDEs) in aqueous solutions of succinic acid (SA, a complexing agent), hydrogen peroxide (an oxidizer), and ammonium dodecyl sulfate (ADS, a corrosion inhibitor for Cu). The surface chemistries of these systems are relevant for the development of a single-slurry approach to chemical mechanical planarization (CMP) of Cu lines and Ta barriers in the fabrication of semiconductor devices. It is shown that in non-alkaline solutions of H 2O 2, the SA-promoted surface complexes of Cu and Ta can potentially support chemically enhanced material removal in low-pressure CMP of surface topographies overlying fragile low-k dielectrics. ADS can suppress Cu dissolution without significantly affecting the surface chemistry of Ta. The data analysis steps are discussed in detail to demonstrate how the D.C. and A.C. electrochemical probes can be combined in the framework of the RDE technique to design and test CMP slurry solutions.

Relationship between the structure of Ru/CeO2 catalysts and their activity in the catalytic ozonation of succinic acid aqueous solutions

Two Ru/CeO2 catalysts were used for the study of the catalytic ozonation of aqueous solutions of succinic acid (SA). These catalysts were prepared either by impregnation (I) or by acid exchange (AE). The objectives were (1) to determine the efficiency towards the oxidation of the organic molecule in relation to the catalysts characterization, and (2) to examine the modifications of the structure induced by ozonation. For each catalyst, two experimental conditions of catalyst and succinic acid concentrations were studied. The diluted conditions ([SA]0=1mM, weightcata=0.8g/l) were applied for the study of the behavior of the catalysts during successive uses. The efficiency was also studied for higher initial concentrations ([SA]0=5mM, weightcata=3.2g/l). Under both conditions the best efficiency was obtained with the impregnated catalyst.Transmission electronic microscopy analyses indicated that before ozonation of SA, ruthenium was distributed within the whole volume of the grain of CeO2 for the AE catalyst, and included only in an external layer for the I catalyst. The size of the particles determined by X-ray diffraction (XRD) was around 3.5nm for Ru and in the range 10–75nm for CeO2. In most cases, the catalytic ozonation induced Ru sintering with the formation of clusters. After four successive ozonation experiments the AE catalyst efficiency was significantly decreased and the structure totally disorganized.

Synthesis of 1, 2, 3, 4-butanetetracarboxylic acid from the irradiation of aqueous succinic acid

This paper deals with the action of ionizing radiation on diluted aqueous solutions of succinic acid in order to synthesize 1, 2, 3, 4- butanetetracarboxylic acid. This compound has a variety of industrial and agricultural applications. The chemical synthesis of this compound involves several steps. In contrast the radiation-induced synthesis can be achieved in one step and with a good yield. The results obtained show that one of the most important reactions was the demerization of the target compound yielding the tetracarboxylic acid.

Conductance Studies of Aqueous Succinic Acid

Abstract Conductance measurements of aqueous solutions of succinic acid and of di-sodium succinate were performed from 278.15 to 308.15 K and the limiting conductances λ0 (1/2 Succ2- ) are reported. The Waiden product is independent of temperature: λ0(1/2 Succ2-)*η(T) = 0.503 ± 0.001. The salt conductances closely obey the Onsager limiting law. The evaluation of the equilibrium constants for the primary and secondary steps of dissociation, K1 and K2, and the limiting conductances of the hydrosuccinate ion, λ0(HSucc-), are discussed using the Quint and Viallard conductance equation

Heterogeneous nucleation of bubbles at solid surfaces in gas-supersaturated aqueous solutions

CH 4, Ar, and N 2 supersaturation thresholds for cavitation in saturated aqueous solutions of succinic acid, potassium nitrate, and potassium chloride were determined at room temperature in the presence and absence of crystalline precipitates. To avoid the introduction and interference of preformed gaseous nuclei, crystals were formed in situ by cooling prior to decompression, after the solutions had been equilibrated with gas at elevated pressure and temperature. In the succinic acid and potassium nitrate systems, bubbles first occurred during decompressions in exclusive association with crystals. At ambient pressure, such cavitation occurred with supersaturations below 10 atm, while cavitation without crystals required supersaturations over 100 atm. In contrast, cavitation with potassium chloride crystals required supersaturations exceeding 100 atm. It is concluded that thresholds with succinic acid and potassium chloride crystals accurately reflected particular properties of the crystal-liquid interfaces, while the low thresholds observed with potassium nitrate crystals may also have reflected certain effects of the preceding crystallization processes per se. Results may be of particular biological significance because thresholds with succinic acid crystals at atmospheric pressure were within 5 atm of the supersaturations which elicit bubble-induced trauma in animals and man.