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Glycyrrhetinic acid (GA) is the pentacyclic triterpenoid hydrophobic aglycone with many pharmacological effects and biological activities. Glycosylation is often used to improve the aglycone's properties such as solubility, stability, and pharmacological potency. UDP-glycosyltransferases (UGTs) are the main enzymes to catalyze this conversion via transferring glycosyl moiety to corresponding acceptor substrates in nature. However, a glycosyltransferase which can transfer glucose to GA has not been reported yet. The glycosyltransferase UGT73C11 from the plant Barbarea vulgaris was reported with the glycosylation function to compounds which are similar to GA in chemical structure. In this study, UGT73C11 was selected to express functionally in Escherichia coli and purified as the biocatalyst for the glycosylation of GA. As a result, the recombinant UGT73C11 catalyzed UDP-glucose and GA to produce a new compound GA-3-O-monoglucose. The product GA-3-O-monoglucose was characterized by HPLC and LC-ESI-MS spectrometry with an exact mass of 633, and the glucose was linked with an O atom at the GA C-3 position with a β-glycosidic bond by IR and NMR analyses. Under optimal reaction conditions, the recombinant UGT73C11 showed the highest activity at 40 °C with pH 7.0, and the highest conversion was found at the substrate molar ratio UDP-glucose/GA of 5:1. Last, 98% of GA was converted into the corresponding GA-3-O-monoglucose under optimized conditions at 6 h. GA-3-O-monoglucose improved significantly the solubility and bioactivity of the parent GA according to data from the water solubility and antibacterial activity testing. These results indicate that the recombinant UGT73C11 was potentially exploited as biocatalyst for the glycosylation of GA in industrial and pharmaceutical use. [ABSTRACT FROM AUTHOR]

To better understand the startup process, the evolution of voltage output, energy gain and output, active biomass, and electrochemical performance of microbial fuel cells (MFCs) started up under different external resistances (10, 50, 250, and 1000 Ω) was investigated. In addition, the influences of external resistance and mass transfer on the anodic biofilm distribution of MFCs were also investigated. The results showed that MFCs with a decreased external resistance during startup had an increased evolution rate of energy gain, energy output, active biomass, and maximum power density but a reduced voltage evolution rate. A low external resistance for startup resulted in a thick and compact biofilm. As the flow field induced mass transfer, the biofilm was mainly distributed on the carbon cloth against the flow channel, and the biomass decreased along the flow direction. The compact biofilm on the surface resulted in a poor mass transfer and limited biofilm development inside the electrode. [ABSTRACT FROM AUTHOR]

Amorphous triphenylmethoxysilane-derived silica membranes were prepared by chemical vapor deposition to demonstrate excellent hydrogen separation performance from gaseous mixtures containing methylcyclohexane (MCH) and toluene (TOL). Pure H2 permeances were on the order of 10-6 mol m-2 s-1 Pa-1, while the single gas permeances of SF6, TOL, and MCH were all on the order of 10-11 mol m-2 s-1 Pa-1, regardless of the ranges of pressure difference and temperature (0.1-0.5 MPa and 373-573 K). This agrees with the order of kinetic diameters for these gaseous molecules, showing high selectivity of hydrogen over the hydrocarbons. The influence of the coexisting MCH and TOL on H2 separation performance through the same membrane was investigated in the gaseous mixtures after eliminating the effect of water molecules. Similar negative effects were observed for MCH and TOL on the H2 separation properties, with the influence of TOL being slightly higher than that of MCH for H2-X (X = MCH, TOL) binary mixtures. Moreover, such the silica membrane exhibited high hydrogen separation performance and good stability in the H2-MCH-TOL ternary gaseous mixtures under operating conditions, which would have potential application to extract high purity hydrogen over 99.99% in membrane reactors. The membrane underwent eight mixtures exposure-regeneration cycles and exhibited stable medium-term running for over 25 days including gas-exchanging cycles and temperature cycles at 573-373 K. [ABSTRACT FROM AUTHOR]

Using ionic liquids for CO2capture is of great interest due to their unique characteristics. However, low gas–liquid mass transfer rates in conventional gas–liquid contactors due to the high viscosities of ionic liquids lead to the significant limitation for large-scale application of CO2capture using ionic liquids. Therefore, there is an urgent demand to develop a novel gas–liquid contactor for the intensification of the mass transfer efficiency in such a system. In this article, CO2absorption with an ionic liquid in a rotating packed bed (RPB) gas–liquid contactor is first reported. It was found that the RPB markedly enhanced the physical absorption of CO2in the ionic liquid in a very short contact time, within seconds. Only one cycle gas–liquid contact in the RPB could make the saturation ratio of CO2in the ionic liquid reach 60%. The effects of various operation conditions on the liquid side volumetric mass transfer coefficient (kLα) were elucidated. Increasing the rotating speed from 1100 to 3100 rpm doubled the kLα. The increase of the liquid flow rate also benefited the enhancement of the kLα. The experimentally measured kLα in the RPB is at least 1 order of magnitude higher than that in a conventional packed tower. A model based on penetration theory was proposed to describe the mechanism of gas–liquid mass transfer in the RPB. The predicted kLα was in good agreement with the experimental data with a deviation of less than 15%. The RPB shows great potential for the industrial application of CO2capture using ionic liquids. [ABSTRACT FROM AUTHOR]

As one of the important bone regeneration materials, α-calcium sulfate hemihydrate (α-CSH) has attracted widespread attention. In this study, a facile method was developed to prepare α-CSH with low aspect ratio via high-gravity continuously reactive precipitation of a calcium sulfate dihydrate (CSD) precursor, using ethanol as a morphology modifier in a rotating packed bed (RPB) reactor, combined with CaCl2 salt solution method under atmospheric pressure with the addition of citric acid with a low concentration (0.06 wt %). The precipitation time of CSD powders in the RPB was dramatically shortened from 30 min to 1 s, and the precursor exhibited more regular short rod shapes and much smaller size, compared to that obtained in a conventional stirring tank reactor (STR). Furthermore, calcium sulfate bone materials with high stability and good mechanical property were prepared by mixing α-CSH and normal saline with a liquid–solid ratio of 0.6. The RPB products had a higher compressive strength (2–3 times) than the STR counterpart. [ABSTRACT FROM AUTHOR]

The solubilities of sodium 1- and 2-naphthalenesulfonate (1- and 2-SNS) in aqueous sodium hydroxide solutions were measured over the temperature range from 276 to 337 K at atmospheric pressure by a dynamic method. The experimental results showed that the solubilities of 1- and 2-SNS both increased with temperature and decreased with concentrations of aqueous sodium hydroxide solutions. The experimental data were correlated with the new electrolyte nonrandom two-liquid (E-NRTL) model. The calculated results showed good agreement with the experimental data. A new strategy, based on the solubility difference between 1- and 2-SNS in aqueous sodium hydroxide solutions, was carried out in laboratory scale. This new strategy, in which the current process of blowing naphthalene was replaced by removing the byproduct according to the solubility difference, overcame the drawbacks of blowing naphthalene and made a good separation effect. The best separation effect was attained when the concentration of aqueous sodium hydroxide solution was 0.07 and the operating temperature was 298.15 K. The purities of obtained 1- and 2-SNS were 0.8369 and 0.9854 in this operating condition, respectively. The new strategy has potential in industrial application for optimizing the production of 2-naphthol. [ABSTRACT FROM AUTHOR]

In our recent work, the arrangement of multiple reactive sections is found to greatly enhance the steady-state performance of reactive distillation columns disproportionating trichlorosilane to silane. In the current research, process dynamics and controllability are studied through in-depth comparative analysis of open-loop and closed-loop behaviors between three reactive distillation columns with, respectively, a single reactive section (RDC-SRS), double reactive sections (RDC-DRS), and triple reactive sections (RDC-TRS). In the regulation path, although the arrangement of double and triple reactive sections reduces slightly the process gains between the bottom product composition and reboiler heat duty in the RDC-DRS and RDC-TRS, it helps to alleviate the coupling between the bottom product composition and reflux flow rate, thereby gaining increases in process controllability as compared with the RDC-SRS. In the disturbance path, the arrangement of double and triple reactive sections results in no intensified sensitivities to the disturbances from feed flow rate and composition. The closed-loop operation tests coincide with the open-loop analysis and demonstrate that the RDC-TRS and RDC-DRS exhibit substantially improved antidisturbance and set-point tracking capabilities as compared with the RDC-SRS. These outcomes highlight evidently the great importance of arranging multiple reactive sections to the dynamics and controllability of reactive distillation columns separating reacting mixtures with unfavorable and complicated reaction kinetics. [ABSTRACT FROM AUTHOR]

This work takes advantage of the unique thermally reversible dissociation/association feature of C-ON bonds in alkoxyamine (Diol) to facilitate the reprocessability of poly(butyl methanol methacrylate) (PBMM) rubber with excellent thermal and mechanical properties. Isocyanate groups were incorporated into the PBMM backbone and then reacted with hydroxyl groups in Diol to obtain cross-linked PBMM rubber. Although its cross-linking degree is slightly lower than the conventional cross-linked rubber by an irreversible cross-linker (Dieg), it shows a higher tensile strength and elongation at break. Its decomposition temperature is about 50 °C higher than PBMM cross-linked by Dieg. Furthermore, the dissociation of C-ON bond at high temperature can break the cross-linking network of PBMM rubber to form a flowable and reprocessable melt and show an excellent ability of reshaping and healing; the association of thermally reversible C-ON bond can completely recover the cross-linking network and mechanical properties at a low temperature. [ABSTRACT FROM AUTHOR]

The conventional method for configuring double temperature difference control (DTDC) schemes relies on sensitivity analysis (SA) and singular value decomposition (SVD) analysis, respectively, to determine sensitive and reference stages. Since no considerations are given at all to the interactions between the synthesized double temperature differences (DTDs) and to the coordination between the upper and lower temperature differences (TDs) subtracted in each synthesized DTD, the conventional method may lead to DTDC schemes that fail to secure tight product quality control of distillation columns. In this article, a novel method is proposed that employs a newly defined metric in our recent work, the averaged absolute variation magnitudes (ASVM), to determine the two reference stages in each DTDC loop. The ASVM measures the variations of TDs between the sensitive stage and the remaining ones with the assumption of complete rejection of all disturbances concerned and can thus reflect the inherent characteristics of coupling between the controlled product qualities. For each DTDC loop, while the first reference stage should be chosen to cope with its coupling with the other control loops, the second reference stage should be to coordinate the two TDs involved, thereby yielding a favorable effect to the inference of the controlled product qualities. Four example systems, including one conventional distillation column separating a binary mixture of ethanol and butanol, two conventional distillation columns separating a ternary mixture of ethanol, propanol, and butanol, and one dividing-wall distillation column separating a ternary mixture of ethanol, propanol, and butanol, are used to assess the proposed method by means of in-depth comparison with the conventional method. While they display comparable dynamic performances, the former leads to considerably smaller steady-state deviations in the controlled product qualities than the latter. These striking outcomes demonstrate evidently that the proposed method can be a promising alternative for the pursuit of tight temperature inferential control of various distillation columns. [ABSTRACT FROM AUTHOR]

Reactive distillation columns with double reactive sections (RDCs-DRS) at the top and bottom are especially favorable for the separations of reacting mixtures featuring the most unfavorable ranking of relative volatilities. In this article, their dynamics and control are studied in great detail, with special attention given to the influences of feed splitting on process dynamics and controllability. Because of the totally refluxed and totally reboiled operation mode plus an intermediate-product withdrawal, the RDC-DRS is generally characterized by severe under-dampness between the intermediate-product compositions and the reboiler heat duty (i.e., the regulation path) and by severe asymmetry between the intermediate-product compositions and the heaviest reactant feed flow rate (i.e., the disturbance path), consequently posing a great challenge to tight product quality control. With feed splitting of the lightest and heaviest reactants in the RDC-DRS (RDC-DRSFS), the simultaneous suppression of the under-dampness in the regulation path and the asymmetry in the disturbance path is attained, thereby presenting favorable influences to process dynamics and controllability. Two reactive distillation systems, executing a hypothetical reversible reaction, A + B ↔ C + D (αA > αC > αD > αB), and the lactic acid esterification with methanol, are employed to inspect the dynamics and controllability of the RDC-DRS and RDC-DRSFS. Although the RDC-DRS can be maintained as stable, rather sluggish tracking responses are noticed because the under-damped and asymmetrical behaviors restrict tight controller tuning. The RDC-DRSFS, on the other hand, shows greatly improved tracking performance with even enhanced disturbance rejection capabilities. The comparison endorses the great significance of feed splitting for the RDC-DRS, namely, not only an effective strategy for process retrofitting but also a potential booster for process dynamics and controllability. [ABSTRACT FROM AUTHOR]

With reference to the disproportionation of trichlorosilane to silane, a three-stage consecutive reversible reaction with rather unfavorable reaction kinetics of a near zero thermodynamic conversion, an in-depth comparison in steady-state performance is performed between the reactive distillation column with a single reactive section (RDC-SRS) and those with multiple reactive sections (RDC-MRS), under the assumptions of the same total number of stages and the same total amount of catalyst employed. With the incremental arrangement of reactive sections, the RDC-MRS shows a steady improvement in steady-state performance with considerably reduced operating cost and capital investment as compared with the RDC-SRS. The great advantages originate essentially from the additional degrees of freedom resulting from the arrangement of multiple reactive sections in process synthesis and design. Apart from the coordination effect to the three-stage consecutive reversible reactions processed, the additional degrees of freedom serve also to reinforce internal mass integration and internal energy interaction between the reaction operations and the separation operations involved. Arrangement of side-condensers is also examined toward the RDC-MRS, and the outcomes reveal the thermodynamic rationale to adopt multiple reactive sections in process development. Although these findings are derived from the specific case study chosen, it should be considered to be of general significance for the synthesis and design of reactive distillation columns separating complicated reacting mixtures involving multiple reversible reactions. [ABSTRACT FROM AUTHOR]

The nitration process as one step in 2-amino-5-chloro-4-methylbenzenesulfonic acid synthesis was improved by optimizing nitration reaction conditions, improving product separation method to eliminate salty scrap acid and cycle use of the concentrated sulfuric acid. The effect of various parameters such as temperature, quality of fuming sulfuric acid, quality of fuming nitric acid, and reaction time was studied for optimization of the nitration reaction condition. In the optimum conditions, the mass ratio of fuming sulfuric acid to sodium 2-chlorotoluene-4-sulfonate and molar ratio of fuming nitric acid to sodium 2-chlorotoluene-4-sulfonate were 4 and 1.05, respectively. The reaction temperature was -5 °C, and the time of reaction was 3 h. By applying the optimum reaction conditions, the yield of nitration reaction was increased to 91%, larger than that of the current industrial process whose yield is only 65.7%. The solubilities of sodium 2-chloro-5-nitrotoluene-4-sulfonate in aqueous sulfuric acid solutions were determined by a dynamic method, and the results showed that the lowest sodium 2-chloro-5-nitrotoluene-4-sulfonate solubility was exhibited in 0.7 mass fraction aqueous sulfuric acid solutions. So the product sodium 2-chloro-5-nitrotoluene-4-sulfonate of nitration reaction was separated by filtration from 0.7 mass fraction aqueous sulfuric acid solutions, and the obtained concentrated aqueous sulfuric acid solution was reused. [ABSTRACT FROM AUTHOR]

Thedeformation of the dispersed phase in polymer blends by tapeextrusion was studied systematically under different processing conditionsand viscosity ratios of the dispersed phase to the matrix. Duringtape extrusion, the spherical dispersed phases were first elongatedinto rotational ellipsoidal or rodlike shapes and then merged to formlonger and even endless microfibrils by coalescence, which were eventuallysqueezed into highly oriented ribbons. The speed of two running rollershas a large effect on the morphology development of the dispersedphase. With an increase of the roller surface speed, the stretchingand squeezing forces increased dramatically. As a result, the dispersedphase gradually deformed from spherical to ellipsoidal, fibrous, andribbonlike shapes. More interestingly, the tensile strength of theobtained blend film with highly oriented ribbons increased significantlyas well. The viscosity ratio of the dispersed phase to the matrixis another important factor influencing the formation of a highlyoriented polymer blend. It is found that a low viscosity ratio facilitatesthe deformation and coalescence of the dispersed phase to form highlyoriented ribbons. Therefore, in order to prepare a well-controlledpolymer blend with highly oriented ribbons, the combination of a high-viscositymatrix and a low-viscosity dispersed phase is preferred. [ABSTRACT FROM AUTHOR]

Toseparate a salt mixture (mainly consisting of Na2CO3and Na2SO4) which is formedfrom the 4,4′-diaminostilbene-2,2′-disulfonic acid wastewatertreatment, the solubility data of Na2CO3andNaHCO3in Na2SO4–water solventmixtures were measured using a dynamic method over the 275–335K temperature range. The solute-free mass fraction of Na2SO4in the solvent mixtures extended from 0 to 0.25. Thesolubility of Na2CO3and NaHCO3inNa2SO4–water solvent mixtures decreasedwith addition of Na2SO4. With rising temperature,the solubility of NaHCO3increased while the solubilityof Na2CO3increased at first and then decreasedafter transition points. The experimental data were correlated withthe electrolyte nonrandom two-liquid model. The root-mean-square deviationsof solubility temperature varied from 0.35 to 1.50 K. Based on thesolubility data of this work, a new strategy for separating the Na2CO3and Na2SO4mixture wasproposed theoretically. [ABSTRACT FROM AUTHOR]