Comparative Study Between Ethylbenzene Disproportionation Reaction and its Ethylation Reaction with Ethanol over ZSM-5

Ethylation of ethylbenzene with ethanol has been studied over ZSM-5 catalyst in a riser simulator that mimics the operation of a fluidized-bed reactor. The feed molar ratio of ethylbenzene:ethanol is 1:1. The study was carried out at 350, 400, 450, and 500 °C for reaction times of 3, 5, 7, 10, 13, and 15 s. Comparisons are made between the results of the ethylbenzene ethylation reaction with that of ethylbenzene disproportionation reaction earlier reported. The effect of reaction conditions on ethylbenzene reactivity, p-diethylbenzene selectivity, total diethylbenzene (DEB) isomers selectivity, p-DEB-to-m-DEB ratio, benzene-to-DEB molar ratio, and benzene selectivity, are reported. Benzene selectivity is about 10 times more in the EB disproportion reaction as compared to its ethylation reaction with ethanol at 350 °C. In addition, the results showed a p-DEB/m-DEB ratio for the EB ethylation reaction varying between 1.2–1.7, which is greater than the equilibrium values. Increase in temperature shifts the alkylation/dealkylation equilibrium towards dealkylation, thereby decreasing conversion and selectivity to DEB.     

Interactions of binary liquid mixtures with polysaccharides studied using multi-dimensional NMR relaxation time measurements

Nuclear magnetic resonance transverse T₂ relaxation time has proven to be a valuable parameter for characterizing liquid/polymer interactions. This measurement is applicable to many food, personal care, and cosmetic products that contain multi-component liquid mixtures. Here, we investigate the interactions of corn starch with water/glycerol mixtures of different weight compositions and explore liquid exchange dynamics; such a system is relevant to the personal care industry. We use a combination of chemical shift resolved ¹H T₂ relaxation measurements and corresponding two-dimensional T₂ relaxation exchange experiments using both a conventional experimental protocol and a modified method with the addition of NMR chemical shift selectivity. Two relaxation regimes were evident for the hydroxyl ¹H (found in both water and glycerol) whilst three relaxation regimes are evident for the aliphatic glycerol ¹H associated here with strongly bound, weakly bound, and free (bulk) liquid, respectively. At higher water contents preferential absorption of glycerol was evident. T₂-T₂ exchange maps with a range of storage times reveal molecular exchange rates between all three regimes due to self-diffusion. Rapid exchange of water between the bulk and bound locations was evident in the case of pure water. Exchange rates for hydroxyl ¹H was considerably reduced by the inclusion of glycerol.     

High-pressure phase equilibria of systems carbon dioxide + n-eicosane and propane + n-eicosane

In this work we investigated the phase equilibrium behavior of the binary asymmetric systems propane (C3) + n-eicosane (C20) and carbon dioxide (CO₂) + n-eicosane (C20). We used a variable-volume view cell for obtaining fluid–fluid equilibrium (FFE), solid–fluid equilibrium (SFE) and solid–fluid–fluid equilibrium (SFFE) experimental data. We modeled the phase equilibria of both systems using the Peng–Robinson Equation of State for describing the fluid phases and an expression for the fugacity of pure solid n-eicosane with parameters fit to reproduce the pure n-eicosane melting line. We performed the phase equilibrium calculations by implementing path-following methods for tracking entire solid–fluid (SF) and solid–fluid–fluid (SFF) equilibrium curves for binary asymmetric mixtures. This made it possible to obtain complete isoplethic lines or complete three-phase equilibrium lines in single runs. Although the model is relatively simple, it is able to grasp the complex observed behavior for the systems studied here.     

High-pressure phase equilibria of systems carbon dioxide + n-eicosane and propane + n-eicosane

In this work we investigated the phase equilibrium behavior of the binary asymmetric systems propane (C3) + n-eicosane (C20) and carbon dioxide (CO₂) + n-eicosane (C20). We used a variable-volume view cell for obtaining fluid–fluid equilibrium (FFE), solid–fluid equilibrium (SFE) and solid–fluid–fluid equilibrium (SFFE) experimental data. We modeled the phase equilibria of both systems using the Peng–Robinson Equation of State for describing the fluid phases and an expression for the fugacity of pure solid n-eicosane with parameters fit to reproduce the pure n-eicosane melting line. We performed the phase equilibrium calculations by implementing path-following methods for tracking entire solid–fluid (SF) and solid–fluid–fluid (SFF) equilibrium curves for binary asymmetric mixtures. This made it possible to obtain complete isoplethic lines or complete three-phase equilibrium lines in single runs. Although the model is relatively simple, it is able to grasp the complex observed behavior for the systems studied here.     

Acylation of p-xylene over zeolites

Zeolites differing in structure and acidity were tested in liquid phase acylation of p-xylene. Hexanoyl chloride, propionic anhydride and isobutyric anhydride were used as acylating agents. The highest conversions of acylating agent were achieved over large pore zeolites USY (66.3%) and Beta (58.2%). It was found that acylation of p-xylene proceeds only over large pore zeolites Beta and USY. Selectivities to monoacylated p-xylene obtained over USY zeolite decreased in the order: propionic anhydride 78.0% > hexanoyl chloride 67.2% > isobutyric anhydride 33.1%. Diacylated product was formed over zeolite USY with all acylating agents tested but only with hexanoyl chloride over zeolite Beta. It was found that the optimum Si/Al ratio of zeolite Beta for p-xylene acylation with propionic anhydride is 25, while for isobutyric anhydride is 19. Conversion of isobutyric anhydride decreased with increasing isobutyric anhydride concentration and increased with increasing amount of catalyst.     

Molecular thermodynamic analysis for phase transitions of linear and cross-linked poly(N-isopropylacrylamide) in water/2-propanol mixtures

Ternary liquid–liquid phase transitions of linear poly(N-isopropylacrylamide) (PNIPA) and the swelling behavior of cross-linked PNIPA gels in water/2-propanol mixtures were investigated using thermo-optical analysis (TOA) and a photon correlation spectroscopy (PCS) technique, respectively. Closed immiscibility gaps in ternary phase diagrams were obtained below 35 °C although all binary mixtures involved in this system were completely miscible. At a fixed concentration of PNIPA (1.0 wt%), a decrease in the lower critical solution temperature (LCST) occurred first, and with an increasing 2-propanol fraction of the solvent mixture, the upper critical solution temperature (UCST) subsequently developed. Corresponding to the linear PNIPA solution behavior, swollen PNIPA gels in pure water first shrank and then reswelled with increasing 2-propanol content in a typical reentrant transition. For theoretical treatment of the mixtures, a multi-component lattice theory of mixing and Flory–Rehner chain model for elasticity were employed for molecular thermodynamic analysis. A secondary lattice concept of specific interactions was used to model binary water/PNIPA solutions, and a temperature dependence of the intermolecular interactions for 2-propanol/PNIPA was used to describe island type ternary phase diagrams. The swelling transitions of cross-linked PNIPA gels were calculated using model parameters obtained from the ternary phase diagrams of linear PNIPA or from experimental conditions. The predicted results were in good agreement with experimental data without the need for further adjustable parameters.     

Upper critical solution temperature—type cononsolvency of poly(N,N-dimethylacrylamide) in water—organic solvent mixtures

The behaviour of linear poly(N,N-dimethylacrylamide) (PDMAM) chains was studied by turbidimetry and viscometry in mixtures of water with the polar organic solvents methanol, dioxane and acetone. The swelling-deswelling behaviour of PDMAM gels in the same solvent mixtures was also investigated. Contrary to the behaviour in water-methanol mixtures, in water-dioxane and water-acetone mixtures a significant shrinkage of polymer chains and deswelling of polymer gels, followed by phase separation, was observed for high organic solvent fractions. Cononsolvency phenomena were found to be temperature-dependent, as demixing occurred upon decreasing temperature. This upper critical solution temperature (UCST) phase separation behaviour in mixed solvents was studied by turbidimetry and compared to the well-known lower critical solution temperature (LCST) behaviour of poly(N-isopropylacrylamide) (PNIPAM) in similar solvents mixtures.     

Control of the lower critical solution temperature—type cononsolvency properties of poly(N-isopropylacrylamide) in water—dioxane mixtures through copolymerisation with acrylamide

The behaviour of the homopolymers poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide (PAM) and random copolymers of N-isopropylacrylamide (NIPAM) with acrylamide (AM) was studied by turbidimetry and viscometry in mixtures of water with dioxane. It was found that the well-known lower critical solution temperature-type cononsolvency properties of PNIPAM in water-dioxane mixtures, observed in the water-rich region, can be effectively controlled by copolymerisation of NIPAM with AM. Thus, the cononsolvency properties of the copolymers in water-dioxane mixtures are shifted to higher temperatures and restricted within a narrower solvent composition region as the acrylamide content of the copolymers increases. A significant decrease of the reduced viscosity of the systems exhibiting phase separation properties was observed upon heating, indicative of the collapse of the (co)polymer chains as temperature approaches the corresponding cloud point temperature. Furthermore, when temperature is fixed close to the cloud point temperature, the reduced viscosity decreases with increasing the volume fraction of dioxane, φ, as far as the solvent mixtures are rich in water. On the contrary, the reduced viscosity of PNIPAM in dioxane-rich mixtures is found significantly higher, indicative of an expansion of the polymer chain, as compared to the reduced viscosity of this polymer in the two pure solvents.     

Vapour liquid equilibrium with association in both phases: A model with the concentration-dependent liquid phase association constant applied to acetic acid—benzene, -toluene, -p- and -o-xylene

A model employing the correction factors of Marek and Standart, but using a concentration-dependent liquid phase association factor of Jenkins—Robinson, has been used to model vapour—liquid equilibrium data for mixtures of acetic acid with benzene, toluene, o-xylene and p-xylene. With the aim to use systems of acetic acid—benzene and acetic acid—toluene as the test mixtures for distillation columns, the examination of the systems of acetic acid—aromatic hydrocarbons was undertaken. The model promises to be useful in modelling isobaric and isothermal data of acetic acid—benzine, acetic acid—toluene, acetic acid-p-xylene and acetic acid-o-xylene systems. Deviation plots show that the isothermal and isobaric data are represented well.     

Fluorescence studies on local density change in supercritical CO2 mixtures using the order parameter model

Supercritical CO₂ has many unusual physicochemical properties in or near the critical region, which is mostly due to the local density enhancements and specific molecular interactions. Compared to pure CO₂, the study on CO₂ mixed with co-solvent is attractive in wide applications but it is hard to quantitatively describe the local density change and intermolecular clusters in CO₂ mixtures. The fluorescence response of a sensitive pyrene probe, empirical Py scale, was determined in CO₂ mixed with pentane at 323.15 K in different phase regions. A variable called the order parameter was introduced to account for possible correlations in the first derivative of Py scale and fluid pressure (dPy/(d(P/P₀ − 1))). This model, avoiding the hard choice of the reference line in CO₂ mixtures, was effective in calculating the local density change and it showed the specific molecular interaction in the critical region. The behaviors of the local density change and the isothermal compressibility of supercritical CO₂ mixtures correlated well with microscopic and macroscopic observations.     

In situ FTIR study of the decomposition of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ionic liquid during cathodic polarization of lithium and graphite electrodes

In this work we analyzed the cathodic reactions of an important ionic liquid (IL) based electrolyte solution, namely lithium bis(trifluoromethylsulfonyl)imide (LiTFSI)/N-methyl-N-methylpyrrolidinium (BMP) TFSI. In situ FTIR spectroscopy was used for the analysis of gaseous products of the electrochemical decomposition of this IL solution during cathodic polarization of lithium metal and graphite electrodes. The main volatile product of the reductive decomposition of the anion in these BMPTFSI solutions is trifluoromethane. BMP cations decompose to mixtures of tertiary amines and hydrocarbons. The composition of the products is influenced by the nature of the anode material. Graphite possesses a catalytic activity in the electroreduction process of BMP cations which occurs along with their intercalation into the graphite structure. The liquid phase after cathodic polarization of graphite electrodes was analyzed by multinuclear NMR spectroscopy coupled with FTIR spectroscopy. ¹⁵N NMR and FTIR spectra revealed an increase in the Li cations content in the electrolyte solution, as a result of BMP cations decomposition during repeated cycling of graphite electrodes.     

H NMR study of temperature-induced phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(N-isopropylacrylamide) mixtures and random copolymers

¹H NMR spectroscopy was used to investigate temperature-induced phase transitions in D₂O solutions of poly(N-isopropylmethacrylamide) (PIPMAm)/poly(N-isopropylacrylamide) (PIPAAm) mixtures and P(IPMAm/IPAAm) random copolymers of various composition on molecular level. While two phase transitions were detected for PIPMAm/PIPAAm mixtures, only single phase transition was found for P(IPMAm/IPAAm) copolymers. The phase transition temperatures of PIPAAm component (appears at lower temperatures) are not affected by the presence of PIPMAm in the mixtures; on the other hand, the temperatures of the phase transition of PIPMAm component (appears at higher temperatures) are affected by the phase separation of the PIPAAm component and depend on concentration of the solution. For P(IPMAm/IPAAm) random copolymers, a departure from the linear dependence of the transition temperatures on the copolymer composition was found for a sample with 75 mol% of IPMAm monomeric units.     

Structural behaviour of molecular alloys: n-pentacontane (n-C50H102)-n-pentacosane (n-C25H52); n-pentacontane (n-C50H102)-n-tricosane (n-C23H48) at room temperature

This paper displays a study of binary mixtures of n-alkanes whose ratio of chain length is around two. The systems composed of n-tricosane (n-C₂₃H₄₈)-n-pentacontane (n-C₅₀H₁₀₂) and n-pentacosane (n-C₂₅H₅₂)-n-pentacontane (n-C₅₀H₁₀₂) have been studied by means of X-ray analyses. These latter, performed at room temperature, showed in both cases, the existence of a large domain where the phases characteristic of each pure component coexist. These mixtures obey Kravchenko's rule relative to the solubility of the n-alkanes according to the chain length of each component. The mixtures studied do not form an intermediate solid solution. In other words, there is no particular arrangement of the shorter molecules inside the crystallographic unit of the longer.     

Concentration-Thermal Swing Adsorption Process for Separation of Bulk Liquid Mixtures

Abstract

A novel concentration-thermal swing adsorption process is described for separation of bulk binary liquid mixtures. The process is designed to produce essentially two pure products with high recoveries of both components. It is particularly suited for separation of azeotropic or close-boiling liquid mixtures which are difficult to separate by distillation. An example of the performance of the new process for separation of an azeotropic water-methyl acetate mixture is given. Experimental binary surface excess equilibrium isotherms, adsorptive mass transfer coefficients, and column dynamics for adsorption of water-methyl acetate mixtures on NaX zeolite are reported.     

Gene Mutation Profiles in Primary Diffuse Large B Cell Lymphoma of Central Nervous System: Next Generation Sequencing Analyses

The existence of a potential primary central nervous system lymphoma-specific genomic signature that differs from the systemic form of diffuse large B cell lymphoma (DLBCL) has been suggested, but is still controversial. We investigated 19 patients with primary DLBCL of central nervous system (DLBCL CNS) using the TruSeq Amplicon Cancer Panel (TSACP) for 48 cancer-related genes. Next generation sequencing (NGS) analyses have revealed that over 80% of potentially protein-changing mutations were located in eight genes (CTNNB1, PIK3CA, PTEN, ATM, KRAS, PTPN11, TP53 and JAK3), pointing to the potential role of these genes in lymphomagenesis. TP53 was the only gene harboring mutations in all 19 patients. In addition, the presence of mutated TP53 and ATM genes correlated with a higher total number of mutations in other analyzed genes. Furthermore, the presence of mutated ATM correlated with poorer event-free survival (EFS) (p = 0.036). The presence of the mutated SMO gene correlated with earlier disease relapse (p = 0.023), inferior event-free survival (p = 0.011) and overall survival (OS) (p = 0.017), while mutations in the PTEN gene were associated with inferior OS (p = 0.048). Our findings suggest that the TP53 and ATM genes could be involved in the molecular pathophysiology of primary DLBCL CNS, whereas mutations in the PTEN and SMO genes could affect survival regardless of the initial treatment approach.     

Study of supercritical three-phase methanol synthesis with n-hexane at supercritical state

A process of supercritical three-phase methanol synthesis on a Cu-based catalyst C302-2, which has high activity at low temperature and low pressure, has been carried out in a mechanically agitated slurry reactor with paraffin as the inert liquid medium and n-hexane as the supercritical medium. The reaction conditions are as follows: pressure ranging from 6.0 to , temperature ranging from 235 to and mass space velocity from 450 to . The influences of these conditions on the conversion of CO and the outlet methanol mole fraction have been investigated in detail. The results show that both the conversion of CO and outlet methanol mole fraction decreased when the mass space velocity and the temperature were increased under the condition of supercritical n-hexane. In addition, we compared the three-phase slurry bed methanol synthesis with and without supercritical medium. The results show that the conversion of CO, CO₂ and H₂ as well as outlet methanol mole fraction of supercritical three-phase methanol synthesis are obviously higher than those chemical equilibrium values of gas-solid reaction under the corresponding experimental condition. That is to say, the process of supercritical three-phase methanol synthesis with n-hexane at supercritical state can remove the limitation of chemical reaction balance of the reversible exothermic methanol synthesis reaction on the conversion of reactants by introducing a supercritical medium that plays an important role in the reaction-separation coupling process in methanol synthesis, by which the conversion of reactants and outlet methanol mole fraction at supercritical condition are increased greatly. Therefore, they are higher than those of three-phase methanol synthesis without supercritical n-hexane. The advantage of supercritical three-phase methanol synthesis is self-evident. Our present study provides an experimental foundation for further engineering exploitation research on the three-phase methanol synthesis process with supercritical medium in three-phase slurry reactors.     

Polymorphisms in DNA Repair Genes (APEX1, XPD,XRCC1 and XRCC3) and Risk of Preeclampsia in a Mexican Mestizo Population

Variations in genes involved in DNA repair systems have been proposed as risk factors for the development of preeclampsia (PE). We conducted a case-control study to investigate the association of Human apurinic/apyrimidinic (AP) endonuclease (APEX1) Asp148Glu (rs1130409), Xeroderma Pigmentosum group D (XPD) Lys751Gln (rs13181), X-ray repair cross-complementing group 1 (XRCC) Arg399Gln (rs25487) and X-ray repair cross-complementing group 3 (XRCC3) Thr241Met (rs861539) polymorphisms with PE in a Mexican population. Samples of 202 cases and 350 controls were genotyped using RTPCR. Association analyses based on a χ² test and binary logistic regression were performed to determine the odds ratio (OR) and a 95% confidence interval (95% CI) for each polymorphism. The allelic frequencies of APEX1 Asp148Glu polymorphism showed statistical significant differences between preeclamptic and normal women (p = 0.036). Although neither of the polymorphisms proved to be a risk factor for the disease, the APEX1 Asp148Glu polymorphism showed a tendency of association (OR: 1.74, 95% CI = 0.96–3.14) and a significant trend (p for trend = 0.048). A subgroup analyses revealed differences in the allelic frequencies of APEX1 Asp148Glu polymorphism between women with mild preeclampsia and severe preeclampsia (p = 0.035). In conclusion, our results reveal no association between XPD Lys751Gln, XRCC Arg399Gln and XRCC3 Thr241Met polymorphisms and the risk of PE in a Mexican mestizo population; however, the results in the APEX1 Asp148Glu polymorphism suggest the need for future studies using a larger sample size.     

Thermodynamic and structural analyses of the solid phases in multi-alkane mixtures similar to petroleum cuts at ambient temperature

Structural analyses were carried out by X-ray diffraction, at ambient temperature, on multi-alkane samples whose mole fraction distribution shows a shape of the ‘exponential decreasing’ type, as observed in petroleum cuts. Nine samples, whose normal-alkane number varies from 15 to 23, have been studied with mole fraction continuous distributions of normal-alkanes going from C₂₂-C₃₆ to C₁₄-C₃₆: each mixture differs from the previous sample by the addition of a lighter n-alkane. At the solid state, the multi-alkane solid samples C₂₂-C₃₆ and C₂₁-C₃₆ are two-phase, C₂₀-C₃₆ to C₁₅-C₃₆, three-phase, and the broader distribution C₁₄-C₃₆, four-phase. In these polyphase solid systems, whose heaviest n-alkane is always C₃₆, the average composition of the heavy and middle phases are constant and their structure are isostructural to the β′ ordered intermediate solid solution, observed in n-alkane binary or ternary molecular alloys; the mean carbon atom number of the light phase decreases as the global average carbon atom number of the synthetic mixtures in relation to the addition of light n-alkanes and its structure simultaneously evolves from the β′ ordered intermediate solid solution towards the β-RI(Fmmm) and the disordered solid solutions, observed in pure n-alkanes: the light n-alkane added between each distribution intercalates itself into the structure whose molecule stacking period (thickness) is compatible with its own carbon chain length, in order to reduce the molecular gaps.     

The analysis of simultaneous clove/oregano and clove/thyme supercritical extraction

The goal of present work was to investigate and explain kinetics and mass transfer phenomena occurring during the SFE from the mixture of two plants with different initial composition. The extractions from pure clove, oregano and thyme as well as from clove/oregano (C/O) and clove/thyme (C/T) mixtures with various initial compositions of plant material were carried out using supercritical CO₂ at 10 MPa and 40 °C. The results indicated that presence of light compounds in supercritical CO₂ originated from the oregano leaves or thyme at the beginning of extraction process increases the extraction rate of compounds from clove bud. Only small added amounts of oregano or thyme to clove bud (C/O - 90:10%, w/w; or C/T - 84:16%, w/w) in the starting plant mixture had the same effect resulted in the similar and the highest increase of the extraction rate and had negligible influence on total extraction yield compared to extract isolated from pure clove. Different mathematical models were used for simulation of experimental data which showed that the highest increase of the solubility of extractable compounds in supercritical CO₂ as well as the highest mass transfer rate in the solid phase during extractions existed during extraction from C/O (90:10, w/w) and C/T (84:16, w/w) mixtures. Decrease of SC CO₂ consumption or shorter time of extraction necessary for achieving desired extract yield in the case of SFE of the clove buds could be important for industrial-scale application.     

Phase equilibria of mixtures containing CO2 and organic acids using the UMR-PRU model

The UMR-PRU model, which has been successfully tested in the past to the predictions of different type of phase equilibrium and thermodynamic properties in binary and multicomponent systems, is applied in this work to phase equilibria in mixtures containing CO₂ and organic acids. New interaction parameters are determined by fitting only binary vapor–liquid equilibrium data and then they are used to predict the vapor–liquid, solid–gas and solid–liquid–gas equilibria in CO₂/organic acid systems. Furthermore, the UMR-PRU model with the newly derived interaction parameters is applied to the prediction of the phase equilibrium in ternary mixtures consisting of CO₂, organic acids and water. Satisfactory results are obtained in all cases.