Liquid–liquid equilibria of ternary mixtures of methanol + MEG + n-C5, ethanol + MEG + n-C5, and n-butanol + MEG + n-C5

New liquid–liquid equilibrium data of ternary systems of mono ethylene glycol + n-pentane + methanol, mono-ethylene glycol (MEG) + n-pentane + ethanol, and mono ethylene glycol + n-pentane + n-butanol from 283.15 to 293 K are presented in this work. Binodal curves were obtained by the cloud point titration method. Tie-line compositions were obtained through density and sound velocity measurements of phases in equilibrium. Results show that the solubility increases with temperature in all systems and decreases as the alcohol chain increases. The relative solubility data indicate that the alcohols are more soluble in MEG than in n-C5. The obtained experimental data were successfully correlated using the CPA and the PC-SAFT equation with appropriate binary interaction parameters.     

Phase equilibria of hydrates from ternary mixtures of methane + ethane + propane and methane + propane + carbon dioxide

Hydrate–liquid–vapour (HLV) equilibrium of aqueous clathrates formed from gas mixtures can be complex compared to hydrates formed with single guests. Typically, pressure and temperature are controlled to obtain these data, but for multicomponent systems, it is necessary to control/report more intensive variables, namely, composition. Metastability, manifested as impractically long experimental times, has been reported to be a challenge with some multicomponent systems. We present HLV equilibrium conditions of two ternary gas mixtures: methane + ethane + propane (90:7:3 molar ratio) and methane + propane + carbon dioxide (55:5:40 molar ratio). Conditions varied in the temperature range of 275–285 K and the pressure range of 1.24–4.75 MPa. Experimental standard uncertainties were on average 0.10 K and 0.005 MPa for methane + ethane + propane and 0.19 K and 0.005 MPa for methane + propane + carbon dioxide. Our technique allowed us to bypass the limitations reported in the literature and provided fast, reproducible HLV equilibria for gas-dominated systems.     

Vapor-Phase Dehydration of 1,3-butanediol over CeO2–ZrO2 Catalysts

The dehydration of 1,3-butanediol was investigated over CeO₂–ZrO₂ catalysts prepared by impregnation at temperatures of 325–375 °C. Pure CeO₂ selectively catalyzed the dehydration of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol, while pure ZrO₂, which was less active than pure CeO₂, catalyzed the dehydration to 3-buten-1-ol. In the CeO₂/ZrO₂ catalyst in which CeO₂ was supported on zirconia, the presence of a small amount of CeO₂ suppressed the formation of 3-buten-1-ol and induced the dehydration of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol and the subsequent dehydrogenation of 3-buten-2-ol to form 3-buten-2-one and butanone. The activity would be related to the redox features of CeO₂. The monoclinic phase of zirconia support decreased while the cubic CeO₂ phase increased as CeO₂ content was increased. In contrast, in the ZrO₂/CeO₂ catalyst in which ZrO₂ was supported on cubic CeO₂, only the cubic CeO₂ phase was observed and ZrO₂ species appeared in the form of a solid solution of CeO₂–ZrO₂ with fluorite structure. Regardless of zirconia loading, ZrO₂ species did not affect the catalytic activity of ZrO₂/CeO₂, which was controlled by CeO₂ species.     

Screening of ionic liquids as entrainers for the separation of 1-propanol + water and 2-propanol + water mixtures using COSMO-RS model

The COSMO-RS model was used to screen potential ionic liquids for the separation of aqueous azeotropic mixtures 1-propanol?+?water and 2-propanol?+?water. A combination of 22 cations (involving imidazolium, pyridinium, pyrrolidinium, quinolinium, and ammonium) and 36 anions were investigated. The anions chloride [Cl] and dihydrogen phosphate [H₂O₄P] were found to strongly influence the vapor liquid equilibrium behavior, whereas the ammonium-based cations diethanol ammonium [(Et)₂AMM]⁺ and tetra methyl ammonium [M₄AMM]⁺ were the most promising cations. In addition, the study of mixing enthalpy and excess Gibbs free energy confirmed that the molecular interaction of ionic liquids with water was found to be much larger than that with alcohols 1-propanol and 2-propanol, indicating the presence of a strong hydrogen bonding between the ionic liquids and water. Further, the addition of ionic liquids to the alcohol–water mixture reduces the activity coefficient of water and increases the relative volatility of the mixture, facilitating easier separation. Ionic liquids [(Et)₂AMM][Cl], [(Et)₂AMM][H₂O₄P], [M₄AMM][Cl], and [M₄AMM][H₂O₄P] are expected to be effective entrainers for the separation of the industrially important 1-propanol?+?water and 2-propanol?+?water systems.     

Improved processing stability in the hydrogenation of dimethyl maleate to γ-butyrolactone, 1,4-butanediol and tetrahydrofuran

In the hydrogenation of dimethyl maleate (DMM) to γ-butyrolactone (GBL), 1,4-butanediol (BDO) and tetrahydrofuran (THF), the performance of the process can be negatively affected by (1) fouling and plugging of the unit through deposition of polymeric by-products and (2) activity drop of the Cu/ZnO-based catalysts through structural changes of the active copper phase at reaction conditions. On the basis of thermodynamic data, we calculated the feed compositions required to prevent condensation of reactants and subsequent formation of polyester deposits in the relevant temperature (453-) and pressure (1-) regime. The resulting critical values of the minimum H₂/DMM ratios of the feed, when corrected for capillary effects, were found to be in excellent agreement with the limits as experienced in the processing experiments. Conditions for safe and stable gas-phase processing of DMM in a single stage can thus be predicted. The Cu/ZnO-based catalysts were improved by modifying the thermal pre-treatment. As compared to conventional materials of the same composition, they need less runtime to reach stationary performance levels, and their steady state activities are higher. The yield ratio of GBL to BDO can be adjusted through temperature and total pressure because the corresponding hydrogenation attains thermodynamic equilibrium. The subsequent dehydration to THF can be promoted by applying higher temperatures; however, selectivities to tetrahydrofuran remain low over typical Cu/ZnO catalysts unless additional acid sites are implemented.     

The nature of the deactivation of hydrothermally stable Ni/SiO2–Al2O3 catalyst in long-time aqueous phase hydrogenation of crude 1,4-butanediol

The deactivation of Ni/SiO₂–Al₂O₃ catalyst in hydrogenation of crude 1,4-butanediol was investigated. During the operation time of 2140 h, the catalyst showed slow activity decay. Characterization results, for four spent catalysts used at different time, indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst. The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet. Such carbonaceous species might be eliminated through either direct H₂ reduction or the combined oxidation–reduction methodologies.     

A convenient access to 1,2-diferrocenyl-substituted ethylenes via [3 + 2]-cycloelimination of 2-silylated 4,4,5,5-tetrasubstituted 1,3-dithiolanes

Ferrocenyl thioketones bearing a hetaryl, phenyl or alkyl group as the second substituent react with (trimethylsilyl)diazomethane at ca. ?30°C in THF solution without formation of a stable [3?+?2]-cycloadduct. After the spontaneous evolution of N₂, the corresponding sterically crowded 4,4,5,5-tetrasubstituted 2-silylated 1,3-dithiolanes are formed as products of the second [3?+?2]-cycloaddition of the intermediate thiocarbonyl S-methanide with the starting thioketone. After desilylation by treatment with TBAF, they are converted into the corresponding carbanions, which display different stability depending on the type of substituent. The presence of hetaryl and phenyl groups results in the exclusive formation of 1,2-diferrocenyl ethylenes. In contrast, the presence of methyl groups significantly enhances the stability of the carbanion, which by protonation yields trans-4,5-diferrocenyl-4,5-dimethyl-1,3-dithiolane.     

Microstructure and mechanical properties of in-situ hot pressed (TiB2 + SiC)/Ti3SiC2 composites with tunable TiB2 content

Without impurity phases detected, fully dense (TiB₂?+?SiC)/Ti₃SiC₂ composites have been successfully synthesised by in-situ reaction hot pressing. The effect of TiB₂ content on phase composite, sintering properties, microstructure, and mechanical properties of the composites were thoroughly investigated. With TiB₂ content increasing from 0 to 50?vol.-%, the flexural strength increases first and then decreases, whereas fracture toughness, hardness and modulus show a linear increase. The maximum strength of 826?MPa was obtained at 20?vol.-% TiB₂. On the whole, the (TiB₂?+?SiC)/Ti₃SiC₂ composites exhibit a superior comprehensive mechanical properties superior to other reported Ti₃SiC₂-based composites reinforced by singular reinforcement. The significant strengthening and toughening effect induced by the in-situ incorporated TiB₂ can be ascribed to the unique properties of TiB₂ and the synergistic action of many mechanisms including particle reinforcement, pulling out of grains, crack deflection and grain refinement strengthening.     

TiCl4 immobilized on a composite support SiO2/MgCl2·x(1,4-butanediol)/poly[styrene-co-(acrylic acid)] for ethylene polymerization: The barrier effect of poly[styrene-co-(acrylic acid)]

By immobilizing titanium-based Ziegler–Natta catalyst on composite support, SiO₂/MgCl₂·x(1,4-butanediol)/poly[styrene-co-(acrylic acid)] (SiO₂/MgCl₂·xBD/PSA) and SiO₂/MgCl₂·xBD/PSA/TiCl₄ (SMPT) were synthesized for ethylene polymerization. SiO₂/MgCl₂·xBD/TiCl₄ without PSA was also prepared for comparison. The results of energy-dispersive X-ray analysis, SEM, and thermogravimetric analysis demonstrated that SMPT had a unique core-mantle-shell structure. The PSA layer can be considered as a barrier for the mass-transfer of reactants based on the results of self-diffusion measurement by pulsed field gradient NMR and ethylene polymerization. The polyethylene produced by SMPT showed high molecular weight (MW) and broad molecular weight distribution (MWD). The influences of PSA content, hydrogen, and comonomer on the ethylene polymerization behavior were also investigated. The results further demonstrated that the PSA layer in the composite support had different diffusion capabilities to the reactants. The physical properties of the produced polyethylene implied the possibility to control the MW and MWD of polyethylene by the manipulation of PSA layer. The catalyst fragmentation during ethylene polymerization was also affected by the PSA shell due to its barrier effect. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A comparative investigation on the corrosion degradation of plasma sprayed YSZ and LnMgAl11O19 (Ln = Nd,Sm, Gd) coatings exposed to the molten V2O5 + Na2SO4 salt mixture at 1100 °C

Corrosive attack of the molten 50 wt. % V₂O₅ + 50 wt.% Na₂SO₄ salt mixture has been comparably studied for the APS YSZ and LnMgAl₁₁O₁₉ (LnMA, Ln = Nd, Sm, Gd) thermal barrier coatings upon a 10 h anneal at 1100 °C in air. The YSZ coating suffered from a deepest infiltration of the molten salt along its thickness direction through the open and connected pores as well as inter-lamellae microcracks. A large number of newly formed voids were widely distributed in the YSZ coating due to the corrosion degradation followed by the t, t’ to m-ZrO₂ phase transformation. While, a relative thin corrosion layer mainly consisting of α-Al₂O₃ and LnVO₄ were present for the corroded LnMA coatings. The much reduced number of open pores and connected microcracks together with the rapid chemical reaction between the molten salt and LnMA coatings, especially for the NdMA coating, preventing further infiltration of the molten salt, was beneficial to mitigate further attacks to the inner coating at the expense of sacrificing a thinner top layer. The presences of amorphous phases were thought to further accelerate the corrosion reaction and strengthen such a corrosion protection mode for all the APS LnMA coatings.     

Mechanistic Study of the NO + NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> Reaction on H- and Fe/H-BEA Zeolites Using <Superscript>15</Superscript>N and <Superscript>18</Superscript>O Labeled Species

Reduction of NO by NH₃ over metal-promoted zeolites represents the principal reaction in the selective catalytic reduction (SCR) technology for NOx removal from Diesel engine exhausts. It has been established that addition of ammonium nitrate (AN) to the reaction mixture substantially enhances the rate of this reaction, decreasing the temperature necessary for an efficient deNOx process. Nevertheless, the nature of this effect has not been completely elucidated. To investigate the NO?+?AN reaction mechanism, we have used individual reactants labeled with either ¹⁵N or ¹⁸O (or both isotopes), thus obtaining an experimental background for proposing the route of the SCR accelerated by AN addition. For this study, we have used as the catalysts H-BEA and Fe/H-BEA zeolites with various Si/Al ratios and various amounts and states of the iron species.