Lixin Xia

Demulsification of emulsions exploited by enhanced oil recovery system

Experimental data are presented to show the influence of the enhanced oil recovery systems components, alkali, surfactant, and polymer, on the demulsification and light transmittance of the water separated from the emulsions. Among which, the effects of surfactants, polyoxyethylene (10) alkylphenol ether (OP‐10) and sodium petroleum sulfonate (CY‐1) on emulsion stability, are the strongest of any component, the effects of polymer, hydrolytic polyacrylamide (HPAM) 3530S, on emulsion stability are the weakest. This research also suggests a possible emulsion minimization approach, which could be implemented in refineries utilizing microwave radiation. Compared with conventional heating, microwave radiation can effectively enhance the demulsification rate by an order of magnitude and increase the light transmittance of the water separated from the emulsions. The demulsification efficiency may reach 100% in a very short time under microwave radiation.

Preparation and characterization of an ultrathin carbon shell coating a silver core for shell-isolated nanoparticle-enhanced Raman spectroscopy

A well-designed type of ultrathin carbon shell coating a silver core was prepared for the first time through an alternate adsorption and carbonization method. The obtained ultrathin carbon shell shows prominent advantages, including sufficient uniformity, better chemical stability than silica or alumina, biocompatibility, being free of pin-holes and low cost.

Microwave-assisted synthesis of sensitive silver substrate for surface-enhanced Raman scattering spectroscopy

A sensitive silver substrate for surface-enhanced Raman scattering (SERS) spectroscopy is synthesized under multimode microwave irradiation. The microwave-assisted synthesis of the SERS-active substrate was carried out in a modified domestic microwave oven of 2450 MHz, and the reductive reaction was conducted in a polypropylene container under microwave irradiation with a power of 100 W for 5 min. Formaldehyde was employed as both the reductant and microwave absorber in the reductive process. The effects of different heating methods (microwave dielectric and conventional) on the properties of the SERS-active substrates were investigated. Samples obtained with 5 min of microwave irradiation at a power of 100 W have more well-defined edges, corners, and sharper surface features, while the samples synthesized with 1 h of conventional heating at 40 degrees C consist primarily of spheroidal nanoparticles. The SERS peak intensity of the approximately 1593 cm(-1) band of 4-mercaptobenzoic acid adsorbed on silver nanoparticles synthesized with 5 min of microwave irradiation at a power of 100 W is about 30 times greater than when it is adsorbed on samples synthesized with 1 h of conventional heating at 40 degrees C. The results of quantum chemical calculations are in good agreement with our experimental data. This method is expected to be utilized for the synthesis of other metal nanostructural materials.

Templated high-yield synthesis of Pt nanorods enclosed by high-index {311} facets for methanol selective oxidation

This communication reports a remarkably simple templating method for the preparation of Pt nanorods enclosed by high-index {311} facets. Due to the existence of the high-index facets, the as-prepared Pt nanorods exhibit significantly enhanced catalytic properties toward a methanol selective oxidation reaction, compared with that of 3 nm Pt nanoparticles.

Determination of the Enthalpy of Vaporization and Prediction of Surface Tension for Ionic Liquid 1-Alkyl-3-methylimidazolium Propionate [Cnmim][Pro](n = 4, 5, 6)

With the use of isothermogravimetrical analysis, the enthalpies of vaporization, Δ(g)lH(o)m(T(av)), at the average temperature, T(av) = 445.65 K, for the ionic liquids (ILs) 1-alkyl-3-methylimidazolium propionate [C(n)mim][Pro](n = 4, 5, 6) were determined. Using Verevkins method, the difference of heat capacities between the vapor phase and the liquid phase, Δ(g)lC(p)(o)m, for [C(n)mim][Pro](n = 2, 3, 4, 5, 6), were calculated based on the statistical thermodynamics. Therefore, with the use of Δ(g)lC(p)(o)m, the values of Δ(g)lH(o)m(T(av)) were transformed into Δ(g)lH(o)m(298), 126.8, 130.3, and 136.5 for [C(n)mim][Pro](n = 4, 5, 6), respectively. In terms of the new scale of polarity for ILs, the order of the polarity of [C(n)mim][Pro](n = 2, 3, 4, 5, 6) was predicted, that is, the polarity decreases with increasing methylene. A new model of the relationship between the surface tension and the enthalpy of vaporization for aprotic ILs was put forward and used to predict the surface tension for [C(n)mim][Pro](n = 2, 3, 4, 5, 6) and others. The predicted surface tension for the ILs is in good agreement with the experimental one.

The excited-state multiple proton transfer mechanism of the 7-hydroxyquinoline–(CH3OH)3 cluster

In this paper, the excited-state proton transfer (ESPT) of 7-hydroxyquinoline (7HQ) in hydrogen-donating methanol (MeOH) was investigated theoretically. The change in the calculated primary bond lengths and the infrared spectra of the 7HQ–(CH3OH)3 configuration from the S0 state to the S1 state testify that the intermolecular hydrogen bonds were strengthened in the S1 state. Therefore, we propose two proton transfer (PT) types in which the ESPT reaction occurs along the hydrogen-bonded bridge O7⋯H8–O9 (Type-A) or N1⋯H2–O3 (Type-B). The normal Stokes shift and the large Stokes shift suggest the existence of the enol form 7HQ–(CH3OH)3 and the keto form 7HQ–(CH3OH)3-PT, respectively, and thus that the proton transfer can occur in the excited-state. In order to further study the details of the complicated multiple proton transfer of the 7HQ–(CH3OH)3 cluster, we scanned the potential energy curves for the ground state (S0) and the excited state (S1) of the hydrogen-bonded 7HQ–(CH3OH)3 complex along with the hydrogen-bonding coordinate (distance of the H2–O3 and H8–O9 bonds). The results show the close barrier height between Type-A (5.35 kcal mol−1) and Type-B (6.65 kcal mol−1), which indicates that the two possible PT types may co-exist and have competition between themselves.

Microwave-Assisted Chemical Demulsification of Water-in-Crude-Oil Emulsions

Two case studies are presented that shows the effects of chemical demulsifiers used under conventional heating and in combination with microwave radiation on efficiency of demulsification and light transmittance of the water separated from the emulsions. The data shows that the chemical demulsifiers coupling with microwave radiation does a better job at demulsifying the water-in-crude-oil emulsions than when the chemical demulsifiers are used under conventional heating. The demulsification efficiency of AE-121 could reach 100% under microwave irradiation (300 W) for 50 seconds.

Catalytic Janus Nanosheets based Emulsion for Ultra-deep Desulfurization

Catalytic Janus nanosheets were synthesized by using an anion-exchange reaction between heteropolyacids (HPAs) and the modified ionic-liquid (IL) moieties of Janus nanosheets. Their morphology and surface properties were characterized by using SEM, energy-dispersive spectroscopy (EDS), FTIR spectroscopy, and X-ray photoelectron spectroscopy (XPS) studies. Because of their inherent Janus structure, the nanosheets exhibited good amphipathic character with ILs and oil to form a stable ILs-in-oil emulsion. Therefore, these Janus nanosheets can be used as both emulsifiers and catalysts to perform emulsive desulfurization. During this process, sulfur-containing compounds at the interface could be easily oxidized and efficiently removed from a model oil. Application of this Janus emulsion brings an efficient, useful, and green procedure to the desulfurization process. Compared with the desulfurization catalyzed by using HPAs in a conventional two-phase system, the sulfur removal of dibenzothiophene (DBT) achieved in a Janus emulsion system was improved from 68 to 97 % within 1.5 h. Moreover, this emulsion system could be demulsified easily by simple centrifugation to recover both the nanosheets and the ILs. Owing to the good structural stability of the Janus nanosheets, the sulfur removal efficiency of DBT could still reach 99.9 % after the catalytic nanosheets had been recycled at least six times.

Self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol adsorbed on silver nanoparticles: Surface-enhanced Raman scattering study.

Self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles were investigated experimentally with surface-enhanced Raman scattering (SERS) and theoretically with density functional theory (DFT) and finite difference time domain (FDTD) method. The absorption spectroscopy of 1,4-BDT in silver sol at different time intervals was measured, which give the indirect evidence of self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles. To obtain the direct evidence of self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles, the SERS of 1,4-BDT were measured experimentally and investigated theoretically. The appearances of S-S stretching band (revealing the formation of multilayers of 1,4-BDT), and strongly enhanced S-C stretching, C-C ring stretching vibrational modes clearly show self-assembled dynamics of 1,4-BDT.

Highly efficient and selective hydrogenation of chloronitrobenzenes to chloroanilines by H2 over confined silver nanoparticles

Ag NPs with sizes ranging form 5–6 nm confined into mesoporous silica SBA-15 (Ag-NPs/SBA-15) are successfully prepared by a facile and rapid glucose/glycol assisted one-step vacuum impregnation method. The as-prepared Ag-NPs/SBA-15 catalyst shows very good activity and selectivity for hydrogenation of chloronitrobenzenes to the corresponding chloroanilines by H2 compared with that of the SiO2 supported Ag catalysts. The robust catalytic performance of the as-prepared Ag-NPs/SBA-15 catalyst displays its potential application for the production of chloroanilines in the fine chemicals industry.