Preparation of ZIF-8@PEBAX/PVDF nanocomposite membrane by the combination of self-assembly and in-situ growth for removing thiophene from the model gasoline

Metal-organic frameworks(MOFs)have gained attention in the development of MOFs/polymer hybrid membranes for pervaporation.However,the agglomeration of MOFs particles and interfacial defects limit its further application.In this study,we present a novel approach to fabricate a ZIF-8@PEBAX/PVDF nanocomposite membrane for removing thiophene from the model gasoline by combination of selfassembly and in-situ growth.Firstly,a PVDF supporting membrane was modified to have a negative charge.Next,positively charged zinc ions were attracted onto the negatively charged PVDF supporting membrane through electrostatic interaction.Afterwards,the Zinc ions deposited PVDF membrane was immersed into dimethylimidazole solution to form a uniform ZIF-8 layer.Finally,the ZIF-8 layer was coated with poly(ether-block-amide)(PEBAX)using the pouring method.Experimental results showed that the separating efficiency of the ZIF-8@PEBAX/PVDF nanocomposite membrane was improved significantly compared to that of pristine PEBAX membrane.The optimal permeation flux and enrichment factor of membrane were 27.80 kg(m^(2)h)^(-1)and 6.9,respectively.

Oxidation of Thiophenes over Silica Gel in Hydrogen Peroxide/Formic Acid System

Thiophene C4H4S and 3-methylthiophene3-MC4H4S are typical thiophenenic sulfur compounds that exist in fluid catalytic cracking FCC gasoline. Oxidation of C4H4S and 3-MC4H4S were conducted in hydrogen peroxide H2O2 and formic acid system over a series of silica gel loaded with metal oxide. The silica gel loaded with copper and cobalt 1:1 oxide was found very active for the model compound oxidation using H2O2formic acid, while the silica gel unloaded with metal oxide was less active. The sulfur removal rate of thiophenes was dif- ferent as solvent was changed. And the conversation of C4H4S and 3-MC4H4S was improved at higher temperature, but reduced when olefin was added. The sulfur removal rate of model sulfur compounds was enhanced when the phase transfer catalyst emulsifier polyethylene glycol octyl phenyl ether or tetrabutylammonium bromideTBAB was added. The sulfur removal rate of simulated gasoline containing 524μg·ml-1 sulfur reached 90%. Interestingly, in a H2O2 and formic acid system with the addition of TBAB, a bromine substitution trend appeared in the oxidation of thiophenes, suggesting the influence of TBAB.

Kinetics and Mechanism of the Photo-oxidation of Thiophene by O_2 Adsorbed on Molecular Sieves

Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure. A 500 W high-pressure mercury lamp （main wave length 365 nm, 0.22 kW/m） was used as light source for irradiation, and air was introduced by a gas pump to supply O2. Thiophene can be photo-oxidized to sulfone, oxalic acid, SO4^2-, and CO2. The desulfurization yield of thiophene in n-octane is 58.9% under photo-irradiation for 5 h under the conditions of air flow at 150 mL/min and V（water）：V（n-octane）=1：1. It can be improved to 92.3% by adding 0.15 g zeoliteartificial into 100 mL reaction system, which is the adsorbent for O2 and thiophene. And under such conditions, the photo-oxidation kinetics of thiophene with O2/zeoliteartificial is first-order with an apparent rate constant of 0.5047 h^-1 and a half-time of 1.37 h. The sulfur content can be depressed from 800 μL/L to less than 62 μL/L.

Effects of toluene on thiophene adsorption over NaY and Ce(IV)Y zeolites

Zeolites NaY and Ce（IV）Y were employed as adsorbents to remove organic sulfur compounds from model gasoline （MG） solutions with and without toluene in static adsorption experiments at room temperature （RT） and atmospheric pressure. The adsorbents were characterized by XRD, XRF and pyridine infrared spectrum （IR）. The adsorption experiments show that the desulfurization performance of Ce（IV）Y is much better than that of NaY. The sulfur removal over both NaY and Ce（IV）Y decreases with the increase of toluene concentration in MG, however, the decline tendency on Ce（IV）Y is smooth, and it is steep on NaY. FT-IR spectra of thiophene adsorption indicate that thiophene molecules are mainly adsorbed on NaY via π electron interaction, but on Ce（IV）Y, in addition to the π electron interaction, both Ce^4＋-S direct interaction and protonation of thiophene also play important roles. Toluene molecules are adsorbed on NaY also via π electron interaction. Although the amount of Bronsted acid sites is increased due to the introduction of Ce^4＋ ions into NaY zeolite, it is not found to influence the adsorption mode of toluene over Ce（IV）Y. Compared with NaY zeolite, the improved desulfurization performance over Ce（IV）Y for removing organic sulfur compounds from MG solution, especially those containing large amount of aromatics, may be ascribed to the direct Ce（IV）-S interaction, which is much resistant to the influence resulted from toluene adsorption.

Novel MWCNT-Support for Co-Mo Sulfide Catalyst in HDS of Thiophene and HDN of Pyrrole

With home-made multi-walled carbon nanotubes （MWCNTs, simplified as CNTs in later text） as support, CNT-supported Co-Mo-S catalysts, denoted as x%（mass percentage）MoiCoj/CNTs, were prepared. Their catalytic performance for thiophene hydrodesulfurization （HDS） and pyrrole hydrodenitrification （HDN） reactions was studied, and compared with the reference system sup- ported by AC. Over the 7.24%Mo3Co1/CNTs catalyst at reaction condition of 1.5 MPa, 613 K, C4H4S/H2=3.7/96.3（molar ratio） and GHSV≈8000 mlswP/（g-cat.h）, the specific HDS activity of thiophene reached 3.29 mmolc4H4S/（s.molMo）, which was 1.32 times as high as that （2.49 mmolc4H4S/（s.molMo）） of the AC-based counterpart, and was 2.47 times as high as that （1.33 mmolc4H4S/（s-molMo）） of the catalysts supported by AC with the respective optimal MoaCol-loading amount, 16.90%Mo3Co1/AC. Analogous reaction-chemical behaviours were also observed in the case of pyrrole HDN. It was experimentally found that using the CNTs in place of AC as support of the catalyst caused little change in the apparent activation energy for the thiophene HDS or pyrrole HDN reaction, but led to a significant increase in the concentration of catalytically active Mo-species （Mo^4＋） at the surface of the functioning catalyst. On the other hand, H2-TPD measurements revealed that the CNT-supported catalyst could reversibly adsorb a greater amount of hydrogen under atmospheric pressure at temperatures ranging from room temperature to about 673 K. This unique feature would help to generate microenvironments with higher stationarystate concentration of active hydrogen-adspecies at the surface of the functioning catalyst. Both factors mentioned above were favorable to increasing the rate of thiophene HDS and pyrrole HDN reactions.

Synthesis of New Schiff Bases Containing Thiophene Moiety

Seven new Schiff bases, which are 4,4,4-trifluo-ro-1-(2-thienyl)-1-butanone-3-Z, Z =-thioseraicarbazone (a); -thiocarbohydrazone (b),-benzoic hydrazone (c), -( o-hydroxyphenyl) imine (d) ,-nicotinic hydrazone (e),-salicylic hydrazone (f), and -(p-fluoro-m-chlorophenyl) imine (g), have been synthesized by reaction of 4, 4, 4-trifluoro-1-(2-thienyl)-1,3-butanedione (TFTBD) with corresponding hy-drazides or anilines, acetic acid or p-toluence sulfonic acid as catalyst, and characterized by Elemental analysis, IR, UV-Vis,1H NMR and MS. The MS spectra confirmed that the -C3=O condensed with primary amino group. Tauto-merism of the compounds is discussed.

Photocatalytic Oxidation Kinetics of Thiophene with Nano-F^-/Fe^(3+)/TiO_2

Photocatalytic oxidation kinetics of thiophene in n-octane/water extraction system was studied with fluorine and ferric ion codoped nano-TiO2(nano-F-/Fe3+/TiO2) powders used as the photocatalyst.Effects of initial concentration of thiophene and additional dosage of F-/Fe3+/TiO2 on the reaction rate constant and half-life were investigated.The results showed that the appropriately added dosage of F-/Fe3+/TiO2 was 0.1 g in the 100-mL reaction system and the photooxidative kinetics of thiophene in the presence of F-/Fe3+/TiO2 catalyst was of first-order with a rate constant of 0.6508 h-1 and a half-life of 1.0651 h.The desulfurization rate of thiophene was 98.1%in 5 h and the sulfur content could be reduced from 800 ppm to 15 ppm.The reaction rate constant increased with a decreasing initial concentration of thiophene.

DFT Study of Thiophene Adsorption on the Pd(111) and Pt(111) Surfaces

Thiophene adsorption on the（111） surfaces of Pd and Pt have been investigated by density functional theory.The results indicate that the adsorption at the hollow sites is the most stable.To our interest,the molecular plane of thiophene ring is distorted with C=C bond being elongated to 1.450 and C–C bond being shortened to 1.347 ,and the C–H bonds tilt 13.91～44.05o away from this plane.Furthermore,analysis on population and density of states verified the calculated adsorption geometries.Finally,charge analysis suggests that thiophene molecule is an electron acceptor,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.

Study on Reaction of Thiophene Compounds and Olefins for Deep Desulfurization of Gasoline

The HY,Hβ,HZSM-5,and SAPO-11 zeolites were investigated in the alkylation reaction of thiophene and olefins.As a result,some sulfur-containing impurities could be converted to higher molecular weight components with their boiling point being in the range of diesel fraction.HZSM-5 had the highest activity and selectivity of desulfurization.At the same time,extensive oligomerization of olefins was not found and coke yield was very low,which could lead to high yield of gasoline products.The main reaction mechanism verifies that the second order alkylation reaction can be carried out on the outer surface and/or pores of the catalyst.The catalytic performance of the HZSM-5 catalyst which is poisoned by 2,4-dimethylquinoline during alkylation to form larger molecules of sulfur compounds is obviously weakened due to the decrease of the acid sites on the outer surface and at the mouth of pores.

Hydrodesulfurization of Thiophene on Ni,Mo-supported MCM-41 Catalysts

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NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-(4-ethoxyphenyl) thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-（4- ethoxyphenyl）thiophene （C16Hj2N2OS） are calculated at the HF/6-31＋＋G（d,p） and B3LYP/6- 311 ＋＋G（d,p） levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed, The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.

An asymmetric membrane of polyimide 6FDA-BDAF and its pervaporation desulfurization for n-heptane/thiophene mixtures

Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.

Sulfidation of Ni, Mo-Containing Y Zeolites and Reactivity for Thiophene Hydrodesulfurization

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Vapour–Liquid Equilibrium for N,N-Dimethylformamide + Benzene + Thiophene via Gibbs Ensemble Molecular Simulation

The selection and design of an optimal solvent for extractive distillation require reliable vapour-liquid phase equilibrium data and knowledge of extraction mechanisms.Compared with time-consuming experiments,molecular simulation presents great potential in research on the properties of fluids.Therefore,in this work,Gibbs ensemble Monte Carlo was applied to successfully predict the vapour-liquid phase equilibrium data of binary and ternary systems containing benzene,thiophene and N,Ndimethylformamide(DMF) at P=101.3 kPa.The explicit hydrogen version of the transferable potentials for phase equilibria potential model was chosen for benzene and thiophene,whereas the OPLS potential model was selected for DMF.The predicted phase diagrams were compared with experimental data and the UNIQUAC thermodynamic model.A good agreement was obtained,which corroborated the validity of the potential models.In addition,the extraction mechanism was explored by radial distribution function(RDF) of the liquid-phase structure.The RDFs showed that thiophene and benzene shared a similar liquidphase structure because of the intermolecular interaction.The distinct difference between the RDFs of DMF/benzene and those of DMF/thiophene is that the oxygen atom of DMF is more associated with hydrogen atoms of thiophene than that of benzene,which may be responsible for the extraction effect of DMF.

Mechanism transformation of cyclohexene-thiophene competitive adsorption in FAU zeolite

Competition of hydrocarbon compounds with sulfides in gasoline has caused a not very high selectivity of sulfides in adsorption desulfurization so far,resulting in a reduction of catalyst lifetime as well as more sulfur oxide emissions.Tostudy the whole competitive process changing with the increase of the loading,the dynamic competition adsorption mechanism of cyclohexene and thiophene in siliceous faujasite(FAU)zeolite was analyzed by the Monte Carlo simulation.The results showed that with the increase of the loading,thiophene and cyclohexene had different performances before and after the inflection point of 40 molecule/UC.The adsorbates were distributed ideally at optimal sites during the stage that occurred before the inflection point,which is called the“optimal-displacement adsorption”stage.When approaching the inflection point,the competition became apparent and the displacement appeared accordingly,some thiophene molecules at S sites(refers to the sites inside the supercages)were displaced by cyclohexene.After the inflection point,the concentration of adsorbates at W sites(refers to the 12-membered ring connecting the supercages)was significantly reduced,whereas the adsorbates at S sites got more concentrated.The stage some cyclohexene molecules displaced by thiophene and inserted into the center of the supercage can be named as the“insertion-displacement adsorption”stage,and both the adsorption behavior and the competitive relationship became localized when the adsorption amount became saturated.This shift in the competitive adsorption mechanism was due to the sharp increase of interaction energy between the adsorbates.Besides,the increase in temperature and ratio of Si/Al will allow the adsorbates,especially thiophene molecules to occupy more adsorption sites,and it is beneficial to improve the desulfurization selectivity.

Reformation of thiophene-functionalized phthalocyanine isomers for defect passivation to achieve stable and efficient perovskite solar cells

Lewis acid–base passivation is a significant technique to achieve structural stability of perovskite solar cells(PSCs) by overcoming the issues of wide grain boundaries, crystal defects, and the instability of PSCs. In this work, the combined effects of thiophene with phthalocyanine(Pc) as isomers(S2 and S3)on the photovoltaic performance of PSCs were studied for the first time. Through density functional theory calculations, we confirmed that the position of the S atom in the structure affects Lewis acid–base interactions with under-coordinated Pb^(2+) sites. The morphology of methylammonium lead iodide(MAPbI_(3)) for passivated devices was improved and thin dense layers with compact surface and large grain size were observed, leading to improvement of the charge extraction ability and reduction of non-radiative recombination and the trap density. A highest power conversion efficiency of 18% was achieved for the Pc S3 passivated device, which was 6.69% more than that of the controlled device.Furthermore, the Pcs passivated devices demonstrated remarkable stability under high-moisture and high-temperature conditions.

NOVEL RED LIGHT-EMITTING POLYMERS BASED ON 2,7-CARBAZOLE AND THIOPHENE DERIVATIVES

A series of conjugated copolymers derived from 9-ethylhexyl-2,7-carbazole(Cz)and 4,7-di(4-hexylthien-2-yl)- 2,1,3-benzothiadiazole(DHTBT)was synthesized by Suzuki polycondensation.The photo-and electro-luminescent properties of these polymers were investigated.Efficient energy transfer from the Cz segment to the DHTBT unit occurs even if the DHTBT content as low as 1 mol%.PL emission was red-shifted significantly from 645 nm to 700 nm with the increase in DHTBT content by 1-50 mol%.PL efficiencies decreased...

Reaction Mechanism of Thiophene on Vanadium Oxides under FCC Operating Conditions

The reaction mechanism of thiophene on vanadium oxides under FCC operating conditions hadbeen preliminary studied using in-situ FT-IR analysis of thiophene and atmospheric pressure continuousfixed-bed reaction, followed by characterization via pyridine adsorption-temperature programmed desorptionmethod, and FT-IR and XPS spectra. The research had discovered that, under 500℃ thiophene could undergothe redox reaction with V2O5, while being converted into CO, CO2 as well as SO2 with its conversion ratereaching 41.2%. At the same time the oxidation number of vanadium decreased. The existence of a few Brnstedacid centers on V2O5 could lead to an increase of H2S yield among the products derived from the reaction withthiophene.

Studies on Synthesis and Biological Activities of Novel Triazole compounds Containing Thiophene Groups

Fifteen new triazole compounds containing thiophene groups were synthesized and their structures were confirmed by means of 1H NMR, IR, MS spectroscopies and elemental analyses. The preliminary biological tests show that the titled compounds exhibit some activities of fungicides and plant growth regulators.