Experimental study on flow characteristics of tetrahydrofuran hydrate slurry in pipelines

Tetrahydrofuran（THF） was selected as the substitute to study the flow behaviors and the mechanism of the hydrates blockage in pipelines.The slurrylike hydrates and slushlike hydrates are observed with the formation of hydrates in pipeline.There is a critical hydrate volume concentration of 50.6% for THF slurries and pipeline will be free of hydrate blockage while the hydrate volume concentration is lower than the critical volume concentration;otherwise,pipeline will be easy to be blocked.Fully turbulent flow occurs and friction factors tend to be constant when the velocity reaches 1.5 m/s.And then,constant values of friction factors that depend on the volume concentrations in the slurry were regressed to estimate the pressure drops of THF hydrate slurry at large mean velocity.Finally,a safe region,defined according to the critical hydrate volume concentration,was proposed for THF hydrate slurry,which may provide some insight for further studying the natural gas hydrate slurries and judge whether the pipeline can be run safely or not.

Synthesis of Tetrahydrofuran and Tetrahydropyran Derivatives Catalyzed by Tungstophosphoric Acid in Ionic Liquid

Synthesis of tetrahydrofuran and tetrahydropyran derivatives catalyzed by tungstophosphoric acid （H3PW12040） were conveniently performed with high yield from the corresponding unsaturated alcohols in ionic liquid. Sufuric acid （H2SO4）, trifluoromathanesulfonic acid （TfOH） and p-toluenesulfonic acid （TsOH） were also explored for preparing these products in ionic liquid. The catalysts and ionic liquid can be easily recovered and reused.

Accelerated nucleation of tetrahydrofuran(THF)hydrate in presence of ZIF-61

Clathrate hydrate can be used in energy gas storage and transportation, CO2 capture and cool storage etc. However, these technologies are difficult to be used due to the low formation rate and long induction time of hydrate formation. In this paper, ZIF-61 （zeolite imidazolate framework, ZIF） was first used in hydrate formation to stimulate hydrate nucleation. As an additive of clathrate hydrate, ZIF-61 promoted obviously the acceleration of tetrahydrofuran （THF） hydrate nucleation. It shortened the induction time of THF hydrate formation from 2-5 h to 0.3-1 h mainly due to the template function of ZIF-61 by which the nucleation of THF hydrate has been promoted.

CATIONIC RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN WITH KEGGIN-TYPE HETEROPOLYCOMPOUNDS AS SOLID ACID CATALYSTS

Three Keggin-type heteropolyanions, namely H3PMo12O40-13H2O, （NH4）3PMo12O40·4H2O and H3PW12O40·13H2O were prepared and tested in the ring-opening polymerization reaction of tetrahydrofuran. The effects of the counter-cation （H＋, NH4＋） and the peripheral atoms （Mo, W） on the polymerization were investigated. It has been found that when the protons of H3PMo12O40·13H2O were replaced by the ammonium cations the polymerization rate decreased dramatically. Whereas, when the peripheral atoms （Mo） were replaced by their homologous （W）, the polymerization rate increased twofold. As for the viscosity average molecular weight （My） of polymer products, it was found that the high molecular weight （7930） was obtained by using H3PW12O40·13H2O. The molecular weight （My） obtained by H3PMo12O40·13H2O and （NH4）H3PMo12O40·13H2O was 6470 and 6810, respectively.

The detection of tetrahydrofuran hydrate formation and saturation using magnetic resonance imaging technique

Tetrahydrofuran（THF） hydrate was formed in bulk as well as in glass beads pack with a mean diameter of 3.0 mm by controlling the temperature under ambient pressure.Images of THF hydrate formation procedure were obtained using the magnetic resonance imaging（MRI） technique.The experiment results showed that MRI is an effective method for the detection of hydrate formation.Saturation of hydrate formed both in bulk and glass beads can be confirmed by intensity integration of MRI images.

Tetrahydrofuran Ring-opening with Acyloxyphosphonium Bromide Catalyzed by Zinc Bromide: An Effective Method for the Preparation of 4-Bromobutyl Esters

Catalyzed by zinc bromide, tetrahydrofuran ring can be opened with acyloxyphos- phonium bromide generated in situ to afford 4-bromobutyl esters under mild conditions in good to excellent yields.

PHOTOCOPOLYMERIZATION OF MALEIC ANHYDRIDE AND VINYL ACETATE IN TETRAHYDROFURAN~*

The copolymerization of maleic anhydride and vinyl acetate in tetrahydrofuran was studied. Results show that the maximum copolymerization rate is in 0.6 mole fraction of maleic anhydride, indicating the involvement of maleic anhydride-tetrahydrofuran charge transfer complex in the chain initiation process. ESR study provides collateral evidence for the formation of maleic anhydride radical and tetrahydrofuran radical.

HYDROGEN STORAGE PROPERTIES OF Mg MODIFIED WITH TETRAHYDROFURAN

The hydriding and dehydriding behaviors of tetrahydrofuran modified Mg,its electronic struc- ture,crystal structure,micro-morphology as well as its stability have been investigated.The modifield Mg absorbs 3.5 wt-％ hydrogen at 643 K in 3.5 MPa H_2,its hydride gives off 3.2 wt-％ hydrogen at 643 K in a vaccum of 1.3 Pa after 20 cycles of hydriding and dehydriding. Tetrahydrofuran alters the electronic structure of Mg but keeps its crystal strueture unchanged.In hydriding products,a new hydride phase is found in addition to the known MgH_2 phase.The hydride formed from Mg is polv-erystalline.The wide-spreading slip bands and twins within crystals indicate that the transformation during absorption of hydrogen causes serious lattice distortions.

Hydriding-dehydriding properties of Mg_2Ni alloy modified by ball-milling in tetrahydrofuran

A new approach of ball-milled Mg_2Ni in tetrahydrofuran (THF) to improve thehydriding kinetics of Mg_2Ni alloy is suggested and studied. It is found that the modified alloydisplayed the improved activity for hydriding even at relatively low temperature (e.g., 323-373 K).In the case of the sample milled in THF for 20 h, the hydrogen content (mass fraction) reaches 1.6 %at 323 K, 2.1% at 348 K and 3.4% at 448 K, respectively. The use of THF during grinding led to thechange of the structure, which is reflected by the broadening and weakening of the diffraction peaksin the XRD spectra. The XPS analysis shows that Mg (2s) binding energy peak of Mg_2Ni aftermodification shifted from a lower binding energy to a higher one, indicating the charge transferencebetween Mg and THF and the formation of catalytically active electron donor-acceptor (EDA)complexes on the surface of modified Mg_2Ni alloy.

Synthesis of 2,5-disubstituted tetrahydrofurans from organozinc halides and lactones

2,5-Disubstituted tetrahydrofurans were obtained from lactones and organozinc halides in moderate to high yield in the presence of Lewis acids.

Microscopic morphology evolution of the crystal structure of tetrahydrofuran hydrate under flowing condition

The evolution of the hydrate particle structure during growth and agglomeration under flowing condition affects the particle as well as flow characteristic,which plays an important role in the flow assurance as well as heat transfer in refrigeration systems.Therefore,this article conducts experiments to study and observe the growth and agglomeration process in the main forming stage of hydrate.It was found that the growth of tetrahydrofuran hydrate was anisotropic and in a layered growth pattern.Single crystals generally transformed from octahedral structure to octahedral skeleton structure with growth,however some single crystals also deformed into plate type particles.The thickness of the plate type particles increased gradually during growth,and the edge part increased earlier than the middle part.During agglomeration,the hydrate particles contacted and sintered together.Sand as the impurity didn’t serve as the nucleation center but affected the agglomeration of hydrate particles by collisions.In addition,the effect increased as the sand size decreased.Finally,a microstructure model for hydrate growth and agglomeration was proposed,which showed the hydrate structure evolution in these processes and could lay a foundation for studying the flow assurance of hydrate slurry.

Liquid-to-glass transition of tetrahydrofuran and 2-methyltetrahydrofuran

Both tetrahydrofuran （THF） and 2-methyltetrahydrofuran （MTHF） are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consistent with experiment. Their glass transition temperatures are obtained： 115 K - 130 K for THF and 131 K - 142 K for MTHF. The calculated results from the dipolar orientational time correlation functions indicate that the ＂long time＂ behavior is often associated with a glass transition. From the radial and spatial distributions, we also find that the methyl has a direct impact on the structural symmetry of molecules, which leads to the differences of physical properties between THF and MTHF.

An Improved Preparation of 2,5-Dimethoxy-tetrahydrofuran

ＡｎＩｍｐｒｏｖｅｄＰｒｅｐａｒａｔｉｏｎｏｆ２，５┐Ｄｉｍｅｔｈｏｘｙ┐ｔｅｔｒａｈｙｄｒｏｆｕｒａｎ＊Ｔｏｗｈｏｍｃｏｒｒｅｓｐｏｎｄｅｎｃｅｓｈｏｕｌｄｂｅａｄｄｒｅｓｅｄ．ＬＩＸｉａｏ－ｌｉａｎｄＣＨＥＮＱｉｎｇ－ｑｉ（Ｄｅｐａｒｔｍｅｎｔ...

Effect of Dissolved CO_2 and Tetrahydrofuran on the Polymerization of Acrylic Acid

The polymerization of acrylic acid (AA) with dissolved carbon dioxide and tetrahydrofuran (THF) in the monomer is studied. Viscosity measurement. differential scanning calorimetry (DSC). and scanning electron microscopy (SEM) indicate that the conccntration of tctrahydrofuran has pronounced effect on the molecular weight (Mn). glass transition temperature (Tg). and the morphology of the product.

Pig Liver Esterase-catalyzed Hydrolysis of Three Diesters of meso-Bicyclic Dicarboxylic Acid and Three Tetraesters of Tetrahydrofuran -2,3,4,5-tetracarboxylic Acid

Three diesters of exo- syn-meso-oxabicyclo (2, 2, 1 ) -hept- 5- ene- 2, 3- dicarboxylic acid and three tetraesters of tetrahydrofuran-2, 3, 4, 5-tetracarboxylic acid were synthesized and tested with enantioselective hydrolysis catalyzed by pig liver esterase(PLE). The results of the PLEcatalyzed hydrolysis were discussed.

Synthesis and Crystal Structure of (Z)-Ethyl-4-(4-methoxy)benzylidene-2-(3,5-dimethoxypheny-tetrahydrofuran-3,3-dicarboxylate

The title compound （Z）-ethyl-4-（4-methoxy）benzylidene-2-（3,5-dimethoxyphenyl）- tetrahydrofuran-3,3-dicarboxylate has been synthesized, and its crystal structure was characterized by X-ray single-crystal diffraction. The crystal belongs to triclinic, space group P1, with a = 8.140（3）, b = 11.966（4）, c = 13.771（5）Aα= 67.366（4）, β= 85.165（5）, γ= 75.806（4）°, V = 1200.1（7） A3, Z = 2, C26H3008, Mr = 470.50, Dc = 1.302 g/cm^3, F（000） = 500,λ（MoKa） = 0.71073 A, μ= 0.096 mm^-1, R = 0.0659 and wR = 0.1841 for 3080 observed reflections （I 〉 2σ（I））. As a key intermediate of HIV-1 integrase inhibitor, the synthesis and structure confirmation of the title compound are important for further studies.

Borane-Tetrahydrofurane Complex Reduction of Nickel and First Transition Metals in Tetrahydrofurane Media: Controllable Chemistry Leading to Nanoscale Metal and Metal Boride Particles

Nickel borides doped with transition metal (Cr, Mn, Fe, Co, Cu, and Zn) MNiB, 4% w/w respect to Ni were prepared by chemical reduction of nickel and metallic salts in methanol solution with borane-tetrahydrofurane (BH3-THF) complex obtained in aprotic solvent (THF anhydrous). Different techniques were used to characterize these materials. The MNiB amorphous structure was verified by XRD. Thermal treatment in N2 shows Ni°, Ni2 Band NiO phases. Spongy-morphology was evident by SEM studies in all cases. XPS and TEM show that doped and non-doped nickel boride was present as Ni° in metallic state as principal phase and nickel alloying with boron was observed in minor quantities. The oxidation stability, magnetic susceptibility and catalytic effect are correlated with parameters of each dopant metal.

Preparation and Characterization of Tungsten-substituted Molybdophosphoric Acids and Catalytic Cyclodehydration of 1,4-Butanediol to Tetrahydrofuran

A series of tungsten-substituted molybdophosphoric acids(H3PMo12-nWnO40·xH2O) were synthesized and characterized by inductive coupled plasma atomic emission spectroscopy(ICPAES),thermal gravimetry and differential scanning calorimetry(TG-DSC),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),and FTIR pyridine adsorption.The as-prepared heteropoly acids have a Keggin type structure.The synthesis of tetrahydrofuran by reactive distillation and cyclodehydration of 1,4-butanediol was studied using the tungsten-substituted molybdophosphoric acids as catalysts.The results of catalytic test indicated that the catalytic activity increased with the increase in the substitution number(n) of tungsten atom in H3PMo12-nWnO40·xH2O and was constant as the substitution number(n) was more than 8.The catalytic activity increased with the increase in the catalyst loading and the selectivity of tetrahydrofuran was nearly 100%.