Preparation of CuCl/C catalyst for the synthesis of dimethyl carbonate: Effects of calcination temperature

Activated carbon supported cuprous chloride, a rarely examined catalyst, was prepared and applied to the oxidative carbonylation of methanol. The catalyst was prepared by impregnation. Water insoluble cuprous chloride was dissolved in hydrochloric acid. The effects of the calcination temperature in preparing the catalysts were examined. The results showed that, as the temperature was increased, the major surface species in the catalyst shifted from CuCl₃²⁻ to CuCl, then to Cu₂Cl(OH)₃, and finally to Cu⁰. Cuprous chloride appeared to be the active species for the production of dimethyl carbonate (DMC), and maximum amount of cuprous chloride in the catalyst occurred at a calcination temperature of 300 °C.     

The performances of higher alcohol synthesis over nickel modified K2CO3/MoS2 catalyst

Ni modified K₂CO₃/MoS₂ catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H₂/CO (molar radio) = 2.0, GHSV = 3000 h^− 1, and P = 10.0 MPa. Compared with conventional K₂CO₃/MoS₂ catalyst, Ni/K₂CO₃/MoS₂ catalyst showed higher activity and higher selectivity to C₂⁺OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K₂CO₃/MoS₂ was higher, however, it was close to that of K₂CO₃/MoS₂ catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K₂CO₃/MoS₂ catalyst.     

Effects of heating rate on microstructures and microwave dielectric properties of (1 − x)ZnAl2O4–xTiO2 (x = 0.21) ceramics

(1 − x)ZnAl₂O₄–xTiO₂ (x = 0.21) ceramics were synthesized at 1500 °C for 3 h using the solid-state reaction at a heating rate from 1 to 7 °C/min. The effects of heating rate on the microstructure, phase composition and oxidation state of titanium in the ceramics were investigated. The XRD results show that this system is composed of two phases, i.e. ZnAl₂O₄ spinel and rutile. The “black core” phenomenon resulting from reduction of Ti⁴⁺ ion valence appears after the ceramics are sintered at the speed of 1 and 3 °C/min. As the heating rate increases, the density and quality factor (Q·f) increase initially and reach the maximum value when the heating rate is 5 °C/min, and then reduce quickly to the minimum, while the dielectric constant (?_r) and temperature coefficient of resonator frequency (τ_f) nearly do not change. The optimal microwave dielectric properties can be achieved in (1 − x)ZnAl₂O₄–xTiO₂ (x = 0.21) ceramics sintered at a heating rate of 5 °C/min with an ?_r value of 11.6, a Q·f value of 74,000 GHz (at about 6.5 GHz), and a τ_f value of −0.4 ppm/°C.     

Experimental determination of the eutectic temperature in air of the CuO-TiO2 pseudobinary system

Eutectic temperature and composition in the CuO-TiO₂ pseudobinary system have been experimentally determined in air by means differential thermal analysis (DTA), thermogravimetry (TG) and hot-stage microscopy (HSM). Samples of the new eutectic composition treated at different temperatures have been characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structural spectroscopy (XANES) to identify phases and to determine the Cu valence state, respectively. The results show that the eutectic temperature in air is higher by 100 °C (∼1000 °C) for a Ti-richer composition (XTiO₂=25 mol%) than the one calculated in the literature. The reduction of Cu²⁺ to Cu⁺ takes places at about 1030 °C. The existence of Cu₂TiO₃ and Cu₃TiO₄ has been confirmed by XRD in the temperature range between 1045 and 1200 °C.     

Synthesis of hollandite-type LixMnO2 by Li ion-exchange in molten salt and lithium insertion characteristics

The Li⁺ ion-exchange reaction of K⁺-type α-K_0.14MnO_1.93·nH₂O containing different amounts of water molecules (n = 0-0.15) with a large (2 × 2) tunnel structure has been investigated in a LiNO₃-LiCl molten salt at 300 °C. The Li⁺ ion-exchanged products were examined by chemical analysis, X-ray diffraction, and transmission electron microscopy measurements. The K⁺ ions and the hydrogens of the water molecules in the (2 × 2) tunnels of α-MnO₂ were exchanged by Li⁺ ions in the molten salt, resulting in the Li⁺-type α-MnO₂ containing different amounts of Li⁺ ions and lithium oxide (Li₂O) in the (2 × 2) tunnels with maintaining the original hollandite structure.The electrochemical properties and structural variation with initial discharge and charge-discharge cycling of the Li⁺ ion-exchanged α-MnO₂ samples have been investigated as insertion compounds in the search for new cathode materials for rechargeable lithium batteries. The Li⁺ ion-exchanged α-MnO₂ samples provided higher capacities and higher Li⁺ ion diffusivity than the parent K⁺-type materials on initial discharge and charge-discharge cyclings, probably due to the structural stabilization with the existence of Li₂O in the (2 × 2) tunnels.     

Detection of N-methyladenosine in urine samples by electrochemiluminescence using a heated ITO electrode

A sensitive and rapid electrochemiluminescence (ECL) method for the detection of N⁶-Methyladenosine (m6A) in urine samples on a heated indium-tin-oxide (ITO) electrode is presented. The ECL intensity of Tris(2,2′-bipyridyl) dichlororuthenium(II)hexahydrate (Ru(bpy)₃²⁺) can be enhanced by the presence of m6A. Experimental results showed that the change of ECL intensities (ΔI) of the Ru(bpy)₃²⁺ between before and after addition of m6A was affected by the working electrode surface temperature (T_e); the highest ΔI occurred at 31 °C. Under optimum conditions, the ΔI had a linear relationship with the m6A concentration in the range of 1.9 × 10⁻⁹-3.9 × 10⁻⁶ mol/L and a detection limit of 7.7 × 10⁻¹⁰ mol/L (S/N = 3) at T_e = 31 °C. The recovery of m6A standards added to urine samples verified the accuracy of the proposed method.     

Comparison of the superconducting properties of Cu0.5Tl0.5Ba2Ca2(Cu3−yZny)O10−δ prepared at different synthesis temperatures

The superconducting properties of Zn-doped Cu_0.5Tl_0.5Ba₂Ca₂(Cu_3−yZn_y)O_10−δ {CuTlZn-1223} (y=0, 0.83, 1.66, 2.5) samples prepared at 820, 830, 850 and 860 °C have been compared. The samples were investigated by x-ray diffraction (XRD), dc-resistivity, ac-susceptibility and Fourier Transform Infrared (FTIR) absorption measurements. Almost all the superconducting properties have been increased to their maximum in all CuTlZn-1223 samples synthesized at 860 °C, which shows that 860 °C is the optimum temperature to achieve CuTlZn-1223 with enhanced superconducting properties.     

Effect of La-doping on the properties of CaCu3Ti4O12 dielectric ceramics

Nano-size Ca_1−χLa_2χ/3Cu₃Ti₄O₁₂ (χ = 0.00, 0.05, 0.10, 0.15 and 0.20) precursor powders were prepared via the sol–gel method and the citrate auto-ignition route and then processed into micro-crystal Ca_1−χLa_2χ/3Cu₃Ti₄O₁₂ ceramics under heat treatment. Characterization of the as-obtained ceramics with XRD and SEM showed an average grain sizes of ∼1–2 μm, indicating La³⁺ amount to have little impact on grain size. The room-temperature dielectric constant of the Ca_1−χLa_2χ/3Cu₃Ti₄O₁₂ ceramics sintered at 1000 °C was of the order of 10³–10⁴ despite the variation of χ values. Compared with CaCu₃Ti₄O₁₂, La³⁺-doped CaCu₃Ti₄O₁₂ showed a flatter dielectric constant curve related to frequency. It was found that the loss tangent of the Ca_1−χLa_2χ/3Cu₃Ti₄O₁₂ ceramics was less than 0.20 in ∼600–10⁵ Hz region, which rapidly decreased to a minimum value of 0.03 by La³⁺doping with χ = 0.05. Our measurement of the ceramics conductivities (σ) also indicated that the appropriate introduction of La³⁺ into CaCu₃Ti₄O₁₂ would distinctly result in its dielectric properties.     

Comparison of product selectivity during hydroprocessing of bitumen derived gas oil in the presence of NiMo/Al2O3 catalyst containing boron and phosphorus

A detailed experimental study was performed in a trickle-bed reactor using bitumen derived gas oil. The objective of this work was to compare the activity of NiMo/Al₂O₃ catalyst containing boron or phosphorus for the hydrotreating and mild hydrocracking of bitumen derived gas oil. Experiments were performed at the temperature and LHSV of 340-420 °C and 0.5-2 h⁻¹, respectively, using NiMo/Al₂O₃ catalysts containing 1.7 wt% boron or 2.7 wt% phosphorus. In the temperature range of 340-390 °C, higher nitrogen conversion was observed from boron containing catalyst than that from phosphorus containing catalyst whereas in the same temperature range, phosphorus containing catalyst gave higher relative removal of sulfur than boron containing catalyst. Phosphorus containing catalyst showed excellent hydrocracking and mild hydrocracking activities at all operating conditions. Higher naphtha yield and selectivity were obtained using phosphorus containing catalyst at all operating conditions. Maximum gasoline selectivity of ∼45 wt% was obtained at the temperature, pressure, and LHSV of 400 °C, 9.4 MPa and 0.5 h⁻¹, respectively, using catalyst containing 2.7 wt% phosphorus.     

Effect of activation temperature on the surface copper particles and catalytic properties of Cu–Ni–Mg–Al oxides from hydrotalcite-like precursors

The Cu–Ni–Mg–Al oxides catalysts for furfural hydrogenation were prepared from the hydrotalcite-like precursors, and the effect of activation temperature on the Cu⁰ particles and catalytic properties of the catalyst was thoroughly investigated. The catalyst activated by H₂ at 300 °C was found to exhibit the best catalytic activity, due to the presence of the smallest Cu⁰ particles with a high dispersion. Moreover, the bigger Cu⁰ particles were active for furfuralcohol hydrogenolysis to 2-methylfuran in the liquid-phase (ethanolic solution), and the hydrogenation of the furan ring of furfuralcohol and 2-methylfuran on Cu⁰ particles was easily achieved in the vapour-phase.     

Etude des phenomenes electrochimiques et des transports de matiere d'un systeme metal electrolytique: cas d'un disque tournant en cuivre dans des solutions aqueuses d'acide chlorhydrique

In the first two areas of the curves I = F(E) corresponding to Cu/CuCl_x^1?x and Cu/CuCl/CuCl_x^1?x redox systems we study the diffusion of Cl^?, Cu⁺ Cu²⁺ and CuCl_x^1?x species: in acidic chloride media (0,1 Ml^?1 ?HCl ? 3 Ml^?1) the diffusion of Cl^? does not exist because the amount of ions consumed is negligible compared to the large quantities contained in the solution, these HCl solutions behave like supporting electrolyte. Cu⁺ and Cu²⁺ does not exist in the diffusion layer on account of the high Cl^? concentration. At all events the diffusion of CuCl_x^1?x complex is the rate determining step. Experimental current is a pure diffusion current because the transference number tCuCl_x^1?x is negligible compared to one and the charge transfer step is very fast. The electrode surface seems to be uniformly reactive although for the Cu/CuCl/CuCl_x^1?x system we can assume there may be a partially blocked electrode surface constituted by independent sites.     

High-temperature close coupled catalysts Pd/Ce-Zr-M/Al2O3 (M = Y, Ca or Ba) used for the total oxidation of propane

A series of high-temperature close coupled catalysts Pd/Ce-Zr-M/Al₂O₃ (M = Y, Ca or Ba) were prepared by ultrasonic-assisted successive impregnation. The catalysts were subjected to a series of characterization measurements. The results of activity evaluation show that Y is the best promoter for propane total oxidation, especially at the calcination temperature of 1100 °C. It is interesting that although the BET specific surface areas and the dispersion of Pd species decrease, the Y-promoted catalyst calcined at 1100 °C shows higher catalytic activity than the corresponding one calcined at 900 °C and better sulfur-resisting performance. The results of TEM, TPHD and CO chemisorption indicate that Y can remarkably increase the dispersion of Pd species. However, the dispersion is hard to be connected with the activity increase as the calcination temperature is elevated from 900 to 1100 °C. The change of active phases and the interaction between Pd species and the supports may account for the activity enhancement. Combined with XRD, H₂-TPR and O₂-TPD results, it is deduced that the coexistence of metallic Pd and PdO species in the catalysts calcined at 1100 °C may be also favorable to C₃H₈ oxidation. In a word, Pd/Ce-Zr-Y/Al₂O₃ is indeed a promising high-temperature close coupled catalyst applicable to high temperature.     

Well defined CuI(NO), CuI(NO)2 and CuII(NO)X (X = O− and/or NO 2 − ) complexes in CuI-ZSMS prepared by interaction of H-ZSM5 with gaseous CuCl

In this note an exchange procedure of the acidic protons of H-ZSM5 by Cu^I ions through reaction with CuCl in the gas phase is described. In the so obtained Cu^I-ZSM5 exchanged zeolite the Cu^I ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The Cu^I(NO)₂ species are transformed at RT into Cu^II(NO)X (X=O^– and/or NO ₂ ^– ) species which could represent an intermediate in NO decomposition.     

High lithium conductivities in weakly-ionophilic low-dimensional block copolymer electrolytes

The structure of amphiphilic low-dimensional copolymer electrolytes I of similar overall composition but prepared by different synthetic procedures X and Y are described. I are copolymers of poly[2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)] (CmO5) and poly[2,-oxatrimethylene(5-alkyloxy-1,3-phenylene)] (CmO1) where the alkyl side chains having m carbons are hexadecyl or mixed dodecyl/octadecyl (50/50). ¹H NMR shows that the copolymers have 50% (m = 16) or only 18 and 13% of CmO5 units and DSC indicates that the copolymers have ‘block’ sequencing of CmO1 and CmO5 segments. Molecular dynamics modelling indicates that in CmO5 Li⁺ and BF₄⁻ ions are separated by Li⁺ encapsulation in tetraethoxy segments but in ionophobic CmO1 units the salt is mostly present as neutral aggregates decoupled from the polymer. Conductivities of these microphase-separated mixtures with salt-bridge amphiphilic polyethers II and III of each system are similar. They have low temperature dependence over the range 20 °C to 110 °C at ∼10⁻³ S cm⁻¹. ⁷Li NMR linewidth measurements confirm high lithium mobilities at −20 °C. A conduction mechanism is proposed whereby Li⁺ hopping takes place along rows of decoupled aggregates (dimers/quadrupoles) within an essentially block copolymer structure. Subambient measurements to −10 °C gave a conductivity of 4 × 10⁻⁵ S cm⁻¹.     

Structural,morphological and up-converting luminescence characteristics of nanocrystalline Y2O3:Yb/Er powders obtained via spray pyrolysis

Sub-micronic, spherical Y₂O₃:Yb/Er particles comprising clustered nano-units (70 nm) were prepared via ultrasonic spray pyrolysis from pure nitrate precursor solutions with different Yb/Er dopant ratios. The particles were additionally thermally treated at 1100 °C for 12, 24 and 48 h. The structural and morphological characteristics of particles were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray analysis and specific surface area (BET) and were further correlated with their advanced optical properties. For the recorded up-conversion emissions, originating from the following Er³⁺ transitions: [²H_9/2→⁴I_15/2] in blue (407–420 nm); [²H_11/2, ⁴S_3/2→⁴I_15/2] green: 510–590 nm; and [⁴F_9/2→⁴I_15/2] in red (640–720 nm) spectral region, the corresponding lifetimes were acquired in the wide temperature range (10–300 K). The most intense green up-conversion emission with the long decay of 550 ms is recorded for Y_1.97Yb_0.02Er_0.01O₃ particles thermally treated at 1100 °C for 24 h.     

Desulfurization of high-sulfur jet fuel by mesoporous π-complexation adsorbents

Desulfurization of JP-5 jet fuel (1172 ppmw S) was investigated by π-complexation adsorption with AgNO₃ supported on mesoporous silica SBA-15 and MCM-41. The average pore sizes of AgNO₃/SBA-15 and AgNO₃/MCM-41 were 48.8 and 19.1 Å, respectively. The results of JP-5 desulfurization showed that significant sulfur breakthrough occurred at ∼10.0 and ∼15.0 mL/g by AgNO₃/SBA-15 and AgNO₃/MCM-41, respectively, at a space velocity of 1.25 h⁻¹. The spent AgNO₃/MCM-41 was regenerated by a simple process (heating in air at 200 °C) and ∼50% of the sulfur capacity was recovered after the first cycle. Molecular orbital calculations show that Cu⁺ (as that in CuY zeolite) formed stronger π-complexation bonding with the thiophenic compounds than Ag⁺ (in AgNO₃), as evidenced by experimental heats of adsorption. However, pore diffusion limitation of the large sulfur molecules (alkylated benzothiophenes) became an important factor for desulfurization of high sulfur jet fuels such that the AgNO₃-supported mesoporous sorbents yielded substantially better results than Cu(I)Y, although Cu(I)Y was better for a model fuel that contained only small sulfur molecules. Among all sorbents that have been investigated, the AgNO₃/MCM-41 sorbent showed the best desulfurization performance for high sulfur jet fuels.     

Grain boundaries and the influence of the ionophilic-ionophobic balance on Li and F NMR and conductivity in low-dimensional polymer electrolytes with lithium tetrafluoroborate

⁷Li and ¹⁹F NMR linewidths and impedance spectra are reported for low-dimensional CmOn (I):LiBF₄ mixtures. Data for the ionophilic polymer C18O5 is compared with that for the ionophobic C18O1 and the block copolymer C16O1O5(21%) (21 mol% of C16O5). In C18O5:LiBF₄ (1:1) narrow ⁷Li linewidths, which were observed in the liquid crystal phase above the side chain melting temperature (∼50 °C), persist in the crystal down to ca. 0 °C and broaden below −20 °C. However, in C18O1:LiBF₄ (1:0.6) narrow ⁷Li linewidths were also observed down to −20 °C suggesting highly mobile neutral aggregates of salt since this system is non-conductive. In the copolymer C16O1O5(21%):LiBF₄ (1:0.7) the linewidths were even narrower down to −70 °C with weak temperature dependence. In all systems ¹⁹F linewidths were significantly broader than ⁷Li linewidths. The complex plane plots obtained by impedance spectroscopy exhibit characteristic minima identified with ‘grain boundary’ resistance and, following heat treatment, minima with weak temperature dependence identified with ‘internal crystal’ resistance, R_i, and conductivities, σ_i ≥ 10⁻⁴ S cm⁻¹. Four-component mixtures of copolymers CmO1O5 and CmO1O4 with LiBF₄ and ‘salt-bridge’ poly(tetramethylene oxide)-dodecamethylene copolymers gave conductivities of ca. 4 × 10⁻⁴ S cm⁻¹ at 20 °C with weak temperature dependence. A novel carrier-hopping mechanism of lithium transport decoupled from side chain melting in the crystalline state is postulated.      

Direct synthesis of poly(l-lactic acid) in supercritical carbon dioxide with dicyclohexyldimethylcarbodiimide and 4-dimethylaminopyridine

The direct synthesis of poly(l-lactic acid) (PLLA) from an l-lactic acid oligomer has been performed in supercritical carbon dioxide (scCO₂) using an esterification promoting agent, dicyclohexyldimethylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) as a catalyst. PLLA within M_n of 13,500 g/mol was synthesised in 90% yield at 3500 psi and 80 °C after 24 h. The molecular weight distribution of the products was narrower than PLLA prepared with melt-solid phase polymerisation under conventional conditions. Both DCC and DMAP showed high solubility in scCO₂ (DCC: 7.6 wt% (1.63×10⁻² mol/mol CO₂) at 80 °C, 3385 psi, DMAP: 4.5 wt% (1.62×10⁻²mol/mol CO₂) at 80 °C, 3386 psi) and supercritical fluid extraction was found to be effective at removing excess DMAP and DCC after the polymerisation was complete. We show that DCC and DMAP are effective esterification promoting reagents with further applications for condensation polymerisations in scCO₂.     

Photocatalytic degradation of methylene blue with TiO2 nanoparticles prepared by a thermal decomposition process

The generation of TiO₂ nanoparticles by the thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out experimentally using a tubular electric furnace at various synthesis temperatures (700-1300 °C) and TTIP heating temperatures (80-110 °C). The photocatalytic activity of the resulting TiO₂ nanoparticles was examined by measuring the rate of methylene blue decomposition. The TiO₂ nanoparticles were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) measurements and transmission electron microscopy (TEM). The crystallite size and crystallinity increased with increasing synthesis temperature and TTIP heating temperature. A TTIP heating temperature and synthesis temperature of 95 °C and 900 °C, respectively, were found to be the optimal synthesis conditions. The primary particle diameter obtained under optimum synthesis conditions was considerably smaller than the commercial photocatalyst (Degussa, P25). The specific surface areas were more than 134.4 m² g^− 1. Under the optimal conditions, the photocatalytic activity for methylene blue was higher than that of the commercial photocatalyst.     

The interaction effects of dehydration function on catalytic performance and properties of hybrid catalysts upon LPDME process

Three bi-functional catalysts have been prepared by physical mixing of a commercial methanol synthesis catalyst (CuO–ZnO–Al₂O₃) with three different methanol dehydration catalysts including: H-MFI90, γ-Al₂O₃ and H-Mordenite in order to investigate the role of interaction effects of dehydration component on characteristic properties and performance of these admixed catalysts. The bi-functional catalysts have been characterized by XRD, N₂ adsorption, H₂-TPR, NH₃-TPD and XRF techniques and tested in a mixed slurry bed reactor at the same operating conditions (T = 240 °C, P = 50 bar, H₂/CO = 2, SV = 1100 ml g-cat^− 1 h^− 1) for 60 h time on stream. Among the examined bi-functional catalysts, the physical mixture of KMT + HMFI-90, which had lower reducing peak temperature (T = 200 °C), higher S_Cu (39.1 m² g-cat^− 1) and Cu Dispersion (11.6%), showed higher X_CO (84 mol%), yield of DME (Y_DME = 55.5 mol%), DME selectivity (Select_DME = 66.7 mol%) and also good stability over 60 h time on stream as compared to the other catalysts. This could be assigned, from NH₃-TPD results, to more middle strength acidic sites of H-MFI90 zeolite (SiO₂/Al₂O₃ = 90, total acid site density = 476 µmol/g-cat) which inhibits detrimental interactions with methanol synthesis catalyst and deep dehydration of methanol.