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1.
Pure phases of ZAPO-5 and MnAPO-5 were synthesised hydrothermally using triethylamine as a structure directing agent. The estimation of acid sites (Brönsted and Lewis) in ZAPO-5 and MnAPO-5 was done by TPD measurements of n-butylamine. The alkylation of ethylbenzene (EB) with 2-propanol over the catalysts was studied in a fixed-bed reactor at atmospheric pressure and 250–400 °C. p-Isopropyl ethylbenzene (p-IPEB) and m-isopropyl ethylbenzene (m-IPEB) were the products formed. MnAPO-5 was found to be more active than ZAPO-5. MnAPO-5 registered 11% yield of p-IPEB and 5.8% yield of m-IPEB at 350 °C.  相似文献   

2.
Highly crystalline cobalt aluminophosphates of type 36 have been synthesized and characterized. Investigations on the thermal decomposition of Pr3N-CoAPO-36 and the surface, sorption, acid strength distribution, acidic and catalytic properties of CoAPO-36 were carried out. The XPS analysis indicated that the concentration of cobalt was higher in the bulk of the material than on the surface. The surface of the cobalt aluminophosphate is aluminium rich. The number of strong acid sites is higher on the CoAPO-36 than on CoAPO-5, MAPO-5 and ZAPO-36. The catalytic activities of CoAPO-5, MAPO-5, ZAPO-36, CoAPO-36, MAPO-36 and MAPSO-36 in the 3-methylpentane ando-xylene conversion reactions were compared. The catalytic turnover rate per framework substituted atom in the conversion ofo-xylene for CoAPO-36 is higher than for the MAPO-5, CoAPO-5, ZAPO-36 and MAPSO-36. In the ethylbenzene conversion reaction, the deactivation of the cobalt aluminophosphate and magnesium aluminophosphates of type 36 were studied.  相似文献   

3.
This paper is focused on establishing the grafting products of diethylmaleate onto ethylene-α-olefin copolymers of varying comonomer contents. Several commercial ethylene/α-olefin copolymers ranging in comonomer contents from 0.35 to 3.70 mol% were used, as well as a hydrogenated polybutadiene (HPB) with a 1,2 unit content of 13.9 mol%. The polymers were functionalized with DEM in solution. The experimental techniques employed to verify the grafting and to ascertain the exact positioning of the insertion with respect to the branching points were: Fourier transform infra red spectroscopy (FTIR), carbon 13 nuclear magnetic resonance (13C NMR) and Distortionless enhancement polarization transfer NMR (13C NMR-DEPT). Thermal fractionation was performed by Differential Scanning Calorimetry (DSC) employing the successive self-nucleation and annealing technique (SSA).The results obtained show that the DEM insertion onto polyethylene chains occurs in secondary carbons of the main chain regardless of the copolymer branch type and content. The reasons for this behavior may be related to a statistical factor being involved in the peroxide radical attack since there is an excess of secondary carbons as compared to tertiary ones per PE chain. Also, steric effects produced by the size of the DEM molecules are probably involved in the DEM insertion step. Our 13C NMR-DEPT results suggest that DEM not only avoids the tertiary carbons where the branches are located but also, in polyethylenes with less than 4 mol% branch content, it prefers to insert in the secondary carbons that are at least 5 carbon atoms away from the branch point. In those cases where unsaturations are present in PE chain ends, FTIR shows that they can also be depleted by DEM grafting. However, in the HPB case where no unsaturations are present and the branching content is very high, the insertion still occurs only in the secondary carbons of the main chain. The thermal fractionation performed by SSA corroborated the aforementioned results since the fractions with the longest linear chains were always the first to be depleted by the grafting reactions.  相似文献   

4.
The aim of this study is to synthesize and finely characterize montmorillonite samples, dioctahedral smectites without tetrahedral charges (structural formulae Nax(Al(2 − x)Mgx)Si4O10(OH)2), to allow their use as reference samples in clay science. The montmorillonites synthesis under hydrothermal conditions at different pressures and with various layer charge deficit has been attempted. The temperature was fixed at 320 °C, the pressure parameter values were 20 MPa, 80 MPa, 120 MPa and 200 MPa. The Mg content varied from 0.25 to 0.60 per half unit cell. The reaction products have been characterized with multi-technique analyses (ICP-AES, EMP, CEC, XRD, FTIR, NMR and TGA).Montmorillonite phase was only produced at 120 and 200 MPa.At 20 and 80 MPa, the results suggest that a 0.33 and 0.16-tetrahedral charge deficit exist in the formed samples. Moreover, the octahedral occupancies are higher than two (2.15 and 2.07 at 20 and 80 MPa respectively). In these experimental conditions, the synthetic smectites are mixtures between montmorillonite, beidellite and saponite.At 120 MPa and for a Mg content of 0.25 or higher than 0.33, the synthetic products were also mixtures of smectites. Tetrahedral charge deficits of 0.11, 0.11 and 0.15 were found for Mg contents of 0.25, 0.50 and 0.60 respectively. The octahedral occupancy was also higher than 2.00.A montmorillonite phase with only octahedral charges and an octahedral occupancy near 2.00 was synthesized for a Mg content of 0.33 and at pressures equal to or higher than 120 MPa. This low charge reference smectite shows a very low amount of accessory minerals and an octahedral charge deficit only created by the presence of magnesium in the structure. This montmorillonite can be compared structurally to the most studied natural one: the montmorillonite SWy-2 from Wyoming.  相似文献   

5.
Guangbo He 《Polymer》2004,45(20):6813-6822
Phenol-urea-formaldehyde (PUF) resole resins were synthesized and analyzed by both liquid and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The liquid 13C NMR analysis indicated that the co-condensation reactions between the phenolic ring and the urea unit occurred during the synthesis of the resins. The addition of the urea component effectively reduced the free formaldehyde content in the resin systems. Methylene ether bridges in the resins were found to be mainly associated with the urea units. pH had significant influences on the structure and composition of the resins. Solid-state 13C NMR measurements of the cured resins suggested that the pH probably affected the curing mechanism. A longer time and a higher temperature can generally accelerate the curing process and increase the rigidity of the cured network.  相似文献   

6.
An inertinite-rich medium rank C bituminous South African coal was utilized to generate chars in a pipe-reactor combustion unit. This unit generates chars at atmospheric pressures and temperature was controlled with N2 to a maximum of 1250 °C. Chemical structural changes were investigated at different reaction zones identified in the pipe-reactor combustion unit. A combination of FTIR, XRD and Solid State NMR experiments were used to characterize the coal/char/ash fractions produced in the reactor. These techniques revealed that the coal structure becomes disordered in the drying zone as well as in the beginning of the pyrolysis zone in the reactor. As the temperature increases towards the base of the reactor the coal structure becomes more ordered and well aligned until char is formed and converted. Major structural changes were seen to occur in the drying to the pyrolysis zones. Structural changes within the molecular core were observed with FTIR and XRD results obtained from samples taken from the drying zone to the combustion zone. However, 13C CP/MAS and dipolar dephasing experiments were not able to corroborate these structural changes of the coal/char/ash fractions produced in the reactor occurring in the reduction and combustion zones.  相似文献   

7.
Lithium transition-metal oxides (LiTMOs) such as LiCoO2 and LiMn2O4 were investigated for their use as anode material for the lithium secondary battery. Ni|Li0|LiPF6(lM, EC + DEC (1 : l))|LiTMO|Cu cell was fabricated and its electrochemical properties were examined. LiCoO2 and LiMn2O4 showed fairly good characteristics as anode material as well as cathode material. At the 1st cathodic process, LiCoO2 had a potential plateau at 1.4 V on open circuit potential line, but LiMn2O4 had two ambiguous potential plateaus between 0.6 and 0.1 V. The specific resistance of Li|LiCoO2 cell was 8 ohm-g, but that of Li|LiMn{si2}O{si4} cell decreased gradually while the reaction proceeded. The specific capacities of Li|LiCoO2 and Li|LiMn2O4 cells at the 1st discharge were about 300 mAh/g. Capacity retention of Li| LiMn2O4 cell during charge-discharge cycling was higher than that of Li|LiCoO2 cell.  相似文献   

8.
Perfluorosulfonate ionomer membranes (PFSIs) were cast from Nafion® propanol-water solutions of varying equivalent weights (950, 1100, and 1200 Da) and all annealed at 100 °C under vacuum. Sulfonate group surface concentration on the various membranes and its effect on the adsorption of a cationic polyacrylamide were investigated utilizing X-ray photoelectron spectroscopy (XPS). The cationic polyacrylamide is employed in the microelectronics industry for electroless printed circuit fabrication and may be used to pattern electrodes directly onto the PFSI surfaces for fuel cell miniaturization. Sulfonate surface concentration was found to be well correlated to the sulfonate bulk concentration obtained from the known equivalent weights of the Nafion® solutions. Adsorbed cationic polyacrylamide surface coverage was found to be independent of the immersion time in the adsorbate solution. A wide variation in adsorbate coverage (from 0 to 60% of the surface) occurred over a comparatively small variation in the sulfonate repeat unit surface concentration (from 0 to 20% of the total Nafion® repeat units). Adsorbate coverage goes through a maximum as the sulfonate concentration increases and is consistent with a random, enthalpy-driven adsorption process. Greater sulfonate concentration and lower associated adsorbate coverage was detected on cast membranes than previously found with commercially prepared membranes.  相似文献   

9.
Granular S, finely-ground S, iron sulphate and aluminium sulphate were added at two rates to the surface (0–6 cm) of a soil and acidification and leaching of nutrients were measured over 12 months in a laboratory study. Iron and aluminium sulphate both rapidly lowered soil pH in the top 0–6 cm of the soil. There was little difference in soil pH after 3 and 12 months reaction of these two amendments. In contrast, for granular S and finely-ground S there were clear decreases in soil pH between 3 and 12 months reaction with the soil. Finely-ground S was oxidized in the soil faster than granular S and therefore had a more acidifying effect. The top 0–6 cm of the soil was acidified by all the agents used but the deeper soil was less affected. The only treatments which lowered the pH of the 12–18 cm layer below pH 6 were the high rates of iron and aluminium sulphate. Soil acidification resulted in a decrease in exchangeable Ca, Mg and K, an increase in exchangeable Al and a decrease in effective CEC in the acidified soil layers.At both levels of addition, total ionic strength of percolates from the soil followed the order: aluminium sulphate = iron sulphate > finely gound S > granular S > control and was higher at the higher rate of addition. The pH values of percolates followed the order: control > granular S > finely ground S > iron sulphate = aluminium sulphate and were lower at the higher rate of addition. For the amended soils there was a very close relationship between the pattern and total amounts of SO 4 2- and Ca2+ leached.It was concluded that granular S is not an effective acidifying agent since it is oxidized very slowly in the soil and that acidfying agents should be incorporated to the depth that acidification is required.  相似文献   

10.
ABSTRACT

A multistage system comprising an upflow anaerobic sludge blanket (UASB) followed by anoxic unit and then oxic activated sludge (AS) with biofilm is studied in El-Berka WWTP, Egypt. Different organic loading wastewaters of chemical oxygen demand (COD) less than 500 mg/L till 3000 mg/L are tested during the study. The hydraulic retention time (HRT) varies for each loading from 7.5 to 10 to 15 h. The UASB reactor accomplishes the removal efficiency of 50%–70% of influent COD. The overall system performs the removal efficiency of 95% of influent COD and NH4-N. Also, the results are verified by a modified mathematical model.  相似文献   

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