Syntheses of Some Carbonates with CO2 under High Pressures Carbonates of the alkali metals and of some transition metals are prepared from their solutions, hydroxides, or oxides by reactions with CO2 using pressures of 600–4500 at and temperatures of 100– 400°C. The carbonates MnCO3, FeCO3, CoCO3, NiCO3, ZrCO3 · 2H2O, Th(CO3)2 · 0.5 H2O and the carbonates of the alkali metals are characterized by infrared spectroscopy and X-ray investigations. The structures of Rb2CO3 (1) and Cs2CO3 (2) are presented. They are both monoclinic, space group P 21/c (No. 14) with a = 5.87 (1), 6.13 (2); b = 10.13 (1), 10.28 (2); c = 7.33 (1), 8.15 Å (2), β = 97.65° (1), 95.85° (2) and Z = 4. 相似文献
Intercalation compounds of vanadyl phosphate with dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) were prepared from VOPO4·2C2H5OH intercalate by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The EC intercalate is stable at ambient conditions, whereas the DMC and DEC intercalates transform to vanadyl phosphate dihydrate. Infrared spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The arrangement of the guest molecules in the interlayer space was proposed. 相似文献
Three interconnected catalytic cycles account for the title reaction catalyzed by a bimetallic aluminum(salen) complex and Bu4NBr. In the first, Bu4NBr acts as a nucleophile to activate the epoxide. In the second, Bu3N generated in situ serves to activate CO2. In the third, the aluminum(salen) complex brings the two activated species together so that the key bonds can be formed intramolecularly.
Pressureless sintering of CaCO3 was carried out, with Li2CO3 (from 0.5 to 8 wt%) as an additive, under different pressures of CO2. Densification occurs between 600 and 700°C. Sintering above the eutectic temperature (T>662°C) leads to the decomposition
of calcium carbonate and the materials become expanded. At 620° under 1 kPa of CO2, a relative density of 96% is reached. Li2CO3 enhances the densification process and grain growth of calcium carbonate. CO2 pressure slows down densification and grain growth kinetics. These results are explained by the influence of carbonate and
calcium ion vacancies on the sintering mechanisms.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献