Synthesis and Characterization of White Mineral Trioxide Aggregate Using Precipitated Calcium Carbonate Extracted from Limestone

White Mineral Trioxide Aggregate (WMTA) using precipitated CaCO3 (PCC) from limestone has been synthesized. PCC in calcite structure was extracted from limestone by calcination at 900 °C for 3 h, dissolved in 0.8 M nitric acid solution and followed with carbonation for 60 minutes. PCC was used for the synthesis of WMTA by mixing with tetraethoxyorthosilicate, bismuth oxide, aluminum oxide, catalyst of with HNO3 and NH3 solution and thermally treated at 1100 °C for 3 h. The products were characterized with Thermal Gravimetric Analysis-Differential Thermal Analysis (TGA-DTG), X-ray Diffraction (XRD), Frontier-Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray Fluorescence (XRF). The results showed that the PCC dominated calcite structure was obtained with 75.25% in yield and 99.42% in purity. The WMTA has been successfully synthesized by low thermal treatment at 1100 °C using catalysts of HNO3 and NH3 solution, proven by the presence of tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and Bi2O3 in WMTA.

RECYCLING OF CARBONE OXIDES (CO, CO2) CONVERSION INTO METHANOL AT ATMOSPHERIC PRESSURE OVER MECHANOCHEMICAL ACHTIVATED CUO-ZNO-AL2O3 CATALYST

The catalytic process for methanol production by synthesis gas conversion under the conditions of mechanochemical activation (MCA) of copper-zinc-aluminum oxide catalyst in the temperature range 160–280 °C at a pressure of 0.1 MPa are investigated. The use of mechanical action force is one of the promising ways to improve the activity of heterogeneous catalysts designed to simplify the manufacturing process lines, improving the efficiency of catalytic processes and reduce the cost of the target product. Given the importance of technology for methanol production on copper-zinc-aluminum oxide catalysts and high demand for methanol in the world [1–3], clarification of the peculiarities of the process of methanol production by synthesis gas conversion in terms of mechanical load on the catalyst is important in scientific and applied ways. It is established that specific catalytic activity, performance of methanol synthesis catalyst and the conversion of initial reagents are increased in the conditions of mechanochemical activation, because of the increasing concentration of defects and formation of additional active centers. It is revealed that mechanochemical treatment of copper-zinc-aluminum oxide catalyst can reduce reaction initiation temperature and optimum temperature synthesis by 20–30 °C, and increase the maximum performance of the catalytic system. Increase of the catalyst activity under mechanical stress is explored by increase of defect concentration of crystal lattice of the catalyst, as confirmed by the tests of catalyst surface structure by scanning electron microscopy, Raman spectroscopy and X-ray analysis. A new effective method for synthesis gas conversion into the methanol under conditions of mechanochemical activation of the catalyst can be used in industry as an alternative to methanol production at high pressures.