Studies on the Binary MgO/SiO2 Mixed Oxide Catalysts for the Conversion of Ethanol to 1,3-Butadiene

The demand for 1,3-butadiene, one of the most important raw materials in the rubber industry, is constantly increasing. The Lebedev process is a classical method of producing 1,3-butadiene from ethanol, which is to be optimized with regard to the mixed oxide catalysts used. In this work, the binary MgO/SiO2 solid system was tested with regard to its optimum chemical composition for the catalytic conversion of ethanol to 1,3-butadiene. Furthermore, novel mesoporous mixed oxides were prepared to investigate their textural, structural, and surface chemical properties as well as the catalytic activity. Nitrogen physisorption, scanning electron microscopy (SEM), and temperature-programmed ammonia desorption (NH3-TPD) measurements were carried out and evaluated. It was shown that the optimum yield of 1,3-butadiene is achieved by using MgO/SiO2 mixed oxide catalysts with 85–95 mol% MgO and not, as suggested by Lebedev, with 75 mol% MgO. The NH3-TPD measurements revealed that the maximum acid-site density is achieved with an equimolar up to magnesium-rich composition. During the synthesis of binary MgO/SiO2 solid systems based on mesoporous MgO, a thermally stable and ordered structure was formed in the autoclave, depending on the carbonate used and on the duration of the treatment.

Modeling the influence of chemical composition on compressive strength behavior of alkali-activated phosphorus slag cement using statistical design

In this study, a statistical experimental design based on response surface methodology (RSM) has been applied to predict and optimize the compressive strength of alkali-activated phosphorus slag in different ages (3, 7, and 28 days). For this purpose, the binder samples were prepared with different molar ratios of SiO2/Na2O (S/N), Na2O/Al2O3(Na/Al), and H2O/Al2O3(H/Al) as alkali activator. Results showed that S/N molar ratio plays its role in early ages of curing and Na/Al molar ratio, and showed its significant effect on 7 and 28 days of compressive strength. H/Al molar ratio had the most significant effect on compressive strength compared to the other parameters. The derived RSM models were statistically adequate and could be used to predict the compressive strength. The optimum chemical composition of activator to obtain the highest compressive strength was achieved as 0.39, 1.34, and 30 for S/N, Na/Al, and H/Al molar ratios, respectively, with compressive strength of 30, 65, and 100 MPa at 3, 7, and 28 days of curing.

Phase Evolution and Microwave Dielectric Properites in the Systems of (Mg1-xCax)2SiO4 Ceramics

In this paper, the microwave dielectric properties in the systems of nominal chemical composition (Mg1-xCax)2SiO4 (0≤x≤0.5)ceramics were investigated, together with their phase evolution. With the increase of x value, the major phase in the ceramic systems gradually changes from Mg2SiO4 to MgCaSiO4, besides with the some secondary phase of MgSiO3 and Ca2MgSi2O7, The relative dielectric constant in the systems of ceramics gradually increased from 6.8 to 8.7. The quality factor of value was well improved, and especially, the absolute value of the ceramic resonant frequency of temperature coefficients was optimized to reach zero, from -61 to +3 . The best optimum chemical composition was equal to 0.4, where the microwave dielectric properties was = 7.2, = 24,170 GHz, = +5 .

Synthesis of Cordierite with Low Thermal Expansion Coefficient

Cordierite is an excellent material with good thermal shock resistance and used at high temperature for its low thermal expansion coefficient. Cordierite ceramics were prepared by using talc, alumina and kaolin clay as starting materials. The thermal expansion coefficient, phase composition and microstructure were studied and the results showed that: in order to get samples with low thermal expansion coefficient, the optimum chemical composition was a little rich in Al2O3 compared with the theoretical composition, the optimum sintering temperature was 1350°C, and adding 10% starch as pore-forming agent could effectively decreased the thermal expansion coefficient of the samples even to 0.8×10-6/°C. The samples contained majority of cordierite phase, with trace mullite and glass, the acicular cordierite crystals in samples developed very well and there were 10% starch powder used as pore-forming agent in formula. All these were the reasons to decrease the thermal expansion coefficient of cordierite material.