Calcium oxide

About: Calcium oxide is a research topic. Over the lifetime, 7600 publications have been published within this topic receiving 66104 citations. The topic is also known as: caustic lime & quicklime.

Soybean Oil Transesterification for Biodiesel Production with Micro-Structured Calcium Oxide (CaO) from Natural Waste Materials as a Heterogeneous Catalyst

Abstract: In this study, micro-structured calcium oxide obtained from the calcination (850 °C for 3 h) of Gallus gallus domesticus (chicken) eggshells was used as a catalyst in the transesterification of soybean oil. This catalyst was characterized by Scanning Electron Spectroscopy (SEM) methods. The structure of the obtained CaO showed several agglomerates of white granular solids with a non-regular and unsymmetrical shape. In terms of calcium oxide catalytic activity, three different catalyst loadings (1%wt, 3%wt, and 5%wt) were tested for the same reaction conditions, resulting in transesterification yields of 77.27%wt, 84.53%wt, and 85.83%wt respectively. The results were compared to the current literature, and whilst they were lower, they were promising, allowing us to conclude that the tendency of yield improvement for this reaction, when the size range of catalyst particles is to be reduced to a nano scale, can be verified.

Mitigating the Effects of Organics in Stabilized Soils: Technical Report

Abstract: The Texas Department of Transportation has reported difficulty stabilizing soils bearing high and low concentrations of organic matter with lime. Problems include: the stabilizer disappearing over time, difficulty measuring organic matter (ignition oven), and rough pavement due to poor subgrade support. The researchers wanted to identify a good test to measure organic matter in soils and identify the problematic fraction of organic matter that causes problems with lime stabilization. Secondly, they wanted to determine what mechanism or mechanisms were responsible for organic matter interfering with lime stabilization. They developed a simple technique to measure the humic acid content of organic matter using a UV-Vis spectrophotometer. They also constructed hundreds of manufactured soils consisting of a humic acid standard mixed with different clay mineral standards, lime, and quartz sand. These soils were used to measure changes in engineering properties as well as monitor chemical changes to elucidate factors controlling reaction mechanisms. From the manufactured soils, the researchers determined that humic acid does interfere with lime stabilization by inhibiting the formation of Calcium Silicate Hydrate reaction products between the lime and clay minerals. This results in reduced unconfined compressive strength values for stabilized cores. The concentration of humic acid that inhibits the formation of pozzolanic reaction products is around 1 percent. Calcareous soils containing organic matter appear to respond better to lime stabilization than acid soils. This study was the first to provide direct evidence of the effects of organic matter on soil stabilization.

Mineral Composition of Build-up in Cement Kiln Preheater

Abstract: Use of a short rotary kiln with a cyclone preheater allowed the internal recirculation of volatile constituents, essentially consisting of compounds of potassium, chlorine and sulphur. These compounds underwent partial condensation on the raw material grains, composed mainly of calcite. The increasing concentration of volatile constituents created convenient conditions for the crystallization of new phases, particularly sylvite. Beautiful crystals of this phase were formed, probably by the VLS mechanism. Thermal analysis revealed that a liquid phase was formed in the system at the relatively low temperature of about 630°C, which enhanced the reaction of silica with calcium carbonate, and spurrite was formed. Thus, the build-ups were composed mainly of calcite, sylvite and spurrite, and in some cases also of calcium oxide and anhydrite. Sulphospurrite, gehlenite, calcium langbeinite, dicalcium silicate and calcium aluminate, 12CaO·7Al2O3 were found as minor components.

Determination of original free lime content of weathered iron and steel slags by thermogravimetric analysis

Abstract: Iron and steel slags are often used as subbase materials in the construction of highways. Previous studies have suggested that the free lime (CaO) in these subbases is responsible for the deposition of calcium carbonate (tufa) in many highway drains. Clogging of these drains leads to the deterioration of highways. Previous work has shown that if the total original CaO in slags exceeds 1%, the slags will readily produce tufa. Therefore, to classify the tufa-producing potential of these slags, it is necessary to determine the total original CaO. Thermogravimetry (TG) methods were employed and most of the TG plots indicated two major changes in weight loss--dehydroxylation of Ca(OH)2 and dissociation of carbonates. From these changes in weight loss the percentage of CaO was calculated. These calculated percentages of CaO from the TG plot plus the results from the "sugar test" determine the total original percentage of CaO. Five groups are recognized according to the calculated total percentage of CaO: 0%, 3.5 to 5%, 8 to 9%, 10 to 12%, and 24 to 25%. Air-cooled blast furnace slag (0% CaO) is the only slag that should be used as a subbase in highway construction, whereas all others are considered to be harmful and could lead to the formation of tufa. TG methods and the sugar test are excellent and economical ways to characterize the original CaO in slags and the susceptibility of the slags to precipitate CaCO3 in subdrains of highways.