3/2015
Josef Farták, Ivo Jiříček
The article deals with the properties of straw as fuel for heating plants and determination of unburned carbon. Unburned carbon content in ash samples from heating plants was investigated using thermo gravimetric analysis using Boudouard reaction. This endothermic reaction according does not require pretreatment using acid leaching of the sample to remove carbonates. However, the determination of unburned carbon by this method without prior adjustment is not very versatile. High po-tassium content in samples can cause incomplete conversion of carbon because sintering and the formation of glass deposits at high temperatures. For the rapid determination of moisture in the fuel using FTIR spectrometer, calibration curve was determined. Results showed sufficient accuracy when compared to a standardized method of determining fuel moisture in oven test at 105 °C.
Petr Vozka, Veronika Váchová, Josef Blažek
Catalytic hydrotreating of liquid products from processing of biomass is lately raising a lot of interest in both the academic and the industrial world. This relatively new process has a lot of things to improve. This article summarizes catalysts which are used for hydrotreating based on the available literature. Catalysts are neatly sorted into chapters according to the composition; there is a discussion about catalyst supports as well.
Catalysts based on noble metals do not need to be sulphurized, which is a significant advantage over catalysts based on transition metal sulfides. The great disadvantage is that even a small amount of impurities causes a significant decrease in their activity, also they are expensive. These catalysts are therefore suitable for treatment of the biomass with low sulfur content. Most of used catalysts are bifunctional catalysts based on transition metal sulfides, e.g. Ni-Mo and Co-Mo on alumina. Their production and operating costs are lower comparing to noble metals catalysts. They have a higher resistance to impurities and are suitable for the co-processing of vegetable oils and oil fractions in already ex-isting refineries. Catalyst support is also important in liquid biomass hydrotreating. Today the most common used support is an alumina.
Veronika Váchová, Petr Vozka
Commonly process used for production of biodiesel by transesterification of vegetable oils has many disadvantages, such as formation of oxygenated compounds, which can be hydrolyzed to acidic products (aggressive towards construction materials) and they contain double bonds that significantly impair the oxidative stability of the products. Therefore, hydrotreating of vegetable oil was developed. This process provides non-oxygenated products boiling mainly in the distillation range of diesel fuel and it has additional advantages. There is the possibility of processing vegetable oils and petroleum feedstocks together, absence of hardly processed waste products and opportunity of mixing products from hydrotreating of vegetables oils with petroleum diesel in almost any ratio due to their properties.
The hydrotreating can be used for the treatment of commonly processed vegetable oils (rapeseed, palm and soybean). Nowadays, usage of algae oils, animal fats and waste oils from the food utilization is largely discussed.
The hydrotreating involves several sequential reactions of conversion vegetable oils to fuel. Firstly, the hydrogenation of the double bonds at the alkyl chain of triglyceride takes place. Following step is the cracking of triglycerides to fatty acids and propane. The last step is the conversion of fatty acids to hydrocarbons via hydrodecarboxylation, hydrode-carbonylation and hydrodeoxygenation reactions. All of these reactions depend on the feedstock used, the catalyst and reaction conditions of the hydrotreating.
Co, Mo, Ni and W sulfides supported on alumina are mostly used catalysts for hydrotreating of petroleum stock and vegetable oils mixture. Noble metal catalysts supported on alumina are used for processing pure vegetable oils. Substantial purity of the raw material is crucial for noble metal, since even small amounts of impurities are able to deactivate the catalyst.
Soukupová Lenka, Kolena Jiří, Šťávová Gabriela, Vráblík Aleš, Bringlerová Nikola
It was the aim of this study to characterize the oil from waste tires pyrolysis by distillation into narrower distillation fractions ant to evaluate the possibility to de-sulphurize the middle distillate fraction boiling between 218 and 300 °C, which can be obtained from the pyroly-sis oil. Desulfurization was carried out in a batch reactor at different reaction conditions. Two-stage hydrotre-atment (the first one with CoMo catalyst the second one with NiW catalyst) at the temperature ranging between 370 – 390 °C and the hydrogen pressure of 12 MPa was performed. Reduction of sulphur content from more than 1 mass % (in the raw oil) to a very low value of 14 mg.kg-1 was achieved by this process.
