Fuels And Combustion Sp Sharma.pdf
Vaniria Setser
Main objective of present work is to study the efficiency of mixed fuel towards solution combustion synthesis of alumina powder, which otherwise prepared by single fuel and study of properties of final product with mixed fuel approach. Two different fuels, glycine and urea, along with aluminium nitrates have been used to prepare nanophase alumina powder. Different fuel to oxidizer ratios and different percentage combination of two fuels were used to prepare six samples. In all samples, nanoscale particle size obtained. Parameter which continuously changes the results of various characterisations is percentage combination of two fuels. In case where percentage of urea is higher than glycine reaction takes place with high exothermicity and hence crystallinity in product phase, whereas glycine promotes amorphous character. With mixed fuel approach, crystallinity can be enhanced easily, by calcinations of powder product at low temperature, because due to mixed urea and glycine, there is already some fraction of crystallinity observed. Overall mixed fuel approach has ability to produce nanophase alumina powder with wide range of particles size.
Aluminium nitrate is a strong oxidising agent. It is used in tanning leather, antiperspirants, corrosion inhibitors, extraction of uranium, petroleum refining and as a nitrating agent. The non-ahydrate and other hydrated aluminium nitrates have many applications. These salts are used to produce alumina for preparation of insulating papers, in cathode ray tube heating elements, and on transformer core laminates. The hydrated salts are also used for the extraction of actinide elements.
Urea or carbamide is an organic compound with the chemical formula CO(NH2)2. The molecule has two NH2 groups joined by a carbonyl (C=O) functional group. It is a colourless, odourless solid, although the ammonia that it gives off in the presence of water, including water vapour in the air, has a strong odour. Used as a fuel in synthesis of various oxides.
Glycine (abbreviated as Gly or G) is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its side-chain, glycine is the smallest of the 20 amino acids commonly found in proteins. Glycine is an intermediate in the synthesis of a variety of chemical products.
Forty-five grams of Al(NO3)3 are mixed with 45 ml of distilled water, dissolve to prepare homogeneous solution using magnetic steerer. Similarly, 9 g of urea in 9 ml of distilled water and 4.5 g of glycine in 18 ml of distilled water.
All the six foamy products formed after solution combustion process are grounded thoroughly to form a homogeneous powder, without agglomerated particles. Powder is used for XRD and SEM characterisation.
From all above observations, we note that in case where percentage of urea is greater than glycine, excellent combustion, without residual carbon contents takes place. Whereas in case, when percentage of glycine is comparable to urea, black product is formed, which indicates incomplete combustion or combustion with residual carbon content in product phase. This reveals the fact that increasing urea in mix fuel approach increases the extent of exothermicity in solution combustion.
XRD patterns of the combustion product were recorded using a Siemens D500 with Cukα radiations. The XRD of the as-synthesized powder showing that in case of sample 1E (Fig. 2), containing 20 % of urea and 20 % of glycine complete amorphous product is formed. Similar result is obtained for the sample 2E (Fig. 3). Formation of amorphous phase is due to the lack of sufficient temperature required to promote alumina crystallisation. In case of sample 3E (Fig. 4), there is some fraction of crystallinity, which is due to increase in percentage of urea, which in turn increases the exothermicity and hence combustion temperature. In case of sample 4E (Fig. 5), the extent of crystallinity increases because of higher percentage of urea (60 %) in precursor. In case of sample 5E (Fig. 6), some crystallinity is observed, but amorphous character dominates, which is due to higher content of glycine, which results in amorphous product phase. In case of 6E (Fig. 7), crystallinity again increased due to higher percentage of urea than glycine and also due to fuel rich conditions. All above observations reveal the fact that in mixed fuel, urea promotes crystallinity and glycine promotes amorphous character of the product phase.
Alumina powder (Al2O3) is prepared by using solution combustion technique, with mixed fuel (urea and glycine). From all the characterisations, we conclude that nanophase alumina powder is obtained in all fuel proportions, but in case of urea rich fuel, the extent of exothermicity is higher than in case when equal percentage of urea and glycine is used. Urea promotes crystalline character of the product, whereas glycine promotes amorphous character of the product. Also in mixed fuel approach, crystallinity can be enhanced easily by calcinations of powder product at low temperature because, due to mixed urea and glycine, there is already some fraction of crystallinity observssed. In mixed fuel, there is wide range of particle size in nanoscale, because urea promotes high flame and hence agglomeration of particles, whereas glycine promotes the formation of small range of particles size. Hence, in mixed fuel approach, the nanophase alumina powder was obtained with wide range of particles size. From overall discussion, we conclude that mixed fuel approach has an outstanding potential for producing crystalline alumina powder particularly in urea rich case, which highlights the potential of urea to promote crystallinity.
First of all thanks to god, then to my parents who made me able to contribute my potential in research area. The author likes to convey sincere thanks to all staff in Material Science & Engineering section of AMPRI, Bhopal for their help and co-operation in completing this research work. A special thanks to my wife Mrs. Manu Sharma (Lecturer in Botany) for her motivation and inspiration to complete this work.
Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
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With mounting concerns over climate change, the utilisation or conversion of carbon dioxide into sustainable, synthetic hydrocarbons fuels, most notably for transportation purposes, continues to attract worldwide interest. This is particularly true in the search for sustainable or renewable aviation fuels. These offer considerable potential since, instead of consuming fossil crude oil, the fuels are produced from carbon dioxide using sustainable renewable hydrogen and energy. We report here a synthetic protocol to the fixation of carbon dioxide by converting it directly into aviation jet fuel using novel, inexpensive iron-based catalysts. We prepare the Fe-Mn-K catalyst by the so-called Organic Combustion Method, and the catalyst shows a carbon dioxide conversion through hydrogenation to hydrocarbons in the aviation jet fuel range of 38.2%, with a yield of 17.2%, and a selectivity of 47.8%, and with an attendant low carbon monoxide (5.6%) and methane selectivity (10.4%). The conversion reaction also produces light olefins ethylene, propylene, and butenes, totalling a yield of 8.7%, which are important raw materials for the petrochemical industry and are presently also only obtained from fossil crude oil. As this carbon dioxide is extracted from air, and re-emitted from jet fuels when combusted in flight, the overall effect is a carbon-neutral fuel. This contrasts with jet fuels produced from hydrocarbon fossil sources where the combustion process unlocks the fossil carbon and places it into the atmosphere, in longevity, as aerial carbon - carbon dioxide.
There are two ways to convert CO2 to liquid hydrocarbons; an indirect route, which converts CO2 to CO or methanol and subsequently into liquid hydrocarbons, or the direct CO2 hydrogenation route, which is usually described as a combination of the reduction of CO2 to CO via the reverse water gas shift (RWGS) reaction and the subsequent hydrogenation of CO to long-chain hydrocarbons via Fischer-Tropsch synthesis (FTS)45. Jet fuel can then be obtained from the products after industrially recognized treatments such as distillation or hydro-isomerization. The second, direct route is generally recognized as being more economical and environmentally acceptable as it involves fewer chemical process steps, and the overall energy consumption for the entire process is lower46.
The direct conversion of CO2 into fuels through these various reactions has attracted great attention in recent years, and a compilation of some of these investigations is highlighted in Table 1. However, there are few reports of the direct catalytic conversion of CO2 to jet fuel range hydrocarbons20,47. The key to advancing this process is to search for a highly efficient inexpensive catalyst, that can preferentially synthesise the target hydrocarbon range of interest48. Iron-based catalysts, widely used in both the RWGS and FTS reactions, are typically prepared by chemical co-precipitation routes, which unfortunately consumes significant amounts of water49,50,51,52.
The formation of Fe2O3 in the used catalyst probably arises from the oxidation of Fe3O4 by CO2 and/or water during the reaction, while the Fe2O3 was reduced to Fe3O4 in the presence of H2 (showed in Supplementary Fig. 24).
Scanning electron microscopy (SEM) images of both the catalyst precursor and the used catalysts are shown in Fig. 3. The precursor consists of closely packed, regular particles (Fig. 3a). Obvious changes take place in the morphology of the catalyst after reaction (Fig. 3b). STEM-BF images of the catalyst precursor and used catalyst were also recorded as shown in Fig. 4.
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