Browsing by Author "Sanna, Aimaro"

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Catalytic Pyrolysis of Tetraselmis and Isochrysis Microalgae by Nickel Ceria Based Catalysts for Hydrocarbon Production
(Pergamon-elsevier Science Ltd, 2016) Aysu, Tevfik; Abd Rahman, Nur Adilah; Sanna, Aimaro
The catalytic pyrolysis of Tetraselmis sp. and Isochrysis sp. was carried out over ceria based catalysts in a fixed bed reactor. There was a clear effect of the catalysts on the product yields and quality, with the catalysts able to recover a large fraction of the starting microalgae energy (67-77%) in the bio-oils. Biooil yield was found to be higher in presence of Ni-Ce/Al2O3 and Ni-C/ZrO2 (26 wt.%). The produced bio-oils had HHVs (higher heating values) of 34-35 MJ/kg and suffered strong deoxygenation, with O level decreased from 40-41% in the starting microalgae to 9-15%. Also, 15-20% N removal was obtained using the ceria based catalysts. The oxygen contents in the bio-oils were remarkably lower than those previously obtained using ZSM-5 (25%) and other species without catalyst (17-24%). H-1 NMR and GC-MS analysis showed that the bio-oils were enriched in aliphatics and depleted in N-compounds and water using the ceria based catalysts. (C) 2016 Elsevier Ltd. All rights reserved.
Ceria on Alumina Support for Catalytic Pyrolysis of Pavlova Sp Microalgae To High-Quality Bio-Oils
(Elsevier Science Bv, 2018) Aysu, Tevfik; Fermoso, Javier; Sanna, Aimaro
In this work, we report for the first time the in-situ catalytic pyrolysis of Pavlova sp. microalgae, which has been performed in a fixed-bed reactor in presence of Ce/Al2O3-based catalysts. The effects of pyrolysis parameters, such as temperature and catalyst were studied on the products yield distribution and bio-oil composition, among others. Results showed that all catalysts increased the bio-oil yield with respect to the non-catalytic runs and reduced the O/C ratio from 0.69 (Pavlova sp.) to 0.1-0.15, which is close to that of crude oil. In terms of bio-oil oxygen content, MgCe/Al2O3 presented the best performance with a reduction of more than 30%, from 14.1 to 9.8 wt%, of the oxygen concentration in comparison with thermal pyrolysis. However, NiCe/Al2O3 gave rise to the highest aliphatics/aromatics fractions. The elemental and gas analysis indicates that N was partially removed from the catalytic bio-oils in the gas phase in forms of NH3 and HCN. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
Ceria Promoted Deoxygenation and Denitrogenation of Thalassiosira Weissflogii and Its Model Compounds by Catalytic In-Situ Pyrolysis
(Elsevier Sci Ltd, 2016) Aysu, Tevfik; Maroto-Valer, M. Mercedes; Sanna, Aimaro
Pyrolysis of microcrystalline cellulose, egg white powder, palm-jojoba oils mixtures Thalassiosira weissflogii model compounds was performed with CeO2 at 500 degrees C, to evaluate its catalytic upgrading mechanism. Light organics, aromatics and aliphatics were originated from carbohydrates, proteins and lipids, respectively. Dehydration and decarboxylation were the main reactions involved in the algae and model compounds deoxygenation, while nitrogen was removed as NH3 and HCN. CeO2 increased decarbonylation reactions compared to in absence of catalyst, with production of ketones. The results showed that the catalysts had a significant effect on the pyrolysis products composition of T. weissflogii. CeO2, NiCeAl2O3 and MgCe/Al2O3 catalysts increased the aliphatics and decreased the oxygen content in bio-oils to 6-7 wt% of the algae starting O-2 content. Ceria catalysts were also able to consistently reduce the N-content in the bio-oil to 20-38% of that in the parent material, with NiCe/Al2O3 being the most effective. (C) 2016 Elsevier Ltd. All rights reserved.
Effects of Titania Based Catalysts on In-Situ Pyrolysis of Pavlova Microalgae
(Elsevier Science Bv, 2017) Aysu, Tevfik; Ola, Oluwafunmilola; Maroto-Valer, M. Mercedes; Sanna, Aimaro
Pavlova microalga was pyrolysed in presence of titania based catalysts in a fixed bed reactor at various temperatures. The effects of catalysts on Pavlova microalga pyrolysis were investigated. A large fraction of the starting energy (similar to 63-74% daf) was recovered in the bio-oils when the catalysts were used. The bio-oil yield was 20% higher in presence of Ni/TiO2 (22.55 wt%) at 500 degrees C. The High Heating Values of the produced bio-oils were in the range of similar to 35-37 Mykg and suffered strong deoxygenation, with O content (% daf) diminished from 51 wt% to similar to 9-12 wt%. The H-1 Nuclear Magnetic Resounance and Gas Chromatography Mass Spectrometry suggested that the titania catalysts enlarged the aliphatics and aromatic compounds and decreased oxygenates in the bio-oils. Ni/TiO2 had the greatest activity in increasing aliphatic protons (60%) and decreasing coke formation. Its enhanced cracking activity was due to its higher availability on the catalyst surface, compared to Co and Ce, and to strong interaction between Ni and TiO2 support. Despite the fact that the bio-oils were partially de-nitrogenated, the N-content still represent a major limitation for their use as bio-fuels without further upgrading. (C) 2017 Published by Elsevier B.V.
Nannochloropsis Algae Pyrolysis With Ceria-Based Catalysts for Production of High-Quality Bio-Oils
(Elsevier Sci Ltd, 2015) Aysu, Tevfik; Sanna, Aimaro
Pyrolysis of Nannochloropsis was carried out in a fixed-bed reactor with newly prepared ceria based catalysts. The effects of pyrolysis parameters such as temperature and catalysts on product yields were investigated. The amount of bio-char, bio-oil and gas products, as well as the compositions of the resulting bio-oils was determined. The results showed that both temperature and catalyst had significant effects on conversion of Nannochloropsis into solid, liquid and gas products. The highest bio-oil yield (23.28 wt%) and deoxygenation effect was obtained in the presence of Ni-Ce/Al2O3 as catalyst at 500 degrees C. Ni-Ce/Al2O3 was able to retain 59% of the alga starting energy in the bio-oil, compared to only 41% in absence of catalyst. Lower content of acids and oxygen in the bio-oil, higher aliphatics (62%), combined with HHV show promise for production of high-quality bio-oil from Nannochloropsis via Ni-Ce/Al2O3 catalytic pyrolysis. (C) 2015 Elsevier Ltd. All rights reserved.