Autothermal reforming of petroleum fractions

Download
2019
Arslan Bozdağ, Arzu
On site and on-demand hydrogen production through diesel autothermal (ATR) and steam reforming (DSR) reactions are attractive routes for both stationary and mobile auxiliary power unit applications (APUs). Maximization of H2 production with coke minimization for cheap and active Ni/Al2O3 catalysts was investigated with incorporation of different metals/metal oxides to Ni/Al2O3 catalyst in DSR and ATR reactions. Two different synthesis techniques which are impregnation of metal/metal oxides to commercial Al2O3 pellets and one-pot synthesis of metal/metal oxide incorporated Al2O3 through surfactant aided evaporation induced self-assembly (EISA) approach, were applied. The effects of different metals/metal oxides such as Ru, W, CeO2, Mg, ZrO2 and their different combinations such as Ru & CeO2, Mg, CeO2 & ZrO2, W & CeO2, W & Mg on the hydrogen productivity and coke resistivity of Ni/Al2O3 catalyst in DSR and ATR reactions were investigated. Performances of catalysts were investigated at the optimum operating conditions which were found to be 7500 h-1 for GHSV, and 2.5 for H2O/C ratio in DSR reaction, 7500 h-1 for GHSV, 2.5 for H2O/C ratio, and 0.5 for O2/C ratio in ATR reaction. Catalyst investigations presented that among Ru and Ru-CeO2 incorporated catalysts, 0.5 wt.% ruthenium loading results in the highest H2 production in both DSR and ATR. Higher activity of this material was mostly due to its higher surface area and easier reducibility of Ni on Ni@0.5Ru@Al2O3 which also presented long term stability for 34 h. Superior activity in DSR was obtained with CeO2 or CeO2/ZrO2 incorporated (one-pot) Ni/Al2O3-EISA catalysts. However, instabilities in product composition of CeO2/ZrO2 incorporated catalyst observed in DSR suggested that in the long term, incorporation of CeO2 is more preferable. CeO2 incorporated catalyst also presented higher hydrogen production in ATR reaction compared to CeO2/ZrO2 incorporated catalyst. Long term DSR test performed with Ni@10CeO2-Al2O3-EISA lead to superior activity along with stability. Tests on Mg, W, W-CeO2 and W-Mg incorporated (one-pot) mesoporous Al2O3-EISA supported nickel catalysts showed the most successful catalyst as Ni@10Mg-Al2O3-EISA in terms of hydrogen yield in DSR reaction. The stability and superior activity of Ni@10Mg-Al2O3-EISA catalyst was observed in long term DSR activity test. Higher success of this catalysts was due to formation of Ni0 crystals whereas formation Ni4W crystals was observed along with lower surface area and higher acidity in W catalysts, leading to lower water gas shift and reforming reaction rates. However, significant coke minimization was achieved with W catalysts due to low solubility of carbon in Ni4W crystals and also due to WC crystal formation during reforming reactions. The best performing catalysts in this study in terms of hydrogen production was Ni@10Mg-Al2O3-EISA, Ni@0.5Ru@Al2O3 and Ni@10CeO2-Al2O3-EISA. Considering sustainability of the developed catalysts, it is suggested that Ni@10Mg-Al2O3-EISA catalyst can be used in commercial applications of DSR. The highest hydrogen production with low coke deposition in ATR reaction was obtained with Ni@10CeO2-Al2O3-EISA catalyst, which can be used in an APUs equipped with a reformer unit to produce hydrogen for solid oxide fuel cells.

Suggestions

Development of ceria and tungsten promoted nickel/alumina catalysts for steam reforming of diesel
Bozdag, A. Arslan; Kaynar, A. D. Deniz; Doğu, Timur; Sezgi, Naime Aslı (Elsevier BV, 2019-12-01)
Use of diesel fuel for on-board hydrogen production for auxiliary power units (APUs) through diesel steam reforming (DSR) reaction is a promising route. Coke minimization for cheap and active Ni/Al2O3 catalyst is necessary for long term operation in DSR reaction. Coke minimization with high hydrogen productivity can be accomplished through the optimization of operating conditions and promoting the Ni/Al2O3 catalyst with ceria (CeO2) and tungsten (W) which attracts attention with their coke resistive propert...
Direct synthesis of hydrogen storage alloys from their oxides
Tan, Serdar; Öztürk, Tayfur; Aydınol, Mehmet Kadri; Department of Metallurgical and Materials Engineering (2011)
The aim of this study is the synthesis of hydrogen storage compounds by electrodeoxidation technique which offers an inexpensive and rapid route to synthesize compounds from oxide mixtures. Within the scope of this study, two hydrogen storage compounds, FeTi and Mg2Ni, are aimed to be produced by this technique. In the first part, effect of sintering conditions on synthesis of FeTi was studied. For this purpose, oxide pellets made out of Fe2O3-TiO2 powders were sintered at temperatures between 900 °C – 1300...
Deposition and testing of thin film hydrogen separation membranes
Pişkin, Fatih; Öztürk, Tayfur; Department of Metallurgical and Materials Engineering (2013)
Industrial production of hydrogen from the syngas, generated from steam reformation of natural gas or coal gasification, sets conditions for hydrogen separation membranes in terms of operating conditions. An alternative source for hydrogen is a syngas generated by gasification of municipal solid wastes which are likely to set more stringent conditions for the separation membranes. There is therefore, a growing demand for separation membranes with improved permeability and particularly of low cost. Among var...
Phototrophic hydrogen production by agar-immobilized Rhodobacter capsulatus
Elkahlout, Kamal E. M.; Yücel, Ayşe Meral; Eroğlu, İnci; Department of Biotechnology (2011)
photosynthetic bacteria is attractive field as production is fueled by solar energy. Hydrogen production potential of two photosynthetic bacteria R.capsulatus (DSM1710 wild type and R.capsulatus YO3 Hup- uptake hydrogenase deleted mutant strain) were examined in agar immobilized systems. In the present work agar and glutamate concentrations were optimized for immobilization of bacteria while feeding bacteria with 40/2-4 mM acetate/ glutamate. Immobilized bacteria produced hydrogen for 420-1428 hours coverin...
Hydrogen storage in magnesium based thin films
Akyıldız, Hasan; Öztürk, Tayfur; Özenbaş, Ahmet Macit; Department of Metallurgical and Materials Engineering (2010)
A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed; one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a t...
Citation Formats
A. Arslan Bozdağ, “Autothermal reforming of petroleum fractions,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Chemical Engineering., Middle East Technical University, 2019.