Details

Autor(en) / Beteiligte

• Ar, İrfan
• Güler, Özge Usta
• Gürü, Metin

Titel

Synthesis and characterization of sodium borohydride and a novel catalyst for its dehydrogenation

Ist Teil von

• International journal of hydrogen energy, 2018-11, Vol.43 (44), p.20214-20233

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2018

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Because of the growing world population and development of technology, the growing population's desire to achieve better life standarts is rising day by day. Correspondingly, there is more consumption and the amount of energy to meet the needs of production is increasing. Increasing energy demand causes the exhaustion of fossil fuels and also enforces to investigate for new and renewable energy sources' development. Although hydrogen energy is a clean energy there are some problems such as: storage, transportation and safely usage problems. Sodium borohydride is synthesized to overcome these problems. At the same time, controlled hydrogen release during dehydrogenation and its safe usage is become more important. Studies have been continued under the different reaction conditions to reach the best hydrogen yield in optimum conditions using various catalysts in this subject. In this study sodium borohydride which can store high amount of hydrogen is synthesized from sodium amide, magnesium hydride and boron oxide by mechanochemical reaction in spex type miller. Up to the authors knowledge there is no study reported in the literature that uses sodium amide as the sodium source. Ethylene diamine was used to purify the raw product. FT-IR, XRD, TGA/DTA, particle size analysis and iodimetric analysis are performed to characterize the synthesized product. As a result of experimental studies, the highest efficiency is obtained by using 30% excess MgH2 in the spex type miller with a 500 min mechanochemical reaction time. Purification of product by using ethylene diamine results the removal of excess MgH2 and side product MgO to give pure NaBH4 and consequently provides 84% yield. Hydrogen is produced from the catalytic dehydrogenation of sodium borohydride to get energy. Also a novel catalyst is synthesized for the dehydrogenation of sodium borohydride in this study. Catalyst used in dehydrogenation reaction were synthesized in economical ways. Kinetic properties of dehydrogenation reactions are developed from the datum of experiments. SEM + EDS and BET analysis are carried out to investigate the surface properties and elemental compositions of catalysts. Various reaction orders were investigated and it as found that the experimental results confirm very well with the zeroth order reaction kinetics at low temperatures (R2 = 0.9921) where as they confirm with the first order reaction kinetics at high temperatures. These observations were also supported by the behavior of lnk vs 1/T line. Change in the slope of lnk vs 1/T line and consequently activation energy of the reaction indicates the change in reaction mechanism. Activation energy (Ea) values for the zeroth order reaction (reaction at low temperature) and first order reaction (at high temperatures) were determined as 32.43 kJ/mol, and 94.93 kJ/mol, respectively. Required integrated system conditions were determined by carrying out the performance measurements in our PEM fuel cell test station. The performance of the synthesized catalyst was determined by performing a set of dehydrogenation-regeneration cycles. Prepared catalyst could achieve hydrogen liberation for 2171 cycle, which equals 212 days uninterruptedly. •Sodium amide is used as sodium source for the synthesis of sodium borohydride.•Excess MgH2 usage in sodium borohydride synthesis has a positive effect.•Ethylene diamine is an effective purification agent; it dissolves only NaBH4.•NaBH4 was obtained with a 84% yield after the removal of ethylene diamine.•30% CoCl2NiCl2 can keep its activity for 2171 cycles and can be used for 212 days.