Susuz Borakstan Sodyum Borhidrür Sentezi: Stokiyometri ve Alternatif İndirgeyici Malzemelerin Etkisi

Öz

Susuz borakstan, alüminyum ve sodyum hidroksit kullanılarak sodyum borhidrür üretimi, hidrojen atmosferinde çalışan bomba tipi kesikli bir reaktörde incelenmiştir. Çalışmada, stokiyometrik oranların ve kalsiyum karbür ilavesinin verim ve ürün kompozisyonu üzerindeki etkileri değerlendirilmiştir. Kalsiyum karbür kullanılmayan deneylerde, molce %100 fazla alüminyum ve sodyum hidroksit kullanımı reaksiyon verimini %11.31’ den %13.28’ e çıkarmıştır. Ancak, kalsiyum karbür ilavesi reaksiyon mekanizmasını değiştirerek, kompleks faz yapılarının oluşumuna yol açmıştır. FT-IR ve XRD ile yapılan yapısal karakterizasyon, 1 ve 2 numaralı deneylerde elde edilen ürünlerin referans NaBH₄ ile uyumlu olduğunu doğrulamıştır. Buna karşın, 3, 4 ve 5 numaralı deneylerin ürünleri, NaBH₄'e özgü piklerin gözlemlenmediği önemli farklılıklar göstermiştir. Bu bulgular, reaksiyon verimliliğinin artırılmasında stokiyometrik optimizasyonun ve tanecik boyutunun küçültülmesinin (<150 μm) önemini vurgulamaktadır. Gelecek çalışmalar, proses parametrelerinin iyileştirilmesine ve alternatif indirgeme ajanlarının rolünün anlaşılmasına odaklanmalıdır.

Anahtar Kelimeler

• Sodyum borhidrür
• susuz boraks
• kalsiyum karbür

Investigation of Sodium Borohydride Synthesis from Anhydrous Borax: Impact of Stoichiometry and Alternative Reducing Agents

Öz

The production of sodium borohydride from anhydrous borax using aluminum and sodium hydroxide as reactants was investigated in a bomb-type batch reactor under hydrogen atmosphere. The study evaluated the effects of stoichiometric ratios and the addition of calcium carbide on yield and product composition. Experiments without calcium carbide, employing 100% molar excess of aluminum and sodium hydroxide, increased the yield from 11.31% to 13.28%. However, incorporating calcium carbide redirected the reaction mechanism, leading to the formation of complex phase structures. Structural characterization using FT-IR and XRD confirmed the consistency of products from Experiments 1 and 2 with reference NaBH₄. In contrast, products from Experiments 3, 4 and 5 showed significant deviations, with no NaBH₄-specific peaks observed. These findings underscore the importance of stoichiometric optimization and particle size reduction (<150 μm) for improving reaction efficiency. Future studies should focus on refining process parameters and understanding the role of alternative reducing agent.

Anahtar Kelimeler

• Sodium borohydride
• anhydrous borax
• calcium carbide

Kaynakça

1. Alibeyli, R., Arslan, S., & Özdemir, E. (2011). Single stage production and hydrolysis of sodium borohydride. International Journal of Hydrogen Energy, 36(17), 11451–11456. https://doi.org/10.1016/j.ijhydene.2010.12.111
2. Alibeyli, R., Guliyev, S., & Ahmedov, İ. (2008). Borakstan tek aşamalı sodyum bor hidrür üretimi süreci. Türk Patent ve Marka Kurumu, 2008/00589.
3. Amendola, S. C., Sharp-Goldman, S. L., Janjua, M., Kelly, M. T., Petillo, P. J., & Binder, M. (2000). An ultrasafe hydrogen generator: Aqueous, alkaline borohydride solutions and Ru catalyst. Journal of Power Sources, 85(2), 186–189. https://doi.org/10.1016/S0378-7753(99)00301-8
4. Brack, P., Dann, S. E., & Wijayantha, K. G. (2015). Heterogeneous and homogeneous catalysts for hydrogen generation from sodium borohydride. Energy Science & Engineering, 3(3), 174–188. https://doi.org/10.1002/ese3.67
5. Çakanyıldırım, Ç., & Gürü, M. (2011). The production of NaBH₄ from its elements by mechano-chemical reaction and usage in hydrogen recycle. Energy Sources, Part A: Recovery, 33(20), 1912–1920. https://doi.org/10.1080/15567030903503175
6. Demirci, U. B., & Miele, P. (2009). Sodium tetrahydroborate as energy/hydrogen carrier: Its history and future. Comptes Rendus Chimie, 12(9), 943–950. https://doi.org/10.1016/j.crci.2008.08.002
7. Eom, K., Cho, E., Kim, M., Oh, S., Nam, S. W., & Kwon, H. (2013). Thermochemical production of sodium borohydride from sodium metaborate in a scaled-up reactor. International Journal of Hydrogen Energy, 38(7), 2804–2809. https://doi.org/10.1016/j.ijhydene.2012.12.053
8. Figen, A. K., & Piskin, S. (2013). Microwave-assisted green chemistry approach of sodium metaborate dihydrate (NaBO₂·2H₂O) synthesis and use as raw material for sodium borohydride (NaBH₄) thermochemical production. International Journal of Hydrogen Energy, 38(8), 3702–3709. https://doi.org/10.1016/j.ijhydene.2013.01.003

9. Gençaslan, A., & Karaduman, A. (2016). Titreşim karıştırmalı bilyeli değirmende sodyum borhidrür üretiminde borat kaynağı olarak susuz boraks ve sodyum metaboratın karşılaştırılması. Journal of Boron, 1(2), 96–103.
10. Kojima, Y., Suzuki, K.-I., & Fukumoto, K. (2002). Hydrogen generation using sodium borohydride solution and metal catalyst. International Journal of Hydrogen Energy, 27(10), 1029–1034. https://doi.org/10.1016/S0360-3199(02)00014-9.
11. Kong, L., Cui, X., Jin, H., Wu, J., Du, H., & Xiong, T. (2009). Mechanochemical synthesis of sodium borohydride by recycling sodium metaborate. Energy & Fuels, 23(12), 619–627. https://doi.org/10.1021/ef900619y.
12. Lyttle, D. A., Jensen, E. H., & Struck, W. A. (1952). A simple volumetric assay for sodium borohydride. Analytical Chemistry, 24(11), 843–844.
13. Marrero-Alfonso, E. Y., Gray, J. R., Davis, T. A., & Matthews, M. A. (2007). Minimizing water utilization in hydrolysis of sodium borohydride: Role of sodium metaborate hydrates. International Journal of Hydrogen Energy, 32(19), 4723–4730. https://doi.org/10.1016/j.ijhydene.2007.08.014.
14. Nunes, H. X., Silva, D. L., Rangel, C. M., & Pinto, A. M. F. R. (2021). Rehydrogenation of sodium borates to close the NaBH₄-H₂ cycle: A review. Energies, 14(12), 3567. https://doi.org/10.3390/en14123567.
15. Ou, T., Giuliano, A., Panizza, M., Barbucci, A., & Cerisola, G. (2013). Thermochemical recycling of hydrolyzed NaBH₄. Part I: In-situ and ex-situ evaluations. International Journal of Hydrogen Energy, 38(35), 15269–15274. https://doi.org/10.1016/j.ijhydene.2013.09.058.
16. Santos, D. M. F., & Sequeira, C. A. C. (2011). Sodium borohydride as a fuel for the future. Renewable and Sustainable Energy Reviews, 15(8), 3980–4001. https://doi.org/10.1016/j.rser.2011.07.018.
17. Schlesinger, H. I., Brown, H. C., & Finholt, A. E. (1953). The preparation of sodium borohydride by the high-temperature reaction of sodium hydride with borate esters. Journal of the American Chemical Society, 75(1), 205–209. https://doi.org/10.1021/ja01097a054.