HİDROJEL ESASLI CoF2 KATALİZÖR ile NABH4’den HİDROJEN SALINIMI

Bu makalede, NaBH4'ün dehidrojenasyon reaksiyonu, Co iyon yüklü hidrojel katalizör varlığında gerçekleştirilmiştir. Reaksiyonlar sırasıyla 25, 35 ve 45 °C'de 27, 18 ve 9 saat içinde gerçekleşmiştir. Bununla beraber, NaBH4'ün başlangıç konsantrasyonu ile salınan hidrojen arasındaki ilişki 45 °C' de araştırılmıştır. Başlangıç borohidrür konsantrasyonu ile üretilen H2 arasında doğrusal bir ilişki olduğu belirlenmiştir. Ayrıca, reaksiyon hız sabitleri ve reaksiyon mertebesini belirlemek için diferansiyel yöntem kullanılmıştır. Böylece, deneysel veriler kullanılarak birinci derece kinetik kanıtlanmıştır. Daha sonra, dehidrojenasyon reaksiyonu için lnk’ya karşılık 1/T grafiğinin eğiminden aktivasyon enerjisi 58.26 kJ/mol olarak bulunmuştur. Bu değer, katalitik dehidrojenasyon çalışmaları için literatürde beklenen 50 kJ/mol'e neredeyse eşittir. Hazırlanan poli (akrilamid-ko-akrilik asit) (p (AAm-co-AAc)-Co) hidrojel katalizörün hidrofilik ve makro-gözenekli yapısı NaBH4 çözeltisinin katalizörün iç kısımlarına kadar girebilmesine ve üretilen H2'nin salınmasına olanak verdiği için gözenek difüzyon sınırlaması etkisi ihmal edilmiştir. NaBH4'ün dehidrojenasyon indeksi, sulu çözeltideki NaBH4 miktarına göre 2526,31 mL H2/g NaBH4 olarak hesaplanmıştır

Anahtar Kelimeler:

Sodyum borhidrür, dehidrojenasyon, hidrojel katalizör, aktivasyon enerjisi

RELEASING HYDROGEN FROM NABH4 VIA HYDROGEL BASED CoF2 CATALYST

In this paper, the dehydrogenation reaction of NaBH4 was performed in the presence of Co-ion loaded hydrogel catalyst. The reactions took place within 27, 18 and 9 hours at 25, 35 and 45 °C, respectively. In addition, the relation between the initial concentration of NaBH4 and released hydrogen was investigated at 45°C. A linear relationship between initial borohydride concentration and produced H2 was determined. Also, differential method was used to determine reaction rate constants and rate order. Hence, first-order-kinetics was proved by using experimental data. After that, the activation energy was found as 58.26 kJ/mol by means of the slope of the graph of lnk versus 1/T for the dehydrogenation reaction. This value is nearly equal to 50kJ/mol, which was expected in literature for the studies of the catalytic dehydrogenation. As the hydrophilic and macroporous structure of the prepared poly(acrylamide-co-acrylic acid) (p(AAm-co-AAc)-Co) hydrogel catalyst allowed inlet of NaBH4 solution up to its interior and release of produced H2, effect of pore diffusion limitation was neglected. Dehydrogenation index of NaBH4 was calculated as 2526.31 mL H2/g NaBH4 according to the amount of NaBH4 in the aqueous solution

Keywords:

Sodium borohydride, dehydrogenation, hydrogel catalyst, activation energy,

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