(641e) The Use of Sand As Sustainable Catalyst in H2 Production from NaBH4 Methanolysis

Hydrogen (H₂) use as an alternative green energy carrier to fossil fuels is steadily growing in recent years because of the increased concerns in the environmental issues and climate changes. As H₂ is environmentally friendly, carbon free, and efficient energy carrier with no by product emission except water vapor upon its combustion with oxygen, it is considered as clean and renewable futuristic fuel. In addition to vast amount of water as H₂ source, metal hydrides are primary chemical storage reagents that are extensively used as H₂ carriers. Sodium borohydride (NaBH₄) amongst the chemical hydrides are particularly attractive because of non-volatile, chemically stable and environmentally friendly, and high H₂ content that is commonly used as H₂ carrier. To release H₂ from NaBH₄ in the presence of a catalyst, different solvents such as ethanol, methanol, glycerol, ethylene glycol are frequently used. Among these solvents, methanol offers many advantages such as faster H₂ production rates than e.g., H₂O and CH₃CH₂OH solvents in addition to its’ capability of performing H₂ release from NaBH₄ at subzero temperatures (T>0 ^oC). In the release studies of H₂ from NaBH₄, metal nanoparticles and their composites such as Co, Ni, Fe, Ru, Pt and Pd so on are widely used catalysts. Interestingly, in the recent years, ionic liquid (IL) and polymeric ILs that were also reported as sustainable metal-free catalysts for H₂ release studies from NaBH₄.

In this study, sand obtained from various public beaches were used as catalyst to generate H₂ from the methanolysis of NaBH₄ reaction. Upon sieving the sand sample in different sizes e.g., over few hundred of micrometers, the samples were washed with ethanol: DI water mixture (50:50) and then treated with various acids such as hydrochloric acid, sulfuric acid, nitric acid, and so on. Then, these acid treated sands were used as catalysts for H₂ production from the methanolysis of NaBH₄. Various parameters such as the types of acids, reaction temperature, re-usability, and re-generation capabilities of these natural catalysts on methanolysis of NaBH₄ reaction were investigated.

Moreover, the sand samples were also chemically modified with various types of amine containing modification agents that contain different numbers of amines, N=2-6 and polyethyleneimine (PEI). The effect of number of amine groups of the modifying agents for H₂ production from NaBH₄ methanolysis were compared. It was found that the protonation of amine groups on the sand catalyst resulted in higher catalytic performances for all the amino modified catalyst systems. Additionally, various parameter such as the types the catalyst dose, and the amounts of NaBH₄,and the reaction temperature on the methanolysis of NaBH₄ reaction as well as re-usability and re-generation abilities of the catalysts were investigated.