Catalytic Performance And Reaction Properties Of Alcoholysis Of Sodium Borohydride

Hydrogen generation from the alcoholysis of sodium borohydride,with high density of hydrogen storage,fast startup of the reaction and wide temperature range,has a broad application in mobile devices such as the fuel cell and military special power supply.SO₄^2-/M_xO_y and Cu/SAPO-34 catalysts are prepared by different methods,respectively.The effects of preparation conditions on catalytic performance based on the alcoholysis reaction are investigated,and various factors on the reaction are also examined.The reaction mechanism of metal-catalyzed alcoholysis and catalyst activity reduction are also discussed.The catalytic performance of SO₄^2-/M_xO_y?M=Cu,Co,Fe,Ni,Cr,Zr and Mg?that prepared by chemical precipitation are tested.SO₄^2-/CuO,SO₄^2-/CoO and SO₄^2-/Fe₂O₃catalysts reveal excellent catalytic activity,and SO₄^2-/CuO shows the best.Characterization analysis of XRD,FT-IR and SEM reveal the composition of SO₄^2-/M_xO_y catalysts,which in essence for the oxides and sulfides of the corresponding metal.The optimal preparation conditions of the SO₄^2-/CuO sample are determined with the aging time of 24 h,impregnation ratio of 30:1 and 3 h of calcination under550 ^oC.Kinetic analysis reveals the reaction orders of methanolysis with respect to concentration of sodium borohydride,methanol and catalyst are 1.01,1.60 and 0.52,respectively.Analogously,the reaction order of ethanolysis with respect to the concentration of sodium borohydride is 0.91.The first order dynamics model could effectively describe the reaction behavior of the sodium borohydride alcoholysis within the scope of experimental conditions in this paper?reaction temperature range:methanolysis 0³0 ^o C,ethanolysis 30⁷0 ^oC?.The decline of reaction rate in the stability test is due to the change of physicochemical properties of catalyst,and the decrease of catalytic activity might be attribute to the reduction of both acidic and metallic sites,the reorganization of the catalyst structure and the generated boron species covering the surface of the SO₄^2-/CuO catalyst.The optimal preparation conditions of Cu/SAPO-34 are determined,with the best solvent pH value of 8 and calcination temperature at 550 ^oC.the reaction order of the catalytic ethanolysis with respect to the concentration of sodium borohydride is 0.9958.Dynamics analysis reveals the ethanolysis of sodium borohydride conforms to the pseudo-first-order model,which has nothing to do with the type,quantity and use of the catalyst.The reaction mechanism of metal-catalyzed ethanolysis is discussed that based on the research above,The dissociative chemisorption of[BH₄]^-on the catalyst surface in the solvent as the first kinetic step,and the essence of reaction process is series of stepwise replacement that B-H bond replaced by B-?OCH₂CH₃?bond.