Research On The Synthesis And Performance Of Ni-ZnO Nanoparticles As Highly-efficient Catalyst For Bicarbonate Reduction To Formic Acid

The amount of carbon dioxide sharply increased in the atmosphere and this makes the fixation and recycling of carbon dioxide a popular research topic.It can solve this problem by the reaction of carbon dioxide with hydrogen to form formic acid.Formic acid is a kind of chemical raw material with economic value,and it also can be used as fuel of chemical batteries to solve the shortage of traditional fossil energy.Because of highly Chemical stability of carbon dioxide,amount of energy required for direct resource utilization.However,it is much easier,if carbon dioxide reacted with alkali to form bicarbonate firstly.In this paper,Ni-ZnO nanoparticles are prepared by reverse phase microemulsion with a simple process,and it was supported on SiO₂ to form metal-supported catalysts.The particle size of Ni-ZnO nanoparticles ranges from 1.8 to 3 nm.The process and mechanism of composite material formation are studied.At the same time,the reaction of sodium bicarbonate catalytic reduction to formic acid was explored.By adjusting amount of metal precursors Ni?NO₃?₂ and Zn?NO₃?₂,the loading of metal components and the metal ratio can be controlled in the composite.The size of Ni-ZnO/SiO₂ composite material is 28⁹5 nm,and the size of Ni-ZnO active component is 1.8³ nm.A series of prepared catalysts were used for hydrogenation of carbon dioxide to produce formic acid,and the activity of catalyst was compared.It can be found that when the metal component loading was 5.4%,and the metal ratio n_Ni:n _ZnO=1:1,the catalytic activity was the best.In addition,it were discussed that the effects of various reaction conditions on the yield of formic acid such as T?reaction temperature?and[P]/[C]?the ratio of the amount of hydrogen to sodium bicarbonate?.It was found that when the ratio of[P]/[C]was 60 at 260^oC,the best catalyst was used,and after 2hours of reaction,the yield of formic acid reached 97%.The mechanism of the catalyst was also explored,the catalyst promoted H₂ decomposed into H^?+and H^?-,and then reacted with HCO₃^-to generate HCOO^-.According to the fruit of our laboratory,the stability of catalyst is improved with amino functionalization.In order to further improve the effect of the Ni-ZnO/SiO₂-NH₂ catalyst used in continuous hydrogen atmosphere at atmospheric pressure,the reaction conditions of the catalyst metal loading,T?reaction temperature?and t?reaction time?were explored on the basis of the original experiment.It was found that the yield of formic acid was 30.4%under the conditions of 70^oC and reaction time of 4.5 h.The stability of the catalyst was explored.Ni-ZnO/SiO₂ was recycled in the experiment.It was found that because the size of Ni-ZnO is too small,it is easy to lose,and its stability is poor.After five cycles,the formic acid yield decreased from 29%to 16.5%.After loading Ni-ZnO on amino-functionalized SiO₂,the activity of the catalyst did not change significantly after five cycles of use.The yield of formic acid changed from 30.4%to 30.3%,which shows that the catalyst still has a high activity.In addition,the formation mechanism of amino-functionalized SiO₂ was also explored,mainly due to the co-hydrolysis and co-condensation process of TEOS and APTES.