Preparation Of Syngas And Its Mechanism In Triboelectric Plasma-water System

The massive consumption of fossil energy has caused anthropogenic CO2 emissions to exceed the natural carbon cycle.This major issue has aroused global attention.In recent years,how to use renewable energy to convert CO2 into valuable chemicals has attracted the attention of many researchers.However,in the research field of CO2 conversion,the utilization rate of renewable energy by traditional electrochemistry is very low and the consumption of a large amount of energy is likely to cause secondary pollution.In addition,traditional plasma has extremely high requirements for power supply.The large-scale and complex highvoltage equipment severely limits its practical application in industry.Based on the above problems,triboelectric nanogeneration(TENG)can be used to collect a variety of mechanical energy in the natural environment and convert it into electrical energy,which has the characteristics of high voltage and low current.Utilizing the characteristics of high voltage can ionize gas to generate triboelectric plasma.Consistent with traditional plasma,it can make chemical reactions with harsh conditions and difficult to carry out,and realize the conversion and utilization of CO2 at normal temperature and normal pressure.Synthesis gas is an important raw material in the field of chemical engineering,and its preparation has attracted the attention of many researchers.Different syngas ratios(the ration of H2/CO)have different application values.For example,when H2/CO is 2,it is suitable for methanol synthesis,F-T synthesis and other subsequent industrial processes.Hydroformylation requires H2/CO to be 1.In recent years,in the field of CO2 conversion and utilization,the research on the preparation of important chemical raw material synthesis gas(CO+H2)through plasma-liquid interaction is important research directions in the field of plasma science and technology,and has attracted extensive attention.Plasma-liquid interface reactions will generate a variety of active species,such as solvated electrons,hydrogen radicals,hydroxyl radicals,etc.,which can realize the preparation of syngas or liquid organic fuel.The production of syngas from cheap and abundant sources of CO2 and H2O is a promising route.The use of triboelectric plasma-water reaction system to prepare syngas not only actively responds to the call of "carbon peak" and "carbon neutral",but also realizes the efficient utilization of waste by "turning waste into treasure".Main content of this dissertation:1.TENG-driven triboelectric plasma-water reaction system was constructed to realize the conversion of CO2 and H2O to produce synthesis gas.TENG,as a plasma power source,discharges ionized gas at high pressure to produce high energy particles that break the stable chemical bonds of CO2 and H2O and produce CO and H2.In the triboelectric plasma-water reaction system,the system temperature,solution pH,discharge structure and feed gas composition all affect the synthesis gas ratio.During the experiment,the needle-water surface distance was kept at 0.5 mm,the gas flow rate was 5 sccm,and the rotation speed of TENG was 300 rpm.The composition and content of the product were quantitatively analyzed by gas chromatography.From the experimental results,it can be known that:a.The system temperature has a great influence on the regulation of the syngas ratio.As the system temperature is adjusted from 0℃ to 90℃,the proportion of syngas increases from 0.01 to 0.67;b.Different discharge structures produce different proportions of syngas.The proportion of syngas prepared in the anode plasma discharge structure is the highest,which can reach 0.67;c.In different discharge structures,the effect of solution pH on the proportion of syngas is different.In the cathode plasma discharge structure,there is basically no effect;in the anode and bipolar plasma discharge structures,reducing the pH of the solution is beneficial to the increase of the proportion of syngas;d.The composition of raw material gas will affect the proportion of synthesis gas.In order to avoid the recombination of hydrogen-oxygen,Ar was introduced into CO2,which increased the production of H2,and the proportion of syngas increased from 0.06 to 5.66 with the increase of Ar content.2.The triboelectric plasma emission spectrometry test system was constructed,and the spectral information of the needle-needle discharge of CO2 and CO2+H2O co-reduction reactions under different experimental conditions was tested.The experimental results show that the intensity of the emission spectrum increases with the increase of TENG rotation speed.By comparing the two reaction systems,it is found that when H2O participates in the reaction,Ha will be produced.The composition of feed gas will affect the atomic emission spectrum of the CO2+H2O co-reduction system.With the decrease of CO2 content,the emission spectrum intensity of CO decreases and the spectral intensity of Ha increases.Next,through the comparison and calculation of the emission spectrum information of CO2 and CO2+H2O co-reduction system,the reaction pathway of CO2 and H2O conversion to synthesis gas was analyzed.The analysis results show that the pure CO2 reaction system only has the emission spectrum information of CO,C,O,etc.,while the CO2+H2O co-reduction system also has Ha information.And with the change of CO2 and Ar content in raw gas,the spectral intensity of Hα,CO and O will change.It can be seen that during the cracking reaction process of CO2 and H2O,namely 1.CO2+e-=CO+O+e-,CO2 cracks to produce CO;2.H2O+e-=H+OH+e-,H2O will produce free hydrogen through the cracking of high-energy particles radicals,followed by combination of hydrogen radicals to produce hydrogen gas.In this dissertation,using TENG as the plasma power source,a triboelectric plasma-water reaction system was built,and combined with the conversion of CO2 and H2O,the system not only realized the production of syngas,but also realized the cycle of carbon use.