目前吸附材料众多,如沸石、MOFs、聚合物等,而生物质具有分布广泛、低成本、可再生和净零排放等优点成为研究热点。已有研究表明掺氮有利于提升生物质炭对CO2的吸附性能,金属矿物质可对生物炭改性,增大生物炭表面有效吸附面积。但何种氮基团对于生物质炭表面CO2吸附性能影响显著仍未清晰,金属矿物质与富氮改性协同作用下生物质炭表面CO2的吸附特性尚未明晰。基于此,采用量子化学理论计算研究了不同含氮基团生物质炭表面CO2的吸附机理,系统探究了不同金属氧化物(MgO、CaO)及其耦合掺氮生物炭对CO2吸附的影响机理。结果表明,各含氮基团生物质炭不同吸附方式中,含N-X生物质炭对CO2吸附作用最强。分析CO2在MgO与CaO体系中O-Top、Hollow和Bridge三种不同吸附方式,得出CO2以O-Top方式吸附于CaO体系中的吸附能最大,相同吸附方式下较MgO对CO2的吸附能高92.22kJ/mol。相较MgO,CaO中O对CO2中C的作用更强,电子云重叠区域更大,电荷转移更多,与CO2分子间的作用引力更强。进一步研究发现含N-X生物质炭与CaO耦合对CO2吸附有一定协同促进作用,较单独含N-X生物质炭和CaO而言,二者耦合对CO2的吸附能分别提升了136.81和0.87kJ/mol。本研究为高质含碳化学品的制备提供了理论支撑。

At present,there are many adsorption materials,such as zeolite,MOFs,polymers,etc,while biomass has the advantages of widedistribution,low cost,renewable and net zero emissions,which has become a research hotspot. Previous studies have shown that nitrogendoping is beneficial to improving the CO2 adsorption performance of biocha,and biochar can be modified by metal minerals to increase theeffective adsorption area of biochar surface. However,it is still not clear which nitrogen groups significantly affect the CO2 adsorption performance on the surface of biochar. The adsorption characteristics of CO2 on the surface of biochar under the synergistic effect of metallic minerals and nitrogen-rich modification are not yet clear. Based on this,quantum chemistry theory was used to calculate and study theadsorption mechanism of CO2 on the surface of biochar with different nitrogen-containing groups,and the influence mechanism of different metal oxides (MgO,CaO) and their coupled nitrogen-doped biochar on CO2 adsorption was systematically explored. The results showthat biochar containing N-X has the strongest adsorption effect on CO2 among the different adsorption methods of nitrogen-containing biochar. By analyzing the three different adsorption modes of CO2 in MgO and CaO systems,namely O-Top,Hollow,and Bridge,it is concluded that the adsorption energy of CO2 in O-Top mode on CaO system is the maximum,and the adsorption energy of CO2 in O-Top mode is92.22 kJ/ mol higher than that in MgO under the same adsorption mode. Compared with MgO,O in CaO has a stronger effect on C in CO2,with more overlapping electron clouds,more charge transfer,and stronger gravitational attraction between CaO and CO2 molecules. Furtherstudy show that the coupling of N-X biochar and CaO has a certain synergistic promoting effect on the adsorption of CO2. Compared withN-X biochar and CaO alone,the adsorption energy of CO2 by the coupling of the two increases by 136.81 kJ/ mol and 0.87 kJ/ mol,respectively. This study provides theoretical support for the preparation of high quality carbonaceous chemicals.

0 引言

1 密度泛函理论计算

   1.1 掺氮生物质炭

   1.2 金属氧化物

2 结果与讨论

   2.1 生物质炭各吸附位点

   2.2 生物质炭对CO2的吸附

   2.3 金属氧化物各吸附位点吸附能计算

   2.4 金属氧化物对CO2吸附

3 金属氧化物耦合含氮生物质炭吸附CO2

4 结论