不同组分过渡金属氧化物催化剂对介质阻挡放电固氮的影响机制

Influence Mechanism of Filling Transition Metal Oxide Catalyst with Different Components on Nitrogen Fixation in Dielectric Barrier Discharge

为了促进介质阻挡放电(DBD)协同催化固氮效果,制备了不同组分Mn/Co/W元素的单一型、二元和三元复合型负载催化剂,并将催化剂置入DBD气隙中进行等离子体协同催化固氮反应.通过X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线能谱(EDS)表征了催化剂的性质,并采用紫外分光光度法测定了液相中的总氮浓度.结果表明,填充催化剂实验组比未填充催化剂组的总氮浓度明显提升.采用傅里叶变换红外光谱仪对有/无催化剂填充两种情况下DBD的气相产物进行了检测,结果表明,填充催化剂能促进空间内NO_(2)和N_(2)O_(5)的生成.通过DBD气相链式反应和催化原理揭示了总氮浓度得以提升的原因,是由于催化剂在等离子协同过程中提供了大量的氧空位,使得NO_(x)充分氧化.多元复合型催化剂能在单一型的基础上,通过金属元素价态的变换和能量的传递进一步促进固氮效果,三元复合型催化剂Mn_(3)WCo/γ-Al_(2)O_(3)在电压为22 kV时的固氮最高总氮浓度为119.13 mg/L,较未填充催化剂组的最大值提升了71.61%,能耗降低了21.70%.

In order to promote the synergistic catalytic nitrogen fixation effect of dielectric barrier discharge(DBD),the single,binary and ternary supported catalysts with different Mn/Co/W elements were prepared in this paper,and the catalysts were placed in the DBD air gap for plasma co-catalytic nitrogen fixation reaction.The catalysts were characterized by XRD,SEM and EDS.The concentration of total nitrogen in liquid phase was determined by ultraviolet spectrophotometry and the experimental results showed that the concentration of total nitrogen in the experimental group filled with catalyst was significantly increased compared with that in the untreated group.Fourier transform infrared spectroscopy(FTIR)was used to detect the gas-phase products of DBD with or without catalyst filling.It was proved that catalyst filling could promote the formation of NO_(2) and N_(2)O_(5) in space.DBD gas-phase chain reactions and the principle of catalysis revealed that the total nitrogen concentration was increased because the catalyst provided a mass of oxygen vacancies in the plasma coordination process,making NO_(x) fully oxidized.Multiple compound catalysts can further promote the nitrogen fixation effect through the transformation of metal element valence state and energy transfer on the basis of single type.The highest total nitrogen concentration of the ternary compound catalyst Mn_(3)WCo/γ-Al_(2)O_(3) experimental group was obtained at the voltage of 22 kV,which was 119.13 mg/L.Compared with the maximum value of unfilled catalyst group,it increased by 71.61%.