赤泥催化SCR脱硝反应机理及其优化改性机制研究

The industrial red mud waste will be investigated in the issue of SCR denitration catalysts in this proposal for the first time, and the heating technique of Non-ionizing radiation will be creatively introduced to the thermal treatment process of catalysts. The samples of red mud will be obtained by extensive sampling analysis to have proper active ingredients and they should be selectively dealkalized. The preparation plan of the SCR catalysts of red mud will be explored and their denitration performance will be investigated on a fixed-bed denitration experimental table. Several advanced characterization methods such as BET, XRD, XPS, SEM, H2-TPR, GFTIR, DRIFTS will be used to study the influence of several factors, such as calcination conditions, radiation parameters, alkali metal, transition metal, rare-earth additives, SO2 and vapour, on the physicochemical properties of red mud as SCR catalysts. Meanwhile, the effects of those factors on the denitration performance of catalysts will be studied. The mechanism of modified optimization of catalysts and the mechanism of selective catalytic reduction over the catalysts will be revealed. This is a brand new program employing the red mud waste produced in the process of the industrial aluminum to explore its innovational resource utilization. Also, this is a creative attempt that apply the metal landfills to the fields of SCR denitration. If it eventually achieves its goal smoothly and realizes the moderate price and eco-friendly effective utilization of the SCR catalysts of red mud, that will work out a bunch of domestic severe environmental issues brought by the stack of the wasted red mud and the serious problem of the loss of heavy metal in vanadium-titanium catalysts, thus, it will has considerable social, environmental and economical significance.

本项目提出将工业废弃赤泥应用于SCR脱硝催化剂研究，并在催化剂热处理工艺中引入非游离辐射加热技术。在对赤泥进行广泛取样分析、适宜样品选择性脱碱基础上，探索优化赤泥SCR催化剂制备方案；借助XRD、XPS、H2-TPR、GFTIR、DRIFTS等先进表征手段研究煅烧条件、非游离辐射参数、碱金属杂质等对赤泥SCR催化剂相关理化性质及脱硝性能的影响机制；探索赤泥催化剂抗硫抗水性能，并对其失活机理及再生方案进行深入探究；针对赤泥催化剂主要性能缺陷，采用过渡金属及稀土元素掺杂对赤泥SCR催化剂优化改性，揭示其改性机理及其催化SCR反应机理。本项目是对工业炼铝废弃赤泥资源化利用方式的全新探索，有望实现价格低廉、环境友好的高效赤泥SCR催化剂制备，其应用将一举解决国内废弃赤泥堆放带来的严重环境问题及传统钒钛系催化剂存在的重金属钒流失问题，具有重要的社会、环保及经济意义。

传统钒钛类SCR脱硝催化剂因其固有缺点，应用日趋受限。铝业废弃物赤泥富含脱硝活性成分Fe2O3，开发以赤泥为原料的铁基脱硝催化剂可以取得经济、环保、固废利用等多重收益。. 在分析、研究赤泥主要成分Fe2O3与TiO2协同脱硝机理基础上，从大量铝业废弃物中筛选出不同地域16种代表性赤泥，测试其物化特性和脱硝活性，精选出高铁低碱拜耳法赤泥为研究对象，对其脱碱工艺、助剂改性、外场优化、量化模拟，成型配方等进行专门研究。研究发现原始赤泥脱硝效率与Fe2O3含量正相关，与碱含量负相关，效率较低，且碱是影响该效率值的主因；酸洗+煅烧是赤泥活化的有效方法，选择性脱碱并富集铁的酸洗技术可脱除赤泥97.6%的碱性物质，保留约92%的活性铁等氧化物；该技术提高了：赤泥比表面积150%、表面吸附氧28%、氧化还原能力30%与表面酸性76%；煅烧后酸洗赤泥在310-430℃脱硝效率超过90%，同时表现出良好的抗中毒性能；硝酸铈改性使赤泥催化剂低温活性大幅提升，T90温度窗口为225-415℃，其一阶反应速率τ为20.28 mL3·g-1·s-1，初始反应速率k为15.64 μmol·m-2·s-1，反应速度较未改性前提高约3.64倍；通过in situ FT-IR研究发现，Ce改性催化剂参与的NH3-SCR反应同时遵循Langmuir-Hinshelwood及Eley-Rideal反应机理；采用Co-Cr复合助剂改性Fe2O3基催化剂具有优良的抗硫、抗水及抗中毒能力，在高水高硫气氛下保持90%以上脱硝活性；超声外场介入未改变赤泥以Fe2O3为主的物相结构，但可优化催化剂的晶粒尺寸、孔径分布、比表面积及活性组分均匀程度，并使温度窗口向低温方向拓展15℃以上；量化模拟计算发现过渡金属、碱金属可以掺杂到Fe2O3超晶胞的表面，改变其表面结构和物化性能，Ti掺杂Fe2O3体系中的氧空位形成能降低，从而增强了NH3和O2的吸附，并使表面酸性增加，表面活性氧数量提高；碱金属掺杂可使得NH3在B酸位点的吸附受到明显抑制，降低其总体SCR活性；整体式赤泥脱硝催化剂成型工艺的探讨表明，选用活性炭、甘油、催化剂纤维、田菁粉制备的蜂窝状催化剂在275-475℃温度区间脱硝效率在90%以上。. 赤泥SCR脱硝催化剂经济、高效、环保，具有替代传统商用脱硝催化剂的应用潜力。