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燃煤电厂及工业窑炉的氮氧化物减排是改善空气质量的关键.现阶段选择性催化还原氮氧化物是最有效的技术途径,核心是采用以TiO_2为载体的钒基催化剂净化烟气.催化剂的活性是决定烟气净化效率的重要因素.近些年的研究主要集中在活性组分的替换上,但是由于其成本高昂,抗水抗硫性能较差,在实际中使用的效果不佳.本文从载体入手,制备了新型TiO_2载体,并采用特殊制备手段研发了新型高比表面积钒钛体系催化剂.通过对载体和催化剂的物化表征,研究了高比表面积TiO_2载体对于活性组分钒在表面分散的促进作用,及分散性的提高对氧化性和酸性的影响.所制新型TiO_2载体比表面积达到380.5 m~2/g,较商业化TiO_2载体提高了5倍.以此为载体,采用超声浸渍法和分段烧结的热处理方式,制备了钒负载量为5 wt%的新型钒钛催化剂.结果发现,高比表面载体显著提高了钒基催化剂比表面积为117.7 m~2/g,比传统钒钛催化剂提高了38%.计算结果表明,这种方式还提高了钒物种在载体表面的分散性.XRF结果表明,超声浸渍法和普通浸渍法均可将5 wt%的钒成功地负载到了载体上.通过模拟实际烟气成分对催化剂的脱硝效果进行了测试,结果表明,所制催化剂具备更宽的温度窗口及更好的N_2选择性,NO_x转化率在200–450°C时能保持在80%以上,比传统方法制备的催化剂温度窗口宽100°C.且N_2选择性在400°C以上时也明显更高.对两种催化剂样品的抗水抗硫能力进行了考察,发现在烟气中存在H_2O或SO_2时,高比表面积催化剂样品相较传统方法制备的催化剂具有更高的活性.Raman结果发现,在传统商业载体上钒物种由于分散不充分,更易在烧结过程中形成V-O-V物种,从而降低了催化剂的氧化还原性.而新型催化剂表面的V-O-Ti及V=O物种数量更多,这些物种活性更高,从而使得催化剂在低温下具有更高的NO_x转化率.采用NH_3-TPD,H_2-TPR和XPS技术研究了活性提高与催化剂结构的关系.结果发现,高比表面积载体通过对钒物种的分散作用,在载体表面由于二氧化钛载体的孔结构和钒物种的高活性,也使得该催化剂具有较高的酸量和氧化还原性.本文为制备新型烟气脱硝催化剂提供了理论依据,该技术方法具有较高的应用价值.
NOx emission reduction in coal-fired power plants and industrial furnaces is the key to improving air quality. At this stage, selective catalytic reduction of nitrogen oxides is the most effective technical approach. The core of the study is to purify the flue gas with a vanadium-based catalyst using TiO 2 as a carrier .Catalyst activity is an important factor to determine the flue gas purification efficiency.In recent years, the research mainly focused on the replacement of the active components, but due to its high cost, water and sulfur resistance is poor, the actual use of the effect is not In this paper, starting from the support, a new type of TiO 2 support was prepared and a new type of high specific surface area vanadium-titanium catalyst was developed by means of special preparation.The physical and chemical characterization of the support and the catalyst was used to study the effect of high specific surface area TiO 2 support on the active component vanadium The dispersion effect on the oxidation and the acidity of the novel TiO 2 support were investigated.The specific surface area of the new TiO 2 support reached 380.5 m 2 / g, which was 5 times higher than that of commercial TiO 2 support.With this as carrier, A novel vanadium-titanium catalyst with vanadium loading of 5 wt% was prepared by ultrasonic treatment and heat treatment by segmented sintering. The results showed that the vanadium-based catalyst The specific surface area of the catalyst was 117.7 m 2 / g, which was 38% higher than that of the conventional vanadium-titanium catalyst. The calculated results show that this method also enhances the dispersibility of vanadium species on the surface of the support.XRF results show that ultrasonic impregnation and ordinary impregnation Method can successfully load 5 wt% vanadium onto the carrier.The denitration effect of the catalyst was simulated by simulating the actual flue gas composition.The results show that the catalyst has a wider temperature window and better N 2 selectivity , NO_x conversion rate can be kept above 80% at 200-450 ° C, which is 100 ° C wider than that of the catalyst prepared by the conventional method, and the selectivity of N_2 is also significantly higher than 400 ° C. For both catalysts The anti-sulfur and anti-sulfur ability of the sample was investigated and it was found that H 2 O or SO 2 was present in the flue gas with higher specific surface area catalyst samples than the traditional method.Raman found that vanadium Species, due to insufficient dispersal, are more likely to form VOV species during sintering, thereby reducing the redox activity of the catalyst, whereas the new catalyst has more VO-Ti and V = O species on the surface and higher activity of these species The results showed that the catalyst with high specific surface area had the highest NOx conversion rate at low temperature.The NH 3 -TPD, H 2 -TPR and XPS techniques were used to study the relationship between the activity and catalyst structure. Due to the pore structure of titanium dioxide carrier and the high activity of vanadium species, the catalyst surface also has a high acidity and redox activity.This paper provides a theoretical basis for the preparation of a new flue gas denitration catalyst, which has high Value.