光催化降解低浓度甲醛工艺研究与反应器设计
发布时间：2018-08-24 20:35
【摘要】：目前室内环境污染问题严重,而光催化技术无疑提供一个新颖的研究思路,我们可以利用光催化技术降解室内的空气污染物,并且越来越多的人对光催化技术感兴趣并投身于此。光催化反应器是光催化技术应用的载体,其内部的动力学过程复杂且影响因素繁多。反应器性能优化已成为光催化技术成功应用的一个关键步骤。本文以甲醛为目标污染物,在自行设计加工的光催化装置内进行反应,研究了光催化反应动力学的过程,并具体讨论了反应器的设计及优化,考察了甲醛降解过程的影响因素。本文的主要结论如下:(1)以光催化降解动力学为基础依据,分析现有催化剂膜厚模型,寻找以金属镍网为载体的理论膜厚模型,确定最佳膜厚,通过实验发现现有模型可以很好的预测以泡沫镍网为载体的光催化膜厚。通过实验和预测均发现,当催化剂膜厚增加时,降解率先增加后稳定。实验得到最优催化剂膜厚为86 nm与预测值基本吻合,通过在同一条件下对比其他催化剂如Ti02, Cu2O, BiVO4, g-C3N4可知,当催化剂膜厚增加时,甲醛降解率先增加后稳定在某一数值。实验得到最优催化剂膜厚均为86nm。说明此模型适用于其他不同种类的催化剂。(2)对比研究不同催化剂Ti02, BiVO4,Cu2O的结构(晶粒尺寸、BET、禁带宽度)和降解低浓度污染物来评价其性能优劣,优选出光催化性能较优的材料。通过结构分析和降解实验发现,当甲醛初始浓度较低时,BiV04降解率优于其他,随浓度增加,催化剂降解率均呈上升趋势,TiO2-1 (T-1).、Ti02-2 (T-2)降解率增加显著。随环境湿度增大,降解率先上升后下降,BiV04-1 (B-1)、BiV04-2 (B-2)降解率下降的较为缓慢。同一物质当晶粒尺寸越小BET越大,其降解率越好。T-2比B-1有更好的稳定性。为下一步反应器的设计提供更加高效稳定的光催化剂。(3)依据高效和节能的原则,以甲醛,光子和催化剂协调为目的,设计了四种光催化反应器,并对其光催化降解社能进行了实验研究。一字型反应器的斯坦顿数(Stm)和吸附平衡常数(K)较大,说明对流传质能力较强,但其反应有效度η和反应速率常数k明显很小,表明其反应能力很差,传质-反应能力并不匹配。当η接近0或者1均不好,只有在0.5时,说明反应速率和传质速率相当,催化剂的传质-反应能力匹配。所以效果最好的是45°型反应器。
[Abstract]:At present, the problem of indoor environmental pollution is serious, and photocatalytic technology undoubtedly provides a novel research idea. We can use photocatalytic technology to degrade indoor air pollutants. And more people are interested in and devoted to photocatalytic technology. Photocatalytic reactor is the carrier of photocatalytic technology. The optimization of reactor performance has become a key step in the successful application of photocatalytic technology. In this paper, the kinetics of photocatalytic reaction was studied in a photocatalytic device designed and processed with formaldehyde as the target pollutant. The design and optimization of the reactor were discussed in detail, and the factors influencing the degradation of formaldehyde were investigated. The main conclusions are as follows: (1) on the basis of photocatalytic degradation kinetics, the existing film thickness model of catalyst is analyzed, and the theoretical film thickness model based on metal nickel mesh is found to determine the best film thickness. It is found that the existing models can predict the thickness of photocatalytic film with nickel foam mesh as the carrier. It was found by experiments and predictions that when the film thickness of the catalyst increased, the degradation increased first and then stabilized. The experimental results show that the optimal film thickness of the catalyst is 86 nm, which is consistent with the predicted value. Compared with other catalysts such as Ti02, Cu2O, BiVO4, g-C3N4 under the same conditions, the degradation of formaldehyde is firstly increased and then stabilized at a certain value when the film thickness of the catalyst increases. The results show that the optimal film thickness of the catalyst is 86 nm. This model is suitable for other kinds of catalysts. (2) the structure (grain size and band gap) of Ti02, BiVO4,Cu2O and the degradation of low concentration pollutants are compared to evaluate its performance and select the materials with better photocatalytic performance. The results of structure analysis and degradation experiments showed that the degradation rate of BiV04 was better than that of others when the initial concentration of formaldehyde was low, and the degradation rate of TiO2-1 (T-1). Ti02-2 (T-2) increased significantly with the increase of formaldehyde concentration. With the increase of environmental humidity, the degradation rate of BiV04-1 (B-1) and BiV04-2 (B-2) decreased slowly. The smaller the grain size of the same material, the larger the BET, the better the degradation rate. T-2 has better stability than B-1. (3) according to the principle of high efficiency and energy saving, four kinds of photocatalytic reactors are designed for the purpose of coordination of formaldehyde, photon and catalyst. The photocatalytic degradation mechanism was studied experimentally. The Stanton number (Stm) and adsorption equilibrium constant (K) of the single-type reactor are larger, which indicates that the convection mass transfer ability is strong, but the reaction efficiency 畏 and the reaction rate constant k are obviously small, which indicates that the reaction ability is very poor and the mass transfer and reaction ability is not matched. When 畏 is close to 0 or 1, only when 畏 is close to 0 or 1, the reaction rate is equal to the mass transfer rate, and the mass transfer ability of the catalyst is matched. So the best effect is the 45 掳reactor.
【学位授予单位】：天津科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X51
本文编号：2201964
[Abstract]:At present, the problem of indoor environmental pollution is serious, and photocatalytic technology undoubtedly provides a novel research idea. We can use photocatalytic technology to degrade indoor air pollutants. And more people are interested in and devoted to photocatalytic technology. Photocatalytic reactor is the carrier of photocatalytic technology. The optimization of reactor performance has become a key step in the successful application of photocatalytic technology. In this paper, the kinetics of photocatalytic reaction was studied in a photocatalytic device designed and processed with formaldehyde as the target pollutant. The design and optimization of the reactor were discussed in detail, and the factors influencing the degradation of formaldehyde were investigated. The main conclusions are as follows: (1) on the basis of photocatalytic degradation kinetics, the existing film thickness model of catalyst is analyzed, and the theoretical film thickness model based on metal nickel mesh is found to determine the best film thickness. It is found that the existing models can predict the thickness of photocatalytic film with nickel foam mesh as the carrier. It was found by experiments and predictions that when the film thickness of the catalyst increased, the degradation increased first and then stabilized. The experimental results show that the optimal film thickness of the catalyst is 86 nm, which is consistent with the predicted value. Compared with other catalysts such as Ti02, Cu2O, BiVO4, g-C3N4 under the same conditions, the degradation of formaldehyde is firstly increased and then stabilized at a certain value when the film thickness of the catalyst increases. The results show that the optimal film thickness of the catalyst is 86 nm. This model is suitable for other kinds of catalysts. (2) the structure (grain size and band gap) of Ti02, BiVO4,Cu2O and the degradation of low concentration pollutants are compared to evaluate its performance and select the materials with better photocatalytic performance. The results of structure analysis and degradation experiments showed that the degradation rate of BiV04 was better than that of others when the initial concentration of formaldehyde was low, and the degradation rate of TiO2-1 (T-1). Ti02-2 (T-2) increased significantly with the increase of formaldehyde concentration. With the increase of environmental humidity, the degradation rate of BiV04-1 (B-1) and BiV04-2 (B-2) decreased slowly. The smaller the grain size of the same material, the larger the BET, the better the degradation rate. T-2 has better stability than B-1. (3) according to the principle of high efficiency and energy saving, four kinds of photocatalytic reactors are designed for the purpose of coordination of formaldehyde, photon and catalyst. The photocatalytic degradation mechanism was studied experimentally. The Stanton number (Stm) and adsorption equilibrium constant (K) of the single-type reactor are larger, which indicates that the convection mass transfer ability is strong, but the reaction efficiency 畏 and the reaction rate constant k are obviously small, which indicates that the reaction ability is very poor and the mass transfer and reaction ability is not matched. When 畏 is close to 0 or 1, only when 畏 is close to 0 or 1, the reaction rate is equal to the mass transfer rate, and the mass transfer ability of the catalyst is matched. So the best effect is the 45 掳reactor.
【学位授予单位】：天津科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X51
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