氢氯氟烃类（HCFCs）和氢氟烃类（HFCs）制冷剂具有极高的温室效应值，它们的替代、回收和处理工作对减少碳排放以及减缓全球气候变暖意义重大。现有废弃制冷剂的处理技术主要是高温焚烧热解法，该方法能耗高、成本高、碳排放高，与我国“碳中和”长远目标的宗旨相违背。为实现废弃制冷剂低能耗和环境友好降解处理，本文在课题组新的制冷剂降解思路，即通过太阳能光催化和热效应的协同作用，实现制冷剂在中温下的有效降解的框架下，选用目前广泛使用的HFC类制冷剂四氟乙烷（R134a）作为研究对象，对其热分解机理进行初步理论研究，并开展光热协同催化降解实验，探索R134a光热协同条件下的降解规律。本文采用密度泛函方法对R134a的热分解机理进行探究。首先提出了多种可能反应路径，得到R134a热分解时的优先断键情况，并指出在氧气或水分子存在的情况下，R134a更易分解；R134a和多种自由基发生反应，主要发生氢原子转移反应；且R134a易和OH自由基发生反应。设计并搭建光热协同催化反应实验装置，开展R134a在光热协同催化条件下的降解实验，并采用气相色谱仪（GC）对R134a和其降解产物进行定量分析。实验选用锐钛矿二氧化钛作为催化剂，在120℃时R134a的2 h降解率可超过95%，这体现了光热协同降解制冷剂方法的优越性。本文设计一系列实验探究温度、光强、氧气和水分含量对反应的影响情况，实验结果表示：温度和光强越高，R134a的降解速率和二氧化碳的生成速率越大；当氧气和R134a的浓度相同时，R134a降解不完全，当氧气浓度是R134a的2倍及以上时，R134a降解规律一致，且实验的矿化率在75%左右,每分子R134a降解消耗氧气的数目在1.2左右；少量水分的加入使R134a的降解速率变快，但过量水分对R134a降解具有抑制作用。实验表征结果证明R134a的副产物包括三氟乙烯、氟代乙炔和少量一氧化碳，且反应后的催化剂中出现了TiOF2。本文的研究为制冷剂在光热协同催化下的中温降解提供实验基础，推动了制冷剂降解新方法的探究。
Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) refrigerants have extremely high greenhouse effect values. Their replacement, recycling and treatment work are of great significance to reduce carbon emissions and slow global warming. The existing waste refrigerant treatment technology is mainly the high-temperature incineration pyrolysis method, which has high energy consumption, high cost, and high carbon emissions and runs counter to the long-term goal of "carbon neutrality" in my country. In order to achieve low energy consumption and environmentally friendly degradation treatment of waste refrigerants, this thesis uses the new refrigerant degradation ideas, namely, through the synergy of solar photocatalysis and thermal effects to achieve effective refrigerant degradation at moderate temperature. The widely used HFC refrigerant tetrafluoroethane (R134a) is used as the research substancce. The preliminary theoretical study of its thermal decomposition mechanism is carried out, and the photo-thermal synergistic catalytic degradation experiment is carried out to explore the degradation law of R134a under the condition of photo-thermal synergy.In this thesis, density functional theory is used to investigate the thermal decomposition mechanism of R134a. First, a variety of possible reaction paths are proposed to obtain the preferential bond breaking during thermal decomposition of R134a, and it is pointed out that in the presence of oxygen or water molecules, R134a is easier to be decomposed; R134a reacts with a variety of free radicals, mainly hydrogen atom transfer Reaction; and R134a easily reacts with OH radicals.This paper designs and builds an experimental device for the photothermal synergistic catalysis reaction, carries out the degradation experiment of R134a under the condition of photothermal synergistic catalysis, and uses gas chromatograph (GC) to quantitatively analyze R134a and its degradation products. In the experiment, anatase titanium dioxide is used as the catalyst, and the degradation rate of R134a in 2 h at 120℃ could exceed
