废催化剂微波氧化焙烧脱碳新技术研究
发布时间：2019-01-29 04:29
【摘要】：铂族金属催化剂被广泛应用于化工领域,现代化工生产中约有85%的反应离不开相应的催化剂,世界上70%的铑、40%的铂和50%的钯都应用于催化剂的制备。所以,从二次资源中回收铂族金属非常必要。由于失效废催化剂中积碳的存在或活性炭本身作为催化剂载体,因碳有较强的吸附性能,在浸出过程中,常造成铂族金属回收率降低。为提高铂族金属的回收效率,需预先将废催化剂进行焙烧脱碳处理。目前,废催化剂的常规焙烧预处理,存在能耗高,生产周期长等缺点。因此,急需寻求一种快速、能耗低的脱碳新技术。本文针对常规焙烧脱碳工艺存在的问题,结合微波选择性加热的特点,提出了微波焙烧脱碳新技术。本文在研究失效废催化剂微波介电特性及升温行为的基础上,开展了微波焙烧脱碳研究,并对脱碳反应机理进行了分析,以期为微波焙烧脱碳产业化应用提供理论依据。1.失效废催化剂微波介电特性研究失效废催化剂介电常数随温度的增大而升高,当温度由室温升高至750℃时,废催化剂介电常数εr由2.27增大至2.85;其介电常数随相对密度则呈线性增大关系,当物料相对密度由0.7g/cm3增大至1.25g/cm3,介电常数ε'γ由1.92增大至2.66;而相对密度对其穿透深度的影响则呈负指数关系,即当相对密度增大,穿透深度表现为指数性减小;废催化剂介电参数变温测试时,在450℃左右出现临界温度,当高于临界温度时,废催化剂的介电损耗显著升高,吸波性能将会明显增强,这一结论与废催化剂的实际升温行为数据相符合;在450℃时,其介电损耗ε'γ为0.012,升温至800℃时介电损耗为0.050。2.失效废催化剂微波加热升温行为研究失效废催化剂升温速度受物料厚度、微波功率影响较大。物料越厚,升温越慢;微波功率越大,升温越快。不同厚度条件(2 cm、3 cm、4 cm、5 cm)下,升温至 800℃所需的时间分别为 21min(2 cm)、23min(3 cm)、25min(4 cm)、42min(5cm);当物料厚度为4cm时,将功率从1kW提升至2.5kW,加热时间可缩短一半。3.失效废催化剂脱碳反应机理研究利用TG/DTG分析技术研究了失效废催化剂的氧化焙烧脱碳过程,针对废催化剂中积碳结构复杂的特点,分析了四种固相反应表观活化能计算方法(Coat-Redfern积分法、Ozawa积分法、Achar微分法和Kissinger微分法)的适用条件;其中,Coat-Redfern积分法和Achar微分法的使用需要预先确定反应的机理函数,Kissinger微分法的使用则需要反应过程不同升温速率DTG曲线的峰值温度(数据显示脱碳反应不同升温速率DTG曲线的峰值温度过于集中,Kissinger微分法不能使用),较之以上三种方法使用条件的局限性,可以使用适用范围较大的Ozawa积分法计算脱碳反应过程的表观活化能Ea;本论文采用满足线性拟合条件的Ozawa积分法详细研究了脱碳反应动力学过程,获得了脱碳反应过程中随转化率和温度变化的反应表观活化能数据。结果表明,在540℃左右,Ea随温度变化出现指数型递减的临界点,使表观活化能的值迅速降低,说明温度对表观活化能Ea有显著影响。反应过程中,温度区间(540℃,600℃)的表观活化能稳定在5kJ/mol-8kJ/mol;而温度区间(600℃,630℃)的表观活化能稳定在 2 kJ/mol-5kJ/mol。4.失效废催化剂脱碳研究在物料厚度2cm,温度600℃,脱碳时间40min条件下,常规脱碳率仅为96.7%,而微波脱碳率达99.5%,常规脱碳实现高效脱碳(脱碳率99.5%)时,需延长反应时间至120min。微波脱碳的最佳工艺参数为物料厚度2cm,温度600℃,脱碳时间40min,脱碳率达99.5%,满足后续工艺要求。
[Abstract]:The platinum group metal catalyst is widely used in the field of chemical industry, and about 85% of the reaction in the modern chemical production can not be separated from the corresponding catalyst. In the world, 70% of the sulfur, 40% of the platinum and 50% of the sulfur are applied to the preparation of the catalyst. Therefore, it is necessary to recover the platinum group metal from the secondary resource. because of the presence of the product carbon in the spent catalyst or the active carbon itself as the catalyst support, the recovery of the platinum group metal is often reduced during the leaching process due to the strong adsorption performance of the carbon. In order to improve the recovery efficiency of the platinum group metal, the waste catalyst needs to be pre-baked and decarbonized. At present, the conventional roasting pretreatment of the waste catalyst has the defects of high energy consumption, long production cycle and the like. Therefore, it is urgent to seek a new and rapid decarbonization technology with low energy consumption. In the light of the problems in the conventional roasting and decarbonization process, the new technology of microwave roasting and decarbonization is put forward in combination with the characteristics of microwave selective heating. In this paper, on the basis of the study of the microwave dielectric properties and temperature rise behavior of the failure waste catalyst, the study of microwave roasting and decarbonization is carried out, and the mechanism of the decarbonization reaction is analyzed, with a view to providing a theoretical foundation for the application of the microwave roasting and decarbonization industrialization. The dielectric constant of the spent catalyst is increased with the increase of the temperature, and when the temperature is increased from room temperature to 750 鈩，
本文编号：2417644
[Abstract]:The platinum group metal catalyst is widely used in the field of chemical industry, and about 85% of the reaction in the modern chemical production can not be separated from the corresponding catalyst. In the world, 70% of the sulfur, 40% of the platinum and 50% of the sulfur are applied to the preparation of the catalyst. Therefore, it is necessary to recover the platinum group metal from the secondary resource. because of the presence of the product carbon in the spent catalyst or the active carbon itself as the catalyst support, the recovery of the platinum group metal is often reduced during the leaching process due to the strong adsorption performance of the carbon. In order to improve the recovery efficiency of the platinum group metal, the waste catalyst needs to be pre-baked and decarbonized. At present, the conventional roasting pretreatment of the waste catalyst has the defects of high energy consumption, long production cycle and the like. Therefore, it is urgent to seek a new and rapid decarbonization technology with low energy consumption. In the light of the problems in the conventional roasting and decarbonization process, the new technology of microwave roasting and decarbonization is put forward in combination with the characteristics of microwave selective heating. In this paper, on the basis of the study of the microwave dielectric properties and temperature rise behavior of the failure waste catalyst, the study of microwave roasting and decarbonization is carried out, and the mechanism of the decarbonization reaction is analyzed, with a view to providing a theoretical foundation for the application of the microwave roasting and decarbonization industrialization. The dielectric constant of the spent catalyst is increased with the increase of the temperature, and when the temperature is increased from room temperature to 750 鈩，
本文编号：2417644
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