【摘要】：鉑族金屬催化劑被廣泛應(yīng)用于化工領(lǐng)域,現(xiàn)代化工生產(chǎn)中約有85%的反應(yīng)離不開相應(yīng)的催化劑,世界上70%的銠、40%的鉑和50%的鈀都應(yīng)用于催化劑的制備。所以,從二次資源中回收鉑族金屬非常必要。由于失效廢催化劑中積碳的存在或活性炭本身作為催化劑載體,因碳有較強(qiáng)的吸附性能,在浸出過程中,常造成鉑族金屬回收率降低。為提高鉑族金屬的回收效率,需預(yù)先將廢催化劑進(jìn)行焙燒脫碳處理。目前,廢催化劑的常規(guī)焙燒預(yù)處理,存在能耗高,生產(chǎn)周期長(zhǎng)等缺點(diǎn)。因此,急需尋求一種快速、能耗低的脫碳新技術(shù)。本文針對(duì)常規(guī)焙燒脫碳工藝存在的問題,結(jié)合微波選擇性加熱的特點(diǎn),提出了微波焙燒脫碳新技術(shù)。本文在研究失效廢催化劑微波介電特性及升溫行為的基礎(chǔ)上,開展了微波焙燒脫碳研究,并對(duì)脫碳反應(yīng)機(jī)理進(jìn)行了分析,以期為微波焙燒脫碳產(chǎn)業(yè)化應(yīng)用提供理論依據(jù)。1.失效廢催化劑微波介電特性研究失效廢催化劑介電常數(shù)隨溫度的增大而升高,當(dāng)溫度由室溫升高至750℃時(shí),廢催化劑介電常數(shù)εr由2.27增大至2.85;其介電常數(shù)隨相對(duì)密度則呈線性增大關(guān)系,當(dāng)物料相對(duì)密度由0.7g/cm3增大至1.25g/cm3,介電常數(shù)ε'γ由1.92增大至2.66;而相對(duì)密度對(duì)其穿透深度的影響則呈負(fù)指數(shù)關(guān)系,即當(dāng)相對(duì)密度增大,穿透深度表現(xiàn)為指數(shù)性減小;廢催化劑介電參數(shù)變溫測(cè)試時(shí),在450℃左右出現(xiàn)臨界溫度,當(dāng)高于臨界溫度時(shí),廢催化劑的介電損耗顯著升高,吸波性能將會(huì)明顯增強(qiáng),這一結(jié)論與廢催化劑的實(shí)際升溫行為數(shù)據(jù)相符合;在450℃時(shí),其介電損耗ε'γ為0.012,升溫至800℃時(shí)介電損耗為0.050。2.失效廢催化劑微波加熱升溫行為研究失效廢催化劑升溫速度受物料厚度、微波功率影響較大。物料越厚,升溫越慢;微波功率越大,升溫越快。不同厚度條件(2 cm、3 cm、4 cm、5 cm)下,升溫至 800℃所需的時(shí)間分別為 21min(2 cm)、23min(3 cm)、25min(4 cm)、42min(5cm);當(dāng)物料厚度為4cm時(shí),將功率從1kW提升至2.5kW,加熱時(shí)間可縮短一半。3.失效廢催化劑脫碳反應(yīng)機(jī)理研究利用TG/DTG分析技術(shù)研究了失效廢催化劑的氧化焙燒脫碳過程,針對(duì)廢催化劑中積碳結(jié)構(gòu)復(fù)雜的特點(diǎn),分析了四種固相反應(yīng)表觀活化能計(jì)算方法(Coat-Redfern積分法、Ozawa積分法、Achar微分法和Kissinger微分法)的適用條件;其中,Coat-Redfern積分法和Achar微分法的使用需要預(yù)先確定反應(yīng)的機(jī)理函數(shù),Kissinger微分法的使用則需要反應(yīng)過程不同升溫速率DTG曲線的峰值溫度(數(shù)據(jù)顯示脫碳反應(yīng)不同升溫速率DTG曲線的峰值溫度過于集中,Kissinger微分法不能使用),較之以上三種方法使用條件的局限性,可以使用適用范圍較大的Ozawa積分法計(jì)算脫碳反應(yīng)過程的表觀活化能Ea;本論文采用滿足線性擬合條件的Ozawa積分法詳細(xì)研究了脫碳反應(yīng)動(dòng)力學(xué)過程,獲得了脫碳反應(yīng)過程中隨轉(zhuǎn)化率和溫度變化的反應(yīng)表觀活化能數(shù)據(jù)。結(jié)果表明,在540℃左右,Ea隨溫度變化出現(xiàn)指數(shù)型遞減的臨界點(diǎn),使表觀活化能的值迅速降低,說明溫度對(duì)表觀活化能Ea有顯著影響。反應(yīng)過程中,溫度區(qū)間(540℃,600℃)的表觀活化能穩(wěn)定在5kJ/mol-8kJ/mol;而溫度區(qū)間(600℃,630℃)的表觀活化能穩(wěn)定在 2 kJ/mol-5kJ/mol。4.失效廢催化劑脫碳研究在物料厚度2cm,溫度600℃,脫碳時(shí)間40min條件下,常規(guī)脫碳率僅為96.7%,而微波脫碳率達(dá)99.5%,常規(guī)脫碳實(shí)現(xiàn)高效脫碳(脫碳率99.5%)時(shí),需延長(zhǎng)反應(yīng)時(shí)間至120min。微波脫碳的最佳工藝參數(shù)為物料厚度2cm,溫度600℃,脫碳時(shí)間40min,脫碳率達(dá)99.5%,滿足后續(xù)工藝要求。
[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，

本文編號(hào)：2417644