化學鍍法制備用于有機廢氣催化燃燒處理的整體式催化劑的研究
發(fā)布時間：2018-07-24 17:03
【摘要】：目前,在眾多有機廢氣處理技術中,催化燃燒法是消除揮發(fā)性有機化合物(VOCs)污染最有效方法之一,具有設備簡單,能耗低,消除效果好等特點,而催化劑是催化燃燒法消除VOCs的關鍵。本文用堇青石蜂窩陶瓷做第一載體,以貴金屬Pd為活性組分,用化學鍍法制備了一系列Pd負載型整體式催化劑。以甲苯和甲醛的催化燃燒作為作為考察催化劑的探針反應,考察了催化劑的催化活性和耐高溫性,并采用多種方法對催化劑進行表征,將催化燃燒性能與催化劑表面性質(zhì)進行了關聯(lián)以及進行了催化機理的探討。本文的主要研究內(nèi)容和結果如下： 催化劑的制備。采用化學鍍法制備Pd/堇青石陶瓷整體式催化劑,通過實驗確定了化學鍍的最佳反應條件：PdCl_2:0.05-0.5g/L, NH_3·H_2O (25%):40-120g/L, NH4Cl: 5-20g/L, NaH_2PO_2·H_2O:1-10g/L, HCl(36-38%):1-4mL/L, pH:9-10,溫度：25℃-60℃。研究表明,采用化學鍍制備技術可在堇青石陶瓷載體直接負載Pd顆粒,有利于提高鈀的利用率,工藝簡單,制備周期短。 催化劑的表征及活性評價。采用SEM、XRD、UV、EDX、BET、XPS、H_2-TPR、O_2-TPD等手段對整體式催化劑的表面形貌、結構和性能進行表征。通過SEM和EDX的測定,可知Pd晶粒均勻地負載在堇青石陶瓷載體。以甲苯和甲醛作為VOCs的代表污染物,進行催化燃燒處理,對催化劑進行活性評價,研究表明,當活性組分Pd負載量在0.36wt%以上時具有較高的催化活性,對于不同焙燒溫度下制備的Pd/堇青石陶瓷整體式催化劑,500℃焙燒下的具有相對較高的催化活性,Pd晶粒在載體表面上均勻負載,晶粒大小均一,范圍在100nm左右。之后隨著焙燒溫度(高于500℃)的升高,催化活性逐漸降低,主要與活性物種PdO顆粒的長大、燒結、晶格氧的減少和比表面積的減小有關。 研究了空速、有機廢氣中甲苯和甲醛的濃度和穩(wěn)定性等因素對Pd/堇青石陶瓷整體式催化劑催化燃燒性能的影響。實驗表明,隨著空速的增大,催化劑對甲苯和甲醛的催化處理效率都逐漸降低。催化劑在空速20000h-1以內(nèi)時,具有較高的甲苯催化處理效率；在3000h-1空速內(nèi)時,對甲醛具有較高的催化處理效率；對于甲苯,甲苯濃度對催化燃燒處理效率影響較小,在6.0g/m3以內(nèi)都具有較高的催化處理效率；對于甲醛,甲醛濃度在2.0mg/m3范圍內(nèi)時,催化劑才對其具有較高的處理效率,說明甲醛濃度對催化燃燒處理效率的影響較大,表明有機污染物的種類和濃度對催化處理效率有較明顯影響,這也說明催化劑具有選擇性。在甲苯催化燃燒的壽命實驗中發(fā)現(xiàn),在10h之內(nèi),Pd/堇青石陶瓷整體式催化劑的甲苯催化處理效率一直保持在99%左右,之后催化處理效率隨著反應時間逐漸下降。重新焙燒再生的催化劑,在9h內(nèi)甲苯催化處理效率可保持在99%,說明催化劑可多次再生循環(huán)使用。 研究還探討了采用浸漬法在堇青石載體上負載一層CeO_2-ZrO_2復合物后,再采用化學鍍負載上活性組分Pd,制備Pd/Ceo.gZro.202/堇青石陶瓷整體式催化劑,并采用SEM、EDX、UV漫反射對其進行表征。研究表明,該類催化劑具有良好的催化活性和耐高溫性。相對于Pd/堇青石整體式催化劑,與500℃焙燒的催化劑相比,800℃焙燒的Pd/堇青石整體式催化劑,T99%為255℃,提高了25℃。800℃焙燒的0.36wt%Pd/Ce0.8Zr0.202/堇青石陶瓷整體式催化劑,T99%為250℃,與500℃焙燒的催化劑相比,只提高了15℃,主要可能是CeO_2-ZrO_2復合氧化物具有貯氧池的作用,可以向Pd提供品格氧,抑制了PdO晶粒的燒結,該催化劑是具有較好的催化活性的。
[Abstract]:At present, in many organic waste gas treatment technologies, catalytic combustion is one of the most effective methods to eliminate the pollution of volatile organic compounds (VOCs). It has the characteristics of simple equipment, low energy consumption and good elimination effect. The catalyst is the key to the elimination of VOCs by catalytic combustion method. The first carrier of cordierite honeycomb ceramics and the activity of Pd as the activity of precious metals are used in this paper. A series of Pd loaded monolithic catalysts were prepared by electroless plating. The catalytic combustion of toluene and formaldehyde was used as a probe reaction as an investigation catalyst. The catalytic activity and high temperature resistance of the catalyst were investigated. Various methods were used to characterize the catalyst. The catalytic combustion properties were related to the surface properties of the catalyst. The main contents and results of this study are as follows:
Preparation of the catalyst. Pd/ cordierite ceramic monolithic catalyst was prepared by electroless plating. The optimum reaction conditions for electroless plating were determined by experiments: PdCl_2:0.05-0.5g/L, NH_3. H_2O (25%): 40-120g/L, NH4Cl: 5-20g/L, NaH_2PO_2. H_2O:1-10g/L, HCl (36-38%): 1-4mL/L, temperature: 25 degrees C The plating technology can directly load Pd particles on cordierite ceramic carrier, which is conducive to improving the utilization rate of palladium, simple process and short preparation period.
The characterization and activity evaluation of the catalyst. Using SEM, XRD, UV, EDX, BET, XPS, H_2-TPR, O_2-TPD and other means to characterize the surface morphology, structure and properties of the monolithic catalyst. By the determination of SEM and EDX, the Pd grain is uniformly loaded on the cordierite ceramic carrier. Methylene and formaldehyde are used as the representative pollutants for the VOCs, and the catalytic combustion is carried out. The activity evaluation of the catalyst shows that the active component Pd has higher catalytic activity when the load is above 0.36wt%, and the Pd/ cordierite ceramic monolithic catalyst prepared at different calcination temperatures has relatively high catalytic activity at 500 C, and the grain size of the Pd grain on the surface of the carrier is uniformly loaded and the grain size is the size. Homogeneous, the range is about 100nm, and the catalytic activity gradually decreases with the rise of the calcination temperature (higher than 500). It is mainly related to the growth of PdO particles in the active species, the reduction of the lattice oxygen and the reduction of the specific surface area.
The effects of air velocity, concentration and stability of toluene and formaldehyde in organic waste gas on the catalytic combustion performance of Pd/ cordierite ceramic catalyst were studied. The experimental results showed that the catalytic efficiency of the catalyst to toluene and formaldehyde gradually decreased with the increase of air velocity. The catalyst had higher toluene when the catalyst was less than 20000h-1. The catalytic efficiency of the catalyst is higher at 3000h-1 airspeed; for toluene, the concentration of toluene has little effect on the efficiency of the catalytic combustion treatment, and has a higher catalytic efficiency within 6.0g/m3. For formaldehyde, the catalyst has a higher treatment when the concentration of formaldehyde is within the range of 2.0mg/m3. It shows that the concentration of formaldehyde has a great influence on the efficiency of catalytic combustion treatment, indicating that the type and concentration of organic pollutants have a significant effect on the efficiency of the catalytic treatment, which also shows the selectivity of the catalyst. In the life experiment of the catalytic combustion of toluene, the toluene catalyst of the Pd / cordierite ceramic monolithic catalyst is found within 10h. The efficiency of the catalyst was kept at about 99%, and the catalytic efficiency decreased with the reaction time. The rebaked catalyst was reroasted. The catalytic efficiency of toluene in 9h could be kept at 99%, indicating that the catalyst could be recycled for many times.
The study also discusses the preparation of Pd/Ceo.gZro.202/ cordierite ceramic monolithic catalyst by using the active component Pd on the electroless plating load on the cordierite carrier by loading a layer of CeO_2-ZrO_2 complex on the cordierite carrier and characterizing it with SEM, EDX, UV diffuse reflection. The study shows that the catalyst has good catalytic activity and high resistance to high activity. Compared with the Pd/ cordierite catalyst, the Pd/ Cordierite Monolithic Catalyst roasted at 800 C, compared with the Pd/ cordierite catalyst, was 255 C, and the 0.36wt%Pd/Ce0.8Zr0.202/ cordierite ceramic monolithic catalyst roasted at 25 C at.800 C was raised, and T99% was 250 C, and the main catalyst was 15 centigrade compared with the 500 C catalyst. It is possible that the CeO_2-ZrO_2 compound oxide has the effect of the oxygen storage tank, which can supply the oxygen to the Pd and inhibit the sintering of the PdO grain. The catalyst has good catalytic activity.
【學位授予單位】：廣東工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：O643.36
本文編號：2142055
[Abstract]:At present, in many organic waste gas treatment technologies, catalytic combustion is one of the most effective methods to eliminate the pollution of volatile organic compounds (VOCs). It has the characteristics of simple equipment, low energy consumption and good elimination effect. The catalyst is the key to the elimination of VOCs by catalytic combustion method. The first carrier of cordierite honeycomb ceramics and the activity of Pd as the activity of precious metals are used in this paper. A series of Pd loaded monolithic catalysts were prepared by electroless plating. The catalytic combustion of toluene and formaldehyde was used as a probe reaction as an investigation catalyst. The catalytic activity and high temperature resistance of the catalyst were investigated. Various methods were used to characterize the catalyst. The catalytic combustion properties were related to the surface properties of the catalyst. The main contents and results of this study are as follows:
Preparation of the catalyst. Pd/ cordierite ceramic monolithic catalyst was prepared by electroless plating. The optimum reaction conditions for electroless plating were determined by experiments: PdCl_2:0.05-0.5g/L, NH_3. H_2O (25%): 40-120g/L, NH4Cl: 5-20g/L, NaH_2PO_2. H_2O:1-10g/L, HCl (36-38%): 1-4mL/L, temperature: 25 degrees C The plating technology can directly load Pd particles on cordierite ceramic carrier, which is conducive to improving the utilization rate of palladium, simple process and short preparation period.
The characterization and activity evaluation of the catalyst. Using SEM, XRD, UV, EDX, BET, XPS, H_2-TPR, O_2-TPD and other means to characterize the surface morphology, structure and properties of the monolithic catalyst. By the determination of SEM and EDX, the Pd grain is uniformly loaded on the cordierite ceramic carrier. Methylene and formaldehyde are used as the representative pollutants for the VOCs, and the catalytic combustion is carried out. The activity evaluation of the catalyst shows that the active component Pd has higher catalytic activity when the load is above 0.36wt%, and the Pd/ cordierite ceramic monolithic catalyst prepared at different calcination temperatures has relatively high catalytic activity at 500 C, and the grain size of the Pd grain on the surface of the carrier is uniformly loaded and the grain size is the size. Homogeneous, the range is about 100nm, and the catalytic activity gradually decreases with the rise of the calcination temperature (higher than 500). It is mainly related to the growth of PdO particles in the active species, the reduction of the lattice oxygen and the reduction of the specific surface area.
The effects of air velocity, concentration and stability of toluene and formaldehyde in organic waste gas on the catalytic combustion performance of Pd/ cordierite ceramic catalyst were studied. The experimental results showed that the catalytic efficiency of the catalyst to toluene and formaldehyde gradually decreased with the increase of air velocity. The catalyst had higher toluene when the catalyst was less than 20000h-1. The catalytic efficiency of the catalyst is higher at 3000h-1 airspeed; for toluene, the concentration of toluene has little effect on the efficiency of the catalytic combustion treatment, and has a higher catalytic efficiency within 6.0g/m3. For formaldehyde, the catalyst has a higher treatment when the concentration of formaldehyde is within the range of 2.0mg/m3. It shows that the concentration of formaldehyde has a great influence on the efficiency of catalytic combustion treatment, indicating that the type and concentration of organic pollutants have a significant effect on the efficiency of the catalytic treatment, which also shows the selectivity of the catalyst. In the life experiment of the catalytic combustion of toluene, the toluene catalyst of the Pd / cordierite ceramic monolithic catalyst is found within 10h. The efficiency of the catalyst was kept at about 99%, and the catalytic efficiency decreased with the reaction time. The rebaked catalyst was reroasted. The catalytic efficiency of toluene in 9h could be kept at 99%, indicating that the catalyst could be recycled for many times.
The study also discusses the preparation of Pd/Ceo.gZro.202/ cordierite ceramic monolithic catalyst by using the active component Pd on the electroless plating load on the cordierite carrier by loading a layer of CeO_2-ZrO_2 complex on the cordierite carrier and characterizing it with SEM, EDX, UV diffuse reflection. The study shows that the catalyst has good catalytic activity and high resistance to high activity. Compared with the Pd/ cordierite catalyst, the Pd/ Cordierite Monolithic Catalyst roasted at 800 C, compared with the Pd/ cordierite catalyst, was 255 C, and the 0.36wt%Pd/Ce0.8Zr0.202/ cordierite ceramic monolithic catalyst roasted at 25 C at.800 C was raised, and T99% was 250 C, and the main catalyst was 15 centigrade compared with the 500 C catalyst. It is possible that the CeO_2-ZrO_2 compound oxide has the effect of the oxygen storage tank, which can supply the oxygen to the Pd and inhibit the sintering of the PdO grain. The catalyst has good catalytic activity.
【學位授予單位】：廣東工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：O643.36
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