化学镀法制备用于有机废气催化燃烧处理的整体式催化剂的研究
发布时间：2018-07-24 17:03
【摘要】：目前,在众多有机废气处理技术中,催化燃烧法是消除挥发性有机化合物(VOCs)污染最有效方法之一,具有设备简单,能耗低,消除效果好等特点,而催化剂是催化燃烧法消除VOCs的关键。本文用堇青石蜂窝陶瓷做第一载体,以贵金属Pd为活性组分,用化学镀法制备了一系列Pd负载型整体式催化剂。以甲苯和甲醛的催化燃烧作为作为考察催化剂的探针反应,考察了催化剂的催化活性和耐高温性,并采用多种方法对催化剂进行表征,将催化燃烧性能与催化剂表面性质进行了关联以及进行了催化机理的探讨。本文的主要研究内容和结果如下： 催化剂的制备。采用化学镀法制备Pd/堇青石陶瓷整体式催化剂,通过实验确定了化学镀的最佳反应条件：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,温度：25℃-60℃。研究表明,采用化学镀制备技术可在堇青石陶瓷载体直接负载Pd颗粒,有利于提高钯的利用率,工艺简单,制备周期短。 催化剂的表征及活性评价。采用SEM、XRD、UV、EDX、BET、XPS、H_2-TPR、O_2-TPD等手段对整体式催化剂的表面形貌、结构和性能进行表征。通过SEM和EDX的测定,可知Pd晶粒均匀地负载在堇青石陶瓷载体。以甲苯和甲醛作为VOCs的代表污染物,进行催化燃烧处理,对催化剂进行活性评价,研究表明,当活性组分Pd负载量在0.36wt%以上时具有较高的催化活性,对于不同焙烧温度下制备的Pd/堇青石陶瓷整体式催化剂,500℃焙烧下的具有相对较高的催化活性,Pd晶粒在载体表面上均匀负载,晶粒大小均一,范围在100nm左右。之后随着焙烧温度(高于500℃)的升高,催化活性逐渐降低,主要与活性物种PdO颗粒的长大、烧结、晶格氧的减少和比表面积的减小有关。 研究了空速、有机废气中甲苯和甲醛的浓度和稳定性等因素对Pd/堇青石陶瓷整体式催化剂催化燃烧性能的影响。实验表明,随着空速的增大,催化剂对甲苯和甲醛的催化处理效率都逐渐降低。催化剂在空速20000h-1以内时,具有较高的甲苯催化处理效率；在3000h-1空速内时,对甲醛具有较高的催化处理效率；对于甲苯,甲苯浓度对催化燃烧处理效率影响较小,在6.0g/m3以内都具有较高的催化处理效率；对于甲醛,甲醛浓度在2.0mg/m3范围内时,催化剂才对其具有较高的处理效率,说明甲醛浓度对催化燃烧处理效率的影响较大,表明有机污染物的种类和浓度对催化处理效率有较明显影响,这也说明催化剂具有选择性。在甲苯催化燃烧的寿命实验中发现,在10h之内,Pd/堇青石陶瓷整体式催化剂的甲苯催化处理效率一直保持在99%左右,之后催化处理效率随着反应时间逐渐下降。重新焙烧再生的催化剂,在9h内甲苯催化处理效率可保持在99%,说明催化剂可多次再生循环使用。 研究还探讨了采用浸渍法在堇青石载体上负载一层CeO_2-ZrO_2复合物后,再采用化学镀负载上活性组分Pd,制备Pd/Ceo.gZro.202/堇青石陶瓷整体式催化剂,并采用SEM、EDX、UV漫反射对其进行表征。研究表明,该类催化剂具有良好的催化活性和耐高温性。相对于Pd/堇青石整体式催化剂,与500℃焙烧的催化剂相比,800℃焙烧的Pd/堇青石整体式催化剂,T99%为255℃,提高了25℃。800℃焙烧的0.36wt%Pd/Ce0.8Zr0.202/堇青石陶瓷整体式催化剂,T99%为250℃,与500℃焙烧的催化剂相比,只提高了15℃,主要可能是CeO_2-ZrO_2复合氧化物具有贮氧池的作用,可以向Pd提供品格氧,抑制了PdO晶粒的烧结,该催化剂是具有较好的催化活性的。
[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.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：O643.36
本文编号：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.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：O643.36
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