对氯苯酚电氧化过程中Pt电极的失活机制

利用线性伏安法、LC/MS和光谱技术研究了Pt电极在电化学氧化降解对氯苯酚过程中的失活现象.结果表明,由于电极表面的聚合反应, Pt电极会在短时间内失活.现场红外分析表明,电氧化过程中Pt电极在1200cm-1和1800cm-1,处分别出现了芳醚和羰基的特征吸收峰.提高对氯苯酚初始浓度和溶液pH均会加快电极的失活速率.对失活Pt电极的乙腈浸洗液进行LC/MS分析表明,电极表面形成的聚合物并不是具有单一结构的化合物,而是一些混合物,其形成的机理主要包括自由基之间的相互偶合、自由基与底物、中间产物或低聚物的取代反应等方式.     

The influence of temperature on the deactivation of commercial Pd/Rh automotive catalysts

Automotive catalyst deactivation can be promoted by thermal and poisoning mechanisms. Catalyst efficiency is reduced by thermal degradation resulting in the agglomeration of precious metals and the reduction of the washcoat surface area. In this paper, the temperature influence on the commercial Pd/Rh-based automotive catalyst performance was studied. Textural and physicochemical characterisation techniques were employed, such as X-ray fluorescence (XRF), atomic absorption spectrometry (AAS), N₂ physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM–EDX). The catalysts were evaluated for CO and propane oxidation with a stoichiometric gas mixture similar to engine exhaust gas. The results indicated the transformation of alumina into high temperature phases and the formation of new mixed oxide phases. Evidence of sintered particles and several spots of palladium agglomerates was seen by SEM–EDX analysis. The activity results showed the effects of thermal deactivation on the conversion of the pollutants. In spite of exposure to extreme temperature conditions (72 h at 1200 °C), significant activity was still observed for carbon monoxide and propane oxidation reactions.     

TiO_2光催化氧化室内VOCs的失活再生研究进展

半导体TiO2纳米材料由于其无毒无害,化学性质稳定等优点,目前已经成为环境污染控制领域和材料学领域共同研究的热点。TiO2纳米材料对环境污染物光催化氧化效果显著,但是随着TiO2的反复使用,其催化效率会减低,最终失去光催化的活性;文章主要对TiO2在光催化降解环境污染物后的失活和再生情况进行了综述,讨论了TiO2光催化剂失活的机理以及其再生的途径。     

汽车排气净化催化剂综合性能的研究

对HR-1型稀土复合氧化物催化剂进行了活性评价,实验结果表明,该催化剂具有良好的温度和空速特性,耐高温性能好;经60000km行车使用后,催化剂仍保持良好的活性;对行车后的催化剂进行了综合分析,说明HR-1型催化剂在一定程度上能够经受燃油带入的铅、磷、锌等物质的侵袭;高温热冲击所造成的催化剂比表面的减少乃是催化剂性能降低的主要原因.     

Upgrading of bio-oil from palm kernel shell by catalytic cracking in the presence of HZSM-5

Upgrading of bio-oil extracted from palm kernel shell (PKS) was performed using a lab-scale fixed-bed reactor with HZSM-5 as a catalyst. The catalytic cracking was carried out at optimized conditions: 0.3-MPa pressure, temperature of 500°C, and oil to catalyst ratio of 1:5. One of the challenges in upgrading bio-oil by catalytic cracking is deactivation of catalyst due to coke formation on catalyst surface. To overcome coke deposition, the upgrading process was carried out at 0.3-MPa pressure. Characterization of raw and upgraded bio-oil obtained through catalytic cracking was discussed in detail, indicating improvement in its physical properties. The distribution of products after cracking of bio-oil includes 58.89 wt% of organic liquid product, 15.63 wt% of aqueous fraction, 7.84 wt% of coke, and 17.64 wt% of gases. The degree of deoxygenation and calorific value of organic liquid product is 43.74% and 31.65 MJ/kg respectively. Organic liquid product obtained comprises 17.55% of hydrocarbons within the gasoline range. Hence, HZSM-5 proved its effectiveness for upgrading the bio-oil in a continuous mode.     

负载型TiO2在印染废水降解中的失活及原因分析

研究了负载型TiO2光催化剂在印染废水降解中的失活及其产生的原因。实验结果说明，催化剂活性下降的主要原因有：废水中不溶于水的染料等悬浮物和催化反应中产生的无定形碳在催化剂表面的吸附；高含量的无机离子对催化剂活性位的占据或在表面的沉积；长时间的使用和反复冲洗使TiO2负载量减少。通过同时采用灼烧和酸洗的方法可以使TiO2的活性恢复到新催化剂的69．5％。     

Biological effects of indoor sunlight in ruraldweling houses

ＢｉｏｌｏｇｉｃａｌｅｆｆｅｃｔｓｏｆｉｎｄｏｏｒｓｕｎｌｉｇｈｔｉｎｒｕｒａｌｄｗｅｌｉｎｇｈｏｕｓｅｓＣｈｅｎＧｕｉｆｕ，ＱｉｕＳｈｉｃｏｎｇ（ＷａｎｎａｎＭｅｄｉｃａｌＣｏｌｌｅｇｅ，Ｗｕｈｕ２４１００１，Ｃｈｉｎａ）Ｂｉｏｌｏｇｉｃａｌｅｆｆ...     

负载型稀土复合氧化物燃烧催化剂的失活研究

本文探讨了负载型稀土复合氧化物燃烧催化剂在使用过程中失活的主要特征.通过XRD,TEM,BET比表面测定及不同使用期的活性测定.证实催化剂在使用后的4—8个月内,烧结是失活的主因;而XPS谱显示硫中毒有积累性,以SO_4~(2-)形式沉积于催化剂表面,构成了燃烧催化剂后期失活的主要因素.由于催化燃烧反应在较高的温度下进行,并充分供氧,所以积炭引起失活的可能性较小,这可以从孔容数据和一些电镜照片中得到证实.     

无机阴离子对Fe-TiO2/SiO2复合光催化剂脱色染料的影响

考察了6种常见的无机阴离子对金属掺杂Fe-TiO2／SiO2复合光催化剂光催化降解酸性红B反应的影响，考察了导致催化剂失活的无机阴离子的最低浓度．结果发现H2PO4^-、HCO3^-具有较强的抑制作用，SO4^3-、I^-具有一定的抑制作用，而NO3^-、CI^-无明显影响实验结果证实无机离子对金属掺杂Fe-TiO2／SiO2活性的影响比TiO2／SiO2催化剂的影响明显要弱．对催化剂失活的机制也作了探讨。     

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters (DPFs). This work focused on the changes in the surface functional groups, carbon chemical state, and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600°C, 800°C, and 1000°C and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer (TGA-GC/MS). The surface functional groups and carbon chemical state were characterized using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The graphitization degree was evaluated by means of Raman spectroscopy (RS). The concentrations of aliphatic C–H, C–OH, C=O, and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature, while the sp²/sp³ hybridized ratio and graphitization degree enhance. These results provide comprehensive evidence of the decreased reactivity of soot samples. Among oxygenated functional groups, the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability. TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000°C thermal treatment of diesel soot.