铂、钯蜂窝催化剂高温老化对甲醇深度氧化的影响

本研究对铂、钯蜂窝催化剂及分别添加助化剂CeO_2或WO_3,并于500℃、700℃、900℃或1100℃下经受热老化4h后,考察催化剂比表面、晶相结构及其对甲醇深度氧化活性、产物分布及反应动力学网络变化的情况。实验证明,添加CeO_2后,降低了铂催化剂的耐高温性能,但对钯催化剂无明显影响。添加WO_3,降低了钯催化剂对甲醇的氧化活性。经X-线衍射分析证明,在1100℃高温下,WO_3与堇青石载体中的氧化镁和氧化钙发生强相互作用,生成了相应的钨酸盐。甲醇氧化反应动力学研究表明,甲醇在新鲜和高温热老化的铂催化剂上,反应动力学网络表示式是有区别的。     

Effect of phosphate on heterogeneous Fenton oxidation of catechol by nano-Fe3O4: Inhibitor or stabilizer?

The effect of phosphate on adsorption and oxidation of catechol, 1,2-dihydroxybenzene, in a heterogeneous Fenton system was investigated. In situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) was used to monitor the surface speciation at the nano-Fe₃O₄ catalyst surface. The presence of phosphate decreased the removal rate of catechol and the abatement of dissolved organic compounds, as well as the decomposition of H₂O₂. This effect of phosphate was mainly due to its strong reaction with surface sites on the iron oxide catalyst. At neutral and acid pH, phosphate could displace the adsorbed catechol from the surface of catalyst and also could compete for surface sites with H₂O₂. In situ IR spectra indicated the formation of iron phosphate precipitation at the catalyst surface. The iron phosphate surface species may affect the amount of iron atoms taking part in the catalytic decomposition of H₂O₂ and formation of hydroxyl radicals, and inhibit the catalytic ability of Fe₃O₄ catalyst. Therefore, phosphate ions worked as stabilizer and inhibitor in a heterogeneous Fenton reaction at the same time, in effect leading to an increase in oxidation efficiency in this study. However, before use of phosphate as pH buffer or H₂O₂ stabilizer in a heterogeneous Fenton system, the possible inhibitory effect of phosphate on the actual removal of organic pollutants should be fully considered.     

基于CWPO法处理垃圾渗滤液的CuO/TiO_2催化剂的制备及其性能研究

采用过量浸渍的方法制备CuO/TiO_2催化剂,以垃圾转运站的渗滤液为对象评价催化剂的活性及稳定性。采用XRD、SEM、BET对催化剂进行了表征,并利用催化湿式氧化法处理垃圾渗滤液。考察了制备过程中煅烧温度、煅烧时间、负载比以及浸渍液浓度对垃圾渗滤液处理效果的影响。结果表明:煅烧温度为300℃,煅烧时间为2 h,负载比为16.5%,浸渍液浓度为0.8 mol/L条件下,渗滤液COD去除率达到78.6%,脱色率达到88.2%。     

SCR脱硝机组空气预热器堵塞治理建议

燃煤机组安装SCR脱硝装置后,空气预热器堵塞成为普遍现象,严重影响机组的安全性、经济性。通过对空气预热器堵塞物成分分析,提出治理空气预热器堵塞技术路线,结合实际运行中出现的问题,探寻SCR脱硝机组氨逃逸率高、SO_3浓度高、排烟温度低的原因,并且分析这些因素对空气预热器堵塞程度的影响,建议从保持催化剂活性,确保NO_x浓度,氨逃逸率均匀分布,防止氨过喷,降低入炉煤含硫量,提高锅炉排烟温度等方面,综合治理空气预热器堵塞,并提出详细的建议。     

Effects of alkali promoters on the textural and catalytic properties of mesoporous Fe–Al–Cu catalysts for water gas shift reaction

Mesoporous Fe₂O₃–Al₂O₃–CuO catalysts promoted with alkali oxides were synthesized and used in water gas shift reaction (WGSR) at high temperatures for hydrogen purification. These chromium-free catalysts were characterized using nitrogen adsorption/desorption, hydrogen temperature programmed reduction, X-ray diffraction (XRD), and transmission electron microscopy techniques. The synthesized catalysts with narrow single-modal pore size distribution in mesopore region possessed high specific surface area. The catalytic results revealed that except Cs, the addition of other alkali promoters declined the catalytic activity. However, all catalysts showed higher catalytic performance than the conventional commercial catalyst. The results showed an optimum content of Cs promoter (3 wt.%) for the promoted Fe–Al–Cu catalyst (3 wt.% Cs-FAC), which exhibited the highest activity in WGSR at high temperature.     

SO2/SO3对选择性催化还原烟气脱硝的影响研究

研究表明，燃料燃烧过程中不同的SO2/SO3转化率对选择性催化还原（ Selective Catalytic Reduction，SCR）烟气脱硝的最低运行温度影响大，温度变化幅度为10~15℃。对燃烧高硫煤锅炉的SCR烟气脱硝，应控制更低的SO2/SO3转化率；对燃烧低硫煤锅炉的SCR烟气脱硝，通过适当提高SO2/SO3转化率，最大催化剂用量可减少一半、烟气阻力降低一半，可大幅降低SCR烟气脱硝建设成本和运行成本。     

Low-temperature VOCs oxidation performance of Pt/zeolites catalysts with hierarchical pore structure

Different zeolites supported Pt catalysts with micro-mesoporous structure were prepared by organic base tetrapropylammonium hydroxide (TPAOH) treatment and their catalytic oxidation activity for various volatile organic compounds (VOCs) were evaluated. The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal. The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts, while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containing N and O heteroatoms. In addition, it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst. This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.     

Electrochemical removal of ammonium nitrogen in high efficiency and N2 selectivity using non-noble single-atomic iron catalyst

Ammonia nitrogen (NH₄⁺-N) is a ubiquitous environmental pollutant, especially in offshore aquaculture systems. Electrochemical oxidation is very promising to remove NH₄⁺-N, but suffers from the use of precious metals anodes. In this work, a robust and cheap electrocatalyst, iron single-atoms distributed in nitrogen-doped carbon (Fe-SAs/N-C), was developed for electrochemical removal of NH₄⁺-N from in wastewater containing chloride. The Fe-SAs/N-C catalyst exhibited superior activity than that of iron nanoparticles loaded carbon (Fe-NPs/N-C), unmodified carbon and conventional Ti/IrO₂-TiO₂-RuO₂ electrodes. And high removal efficiency (> 99%) could be achieved as well as high N₂ selectivity (99.5%) at low current density. Further experiments and density functional theory (DFT) calculations demonstrated the indispensable role of single-atom iron in the promoted generation of chloride derived species for efficient removal of NH₄⁺-N. This study provides promising inexpensive catalysts for NH₄⁺-N removal in aquaculture wastewater.     

Gas-phase thermal explosions in catalytic direct oxidation of alkenes

The metal-based catalytic oxidation of alkenes to the corresponding epoxides is playing a significant role in the modern chemical industry. Nevertheless, these key processes are still lacking proper understanding with respect to the gas-phase runaway behaviour (thermal explosion) and to the hot spot formation on the catalytic surface, under the typical process conditions.This work aims to enlighten these aspects by considering either the catalytic or the gas-phase chemistry for the development of reactor operative diagrams, in order to define the best-operating conditions with respect to the selectivity, the productivity, and the process safety aspects.The proposed methodology has been applied to the oxidation of ethylene and propylene for the direct oxidation process by pure oxygen, considering a detailed kinetic model accounting for the homogeneous reactions, coupled with the heterogeneous catalytic mechanisms.Sensitivity and reaction path analyses were performed to individuate the ruling species and reactions determining the transition to runaway conditions.     

烟气脱硫石膏催化还原为硫化钙的研究

采用Fe-Ni复合催化剂,在温度650℃条件下即可将烟气脱硫石膏催化还原为硫化钙,还原率达95%以上。研究了反应温度、催化剂加入量及还原气体含量因素对还原反应的影响。