In situ regeneration of the Ni-based catalytic reformer of a 5 kW PEMFC system

The paper reports the results of on-site regeneration catalytic bed of the natural gas reformer in a 5 kW PEM fuel cell system. The Ni catalyst previously poisoned by sulphur from the available natural gas, could be re-activated by injection of pure water steam, following the method developed for industrial reformers using the same metal catalyst: this method was shown to be perfectly efficient, provided no natural gas was fed during the operation. Results of the tests conducted are presented and discussed in relation to published data on S-sorption on Ni surfaces.     

Axial characterization of catalytic activity in close-coupled lightoff and underfloor catalytic converters

A exhaust system consisting of a close-coupled Pd technology 32 in³ lightoff converter and Pt/Rh technology 170 in³ underfloor converter was vehicle-aged for 56000 miles on a vehicle equipped with a 3.8 l engine. Following this aging, the converters were taken off the vehicle and cut into 1″ thick sections along their axis and characterized for lightoff and warmed-up activity using a laboratory reactor to simulate vehicle exhaust. Each section was also analyzed for the quantity of oil additive poisons (phosphorus and zinc) deposited. Following this initial characterization, the phosphorus and zinc deposits were removed, and the sections were characterized again for lightoff and warmed-up activity. This procedure was used to qualitatively determine the relative contribution of oil additive poisoning and thermal sintering to the total activity deterioration as a function of axial position in the catalyst monoliths.

Analysis of the lightoff converter as taken from the vehicle showed a dramatic axial gradient in the lean and stoichiometric lightoff and warmed-up (600°C) performance for HC, CO and NO_x, with most of the deterioration having taken place in the forward-most 1″ section of the converter, which was consistent with the gradient in the deposition of phosphorus (P) and zinc (Zn) in this converter. Comparison of these data sets with those obtained after removal of the P and Zn poisons indicates that most of the total deterioration of lean HC and CO activity can be attributed to P and Zn poisoning of the forwardmost 1″ section. When tested under stoichiometric conditions, most of the deterioration of HC activity is attributable to P and Zn poisoning, while most of the deterioration of CO and NO_x activity is attributable to thermal deterioration. A similar activity and poison deposition gradient was detected in the underfloor converter, but to a smaller extent.     

苯甲酸加氢催化剂Pd/C抗中毒方法研究及应用

研究了苯甲酸加氢过程中Pd/C催化剂的失活原因，针对CO引起Pd/C活性降低，开发了SRNA－5助催化剂，有效消除了反应中生成的CO对Pd/C催化剂活性的影响。并在石家庄化纤公司完成了工业试验，工业试验表明，在不改变原工业流程的基础上，通过向苯甲酸加氢工业装置中加入SRNA－5助剂，有效提高Pd/C催化剂活性，该厂每年减少催化剂直接费用1500万元。     

Regeneration of S-poisoned Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts for the combustion of methane

This work investigates the regeneration of S-poisoned Pd/Al₂O₃ and Pd/CeO₂/Al₂O₃ catalysts under different CH₄ containing atmospheres. Under lean combustion conditions in the presence of excess O₂, partial regeneration took place for both systems only above 750 °C after decomposition of stable sulphate species adsorbed on the support. Under alternate lean combustion/CH₄-reducing pulse regeneration is markedly anticipated down to 550–600 °C. Experiments evidenced an effective role of ceria in preventing PdO from sulphation and in promoting regeneration via sulphates decomposition under reducing conditions.     

制氢装置转化催化剂失活原因分析及对策

中石化西安分公司制氢装置转化催化剂在短期生产运行过程中,因催化剂积碳导致转化炉管表面出现大面积花斑,近半数炉管出现红管,炉管差压增大,转化出口甲烷含量超标,芳烃穿透.对催化剂失活原因进行细致分析后表明:装置开停车频繁;转化催化剂多次积碳-烧碳使催化剂表面剥蚀破碎、跑损严重为主要原因.针对失活原因制定了相应对策.     

Structural changes in air aged and poisoned diesel catalysts

Laboratory-scale ageing and poisoning procedures were performed on selected diesel catalysts. The results showed that phosphorus poisoning together with high temperature ageing has a strong effect on the catalytic activity and microstructure of platinum containing catalysts. Phosphorus poisoning contaminated the catalysts resulting in phosphate formation, e.g. CePO₄ and AlPO₄. Poisoning and air ageing increased platinum particle-size and washcoat grain-size.     

PORE-MOUTH POISONING OF NON-UNIFORM CATALYSTS

Impurity poisoning of a catalyst particle having a non-uniform activity distribution is analyzed. Equations that relate the position of the poison-front with time for different activity profiles are derived. It is shown that the effect of the activity distribution on the poisoning rate is apparent in the case of intraparticle-diffusion control. The performance of a non-uniform bifunctional catalyst in such conditions is also studied.     

Complete Oxidation of Methane at Low Temperature over Pt Catalysts Supported on High Surface Area SnO2

The catalytic activity of Pt catalysts supported on high surface area tin(IV) oxide in the complete oxidation of CH₄ traces under lean conditions at low temperature was studied in the absence and in the presence of water (10 vol.%) or H₂S (100 vol.ppm). Their catalytic properties were compared to those of Pd/Al₂O₃ and Pt/Al₂O₃. In the absence of H₂S in the feed, Pt/SnO₂appears as a very promising catalyst for CH₄ oxidation, being even significantly more active under wet conditions than the best reference catalyst, Pd/Al₂O₃. Catalysts steamed-aged at 873 K were also studied in order to simulate long term ageing in real lean-burn NGV exhaust conditions. To this respect, Pt/SnO₂ is slightly less resistant than Pd/Al₂O₃. In the presence of H₂S, Pt/SnO₂catalysts are rapidly and almost completely poisoned, comparably to Pd/Al₂O₃and the catalytic activity is hardly restored upon oxidising treatment below 773 K. A synergetic effect between Pt and specific surface SnO₂sites active in CH₄oxidation is proposed to explain the superior catalytic behaviour of Pt/SnO₂.     

基于细胞阻抗传感器的腹泻性毒素检测系统设计与实现

针对海洋水产品腹泻性毒素检测问题,设计了一种新型的基于细胞阻抗传感器(ECIS)的毒素快速检测分析系统。相对于传统的毒素检测方法,该系统具有操作简便,高一致性和高通量等特点。介绍了系统的硬件设计和软件设计,通过对系统整体性能测试以及使用神经母细胞瘤细胞(Neuro-2a)对腹泻性贝毒(DSP)大田软海绵酸(OA)进行毒性检测实验,用以验证系统平台的可行性。实验结果表明,基于细胞传感器的海洋水产品腹泻性毒性检测系统具备快速,长期,无损和高通量测量的特点,为腹泻性毒素检测提供了新的平台。     

氨合成塔催化剂中毒原因分析及处理

介绍合成塔催化剂因合成气压缩机段间水冷器泄漏而致水中毒的情况，分析水中毒的原因及处理过程，介绍了段间水冷器泄漏情况下装置的运行方案。