Insight into the effect of phosphorus poisoning of Cu/zeolites with different framework towards NH3-SCR

Cu/zeolites were prepared to elucidate the effect of phosphorus poisoning on different zeolite framework structures for NH3-SCR. The results show that there are significant differences in phosphorus poisoning depending on the zeolite framework structure. The PO3−/PO43− species gradually decreased along with an increase in P2O5 in the following order: Cu/SSZ-13, Cu/ZSM-5, and Cu/BEA. One possible reason could be the increased pore size of these zeolites, which results in less steric hindrance for larger P2O5 species. P2O5 is suggested to enhance the redox ability of Cu ions, which results in an increase in low-temperature activity in NH3-SCR, whereas Cu ions were significantly poisoned by PO3−/PO43−, resulting in low-temperature deactivation. Furthermore, the effect of phosphorus poisoning on the structure of Cu/ZSM-5 was found to be much greater than that of Cu/BEA and Cu/SSZ-13, possibly due to phosphorus attacked the surface defects of the zeolite, causing local expansion and cracking

A deactivation mechanism study of phosphorus-poisoned diesel oxidation catalysts: Model and supplier catalysts

The effect of phosphorus poisoning on the catalytic behavior of diesel oxidation catalysts was investigated over model and supplier monolith catalysts, i.e., Pd-Pt/Al2O3. The results of ICP and XPS from the vapor-phase poisoning over model catalysts suggested that the temperature of phosphorus poisoning affects both the overall content of phosphorus and the dispersion of phosphorus (i.e., inlet/outlet and surface/bulk). Phosphorus oxide (P2O5), metaphosphate (PO3-), and phosphate (PO43-) were identified in the poisoned model and supplier catalysts. The distribution of these species on poisoned model catalysts was highly dependent on the poisoning temperature, i.e., a higher temperature resulted in a higher concentration of PO43-. The outlets of the monoliths contained more PO43- and less P2O5 than the inlets. Both active sites and surface OH groups on model and supplier catalysts were contaminated upon phosphorus poisoning. It is found that PO43- had a stronger influence on the active sites than P2O5. One significant finding in this study is that the vapor-phase phosphorus poisoning could be a practical and cost efficient approach to simulate an accelerated aging/poisoning process

Automated turnkey microcomb for low-noise microwave synthesis

Microresonator-based optical frequency comb (microcomb) has the potential to revolutionize the accuracy of frequency synthesizer in radar and communication applications. However, fundamental limit exists for low noise microcomb generation, especially in low size, weight, power and cost (SWaP-C) package. Here we resolve this limit, by the demonstration of an automated turnkey microcomb, operating close to its low quantum-limited phase noise, within a compact setup size of 85 mm * 90 mm * 25 mm. High quality factor fiber Fabry-Perot resonator (FFPR), with Q up to 4.0 * 10^9, is the key for both low quantum noise and pump noise limit, in the diode-pump case in a self-injection locking scheme. Low phase noise of -80 and -105 dBc/Hz at 100 Hz, -106 and -125 dBc/Hz at 1 kHz, -133 and -148 dBc/Hz at 10 kHz is achieved at 10.1 GHz and 1.7 GHz repetition frequencies, respectively. With the simultaneous automated turnkey, low-noise and direct-diode-pump capability, our microcomb is ready to be used as a low-noise frequency synthesizer with low SWaP-C and thus field deployability

Deactivation of a Vanadium-Based SCR Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation

We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NO(x)reduction performance in terms of standard, fast and NO2-rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NO(x)reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V4+/V(5+)ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V(4+)to V(5+)is partially hindered, blocking the redox cycle for parts of the active sites

Deactivation of a Pd/Pt Bimetallic Oxidation Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation

The reduction of anthropogenic greenhouse gas emissions is crucial to avoid further warming of the planet. We investigated how effluent gases from a biogas powered Euro VI heavy-duty engine impact the performance of a bimetallic (palladium and platinum) oxidation catalyst. Using synthetic gas mixtures, the oxidation of NO, CO, and CH4\ua0before and after exposure to biogas exhaust for 900 h was studied. The catalyst lost most of its activity for methane oxidation, and the activity loss was most severe for the inlet part of the aged catalyst. Here, a clear sintering of Pt and Pd was observed, and higher concentrations of catalyst poisons such as sulfur and phosphorus were detected. The sintering and poisoning resulted in less available active sites and hence lower activity for methane oxidation

SES: Sentiment Elicitation System for Social Media Data

Abstract—Social Media is becoming major and popu-lar technological platform that allows users discussing and sharing information. Information is generated and man-aged through either computer or mobile devices by one person and consumed by many other persons. Most of these user generated content are textual information, as So-cial Networks(Facebook, LinkedIn), Microblogging(Twitter), blogs(Blogspot, Wordpress). Looking for valuable nuggets of knowledge, such as capturing and summarizing sentiments from these huge amount of data could help users make informed decisions. In this paper, we develop a sentiment identification system called SES which implements three dif-ferent sentiment identification algorithms. We augment basic compositional semantic rules in the first algorithm. In the second algorithm, we think sentiment should not be simply classified as positive, negative, and objective but a continuous score to reflect sentiment degree. All word scores are calculated based on a large volume of customer reviews. Due to the special characteristics of social media texts, we propose a third algorithm which takes emoticons, negation word posi-tion, and domain-specific words into account. Furthermore, a machine learning model is employed on features derived from outputs of three algorithms. We conduct our experiments on user comments from Facebook and tweets from twitter. The results show that utilizing Random Forest will acquire a better accuracy than decision tree, neural network, and logistic regression. We also propose a flexible way to represent document sentiment based on sentiments of each sentence contained. SES is available online. Keywords-Social media, sentiment, rule, machine learning I

Fabrication of uniform Ag/TiO2 nanotube array structures with enhanced photoelectrochemical performance

In the current work, pulse current deposition has been used to prepare evenly distributed and uniformly sized Ag nanoparticles on a TiO2 nanotube array photoelectrode. The Ag particle size and loading were controlled by the pulse deposition time. The Ag/TiO2 nanotube arrays were characterized by SEM, TEM, XRD, XPS and UV-vis diffuse reflection absorption. The resulting electrode contained intimately coupled, three-dimensional Ag/TiO2 structures with greatly improved photocurrent generation and charge transfer compared to a two-dimensional random Ag particle layer deposited directly on top of the nanotube array by the regular photoinduction method. A model mechanism is proposed to illustrate the uniform Ag nanoparticle deposition via the new deposition technique developed in the current work that promotes the uniform distribution of the Ag particles whilst minimizing their deposition at tube entrances, thus effectively preventing the pores from becoming clogged.National Research Foundation of Singapore Government [MEWR 651/06/160]; National Nature Science Foundation of China [20773100, 20620130427]; National Basic Research Program of China (973 Program) [2007CB935603]; R&D of Fujian and Xiamen [2007H0031, 3502Z20073004