Promotional effect of colloidal alumina on the activity of the In/HZSM-5 catalyst for the selective reduction of NO with methane

Colloidal alumina was used to improve the activity of an In/HZSM-5 catalyst for the selective reduction of NO with CH4 in the excess of oxygen. Compared with In/HZSM-5, the In/HZSM-5/Al2O3 catalyst showed higher activity in a wide range of reaction temperatures. It is visualized that a synergetic effect between In/HZSM-5 and Al2O3 enhances the conversion of NOx. The addition of Al2O3 improved the conversion of NO to NO2 and facilitated the activation of methane. An In/HZSM-5/Al2O3 pre-treated with steam for 15 h at 700 degreesC still showed a high activity for the removal of NOx with methane, while an In/HZSM-5 similarly pre-treated with steam showed a lower activity than the fresh sample. The activity of the In/HZSM-5/Al2O3 catalyst could be restored completely after water vapor was removed from the feed gas. Furthermore, it was found that the In/HZSM-5/Al2O3 remained fairly active under high GHSV and O-2 concentration conditions. It was also interesting to find that an increase in NO content could enhance the conversion of methane, and this illustrates that the existence of NO is beneficial for the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

Unique properties of Ir/ZSM-5 catalyst for NO reduction with CO in the presence of excess oxygen

The reduction of NO with CO in the presence of excess oxygen was investigated over different noble metal catalysts for probing the relationship between catalytic properties and adsorption behaviors. Among the four precious metal catalysts investigated, Ir/ZSM-5 was found to be the only active one for NO reduction with CO under lean conditions. With the decreasing of the Ir content, higher NO conversion and CO selectivity was obtained. Temperature-programmed reaction (TPR) studies of NO/H-2/O-2 and NO/CO/O-2 showed that the Pt/ZSM-5 was active when H-2 was used as the reductant, whereas, the Ir/ZSM-5 was active when CO was the reducing agent. This difference is due to the different mechanisms of the two reactions. Temperature-programmed desorption (TPD) of NO, CO and O-2 showed that NO could dissociate more easily over the Ir/ZSM-5 than on the Pt/ZSM-5, while the oxidation of CO by O-2 proceeded more rapidly on the Pt/ZSM-5 than on the Ir/ZSM-5. The presence of excess O-2 inhibited drastically the dissociation of NO, which is considered as the key step for the NO-CO reaction. The high dissociation rate of NO over the Ir/ZSM-5 is visualized as the key factor for its superior high activity in NO reduction with CO under lean conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

Effect of addition of Zn on the catalytic activity of a Co/HZSM-5 catalyst for the SCR of NOx with CH4

The selective catalytic reduction (SCR) of NOx by methane in the presence of excess oxygen was studied on a Zn-Co/HZSM-5 catalyst. It was found that the addition of Zn could improve effectively the selectivity of methane towards NOx reduction. When prepared by a coimpregnation method, the Zn-Co/HZSM-5 catalyst showed much higher catalytic activity than the two catalysts of a Zn/Co/HZSM-5 and Co/Zn/HZSM-5 prepared by the successive impregnation method. It is considered that there exists a cooperative effect among the Zn, Co and zeolite, which enhances the reduction of NO to NO2 reaction and the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

Direct decomposition of NO by microwave heating over Fe/NaZSM-5

Catalytic decomposition of NO was studied over Fe/NaZSM-5 catalyst. Novel results were observed with the microwave heating mode. The conversion of NO to N-2 increased remarkably with the increasing of Fe loading. The effects of a series of reaction parameters, including reaction temperature, O-2 concentration, NO concentration, gas flow rate and H2O addition, on the productivity of N-2 have been investigated. It is shown that the catalyst exhibited good endurance to excess O-2 in the microwave heating mode. Under all reaction conditions, NO converted predominantly to N-2. The highest conversion of NO to N-2 was up to 70%. (C) 2002 Elsevier Science B.V. All rights reserved.

New titanium complexes with two beta-enaminoketonato chelate ligands: Syntheses, structures, and olefin polymerization activities

New titanium complexes with two nonsymmetric bidentate beta-enaminoketonato (N,O) ligands (4a-e), [(Ph)NC(R-2)C(H)C(R-1)O](2)TiCl2, have been synthesized. X-ray crystal structure reveals that complex 4a has a C-2-symmetric conformation with a distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4a-e are active catalysts for ethylene polymerization at room temperature, producing high molecular weight polyethylenes bearing linear structures. The 4a,b/MMAO catalyst systems exhibit the characteristics of a quasi-living polymerization of ethylene, producing polyethylenes with narrow molecular weight distributions. Moreover, the 4a-d/MMAO catalyst systems are also capable of promoting the quasi-living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight alternating copolymers with narrow molecular weight distributions. The quasi-living nature of the catalysts allows the synthesis of new A-B polyethylene-block-poly(ethylene-conorbornene) diblock copolymer.

Size-affected crystallization of trans-1,4-polybutadiene

By using different catalyst systems, two trans-1,4-polybutadiene (TPBD) samples with different tr trans-content and molecular weight were synthesized. The phase transition of two samples from monoclinic form to hexagonal phase was revealed by differential calorimeter scanning and X-ray, respectively. The small-angle X-ray scattering measurements showed the remarkable discrepancy of phase transition and melting point between the two samples was attributed to the different lamellar thickness of crystals: The crystals with different crystalline morphology and lamellar thickness were developed by casting different concentration TPBD solutions. Transmission electron microscopy morphology observations proved that annealing the specimen at the temperature above the phase transition point for different times resulted in the different lamellae thickening of monoclinic form. It means that annealing the TPBD in its hexagonal phase will also slightly favor the increase of both the phase transition temperature and melting point of hexagonal phase. (C) 2001 Elsevier Science Ltd. All rights reserved.

Comparative study of Nickel-based perovskite-like mixed oxide catalysts for direct decomposition of NO

The mixed oxides LaNiO3, La0.1Sr0.9NiO3, La2NiO4 and LaSrNiO4 were prepared and used as catalysts for the direct decomposition of NO. The catalysts were characterized by means of XRD, XPS, O-2-TPD, NO-TPD and chemical analysis. By comparing the physico-chemical properties and catalytic activity for NO decomposition, a conclusion could be drawn as follows. The direct decomposition of NO over perovskite and related mixed oxide catalysts follows a redox mechanism. The lower valent metal ions Ni2+ and disordered oxygen vacancies seem to be the active sites in the redox process. The oxygen vacancy plays an important role favorable for the adsorption and activation of NO molecules on one hand and on the other hand for increasing the mobility of lattice oxygen which is beneficial to the reproduction of active sites. The presence of oxygen vacancies is one of the indispensable factors to give the mixed oxides a steady activity for NO decomposition.

聚硅氯化铝铁（PSAFC）絮凝剂的形态分析

通过对聚硅氯化铝铁水解共聚物的合成制备及水解共聚过程PH变化的研究，对铝铁共物的化学形态、二氧化硅的加入和碱化度B对铝铁共聚物的影响进行了研究和讨论；并应用Ferron配合逐时比色法对聚合物中铁的形态进行了表征，为深入研究聚硅氯化铝铁铁奠定了理论基础。

Enhanced activity of an In-Fe2O3/H-ZSM-5 catalyst for NO reduction with methane

Selective reduction of NO by CH4 on an In-Fe2O3/H-ZSM-5 catalyst was investigated in the presence of excess oxygen. Compared with In/H-ZSM-5, the In-Fe2O3/H-ZSM-5 catalyst with high Fe2O3 contents showed higher activity in a wide range of reaction temperatures. It was found that the addition of Fe2O3 yielded a promotion effect on CH4 activation. The influence of water vapor on NO conversion was also investigated. The activity of the In/H-ZSM-5 catalyst has been found to be strongly inhibited by water vapor, while the In-Fe2O3/H-ZSM-5 catalyst remained fairly active in the presence of 3.3% steam. (C) 2000 Elsevier Science B.V. All rights reserved.

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

The catalytic performance of silver-modified ZSM-5 catalysts in the selectively catalytic reduction (SCR) of NOx with methane was investigated. NO was selectively reduced by CH4 to N-2 in the presence of excess O-2, and the catalytic activity depended on both the activation of CH4 and the adsorption properties of NOx. Silver incorporated in ZSM-5 zeolite activated CH4 at low temperatures and lowered the "light-off" temperature for the CH4-SCR of NOx. Temperature-programmed (TP) spectroscopy studies depicted that surface nitrosyl species directly decomposed to N-2 in the absence of O-2. CH4 could not effectively reduce surface nitrosyl species, but might facilitate the direct decomposition of NO through the removal of surface oxygen. Surface nitrates were formed in NO and O-2 coexisting system and could be effectively reduced by CR4 to nitrogen. The priority of surface nitrates to O-2 in the reaction with CH4 clearly demonstrated that CH4 selectively and preferentially reduced the surface nitrate species to N-2 in the excess of oxygen. (C) 2002 Elsevier Science B.V. All rights reserved.

Anais.

Aspectos economicos da criacao de aves em ambientes climatizados; Aspectos economicos e viabilidade da criacao de frangos nos sistemas convencionais e automatizado; Gerenciamento do ambiente na avicultura; Sistemas de climatizacao de instalacoes avicolas; Criterios para o planejameto de instalacoes avicolas para aves de postura; Avancos na area de equipamentos para postura; Sistemas de aquecimento para aves; Misting systems for poultry - dimension and applications; Sistemas de ventilacao natural e artificial na criacao de aves; Planning broiler housing for environmental control systems; Luz: criterios para o dimensionamento de programas em aviarios de corte e alternativas para a intensidade, cor e distribuicao; Ventilation to control poultry house air quality; A interacao ambiente X sanidade; Management, treatment, and utilization of poultry litter with respect to environmental protection.

TCP-friendly SIMD Congestion Control and Its Convergence Behavior

The increased diversity of Internet application requirements has spurred recent interests in flexible congestion control mechanisms. Window-based congestion control schemes use increase rules to probe available bandwidth, and decrease rules to back off when congestion is detected. The parameterization of these control rules is done so as to ensure that the resulting protocol is TCP-friendly in terms of the relationship between throughput and packet loss rate. In this paper, we propose a novel window-based congestion control algorithm called SIMD (Square-Increase/Multiplicative-Decrease). Contrary to previous memory-less controls, SIMD utilizes history information in its control rules. It uses multiplicative decrease but the increase in window size is in proportion to the square of the time elapsed since the detection of the last loss event. Thus, SIMD can efficiently probe available bandwidth. Nevertheless, SIMD is TCP-friendly as well as TCP-compatible under RED, and it has much better convergence behavior than TCP-friendly AIMD and binomial algorithms proposed recently.

Electronic aids to daily living: be able to do what you want

Purpose. This study explores the experiences of Irish people with high cervical spinal cord injuries living with electronic aids to daily living (EADL) and the meaning attributed to such systems in the context of participation in everyday life. Method. Qualitative methodology using a phenomenological approach was used to explore the phenomenon of living with EADL. Data were collected using four focus groups of users and nonusers of EADL (n = 15). All participants had high cervical spinal cord injuries (C3-5). Groups were video recorded, transcribed verbatim and analysed using descriptive phenomenological analysis. Findings. Findings revealed key elements of the meaning of living with EADL. Two key themes, time alone and changed relationships are described. These contribute to the super ordinate theme of autonomy. Findings suggest that participants perceived improvements in both anticipated and actual lived experiences with EADL. Themes are interrelated and together represent a summary of the experience of living with environmental controls. The themes described are similar to those found in other spinal injury studies relating to quality of life. Conclusions. Findings highlight differences in life experiences for those with and without EADL and provides motivation to address this difference. Such insights are valuable for both users and providers of EADL.