Hydrophobicity and catalytic properties of Ti-MFI zeolites synthesized by microwave and conventional heating

Ti-incorporated MFI zeolite (Ti-MFI-MW) has been synthesized with microwave heating. Their physicochemical properties such as surface hydrophobicity, and adsorption and catalytic properties have been compared with those of Ti-incorporated MFI zeolite (Ti-MFI-CH) prepared by conventional hydrothermal method. Competitive adsorption measurements with toluene and water revealed that the hydrophobicity index of Ti-MFI-MW (8.0) is higher than that of Ti-MFI-CH (6.2). IR spectra showed that Ti-MFI-MW also has a lower content of surface hydroxyl groups and adsorbs a larger amount of 1-hexene than Ti-MFI-CH. These results pointed out that Ti-MFI-MW is more hydrophobic than Ti-MFI-CH. Epoxidation reactions of 1-hexene and styrene with hydrogen peroxide have been conducted to investigate catalytic properties of the Ti-MFI zeolites according to the synthesis method. The conversions and epoxide selectivities over Ti-MFI-MW are higher than those over Ti-MFI-CH due to the enhanced surface hydrophobicity.     

Selective crystallization of CoAPO-34 and VAPO-5 molecular sieves under microwave irradiation in an alkaline or neutral condition

Syntheses of cobalt- and vanadium-incorporated aluminophosphate molecular sieves (CoAPO and VAPO) with AFI and CHA structures have been studied using an alkaline or neutral gel under microwave irradiation and conventional hydrothermal heating. Microwave synthesis gives rise to the selective crystallization of CoAPO-34 with a CHA structure and VAPO-5 with an AFI structure, while the conventional hydrothermal crystallization brings CoAPO-5 and VAPO-34 through the gradual transformation of CoAPO-34 and VAPO-5, respectively, as the crystallization time increases. These results reveal that the relative stabilities of metal-incorporated aluminophosphate (MeAPO) molecular sieves between AFI and CHA structures depend on the type of incorporated metal ions. This work also suggests that microwave syntheses of MeAPO molecular sieves preferentially induce a kinetically favorable MeAPO phase in a short period of crystallization time. The synthesis of VAPO-5 in an alkaline condition is for the first time reported in this work.     

Oligomerization of isobutene over aluminum chloride-loaded USY zeolite catalysts

Oligomerization of isobutene has been investigated over AlCl₃-loaded USY zeolite catalysts in order to produce triisobutenes or remove/separate isobutene from C₄ streams. Stable isobutene conversion and high selectivity for trimers and tetramers were attained over the modified zeolite with high ratio of Lewis acid site-to-Brønsted acid site, suggesting that a potential trimerization catalyst can be obtained easily by loading a Lewis acid into an acidic zeolite catalyst. This catalyst can be facially produced by physical mixing and can be easily restored its activity after deactivation by simple calcinations.     

Seismic response of reactor vessel internals for Korean standard nuclear power plant

This paper presents the development of seismic design criteria for the reactor vessel internals as a part of the standardization programme for the nuclear power plant in Korea. The seismic design loads of the reactor vessel internals are calculated using the reference input motions of reactor vessels taken from Yonggwang nuclear power plant units 3 and 4 which are being constructed in Korea. An overview of analysis related to the basic parameters and methodologies is presented. Also, the response of internal components to the reactor vessel motions is carefully investigated.     

Bayesian contextual classification based on modified M-estimatesand Markov random fields

A Bayesian contextual classification scheme is presented in connection with modified M-estimates and a discrete Markov random field model. The spatial dependence of adjacent class labels is characterized based on local transition probabilities in order to use contextual information. Due to the computational load required to estimate class labels in the final stage of optimization and the need to acquire robust spectral attributes derived from the training samples, modified M-estimates are implemented to characterize the joint class-conditional distribution. The experimental results show that the suggested scheme outperforms conventional noncontextual classifiers as well as contextual classifiers which are based on least squares estimates or other spatial interaction models     

Tungsten Nitride,Well‐Dispersed on Porous Carbon: Remarkable Catalyst,Produced without Addition of Ammonia,for the Oxidative Desulfurization of Liquid Fuel

Polyanilines (pANIs), loaded with phosphotungstic acid (PTA), are pyrolyzed to get WO₃ or W₂N (≈6 and ≈7 nm, respectively), which is well‐dispersed on pANI‐derived porous carbons (pDCs). Depending on the pyrolysis temperature, WO₃/pDC, W₂N/pDC, or W₂N‐W/pDCs could be obtained selectively. pANI acts as both the precursor of pDC and the nitrogen source for the nitridation of WO₃ into W₂N during the pyrolysis. Importantly, W₂N could be obtained from the pyrolysis without ammonia feeding. The obtained W₂N/pDC is applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of liquid fuel for the first time, and the results are compared with WO₃/pDC and WO₃/ZrO₂. The W₂N/pDC is very efficient in ODS with remarkable performance compared with WO₃/pDC or WO₃/ZrO₂, which is applied as a representative ODS catalyst. For example, W₂N/pDC shows around 3.4 and 2.7 times of kinetic constant and turnover frequency (based on 5 min of reaction), respectively, compared to that of WO₃/ZrO₂. Moreover, the catalysts could be regenerated in a facile way. Therefore, W₂N/pDC could be produced facilely from pyrolysis (without ammonia feeding) of PTA/pANI, and W₂N, well‐dispersed on pDC, can be suggested as a very efficient oxidation catalyst for the desulfurization of liquid fuel.     

Recombinant human interleukin-11 in experimental Pseudomonas aeruginosa sepsis in immunocompromised animals

The therapeutic potential of recombinant human interleukin-11 (rhIL-11) was tested in a neutropenic rat model that mimics the clinical consequences of myelosuppressive chemotherapy complicated by Pseudomonas aeruginosa sepsis. rhIL-11-treated animals (150 micrograms/kg intravenously every 24 h for 3 days) had reduced endotoxin levels (P < .05) and less pulmonary edema fluid (P < .001) and were protected (P < .01) against thinning and necrosis of the intestinal mucosa compared with the control group. The survival rate in rhIL-11-treated animals was 40% (19/47), whereas it was 0 (0 of 19) in the control group (P < .01). The addition of ciprofloxacin (10 mg/kg every 12 h) resulted in a survival rate of 9 (60%) of 15, while the combination of rhIL-11 and ciprofloxacin resulted in 100% survival (15/15; P < .05). These results indicate that rhIL-11 supports mucous membrane integrity of the alimentary tract and decreases the systemic inflammatory response to experimental gram-negative infection in immunocompromised animals.     

Adoption of new online services in the presence of network externalities and complementarities

A typical online user utilizes multiple services in the same service category concurrently due to the fact that many online service markets are characterized by the coexistence of multiple services offering complementary features. Along with an inherent network externality feature, this complementary nature among competing online services complicates predictions of adoption patterns in these markets. This paper extends the adoption function model of Arthur [W.B. Arthur, Competing technologies, increasing returns, and lock-in by historical events, The Economic Journal 99 (1989) 116–131] and applies it to the online service market in an attempt to explain various cases of adoption behavior. The proposed model predicts that there exists a first-mover’s advantage in this market. Specifically, when network externality is large enough, the follower is confined to a low market share, even though it provides the same level of service as that provided by the leader. However, this first-mover’s advantage can be overcome in cases where perturbations are caused by the heterogeneity of consumers or by service value uncertainty. In addition, a two-step punctuated equilibrium may exist: under specific conditions, market share distribution may be stable for a while at certain levels and then move into actual equilibrium.