Effects of water temperature on swimming performance of <em>Siniperca knerii</em> Garman under the Yuanshui River cascade development

We examined the swimming parameters and oxygen consumption rate at four temperature levels (15，20，25 and 30°C) of Siniperca knerii Garman (11.81 ±2.21 cm, 26.4 ± 6.28g) from Yuanshui River for 30 days to analyze the ecological adaptability of the typical fish and the conservation of fishery resources from the Dongting Lake water system. Their relationship was also analyzed, and the results showed an approximately linear increasing trend of the fish's critical swimming speed and preferred swimming speed with the change of temperature (PSiniperca knerii Garman. The changes were due to physiological and biochemical regulation with temperature and environmental changes. This experiment provided essential data support for the adaptive mechanism of sports physiology and ecology of typical fishes in the Yuanshui River

Effect of Catalyst Preparation on Hydroisomerization of n-Heptane over Pt/Silicalite-1

The isomerization of n-heptane was comparatively investigated over Pt catalysts prepared by deposition (Pt/S-1-DP) and impregnation precipitation (Pt/S-1-IMP) method with a low loading, separately. It was found that Pt/S-1-DP catalyst produced a much higher catalytic conversion compared with the counterpart catalyst prepared by impregnation. Combined with various characterization techniques, the better performance over Pt/S-1-DP was attributed to not only the well improved dispersity and the smaller size of Pt particles but also the faster transfer of reactive species between Pt sites and acid sites. The activity could be improved by increasing the reduction temperature. Moreover, the (de)hydrogenation of Pt over Pt/S-1 catalyst was verified by in situ infrared spectroscopy through H/D isotope exchange experiment

La-Stabilized, Single-Atom Ir/AC Catalyst for Heterogeneous Methanol Carbonylation to Methyl Acetate

Although homogeneous methanol carbonylation is industrialized to produce acetic acid, it still suffers from the problems of difficult separation and metal leaching. Here, we report a heterogeneous single atom Ir-La/AC catalyst to produce methyl acetate in a fixed-bed reactor. A high TOF of 2200h(-1) and high selectivity over 90% for methyl acetate with space time yield of 8200 g/(kg(cat) h) were achieved over the Ir-La/AC catalyst. Furthermore, the effects of reaction temperature, partial pressure of CO and CH3OH, weight ratio of CH3I/CH3OH, total LHSV as well as the role of La on the catalytic performance of Ir/AC were tested in this paper. In addition, we proposed a reasonable mechanism for heterogeneous methanol carbonylation over La stabilized single atom Ir/AC catalyst. Our work provides a reference for the further scale-up of the process and a stable, supported, single-atom system as a substitution for other homogeneous catalyst

Promotional effects of Cr and Fe on Rh/SiO2 catalyst for the preparation of ethanol from CO hydrogenation

A series of Cr and Fe promoted Rh-based silica supported catalysts were prepared by an incipient co-impregnation method. The performance of the catalysts was investigated by the hydrogenation of carbon monoxide to ethanol. The catalysts were characterized by N-2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, H-2 temperature-programmed reduction, temperature programmed surface reaction, and Fourier transform infrared spectroscopy. The results revealed that addition of 0.2-0.4 wt% Cr to Rh/SiO2 increased its activity significantly. However, further addition of 0.1-0.2 wt% Fe lowered CO conversion slightly, while the selectivity towards ethanol was enhanced significantly. Therefore, high catalytic activity and selectivity toward ethanol were achieved by simultaneous introduction of 0.4 wt% Cr and 0.2 wt% Fe to Rh/SiO2. This may be due to improved dispersion of Rh particles, moderate ability to dissociate CO molecules, and high ratio of Rh+ sites to Rh-0 sites

A highly efficient single site Rh-POL-PPh3 catalyst for heterogeneous methanol carbonylation

In Contrast to the Monsanto homogeneous system, the Rh heterogeneous methanol carbonylation universally displays lower activity and stability. Here, a single site catalyst Rh-POL-PPh3 was successfully prepared by impregnation of the Rh-2(CO)(4)C-12 dichloromethane solution, and applied to heterogeneous methanol carbonylation in a continuous fixed-bed reactor for the first time. Due to single site Rh species and the electron-donating effect of P ligands and the strong multicoordination bonds between Rh and P, the Rh-POL-PPh3 catalyst exhibited a little higher TOF of 1550 h(-1) than that of optimized Monsanto process and maintained relatively stable activity for near 180 h under 2.5 MPa, 195 degrees C. Thus, POL-PPh3 not only acts as a stable support but also a promotion of methanol carbonylation process. (C) 2017 Elsevier B.V. All rights reserved

A framework of synthesizing tutoring conversation capability with web-based distance education courseware

Whereas existing learning environments on the Web lack high level interactivity, we have developed a human tutor-like tutorial conversation system for the Web that enhances educational courseware through mixed-initiative dialog with natural language processing. The conversational tutoring agent is composed of an animated tutor, a Latent Semantic Analysis (LSA) module, a database with curriculum scripts, and a dialog manager. As in the case of human tutors, the meaning of learner\u27s contributions in natural language are compared with the content of expected answers to questions or problems specified in curriculum scripts. LSA is used to evaluate the conceptual matches between learner input and tutor expectations, whereas the dialog manager determines how the tutor adaptively responds to the learner by selecting content from the curriculum script. The integration of available courseware with the tutorial dialog system guarantees the reusability of existing Web tutorials with minimal effort in the modification of the curriculum script and LSA module. This development thereby simplifies the change into more valuable Web based training courseware. © 2003 Elsevier Ltd. All rights reserved

Highly efficient beta-SiC-supported 0.5% Rh-based catalyst for CO hydrogenation to C-2 oxygenates

beta-SiC was used as a support for a 0.5% Rh-based catalyst for CO hydrogenation to C-2 oxygenates for the first time. The beta-SiC was acid etched and/or calcined at high temperature before use. The results show that the pretreatments had little effect on the textural and crystal properties of SiC, but calcination markedly increased the number of surface oxygen-containing groups. The pretreatment significantly increased the catalytic activities of SiC-supported Rh-Mn-Li/SiC catalysts in CO hydrogenation. An Rh efficiency of 97.2 g/g-Rh/h was achieved, the highest value reported in the literature to date. Possible reasons for this enhancement are suggested. (C) 2016 Elsevier B.V. All rights reserved

Ru coordinated with BINAP in knitting aryl network polymers for heterogeneous asymmetric hydrogenation of methyl acetoacetate

A facile method for the preparation of heterogeneous asymmetric hydrogenation catalysts was presented. BINAP was knitted with aryl compounds using formaldehyde dimethyl acetal (FDA) as a crosslinker by Friedel-Crafts reaction without any pre-modification. The prepared catalysts showed different catalytic activities, and excellent recyclablilty results could be achieved in asymmetric hydrogenation

Effect of different synthetic routes on the performance of propylene hydroformylation over 3V-PPh3 polymer supported Rh catalysts

This article studied the difference between two 3V-PPh3 polymer (POL-PPh3) supported Rh catalysts synthesized via different synthetic strategies, one-pot and post-synthesis, respectively. The catalytic performance of the two catalysts was further evaluated for the hydroformylation of propylene on a fixed-bed reactor. The catalyst prepared through post-synthesis (Rh/POL-PPh3) showed better catalytic activity compared to the one-pot sample (Rh-POL-PPh3), and exhibited excellent long-term stability. N-2 sorption, SEM, EXAFS and FT-IR characterization results suggested that the possible reasons for the different catalytic performance of two catalysts can be ascribed to the fact that part of Rh species was probably embedded into the framework of POL-PPh3 in the Rh-POL-PPh3 catalyst. Moreover, it might restrict the accessibility of reagents to Rh species and block the flexible coordination between Rh species and POL-PPh3. The Rh/POL-PPh3 catalyst synthesized via post-synthesis and the Rh species were uniformly distributed on the surface of PO-LPPh3, which might have a positive effect on the improvement of the mass transfer and the flexible coordination of Rh species with POL-PPh3

Promoting effect of Al on tethered ligand-modified Rh/SiO2 catalysts for ethylene hydroformylation

A Rh/SiO2 catalyst with excellent activity and stability for ethylene hydroformylation was developed by modifying with tethered diphenylphosphinopropyl and doped with an Al promoter. The catalyst was characterized by means of N-2 adsorption/desorption isotherms, transmission electron microscope, NH3 temperature programmed desorption, Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance. Experimental results showed that the existence of the Al promoter inhibited the growth of Rh particles, increased the number of exposed Rh atoms, changed the acidity of the catalyst surface, promoted in situ formation of active species that were similar to their corresponding homogeneous counterparts, and enhanced electron density of the P atom in the phosphine ligand. (C) 2014 Elsevier B.V. All rights reserved