NNI-1型C_5/C_6烷烃异构化催化剂长周期运行分析及建议

中国石化海南炼油化工有限公司0.2 Mt/a C5/C6烷烃异构化装置以连续重整装置的拔头油为原料,使用NNI-1催化剂,采用一次通过流程,不设脱异戊烷塔和稳定塔,经设在连续重整装置内的脱丁烷塔稳定处理后作为汽油调合组分。该装置于2006年9月开工投产,截至2015年3月已连续运行3个周期。长周期运行分析结果表明:前两个周期中NNI-1催化剂具有较高的异构化活性及选择性,C5异构化率为60%左右,C6异构化率为80%左右,C6选择性为15%左右,产品辛烷值基本达到技术指标要求(RON≥78);而在第三周期运行中,催化剂积炭增加等原因导致其异构化活性及选择性降低,异构化产品辛烷值提升能力呈现逐步衰减的趋势,提高反应苛刻度已不能弥补催化剂活性下降造成的产品辛烷值降低。为保证装置长周期运行,建议择机停工对催化剂进行再生,或是直接换用与装置原料性质匹配的异构化催化剂。     

儿童用品TBT通报数据可视化预警研究

探索采用数据可视化技术分析儿童用品TBT通报数据,以可视化图形图像呈现通报热点并揭示趋势信息,提出对策与建议,助力为儿童用品产业升级、TBT预警数据分析和信息传播工作提供新思路,提高中小企业的国外市场准入机会。     

SDN中基于KMOBPSO的高可靠性控制器部署算法

针对SDN中控制器系统的单节点故障问题,兼顾系统成本和系统时延,应用N+1冗余备份模型来提高SDN控制器部署的可靠性,并将其抽象为多目标优化问题.同时,提出了一种融合K-means聚类算法和遗传算子的多目标二进制粒子群算法——KMOBPSO算法,以求解SDN控制器高可靠性部署问题的解.仿真结果表明,所提算法具有求解精度高、分布均匀、沿Pareto前沿面覆盖广的特点,能够显著提高SDN中控制器部署的可靠性.     

Mg0.5NixZn0.5-xFe2O4 spinel as a sustainable magnetic nano-photocatalyst with dopant driven band shifting and reduced recombination for visible and solar degradation of Reactive Blue-19

Focussing on visible light active ferrites for high performance removal of noxious pollutants, we report the synthesis of Mg_0.5Ni_xZn_0.5-xFe₂O₄ (x = 0.1, 0.2, 0.3, 0.4, & 0.5) ferrite nanoparticle for degradation of reactive blue-19 (RB-19). Lattice parameters calculated using intense X-ray diffraction (XRD) peaks and Nelson-Riley plots (N-R plot) are in well agreement with each other. The sample Mg_0.5Ni_0.4Zn_0.1Fe₂O₄ (M5N4) exhibits best performance with 99.5% RB-19 degradation in 90 min under visible light. Photoluminescence (PL) results confirm that recombination of charge carriers is highly reduced in the photocatalyst. Scavenging experiments suggest that O₂⁻ radicals were the dominant species responsible for photocatalytic performance. The photocatalytic mechanism was explained in terms of dopant driven shifting of conduction bands and valence bands (calculated by Mott-Schottky plots). The thermodynamic probability of radical generation along with role of redox cycles of metal ions has been discussed in the mechanism. The dye degradation was ascertained by detection of intermediates via mass spectrometry analysis and a possible degradation route was also predicted. The findings in this work provide intriguing opportunities to modify the electronic band structure of spinel ferrites for visible and solar light photocatalytic activity for environmental detoxification.     

Residual strain in cadmium telluride/gallium arsenide (001) heterostructures as a function of temperature

Optical studies of residual strain in cadmium telluride (CdTe) films grown using molecular beam epitaxy on gallium arsenide (GaAs) substrate have been performed using photoreflectance techniques. Measurements have been conducted to determine the fundamental transition energy, heavy-hole and light-hole transition energy critical-point parameters in a range of temperatures between 12 and 300 K. There are problems inherent in the fabrication of optoelectronic devices using high-quality CdTe films, due to strain effects resulting from both the lattice mismatch (CdTe: 14.6%) and the thermal expansion coefficient difference. The CdTe film exhibits compressive stress causing valence-band splitting for light and heavy holes. We have used different models to fit the obtained experimental data and, although the critical thickness for the CdTe has been surpassed, the strain due to the lattice mismatch is still significant. However, the strain due to the thermal expansion is dominant. We have found that the fundamental transition energy, E₀, is affected by the compressive strain and the characteristic values are smaller than those reported. In addition, the total strain is compressive for the full measured range, since the strain due to the lattice mismatch is one order of magnitude higher than that calculated from the thermal expansion.     

Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

The effect of SO₂ gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH₃) over a TiO₂ photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO₂ (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO₂ gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N₂ adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.     

Combined hardware–software multi-parallel prefiltering on the Convey HC-1 for fast homology detection

Protein databases used in research are huge and still grow at a fast pace. Many comparisons need to be done when searching similar (homologous) sequences for a given query sequence in these databases. Comparing a query sequence against all sequences of a huge database using the well-known Smith–Waterman algorithm is very time-consuming. Hidden Markov Models pose an opportunity for reducing the number of entries of a database and also enable to find distantly homologous sequences. Fewer entries are achieved by clustering similar sequences in a Hidden Markov Model. Such an approach is used by the bioinformatics tool HHblits. To further reduce the runtime, HHblits uses two-level prefiltering to reduce the number of time-consuming Viterbi comparisons. Still, prefiltering is very time-consuming. Highly parallel architectures and huge bandwidth are required for processing and transferring the massive amounts of data. In this article, we present an approach exploiting the reconfigurable, hybrid computer architecture Convey HC-1 for migrating the most time-consuming part. The Convey HC-1 with four FPGAs and high memory bandwidth of up to 76.8 GB/s serves as the platform of choice. Other bioinformatics applications have already been successfully supported by the HC-1. Limited by FPGA size only, we present a design that calculates four first-level prefiltering scores per FPGA concurrently, i.e. 16 calculations in total. This score calculation for the query profile against database sequences is done by a modified Smith–Waterman scheme that is internally parallelized 128 times in contrast to the original Streaming ‘Single Instruction Multiple Data (SIMD)’ Extensions (SSE)-supported implementation where only 16-fold parallelism can be exploited and where memory bandwidth poses the limiting factor. Preloading the query profile, we are able to transform the memory-bound implementation to a compute- and resource-bound FPGA design. We tightly integrated the FPGA-based coprocessor into the hybrid computing system by employing task-parallelism for the two-level prefiltering. Despite much lower clock rates, the FPGAs outperform SSE-based execution for the calculation of the prefiltering scores by a factor of 7.9.     

Preparation and physical properties of the layered niobate Cu0.5Nb3O8: Application to photocatalytic hydrogen evolution

The new layered niobate Cu_0.5Nb₃O₈ is synthesized by soft chemistry in aqueous electrolyte via Cu²⁺→H⁺ exchange between copper nitrate and HNb₃O₈·H₂O. The characterization of the exchanged product is made by means of thermal gravimetry, chemical analysis, X-ray diffraction and IR spectroscopy. Thermal analysis shows a conversion to anhydrous compound above 500 °C. The oxide displays a semiconductor like behavior; the thermal variation of the conductivity shows that d electrons are strongly localized and the conduction is thermally activated with activation energy of 0.13 eV. The temperature dependence of the thermopower is indicative of an extrinsic conductivity; the electrons are dominant carriers in conformity with an anodic photocurrent. Indeed, the Mott–Schottky plot confirms n-type conduction from which a flat band potential of −0.82 V_SCE, an electronic density of 8.72×10¹⁹ m⁻³ and a depletion width of 4.4 nm are determined. The upper valence band, located at ~5.8 eV below vacuum is made up predominantly of Cu²⁺: 3d with a small admixture of O²⁻: 2p orbitals whereas the conduction band consists of empty Nb⁵⁺: 5s level. The energy band diagram shows the feasibility of the oxide for the photocatalytic hydrogen production upon visible light (29 mW cm⁻²) with a rate evolution of 0.31 mL g⁻¹ min⁻¹.     

Excited-state absorption of meso-tetrasulfonatophenyl porphyrin: Effects of pH and micelles

The influence of the environment on the excited state transitions of meso-tetrakis(p-sulfonatophenyl) porphyrin (TPPS) is reported. TPPS was investigated in protonated and non-protonated forms, and in the presence of the cationic cetyltrimethylammonium bromide (CTAB) micelles. The singlet excited-state absorption spectra were measured by using the white-light continuum Z-scan technique and the triplet–triplet absorption spectra were acquired employing an association of laser flash photolysis and Z-scan techniques. Our results show that the perseveration of the molecular symmetry, upon excitation, depends on the state of multiplicity of the molecules, as well as on the environment and structural characteristics of the porphyrin. Additionally, it was observed that for excited molecules, the ring distortion caused by the protonation of porphyrin ring has great influence on the changes observed for the symmetry and vibronic structure. The results clearly show that the porphyrin investigated is a promising candidate for optical limiting applications for all investigated environments.