沙芥乳酸菌发酵饮料的工艺优化

选取植物乳杆菌、保加利亚乳杆菌以及嗜热链球菌3 种益生菌,对沙芥进行发酵处理,以发酵活菌数和酸度为参考指标,通过单因素试验以及正交试验确定复合菌的配比为植物乳杆菌∶嗜热链球菌∶保加利亚乳杆菌=4∶4∶3（质量比）,最佳发酵工艺：发酵温度33 ℃、发酵时间14 h、菌种接种量4%;基于此发酵工艺条件,测得沙芥发酵饮料所含活菌数达6.03×108 CFU/mL。     

微通道结构数值模拟及实验性能评价

Fluent软件的数值模拟结果显示伞形微通道结构比U形直线形微通道结构具有更加高效的混合效率,但该结构也存在流动死区,结合优化方向提出一种压降更小、混合效率较优更适用于液-液非均相反应的菱形微通道结构。同时,本文利用前述3种不同微通道结构反应器及常规反应器开展丙烯酸十四酯的合成评价对比实验,红外光谱及核磁谱图对反应产物的分析表征均证明了丙烯酸十四酯的生成。常规反应器和微反应器在相似工艺条件下,丙烯酸十四酯的收率仅为82%,停留时间更是长达300min,而微反应器中收率均达到90%以上,停留时间不超过3.5min,且菱形微通道结构反应器比U形直线形和伞形微通道结构反应器所得丙烯酸十四酯的收率都大,达到97%,说明菱形微通道结构更加有利于物料间的充分混合反应,这与菱形微通道结构数值模拟显示的结果是一致的,从而验证了数值模拟结果的可靠性。     

Purification of Free DHA by Selective Esterification of Fatty Acids from Tuna Oil Catalyzed by Rhizopus oryzae Lipase

Tuna fish oil contains 25–30 % docosahexaenoic acid (DHA) and is one of the richest sources of DHA. The present paper investigates the enrichment of DHA by selective esterification of fatty acids obtained from hydrolysis of tuna fish oil catalyzed by Rhizopus oryzae lipase (ROL). The fatty acid mixture obtained after hydrolysis of tuna fish oil, referred to as tuna-FFA contained 26 % DHA. For purification/concentration of DHA in free fatty acids, selective esterification of the fatty acid mixtures with butanol was carried out using ROL in a water-organic solvent system. The best reaction parameters found in this study were pH 7, temperature 35 °C, agitation speed 800 rpm and a fatty acid to solvent (iso-octane) ratio of 1:1.32 (w/v). Also, the effects of other parameters such as type of alcohol, type of enzyme, alcohol to fatty acid ratio, enzyme to fatty acid ratio were studied to determine the most suitable reaction conditions. Exactly 76.2 % of tuna-FFA was esterified in 24 h, under the most suitable reaction conditions and the DHA content in the fatty acid fraction rose from 26 to 86.9 % with 80 % recovery of DHA, after selective esterification. The DHA content of fatty acids in butyl esters was found to be 13.6 %.     

High–Energy‐Storage Density Capacitors of Bi(Ni1/2Ti1/2)O3–PbTiO3 Thin Films with Good Temperature Stability

High–energy‐storage density capacitors with thin films of 0.5Bi(Ni_1/2Ti_1/2)O₃–0.5PbTiO₃ (BNT–PT) were fabricated by chemical solution deposition technique on Pt/Ti/SiO₂/Si substrates. The dense thin films with pure‐phase perovskite structure could be obtained by annealing at 750°C. High capacitance density (~1925 nF/cm² at 1 kHz) and extremely high‐energy density (~45.1 J/cm³) under an electric field of 2250 kV/cm were achieved at room temperature. The energy‐storage density and efficiency varied little in a wide temperature range from ?190°C to 250°C. The high–energy‐storage density and good temperature stability make BNT–PT films promising candidates for high power electric applications.     

EFFECT OF PRETREATMENT CONDITIONS ON STRUCTURAL CHARACTERISTICS OF WHEAT STRAW

Structural characteristics of lignocellulosic biomass such as surface area, pore volume, crystallinity, hemicellulose, and lignin content significantly affect the yield of fermentable sugars for bioethanol production. In the present work, the effect of dilute acid pretreatment was studied on structural characteristics of wheat straw, using different combinations of process variables (temperature, time, and acid concentration). Pretreated wheat straw (PWS) exhibited higher available surface area and pore volume along with low hemicellulose and lignin content. Crystallinity index (CrI) of biomass at different pretreatment conditions showed an increased trend followed by sharp decrease at high temperature (190°C) conditions. Maximum increase in surface area (7.1 m²/g compared to 4.0 m²/g for untreated wheat straw) was obtained at pretreatment conditions of 180°C temperature, 0.5% (v/v) acid, and 7 min time. SEM imaging of biomass revealed that pore breaking, compression of pores, and partial pore blocking in the case of high temperature (190°C) pretreatment conditions may be the reason behind decreased surface area of biomass. FT-IR analysis showed almost complete hemicellulose removal and acid-soluble lignin removal after dilute acid pretreatment but insufficient removal of acid insoluble lignin.

[Supplementary material is available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resource: figure showing XRD pattern of biomass with respect to different pretreatment conditions.]     

Synthesis,Characterization, Luminescent and Thermal Properties of a Hybrid Inorganic–Organic Polymeric Framework Formed by Lead (II) Pyridinecarboxylate

Abstract  

A coordination polymer of formula [Pb_0.5(pyc)] _n , 1, where Hpyc = pyridine-3-carboxylic acid, has been synthesized and structurally characterized by X-ray single crystal diffraction analysis. Every Pb(II) centre demonstrate trigonal dodecahedron geometry. The ligand i.e. pyridine-3-carboxylate offers μ _{3 -} η ² : η ¹ coordination pattern using its hetero donor centres. The complex initially forms an infinite 1D chain (c-axis) which is turned to 2D sheet and finally a 3D network is recognized through ligand connectivity. Stabilization of 3D structure is further reinforced by π–π stacking interaction. An open channel is identified along c-axis. TG analysis has been performed for the complex. Emission study demonstrates the existence of intraligand and metal-to-ligand charge transfer transition in 1.     

Carbon monoxide hydrogenation over cobalt catalyst in a tube-wall reactor: Part II. Modelling studies

A mathematical model was developed to predict the performance of Fischer-Tropsch Synthesis over cobalt catalyst in a tube-wall reactor. Comparison was made between model predictions and previous experimental results (part 1 of this paper) for pressures 0.35-1.03 MPa, temperatures 250?275°C, and exposure velocities 139-722 μ/s. The agreement was good. The model predicts an increase in methanation activity with temperature. Carbon monoxide and hydrogen conversions, and water and carbon dioxide concentrations increase along the reactor axis. With an increase in exposure velocity, hydrocarbons and carbon dioxide production increase, but water production decreases. However, the water-gas shift activity increases continuously along the reactor axis. The model is based on two-dimensional transport equations, and employs the orthogonal collocation method in its numerical predictions.     

η-Al2O3与γ-Al2O3在CS2催化水解反应中的性能比较

通过制备高纯度的前驱体湃铝石获得了η-Al₂O₃材料,采用XRD验证了η-Al₂O₃与γ-Al₂O₃在晶相结构上的差异,比较了两者的表面形貌、织构及酸碱性能,结果显示,η-Al₂O₃与γ-Al₂O₃的比表面积相当,但η-Al₂O₃具有更弱的弱碱位和较少的强碱位,并拥有丰富的中等强度酸性位。将η-Al₂O₃与γ-Al₂O₃作为催化剂应用于CS₂水解反应,结果表明,在(200~450) ℃测试温度范围内,η-Al₂O₃催化剂对CS₂的水解活性始终优于γ-Al₂O₃,两种催化剂上CS₂反应的浓度效应也明显不同,推测与它们的酸碱性质影响了对CS₂的吸附能力有关,导致两者催化CS₂水解反应遵循了不同的机制。     

Morphology and deactivation behaviour of Co–Ru/γ‐Al2O3 Fischer–Tropsch synthesis catalyst

Deactivation of Co–Ru/γ‐Al₂O₃ Fischer–Tropsch (FT) synthesis catalyst along the catalytic bed over 850 h of time‐on‐stream (TOS) was investigated. Catalytic bed was divided into four parts and structural changes of the spent catalysts collected from each catalytic bed after FT synthesis were studied using BET, ICP, XRD, TPR, carbon determination, H₂ chemisorption and oxygen titration techniques. Rapid deactivation was observed during first 200 h of FT synthesis. In this case, the deactivation rate was not dependent on the number of the catalyst active sites. It was zero order to CO conversion and independent of the size of active sites. Beyond the TOS of 200 h, the deactivation could be simulated with a power law expression: . The physical properties of the catalyst charged in 1st half of the reactor did not change significantly. Interaction of cobalt with alumina and formation of mixed oxides of the form xCoO·yAl₂O₃ and CoAl₂O₄ was increased along the catalytic bed. Percentage reducibility and dispersion decreased by 2.4–25.5% and 0.5–8.8% for the catalyst in the beds 1 and 4, respectively. Particle diameter increased by 0.8–6.1% for the catalyst in the beds 1 and 4 respectively suggesting higher rate of sintering at last catalytic bed. The amount of coke formation in the 4th catalytic bed was 6 times more than that of in bed 1.     

基于CBR-HJaya-BP的液压缸加工工时预测研究

为了提高冶金行业液压缸加工工时预测精度,提出一种结合基于案例的推理（CBR）和混合Jaya算法优化BP神经网络的液压缸加工工时预测方法（CBR-HJaya-BP）。使用混合Jaya算法优化BP神经网络的初始权值和阈值,采取基于Sin混沌反向学习的种群初始化策略提高初始解的质量,引入阿基米德优化算法中的转移算子,在探索阶段采用均匀交叉产生中间种群,在开发阶段使用Jaya公式产生中间种群,在解的保留策略中引入了模拟退火算法中的Metropolis准则,以跳出局部最优。以某冶金液压缸制造企业的历史加工数据库为样本,采用CBR方法提取与待预测液压缸的特征参数相似度最高的历史数据,使用提出的HJaya-BP模型进行预测实验,并与改进前的Jaya-BP模型以及原始BP神经网络模型进行对比。实验结果表明,HJaya-BP模型的预测准确度和稳定性均为最优。