Catalytic hydrothermal liquefaction of D. tertiolecta for the production of bio‐oil over different acid/base catalysts

In this article, two acid catalysts (ZrO₂/SO₄^2? and HZSM‐5) and two base catalysts (MgO/MCM‐41 and KtB) were used in catalytic hydrothermal liquefaction (HTL) of Dunaliella tertiolecta (D. tertiolecta) for the production of bio‐oil. The results indicated that the acid/base property of the catalyst plays a crucial role in the catalytic HTL process, and the base catalyst is conducive to the improvement of conversion and bio‐oil yield. When KtB was used as the catalyst, the maximum conversion and bio‐oil yield was 94.84 and 49.09 wt %, respectively. The detailed compositional analysis of the bio‐oil was performed using thermogravimetric analysis, elemental analysis, FT‐IR, and GC‐MS. The compositional analysis results showed that the introduction of catalyst is beneficial for reducing the fixed carbon content in the bio‐oil, and the structure of catalyst influences on the bio‐oil composition and boiling point distribution. Based on our results and previous studies, the probable catalytic HTL microalgae model over various catalysts can be described that the main chemical reactions include ketonization, decarboxylic, dehydration, ammonolysis, and so forth. with HZSM‐5 and MgO/MCM‐41 as the catalyst; the cyclodimerization, decomposition, Maillard reaction, and ketonization are the main reactions with ZrO₂/SO₄^2? as the catalyst; the dehydration, ammonolysis, Maillard reaction, and ketonization can occur with KtB as the catalyst. Therefore, a plausible reaction mechanism of the main chemical component in D. tertiolecta is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1118–1128, 2015     

新型高精度数控交流恒流源的设计

基于直接数字频率合成技术设计了一种新型高精度数控交流恒流源系统。该系统由低频正弦信号发生器和恒流源电路组成,其中正弦信号发生器由STM32单片机搭建,恒流源电路在功率放大电路的基础上添加反馈网络,使新型恒流源具有更高的输出精度和更好的幅值稳定性。测试结果显示：该恒流源输出电流的幅值、频率、相位、输出时长可控,具有工作稳定好、精度高、噪声小的特点。     

具有瞬时较大波动的信号降噪方法研究

针对一类具有瞬时较大波动的信号,提出了一种基于小波阈值的滤波方法.在信号中噪声为加性白噪声的情况下,其重建信号与原含噪信号间的残差不应当随着信号振幅的增大而增大.现有的小波阈值滤波方法在此方面表现不佳.在小波阈值计算时原始信号的系数选取范围上提出了改进,计算小波滤波阈值时,不使用信号中瞬时较大波动的部分对应的小波系数.将此方法应用于实测获得的数据,计算结果表明,其能在有效地保留信号特征的前提下,较好地消除噪声.     

基于分子动力学的无定形纤维素热力学性质仿真

为更深入地在微观角度上研究变压器绝缘纸老化机理,利用分子动力学仿真,对不同温度下纤维素无定形区的热力学性质进行了研究。结果表明:纤维素无定形区为各向同性弹性材料,其弹性系数和各模量随着模拟温度的升高均有减小的趋势,与晶区相比,温度对其影响较大;无定形区的刚性随温度升高出现较大减弱;随着温度升高,无定形区内氢键数量减少,并且分子内氢键数目较分子间氢键数目下降快。对比晶区内的氢键数目在相同模拟温度下的极小变化,可知纤维素的老化首先是从纤维素的无定形区内分子间的氢键被破坏开始的。随模拟温度的升高,纤维素分子链运动加剧,但其末端距无明显变化。温度对纤维素无定形区的力学性质和氢键的影响从分子层次上阐明了纤维素绝缘老化实验中结晶度升高及无不定形区先行老化的微观机理。     

Preparation of polyacrylamide grafted collagen extracted from leather wastes and their application in kaolin flocculation

This is probably the first report on the synthesis of a series of novel collagen‐based flocculants (CP11, CP12, and CP13) by grafting polyacrylamide (PAM) chains onto the collagen backbone, which was directly extracted from leather shavings via alkali hydrolysis. The results from FTIR, XRD, ¹H NMR, and TGA well supported that PAM chains had been successfully grafted onto collagen backbone. In addition, the micrographs of SEM revealed that the PAM grafted collagen possessed much more porous and looser surface structures in comparison with virgin collagen. Zeta potential measurement showed that the introduction of branched PAM chains helped to improve the positively charge density. Furthermore, CP12 performed the best in the kaolin flocculation with the highest flocculation rate about 24%·min^?1 and could induce the generation of much larger and denser floccs for the fast settling of kaolin particles. The corresponding flocculation mechanism was also presented by analyzing the collected flocs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41556.     

Water filtration properties of novel composite membranes combining solution electrospinning and needleless melt electrospinning methods

New composite polyvinyl alcohol (PVA)/polypropylene (PP) membranes were prepared by combining both solution electrospinning and melt electrospinning methods. Self‐designed and made needleless melt electrospinning device was used to fabricate PP membranes which acted as the support layer. PVA membrane on the surface was fabricated via solution electrospinning. The electrospun PVA/PP composite membranes were characterized by the pore size distribution, pure water flux, and rejection ratio, then compared with general composite membranes. Characterizations revealed that the fiber diameter of solution electrospun PVA membrane and melt electrospun PP membrane were 0.171 ± 0.027 and 2.24 ± 0.33 μm, respectively, and the average pore size was 0.832 μm and 27.29 μm, which was much smaller than the nonwoven membrane. The rejection ratio to the 500 nm particles of the PVA/PP composite membrane could reach more than 96%, which was much larger than that of the PVA/non‐woven substrate of 90%, and the melt electrospun PP membrane of 80%, and still maintained high permeate flux of 32,346 L/m²h under the pressure of 0.24 bar. This approach of compositing the solution electrospun membranes and melt electrospun membranes could be useful in designing novel microfiltration membrane owning both higher flux and higher rejection ratio. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41601.     

Decomposition mechanisms of cured epoxy resins in near‐critical water

A reaction mechanism based on the near‐critical water homolysis of bonds in the cured epoxy followed by the saturation of the resulting radicals by hydrogen abstraction from the donor was discussed. The compounds evolved during degradation were identified by gas chromatography and mass spectrometer. The materials prepared possess the characteristics of thermosets, due to the presence of ether groups in the polymer chains, which were broken at the beginning of degradation. The degradability increased when the reaction time and reaction temperature increased. Based on the experimental results, a probable macroscopic mechanism was proposed. The near‐critical water degradation mechanisms of polymers consist of three categories: random scission, unzipping, and side group elimination, which simultaneously occurs in the reactor. The first random scission of links caused a molecular weight reduction of the raw polymer, the second side‐group elimination caused the generation of the volatile product, and the last unzipping produced either fragmentation to smaller oligomeric units or unzipping all the way to monomers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41648.     

Synthesis and Luminescent Properties of the Li0.995−xMgxSi2−xAlxN3: Eu2+0.005 Phosphors

Li_0.995?xMg_xSi_2?xAl_xN₃: Eu²⁺_0.005 (LSN: xM) (0 ≤ x ≤ 0.04) phosphors were successfully synthesized by gas‐pressed sintering. Double substitution which is partial replacement of (LiSi)⁵⁺ with (MgAl)⁵⁺ is presented as a useful way to improve luminescence properties. With an increase in the substitution concentration, the intensity of the emission band of LSN: xM was enhanced and the peak position shows blue shift due to the decreased stokes shift. Furthermore, LSN: xM (0 ≤ x ≤ 0.04) shows narrower full width at half maximum and higher thermal stability than Li_0.995Si₂N₃: Eu²⁺_0.005.     

Designing of anion‐functionalized ionic liquids for efficient capture of SO2 from flue gas

Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO₂ from flue gas, where the concentration of SO₂ is only 2000 ppm. The effect of the anion on SO₂ absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P₄₄₄₂][Tetz], was further designed and applied for the capture of SO₂, which shows the high absorption capacity of 0.18 g SO₂ per g IL and excellent reversibility for 2000 ppm SO₂. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015