Pd-Cu/La_(0.5)Pb_(0.5)MnO_3上氧化羰基化合成碳酸二苯酯

针对氧化羰基化合成碳酸二苯酯反应过程在低氧浓度下催化剂活性低的特点,研制出一种高效负载型双金属催化剂Pd-Cu/La0.5Pb0.5MnO3,并采用向反应体系中连续通入CO、O2的混合气体对苯酚氧化羰基化合成碳酸二苯酯(DPC)。实验表明,Pd-Cu/La0.5Pb0.5MnO3催化剂适宜的n(Cu)∶n(Pd)=1∶1,在苯酚50 g,催化剂1.0 g,通氧速度15 mL/min,CO进料速度285 mL/min,反应压力1.0 MPa,反应温度80℃条件下,反应5 h时,DPC产率达16.4%。     

Cu_(0.5)Zn_(0.5)Cr_(0.5)Al_(1.5)O_4尖晶石的制备及其催化性能

以硝酸铜、硝酸锌、硝酸铬、硝酸铝和氢氧化钠为原料,利用化学共沉淀法制得铜锌铬铝尖晶石Cu_xZn_(1-x)Cr_(0.5)Al_(1.5)O_4(x=0,0.25,0.50,0.75和1.00)(依次记为C1~C5),采用XRD、ICP、SEM和BET对其结构和物理、化学性质进行了表征。将不同组成的铜锌铬铝尖晶石作为催化剂在固定床反应器上催化合成N-甲基-4-氨基苯甲醚(NMA)。考察了尖晶石组成、反应温度、质量空速(WHSV)和反应原料配比对催化剂催化性能的影响。结果表明:反应温度为265℃,WSHV为0.15 h-1、n(甲醇)∶n(对氨基苯甲醚)=3.0∶1.0时,Cu_(0.5)Zn_(0.5)Cr_(0.5)Al_(1.5)O_4(C3)具有最佳的催化性能。对氨基苯甲醚转化率可达90.95%,NMA的选择性可达94.93%。     

叔戊烯与甲醇在Cs2.5H0.5PW12O40/SiO2 催化剂上的醚化

采用Cs2.5H0.5PWi2O40/SiO2催化剂进行了叔戊烯与甲醇的醚化反应研究考察了催化剂制备方法和工艺条件对叔戊烯转化率的影响.研究结果表明,以硅胶为载体,在负载量40%、焙烧温度400℃条件下制备的Cs2 5H0.5PWi2O40/SiO2催化剂具有较高的催化活性.在反应温度为80℃、压力为1.0MPa、n(甲醇)/n(叔戊烯)比为1.1、LHSV为1h-1的条件下,叔戊烯的转化率为68.57%.     

Pd/CuO-Ce0.5Mn0.5O2催化剂氧化羰基化合成碳酸二苯酯

采采用2种CuO引入方法制备了CuO-Ce0.5Mn0.5O2载体,再通过沉淀法负载活性组分Pd得到了0.5%Pd/CuO-Ce0.5Mn0.5O2催化剂,以XRD, SEM, BET等手段对催化剂进行了表征. 将该催化剂用于苯酚氧化羰基化合成碳酸二苯酯的反应,考察了引入CuO对催化剂催化活性的影响. 结果表明,采用溶胶-凝胶法添加不同含量的CuO时,载体的孔结构及活性组分在载体表面的分散都得到了不同程度的改善;在CuO添加量为9%(w)的条件下,反应在温度75℃、压力5 MPa下进行12 h,碳酸二苯酯收率可达17.06%.     

Cu0.5Zn0.5Cr0.5Al1.5O4尖晶石的制备及其催化性能

以硝酸铜、硝酸锌、硝酸铬、硝酸铝和氢氧化钠为原料,利用化学共沉淀法制备铜锌铬铝尖晶石（Cu0.5Zn0.5Cr0.5Al1.5O4）,并采用XRD、ICP、SEM和BET对其结构和物理、化学性质进行了表征。将不同组成的铜锌铬铝尖晶石作为催化剂在固定床反应器上催化合成了N-甲基-4-氨基苯甲醚(NMA)。考察了尖晶石组成、反应温度、空速(WHSV)和反应原料配比对催化剂催化性能的影响。结果表明：最佳反应条件为反应温度265℃,WSHV0.15h-1、甲醇与对氨基苯甲醚物质的量比3：1,Cu0.5Zn0.5Cr0.5Al1.5O4具有最佳的催化性能。对氨基苯甲醚单程转化率可达90.95%,NMA的选择性可达94.93%。     

聚乙二醇对旋转填充床制备La_(0.5)Pb_(0.5)MnO_3载体的影响

采用旋转填充床液液相共沉淀法制备了钙钛矿复合氧化物La0.5Pb0.5MnO3,以其作为载体制备了0.5%Pd(质量分数)/La0.5Pb0.5MnO3催化剂合成碳酸二苯酯。为了提高催化剂的活性,采用聚乙二醇(PEG)为分散剂对载体表面改性,通过XRD,SEM,BET手段对其物性进行表征,并对催化剂进行了活性评价。结果表明:PEG良好的空间位阻效应可以增加载体的分散度和比表面积,提高催化剂的活性。PEG10 000浓度为0.001 5 mol/L时效果最佳,载体比表面积达53.73 m2/g。反应温度65℃,总压5 MPa,p(CO)∶p(O2)=94∶6,反应3 h,DPC收率达13.30%。反应9 h,该条件下DPC收率可达21.90%。     

固体超强酸S2O2-8/TiO2催化合成乙酸正丁酯

以固体超强酸S2O2-8/TiO2为催化剂、冰乙酸和正丁醇为原料合成乙酸正丁酯,考察反应条件对酯化率的影响.结果表明,最佳反应条件n(醇):n(酸)=1.4:1,催化剂用量0.5 g(冰乙酸用量0.2 mol),过硫酸铵浓度0.75 mol·L-1,115～117℃反应1.5 h,酯化率达99%以上.催化剂可重复使用,且对设备腐蚀程度较小.     

超重力法制备La_(0.5)Pb_(0.5)MnO_3及其在碳酸二苯酯合成中的应用

采用液液相共沉淀法在旋转填充床中合成钙钛矿型复合氧化物La0.5Pb0.5MnO3的前驱体,再经高温焙烧后制备出碳酸二苯酯合成催化剂的载体材料。考察了旋转填充床转速、反应物流量和添加分散剂PEG对La0.5Pb0.5MnO3物性的影响,通过XRD、BET、SEM、粒度分析手段对载体进行表征。结果表明,旋转填充床转速为1200r.min-1,反应物流量为80L.h-1,加入PEG10000时可制备出纯晶相的钙钛矿载体,相应的载钯(Pd占载体质量的0.5%)催化剂在氧化羰基化合成碳酸二苯酯反应中的活性最好。当反应总压为5MPa、CO/O2分压比为96:6、反应时间3h、反应温度65℃时,碳酸二苯酯收率可达13.30%。     

Cu-Al类水滑石催化合成2-糠醛缩二乙醇的研究

采用共沉淀法制备了不同n(Cu)/n(Al)比的Cu-Al类水滑石,借助XRD、SEM和NH_3-TPD对催化剂进行表征.将Cu-Al类水滑石应用于2-糠醛缩二乙醇的合成,考察了催化剂组成、原料配比、催化剂用量及反应时间等对反应的影响.研究结果表明,Cu-Al二元类水滑石对该反应的催化活性和选择性都较好,是合成2-糠醛缩二乙醇的良好催化剂,当催化剂的组成为n(Cu)/n(Al)=0.5、n(醇):n(醛)=40:3、催化剂用量为0.1 g、反应时间90 min的条件下,糠醛的转化率可达54.43%,选择性接近100%.根据实验结果初步提出了催化机理.     

乙炔选择加氢催化剂的研究

采用固定床连续流动反应器对12%Ni/CNF、0.5%Pd/CNF、0.5%Pd/α-Al2O33种催化剂上的乙炔加氢反应进行了研究。考察了反应温度、n(H2)/n(C2H2)以及总空速对反应的影响,得到了在n(H2)/n(C2H2)较宽的范围内乙炔加氢为乙烯具有良好选择性的催化剂0.5%Pd/CNF。在50℃,n(H2)/n(C2H2)=23,乙炔空速为106h-1时,乙炔转化率达100%,乙烯收率为64.8%,乙烯选择性为73.8%。     

Piezoelectric K0.5Na0.5NbO3 Ceramics Textured Using Needlelike K0.5Na0.5NbO3 Templates

Improved performance by texturing has become attractive in the field of lead‐free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here, we report on successful texturing of K_0.5Na_0.5NbO₃ (KNN) ceramics by alignment of needlelike KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction (TCD) and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest <001>_pc orientation, while the response normal to the tape cast plane was lower than for a nontextured KNN. In situ X‐ray diffraction during electric field application revealed that non‐180° domain reorientation was enhanced by an order of magnitude in the TCD, compared to the direction normal to the tape cast plane and in the nontextured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.     

四元复合氧化物La_(0.5)Sr_(0.5)Ni_(0.5)Cu_(0.5)O_3的抗硫性能

以SO2 为毒物 ,采用脉冲中毒方法 ,再以CO氧化反应为探针 ,对三元复合氧化物催化剂La0 .5Sr0 .5NiO3 与La0 .5Sr0 .5CuO3 以及四元复合氧化物催化剂La0 .5Sr0 .5Ni0 .5Cu0 .5O3 等三种催化剂样品的抗硫毒能力、失活曲线、中毒催化剂的再生性能以及毒物残留形态等进行了全面考察和对比分析。实验结果表明四元复合氧化物催化剂La0 .5Sr0 .5Ni0 .5Cu0 .5O3 在SO2 毒物含量是 1 2 2×10 -2 mmol时 ,特别是在高温 (≥ 30 0℃ )条件下 ,具有优异的抗硫性能     

Thermally-stable large strain in Bi(Mn0.5Ti0.5)O3 modified 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics

(1-x)[0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃]-xBi(Mn_0.5Ti_0.5)O₃ (x = 0–0.06, BNKMT100x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn_0.5Ti_0.5)O₃ induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03–0.055 exhibit large strain of 0.31%–0.41% and electrostrictive coefficient of 0.027–0.041 m⁴/C². Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn_0.5Ti_0.5)O₃.     

Na0.5Bi0.5TiO3-Ba0.5Sr0.5Nb2O6无铅压电陶瓷的研究

采用固相法制备了(1-x)(Na0.5Bi0.5)TiO3-xBa0.5Sr0.5Nb2O6(0≤x≤1.0％)(简称(1-x)NBT-xBSN)无铅压电陶瓷,研究了不同BSN含量(x=0,0.1％,0.3％,0.5％,0.7％,1.0％,摩尔分数)样品的物相组成、显微结构及电性能.结果表明:所有样品均为纯钙钛矿结构,随掺杂量x的增加,陶瓷的相对密度pr、压电常数d33和机电耦合系数kp均先增大后降低,机械品质因子Qm和退极化温度Td则逐渐下降.该体系陶瓷具有弥散相变特征,弥散指数介于1.6～1.7.当x=0.5％时,陶瓷获得最佳性能:d33=92pC/N,kp=0.164,Qm=89,εr=650,tanδ=5.47％,pr=96.5％.     

Near-infrared emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: synthesis and bright luminescence

We present how CdTe_0.5Se_0.5 cores can be coated with Cd_0.5Zn_0.5S shells at relatively low temperature (around 200°C) via facile synthesis using organic ammine ligands. The cores were firstly fabricated via a less toxic procedure using CdO, trioctylphosphine (TOP), Se, Te, and trioctylamine. The cores with small sizes (3.2-3.5 nm) revealed green and yellow photoluminescence (PL) and spherical morphologies. Hydrophobic core/shell CdTe_0.5Se_0.5/Cd_0.5Zn_0.5S quantum dots (QDs) with tunable PL between green and near-infrared (a maximum PL peak wavelength of 735 nm) were then created through a facile shell coating procedure using trioctylphosphine selenium with cadmium and zinc acetate. The QDs exhibited high PL efficiencies up to 50% because of the formation of a protective Cd_0.5Zn_0.5S shell on the CdTe_0.5Se_0.5 core, even though the PL efficiency of the cores is low (≤1%). Namely, the slow growth process of the shell plays an important role for getting high PL efficiencies. The properties of the QDs are largely determined by the properties of CdTe_0.5Se_0.5 cores and shells preparation conditions such as reaction temperature and time. The core/shell QDs exhibited a small size diameter. For example, the average diameter of the QDs with a PL peak wavelength of 735 nm is 6.1 nm. Small size and tunable bright PL makes the QDs utilizable as bioprobes because the size of QD-based bioprobes is considered as the major limitation for their broad applications in biological imaging.     

K0.5Na0.5NbO3-BaCu0.5W0.5O3无铅压电陶瓷的结构与性能

以传统固相法工艺制备(1-x)K0.5Na0.5NbO3-xBaCu0.5W0.5O3[(1-x)KNN-xBCW]无铅压电陶瓷,研究不同BCW掺量(x=0％,0.1％,0.25％,0.5％,1.0％,摩尔分数,下同)对KNN陶瓷的晶体结构和电性能的影响,结果表明:x＜0.5％时,KNN陶瓷的相结构没有改变,仍为正交相...     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的极化工艺研究

主要研究了极化电场,极化时间和极化温度等工艺参数对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷介电和压电性能的影响。结果表明:极化电场和极化温度对压电陶瓷的介电、压电性能影响较大,而极化时间则影响较小。适宜的极化电场是3～3.5kV/mm,极化温度70～80℃,极化时间为10～15min。     

CeO2掺杂钛酸铋钠钾陶瓷的制备工艺与介电性能

为了进一步探索合成工艺对钛酸铋钠系无铅材料的结构及介电特性的影响,本文以甘氨酸为燃料,利用固相-燃烧法制备了CeO2掺杂的Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNKT)陶瓷.XRD表明,在固相合成工艺中引入燃烧法制备BNKT陶瓷,比传统固相法降低预烧温度150 ℃,掺杂的CeO2扩散进入了BNKT钙钛矿的晶格,且当掺杂量为0%~0.3%时,形成纯的钙钛矿相结构;SEM表明,CeO2掺杂使晶粒尺寸趋于平均,对晶粒生长有抑制作用;介电温谱表明,随着CeO2掺杂量增加,介电常数εr和退极化温度Td、相转变温度Tm降低,介电反常峰逐渐弱化,且室温至300 ℃,介电损耗tanδ始终在0.3%以下,并从微结构缺陷空位形成机制角度,结合铁电畴壁运动状态,分析讨论了对材料介电特性的作用规律.     

Raman spectroscopy of Na0.5Bi0.5TiO3

We have measured the Raman spectra of bismuth sodium titanate in its rhombohedral, tetragonal, and cubic phases, with special attention paid to the phase transitions at 584K and 837K (heating). Both transitions appear to be order-disorder and strongly first order, with large thermal hysteresis. The phonon spectra at temperature slightly below the tetragonal phase are remarkably similar to BaTiO₃ with A₁(To) modes at 130, 269, and 541 cm^-1 (compared with 170, 270, 520 cm^-1 in BaTiO₃) and an E(TO) at 52 cm^-1.     

Characterization of multiferroic PbFe0.5Nb0.5O3 and PbFe0.5Ta0.5O3 ceramics derived from citrate polymeric precursors

Ceramics of the perovskite multiferroics PbFe_0.5Nb_0.5O₃ (PFN) and PbFe_0.5Ta_0.5O₃ (PFT) were synthesized from new citrate polymeric precursors. X-ray tests pointed to trace amounts of the pyrochlore phase. SEM studies revealed the heterogeneous grain size distribution for PFN and the homogeneous one for PFT. Dielectric studies pointed to one diffuse T-C phase transition at 378 K for PFN and two diffuse M-T and T-C phase transitions, at 200 and 235 K, for PFT, respectively. X-ray photoelectron spectroscopy studies of PFN reveal that all ions exist in one valence state, however, with two chemical shifts for Pb²⁺. Two valence states for the majority of ions of PFT seem to be connected with a higher volume fraction of the amorphous grain-boundary phase. The electronic energy band gap for both compounds is approximately 2.8 eV. Two magnetic transitions, ie, from the paramagnetic to the antiferromagnetic phase and then to the spin-glass phase, were observed at 156 and 10 K for PFN, and at 145 and 15 K for PFT, respectively.