Decomposition of Copper Formate Clusters: Insight into Elementary Steps of Calcination and Carbon Dioxide Activation

The decomposition of copper formate clusters is investigated in the gas phase by infrared multiple photon dissociation of Cu(II)_n(HCO₂)_2n+1⁻, n≤8. In combination with quantum chemical calculations and reactivity measurements using oxygen, elementary steps of the decomposition of copper formate are characterized, which play a key role during calcination as well as for the function of copper hydride based catalysts. The decomposition of larger clusters (n > 2) takes place exclusively by the sequential loss of neutral copper formate units Cu(II)(HCO₂)₂ or Cu(II)₂(HCO₂)₄, leading to clusters with n=1 or n=2. Only for these small clusters, redox reactions are observed as discussed in detail previously, including the formation of formic acid or loss of hydrogen atoms, leading to a variety of Cu(I) complexes. The stoichiometric monovalent copper formate clusters Cu(I)_m(HCO₂)_m+1⁻, (m=1,2) decompose exclusively by decarboxylation, leading towards copper hydrides in oxidation state +I. Copper oxide centers are obtained via reactions of molecular oxygen with copper hydride centers, species containing carbon dioxide radical anions as ligands or a Cu(0) center. However, stoichiometric copper(I) and copper(II) formate Cu(I)(HCO₂)₂⁻ and Cu(II)(HCO₂)₃⁻, respectively, is unreactive towards oxygen.     

GdPO4:Sm3+荧光粉的焙烧温度和掺杂浓度的优化及发光和磁性能

以GdPO₄为基质,Sm³⁺为激活剂,采用水热法合成了纳米荧光粉前驱体,分别在800、900、1 000、1 100和1 200℃下焙烧,得到一系列GdPO₄:Sm³⁺荧光粉。首先探究了GdPO₄:Sm³⁺的最佳焙烧温度;其次研究了Sm³⁺掺杂浓度对GdPO₄:Sm³⁺荧光性能的影响;最后研究了GdPO₄:2% Sm³⁺的高温荧光性能和磁性能。使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、磁强计和荧光分光光度计(FL)对荧光粉的晶体结构、形貌、发光和磁性能进行了表征。结果表明:荧光粉的晶体结构由前驱体六方晶系GdPO₄·H₂O:Sm³⁺变为单斜晶系的GdPO₄:Sm³⁺,形貌由纳米棒变为无规则块体。当焙烧温度为1 000℃,Sm³⁺掺杂浓度为2%时,荧光粉的发光强度和荧光寿命达到最大值。GdPO₄:2% Sm³⁺中Sm³⁺之间能量传递类型为电偶极-电偶极相互作用,能量传递的临界距离为1.646~1.884 nm。最佳样品GdPO₄:2% Sm³⁺有优异的热稳定性,热猝灭活化能为-0.157 eV,且具有良好的顺磁性,质量磁化率为1.22×10^-4 emu·g^-1·Oe^-1。     

Biomass-derived porous material synthesized by one-step calcination method for the magnetic solid-phase extraction of polychlorinated biphenyls in water

Recent findings unfold that biomass materials with the micro/mesoporous structure were often treated as adsorbents for organic substances. In this work, a one-step calcination method was adopted in the preparation of magnetic porous green bean biomass material. It has the properties of magnetism and porosity after the addition of Co(NO₃)₂ and high-temperature calcination. A variety of characterizations have been operated, including energy dispersive X-ray detector, vibrating sample magnetometer, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and so on. It has a specific surface area of 168.1611 m²/g and a pore volume of 0.1764 cm³/g. The material was used in magnetic solid-phase extraction of three polychlorinated biphenyls: 2-chlorobiphenyl, 4-chlorobiphenyl, and 2,2,5-trichlorobiphenyl. Several factors were investigated, such as material amount, eluents, adsorption time, solution pH, salinity, and reusability. Under optimized conditions, good recoveries (90.24–93.34%) were achieved with the relative standard deviation in a range from 2.30 to 4.83%. Three real water samples (tap, river, and lake water) were tested to verify the accuracy of the method. This method can be successfully used in the analysis of some polychlorinated biphenyls congeners in water.     

CuWO4/C复合物的制备和其在模拟油氧化脱硫中的应用

用混合煅烧法制备了CuWO₄/C复合物,并采用XRD、SEM、和BET等技术对其结构进行表征。以CuWO₄/C复合物为催化剂、过氧化氢为氧化剂、1-乙基-3-甲基咪唑硫酸乙酯盐离子液体为萃取剂氧化脱除模拟油中的二苯并噻吩(DBT)。考察了反应温度、双氧水加入量、萃取剂加入量等因素对脱硫效果的影响。结果表明,在相同的实验条件下,相比于CuWO₄,CuWO₄/C复合物具有更高的脱硫率。在模拟油为5.0 mL、催化剂加入量为0.02 g、H₂O₂加入量0.2 mL、萃取剂加入量1.0 mL、反应温度70℃、反应时间180 min的最佳实验条件下,DBT转化率可达到98.2%,催化剂循环使用四次活性没有明显降低。     

液固相同晶取代法制备Sn-NaY催化环己酮Baeyer-Villiger氧化

以微孔分子筛NaY为载体,SnCl_4·5H_2O为锡源,通过液固相同晶取代法制备催化材料Sn-NaY,研究了脱铝预处理和焙烧两个因素对制备Sn-NaY的影响.采用FT-IR、UV-Vis、XRD、N_2物理吸附、ICP、NH_3-TPD、吡啶红外、激光拉曼等手段对催化材料进行了表征.结果表明:对载体进行脱铝预处理有利于分子筛在催化剂制备过程中保持良好的骨架结构,焙烧有利于进入分子筛骨架中的Sn(Ⅳ)与硅羟基成键,从而形成有催化活性的四配位的Sn(Ⅳ),而空气氛围下焙烧容易产生骨架外SnO_2物种.Sn-NaY催化环己酮Baeyer-Villiger氧化结果表明,在环己酮0.03 mol,n(H_2O_2)∶n(酮)=1.5∶1,0.35 g催化剂,15 mL乙腈,70℃反应24 h的工艺条件下,N_2氛围焙烧的同晶取代脱铝催化剂性能最好,环己酮的转化率可达44%,己内酯的选择性为62%.     

铁改性水滑石基Pt/BaO/MgFeO催化剂焙烧温度对催化剂结构及NO_x吸附-还原性能的影响

采用共沉淀法和浸渍法制备了贵金属负载均匀的镁铁水滑石基稀燃氮氧化物捕集(LNT)催化剂,并采用多种表征手段研究了焙烧温度对催化剂结构及NO_x吸附-还原反应的影响。结果表明,500-700℃焙烧后催化剂晶相结构稳定,800℃焙烧后催化剂表面出现烧结,Pt颗粒发生团聚;随焙烧温度升高,催化剂的NO_x脱附峰面积先减小后增大,但峰值温度变化不大;与500℃焙烧催化剂相比,800℃焙烧后催化剂表面NO_x吸附物种及吸附路径发生改变,而还原反应产物中氨气/氮气体积比下降,NO_x转化效率由91.7%降为85.2%。     

不同焙烧气氛对氧化镁表面碱性的影响

The MgO samples are prepared by heating Mg(OH) 2 at 600 ℃ in different atmospheres. The XRD results show that Mg(OH) 2 is decomposed into MgO after calcination. The results of BET indicate that the specific surface area of the samples is affected by the calcination atmosphere, the sample preheated in vacuum has the highest surface area, while the sample preheated in air has the lowest surface area. The CO 2 TPD profiles of the samples are also different, which implies that the samples have different surface basicity. From the desorbed amount of CO 2 and the desorption activation energy, it is found that the sample pretreated in vacuum has the most basic sites and the strongest basicity.     

后处理温度对Sol-Gel法制备的镍基负载型催化剂性能的影响

以正硅酸乙酯、钛酸丁酯、硝酸镍为原料,用Sol-Gel法制备得到超细镍基负载型催化剂前体NiO/TiO₂-SiO₂。采用BET、UV-Vis、FT-IR 、XRD、TPR等方法,研究了焙烧温度对催化剂前体物化性能及其催化剂活性（苯加氢生成环已烷反应）的影响。结果表明：用Sol-Gel 法制备得到的NiO/TiO₂-SiO₂的织构具有较高的热稳定性。随着焙烧温度的升高,比表面积、孔体积略有减少,表观堆密度增大。焙烧至92     

三维花状铜基复合物及其低温煅烧衍生物用于高效析氧反应

采用一种简单易行的方法来制备铜基电化学催化剂,该催化剂用于析氧反应。利用沸石咪唑酯骨架-67(ZIF-67)为前驱体,通过铜离子刻蚀合成新型铜基复合物(命名为Cu-NF)。它具有特殊的三维花状形貌和中孔结构,其形貌受铜离子与ZIF-67的质量比的影响。随后,Cu-NF经过低温煅烧处理,得到了不同温度下的衍生物,而煅烧过程并未改变其原始形貌。煅烧温度决定了活性物种的组成及含量,并增强了材料的多孔性。其中,300 ℃煅烧得到的产物Cu-NF-300具有最好的析氧反应性能：在 1.0 mol·L^-1 KOH 溶液中,过电位低达 347 mV,塔菲尔斜率为 93 mV·dec^-1。该材料电化学性能的提高归因于其三维结构以及低温煅烧所带来的活化作用。     

不同温度焙烧的Au-Pd/SiO2催化剂上甲醇选择性氧化制备甲酸甲酯

以溶胶固定法制备了Au-Pd/SiO₂催化剂,考察了催化剂焙烧温度对甲醇选择氧化制甲酸甲酯反应性能的影响。在200~500℃,400℃焙烧的Au-Pd/SiO₂具有最好的低温催化性能,在室温下就有活性,反应温度为100℃时甲醇转化率为25.3%,甲酸甲酯的选择性为100%。采用BET、XRD、UV-vis DRS、XPS、TEM和DRIFTS技术对催化剂进行表征,结果表明,催化剂中活性组分Au和Pd的高分散性,合适的Au和Pd粒径,Au-Pd合金的形成以及Au和Pd之间的强相互作用力,有利于甲醇氧化为甲酸甲酯反应的进行。初步推测出了甲醇在Au-Pd/SiO₂上氧化为甲酸甲酯的反应机理,甲醇在Au-Pd/SiO₂催化剂上是通过甲氧基中间体得到甲酸甲酯的。