The reduction of nitrobenzene to aniline is very important for both pollution control and chemical synthesis.Nevertheless,difficulties still remain in developing a catalytic system having high efficiency and selectivity for the production of aniline.Herein,it was found that PdO nanoparticles highly dispersed on TiO_(2)support(PdO/TiO_(2))functioned as a highly efficient catalyst for the reduction of nitrobenzene in the presence of NaBH4.Under favorable conditions,95%of the added nitrobenzene(1 mmol/L)was reduced within 1 min with an ultra-low apparent activation energy of 10.8 kJ/mol by using 0.5%PdO/TiO_(2)as catalysts and 2 mmol/L of NaBH4 as reductants,and the selectivity to aniline even reached up to 98%.The active hydrogen specieswere perceived as dominant species during the hydrogenation of nitrobenzene by the results of isotope labeling experiments and ESR spectroscopic.A mechanismwas proposed as follows:PdO activates the nitro groups and leads to in-situ generation of Pd,and the generated Pd acts as the reduction sites to produce active hydrogen species.In this catalytic system,nitrobenzene prefers to be adsorbed on the PdO nanoparticles of the PdO/TiO_(2)composite.Subsequently,the addition of NaBH_(4) results in in-situ generation of a Pd/PdO/TiO_(2)composite from the PdO/TiO_(2)composite,and the Pd nanoclusters would activate NaBH_(4) to generate active hydrogen species to attack the adsorbed nitro groups.This work will open up a new approach for the catalytic transfer hydrogenation of nitrobenzene to aniline in green chemistry.
在施工项目领域,有效风险预测对于施工项目的顺利完成至关重要。针对传统风险预测模型难以实现非线性条件下的风险预测问题,提出了一种基于土拨鼠优化算法支持向量回归机(Prairie Dog Optimization Algorithm Optimizes Support Vector Regression Machine,PDO-SVR)的施工项目风险预测模型。该模型利用SVR强大的非线性预测能力,对施工项目的风险进行预测,针对人工选择SVR参数存在不合理的问题,利用PDO对SVR参数进行优化。实验结果表明,PDO-SVR模型具有更低的预测误差和良好的预测效果。
穿越地球时空研究计划(Cross Earth System Time and Space,CRESTS计划)将结合模式模拟与古气候资料,对过去130 ka的气候进行研究,以此对气候模式进行校验。太平洋年代际震荡(PDO)与大西洋多年代际震荡(AMO)作为全球年代际变化的主要模态,在全球气候变化研究中具有重要地位。目前已有不少古气候记录用于重建过去500—1000 a以来的PDO和AMO变化。作为CRESTS计划中的年代际气候变率重建的前期调研,汇总了目前已发表的PDO和AMO重建记录(以.xlsx格式存储),对这些记录的经纬度、载体类型、分辨率、指示意义等进行总结,以推动古PDO和AMO的重建研究。收集整理前人用于重建AMO与PDO的109条古气候记录,涉及的载体包括树轮、冰芯、珊瑚、硬海绵、历史文献、湖泊和深海沉积物。其中AMO重建的记录为77条,PDO重建的记录为32条。报告按照时间跨度、时间分辨率和重建内容对收集的记录进行分类整理。此外,还对前人重建结果的不确定性来源进行了总结。
