Selective catalytic reduction of NO with propene over Au/CeO2/Al2O3 catalysts

Selective catalytic reduction of NO by propene under an oxygen-rich atmosphere has been investigated over Au/ CeO₂, Au/CeO₂/Al₂O₃ and Au/Al₂O₃ catalysts prepared by deposition-precipitation. The results demonstrated that Au/16%CeO₂/Al₂O₃ had good low-temperature activity, selectivity towards N₂ and stability, which is superior to that of Pt/Al₂O₃. It was also found that adding 2% water vapour to the feed stream enhanced the NO conversions at low temperatures while the presence of 20 ppm SO₂ increased NO conversions at higher temperatures. It is particularly interesting that under the simultaneous presence of 2% water vapour and 20 ppm SO₂, the NO conversions to N₂ were significantly increased and the temperature window was widened significantly. The catalysts were characterized by Xray diffraction (XRD), high resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (HRTEM-EDX) and temperatureprogrammed reduction (H2-TPR) techniques. Both XRD and HRTEM revealed that CeO₂ was highly dispersed on the alumina support, and HRTEM combined with EDX showed that gold particles were preferentially deposited on those highly dispersed CeO₂ particles. The gold deposition made CeO₂ more reducible and interaction between gold and those highly dispersed CeO₂ particles became stronger than that with the bulk CeO₂, and this interaction is probably responsible for the superior catalytic performance of the Au/CeO₂/Al₂O₃.     

Optimal unit sizing for a hybrid wind/photovoltaic generating system

The application of a hybrid wind/photovoltaic (PV) power generating system for utilization as a stand-alone or a network connected system is investigated. The optimum combination of wind and PV generation coupled with battery storage for a stand-alone system has been obtained for a hypothetical site in Montana. Generation and storage units for the hybrid system are properly sized in order to meet the annual load and minimize the total annual cost to the customer. The optimal solutions are found by a numerical study using the hourly load demand for a typical residential home in the Northwestern US. Hourly wind speed and approximate solar radiation data have been used.     

3-羰基-4-氮杂-5-雄甾烯-17-肟衍生物的合成

4-氮杂类甾体化合物是一类比较重要的治疗良性前列腺增生、男性秃顶、女性多毛等症状的5α-还原酶抑制剂.以4-雄烯二酮为起始原料,经过氧化开环、氨解闭环、肟化、取代等4步反应,合成了3个新的3-羰基-4-氮杂-5-雄甾烯-17-肟衍生物7、8和9,并用质谱、1H NMR、13C NMR等测试手段对目标化合物的结构进行了表征.     

酵母悬浮液进料时膨胀床空隙率和粒径分布的动态变化

引言 膨胀床吸附技术可以直接从细胞破碎液(未澄清液)中提取目标产物[1-3],而无需预先进行固液分离操作,具有快速、高效和集成化的特点.在实际应用中,料液中细胞(碎片)的存在将会影响到膨胀床的床层稳定性和操作性能[4-6].     

在玻璃上合成有取向的silicalite-1分子筛膜及其生长机理

引言 分子筛膜具有规则的微孔结构、良好的化学和热稳定性,在气体分离、催化膜反应器、化学传感器以及分子筛改性电极等方面有广泛的应用前景[1-2],是催化和分离新材料领域的研究热点之一.     

逆向法确定色氨酸对映体竞争型吸附等温线

引言 吸附等温线测定是研究色谱分离过程的关键,其准确性直接影响到色谱分离过程的准确程度,因此,选择适当的实验方法和数学模型来模拟吸附等温线是模拟色谱分离过程的一个重要环节.常用的几种方法包括:前沿分析法、特征点洗脱法、特征点前沿分析法以及扰动法[1-2].其中前沿分析法是最常用的方法,该方法简单,准确性高,可用于多组分竞争型吸附等温数据的测定,但其数据采集过程非常耗时,对原料的需求量大,且需要考察单组分吸附等温模型与吸附数据的拟合程度.     

溶剂对对苯二酚晶体晶习的影响

采用冷却结晶方法,考察了水、甲醇、乙醇、正丙醇、异丙醇和正丁醇等溶剂对对苯二酚晶习的影响,并通过扫描电镜、差热扫描分析、X射线衍射等手段对对苯二酚晶体进行了分析表征.结果表明,溶剂性质显著影响对苯二酚晶体的晶习,随着溶剂介电常数的减小,晶体的长径比变小.在利用分子模拟软件Cerius²预测对苯二酚晶体晶习的基础上,初步揭示了溶剂影响对苯二酚晶体晶习的机理.     

汽-液-固流动沸腾系统混沌时间序列的遗传算法全局建模

与系统的平均特性建模研究相比,系统的时间序列建模工作更富挑战性,也更具有意义.最近的研究表明,汽-液-固三相流动沸腾系统的动力学行为具有混沌特征,因此,本文从非线性视角出发,开展系统物理量的时间序列建模研究.根据实验测得的反映系统非线性演化信息的汽-液-固三相流动沸腾系统的壁温时间序列数据,采用遗传算法全局建模方法,建立了描述该系统非线性动力学行为的时间序列迭代形式的数学模型,并将模型计算结果与实验数据进行了比较.结果表明,采用遗传算法全局建模方法所建立的模型,能够较好地描述汽-液-固三相流动沸腾系统的非线性动力学行为,模型计算值与实验数据吻合良好.     

Diffusion controlled photocurrent transients at the surface of thin polycrystalline n-TiO2 layers

Within the pH-range of 5 to 11 thermally-produced n-TiO₂ photoanodes exhibit a complex picture of diffusion controlled photocurrent transients (PT). These diffusion effects seem to be enhanced by the rough and structured surface of thermally produced n-TiO₂ electrodes. The characteristic of PT is interpreted as local pH-shifts at the electrode surface and photooxidation of reduced surface states (HO₂, H₂O₂).     

阻燃剂四溴双酚S双烯丙基醚的制备研究

在NaOH水溶液中,以四溴双酚S(TBS)为原料,通过滴加的方式加入醚化剂烯丙基氯,用季铵盐催化醚化法和其他表面活性剂醚化法成功地合成了收率、纯度均较高的阻燃剂四溴双酚S双烯丙基醚(ATBS)。研究了催化剂用量、反应时间、烯丙基氯用量及其他因素对ATBS收率及纯度的影响情况,找到了反应的最优化条件。季铵盐催化醚化法和其他表面活性剂醚化法的最佳收率分别为97·55%和95·21%,相应纯度为95·57%和93·96%。