Effects of alkaline-earth strontium on the performance of Co/Al_2O_3 catalyst for methane partial oxidation

联系作者: 余长林( 1974-) ，湖南炎陵人，男，博士，副教授。主要从事纳米催化新材料研究。Tel: 0797-8312334; E-mail: [email protected]。 本文的英文电子版由Elsevier 出版社在ScienceDirect 上出版( http: / /www.sciencedirect． com /science /journal /18725813) 。[中文文摘]以γ-Al2O3为载体,采用共浸渍法制备了Sr-Co/Al2O3系列催化剂,研究了助剂Sr对Co/Al2O3催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N2物理吸附、X射线衍射、H2-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al2O3和800℃焙烧的Sr-Co/Al2O3催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H2还原为单质的Co3O4;另一类是与载体相互作用较强、难还原、无催化活性的CoAl2O4尖晶石。在焙烧过程中,Sr易形成Sr4Al14O25,从而削弱Co与Al2O3之间的相互作用,能在一定程度上抑制CoAl2O4物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al2O3在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl2O4的产生。[英文文摘]A series of Sr-Co/Al2O3 catalysts were prepared by co-impregnation method using γ-Al2O3 as the support.The effect of strontium promoter on the catalytic performance of Co/Al2O3 catalyst for partial oxidation of methane(POM) to synthesis gas was studied.The catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption,X-ray diffraction(XRD),H2-temperature programmed reduction(H2-TPR) and thermogravimetry(TG).The results show that both Co/Al2O3 calcined at 700 ℃ and Sr-Co /Al2O3 calcined at 800 ℃ exhibit low activity and deactivate at the initial stage of POM reaction.The addition of above 2% mass fraction of strontium will greatly enhance the activity and stability of Co /Al2O3.Two types of Co species were identified on the fresh calcined catalysts.One is Co3O4 which weakly interacts with Al2O3 (easily reduced by H2) and the other is the spinel CoAl2O4 ( non-catalytic performance) which strongly interacts with the support.During the course of calcination，strontium can react with Al2O3 to form Sr4Al14O25 which will restrain the generation of the CoAl2O4 species and promote the stability and activity of catalysts．Without strontium promoter，CoAl2O4 is easy to be formed over Co /Al2O3 in the POM reaction.However，the formation of CoAl2O4 cannot be avoided with the addition of limited strontium when the calcination temperature is over 800 ℃．国家自然科学基金(21067004,21263005); 厦门大学固体表面物理化学国家重点实验室开放基金(200906);; 江西省自然科学基金(2010-GZH0048); 江西省教育厅科技项目(GJJ12344); 江西省青年科学家培养对象资助(20122BCB23015

Preparation of Co/Ce_(0.5)Zr_(0.5)O_2 catalysts and their catalytic performance in methane partial oxidation to produce synthesis gas

联系作者: 余长林( 1974-) ，湖南炎陵人，男，博士后，副教授，主要从事纳米催化新材料研究，Tel: 0797-8312334; E-mail : yuchanglinjx@ 163． com。 本文的英文电子版由Elsevier 出版社在ScienceDirect 上出版( http: / /www． sciencedirect． com /science /journal /18725813) 。[中文文摘]利用共沉淀法制备了具有介孔结构的Ce0． 5Zr0.5O2 固溶体载体，然后浸渍不同质量分数(10%、20%、30%) 的活性组 分钴，制备了系列Co/Ce0.5Zr0.5O2 催化剂。利用N2 物理吸附(BET) 、X 射线粉末衍射( XRD) 、H2-程序升温还原(H2-TPR)、扫 描电子显微镜( SEM) 、透射电子显微镜( TEM) 、程序升温氧化( TPO) 和热重(TG) 等手段对制备和反应后的催化剂进行了 表征，研究了它们对甲烷部分氧化制合成气反应的催化性能。研究结果表明，铈锆固溶体负载的钴比较容易被还原，该系列 催化剂具有较高的活性和对H2 及CO 的选择性，且随Co含量的增加，催化剂的活性和对H2和CO 的选择性得到提高的同时， 也增强了催化剂的抗积炭性能。[英文文摘]Porous Ce0． 5 Zr0． 5 O2 solid solution support was first prepared by a co-precipitation method． Then， different concentrations of Co ( 10%，20%，and 30 %) were loaded over Ce0． 5Zr0． 5O2 by impregnation process． The fresh catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption (BET) ，X-ray diffraction(XRD) ，temperature-programmed reduction of hydrogen ( H2-TPR) ，scanning electron microscopy (SEM) ，and transmission electron microscopy (TEM) ．The amount of deposited carbon over used catalysts was analyzed by temperature-programmed oxidation of oxygen (O2-TPO) and thermogravimetry(TG) ．The catalytic performance of these Co /Ce0．5Zr0．5O2 catalysts was evaluated by methane partial oxidation to produce synthesis gas． The results show that cobalt oxide is easy to be reduced to metal cobalt over Ce0． 5Zr0． 5O2 ． This series of Co/Ce0．5 Zr0．5O2 catalysts show high activity and selectivity to H2 and CO． It was found that loading high concentration of Co could benefit the increase in catalytic activity and ability to resist the coke．基金项目: 国家自然科学基金( 21067004) ; 厦门大学固体表面物理化学国家重点实验室开放基金( 200906) ; 江西省自然科学基金( 2010- GZH0048) ; 江西省教育厅科技项目( GJJ12344)

A STUDY ON NANO-HYDROXYAPATITE-CHITOSAN SCAFFOLD FOR BONE TISSUE ENGINEERING

作者单位: 1 中国医学科学院中国协和医科大学生物医学工程研究所天津市生物医学材料重点实验室( 天津, 300192 ) ; 2 厦门大学生物医学工 程研究中心厦门大学医学院厦门市生物医学工程技术研究中心 通讯作者: 张其清, 教授, 博士导师, 研究方向: 组织引导再生, E-mail: zhangqiq@ xmu . edu. cn[中文文摘]目的以一种简单、有效的方法制备多孔的纳米羟基磷灰石(nano hydroxyapatite,nano-HA)-壳聚糖(chitosan,CS)复合支架,并评价其理化性能及与细胞相容性。方法采用原位复合-冷冻干燥方法,制备多孔nano-HA-CS支架。通过扫描电镜、透射电镜、X线衍射和傅立叶红外光谱分析支架的微观形貌及材料的组成。分离初生Wistar大鼠的成骨细胞,取传代培养第3代细胞分别与nano-HA-CS支架和纯CS支架共培养2、4、6、8h,各时间点各取4个样品,测定细胞在支架上的黏附率,并通过组织化学染色、扫描电镜观察细胞形态。结果nano-HA-CS复合支架具有多孔结构,孔径为100~500μm,大多数孔径为400~500μm。具有很高的孔隙率,随CS和HA含量的增加,孔隙率明显降低,密度升高。扫描电镜和透射电镜观察显示合成的HA晶体,晶粒大小为纳米级,在支架孔壁上均匀、连续分布如“铺路石”样。X线衍射和红外光谱分析表明合成的HA是含CO32-弱结晶纳米晶体。细胞相容性实验显示,成骨细胞在支架上黏附、增殖,并分泌纤维状细胞外基质;在复合支架上的黏附率明显高于纯CS支架。结论采用原位复合与冷冻干燥法结合制备的nano-HA-CS复合支架具有良好的理化性质和细胞相容性,有望应用于组织工程骨的构建。[英文文摘] Objective To fabricate a nano-hydroxyapatite-chitosan (nano-HA-CS) scaffold with high porosity by a simple and effective technique and to evaluate the physical and chemical properties and the cytocompatibility of the composite scaffold. Methods The three-dimensional nano-HA-CS scaffolds with high porosity were prepared by the in situ hybridization-freeze-drying method. The microscopic morphology and components of the composite scaffolds were analyzed by the scanning electron microscopy (SEM), the transmission electron microscopy(TEM), the X-ray diffraction(XRD)examination, and the Fourier transformed infrared spectroscopy(FTIR). The calvarial osteoblasts were isolated from the neonatal Wistar rats. The serial subcultured cells (3rd passage) were respectively seeded onto the nano-HA-CS scaffold and the CS scaffold, and then were co-cultured for 2, 4, 6 and 8 hours. At each time point, four specimens from each matrix were taken to determine the cell-adhesion rate. The cell morphology was observed by the histological staining and SEM. Results The macroporous nano-HA-CS scaffolds had a feature of high porosity with a pore diameter from 100 to 500 μm (mostly 400-500 μm). The scaffolds had a high interval porosity; however, the interval porosity was obviously decreased and the scaffold density was increased with an increase in the contents of CS and HA. The SEM and TEM results showed that the nano-sized HA was synthesized and was distributed on the pore walls homogeneously and continuously. The XRD and FTIR results showed that the HA crystals were carbonate-substituded and not well-crystallized. The cytocompatibility test showed that the seeded osteoblasts could adhere the scaffolds, proliferating and producing the extracellular matrix on the scaffolds. The adherence rate for the nano-HA-CS scaffolds was obviously higher than that for the pure CS scaffolds. Conclusion The nano-HA-CS scaffolds fabricated by the in situ hybridization-freeze-drying method have a good physical and chemical properties and a good cytocompatibility; therefore, this kind of scaffolds may be successfully used in the bone tissue engineering.天津市科技攻关项目资助项目(05YFGZGX03800

A Study on Gaze Pattern Variability and Machine Learning Classification in Children with Autism Spectrum Disorder Under Different Social Intentions

孤独症谱系障碍（Autism Spectrum Disorder，ASD）是一种复杂的神经发育障碍，其核心特征包括社交互动和沟通能力障碍，以及刻板的重复行为。这些特征不仅影响个体的日常生活，也对家庭和社会造成了深远的影响，早期精准的诊断和干预对于改善 ASD 儿童的生活质量至关重要。 本研究采用眼动追踪技术结合机器学习算法，通过对4至9岁实验组（56 名 ASD 儿童）与对照组（50 名典型发育儿童，Typical Developing，TD 儿童）在观看含有&ldquo;联合意图&rdquo;和&ldquo;非联合意图&rdquo;社交场景时的注视模式差异及其个体内注视模式的变异性进行研究，探究注视模式与动作预测和意图理解等社交认知能力之间的潜在关联。进一步，利用机器学习算法对眼动数据进行分类分析，旨在提高 ASD 的诊断准确性和识别效率，以期为 ASD 儿童的早期干预提供科学依据和技术支持。 研究结果显示，ASD 儿童在关键社会性线索区域（如眼睛和面部）的注视时间与注视频率显著低于 TD 儿童，而对&ldquo;背景&rdquo;等非社会性区域的注视则相对增多。这种差异在非联合意图条件下更为显著，反映了 ASD 儿童在处理模糊社交线索时的困难。此外，ASD 儿童的个体内注视模式变异性与任务相关区域的注意力分配呈负相关，而与人物非相关区域的注意力分配呈正相关，揭示了非典型注意力分配与社交认知功能之间的密切联系。 采用决策树、k 最近邻等 5 种机器学习算法，基于眼动数据进行 ASD 分类 的准确率超过 80%，证实了机器学习在 ASD 分类中的有效性。进一步对特征提 取、特征重组和兴趣区划分等关键技术进行了研究，旨在提升 ASD 分类准确性和分类模型的泛化能力。研究证实了基于视觉注视的眼动指标进行特征组合的方法能够大幅提升 ASD 分类准确率，尤其是在决策树分类器中，其准确率达到了91.4%，表现出卓越的分类性能。此外，本研究还探讨了基于数据驱动后验兴趣区划分的机器学习分类效果，发现兴趣区数量与分类性能并无直接正相关。这表明在机器学习模型中，样本量选择、特征选择和模型训练过程优化的重要性超过了单纯增加兴趣区的数量。 本研究不仅增进了对 ASD 儿童社交障碍认知基础的理解，还为早期诊断与干预提供了潜在的生物标志物，具有重要的实践意义。未来研究将进一步探索视 觉注视模式与社交认知功能之间的复杂关系，并优化机器学习算法，以提高 ASD 分类的准确性和泛化能力。</p