排序方式: 共有31条查询结果,搜索用时 15 毫秒
11.
采用壳聚糖为基材、果胶为交联剂制备了薄膜材料,考察了卡拉胶和淀粉为添加剂对该薄膜材料力学性能的影响。结果显示,不加卡拉胶、淀粉的果胶-壳聚糖复合聚合物薄膜材料由于不溶于模拟胃液和模拟肠液,不适合单独作为缓释胶囊材料。当加入卡拉胶和淀粉后,不仅可进一步增加薄膜材料的柔韧性、凝胶性、透明度和力学性能,还增加其在模拟肠液和胃液中的溶解性。果胶-壳聚糖、卡拉胶、淀粉的质量比为2∶1∶1,得到的薄膜材料不仅具有良好的成型性和弹性,也具有适中的胃液和肠液溶解性。将该材料制备成胶囊,在模拟胃液和模拟肠液环境考察其破壁缓释效果,结果显示,胶囊在模拟胃液和肠液中的溶解是一个缓慢过程,浸泡6h后,胶囊药物的缓释率大致为93%。 相似文献
12.
13.
毒死蜱/羽毛蛋白/海藻酸钠复合微球的制备及其缓释性能 总被引:2,自引:0,他引:2
[目的]制备毒死蜱/羽毛蛋白/海藻酸钠复合微球。[方法]采用挤压法制备载药微球,利用傅立叶红外光谱仪、激光粒度仪、扫描电镜、差示扫描量热仪表征微球的化学组成、粒径分布、形貌结构以及毒死蜱的分布形态;并运用单因素法探讨羽毛蛋白用量、交联剂浓度、交联时间、离子浓度和p H值对微球溶胀率与载药量及缓释性能的影响。[结果]复合微球组分间以氢键和静电作用力结合,平均粒径750滋m,且分布均匀,表面光滑致密,毒死蜱以结晶形态分散于复合微球中。复合微球骨架的溶胀率和缓释速率与羽毛蛋白用量、交联剂浓度、交联时间、离子浓度和p H值均有关。[结论]载药复合微球的缓释行为表现出对离子浓度、p H值、温度的响应,有望在智能型微球方向取得应用。 相似文献
14.
纳米ZrO_2负载Ni催化剂催化CO选择性甲烷化 总被引:10,自引:3,他引:7
利用表面活性剂辅助模板机理,结合水热法合成出纳米有序的多孔 ZrO_2载体,采用等体积浸渍法制备了 Ni/ZrO_2催化剂;采用固定床微反装置评价了 Ni/ZrO_2催化剂对富氢气体中低含量 CO 选择性甲烷化反应的催化性能;采用 X 射线衍射和程序升温还原等方法对载体和催化剂进行了表征。实验结果表明,利用模板剂十六烷基三甲基溴化铵(CTAB)制备的 ZrO_2载体再负载质量分数4%Ni 的 Ni/ZrO_2催化剂具有优异的催化活性,可将 CO 体积分数从1.1%降至0.01%以下,且该催化剂在220~260℃内均能保持较高的活性和选择性。表征结果显示,以 CTAB 为模板剂制备的多孔性纳米 ZrO_2具备优良的载体性能,能促进活性组分 Ni 的分散,载体与活性组分 Ni 之间存在较强的相互作用,提高了催化剂的活性。 相似文献
15.
Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller (BET), transmission electron microscope (TEM), X-ray dif- fraction (XRD) and temperature-programmed reduction (TPR). The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% (by mass) Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low. 相似文献
16.
在超声作用下,假设亚油酸共轭反应为不可逆恒容反应,且反应一步完成的基础上,研究了碱催化亚油酸共轭反应的动力学。考察了反应物与催化剂的浓度、超声声强、温度对共轭反应速率的影响,并通过理论推导与试验拟合得到了各因素对反应速率常数影响的数学模型。结果表明,在超声作用下,碱催化亚油酸共轭反应符合宏观一级动力学特征;超声声强、反应物初始浓度、温度及催化剂浓度对反应速率的影响较大。在超声作用下反应的表观活化能为112.1 k J/mol,与常规相比,有所降低,这说明,超声作用可以使共轭反应进行得更快。试验同时显示,所得到的模型对试验结果的预测非常好,可用于超声作用下亚油酸共轭反应结果的预测。 相似文献
17.
18.
19.
Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst. 相似文献
20.