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151.
152.
Alkaline peroxide mechanical pulping (APMP) of wheat straw with enzyme treatment was studied. Instead of direct enzyme pretreatment
on wheat straw, an alternative treatment method was used, in which coarse pulps from refiner defibrated wheat straw rather
than wheat straw were pretreated with a crude enzyme containing mainly xylanase, then impregnated with alkaline H2O2 solution and further refined. The optimum conditions of enzyme treatment were xylanase dosage of 10–15 IU/g of oven-dried
wheat straw, 90 min, 50–60°C, pulp consistency of 5–10%, and initial pH of 5.0, and those for chemical impregnation were 6%
NaOH, 70–80°C, 60–90 min, and 4 to 5% H2O2. Enzyme treatment improved pulpability of wheat straw by the APMP process, and final pulp quality such as brightness, breaking
length, and burst index of pulp. Pulp from the APMP process with enzyme treatment could be bleached to a brightness of 70.5%
ISO by two-stage H2O2 bleaching sequence with only 4% H2O2, and breaking length of the bleach pulp reached 4470 m. 相似文献
153.
Manganese dioxide modified carbon powder was prepared via a wet impregnation method from the solution of permanganate salt. After heating at 120 °C over night in air, the formation of manganese oxide was confirmed by cathodic stripping voltammetry. The synthesized material was used for fabrication of composite electrodes and their potential application in the field of electroanalysis investigated. The composite electrodes based on the manganese dioxide modified carbon powder proved to be useful as electrodes for detection of hydrogen peroxide, ascorbic acid and nitrite ions. 相似文献
154.
不同方法制备的Cu-Cr/γ-Al2O3的结构及其对糠醛加氢制2-甲基呋喃反应的催化性能 总被引:6,自引:0,他引:6
利用普通浸渍法、共沉淀法和溶剂化金属原子浸渍法制备了一系列Cu-Cr/γ-Al2O3催化剂,并用X射线衍射、扫描电镜、透射电镜和X射线光电子能谱等技术对这些催化剂进行了表征.结果表明,不同方法制备的催化剂的金属粒度的顺序为溶剂化金属原子浸渍法<共沉淀法<普通浸渍法;金属还原程度的顺序为溶剂化金属原子浸渍法>普通浸渍法≈共沉淀法.糠醛加氢反应实验结果表明,催化活性顺序为溶剂化金属原子浸渍法>普通浸渍法>共沉淀法;生成2-甲基呋喃选择性顺序为共沉淀法>普通浸渍法>溶剂化金属原子浸渍法. 相似文献
155.
156.
采用等容浸渍法引入少量CeO2助剂制备了CoMoSx/CeO2-γ-Al2O3催化剂。通过X射线衍射(XRD)、高角环形暗场像-扫描催化剂的形貌结构、还原性、吸附性能及反应过程等进行了表征,利用固定床反应器研究了其催化CO还原SO2的催化性能及稳定性。结果表明:少量CeO2的引入可以降低反应温度,随着CeO2含量的增加,CoMoSx/CeO2-γ-Al2O3催化剂的催化活性先增剂具有优异的稳定性;等容浸渍法制备的催化剂表面的金属元素分散良好;CeO2的引入提高了催化剂的硫化程度和低温还原进行。 相似文献
157.
Irena Zizovic Marcin Tyrka Konrad Matyja Ivana Moric Lidija Senerovic Anna Trusek 《Molecules (Basel, Switzerland)》2021,26(2)
This study investigates the modification of commercial cellulose acetate microfiltration membranes by supercritical solvent impregnation with thymol to provide them with antibacterial properties. The impregnation process was conducted in a batch mode, and the effect of pressure and processing time on thymol loading was followed. The impact of the modification on the membrane’s microstructure was analyzed using scanning electron and ion-beam microscopy, and membranes’ functionality was tested in a cross-flow filtration system. The antibiofilm properties of the obtained materials were studied against Staphyloccocus aureus and Pseudomonas aeruginosa, while membranes’ blocking in contact with bacteria was examined for S. aureus and Escherichia coli. The results revealed a fast impregnation process with high thymol loadings achievable after just 0.5 h at 15 MPa and 20 MPa. The presence of 20% of thymol provided strong antibiofilm properties against the tested strains without affecting the membrane’s functionality. The study showed that these strong antibacterial properties could be implemented to the commercial membranes’ defined polymeric structure in a short and environmentally friendly process. 相似文献
158.
Effects of impregnation sequence on the microstructure and performances of Cu-Co based catalysts for the synthesis of higher alcohols 下载免费PDF全文
Silica-supported CuCo catalysts were prepared by impregnation method with different impregnation sequence for higher alcohols synthesis. These catalysts were characterized by H2-TPR, XRD, N2 adsorption, XPS techniques and CO selective hydrogenation reaction measurement. The effects of impregnation sequence on the structure and performance of catalysts were investigated, and there were important influences on the selectivity to higher alcohols. There was a strong synergistic effect between copper and cobalt for the co-impregnated sample. The CuCo/SiO2 catalyst prepared by co- impregnation showed a better yield of total alcohols, and a higher selectivity to total alcohols which reached 51.5%. 相似文献
159.
Direct gas-phase epoxidation of propylene to propylene oxide using air as oxidant on supported gold catalyst 下载免费PDF全文
Gold catalysts supported on SiO2, TiO2, TiO2-SiO2, and ZrO2-SiO2 supports were prepared by impregnating each support with a basic solution of tetrachloroauric acid. X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques were used to characterize their structure and surface composition. The results indicated that the size of gold particles could be controlled to below 10 nm by this method of preparation. Washing gold catalysts with water could markedly enhance the dispersion of metallic gold particles on the surface, but it could not completely remove the chloride ions left on the surface. The catalytic performance of direct vapor-phase epoxidation of propylene using air as an oxidant over these catalysts was evaluated at atmospheric pressure. The selectivity to propylene oxide (PO) was found to vary with reaction time on the stream. At the reaction conditions of atmosphere pressure, temperature 325 ℃, feed gas ratio V(C3H6)/V(O2)= 1/2, and GHSV =6000h^-1, 17.9% PO selectivity with 0.9% propylene conversion were obtained at initial 10 min for Au/SiO2 catalyst. After reacting 60 min only 8.9% PO selectivity were detected, but the propylene conversion rises to 1.4% and the main product is transferred to acrolein (72% selectivity). Washing Au/TiO2-SiO2 and Aa/ZrO2-SiO2 samples with magnesium citrate solution could markedly enhance the activity and PO selectivity because smaller gold particles were obtained. 相似文献
160.
以柠檬酸三钠为稳定剂,硼氢化钠为还原剂,制备了碳载型的Pd-Sb复合纳米催化剂(Pd-Sb/C),通过调制不同Pd:Sb摩尔比研究了其对甲酸电催化性能的影响. TEM结果表明,合成的纳米颗粒粒径较小且均匀分散在碳载体表面. XRD和XPS测试表明,Pd-Sb/C中少量的单质态Sb(0)高度分散在Pd颗粒中或表面,形成合金化程度较低的PdSb合金. 电化学测试表明,当Pd:Sb = 20:1时,合成的催化剂对甲酸的催化效能最佳. 与合成的Pd/C和商业Pd/C相比,Pd-Sb/C(20:1)的电流密度分别是Pd/C的2.6倍、商业Pd/C的4.2倍. Pd-Sb/C的整体催化性能得到改善主要归因于适量的单质态Sb(0)引入到Pd中,诱导产生电子效应和“双功能”效应,一方面减小Pd与CO毒性物种之间的吸附作用,另一方面促使Pd表面吸附的CO快速氧化,提高了Pd-Sb/C催化剂的抗CO中毒能力,使得Pd-Sb/C催化剂的整体催化性能得到改善. 相似文献