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以罗丹明B(RhB)为碱性染料代表,研究掺杂稀土元素Ce的纳米ZnO(Ce-ZnO催化剂)的光催化性能,优化催化反应条件。结果表明:掺杂Ce有效地提高了纳米ZnO催化降解RhB效果,选取催化剂用量、催化时间和Ce掺杂比进行三因素三水平正交实验,得出自然光下Ce-ZnO催化降解5 mg/L RhB的最优条件为催化剂用量50 mg/50ml、催化时间90 min、Ce掺杂比2%。在最优催化条件下,Ce-ZnO对浓度为5 mg/L的RhB催化降解率接近90%。 相似文献
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[目的]进行丙酸香叶酯的合成并优化合成条件。[方法]在敞开体系中合成中孔分子筛Al-MCM-41。通过X射线衍射(XRD)、红外光谱(FT-IR)、NH3程序升温脱附(NH3-TPD)、N2吸附-脱附和气相色谱(GC)等方法对所合成样品的结构和催化性能进行表征分析。用其催化合成丙酸香叶酯,考察了反应时间、反应温度、催化剂用量、反应物配比及催化剂再生对香叶醇酯化反应结果的影响。[结果]合成的样品具有中孔分子筛的六方介孔结构以及良好的长程有序性和结晶度,属于典型的中孔材料,分子筛表面有弱酸中心。最佳的反应条件是n(香叶醇)/n(丙酸)=1.0∶1.5,反应温度为120℃,反应时间为8h,但香叶醇的转化率仅为40.01%,丙酸香叶酯的选择性为70.01%。催化剂使用到第5次时有失活现象,可通过焙烧除去掩盖酸中心的积碳,使催化剂的活性和选择性得到恢复。[结论]得到了丙酸香叶酯的合成优化条件,为进一步研究奠定基础。 相似文献
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以十六烷基三甲基溴化铵为模板,硅酸钠为硅源,采用微波辐射方法合成出了Zr-MCM-41分子筛,将其在硫酸溶液中浸渍得到了具有酸催化作用的SO42-/Zr-MCM-41分子筛,用于催化合成乳酸乙酯.探讨了对乳酸乙酯收率的各影响因素.结果表明:催化剂锆硅摩尔比为0.05,在100℃条件下微波晶化2.5h,焙烧温度550℃,酯化产率86.2%.催化剂重复使用4次后再活化使用,产率仍达80%以上,且易分离,不污染环境. 相似文献
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通过湿式机械混合法制备系列TiO2/ZnO复合催化剂,并向其中掺杂不同金属离子.以甲基橙为模拟污染物进行光催化降解实验,结果表明复合催化剂中TiO2和ZnO的最佳配比为60%~80%;在分别掺杂含量为10-4 mol/g的Ag+,Zr4+,Sn4+离子后催化活性有明显提高;焙烧活化处理温度对掺杂不同金属离子催化剂活性有不同的影响. 相似文献
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通过湿式机械混合法制备系列TiO2/ZnO复合催化剂,并向其中掺杂不同金属离子.以甲基橙为模拟污染物进行光催化降解实验.结果表明复合催化剂中TiO2和ZnO的最佳配比为60%-80%;在分别掺杂含量为10^-4mol/g的Ag^+,Zr^4+,Sn^4+离子后催化活性有明显提高;焙烧活化处理温度对掺杂不同金属离子催化剂活性有不同的影响。 相似文献
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Tubular aluminophosphate molecular sieve crystals were grown at an organic interface with their channels (7 angstroms in cross section) vertical to the substrate. To induce surface nucleation and oriented growth of AIPO(4)-5 crystals, organophosphonate layers cross-linked with Zr(IV) were assembled on a gold substrate and the modified substrate was immersed in a hydrothermal bath containing reagents for the synthesis of the molecular sieve. Reflection-absorption infrared studies demonstrated the stability of the phosphonate layers under these conditions. Drastic changes in the morphology of the surface-grown crystals from spherical agglomerates to vertical needles to thin tilted needles could be achieved by adjusting the water content of the synthesis bath. Nitrogen sorption in these structures on a piezoelectric device confirmed the presence of zeolitic microporosity. 相似文献
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选用5A分子筛、13X分子筛和硅胶作为吸附剂,采用变压吸附法进行脱除沼气中CO2试验,考察不同的吸附压力条件下CH4/CO2分离的效果,并对三种吸附剂的吸附性能进行分析和比较.结果表明,5A分子筛在0.7 Mpa下脱除CO2效果最好,获得CH4含量最大为90%~92%.5A分子筛在流量22.1 L·min-1的穿透时间约为200 s,获得CH4浓度最大,平均纯度为83.5%;脱附时间为560 s,再生效果较好 相似文献
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Sodium silicoglycolate, an organosilicon compound in which silicon is in 5-coordination with respect to oxygen, is shown to be a reaction intermediate in the synthesis of a purely siliceous sodalite with ethylene glycol as solvent. The presence of silicon-29 nuclear magnetic resonances at -105.5 +/- 0.3 parts per million in solution and -102.7 parts per million in the solid state as well as x-ray powder diffraction patterns demonstrate that 5-coordinate silicon is intimately involved in the synthesis. Silicon compounds of the 5-coordinate type are highly reactive and are promising starting materials for the synthesis of novel silicone polymers, molecular sieves, glasses, semiconductors, and ceramics. We have used sodium silicoglycolate to prepare the molecular sieve silicalite as well as sodalites of different compositions. 相似文献
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Varoon K Zhang X Elyassi B Brewer DD Gettel M Kumar S Lee JA Maheshwari S Mittal A Sung CY Cococcioni M Francis LF McCormick AV Mkhoyan KA Tsapatsis M 《Science (New York, N.Y.)》2011,334(6052):72-75
Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes. 相似文献
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[目的]对介孔分子筛固定化海藻糖合酶进行研究。[方法]以基因工程菌所产海藻糖合成酶为材料,利用介孔分子筛MCM-41作为载体固定化海藻糖合成酶,并对固定化条件和固定化前后的海藻糖合酶性质进行比较研究。[结果]海藻糖合成酶可通过物理吸附法固定于介孔分子筛MCM-41孔道中,在pH为3,给酶量为62.5 mg/g的条件下,固定12 h时可得到最佳固定化效果;与游离海藻糖合酶相比,固定化后的海藻糖合酶pH稳定性和热稳定性明显改善,并具可重复操作性,有利于酶的使用和储放。[结论]该研究为开发新的固定化海藻糖合成酶提供了理论依据。 相似文献
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微波辐射硫酸氢钠催化合成乙酸异戊酯研究 总被引:1,自引:0,他引:1
在微波辐射下,以NaHSO4·H2O作催化剂,4A分子筛作脱水剂,以冰醋酸和异戊醇为原料合成乙酸异戊酯.当微波辐射功率为255W,以0.1mol冰醋酸为基准,催化剂用量为0.3g,酸醇的摩尔比为1∶1.5,反应时间20min时,酯化率达99.2%. 相似文献
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《Science (New York, N.Y.)》1990,247(4947):1167
The cover caption for the issue of 9 February 1990 should have described the molecule on the cover as VPI-5 (Dow and Virginia Polytechnic Institute), not as ALPO-5 (Union Carbide). The first sentence of the caption should have read, "Superlattices of p-nitroaniline molecules self-assemble and orient within the polar, greater than 10 angstrom wide channels of VIP-5, a molecular sieve." The preferred orientation of the polar molecules occurs in both materials. 相似文献
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de Jong JJ Lucas LN Kellogg RM van Esch JH Feringa BL 《Science (New York, N.Y.)》2004,304(5668):278-281
In nature, key molecular processes such as communication, replication, and enzyme catalysis all rely on a delicate balance between molecular and supramolecular chirality. Here we report the design, synthesis, and operation of a reversible, photoresponsive, self-assembling molecular system in which molecular and supramolecular chirality communicate. It shows exceptional stereoselectivity upon aggregation of the molecules during gel formation with the solvent. This chirality is locked by photochemical switching, a process that is subsequently used to induce an inverted chiral supramolecular assembly as revealed by circular dichroism spectroscopy. The optical switching between different chiral aggregated states and the interplay of molecular and supramolecular chirality offer attractive new prospects for the development of molecular memory systems and smart functional materials. 相似文献
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以高效纤维素分解菌桔青霉(Penicillium citrinum)CR-2菌株为材料,利用分子筛及离子交换技术纯化分离其内切葡聚糖酶蛋白,首次获得了电泳纯的桔青霉内切葡聚糖酶蛋白组分,大小为27.26 kDa,最适作用温度为60℃,最适作用pH为5。对研究桔青霉纤维素酶降解纤维素的作用机理以及该菌株的改造应用具有重要意义。 相似文献