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用固体超强酸 SO2 - 4 /Ti O2 为催化剂 ,以尿素和乙醛酸为原料合成了尿囊素。得到最佳条件为 :Ti O2 在 1mol.L- 1 H2 SO4溶液中浸渍 12 h,再在 6 0 0℃焙烧 3h;尿素与乙醛酸摩尔比 3.5 :1,催化剂 9% ,时间 3h,温度 72℃~ 75℃ ,产率达5 7.4% 相似文献
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固体超强酸SO2-4/TiO2-SiO2催化合成马来酸二辛酯 总被引:6,自引:0,他引:6
用H2SO4浸渍钛硅复合氧化物,制得固体超强酸SO4^2-/TiO2-SiO2,考察了催化剂对马来酸酐与正辛醇的酯化反应的催化作用及其制备条件对催化剂活性的影响,并与硫酸,对甲苯磺酸的催化效果比较,结果表明,对于给定反应,当n(Ti):n(Si)为15:1,用浓度0.6mol/L的硫酸浸渍8h,在550℃下焙烧3h时制得的催化剂SO4^2-/TiO2-SiO2具有最高的催化活性,用以催化马来酸酐和正辛醇的酯化反应,可得无色透明的酯化产物,3h内酯化率达99.1%,较SO4^2-/TiO2催化剂的酯化率提高了约6%。 相似文献
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固体超强酸TiO2/SO42-催化合成α-萘乙酸甲酯 总被引:3,自引:0,他引:3
以固体超强酸TiO2/SO4^2-为催化剂,研究了α-萘乙酸与甲醇的酯化反应,探讨了催化剂种类、用量及活化温度等反应条件,发现固体超强酸TiO2/SO4^2-对α-萘乙酸与甲醇的酯化反应具有较高的催化活性,并使后处理简化。较佳反应条件为:α-萘乙酸与甲醇的摩尔比为1:5.3,固体超强酸TiO2/SO4^2-活化温度为450℃~500℃,活化时间3h,用量为α-萘乙酸用量的3%,反应时间6h,反应温度74.5℃~76℃。在试验筛选的最佳条件下,酯产率超过96%,精酯收率达83%。 相似文献
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催化合成新型十六烷值改进剂草酸二正丁酯 总被引:7,自引:0,他引:7
采用直接浸渍-焙烧法制备了SO4^2- - TiO2/Al2O3新型固体超强酸催化剂(简称SO4^2- - TiO2/Al2O3催化剂),用Hammett指示剂法测定了SO4^2- - TiO2/Al2O3催化剂的酸强度;以草酸和正丁醇为原料合成了新型柴油十六烷值改进剂-草酸二正丁酯。考察了SO4^2- - TiO2/Al2O3催化剂的焙烧温度、TiO2负载量、SO4^2- - TiO2/Al2O3催化剂用量、原料配比、回流时间、带水剂甲苯用量对反应的影响。最佳的反应条件为:TiO2负载量(质量分数)10%、SO4^2- - TiO2/Al2O3催化剂焙烧温度500℃、催化剂用量为反应物料总质量的4.0%、n(正丁醇):n(草酸)=2.4:1、带水剂甲苯20mL、回流时间1.5h;在最佳反应条件下,草酸二正丁酯的收率可达99.3%,产品的纯度为99.6%。 相似文献
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用H2 SO4浸渍钛硅复合氧化物 ,制得固体超强酸SO2 -4/TiO2 -SiO2 ,考察了催化剂对马来酸酐与正辛醇的酯化反应的催化作用及其制备条件对催化剂活性的影响 ,并与硫酸、对甲苯磺酸的催化效果比较。结果表明 :对于给定反应 ,当n(Ti)∶n(Si)为 15∶1、用浓度 0 .6mol/L的硫酸浸渍 8h、在 5 5 0℃下焙烧 3h时制得的催化剂SO2 -4/TiO2 -SiO2 具有最高的催化活性 ;用以催化马来酸酐和正辛醇的酯化反应 ,可得无色透明的酯化产物 ,3h内酯化率达 99.1% ;较SO2 -4/TiO2 催化剂的酯化率提高了约 6 % 相似文献
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利用硫酸钡重量法对SO4^2-/TiO2^-MoO3-La2O3固体超强酸催化剂中的硫含量进行了分析。实验结果表明,随着焙烧温度的升高,SO4^2-/TiO2^-MoO3-La2O3催化剂存在一个S04z一的快速流失温度区。原料配比n(La^3 )/n(Ti^4 ),MoO3的含量、硫酸浸泡浓度、硫酸浸泡时间、焙烧温度和活化时间等制备条件对SO4^2-/TiO2^-MoO3-La2O3催化剂中的硫含量都存在较大的影响。SO4^2-/TiO2^-MoO3-La2O3催化剂的适宜制备条件为:原料配比n(La^3 )/n(Ti^4 )为1/34,MoO3的含量25%,硫酸浸泡浓度0.5mol/L,硫酸浸泡时间24h,焙烧温度450℃,活化时间3h。 相似文献
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In glasses with the compositions (100 ? x)(2Na2O·16K2O·8Al2O3·74SiO2)xBaF2 (with x = 0 to 6), the glass transition temperature decreases with increasing BaF2-concentration. Samples with x = 6 were thermally treated at temperatures in the range from 500 to 600 °C for 5–160 h. This leads to the crystallisation of BaF2. The quantity of crystalline BaF2 increases with increasing time of thermal treatment, while the mean crystallite size remains constant within the limits of error. The glass transformation temperature of partially crystallised samples increases with increasing crystallisation time and approaches a value equal to the temperature, at which the samples were treated. This is explained by the formation of a highly viscous layer enriched in SiO2 which is formed during crystallisation. This layer acts as a diffusion barrier and hinders further crystal growth. 相似文献
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复合固体超强酸SO42-/ZrO2-Al2O3催化合成乳酸正丁酯的研究 总被引:12,自引:0,他引:12
《化学试剂》2001,23(5):269-270
合成了几种不同Zr、Al原子比的SO42-/ZrO2-Al2O3复合固体超强酸,将其用于催化乳酸与正丁醇的酯化反应,均有较好的催化活性,尤以ZrAl=12的催化效果最好,经济性优于ZrO2超强酸催化剂.其最佳反应条件为酸醇摩尔比为13,催化剂用量为乳酸质量的10%,反应时间2~2.5h,酯化率达96.9%.该催化剂具有制备容易、催化活性高、不污染环境、可重复使用的优点. 相似文献
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Paul Wencil Brown 《Journal of the American Ceramic Society》1990,73(11):3457-3461
A portion of the quaternary phase diagram for Na2 O-CaO-SiO2 -H2 O has been constructed. Plotting concentrations as their 10th roots allows compounds having solubilities which differ by several orders of magnitude to be represented on a single diagram. The compositional relationships among sodium-substituted calcium silicate hydrate, calcium-substituted sodium silicate hydrate, calcium bydroxide, a quaternary compound of approximate composition 0.25Na2 O · CaO · SiO2 · 3H2 O, sodium hydroxide monohydrate, and miscellaneous sodium silicate hydrates are presented. The quaternary diagram constructed shows the quaternary compound to exist in equilibrium with sodium-substituted calcium silicate hydrate and calcium hydroxide. Conditions in concrete pore solutions which favor the formation of this quaternary compound may also favor the occurrence of the alkali-silica reaction. 相似文献
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In earlier work, a prediction method of the immiscibility boundary of a ternary silicate glass system was developed involving two known binary immiscibility boundaries and a measured immiscibility temperature of one ternary glass composition. In the present work, the method is extended to the case where one of the two binary immiscibility boundaries is not known and is applied as an example to ternary silicate systems containing K2 O. First, the immiscibility boundary of the system K2 O-SiO2 is estimated by measuring the immiscibility temperatures of three glasses in the system K2 O-Li2 O (or Na2 O)-SiO2 . Using this result the immiscibility boundaries of the systems K2 O-Li2 O-SiO2 , K2 O-Na2 O-SiO2 , and K2 O-BaO-SiO2 are estimated. The results agree reasonably well with the experimentally determined immiscibility temperatures at selected compositions. 相似文献
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BURNHAM W. KING 《Journal of the American Ceramic Society》1954,37(5):238-242
It was first shown that the enamel slips which have the best suspnding characteristics contain equal amounts of Na2 O and B2 O3 and at least a moderate amount of NaF. The solubilities of mixtures of Na2 O, NaF, and B2 O3 were then investigated. The pH of these solutions and the primary crystalline phases separating on evaporation also were determined. The solubility data obtained at room temperature were summarized. When the solutions were evaporated, NaF was the first crystalline phase to separate from a large proportion of the mixtures investigated. It was concluded that the desirable handling characteristics of enamels whose mill liquors contain the proper proportion of Na2 O, NaF, and B2 O3 are not due to the formation of complex salts but to the following combination of properties: (1) the presence of salts with a moderate solubility which changes very slightly with temperature, (2) a moderate pH of about 10 in a probably well-buffered solution, (3) a relatively stable crystalline material, NaF, as a primary phase, and (4) a secondary phase which crystallizes slowly with relatively little shrinkage. 相似文献
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Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu2O, Bi2O3 and ZnMn2O4 are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu2O/TiO2 and Bi2O3/TiO2 by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed. 相似文献
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Equilibrium phase diagrams for the systems MgCl2 -MgF2 , CaCl2 -MgF2 and NaCl-MgF2 were determined by differential thermal analysis, thermal analysis, and temperature-composition equilibrium techniques. Simple eutectics were observed at 78.0±0.5 mol% MgCl2 and 628°±2°C in the MgCl2 -MgF2 system, at 87.5±0.5 mol% CaCl2 and 694°±2°C in the CaCl2 -MgF2 system, and at 95.5±0.5 mol% NaCl and 786°±3°C in the NaCl-MgF2 system. The phase diagrams determined for these systems were compared with phase diagrams that were computed using Temkin's model. The phase diagrams of the CaCl2 -MgF2 and NaCl-MgF2 systems were also compared with diagrams that were computed using the expression suggested by Flood et al. for reciprocal systems. The experimentally determined and computed phase diagrams agreed for the MgCl2 -MgF2 system but not for the CaCl2 -MgF2 and NaCl-MgF2 systems. 相似文献
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Yong Sig Ko 《Powder Technology》2004,145(1):10-19
Zeolite L powder was prepared from the substrate mixture of Na2O-K2O-Al2O3-SiO2-H2O system at temperatures of 373-443 K. In order to investigate the factors which influence the synthesis outcome, a reference system which yields zeolite L in a reproducible manner was chosen and subjected to controlled changes in synthesis parameters. The crystalline zeolite L samples obtained were characterized by elemental chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was established that phase purity, morphology, and the size of crystals of crystalline product were affected by molar ratios of the substrate, such as SiO2/Al2O3, (K2O+Na2O)/SiO2, Na2O/(K2O+Na2O), and H2O/(K2O+Na2O). Amorphous silica powder (Zeosil) was the preferred silica source, and the crystallization rate was promoted by introducing gel aging, seeding, and rapid heating rate. 相似文献
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Activity and selectivity of selective CO oxidation in an H2-rich gas stream over Co3O4/CeO2/ZrO2, Ag/CeO2/ZrO2, and MnO2/CeO2/ZrO2 catalysts were studied. Effects of the metaloxide types and metaloxide molar ratios were investigated. XRD, SEM, and N2 physisorption techniques were used to characterize the catalysts. All catalysts showed mesoporous structure. The best activity was obtained from 80/10/10 Co3O4/CeO2/ZrO2 catalyst, which resulted in 90% CO conversion at 200°C and selectivity greater than 80% at 125°C. Activity of the Co3O4/CeO2/ZrO2 catalyst increased with increase in Co3O4 molar ratio. 相似文献