当前位置：
X-MOL 学术
›
React. Chem. Eng.
›
论文详情
Our official English website, www.x-mol.net, welcomes your
feedback! (Note: you will need to create a separate account there.)
Hierarchical silica monoliths with submicron macropores as continuous-flow microreactors for reaction kinetic and mechanistic studies in heterogeneous catalysis†
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2018-04-17 00:00:00 , DOI: 10.1039/c8re00037a Richard Kohns 1, 2, 3, 4, 5 , Christian P. Haas 1, 2, 3, 4 , Alexandra Höltzel 1, 2, 3, 4 , Christian Splith 4, 5, 6, 7 , Dirk Enke 4, 5, 6, 7 , Ulrich Tallarek 1, 2, 3, 4
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2018-04-17 00:00:00 , DOI: 10.1039/c8re00037a Richard Kohns 1, 2, 3, 4, 5 , Christian P. Haas 1, 2, 3, 4 , Alexandra Höltzel 1, 2, 3, 4 , Christian Splith 4, 5, 6, 7 , Dirk Enke 4, 5, 6, 7 , Ulrich Tallarek 1, 2, 3, 4
Affiliation
|
Synthetic attempts towards submicron macropore and skeleton dimensions of hierarchical silica monoliths have so far been plagued by compromised structural homogeneity and/or mechanical stability. We overcome these problems by introducing urea as an agent to control macropore size and skeleton thickness (in addition to mesopore size) as well as a low-cost, straightforward method to achieve a seamless stainless-steel cladding of the monolithic silica rods tolerating pressures of >100 bar. Increasing the urea content of the starting sol comprising a sulfuric acid solution of tetraethoxysilane, poly(ethylene oxide), and urea from 3 to 24 wt% decreases the macropore size from 2.3 to 0.6 μm, the skeleton thickness from 2.0 to 0.4 μm, and increases the mesopore size from 10 to 26 nm. We assume that with increasing urea content of the starting sol, phase separation and gelation are retarded as well as shifted closer together, so that the formed monolithic structures represent a less evolved state of spinodal decomposition, preserving smaller macropores and a thinner skeleton. After cladding, the surface functionalization with aminopropyl groups yields a continuous-flow microreactor (5 mm i.d. × 4 cm length) used for heterogeneous catalysis of the Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate. The catalytic testing and kinetic studies with an on-line coupled reaction–analysis system reveal plug-flow conditions in the microreactor and the elimination of diffusive transport limitations demonstrating the overall success of the preparation. The proposed scheme enables academic laboratories to prepare hierarchical silica monoliths with desirable morphological properties (addressing particularly submicron macropore size and skeleton thickness) and versatile surface functionalization for demanding applications in adsorption, separation, organic synthesis, and catalysis.
中文翻译：
具有亚微米大孔的连续级二氧化硅整体流作为连续流微反应器，用于非均相催化的反应动力学和机理研究†
迄今为止，对结构化均质性和/或机械稳定性的折衷一直困扰着对亚微米级大孔和分级二氧化硅整料的骨架尺寸的合成尝试。我们通过引入尿素作为试剂来控制大孔尺寸和骨架厚度（除了中孔尺寸），以及一种低成本，简单的方法来实现整体式硅棒的无缝不锈钢包层以承受最大压力，从而克服了这些问题。 > 100巴。将包含四乙氧基硅烷，聚环氧乙烷和尿素的硫酸溶液的起始溶胶的尿素含量提高3至24重量％，可将大孔尺寸从2.3降低至0.6μm，骨架厚度从2.0降低至0.4μm，并且将中孔尺寸从10纳米增加到26纳米。我们假设随着起始溶胶中尿素含量的增加，相分离和胶凝作用被延迟以及移近在一起，因此形成的整体结构代表了旋节线分解的较少演化状态，保留了较小的大孔和较薄的骨架。包覆后，用氨基丙基进行表面官能化，得到连续流动的微反应器（内径5 mm×4 cm长），用于苯甲醛和氰基乙酸乙酯之间的Knoevenagel缩合反应的多相催化。通过在线耦合反应-分析系统进行的催化测试和动力学研究表明，微反应器中存在活塞流条件，并且消除了扩散传输限制，证明了该制备方法的总体成功。
更新日期：2018-04-17
中文翻译：
具有亚微米大孔的连续级二氧化硅整体流作为连续流微反应器，用于非均相催化的反应动力学和机理研究†
迄今为止，对结构化均质性和/或机械稳定性的折衷一直困扰着对亚微米级大孔和分级二氧化硅整料的骨架尺寸的合成尝试。我们通过引入尿素作为试剂来控制大孔尺寸和骨架厚度（除了中孔尺寸），以及一种低成本，简单的方法来实现整体式硅棒的无缝不锈钢包层以承受最大压力，从而克服了这些问题。 > 100巴。将包含四乙氧基硅烷，聚环氧乙烷和尿素的硫酸溶液的起始溶胶的尿素含量提高3至24重量％，可将大孔尺寸从2.3降低至0.6μm，骨架厚度从2.0降低至0.4μm，并且将中孔尺寸从10纳米增加到26纳米。我们假设随着起始溶胶中尿素含量的增加，相分离和胶凝作用被延迟以及移近在一起，因此形成的整体结构代表了旋节线分解的较少演化状态，保留了较小的大孔和较薄的骨架。包覆后，用氨基丙基进行表面官能化，得到连续流动的微反应器（内径5 mm×4 cm长），用于苯甲醛和氰基乙酸乙酯之间的Knoevenagel缩合反应的多相催化。通过在线耦合反应-分析系统进行的催化测试和动力学研究表明，微反应器中存在活塞流条件，并且消除了扩散传输限制，证明了该制备方法的总体成功。
京公网安备 11010802027423号