Amine functionalized silicas have frequently been investigated as potential aldol reaction catalysts. However, active site leaching due to hydrolysis cannot be avoided, limiting the long-term stability of these catalysts in aqueous aldol reactions. Therefore, novel catalysts based on an organic resin have been developed starting from a suspension polymerized poly(ethylene glycol) methacrylate (PEGMA) hydrogel with poly(ethylene glycol) dimethacrylate (PEGDMA) as cross-linker. Amine functionalization was performed by chlorination of the terminal hydroxyl groups in the resulting PEGMA resin and subsequent nucleophilic substitution with an amine precursor, i.e., ethylenediamine (EDA), N,N′-dimethylethylenediamine (DED), or methylamine (MA). The successful synthesis of the catalysts was confirmed by ¹³C NMR, FT-IR, and elemental CHN analysis. Performance evaluation in a batch reactor for the aqueous aldol reaction of acetone with 4-nitrobenzaldehyde resulted in a turnover frequency (TOF) of the PEGMA-EDA catalyst amounting to 6.3 ± 0.4 · 10⁻⁴ s⁻¹, which is of the same order of magnitude as that of the corresponding state-of-the-art amine functionalized silica evaluated using hexane as solvent. The PEGMA-DED catalyst exhibited a somewhat lower TOF of 3.1 ± 0.2 · 10⁻⁴ s⁻¹, while the PEGMA-MA catalyst did not exhibit any turnover, indicating that the secondary amine in the backbone of the active site in the PEGMA-EDA catalyst is inactive. Continuous-flow evaluation of the PEGMA-EDA catalyst in a packed-bed reactor indicated that, as opposed to a primary amine functionalized silica catalyst, a stable catalytic activity as a function of time on stream could be achieved for at least 8 h and, hence, that no deactivation has occurred in this timeframe.

胺官能化的二氧化硅经常被研究为潜在的醛醇缩合反应催化剂。然而，由于水解而导致的活性位点的浸出是不可避免的，这限制了这些催化剂在水性羟醛反应中的长期稳定性。因此，已经从以聚（乙二醇）二甲基丙烯酸酯（PEGDMA）为交联剂的悬浮聚合的聚（甲基丙烯酸乙二醇酯）水凝胶开始开发了基于有机树脂的新型催化剂。通过氯化所得PEGMA树脂中的末端羟基并随后用胺前体即乙二胺（EDA），N，N'-二甲基乙二胺（DED）或甲胺（MA）进行亲核取代来进行胺官能化。催化剂的成功合成证实了¹³ C NMR，FT-IR和元素CHN分析。在用于与4-硝基苯甲醛丙酮的含水醛醇缩合反应间歇式反应器性能评价导致PEGMA-EDA催化剂金额总计的转换频率（TOF）至6.3±0.4·10 ^-4小号^-1，这是相同的顺序的其强度与使用己烷作为溶剂评估的相应的最新胺官能化二氧化硅的数量级相同。PEGMA-DED催化剂的TOF稍低，为3.1±0.2·10 ^-4 s ^-1，但PEGMA-MA催化剂没有任何更新，表明PEGMA-EDA催化剂中活性位点主链中的仲胺是无活性的。在填充床反应器中对PEGMA-EDA催化剂进行的连续流动评估表明，与伯胺官能化的二氧化硅催化剂相反，至少在8小时内可获得稳定的催化活性，这是生产时间的函数，并且因此，在此时间范围内未发生停用。