Calcium oxide and strontium oxide as environmentally benign and highly efficient heterogeneous catalysts for the Tishchenko reaction of furfural
Calcium oxide and strontium oxide as environmentally benign and highly efficient heterogeneous catalysts for the Tishchenko reaction of furfural
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DOI：
10.1039/b102389f
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发表时间：
2001
影响因子：
4.9
通讯作者：
T. Seki;Kazumasa Akutsu;H. Hattori
中科院分区：
文献类型：
--
作者：
T. Seki;Kazumasa Akutsu;H. Hattori
铁先科反应是醛的二聚化反应，在铝烷氧化物的作用下生成相应的酯。1-5大约一个世纪以来，人们开发了许多用于各种醛的铁先科反应的催化剂，以获得高产率的产物酯。虽然许多醛转化为铁先科二聚体的产量很高，但对糠醛的铁先科反应成功进行的研究很少。据报道，当使用传统的铝烷氧化物、硼酸或四羰基高铁酸盐（2II）作为催化剂时，该反应很难进行。2,6,7最近，一些均相催化剂如（C5Me5） 2LaCH (SiMe3) 2和La [N (SiMe3) 2] 3被报道对糠醛的Tishchenko反应有效，尽管这些催化剂需要较长的反应时间才能使产物酯达到合成满意的产率。8,9此外，从所得溶液中去除这些均相催化剂会导致催化剂的损失和产品收率的降低。此外，考虑到环境问题，鼓励避免在工业过程中使用有毒的过渡金属催化剂。在这里，我们报告了环境友好，高效的多相催化剂的铁先科反应的糠醛。一般反应方程如方案1所示。以Mg (OH) 2、Ca (OH) 2、SrCO3和BaCO3为原料，在真空中高温热分解法制备了MgO、CaO、SrO和BaO碱土氧化物。以La (OH) 3为原料，采用与碱土氧化物相同的工艺制备氧化镧，La (OH) 3由La (NO3) 3水溶液经氨水水解得到，然后用蒸馏水洗涤，在373 K下干燥。以Zr (OH) 4和Zn (OH) 2为原料，在真空中高温热分解制备ZrO2和ZnO。g-氧化铝作为催化剂和KOH/氧化铝负载催化剂由日本催化学会（JRC-ALO4）提供。合成了水滑石（Mg/Al= 2）。10氧化铝负载KF （KF/氧化铝）购自Fluka， XRF测定其KF含量为8.2 mmol g21。用KOH水溶液浸渍g-氧化铝（JRC-ALO4），在373 K空气中干燥，制备KOH/氧化铝负载型KOH催化剂；KOH含量为1.2 mmol g21。所测催化剂的预处理温度和表面积见表1。糠醛是从奥尔德里奇购买的，通过减压蒸馏提纯。
The Tishchenko reaction is dimerization of aldehydes to yield the corresponding esters by the action of aluminium alkoxides. 1–5 For about a century, a number of catalysts for the Tishchenko reaction of various types of aldehydes have been developed to obtain the product esters in high yields. While many aldehydes have been converted to the Tishchenko dimers in good yields, few studies have been successfully carried out on the Tishchenko reaction of furfural. This reaction has been reported to be difficult when carried out using traditional aluminium alkoxides, boric acid or tetracarbonylferrate (2II) as catalysts. 2, 6, 7 Recently, some homogeneous catalysts such as (C5Me5) 2LaCH (SiMe3) 2 and La [N (SiMe3) 2] 3 have been reported to be effective for the Tishchenko reaction of furfural, though these catalysts require a long reaction time to give the product ester in a synthetically satisfactory level of yield. 8, 9 In addition, removal of those homogeneous catalysts from the resulting solution causes loss of catalyst and reduction of the product yields. Moreover, in view of environmental concerns, avoidance of use of toxic transition metal catalysts in industrial processes is encouraged. Herein, we report environmentally benign, highly effective heterogeneous catalysts for the Tishchenko reaction of furfural. The general reaction equation is shown in Scheme 1.Alkaline earth oxides, MgO, CaO, SrO and BaO, were prepared from Mg (OH) 2, Ca (OH) 2, SrCO3 and BaCO3, respectively, by thermal decomposition at elevated temperatures in vacuo. Lanthanum oxide was prepared from La (OH) 3 by the same procedure as the alkaline earth oxides, the La (OH) 3 being obtained from an aqueous solution of La (NO3) 3 upon hydrolysis with aqueous ammonia, followed by washing with distilled water and drying at 373 K. ZrO2 and ZnO were prepared from Zr (OH) 4 and Zn (OH) 2, respectively, by thermal decomposition at elevated temperatures in vacuo. g-Alumina used as a catalyst and as a KOH/alumina-supported catalyst was supplied from the Catalysis Society of Japan (JRC-ALO4). Hydrotalcite (Mg/Al= 2) was synthesized as reported. 10 Alumina-supported KF (KF/alumina) was purchased from Fluka, and its KF content was determined as 8.2 mmol g21 by XRF. Alumina-supported KOH catalyst (KOH/alumina) was prepared by impregnation of g-alumina (JRC-ALO4) with an aqueous solution of KOH, followed by drying at 373 K in air; the KOH content was 1.2 mmol g21. The pretreatment temperatures and surface areas of the catalysts examined are listed in Table 1. Furfural was purchased from Aldrich, and was purified by distillation under a reduced pressure.