水溶性钯配合物催化柠檬醛的选择加氢反应研究 Ⅰ.反应条件的影响

研究了在水／有机物两相体系中水溶性钯－膦配合物催化柠檬醛的加氢反应．考察了反应温度、氢气压力、底物和催化剂浓度、反应时间、水相ｐＨ值等对该反应的影响，并与几种柠檬醛衍生物的加氢结果进行了比较．发现仅用蒸馏水作水相，则主要产物是二氢香茅醛（＞９３％）；而水相中加入Ｎａ２ＣＯ３后，则主要产物为香茅醛（９７％），且加氢速度比同样条件下使用Ｐｄ／Ｃ催化剂快得多．

Selective Hydrogenation of Citral Catalyzed by Water Soluble Palladium Complex

Hydrogenation of citral catalyzed by water soluble PdCl 2(TPPTS) 2TPPTS = P( m C_6H_4SO_3Na)_3] was studied in a two phase system.The effects of the reaction temperature, H 2 pressure, concentration of substrate and catalyst, reaction time and pH value of the aqueous phase on the catalyst activities and selectivities have been explored. Hydrogenation of several citral derivatives under the same conditions was compared. The results showed that the selectivity of the reaction depended strongly on the pH valuse of the aqueous phase. The selectivity to citronellal increased with increating pH value of aqeous solution. When citral hydrogenation was carried out at the same pH values the selectivities were higher in Na 2CO 3 solution than in NaOH solution. The yield of 97% of citronellal has been obtained at pH=11 6 by using Na 2CO 3 solution. The C=C bond in citronellal could be further hydrogenated to form dihydrocitronellal when the hydrogenation was carried out in distilled water(pH=6 0).Therefore, high selective formation of citronellal or dihydrocitronellal from citral hydrogenation could be realized by modification of the reaction conditions. The yield of dihydrocitronellal could reach 93% by prolonging the reaction time to 6 h. In addition,this complex has shown much higher catalytic activity for the hydrogenation of the conjugated C=C double bond in citral to form citronellal than using Pd/C or PdCl_2(PPh_3)_2 as the catalyst under similar reaction conditions.