水溶性钯配合物催化柠檬醛的选择加氢研究 Ⅱ.催化剂的循环使用

Selective Hydrogenation of Citral Catalyzedby WaterSoluble Palladium ComplexⅡ Study of the Catalyst System Stability

研究了以水溶性ＰｄＣｌ２（ＴＰＰＴＳ）２为催化剂，在水／有机物两相体系中，添加ＴＰＰＴＳ、ＣＴＡＢ、ＰＶＡ、明胶和碳酸钠对柠檬醛加氢反应及催化剂稳定性的影响．添加配体ＴＰＰＴＳ、明胶或表面活性剂ＣＴＡＢ有利于减少钯黑的形成，但会引起催化活性的降低；而添加ＰＶＡ和Ｎａ２ＣＯ３，虽然都不能抑制钯黑的形成，但后者的添加会明显提高加氢速度；发现，明胶加碳酸钠的体系不仅可以稳定催化剂的活性物种，避免钯黑的析出，而且催化反应的转化率及选择性都较高．

おhe stability of the watersoluble PdCl2(TPPTS)2[TPPTS=P(mC6H4SO3Na)3 ] catalyst system was studied in hydrogenation of citral. Several additives were introduced into the biphasic catalytic system for stabilization of the palladium complex active species in water. The addition of surfactant CTAB, gelatin or ligand TPPTS was favorable to the reducing of Pd black formation, but the catalytic activity was decreased with increasing their concentrations. The addition of PVA or Na2CO3 does not inhibited the formation of Pd black, however, the addition of Na2CO3 resulted in the obvious increase of hydrogenation rate and selectivity. We found that the mixed additives consisting of TPPTS、 Na2CO3 and CTAB were satisfactory for maintaining the higher conversion and selectivity, but the stability of the catalyst system was not very good and more Pd black was formed after five cycles. The higher conversion and selectivity could be kept by proper combination of Na2CO3 and gelatin, and the formation of Pd black could be avoided also.