Condensation Product Of The Hydrogenation Process Research

Vitamin A has been synthesized by O.Isler technology since 1965 in China. There is no further breakthrough in the Oxenin hydrogenation research as far. Compared to the selectivity of 95% in foreign plants, the selectivity of the domestic plants ranges from 85% to 88%. The Oxenin hydrogenation technology including catalyst preparation, and reaction dynamics, and the influence of reaction conditions and organic modifier has been presented.By analysis of the catalyst preparation and utilization, we found that the metal modifier and noble metal decreased because of the carrier-material being crashed resulting in deactivation of the catalyst and reduction of selectivity. We obtained that the activity and selectivity of catalyst is all high when 1 ml hydrogen is absorbed by per gram catalyst by correlating the catalyst performance using the catalyst characteristic system.The experimental results showed that the selectivity of Oxenin hydrogenation can reach 92% if catalyst is prepared by pretreating carriers of 120 to 180 meshes, adding the quantity of metal modifiers, and adding appropriate base in the palladium chloride solution.We found that the double-bond selectivity can reach to 95% by adding modifier B comprising sulfur compound and auxiliary modifier E in Oxenin hydrogenation reaction, employing methlane dichloride and petroleum ether as solvent, and reacting in lower temperature.We studied the process of the Oxenin hydrogenation reaction systematically for the first time. It is found that the Oxenin hydrogenation reaction is zero-order reaction when the reaction temperature ranges from 30℃ to 40℃ and the rate of conversion is below 90%. The dynamic equation of major and side reaction isrmajor= d[S=]/dt = 4.09 × 103(PH2)exp(-E/RT) rside= d[S0]/dt - 5.07 × 105 (PH2)0.8exp(-EVRT) where activation energy is E=7.31 × 103 Lmol-1, E' =2.62 × 104 J.mor-1.The experiments showed that hydrogen is not absorbed by the catalyst. The hypothesis that the major and side reaction is parallel reaction has been proved right. The Oxenin hydrogenation reaction in low temperature and high hydrogen pressure favors the improvement of the reaction selectivity.Therefore, it is possible that we can overtake the international advanced level in the field of vitamin A synthesis.