硝基苯选择加氢制对氨基苯酚

研究了以０ ．８ ％ Ｐｄ／ Ｃ 为催化剂，硫化物为助催化 剂， 在酸性介质中硝基苯选择 催化氢化合成对氨基苯酚的反应条件。该反应 最佳条 件为：氢气 的压力 ０ ．２ Ｍ Ｐａ ， 催化剂 用量为 反应物 质量的 １ ．２ ％ ，助催化剂与催化剂用量摩尔比为０ ．６ ，硫酸溶液的质量分数为１２ ％ ，阳离子表面活性剂０ ．４ ｍ Ｌ，反应温度为（８５ ±１） ℃，反应时间为８０ ｍｉｎ 。研究 结果表明，选用易回收、低浓度 的０ ．８ ％ Ｐｄ／ Ｃ 催化剂，对硝基苯氢化反应具有较高的活性，通过 添加助催化剂可明显提高 反应的选择性。合成产品通过 Ｉ Ｒ、 Ｍ Ｓ 确认其结构，并通过滴定氨基值计算出硝基苯的转化率为９０ ％ 左右，产品的选择性达８０ ％ 。该工艺生产成本比传统工艺低，工业污染小，操作简便，收率高，为工业化生产提供理论依据

Selective Catalytic Hydrogenation of Nitrobenzene to p-Aminophenol

The reaction condition for the selective catalytic hydrogenation of nitrobenzene to p -aminophenol was studied in acid solution by using 0.8% Pd/C as main catalyst and sulphide as promoter. The optimum reaction conditions were that the hydrogen pressure is 0.2 MPa ;the mass ratio of the catalyst to the reaction product is 1.2%; the molar ratio of promoter to catalyst is 0.6; the concentration sulphuric acid solution is 12%, cation surfactant is 0.4 mL, the reaction temperature is (85±1)℃, and the reaction time is 80 min.The results showed that 0.8% Pd/C catalyst and easy recycled with low concentration has been selected, and it had high activity for nitrobenzene hydrogenation. Reaction selectivity had ben increasedobviously by adding promoter. The synthetic product was proved by IR and MS. The translation ratio of nitrobenzene was about 90% by titrating amino group value. The selectivity of p -aminophenol was 80%. The cost of this technology was lower than classical one, the industrial pollution was light. The operation was simple and the yield was high. The method provided theortical basis for commerical production.