Studies On Preparation Of Hydroxylamine By HPO Process

Caprolactam is one of the important petrochemicals and is mainly used for manufacture of enigineering plastic and fibre for public and industry. At present, there are three representative techniques for manufacture of caprolactam: the process of cyclohexanone- hydroxylamine, of PNC and of SNIA. In the method of cyclohexanone-hydroxylamine, benzene is a main raw material, the process include hydrogenation of benzene, oxygenation of cyclohexane, oximation of cyclohexanone, rearrangement of cyclohexanone oxime and refinement of crude caprolactam. The PNC process also uses benzene as raw material, by this process, cyclohexanone oxime can directly be prepared by the light-catalyzed nitrosation of cyclohexane. In the method of SNIA, toluene is used as raw material,the process mainly consists of oxygenation of toluene, hydrogenation of benzoic acid, nitrosation of cyclohexane-carboxylic acid with nitrosyl sulfuric acid. The processes of cyclohexanone-hydroxylamine are widely adopted over the world, in which, hydroxylamine is a very important intermediate. The mainly methods of preparation of hydroxylamine salt at industrilized- scale are HSO process, NO process and HPO process. SINOPEC Baling branch manufacture caprolactam by HPO process. After the capacity of plant is up to designed-scale and is successfully enlarged to 70kt/a, the company is further going to broaden the production capacity to 100kt/a based on old plant and equipments. So, we study the process of hyam preparation once more by analyzing the real situation of the plant, and hope to fulfill the aim by increasing the hyam concentration in IPL. The topic includes: Firstly, we should carry out the essential kinetic experiments to synthesize high concentration of hyam, and to grasp the basic character of reaction, so that we can establish the kinetic model.Secondly, we further put up continuous experiment at lab-scale, middle-scale experiment by-pass the plant and plant test respectively. The result of mini experiment indicates that the velocity of producing hyam can be increased by elevating the H2 partial pressure, the concentration of catalyst, H+ and nitrate. In existence hyam concentration, the velocity of reaction of nitrate hydrogenation to hyam is in proportion to 0.65 exponential of catalyst concentration and 0.45 exponential of H2 partial pressure, the influene of concentration of nitrate and H+ on the velocity of reaction is fade. Due to the plant limitation, the catalyst concentration and hydrogen pressure can not be increased doubly, at meantime, it is difficult to elongate the stay time of reactants in reactor. Furthermore, the by-reactions of hyam in series are step up with the increasing of hyam concentration, so the total selectivity of hyam is droped down. It has little possibility to enlarge the capacity by increasing the hyam concentration at the old plant.