Process for the preparation of melamine

摘要

The invention relates to a process for the preparation of melamine which process comprises at least the following steps:
a. feeding ammonia and hydrogen cyanide, either separately or combined, to a first reactor that contains a catalyst that comprises at least one group 11 element and which reactor is maintained at a pressure of at least 2 bar and a temperature of 300-500 °C, at a space velocity lying between 10 2 and 10 6 ml/(g.hr), whereby a gaseous mixture (a) is formed comprising at least melamine,
b. optionally purifying mixture (a) producing a melamine containing mixture (b),
c. separating at least a part of the formed melamine thereby forming reaction mixture (c) and separated melamine The invention also relates to a process for the preparation of melamine, which process comprises at least the following steps:
i. feeding methane and ammonia to a pre- reactor which pre- reactor is maintained at a temperature between 700 and 1500 °C whereby a gaseous mixture (i) is formed comprising at least hydrogen cyanide,
ii. purifying mixture (i) thereby forming a mixture (ii) that contains at least hydrogen cyanide,
a. feeding hydrogen cyanide from mixture (ii) and ammonia, either separately or combined, to a first reactor that contains a catalyst and which reactor is maintained at a pressure of at least 2 bar and a temperature of 300-500 °C, at a space velocity lying between 10 2 and 10 6 ml/(g.hr), whereby a gaseous mixture (a) is formed comprising at least melamine,
b. optionally purifying mixture (a) producing a melamine containing mixture (b),
c. separating at least a part of the formed melamine thereby forming reaction mixture (c) and separated melamine The invention further relates to the melamine obtained by the processes.