Traditional methylal synthesis with sulfuric acid catalyst has a series corrosion problem to the equipment. Along with methylal technology development, the sulfuric acid catalyst is replaced by solid resin, then, reaction and distillation combination process is developed. In this way, the production capacity and quality has been greatly improved, but, the catalyst regeneration is quite difficult and the COD in the waste water exceeds 2000ppm.
We have developed new process and new technology with own intellectual property. It has the features of easy catalyst regeneration and replacement. Furthermore, the conversion rate and output is increased; waste water COD is reduced to be lower than 200ppm.
(1)Common concentration methylal
Methanol and formaldehyde are pumped into the fixed bed catalysis reactor in proportion. The reaction temperature is controlled in the range of 60¡æ¡«85¡æ in the reactor to form mixing solution of methylal containing methanol and water. This mixing solution is heated for evaporation by the re-boiler steam at the bottom of distillation tower. The easy volatile compositions are collected at the top of the tower through screen packing, while the heavy fraction remains at the tower bottom. The azeotropy fraction of methylal and methanol from the tower top are sent to the reflux tank through condenser. Part of liquid returns to the top of the tower for refluxing, and another part of it is collected as final product. The COD in the waste water at the bottom can be controlled below 200ppm.
(2)High Concentration Methylal
First, use common concentration methylal process to receive low concentration methylal. Pump 92% methylal solution into pressure differential distillation tower, The pressure at the tower is controlled at the range of 1.2-1.5Mpa, temperature at the top of the distillation tower is controlled at 120¡æ, while temperature at the bottom of the distillation tower is controlled at 135¡æ. In this way, High concentration methylal can be collected at the bottom, the fractions on top of the tower is refluxed to reactor and pressurized distillation tower.
(1)This process has relatively lower energy consumption by comparison with the same industry.
(2)The catalyst activity lasts longer time, and can be regenerated.
(3)Small amount of waste water with low formaldehyde concentration is far below the energy saving and the environmental protection requirement. The sewage is greatly reduced.
(4)Has the advantage of high conversion rate, good selectivity, low energy consumption, high purity, easy operation and less investment etc.