From Start-of-Run till End-of-Run Maleic Anhydride (MA) catalyst activity is continuously decreasing. To lengthen the life-cycle of catalyst Trimethyl-Phosphate (TMP) must be added to the feed. An important role of TMP is the catalyst activation process to achieve full catalyst selectivity.

General description of the system:

A Selectivity/Activity Stabiliser (SAS) dosing system is placed into the reactor section and it is supplied as a package that contains a stainless-steel tank for TMP storage, dosing pump, control system, safety relief valve, and TMP drum pump with hose for safe and fast unloading of TMP from the drum into the tank. The dosing system is installed into a heated cabinet. A special atomiser/distributor is located at the TMP / feed gas line connection point.

TMP is supplied by the TMP dosing pump from the TMP tank and is then injected into the feed-gas line through a special atomiser/distributor. On the TMP line a shut-off valve is installed to prevent feed-gas flowing back to TMP system. The dosing pump is equipped with capacity regulation and discharge pressure protection.

Main Advantages of TMP dosing system:

• constant flow and perfect distribution of TMP in reactor;
• better control of the catalyst operation – stable catalyst hot-spot;
• higher yields and plant productivity;
• longer catalyst lifecycle;
• system is also capable of dosing Triethyl-Phosphate (TEP).