(95e) Aldol Polymerization Inhibitor Evaluation Using Turbiscan

In a steam cracker, caustic tower is located between later stages of compression, which serves the purpose of removal of acid gases (H₂S and CO₂) through absorption using dilute caustic soda. Similar to other process equipment, the caustic tower is prone to fouling resulting in reduced caustic circulation rate, foaming, and pressure drop. A major contribution to fouling in caustic tower is due to base catalyzed aldol polymerization of aldehydes. The rate of polymerization depends on caustic tower operating temperature and strength of caustic. In order to prevent/minimize aldol polymerization various inhibitors are available in the market from different companies. Often, it is challenging for plant personal to choose the most suitable inhibitor among available options for his unit. Traditional laboratory flask test^1-3, followed by gravimetric separation of formed polymer is a method used to evaluate different inhibitors. Also, other innovative methods such as UV spectroscopy measurement or Evaporative Light Scattering Detector (ELSD)⁴ for quantification of aldol polymer as a function of time is reported.

In the current paper, we will describe an easy and efficient method of evaluating caustic inhibitors at reducing aldol polymerisation as a function of time, temperature and caustic strength using a Turbiscan™ LAB stability analyzer. The extent of polymerisation observed as an increase in destabilization behaviour of the reactant mixture, measurements derived from back scattering and transmission signals from the test solution. This method for evaluating aldol inhibitors is considered an improvement on methods described earlier.

References:

(1) McClain Robert D, Patel Natu R, Glath Raymond M, Reducing undesired polymerization in hydrocarbon cracking processes, WO 02/36715A1.

(2) Mahesh Subramaniyam, Banker Prashant, Method for prevention of fouling in basic solution by inhibiting polymerization and solubilizing deposits using amino acids, US6986839B2

(3) Hiren M. Bhajiwala, Harshad R. Patil, Virendrakumar Gupta, Studies of amino acids for inhibition of aldol condensation and dissolution of polymeric product of aldehyde in alkaline media, Appl Petrochem Res (2013) 3:17–23.

(4) Satheesh Sambandam, Bassam Alnasleh, Debby Rossana, Study of aldol polymerization in ethylene plant Caustic towers, Presentation at the 2018 Spring National Meeting Orlando, Florida, April, 23, 2018.