Combine calculation and experiment to study the undesired polymerization of styrene for screening of effective inhibitors

• A calculation and experimental methods were employed to screen the best antipolymer and antioxidant. • DFT approach was adopted to analyze the correlation between the ability of inhibitors to donate or accept electrons. • EPHA and BPHA from amine family and 4‑hydroxy-TEMPO and 4-oxo-TEMPO from stable nitroxide radicals were showed to be the most effective inhibitors with 17.20, 29.55, 24.85 and 56.30 % growth, respectively. • It was observed that the growth percentage of the mentioned blend inhibitor was 7.2 % after 4 hrs of operation. Regarding undeniable formation of the undesired polymer (UP) in the styrene purification process, it is of vital importance to inhibit its production. To address the mentioned issue, effects of injecting antipolymers (e.g., stable nitroxide radicals (i.e., SNRs) and antioxidants (e.g., alkylhydroxylamines (AHA)) on the controlling the UP formation have been studied through density functional theory (DFT) calculations as well as experimental method in this study. In fact, electrophilicity and growth percentage were evaluated by DFT calculations and experimental approach, correspondingly. Accordingly, it was revealed that the best antipolymers in terms of inhibiting performance were 4‑hydroxy-2,2,6,6-tetramethyl piperidine 1-Oxyl (4‑hydroxy-TEMPO) and 4-oxo-2,2,6,6-tetramethylpiperidine 1-Oxyl (4-oxo-TEMPO), and from the antioxidants, N-Ethyl-N-phenyl hydroxylamine (EPHA) and N-Benzyl-N-phenyl hydroxylamine (BPHA) exhibited the best performance. In addition, the growth percentage of 18.70, 20.55, 24.85 and 46.8, were obtained for the EPHA, BPHA, 4‑hydroxy-TEMPO, and 4-oxo-TEMPO after 4 hrs of operation, correspondingly. Besides, the synergetic effects of the used inhibitors were determined experimentally. Among the evaluated inhibitors, EPHA/4‑hydroxy-TEMPO demonstrated the best synergetic effects over the control of UP formation. Finally, the blend of 4‑hydroxy-TEMPO (40 wt.%) and EPHA (60 wt.%) was obtained to be the optimum (best) inhibitor with 7.2 % polymer growth after 4 hrs of operation.