Optimization of Chloroethane-Promoted Titanium-Catalyzed Ethylene Dimerization Using the Taguchi L₁₆ Design

Abstract

A five-factor four-level Taguchi L₁₆ orthogonal design was used to determine optimized factors of the [titanium tetrabutoxide (Ti(OC₄H₉)₄)–triethyl aluminum (TEA)] catalyst system with two additives: tetrahydropyran (THP) as an electron donor ligand and chloroethane (CE) as a halide promoter. Tests determined the effects of temperature, pressure, TEA/Ti, THP/Ti, and CE/Ti molar ratios on overall yield of reaction (Y_R(%)) and weight of polymer (W_PE(mg)) and evaluations were investigated by signal to noise (S/N) ratios and their mean. Moreover, analysis of variance (ANOVA) determined that the THP/Ti molar ratio (with 33.42%) and the temperature (38.99%) had the highest contributions in Y_R and W_PE, respectively, for the aforesaid newly introduced four-member system. The confirmation tests showed very good consistency between predicted and actual results. The results show that this previously untested method can efficiently increase Y_R and decrease W_PE and better demonstrates the role of the catalyst. The results can be applied to improve 1-butene production on an industrial scale and minimize polymer fouling that could result in a reactor shutdown.

Keywords:

• Analysis of variance
• Ethylene dimerization
• Overall yield of reaction
• Promoter
• Taguchi method
• Weight of polymer

Acknowledgments

Foremost, the authors express their heartfelt thanks to Mr. Abbas Nassiri, Senior Polymer Researcher of the R&D division of Arak Petrochemical Company (ARPC), for his skillful contributions to the dimerization experiments. The helpful advice from Mr. Abbas Saadatmand, Head of Research Laboratory of the R&D division of ARPC, on GC adjustment and the definition of GC methods for the analysis of gas and liquid samples is greatly appreciated. S.H.M. is grateful to Mr. Fakhredin Mohajerani, head of 1-butene/LLDPE laboratory of ARPC, for his effective advice on the sampling method of gaseous and liquid products from the 1-L Büchi reactor and to Mr. Saeid Allamehnezhad, Senior Researcher of the R&D division of ARPC, for his useful explanations during the course of this research.

S.H.M. dedicates this article to the memory of his late father, Mr. Seyed Hasan Mahdaviani, a famous retired professor of Persian literature.