Response of Titanium-Isopropoxide-Based Heterogeneous Amphiphilic Polymer Catalysts for Transesterification

Abstract

Transesterification is a widely used reaction in the chemical industry. Currently, industrial-scale transesterification is primarily performed via homogeneous catalysts. Because of downstream separation issues, there is a need for effective heterogeneous catalysts. However, heterogeneous catalysts introduce the drawback of mass-transfer limitations into the reaction system. The substrates associated with transesterification form a three-phase system that is inherently immiscible in each other with liquid/liquid/solid (L/L/S) interfaces. This study was conducted to ascertain the behavior of a solid catalyst that has amphiphilic properties in the transesterification system. It was hypothesized that the amphiphilic catalyst, depending upon its degree of polymerization, would orient itself at the interface of the two immiscible liquids, forming an emulsion. The catalytic active site, in the mean time, would catalyze the transesterification reaction. In this study, the catalytic aspects of the titanium-isopropoxide-based inorganic dendritic polymers were investigated. Titanium isopropoxide catalysts with varying degrees of polymerization were developed by sol−gel water condensation. The degree of polymerization was controlled by the amount of water addition. Five forms of catalysts with varying degrees of polymerization were subjected to transesterification at varying temperatures and time intervals. In this experiment, soybean oil was used as the triglyceride. Isopropanol and titanium isopropoxide were used as the catalyst precursors. The highest yield of 41.56% of propyl esters was obtained at 200 °C after 3 h with 1% (w/w) of the monomeric form of the catalyst. The behavior of the dimeric and higher forms was highly correlated with reaction temperatures and residence times.

Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions

“…In 2010, Nawaratna et al reported the first and sole example to date of rationally designed amphiphilic nanoparticles for base-catalyzed reactions. [63] Inspired by a former study on amphiphilic titanium alkoxide oligomers (see Ref. [34] and section 3.1), the authors prepared titaniumisopropoxide-based inorganic dendritic polymers with variable degrees of polymerization ( Figure 13).…”

Phase Stability of a Triglyceride/Alcohol/Catalytic‐Surfactant System in Transesterification

“…This is likely due to the higher amount of triglyceride substrate in the 7:3:2.5 mixture, as in both samples the catalyst concentration is the same. Previous studies with the system (with the only change being the amount of the catalytic surfactant used) resulted in lesser ester yields,13, 14 even after 3 h of reaction time at 200 °C. This observation exemplifies the importance and impact of emulsification ability that a catalyst can bring into systems with immiscible or poorly miscible reactants.…”

“…The first stage was adopted to analyze the effect of alkoxide tail group on phase stability of the ternary system while the second stage looked at the alkoxide polymerization effect on the stability of the system. We have discussed the catalytic effects of tail group and polymerization in earlier studies13, 14 and present studies were conducted to ascertain the correlation of phase stability of the ternary system with catalytic effects. In the first stage, titanium ethoxide, titanium propoxide, and titanium butoxide were compared for their effects on the phase stability of the system while in the second stage the effect of titanium isopropoxide was elucidated in more detail.…”

“…In our previous studies we looked into the catalytic activity of three‐phase systems consisting of a triglyceride (soybean oil), metal alkoxide(s), and the respective alcohol(s) 13. 14 The impact of metal groups and alkoxide groups of transition metal alkoxides on the catalytic ability of the transesterification reaction was elucidated. Herein, we describe the concomitant impact of the alkoxide on the phase stability, that is, the stability of an emulsion, and the catalysis of the reaction.…”

Grenzflächenkatalyse in Pickering‐Zweiphasensystemen: vom Emulsionsdesign zu grünen Reaktionen

“…Aus dem Jahr 2010 stammt das erste und bislang einzige Beispiel eines maßgeschneiderten amphiphilen Nanopartikels für basenkatalysierte Reaktionen von Nawaratna et al 63. Inspiriert durch eine frühere Studie zu amphiphilen Titanalkoxidoligomeren (siehe Lit.…”