Preparation of Methyl Ester Sulfonates Based on Sulfonation in a Falling Film Microreactor from Hydrogenated Palm Oil Methyl Esters with Gaseous SO₃

Abstract

Fatty acid methyl ester sulfonate (MES) is an environmentally friendly anionic surfactant. It contains RCH(CO2Me)SO3Na (α-MES) as the active component and RCH(CO2Na)SO3Na (the disodium salt) whose content must be lower than 5%. In this paper, MES was prepared first in a falling film microreactor (FFMR) by sulfonation of hydrogenated palm oil methyl ester (ME) with SO3 diluted with N2, followed by aging in a tubular reactor and subsequent bleaching and neutralization with NaOH. The influences of the ME flow rate, the channel size, the N2 flow rate, the SO3-to-ME molar ratio, and the sulfonation temperature in the sulfonation step, as well as the influences of the SO3-to-ME molar ratio, the aging residence time, and the aging temperature in the aging step, were all examined. The results indicated that the ME flow rate had no evident influence on the ME conversion and the α-MES concentration both without overflow and with overflow. In the sulfonation step, the disodium salt (disalt) concentration increased with increase in the ME flow rate, the channel size, the SO3-to-ME molar ratio, and the sulfonation temperature or decrease in the N2 flow rate. In the aging step, the ME conversion, the α-MES concentration, and the disalt concentration increased with increase in the SO3-to-ME molar ratio, the aging residence time, and the aging temperature. The results of 1H NMR spectra indicated that RCH(CO2Me)SO3H was mainly formed in the sulfonation step in the microreactor, while it was formed in the aging step when the sulfonation was carried out in the conventional falling film reactor. Accordingly, a sulfonation reaction mechanism in the FFMR different from that in the conventional FFR was proposed. The final products with an α-MES concentration of 86.3% and a disalt concentration of 1.2% were obtained under the conditions of a ME flow rate of 2 mL/min, a channel size of 300 × 100 μm, a SO3-to-ME molar ratio of 1.2, a N2 flow rate of 900 mL/min, a sulfonation temperature of 85 °C, an aging temperature of 90 °C, and an aging residence time of 19.7 min.

Synthesis, Characterization and Exploratory Application of Anionic Surfactant Fatty Acid Methyl Ester Sulfonate from Waste Cooking Oil

“…MES prepared on the basis of this method can be obtained through a re-esterification process because of its low disodium salt content. Another possible route consists in the sulfonation of fatty acids with either SO 3 or chlorosulfonic acid and subsequent esterification, bleaching, and neutralization to integrate the MES product [8][9][10]. Regardless of the production procedure adopted, vegetable oil is the most commonly used starting material in MES production and about 80 % of the total production cost of methyl ester, the intermediate product of MES, is linked to the oil source [11].…”

“…Though the synthesis procedure of MES is simple, the shortage and relatively high cost of raw materials is becoming the major economic constraint in its production and commercialization. Several studies have been carried out with the aim of reducing MES production costs, but the majority of these works are focused on the improvement of the synthesis method and an increase in yield [8,10,11]. On the other hand, the idea of developing a new, low-cost, oil source to replace vegetable oil should become the primary consideration in the MES production industry.…”

A Falling‐Film Microreactor for Enzymatic Oxidation of Glucose

“…Theoretical simulations or mathematical calculations of flow distribution have been described previously in the literature. [15,34] …”

Methyl Ester Sulfonate: A High‐Performance Surfactant Capable of Reducing Builders Dosage in Detergents

“…The primary challenge for those green surfactants to penetrate into the Home Care market is to provide high performance while maintaining low cost. Among all the green surfactants, focus has been on α‐MES because of its high detergency performance, excellent calcium hardness tolerance, moderate foamability in both soft and hard water (Lim et al, ; Slamet and Wulandari, ; Xie et al, ; Xu et al, , b), and mildness to skin, making it as an attractive candidate in Home Care applications (Kapur et al, ; Stein and Baumann, ).…”