Hydrolysis of palm oil catalyzed by macroporous cation‐exchanged resin

Abstract

Hydrolysis of palm oil was studied using four types of commercial H + -exchanged resin with acidity in the region of 5 ×10 −3 eq g −1 but with different pore volumes, specific surface areas, and pore diameters. The reaction was carried out in a stirred batch reactor in the liquid phase with continuous steam injection for up to 14 h. The rate of hydrolysis did not depend on total pore volume and specific surface area but did depend on pore diameter. On exchanging H + with La 3+ , Co 2+ , and Na + , the rate of reaction decreased markedly and was dependent on the degree of exchange, demonstrating that hydrolysis was catalyzed by H + sites. The activation energy for the hydrolysis of the triglycerides was estimated to be 240 kJ mol −1 . A procedure to estimate the rates of the different stages of hydrolysis and hence the individual rate constants of the forward and reverse reactions is described. The procedure yielded reasonable parameters for the reaction at 155°C up to 6 h of reaction time, when about 75 mol% of triglycerides was hydrolyzed.Paper no. J8946 in JAOCS 76, 529-533 (April 1999).Continuous high-pressure fat splitting with superheated steam is still the preferred technology for fatty acid production since its invention in the 1930s. Hydrolysis is usually carried out at 250°C and 3000-5000 kN/m 2 pressure with countercurrent flow of water and oil. About 96-98% of hydrolysis takes place within 2 h (1). The process involves high capital cost because of the corrosive nature of the acid produced at such high temperatures and pressures; high steam pressure also requires high energy input and costs. Due to rising energy and capital costs, renewed interest in ambient temperature enzymatic fat splitting using lipase as catalyst emerged around 1980 (1,2). The lipase process is suitable for small-scale production of fatty acids from heat-sensitive oils. The problems of catalyst recovery and the low rate of attaining equilibrium prevent commercialization of the process for large-scale production, although efforts to immobilize the enzyme on solid supports and to carry out the reaction at temperatures above ambient have resulted in some success (3).Catalyzed hydrolysis of fats and oils in batchwise fatty acid production was used even before steam splitting. The Twitchell process, which uses a sulfonic acid as catalyst, was first patented in 1898 (4). Other catalysts involving solid acids and bases, such as supported alkylbenzene sulfonic acid, ZnO, and lime, have also been used (5). Cation-exchanged resins have been used for hydrolysis of esters (6-8), and the hydrolysis kinetics of triglycerides catalyzed by cation-exchanged resins has also been reported (6). It is well established that the hydrolysis of triglycerides is a stepwise process catalyzed by acid/base; however, there are insufficient kinetic data on the process in current literature. This report aims to fill the gap. EXPERIMENTAL PROCEDURESFour samples of polystyrene sulfonic acid cation-exchanged resins, CT-110, CT-151, CT-165, and CT-175, were gifts fro...

Reaction Kinetics and Mechanisms for Hydrolysis and Transesterification of Triglycerides on Tungstated Zirconia

“…Many studies have reported the kinetic parameters for the non-catalytic hydrolysis of refinery rapeseed oil in subcritical water [35], of canola oil in supercritical carbon dioxide media [24,36] and of various oils (coconut, peanut, and beef tallow) in a batch reactor [33]. However, the solid acid catalyzed hydrolysis of TGs has only been investigated by Yow and Liew using palm oil [26]. The complexity of water-oil mixtures makes it difficult to obtain good initial kinetic data due to 2-liquid phase behavior [37].…”

“…The complexity of water-oil mixtures makes it difficult to obtain good initial kinetic data due to 2-liquid phase behavior [37]. It was found that for the 2-phase situation, the rate of dissolving of water in oils is the RDS of hydrolysis with the solubility of water in oil increasing with FFA formation [24,26,36]. Use of a model triglyceride (TCp) and low concentrations of water in this kinetic study permitted us to determine the solid-acid catalyzed hydrolysis mechanism without 2-phase problems.…”

“…5a, b were a = 1.34 and b = -1.15 for water-to-TCp molar ratios of 0.8-1.2. The reaction orders for non-catalytic reaction in the temperature range of 100-250°C [24,33,36] and for catalyzed hydrolysis on a macroporous cation-exchange resin at 155°C [26] have been reported to be 1 for both TG and water. Under non-catalytic conditions, acid sites are not required to carry out this reaction, thus when the amount of water as a reactant increases, the reaction rate should increase [23].…”

“…Only one paper by Yow and Liew [26] has reported an investigation of the kinetics of hydrolysis of palm oil catalyzed by a macroporous cation-exchanged resin. They suggested that this reaction follows a mechanism similar to that of homogeneous acid catalyzed hydrolysis reaction which has first-order kinetics at 155°C.…”

A heterogeneous acid‐catalyzed process for biodiesel production from enzyme hydrolyzed fatty acids

“…18 An amount of 1 g of resin was mixed with 200 ml of 0.1 M NaOH prepared in 5% NaCl, and allowed to stand overnight at room temperature. Fifty milliliter of the supernatant liquid was subsequently titrated with 0.1 M HCl using phenolphthalein as an indicator to determine residual amount of base (i.e., acidity of the resin).…”