Covalorization of Palm Oil‐Refining by‐Products as Soaps

Abstract

This study deals with the covalorization of spent bleaching clay (SBC) and palm fatty acid distillate (PFAD), the by-products of palm oil-refining plants (3 Mt. year −1 ), through soap manufacture. Obtained SBC and PFAD samples show differing acidity and saponification values depending on their content of free fatty acids and of acylglycerols. The SBC sample had an acidity of 60.5% and a saponification value of 182 mg KOH g −1 of oil, and the PFAD sample has an acidity of 88.4% and a saponification value of 204 mg KOH g −1 of oil. Soaps are prepared using the stoichiometric amount of NaOH, under varying proportion of water introduced through the basic solution. The overall reaction (neutralization and saponification) is complete (99.9%) with PFAD, whereas the yield reaches only 56.1% with SBC. When mixing SBC and PFAD, for example under a 1:1 weight ratio, the overall reaction completion (87.7%) is surprisingly higher than expected based on the computed individual reaction yields (78%), showing a synergistic effect of about 10% on the course of the saponification reaction of acylglycerols in SBC. The water content was found to be a critical parameter, 30% w/w of added water providing the highest yield. These results show an innovative way for covalorizing two important by-products of palm oil industrial processing as a single final product. By-products of the physical refining of other oils could also be valorized following the same method.Keywords Palm fatty acid distillate Á Spent bleaching clay Á Palm oil by-product Á Soap J Am Oil Chem Soc (2019) 96: 329-336. Values within the same column having the same or without superscript are not significantly different (P > 0.05); Data are written as mean value and SD. 333 J Am Oil Chem Soc J Am Oil Chem Soc (2019) 96: 329-336

Co-valorization of agro-industry by-products: effect of citrus oil on the quality of soap derived from palm fatty acid distillate and spent bleaching clay

“…In addition, the selectivity of adsorption on the clay could also play a role. The found fatty acid composition of the oils and derived samples used in this study is consistent with published data [4,17,18].…”

“…The acidity of PFAD is even much higher because the aim of the distillation step is to withdraw all FFA in order to yield neutral palm oil. Accordingly, the saponification value of PFAD is higher than that of waste oil and of CPO, as the result of the decrease of the triacylglycerol portion in these samples, which is acting in favour of lower molecular weight compounds like FFA [17].…”

“…The slight increase noted in the case of PFAD is the result of harsh thermal processing conditions applied during the last step of physical refining (distillation). Indeed, the temperature is in the range of 240°C -or even higher-, and the trans-isomer is thermodynamically favored [2,17]. But the thirty-fold increase noted for the waste oil, which was not processed at a temperature higher than 95°C, could also be the result of the known cis-trans isomerization catalytic effect of phosphoric acid added prior to contacting with the bleaching clay, and/or that of the clay itself.…”

“…With SBC, the highest saponification yield is 56.1%, thus much lower than the 99.9% found in the case of pure fat substrates. The tested reaction conditions are thus not suitable for high conversion of the lipids retained within the SBC, probably because of the consumption of sodium hydroxide by other adsorbed -or absorbed-compounds, and also because of possible ion exchange at clay surface [17]. Further optimizing reaction conditions was out of the scope of this explorative work.…”

“…This last was used here. Based on the above results regarding the soap content, the best compounds were prepared, and total microbial counts were made before and after hand washing with the following products: SBC-soap (water content 30%), waste oil soap (water content 30%), PFAD-soap (water content 35%) and SBC-PFAD soap (SBC:PFAD ratio 1:3, and water content 20%) [17]. Average total viable microbial count (TVC) before hand washing with SBC-soap of 1.4±0.3 log cfu/cm 2 is reduced significantly after hand washing to 0.7±0.2 log cfu/cm 2 (Table 1), achieving a cleaning efficiency of 49±4%.…”