Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Ethyl esters from waste oil: Reaction data of non-catalytic hydroesterification at pressurized conditions and purification with sugarcane bagasse ash Jhessica Marchini Fonseca a , Lúcio Cardozo-Filho b,c , Joel Gustavo Teleken d , Camila da Silva a,e, ⁎ a Programa de Pós-Graduação em Bioenergia, Universidade Estadual do Maringá (UEM), Av. Colombo 5790, Maringá, PR, 87020-900, Brazil b Programa de Pós-graduação em Engenharia Química, Universidade Estadual de Maringá (UEM), Av. Colombo, 5790, 87020-900, Maringá, PR, Brazil c Departamento de Agronomia, Centro Universitário da Fundação de Ensino Octávio Bastos (UNIFEOB), Av. Dr. Otávio Bastos, 2439, 13874-149, São João da Boa Vista, SP, Brazil d Departamento de Engenharia e Ciências Exatas, Universidade Federal do Paraná (UFPR), R. Pioneiro 2153, Palotina, PR, 85950-000, Brazil e Departamento de Tecnologia, Universidade Estadual de Maringá (UEM), Av. Ângelo Moreira da Fonseca 180, Umuarama, PR, 87506-370, Brazil ARTICLE INFO Keywords: Hydroesterification Pressurized conditions Waste oil Adsorption Sugarcane bagasse ash ABSTRACT The reaction data of hydroesterification of waste oil, under pressurized conditions, were collected and the ad- sorption of compounds from ester mixture by sugarcane bagasse ash was evaluated. The reactions were con- ducted in a continuous reactor to evaluate of the effect of temperature and residence time. In the hydrolysis, the evaluated variables promoted an increase in free fatty acid (FFA) formation. However, at the highest tem- perature evaluated (320 °C), the equilibrium was reached after 12 min, obtaining 91.68% of FFA. Temperature and residence time increased the FFA conversion, although at 300 °C the conversion was stabilized after 10 min and ester yield after 20 min, thereby obtaining a 96.42% of FFA conversion with 74% of ester content. In the adsorption, the percentage of adsorbent and contact time varied for the FFA removal and polar compounds (PC). The adsorption equilibrium was reached with 12.5 wt% of ash and after 8 h 33.22% of FFA and 56.31% of PC were absorbed. Adsorption in four successive beds was also evaluated, changing the adsorbent mass every 8 h, maintaining the same adsorbate. The results indicated the removal of 43.89% of FFA and 73.08% of PC after the 4th bed. 1. Introduction Biodiesel, a mixture of fatty acid esters, has received attention be- cause it is nontoxic, has high combustion efficiency and degradability, low emissions of carbon monoxide, particulate matter, and unburned hydrocarbons, contains less sulfur and aromatic compounds, recycles the carbon dioxide released in combustion, and is obtained from re- newable sources [1]. Recent studies have reported a two-step process for obtaining bio- diesel: hydrolysis of triglycerides and subsequent esterification of the fatty acids obtained. The two-step reaction is commonly catalyzed by chemical or enzymatic catalysts. Homogeneous acids are superior in catalytic activity when compared to heterogeneous catalysts, and de- crease mass-transfer limitations, due to the greater interaction between the catalyst and the substrates, but they have the disadvantage of complex purification processes, generating high volumes of liquid effluents [2,3]. The process catalyzed by enzymes requires milder temperatures in the hydrolysis step, but requires long reaction times [4]. In esterification, the enzymes are susceptible to alcohol deactiva- tion, reducing the conversion rates [5]. An alternative to the catalytic processes is the hydroesterification without the presence of catalysts, using subcritical water and an alcohol under sub- or supercritical conditions [6–10], which requires mild conditions of temperature and pressure, when compared to the process in only one step, thus avoiding the possible degradation of the products [6] The removal of the glycerol in the hydrolysis allows esterification to occur with smaller proportions of alcohol [11], and avoids the reaction of this coproduct with alcohol or esters, thus avoiding the formation of other compounds and obtaining better quality biodiesel [7,12]. The subcritical state of the water is in the temperature range be- tween 100 and 374 °C, and pressures of 0.4 to 20 MPa [13]. As the water temperature is high, a decrease in polarity, viscosity, and surface https://doi.org/10.1016/j.jece.2018.07.044 Received 17 May 2018; Received in revised form 26 June 2018; Accepted 22 July 2018 ⁎ Corresponding author at: Departamento de Tecnologia, Universidade Estadual de Maringá (UEM), Av. Ângelo Moreira da Fonseca 180, Umuarama, PR, 87506- 370, Brazil. E-mail address: camiladasilva.eq@gmail.com (C.d. Silva). Journal of Environmental Chemical Engineering 6 (2018) 4988–4996 Available online 23 July 2018 2213-3437/ © 2018 Elsevier Ltd. All rights reserved. T