Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser Insight into the catalytic conversion of palm oil into biodiesel using Na + /K + trapped muscovite/phillipsite composite as a novel catalyst: Effect of ultrasonic irradiation and mechanism Mostafa R. Abukhadra a,b,* , Mohamed Abdel Salam c , Sherouk M. Ibrahim a,d a Materials Technologies and Their Applications Lab, Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef City, Egypt b Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef City, Egypt c Chemistry Department, Faculty of Science, King Abdulaziz University, P.O Box 80200, Jeddah 21589, Saudi Arabia d Chemistry Department, Faculty of Science, Beni-Suef University, Beni-Suef City, Egypt ARTICLE INFO Keywords: Muscovite Zeolite Composite Transesterification Biodiesel Ultrasonic ABSTRACT A novel composite of muscovite/synthetic zeolite (phillipsite) (Mu/Pz) was synthesized in an open system by the alkaline modification at 150 °C under stirring of speed 600 rpm for 22 h. The composite was characterized as a novel, low cost and effective basic catalyst in the transesterification conversion of palm oil into biodiesel. The catalytic properties of Mu/PZ were studied based on several controlling factors by normal stirring and ultrasonic irradiation as mixing techniques. The maximum biodiesel yield obtained by normal stirring is 94% and was accomplished after adjusting the controlling factors at 180 min as conversion interval, 20:1 as the incorporated methanol-to-oil molar ratio, 100 °C as reaction temperature, 5 wt, % as a Mu/Pz loading and 1300 rpm as a stirring speed. The influence of ultrasonic irradiation was addressed within a range from power 20% to power 60% and the best results were achieved using ultrasonic power of 60%. At the same conducting conditions of temperature, Mu/Pz loading, and the incorporated methanol-to-oil ratio, the biodiesel yield attained 97.8% after 90 min by using ultrasonic irradiation as a mixing method at 60% power. The stability study of Mu/Pz catalyst revealed high reusability properties for five cycles using three regeneration solvents of distilled water, methanol and acetone with clear preferences for using the organic solvents. The specifications of the obtained biodiesel samples by both methods match the biodiesel requirements of the STM-D-6571 as well as the EN-14214 inter- national standards. 1. Introduction Increasing the world concerns by the environmental and health hazards of traditional fuels as well as the continuous depletion in their resources make the developing of renewable and clean fuels the main target for the modern world [1–4]. Transesterification reactions of ed- ible and non-edible oils into biodiesel attracted the considerations as one of the best environmental substitute solutions for fossil fuel re- sources [5–7]. Environmentally, biodiesel is of biodegradability prop- erties, no toxic emission, no CO 2 production, and low shots [8–10]. Technically, it exhibits excellent viscosity, lubricity, high octane number, and high flash point so it can be applied directly in the engines or mixed with petrodiesel [4,11]. The transesterification production of biodiesel is generally conducted in the presences of homogenous or heterogeneous catalysts [12,13]. The homogeneous transesterification reactions can result in high biodiesel yield but it is of several drawbacks. These drawbacks related to the high cost of the used che- micals, the complicated separation process of the used homogenous catalysts for the obtained biodiesel and the associated toxic by-products [4,7]. Thus, the heterogeneous catalysts were addressed to avoid the main drawbacks of homogenous catalysts as they are of low preparation costs, high purity, high reusability and simple in separation [2,12]. The reported weak interaction and high immiscibility between solid cata- lysts and the present liquid phases represent the main challenge in designing effective heterogeneous transesterification system as it re- duces the conversion rate [11,14]. Several studies have been accom- plished to enhance the mixing properties between the reacting com- ponents by ultrasonic irradiation [11,15]. The ultrasonic mixing commonly accompanied by cavitation phenomena which resulted in creation of microbubbles at the interface area between the used alcohol and oil [11,15]. The continuous collapse of such microbubbles provides https://doi.org/10.1016/j.rser.2019.109346 Received 11 May 2019; Received in revised form 15 August 2019; Accepted 19 August 2019 * Corresponding author. Materials Technologies and Their Applications Lab, Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef City, Egypt. E-mail address: abukhadra89@science.bsu.edu.eg (M.R. Abukhadra). Renewable and Sustainable Energy Reviews 115 (2019) 109346 1364-0321/ © 2019 Elsevier Ltd. All rights reserved. T