  Citation: Puspawiningtiyas, E.; Muraza, O.; Devianto, H.; Pratiwi, M.; Subagjo; Prakoso, T.; Krisnawan; Zaki, U.; Elizabeth, L.; Soerawidjaja, T.H.; et al. Sustainable Diesel from Pyrolysis of Unsaturated Fatty Acid Basic Soaps: The Effect of Temperature on Yield and Product Composition. Molecules 2022, 27, 667. https://doi.org/10.3390/ molecules27030667 Academic Editor: Adele Papetti Received: 30 November 2021 Accepted: 7 January 2022 Published: 20 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). molecules Article Sustainable Diesel from Pyrolysis of Unsaturated Fatty Acid Basic Soaps: The Effect of Temperature on Yield and Product Composition Endar Puspawiningtiyas 1,2 , Oki Muraza 3 , Hary Devianto 1 , Meiti Pratiwi 1,4 , Subagjo 1 , Tirto Prakoso 1,4 , Krisnawan 1 , Usamah Zaki 1 , Lidya Elizabeth 5 , Tatang H. Soerawidjaja 1,4 , Yohanes Andre Situmorang 4 and Antonius Indarto 1,4, * 1 Department of Chemical Engineering, Institut Teknologi Bandung, Ganesha Street No. 10, Bandung 40132, Indonesia; endartiyas@yahoo.com (E.P.); hardev@che.itb.ac.id (H.D.); mei@che.itb.ac.id (M.P.); subagjo@che.itb.ac.id (S.); tirto@che.itb.ac.id (T.P.); krisnawanj@gmail.com (K.); usamah.zaki96@gmail.com (U.Z.); thsoerawidjaja@gmail.com (T.H.S.) 2 Department of Chemical Engineering, Universitas Muhammadiyah Purwokerto, Purwokerto 53182, Indonesia 3 Research & Technology Innovation, Pertamina, Sopo Del Building, 51st Fl. Jl. Mega Kuningan Barat, Jakarta Pusat 12950, Indonesia; oki.muraza@pertamina.com 4 Departement of Bioenergy Engineeringand Chemurgy, Institut Teknologi Bandung, Jalan Let. Jen. Purn. Dr. (HC). Mashudi No. 1 Sumedang, Kota Bandung 45363, Indonesia; yohanes.andrest@gmail.com 5 Department of Chemical Engineering, Politeknik Negeri Bandung, Gegerkalong Hilir Street, Bandung 40559, Indonesia; lidya.elizbth@gmail.com * Correspondence: indarto_antonius@yahoo.com Abstract: The production of sustainable diesel without hydrogen addition remains a challenge for low-cost fuel production. In this work, the pyrolysis of unsaturated fatty acid (UFA) basic soaps was studied for the production sustainable diesel (bio-hydrocarbons). UFAs were obtained from palm fatty acids distillate (PFAD), which was purified by the fractional crystallization method. Metal hydroxides were used to make basic soap composed of a Ca, Mg, and Zn mixture with particular composition. The pyrolysis reactions were carried out in a batch reactor at atmospheric pressure and various temperatures from 375 to 475 ◦ C. The liquid products were obtained with the best yield (58.35%) at 425 ◦ C and yield of diesel fraction 53.4%. The fatty acids were not detected in the pyrolysis liquid product. The gas product consisted of carbon dioxide and methane. The liquid products were a mixture of hydrocarbon with carbon chains in the range of C 7 and C 20 containing n-alkane, alkene, and iso-alkane. Keywords: pyrolysis; unsaturated fatty acid; basic soap; metal hydroxide; biohydrocarbon 1. Introduction Increased energy demand and issues related to environmental concerns constitute a strong reason many countries have chosen to use alternative and renewable energy technologies. Biohydrocarbon or liquid hydrocarbon are renewable fuels derived from any material originating from biological matters [1], including biomass [2], lignocellulose [3], triglycerides, or fatty acids [4,5]. There are many reasons for the strong interest in biofuels, among others their easy availability from common biomass. Biofuels represent a carbon dioxide cycle in combustion. They have considerable environmentally friendly potential, and they are biodegradable and contribute to sustainability [6]. Nowadays, the main processes used to obtain biofuels from vegetable oils are transesterification and thermal cracking (pyrolysis) or thermal-catalytic cracking (catalytic pyrolysis) [7]. Biodiesel, a promising biofuel, is made from renewable biological sources, such as vegetable oils and animal fats, by chemically reacting oil or fat with an alcohol (transesterification) in the presence of a homogeneous and heterogeneous catalysts [8]. Biodiesel is renewable, Molecules 2022, 27, 667. https://doi.org/10.3390/molecules27030667 https://www.mdpi.com/journal/molecules