Controlled production of carbon nanofibers over cement clinker via oxidative dehydrogenation of acetylene by intrinsic carbon dioxide Chompunuch Warakulwit a,⇑ , Sudarat Yadnum a , Veerachart Paluka a , Oranit Phuakkong a , Malinee Niamlaem a , Kittisak Pongpaisanseree b , Sakprayut Sinthupinyo b , Jumras Limtrakul a,⇑ a Department of Chemistry, Faculty of Science, Center of Nanotechnology and NANOTEC Center of Excellence for Nanoscale Materials Design for Green Nanotechnology and Center for Advanced Studies in Nanotechnology and Its Applications in Chemical, Food and Agricultural Industries, Kasetsart University, Bangkok 10900, Thailand b Siam Research and Innovation Co., Ltd., 51 Moo 8, Tubkwang, Kaeng Khoi, Saraburi 18260, Thailand highlights  CO 2 was used to produce carbon nanofibers (CNFs) over cement clinker particles.  This approach delivers both CO 2 removal and high value-added cement products.  CNFs were obtained at 575–725 °C where Fe 3+ species are active for C 2 H 2 –CO 2 reaction.  The reaction temperature is a key parameter controlling the CNF diameter and amount. article info Article history: Available online xxxx Keywords: Cement Clinker Carbon nanofibers Chemical vapor deposition Oxidative dehydrogenation Carbon dioxide abstract In the course of the production of cement clinker, a high amount of carbon dioxide (CO 2 ) is released, caus- ing an undesirable impact on the environment. The in situ conversion of this CO 2 to carbon nanomaterials that can reinforce cement would be a novel approach delivering both on-site CO 2 removal and high value-added cement products. The production of carbon nanomaterials over cement clinker via oxidative dehydrogenation of acetylene by CO 2 is investigated. Chemical vapor deposition experiments were per- formed at 450–800 °C. Carbon nanofibers (CNFs) were obtained as the major product at 575–725 °C. This temperature range strongly relates to the temperatures at which active Fe 3+ species in clinker are abun- dant, indicating that these species are responsible for the reaction. The presence of CO 2 can effectively preserve the catalytic domains. As a consequence, with CO 2 the CNF diameters increase gradually in the temperature range of 600–700 °C and yet the product yield is higher. The characteristics and yield of CNFs strongly depend on the reaction temperature. Thus, fine-tuning this parameter is a simple and practical strategy for controlling the CNF diameter and amount in the CNF/clinker composite material and in turn the mechanical properties of the cement. The proper operating temperature with respect to CNFs with diameters in the order of ten nanometers and the maximum yield is 625 °C. By performing additional experiments we later found that approximately 10% of CO 2 produced by the cement industry is potentially reduced via the synthesis technique presented in this work. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Cement is the most widely used construction material of all. For the production of common Portland cement, cement clinker is produced by combusting raw materials, primarily limestone or cal- cium carbonate (CaCO 3 ), at a high temperature, more than 1000 °C [1]. During that process, a large volume of carbon dioxide (CO 2 ) is released, causing an undesirable impact on the environment [2]. Utilization of CO 2 can, in principle, be achieved via both non- conversion and conversion methods. In the first case, CO 2 is directly stored as a sustainable solvent or as a working fluid [3,4] while in the second case some valuable fuels, chemicals, and poly- mers [3,5,6] are produced from it. However, both routes are typi- cally not linked to the cement manufacture. Thus, they require extra cost to capture, separate, purify, store, and transport CO 2 to the target locations [3]. In terms of cost-efficiency, on-site CO 2 uti- lization is a better approach. http://dx.doi.org/10.1016/j.cej.2014.11.028 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. Tel./fax: +66 2562 5555x2190. E-mail addresses: fscicpn@ku.ac.th (C. Warakulwit), fscijrl@ku.ac.th (J. Limtrakul). Chemical Engineering Journal xxx (2014) xxx–xxx Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Please cite this article in press as: C. Warakulwit et al., Controlled production of carbon nanofibers over cement clinker via oxidative dehydrogenation of acetylene by intrinsic carbon dioxide, Chem. Eng. J. (2014), http://dx.doi.org/10.1016/j.cej.2014.11.028