Chemistry 1 (2015 8) 6-18 ~ ~ ~ УДК 661.9:547.4 The Nature and Mechanism of Selectivity Decrease of the Acid-catalyzed Fructose Conversion with Increasing the Carbohydrate Concentration Marina A. Smirnovaa Alexander A. Kondrasenkoa Valery E. Tarabankoa,b , Mikhail Yu. <...> Chernyaka and Nikolay V. Tarabankoa *, , * aInstitute of Chemistry and Chemical Technology SB RAS 50/24 Akademgorodok, Krasnoyarsk, 660036, Russia b Siberian Federal University 79 Svobodny, Krasnoyarsk, 660041, Russia Received 20.02.2015, received in revised form 01.03.2015, accepted 21.03.2015 To understand the effect of decreasing the process selectivity with increasing the carbohydrate concentration, the infl uence of levulinic acid and glucose additions on the fructose acid-catalyzed conversion was studied. <...> Levulinic acid yield signifi cantly decreases by initial addition of levulinic acid and glucose to the reaction mixture. <...> Humins were found to include structural fragments of levulinic acid, carbohydrates, and 5-hydroxymetylfurfural. <...> According to the mechanism suggested, the carbocation formed from fructose interacts with water producing target products (5-HMF and levulinic acid) or with levulinic acid or another carbohydrate molecules giving humins. <...> In these assumptions the levulinic acid formation in the process is a reaction of fi rst order with respect to substrate concentration, and the humic substance formation is a reaction of second order with respect to the initial carbohydrate concentration. <...> These two process characteristics, water to substrate ratio and the reaction orders distinction, are the reasons of decreasing the carbohydrate conversion selectivity with increasing the substrate concentration. <...> All rights reserved * Corresponding author E-mail address: veta@icct.ru homogeneous catalysis, levulinic acid, # 6 # Valery E. Tarabanko, Marina A. Smirnova…The Nature and Mechanism of Selectivity Decrease of the Acid-catalyzed… Природа и механизм снижения селективности кислотно-каталитической конверсии фруктозы с ростом концентрации углеводов М. <...> В первом случае образуются 5-ГМФ и левулиновая кислота, а в последнем – гумины. <...> В соответствии с этим механизмом левулиновая кислота образуется по реакции первого порядка по концентрации углевода, а гумины – по реакции второго порядка по начальной концентрации углевода. <...> One of the most common way to process hexose carbohydrates is their acid-catalyzed conversion in water medium to levulinic acid <...>