Investigation of the kinetics and mechanism of the glycerol chlorination reaction using gas chromatography-mass spectrometry

As a primary by-product in biodiesel production, glycerol can be used to prepare an important fine chemical, epichlorohydrin, by the glycerol chlorination reaction. Although this process has been applied in industrial production, unfortunately, less attention has been paid to the analysis and separation of the compounds in the glycerol chlorination products. In this study, a convenient and accurate method to determine the products in glycerol chlorination reaction was established and based on the results the kinetic mechanism of the reaction was investigated. The structure of main products, including 1,3- -dichloropropan-2-ol, 2,3-dichloropropan-1-ol, 3-chloro-1,2-propanediol, 2-chloro- 1,3-propanediol and glycerol was ascertained by gas chromatography-mass spectrometry and the isomers of the products were distinguished. Apidic acid was considered as the best catalyst because of its excellent catalytic effect and high boiling point. The mechanism of the glycerol chlorination reaction was proposed and a new kinetic model was developed. Kinetic equations of the process in the experimental range were obtained by data fitting and the activation energies of each tandem reaction were 30.7, 41.8, 29.4 and 49.5 kJ mol-1, respectively. This study revealed the process and mechanism of the kinetics and provides the theoretical basis for engineering problems. Kao primarni sporedni proizvod u proizvodnji biodizela, glicerol se moze upotrebiti za sintezu vazne supstance epihlorhidrina, koji nastaje kao intermedijerni proizvod u procesu hlorovanja glicerola. Mada se taj proces koristi u industrijskim uslovima, mala paznja je bila poklonjena analizi i separaciji hloriranih proizvoda reakcije. U ovom radu je ispitana kinetika i mehanizam reakcije i opisan odgovarajuci i precizan metod odredjivanja proizvoda reakcije. Primenom gasno-masene spektrometrije utvrdjeno je da proizvod reakcije sadrzi 1,3-dihloro 2-propanol, 2,3-dihloro 1-propanol, 3-hloro-1,2-propandiol, 2-hloro-1,3-propandiol i glicerol. Zbog visoke tacke kljucanja i dobrih katalitickih osobina adipinska kiselina se pokazala kao najbolji katalizator u ovoj reakciji. Pretpostavljen je mehanizam i razvijen je novi kineticki model ove reakcije. Fitovanjem eksperimentalnih podataka dobijene su sledece vrednosti za energije aktivacije pojedinacnih stupnjeva: 30,7, 41,8, 29,4 i 49,5 kJ mol-1. Ovaj rad, razjasnjavajuci kinetiku i mehanizam procesa, postavlja teorijsku osnovu za inzenjerizaciju ovog procesa.