Catalytic methyl esterification of colophony over ZnO/SFCCR with subcritical CO2: catalytic performance, reaction pathway and kinetics.

Xubin Wang,Jiezhen Liang,Xiaojie Wei,Han Xiao,Linlin Wang,Xiaopeng Chen,Dan Zhou

doi:10.1098/rsos.172124

Abstract

A heterogeneous catalyst (ZnO/SFCCR) composed of ZnO supported on spent fluid cracking catalyst by wet impregnation was synthesized and applied to the esterification of colophony acids with methanol under subcritical CO2 conditions. The catalyst was characterized by SEM-EDS, BET, ICP, FTIR, XRD and Py-IR. An experimental set-up involving a new injection technique was designed to promote the heterogeneous methyl esterification, and the subcritical CO2 played a role in auxiliary acid catalysis (a pH range of 3.54–3.91), increasing the lifespan of ZnO/SFCCR, reducing the viscosity of the system to promote gas–liquid mass transfer. A maximum conversion rate of 97.01% was obtained in a relatively short time of 5 h. Kinetic experiments were performed from 190 to 220°C using a special high-temperature sampling device and analysing aliquots with high-performance liquid chromatography. A new reaction pathway, involving methyl abietate, methyl dehydroabietate, methyl neoabietate and methyl palustrate along with other kinds of colophony acids, was developed. The kinetic parameters were obtained using the Levenberg–Marquardt nonlinear least-squares method, and the activation energies for the isomerizations of neoabietic and palustric acids and for the methyl esterification of neoabietic, abietic, palustric and dehydroabietic acids were found to be 107.09, 113.95, 68.99, 49.85, 75.43 and 59.20 kJ mol−1, respectively. The results from the kinetic model were in good agreement with experimental values.

Highlights

There has been a wealth of interdependent research focused on creating high-value products from renewable biomass as fossil fuel resources deplete [1]
The surface morphologies of the SFCCR and ZnO/SFCCR were analysed by scanning electron microscopy (SEM) and the surface elemental compositions were determined by energy-dispersive spectroscopy (EDS), with the results shown in figure 2 and electronic (a) rsos.royalsocietypublishing.org R
The as-received SFCCR particles were clogged with internal coke deposits, as indicated by the microphotograph in figure 2b

Summary

Introduction

There has been a wealth of interdependent research focused on creating high-value products from renewable biomass as fossil fuel resources deplete [1]. Colophony is a natural resin obtained by distilling pine resin, which comprises greater than 90% resin acids with a single carboxylic group [2,3]. Colophony can be modified by changing the carboxyl group structure to broaden the range of applications and increase its value [4,5]. Fluid catalytic cracking is an important process in petroleum refining, which generates large quantities of spent fluid cracking catalyst (SFCCR)—approximately 160 000 tons [8]. SFCCR has been reported as a material for use in sorbent and construction applications; SFCCR has rarely been employed as a catalyst [10,11]. As SFCCR is composed primarily of SiO2 and Al2O3 and has a stable molecular sieve structure with a large specific surface area, it may find use as a suitable catalytic support

Methods

Results

Conclusion