Preparation of Chloromethylated Pitch–Based Hyper–Crosslinked Polymers and An Immobilized Acidic Ionic Liquid as A Catalyst for the Synthesis of Biodiesel

Abstract

Hyper-crosslinking polymers and its immobilized acid ionic liquid catalyst were prepared using cheap pitch, as a monomer, through hyper-crosslinking reactions and allyl chloride, as a chlorine source, for chloromethylation and further grafting with imidazole and functionalizing with sulfonic acid. The polymers were characterized by FE-SEM, FTIR, TG, and nitrogen sorption. The grafting ratios of the chloromethylated pitch-based hyper-crosslinked polymer (HCPpitch–CH2–Cl) and immobilized acid ionic liquid [HCPpitch–Im–Pros][Tos] were 3.5 mmol/g and 3.0 mmol/g, and the BET specific surface areas were 520 m2/g and 380 m2/g, respectively. This strategy provides an easy approach to preparing highly stable and acid functionalized mesoporous catalysts. The immobilized acidic ionic liquid was used as a catalyst for the esterification of oleic acid and methanol to synthesize biodiesel. The results demonstrated that under the optimal conditions of an alcohol to acid molar ratio of 7:1, ionic liquid to oleic acid molar ratio of 0.12, and a reaction time of 3 h at atmospheric pressure, the yield of methyl oleate can reach up to 93%. Moreover, the catalyst was reused five times without the yield decreasing significantly. This study shows that [HCPpitch–Im–Pros][Tos] is a robust catalyst for the synthesis of biodiesel.

Recent Advances of Biodiesel Production Using Ionic Liquids Supported on Nanoporous Materials as Catalysts: A Review

“…According to Granados et al (2007) and Coenen (1986), a minimum pore diameter of 3.5 nm is preferable for producing biodiesel. However, high conversion and yield after multiple reuses was reported by Pei et al (2019), using an average pore diameter of 2.56 nm. Therefore, a pore diameter of >2.5 nm should be considered to achieve high yields under mild reaction conditions.…”

“…The post-modification method was used in the first six studies Noshadi et al, 2014;Pan et al, 2016Pan et al, , 2019Feng et al, 2017;Pei et al, 2019), in which the IL is supported on an as-synthesized polymer. This method is based on three consecutive steps including polymer synthesis, modification through quaternary ammonization, and ion exchange.…”

Hypercrosslinked Ionic Polymers with High Ionic Content for Efficient Conversion of Carbon Dioxide into Cyclic Carbonates

“…The experimental results (Figure 1b and Table S2) show that when increasing the mass ratio of H 2 SO 4 /HCP from 0.5 to 1.5, a positive effect was achieved on the chloromethyl content of HCP-CH 2 -Cl-X (2.0-3.1 mmol g −1 ). However, when the mass ratio of H 2 SO 4 /HCP increased to 2.5, the chloromethyl contents decreased to 1.7 mmol g −1 because the excessive sulfuric acid generated more sulfonation reactions of the benzene ring of HCP, resulting in the passivation of the benzene ring and decreasing the chloromethyl content [35]. In addition, the specific surface area of HCP-CH 2 -Cl-X decreased from 783 m 2 g −1 to 530 m 2 g −1 when the mass ratio of H 2 SO 4 /HCP increased from 0.5 to 1.5, which was attributed to the numerous pores that were occupied by the grafted chloromethyl group.…”

Low‐Cost Hypercrosslinked Polymers by Direct Knitting Strategy for Catalytic Applications

“…Because the presence of a long bridge (composed by the imidazolium and alkyl chain) between the SO 3 H group and the HCP support, the supported acid ionic liquid can be an alternative choice when an acid catalyst is needed. [ 80 ]…”