FeCl3-Modified Carbonaceous Catalysts from Orange Peel for Solvent-Free Alpha-Pinene Oxidation

Adrianna Kamińska,Joanna Sreńscek-Nazzal,Agnieszka Wróblewska,Piotr Miądlicki,Rafał Jan Wróbel,Jarosław Serafin,Karolina Kiełbasa

doi:10.3390/ma14247729

Abstract

The work presents the synthesis of FeCl3-modified carbonaceous catalysts obtained from waste orange peel and their application in the oxidation of alpha-pinene in solvent-free reaction conditions. The use of waste orange peel as presented here (not described in the literature) is an effective and cheap way of managing this valuable and renewable biomass. FeCl3-modified carbonaceous materials were obtained by a two-stage method: in the first stage, activated carbon was obtained, and in the second stage, it was modified by FeCl3 in the presence of H3PO4 (three different molar ratios of these two compounds were used in the studies). The obtained FeCl3-modified carbon materials were subjected to detailed instrumental studies using the methods FT-IR (Fourier-transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), EDXRF (Energy Dispersive X-ray Fluorescence) and XPS (X-ray Photoelectron Spectroscopy), while the textural properties of these materials were also studied, such as the specific surface area and total pore volume. Catalytic tests with the three modified activated carbons showed that the catalyst obtained with the participation of 6 M of FeCl3 and 3 M aqueous solutions of H3PO4 was the most active in the oxidation of alpha-pinene. Further tests (influence of temperature, amount of catalyst, and reaction time) with this catalyst made it possible to determine the most favorable conditions for conducting oxidation on this type of catalyst, and allowed study of the kinetics of this process. The most favorable conditions for the process were: temperature of 100 °C, catalyst content of 0.5 wt% and reaction time 120 min (very mild process conditions). The conversion of the organic raw material obtained under these conditions was 40 mol%, and the selectivity of the transformation to alpha-pinene oxide reached the value of 35 mol%. In addition to the epoxy compound, other valuable products, such as verbenone and verbenol, were formed while carrying out the process.

Highlights

Obtaining carbonaceous materials from biomass allows the utilization of raw materials that have not been used so far and is a new way to utilize biomass waste [3]
The raw material used for the activated carbon (AC) production was orange peel (Valencia, Spain)
Summarizing our research presented in this work, it can be seen that we were able to obtain active catalysts for alpha-pinene oxidation with oxygen

Summary

Introduction

There has been a growing interest in research on the use of industrial and agricultural waste to produce of activated carbons [1]. The availability and ease of the obtaining this waste makes it a good source of raw materials for the production of carbonaceous materials [2]. The Food and Agriculture Organization (FAO) estimates that the world’s citrus fruit production is close to 88 million tons per year, of which 80% is oranges [4]. Brazil is the major citrus-processing country (Brazil processes 47% of the world’s citrus fruits). These fruits are mainly processed into juices. The citrus fruit processing industry generates huge amounts of waste, with citrus peel accounting for as much as 60 to 65% [6]. A solution to this problem may be the production of useful materials from orange peel that can be used in many areas of industry

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