Daniel Mourant

Mediating acid-catalyzed conversion of levoglucosan into platform chemicals with various solvents

Acid-catalyzed conversions of levoglucosan have been investigated in mono-alcohols, poly-alcohols, water, chloroform, toluene, acetone, N,N-dimethyl formamide, dimethyl sulfoxide and some mixed solvents, aiming to mediate conversion of sugars into platform chemicals with solvents. The mono-alcohols can stabilize soluble polymers and thus suppress formation of insoluble polymers. Water does not have such an effect, leading to lower yields of levulinic acid. Chloroform cannot effectively dissolve levoglucosan, leading to “dissolving” of levoglucosan in the catalyst and the consequent rapid polymerization. Acetone reacted with sugars, forming substantial amounts of polymer. N,N-Dimethyl formamide poisoned the acid resin catalyst, leading to negligible conversion of levoglucosan. Dimethyl sulfoxide (DMSO) mainly catalyzed the conversion of levoglucosan into 5-(hydroxymethyl)furfural (HMF), 2,5-furandicarboxaldehyde, and the sulfur ether of HMF. DMSO has a low ability to transfer protons, which helps to avoid further contact of HMF with catalytic sites and stabilizes HMF.

Acid-catalyzed conversion of mono- and poly-sugars into platform chemicals: Effects of molecular structure of sugar substrate

Hydrolysis/pyrolysis of lignocellulosic biomass always produces a mixture of sugars with distinct structures as intermediates or products. This study tried to elucidate the effects of molecular structure of sugars on their acid-catalyzed conversions in ethanol/water. Location of carbonyl group in sugars (fructose versus glucose) and steric configuration of hydroxyl groups (glucose versus galactose) significantly affected yields of levulinic acid/ester (fructose>glucose>galactose). The dehydration of fructose to 5-(hydroxymethyl)furfural produces much less soluble polymer than that from glucose and galactose, which results in high yields of levulinic acid/ester from fructose. Anhydrate sugar such as levoglucosan tends to undergo the undesirable decomposition to form less levulinic acid/ester. Catalytic behaviors of the poly-sugars (sucrose, maltose, raffinose, β-cyclodextrins) were determined much by their basic units. However, their big molecular sizes create the steric hindrance that significantly affects their followed conversion over solid acid catalyst.

Production of value-added chemicals from bio-oil via acid catalysis coupled with liquid–liquid extraction

Sugar/sugar derivatives in bio-oil can be effectively separated from aromatics via water/chloroform extraction. Subsequent acid-treatment in methanol converts the sugars into levulinic acid/ester and the sugar derivatives into fuel additives. Further extraction with CH2Cl2/CHCl3 could efficiently separate methyl levulinate and levulinic acid from other products.

Esterification of bio-oil from mallee (Eucalyptus loxophleba ssp. gratiae) leaves with a solid acid catalyst: conversion of the cyclic ether and terpenoids into hydrocarbons.

Bio-oil from pyrolysis of mallee (Eucalyptus loxophleba ssp. gratiae) leaves differs from that obtained with wood by its content of cyclic ethers, terpenoids and N-containing organic compounds. Upgrading of the leaf bio-oil in methanol with a solid acid catalyst was investigated and it was found that the N-containing organics in the bio-oil lead to deactivation of the catalyst in the initial stage of exposure and have to be removed via employing high catalyst loading to allow the occurrence of other acid-catalysed reactions. Eucalyptol, the main cyclic ether in the bio-oil, could be converted into the aromatic hydrocarbon, p-cymene, through a series of intermediates including α-terpineol, terpinolene, and α-terpinene. Various steps such as ring-opening, dehydration, isomerisation, and aromatization were involved in the conversion of eucalyptol. The terpenoids in bio-oil could also be converted into aromatic hydrocarbons that can serve as starting materials for the synthesis of fine chemicals, via the similar processes.

Formation of coke during the esterification of pyrolysis bio-oil

Coke formation during the esterification of bio-oil in alcohols and water over a solid acid catalyst Amberlyst 70 has been investigated. The amounts of coke formed from the acid-treatment of bio-oil in various alcohols are half of that in water. Alcohols stabilize the major components in bio-oil such as sugars, furans, aldehydes, carboxylic acids and phenolics. On the other hand, water promotes the polymerisation of these components. In addition, experimental parameters also affect the coke formation during acid-treatment of bio-oil in alcohols. The elevated reaction temperature, long residence time, and high dosage of catalyst significantly promoted coke formation. The soluble polymeric material and insoluble polymeric material was characterized with FI-IR and UV-florescence spectroscopies. The results show that the coke formed is highly aromatic. The aromatics in bio-oil have a significant contribution to the formation of coke during the esterification of bio-oil.