Selective Microwave‐Assisted Pyrolysis of Cellulose towards Levoglucosenone with Clay Catalysts

Abstract

Levoglucosenone (anhydrosugar) is one of the most promising chemicalp latforms derived from the pyrolysis of biomass. It is ac hiral building block for pharmaceuticals as wella sa ni ntermediate in the production of solvents and polymers. Therefore, the development of cost-efficient, low-energy production methods is vital for af uture sustainable biorefinery.H ere, a novel, green approach to the production of levoglucosenone was developedb yu sing am icrowave (MW)-assisted pyrolysis of cellulose in the presence of readily available clays. It was shown that natural and pillared clays in the presence of MW irradiation significantly increaset he yield of levoglucosenone from cellulose. Both the water content and the presence of acid centres are critical characteristics that influence the yield and distributiono fc atalysed products.Au nique experiment was designed by using as ynergetic effect between different types of catalysts, which enhanced the levoglucosenone yield to 12.3 wt %with63% purity.Bio-oil is ac omplex organic mixture resultingf rom thermal processing (pyrolysis) of biomass and biowastea nd represents an alternative renewable source for chemicals and fuels. The majority of individual compounds in bio-oil are multifunctional oxygen-containing chemicals. Someofthem are attractive plat-form molecules ready for industrial use without any prefunctionalization. [1] These platform molecules could form the core of as ustainable and efficient biorefinery.C urrently,o ne of the biggest challenges for such ab iorefinery is separation of the complex bio-oil into individual compounds. The direct distillation of the oxygen-containing compounds is impossible, and the applicationo fc hromatography columns is an expensive decision for the large-scale chemical industry.Apossible solution is selectivei nsitu targeting of the desired compounds duringp yrolysis of biomass (which typically contains hemicellulose, cellulose and lignin). At present,m ost of the problems associated with refiningh emicellulose have been addressed, [2] whereas refining crosslinked lignin requires significant further developments;h ence our focus on cellulose. Pyrolysis of cellulose to ac omplex mixture of chemicals is already developed, but ac ontrollable and sustainable production of the platform molecules levoglucosenone( LGO) and 5-hydroxymethylfurfural (5-HMF) is not. Conventional pyrolysis of cellulose proceeds at high temperatures (T > 360 8C), inducing secondary reactions and therefore producing ac omplex mixture of products.One of the ways to increase selectivity during pyrolysis is catalysis. [3] Natural aluminosilicatess uch as zeolitesa re widely reported to preferentially catalyse the conversion of biomass to aromatic compounds. [4,5] However,a lthough cost-efficient and readily available, clays have not attracted significant attention. Pillared clays (a class of swollen clays modified with avariety of large polynuclear hydroxo-complexes) are of particular interest. [6] Another way to improvep yrolysis selectivity is the application...

Effect of Exchangeable Cation in Clays on the Yield and Quality of the Bio-Oil during Microwave Pyrolysis of Cellulose

“…In our previous publication, we have shown that clay minerals, which are widely used for water treatment [17,18], can be excellent absorbers of MWs, demonstrating high values of maximum heating rate [1]. MW-assisted pyrolysis of cellulose mixed with bentonite resulted in 25 wt.% enhancement of bio-oil.…”

“…Bio-oil is a complex mixture of organic chemicals obtained through the pyrolysis of biomass. It represents an attractive source for the production of sustainable fuels and renewable chemicals [1]. Bio-oil catalytical upgrading for the production of valuable chemicals has been widely reported [2][3][4].…”

“…On the other hand, an application of alternative types of heating, including microwave (MW)-assisted pyrolysis, is known to improve the yield of bio-oil and its quality [1,11]. During the biomass pyrolysis, produced gases and volatiles do not interact with MW irradiation due to their low density.…”

“…Additionally, MW heating of biomass sometimes is problematic due to its weak interaction with biopolymers in the temperature range below their softening [13,15]. Such low-efficiency interaction usually results in lower yields of MW pyrolysis oil compared to those of conventional fast pyrolysis and, therefore, reduces the efficiency and sustainability of the production of valuable chemicals [1].…”

Selectively Production of Levoglucosenone from Cellulose via Catalytic Fast Pyrolysis

“…Therefore, it is essential to develop a suitable catalyst for cellulosic fast pyrolysis to achieve LGO with high yields. It has been proposed that the catalysts currently used in the cellulosic pyrolysis to produce LGO include ionic liquids, liquid inorganic acids and solid acids (Doroshenko et al, 2019). Although ionic liquids can increase the yield of…”