Valorization of lignocellulosic fibres of paper waste into levulinic acid using solid and aqueous Brønsted acid

Chen, Season S.,Wang, Lei,Yu, Iris K.M.,Tsang, Daniel C.W.,Hunt, Andrew J.,Jé,rô,me, Franç,ois,Zhang, Shicheng,Ok, Yong Sik,Poon, Chi Sun Elsevier 2018 Bioresource technology Vol.247 No.-

<P><B>Abstract</B></P> <P>This study aims to produce levulinic acid (LA) from paper towel waste in environment-friendly and economically feasible conditions, and evaluate the difference using solid and aqueous Brønsted acids. Direct dehydration of glucose to LA required sufficiently strong Brønsted acidity, where Amberlyst 36 demonstrated rapid production of approximately 30Cmol% of LA in 20min. However, the maximum yield of LA was limited by mass transfer. In contrast, the yield of LA gradually increased to over 40Cmol% in 1M H<SUB>2</SUB>SO<SUB>4</SUB> at 150°C in 60min. The SEM images revealed the conversion in dilute acids under microwave at 150°C resulting in swelling structures of cellulose, which were similar to the pre-treatment process with concentrated acids. Further increase in reaction temperature to 200°C significantly shortened the reaction time from 60 to 2.5min, which saved the energy cost as revealed in preliminary cost analysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 30% of levulinic acid (LA) yielded from paper towel over Amberlyst 36 in 20min. </LI> <LI> Maximum yield of LA was comparable using dilute sulphuric acid at 150 and 200°C. </LI> <LI> Cellulose underwent swelling in dilute acid with microwave heating at 150°C. </LI> <LI> Conversion at 200°C shortened reaction time and reduced total energy consumption. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Catalytic valorization of starch-rich food waste into hydroxymethylfurfural (HMF): Controlling relative kinetics for high productivity

Yu, Iris K.M.,Tsang, Daniel C.W.,Yip, Alex C.K.,Chen, Season S.,Wang, Lei,Ok, Yong Sik,Poon, Chi Sun Elsevier 2017 Bioresource technology Vol.237 No.-

<P><B>Abstract</B></P> <P>This study aimed to maximize the valorization of bread waste, a typical food waste stream, into hydroxymethylfurfural (HMF) by improving our kinetic understanding. The highest HMF yield (30mol%) was achieved using SnCl<SUB>4</SUB> as catalyst, which offered strong derived Brønsted acidity and moderate Lewis acidity. We evaluated the kinetic balance between these acidities to facilitate faster desirable reactions (i.e., hydrolysis, isomerization, and dehydration) relative to undesirable reactions (i.e., rehydration and polymerization). Such catalyst selectivity of SnCl<SUB>4</SUB>, AlCl<SUB>3</SUB>, and FeCl<SUB>3</SUB> was critical in maximizing HMF yield. Higher temperature made marginal advancement by accelerating the undesirable reactions to a similar extent as the desirable pathways. The polymerization-induced metal-impregnated high-porosity carbon was a possible precursor of biochar-based catalyst, further driving up the economic potential. Preliminary economic analysis indicated a net gain of USD 43-236 per kilogram bread waste considering the thermochemical-conversion cost and chemical-trading revenue.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Valorization of bread waste resulted in 30mol% HMF using SnCl<SUB>4</SUB> as catalyst. </LI> <LI> Catalyst selectivity towards formation reactions improved maximum HMF yield. </LI> <LI> Balance between Brønsted acidity and Lewis acidity controlled catalyst selectivity. </LI> <LI> Temperature increase reduced reaction time but marginally enhanced HMF yield. </LI> <LI> Sn-deposited porous humins may serve as precursor of biochar-based catalyst. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Polar aprotic solvent-water mixture as the medium for catalytic production of hydroxymethylfurfural (HMF) from bread waste

Yu, Iris K.M.,Tsang, Daniel C.W.,Chen, Season S.,Wang, Lei,Hunt, Andrew J.,Sherwood, James,De Oliveira Vigier, Karine,Jé,rô,me, Franç,ois,Ok, Yong Sik,Poon, Chi Sun Elsevier 2017 Bioresource technology Vol.245 No.1

<P><B>Abstract</B></P> <P>Valorisation of bread waste for hydroxymethylfurfural (HMF) synthesis was examined in dimethyl sulfoxide (DMSO)-, tetrahydrofuran (THF)-, acetonitrile (ACN)-, and acetone-water (1:1v/v), under heating at 140°C with SnCl<SUB>4</SUB> as the catalyst. The overall rate of the process was the fastest in ACN/H<SUB>2</SUB>O and acetone/H<SUB>2</SUB>O, followed by DMSO/H<SUB>2</SUB>O and THF/H<SUB>2</SUB>O due to the rate-limiting glucose isomerisation. However, the formation of levulinic acid (via rehydration) and humins (via polymerisation) was more significant in ACN/H<SUB>2</SUB>O and acetone/H<SUB>2</SUB>O. The constant HMF maxima (26–27mol%) in ACN/H<SUB>2</SUB>O, acetone/H<SUB>2</SUB>O, and DMSO/H<SUB>2</SUB>O indicated that the rates of desirable reactions (starch hydrolysis, glucose isomerisation, and fructose dehydration) relative to undesirable pathways (HMF rehydration and polymerisation) were comparable among these mediums. They also demonstrated higher selectivity towards HMF production over the side reactions than THF/H<SUB>2</SUB>O. This study differentiated the effects of polar aprotic solvent-water mediums on simultaneous pathways during biomass conversion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bread waste was valorised for the synthesis of HMF, with yields of 26–27mol%. </LI> <LI> Fastest HMF production took place in ACN/H<SUB>2</SUB>O and acetonitrile/H<SUB>2</SUB>O systems. </LI> <LI> Slow glucose isomerization hindered HMF formation in DMSO/H<SUB>2</SUB>O and THF/H<SUB>2</SUB>O. </LI> <LI> Similar HMF selectivity was achieved in ACN/H<SUB>2</SUB>O, acetonitrile/H<SUB>2</SUB>O, and DMSO/H<SUB>2</SUB>O. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Sulfonated biochar as acid catalyst for sugar hydrolysis and dehydration

Xiong, Xinni,Yu, Iris K.M.,Chen, Season S.,Tsang, Daniel C.W.,Cao, Leichang,Song, Hocheol,Kwon, Eilhann E.,Ok, Yong Sik,Zhang, Shicheng,Poon, Chi Sun Elsevier 2018 CATALYSIS TODAY - Vol.314 No.-

<P><B>Abstract</B></P> <P>This study investigated the use of 30 w/v% H<SUB>2</SUB>SO<SUB>4</SUB> sulfonated wood waste-derived biochar as catalysts for production of value-added chemicals from carbohydrates in water as an environmentally benign solvent. Physicochemical characteristics of the sulfonated biochar were revealed by Fourier transform infrared spectroscopy (FTIR), acid-base neutralization titration, gas adsorption analysis, thermogravimetric analysis (TGA), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Using the sulfonated biochar as catalysts, hydrolysis of maltose at 140–160 °C resulted in the maximum glucose yield of 85.4% and selectivity of 88.2%, whereas dehydration of fructose at 160–180 °C produced the maximum HMF yield of 42.3% and selectivity of 60.4%. A higher range of reaction temperature was required for fructose dehydration due to the higher energy barrier compared to maltose hydrolysis. While increasing the temperature accelerated the catalytic reactions, the maximum product selectivity remained unchanged in the sulfonated biochar-catalyzed systems. The products were stable despite the increase in reaction time, because rehydration and adsorption of products was found to be minor although polymerization of intermediates led to unavoidable carbon loss. This study highlights the efficacy of engineered biochars in biorefinery as an emerging application.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biochar catalyst sulfonated by 30% w/v H<SUB>2</SUB>SO<SUB>4</SUB> achieved 42.3% yield and 58.7% selectivity HMF from fructose. </LI> <LI> Maltose hydrolysis to glucose with yield and selectivity of 85.4% and 88.2% was achieved at lower temperatures. </LI> <LI> Higher temperature accelerated the conversion but did not change the maximum yield and selectivity. </LI> <LI> Energy barrier of dehydration is larger than hydrolysis and requires higher temperature or stronger acidity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Production of 5-hydroxymethylfurfural from starch-rich food waste catalyzed by sulfonated biochar

Cao, Leichang,Yu, Iris K.M.,Chen, Season S.,Tsang, Daniel C.W.,Wang, Lei,Xiong, Xinni,Zhang, Shicheng,Ok, Yong Sik,Kwon, Eilhann E.,Song, Hocheol,Poon, Chi Sun Elsevier 2018 Bioresource technology Vol.252 No.-

<P><B>Abstract</B></P> <P>Sulfonated biochar derived from forestry wood waste was employed for the catalytic conversion of starch-rich food waste (e.g., bread) into 5-hydroxymethylfurfural (HMF). Chemical and physical properties of catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and elemental analysis. The conversion of HMF was investigated via controlling the reaction parameters such as catalyst loading, temperature, and reaction time. Under the optimum reaction conditions the HMF yield of 30.4 Cmol% (i.e., 22 wt% of bread waste) was achieved in the mixture of dimethylsulfoxide (DMSO)/deionized-water (DIW) at 180 °C in 20 min. The effectiveness of sulfonated biochar catalyst was positively correlated to the density of strong/weak Brønsted acidity (SO<SUB>3</SUB>H, COOH, and OH groups) and inversely correlated to humins content on the surface. With regeneration process, sulfonated biochar catalyst displayed excellent recyclability for comparable HMF yield from bread waste over five cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> HMF yield of 30.4 Cmol% (∼20 wt%) from bread waste was achieved at 180 °C in 20 min. </LI> <LI> SBC loading, temperature, and reaction time controlled starch conversion route. </LI> <LI> HMF yield was in line with the total acidity density (TAD) of SBC. </LI> <LI> TAD of recovered biochar catalysts was inversely correlated with humins content. </LI> <LI> With regeneration, SBC displayed comparable performance and excellent recyclability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Improving urban public transport service using new timetabling strategies with different vehicle sizes

Avishai Ceder,Stephan Hassold,Christopher Dunlop,Iris Chen 서울시립대학교 도시과학연구원 2013 도시과학국제저널 Vol.17 No.2

This paper deals with the creation of bus timetables using different vehicle sizes. The need for the development of new bus timetables for public transport (PT) stems from the current reliability and efficiency problems that current bus services are facing. These issues arise from the fact that timetables are designed mainly with even headways; however, it is also possible to design timetables with even passenger loads on the vehicles at the maximum load points, but with uneven headways. This paper hopes to bridge the two strategies together through the use of the incorporation of a mixed fleet size, running in conjunction. The timetables were constructed using two key concepts; assigning capacity and shifting departure times. The methodology for the creation of timetables was applied to a real-life example from Auckland, New Zealand. The results of the timetable are promising, validating the methodology of the model. The new timetables lead to a reduction in both passenger waiting time (user perspective) and empty seat time (operator perspective), with only a marginal increase in passenger standee time. The implementation of a mixed fleet of different vehicle sizes shows to be a promising way for achieving both an even headway and an even loading.