Catalytic conversion of sawdust-based sugars into 5-hydroxymethylfurfural and furfural

Abstract Sawdust is an abundant but poorly utilized lignocellulosic side stream. It is mainly burned as energy despite the fact that it could be utilized in the production of biomass-based chemicals. Sawdust is composed of cellulose, hemicellulose, and lignin fractions, all of which can be separated and utilized for different applications. The production of so-called high-value-added chemicals from biomass could improve the economics associated with biorefinery and replace certain petroleum-based chemicals as well. Recently, the production of 5-hydroxymethylfurfural (HMF) and furfural has attracted a considerable amount of interest, as these substances can be prepared from sawdust-based sugars and play a key role in the production of many biomass-based products. The catalytic conversion of sawdust-based sugars into HMF and furfural was studied in this thesis. The comprehensive utilization of sawdust through stepwise fractionation, hydrolysis, and conversion were used, and all the reaction steps were geared toward high selectivity. In addition, different homogeneous and heterogeneous catalysts, such as mineral acids, organic acids, metal salts, catalysts based on activated carbon (AC), and deep eutectic solvents (DESs), were also utilized in this research. In the first part of the thesis, sawdust was selectively degraded to produce either hemicellulose sugars or furfural using acid hydrolysis or DES treatment. In the second part, sawdust-based sugars were converted into HMF and furfural using different AC-based catalysts or DES media. Based on the results obtained, it was demonstrated that hemicellulose could be efficiently separated as sugars and furfural from the sawdust. These processes could potentially be utilized in biorefinery concepts where the main products are currently obtained from cellulose. In addition, the selectivity of HMF and furfural production from sawdust-based sugars could be significantly improved with the use of AC catalysts in the conversion reaction. Overall, this research enhances the information available on possible side stream valorization (sawdust-, C6-, or C5-rich side streams) and introduces some green alternatives for traditional mineral acid catalysts.Tiivistelmä Sahanpuru on laajasti saatavilla oleva mutta huonosti hyödynnetty lignoselluloosapitoinen sivuvirta. Se poltetaan pääasiassa energiana, vaikka se voitaisiin hyötykäyttää erilaisten biomassaperäisten tuotteiden valmistuksessa. Sahanpuru koostuu selluloosa-, hemiselluloosa- ja ligniinifraktioista, jotka voidaan erottaa toisistaan ja hyötykäyttää erilaisissa sovelluksissa. Niin sanottujen korkean lisäarvon tuotteiden valmistaminen biomassasta voisi sekä lisätä biojalostamoiden taloudellista kannattavuutta että korvata osan öljypohjaisista tuotteista biomassaperäisillä vastineilla. Viime aikoina 5-hydroksimetyylifurfuraalin (HMF) ja furfuraalin tuotanto on herättänyt paljon kiinnostusta, sillä ne voidaan valmistaa sahanpurun sisältämistä sokereista ja niillä on keskeinen rooli monien biomassaan perustuvien tuotteiden valmistuksessa. Tässä työssä tutkittiin sahanpurun sisältämien sokereiden katalyyttistä konversiota HMF:ksi ja furfuraaliksi. Sahanpuru hyödynnettiin kokonaisvaltaisesti vaiheittaisen fraktioinnin, hydrolyysin ja konversion avulla siten, että reaktioiden korkea selektiivisyys säilyi joka vaiheessa. Työssä hyödynnettiin erilaisia homogeenisia sekä heterogeenisiä katalyyttejä, kuten mineraalihappoja, orgaanisia happoja, metallisuoloja, aktiivihiilipohjaisia katalyyttejä ja syväeutektisia liuottimia (DES). Työn ensimmäisessä osassa sahanpurun hemiselluloosafraktio pilkottiin selektiivisesti joko sokereiksi tai furfuraaliksi. Tähän käytettiin happohydrolyysiä tai DES-käsittelyä. Työn toisessa osassa sahanpurun sisältämiä sokereita muunnettiin HMF:ksi ja furfuraaliksi käyttäen erilaisia aktiivihiilikatalyyttejä tai hyödyntäen syväeutektisia liuottimia. Saadut tulokset osoittivat, että hemiselluloosa voidaan erottaa sahanpurusta selektiivisesti sekä sokereina että furfuraalina. Tämä olisi hyödynnettävissä esimerkiksi biojalostamoissa, joissa nykyiset päätuotteet saadaan selluloosasta. Lisäksi tulokset osoittivat että HMF- ja furfuraalituotannon selektiivisyyttä sahanpurupohjaisista sokereista voidaan merkittävästi parantaa käyttämällä aktiivihiilikatalyyttejä konversioreaktiossa. Yleisesti ottaen tutkimus lisäsi tietoa sivuvirtojen (sahanpuru sekä C6- että C5-sokerit) hyödyntämisestä ja esitteli vihreän kemian mukaisia vaihtoehtoja perinteisille mineraalihappokatalyyteille

Hiilinanoputkien ja polymeerien välisten vuorovaikutusten parantaminen

Tässä kirjallisuustutkielmassa on tarkasteltu hiilinanoputkien ja polymeerien välisiä vuorovaikutuksia ja esitetty keinoja vuorovaikutusten parantamiseksi. Vuorovaikutusten tarkastelu on painottunut erilaisiin polymeerikomposiitteihin, joissa hiilinanoputkia on käytetty lujiteaineena. Lisäksi tutkielmassa on käyty läpi perusasioita hiilinanoputkien rakenteesta ja ominaisuuksista sekä yleisistä polymeerikomposiiteista. Hiilinanoputkien ja polymeerien vuorovaikutusten parantaminen on jaettu tutkielmassa ei-kovalenttisiin ja kovalenttisiin menetelmiin. Hiilinanoputket ovat nanorakenteeltaan putkimaisia hiilen allotrooppeja. Ne ovat herättäneet paljon mielenkiintoa pienen kokonsa ja erinomaisten mekaanisten, sähköisten ja optisten omaisuuksiensa vuoksi. Yksi kiinnostavimmista hiilinanoputkien sovelluksista ovat olleet hiilinanoputki/polymeeri-komposiitit, sillä hiilinanoputkien erinomaiset lujuusominaisuudet sekä sähkönjohtavuus tekevät niistä ainutlaatuisen lujitemateriaalin. Ongelmana materiaalien kehityksessä on kuitenkin ollut hiilinanoputkien ja polymeerien vähäiset vuorovaikutukset, jotka ovat heikentäneet merkittävästi materiaalien lujuutta (sekä myös muita ominaisuuksia). Vähäiset vuorovaikutukset johtuvat hiilinanoputkien kemiallisesti hyvin inertistä pinnasta. Parempia vuorovaikutuksia hiilinanoputkien ja komposiittien välille on pyritty saamaan muokkaamalla hiilinanoputkien pintaa. Ei-kovalenttiset funktionalisointimenetelmät perustuvat hiilinanoputken pinnan aromaattiseen rakenteeseen, joka mahdollistaa π-π-vuorovaikutukset. Ei-kovalenttisista menetelmistä tutkielmassa on esitetty polymeerien kietominen hiilinanoputkien pintaan ja pinta-aktiivisten aineiden käyttö. Näillä menetelmillä putkista on saatu paremmin dispergoituvia ja myös niiden vuorovaikutukset ovat lisääntyneet. Kovalenttisesta funktionalisoinnista tutkielmassa on esitetty ”grafting to”- ja ”grafting from”-menetelmät, jotka ovat eniten käytettyjä polymeerien liittämisessä hiilinanoputkiin. Molemmat menetelmät vaativat hiilinanoputken pinnan muokkaamista, jonka jälkeen liitettävä polymeeri voidaan liittää putken pintaan. ”Grafting to”-metelmä perustuu additioreaktioon muokatun hiilinanoputken ja polymeerin välillä. Yleisimmin muodostuva sidos on esterisidos tai amidisidos. ”Grafting to”-menetelmässä polymeeri liitetään radikaalireaktioilla hiilinanoputken pintaan. Ennen tätä pintaan liitetään kuitenkin radikaalireaktion initiaattori. Molemmilla tekniikoilla hiilinanoputkiin on liitetty yleisimpiä polymeerejä, kuten polystyreeniä, nailonia, polyvinyylialkoholia, polyuretaania, polyimidejä ja polymetyylimetakrylaattia. Kirjallisuustutkielman perusteella voidaan todeta hiilinanoputkien pinnan muokkaamisen olevan edellytys paremmille vuorovaikutuksille polymeerien kanssa. Polymeerikomposiiteissa pinnan ei-kovalenttinen muokkaaminen ei monessa tapauksessa luo tarpeeksi voimakkaita vuorovaikutuksia nanoputkien ja polymeerimatriisin välille. Tämän takia enemmän käytetty menetelmä on kovalenttinen funktionalisointi polymeereilla. Kovalenttisen funktionalisoinnin onnistumiseen on havaittu vaikuttavan oleellisesti polymeerimatriisin ja hiilinanoputken pintaan liitettävän polymeerin rakenteiden samankaltaisuus. Toinen tärkeä asia funktionalisoitumisen onnistumisessa on funktionalisointireaktion hyvä tehokkuus. Tämä asettaa haasteen, sillä funktionalisointi täytyy saada tehtyä riittävän tehokkaasti mutta niin, ettei se liikaa riko hiilinanoputkien rakennetta

Production of 5-hydroxymethylfurfural from apple pomace in deep eutectic solvent

Abstract Apple pomace is a waste stream produced by fruit processing industry millions of tons annually. It is rich in carbohydrates making it a potential feedstock for the production of 5-hydroxymethylfurfural (HMF), one of the most valuable platform chemicals. In this work, the conversion of apple pomace carbohydrates to HMF was studied in a choline chloride:glycolic acid (1:3) deep eutectic solvent. To prevent undesired side reactions of HMF methyl isobutyl ketone was added to the reaction system as an extractive phase. The effect of reaction conditions, i.e., the amount of water added to the reaction system, the presence of Lewis acid co-catalyst, as well as the reaction temperature and time, on HMF yield were studied. The highest total HMF yield (44.5%) was achieved at 110 °C in 10 min with 15 wt% H₂O, and 0.01 g CrCl₃ as co-catalyst. Without the co-catalyst, the highest achieved HMF yield was 37.3% (120 °C, 20 min, 15 m% H₂O). The results indicated that apple pomace can be used as the feedstock for HMF production but the reaction procedure, especially the extraction process of HMF from deep eutectic solvent needs to be studied further

Furfural and 5-Hydroxymethylfurfural production from sugar mixture using deep eutectic solvent/MIBK System

Abstract Choline chloride (ChCl) / glycolic acid (GA) deep eutectic solvent (DES) media with high water content but without any additional catalyst are introduced in furfural and 5-hydroxymethylfurfural (HMF) production. The effects of water content, reaction time, and reaction temperature are investigated with two feedstocks: a glucose/xylose mixture and birch sawdust. Based on the results, 10 equivalent quantities of water (32.9 wt.%) were revealed to be beneficial for conversions without rupturing the DES structure. The optimal reaction conditions were 160 °C and 10 minutes for the sugar mixture and 170 °C and 10 minutes for birch sawdust in a microwave reactor. High furfural yields were achieved, namely 62 % from the sugar mixture and 37.5 % from birch sawdust. HMF yields were low, but since the characterization of the solid residue of sawdust, after DES treatment, was revealed to contain only cellulose (49 %) and lignin (52 %), the treatment could be potentially utilized in a biorefinery concept where the main products are obtained from the cellulose fraction. Extraction of products into the organic phase (methyl isobutyl ketone, MIBK) during the reaction enabled the recycling of the DES phase, and yields remained high for three runs of recycling

Current status and challenges for metal-organic-framework-assisted conversion of biomass into value-added chemicals

Abstract Owing to the abundance of availability, low cost, and environmental-friendliness, biomass waste could serve as a prospective renewable source for value-added chemicals. Nevertheless, biomass conversion into chemicals is quite challenging due to the heterogeneous nature of biomass waste. Biomass-derived chemicals are appealing sustainable solutions that can reduce the dependency on existing petroleum-based production. Metal-organic frameworks (MOFs)-based catalysts and their composite materials have attracted considerable amounts of interest in biomass conversion applications recently because of their interesting physical and chemical characteristics. Due to their tunability, the catalytic activity and selectivity of MOF-based catalyst/composite materials can be tailored by functionalizing them with a variety of functional groups to enhance biomass conversion efficiency. This review focuses on the catalytic transformation of lignocellulosic biomass into value-added chemicals by employing MOF-based catalyst/composite materials. The main focus is given to the production of the platform chemicals HMF and Furfural from the corresponding (hemi)cellulosic biomass, due to their versatility as intermediates for the production of various biobased chemicals and fuels. The effects of different experimental parameters on the conversion of biomass by MOF-based catalysts are also included. Finally, current challenges and perspectives of biomass conversion into chemicals by MOF-based catalysts are highlighted

Selective hemicellulose hydrolysis of Scots pine sawdust

Abstract The depletion of fossil resources is driving forward the search for new and alternative renewable feedstocks in the production of renewable chemicals, which could replace the petroleum-based ones. One such feedstock is pine (Pinus sylvestris) sawdust, which is generated enormous amounts in Finnish sawmills yearly. However, prior to the utilization in high-value applications, it needs to be fractionated into its constituents. In this work, the objective was to produce monomeric hemicellulose sugars from pine sawdust without degrading cellulose or lignin simultaneously. The influence of the reaction temperature and time, as well as acid type and concentration, was studied. Based on the results, the temperature was the main distinguishing feature between cellulose and hemicellulose hydrolysis. Promising results were achieved with acid mixtures consisting of 0.5% sulfuric acid and 5.5 or 10% formic acid. At 120 °C with the reaction time of 2 h, the mixtures produced hemicellulose sugars with the yields of 62%. These yields were comparable to the yields achieved in similar conditions with 1.5% sulfuric acid or 40% formic acid. Therefore, by using an acid mixture, the concentration of a single acid could be reduced significantly. The solid fractions remaining after the hydrolysis consisted mainly of cellulose and lignin, which verified the selectivity of the hemicellulose hydrolysis. Also, the fractionation of the remaining solids confirmed that the utilization of all the sawdust components is feasible

Conversion of xylose to furfural over lignin-based activated carbon-supported iron catalysts

Abstract In this study, conversion of xylose to furfural was studied using lignin-based activated carbon-supported iron catalysts. First, three activated carbon supports were prepared from hydrolysis lignin with different activation methods. The supports were modified with different metal precursors and metal concentrations into five iron catalysts. The prepared catalysts were studied in furfural production from xylose using different reaction temperatures and times. The best results were achieved with a 4 wt% iron-containing catalyst, 5Fe-ACs, which produced a 57% furfural yield, 92% xylose conversion and 65% reaction selectivity at 170 °C in 3 h. The amount of Fe in 5Fe-ACs was only 3.6 µmol and using this amount of homogeneous FeCl₃ as a catalyst, reduced the furfural yield, xylose conversion and selectivity. Good catalytic activity of 5Fe-ACs could be associated with iron oxide and hydroxyl groups on the catalyst surface. Based on the recycling experiments, the prepared catalyst needs some improvements to increase its stability but it is a feasible alternative to homogeneous FeCl₃

Catalytic conversion of glucose to 5-hydroxymethylfurfural over biomass-based activated carbon catalyst

Abstract Selective and efficient dehydration of glucose to 5-hydroxymethylfurfural (HMF) has been widely explored research problem recently, especially from the perspective of more sustainable heterogeneous catalysts. In this study, activated carbon was first produced from a lignocellulosic waste material, birch sawdust. Novel heterogeneous catalysts were then prepared from activated carbon by adding Lewis or Brønsted acid sites on the carbon surface. Prepared catalysts were used to convert glucose to HMF in biphasic water:THF system at 160 °C. The highest HMF yield and selectivity, 51% and 78%, respectively, were obtained in 8 h with a catalytic mixture containing both Lewis and Brønsted acid sites. Also, preliminary recycling experiments were performed. Based on this study, biomass-based activated carbon catalysts show promise for the conversion of glucose to HMF

Microwave-assisted conversion of novel biomass materials into levulinic acid

Abstract Levulinic acid is considered one of the most important platform chemicals. It is currently produced mainly from lignocellulosic biomasses. However, there are also other abundant biomass materials, which could be used as raw materials for levulinic acid production. In this work, levulinic acid was produced from two novel biomasses in the presence of Brønsted (H2SO4) and Lewis acid (CrCl3·6H2O or AlCl3·6H2O) catalysts. The studied materials were carbohydrate-rich potato peel waste and sporocarps of the fungus Cortinarius armillatus. Reaction conditions, i.e., time, temperature, H2SO4, and Lewis acid concentrations, were studied by utilizing full 24-factorial experimental designs. Microwave irradiation was used as the heating method. Based on the results, the reaction temperature and the H2SO4 concentration had the greatest impact on the yield of levulinic acid. The highest yield obtained in this study from potato peel waste was 49% with 180 °C for reaction temperature, 15 min for reaction time, and 0.5 and 0.0075 M for the concentrations of H2SO4 and CrCl3, respectively. When Cortinarius armillatus was used as the raw material, the highest yield was 62% with 180 °C for reaction temperature, 40 min for reaction time, and 0.5 and 0.0075 M for the concentrations of H2SO4 and CrCl3, respectively