C543etukansi.kesken.fm Page 1 Thursday, September 3, 2015 12:37 PM C 543 OULU 2015 C 543 UNIVERSITY OF OULU P.O. Box 8000 FI-90014 UNIVERSITY OF OULU FINLAND ACTA UNIVERSITATISUNIVERSITATIS OULUENSISOULUENSIS ACTA UNIVERSITATIS OULUENSIS ACTAACTA TECHNICATECHNICACC Kaisa Lamminpää Kaisa Lamminpää Professor Esa Hohtola FORMIC ACID CATALYSED University Lecturer Santeri Palviainen XYLOSE DEHYDRATION Postdoctoral research fellow Sanna Taskila INTO FURFURAL Professor Olli Vuolteenaho University Lecturer Veli-Matti Ulvinen Director Sinikka Eskelinen Professor Jari Juga University Lecturer Anu Soikkeli Professor Olli Vuolteenaho UNIVERSITY OF OULU GRADUATE SCHOOL; UNIVERSITY OF OULU FACULTY OF TECHNOLOGY Publications Editor Kirsti Nurkkala ISBN 978-952-62-0913-5 (Paperback) ISBN 978-952-62-0914-2 (PDF) ISSN 0355-3213 (Print) ISSN 1796-2226 (Online) ACTA UNIVERSITATIS OULUENSIS C Technica 543 KAISA LAMMINPÄÄ FORMIC ACID CATALYSED XYLOSE DEHYDRATION INTO FURFURAL Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence in Kuusamonsali (YB210), Linnanmaa, on 16 October 2015, at 12 noon UNIVERSITY OF OULU, OULU 2015 Copyright © 2015 Acta Univ. Oul. C 543, 2015 Supervised by Professor Juha Tanskanen Doctor Juha Ahola Reviewed by Professor Tapio Salmi Associate Professor Wiebren de Jong Opponent Docent Arto Laari ISBN 978-952-62-0913-5 (Paperback) ISBN 978-952-62-0914-2 (PDF) ISSN 0355-3213 (Printed) ISSN 1796-2226 (Online) Cover Design Raimo Ahonen JUVENES PRINT TAMPERE 2015 Lamminpää, Kaisa, Formic acid catalysed xylose dehydration into furfural University of Oulu Graduate School; University of Oulu, Faculty of Technology Acta Univ. Oul. C 543, 2015 University of Oulu, P.O. Box 8000, FI-90014 University of Oulu, Finland Abstract Lignocellulosic biomass, such as wood or agricultural residues, is a resource widely available for use in chemical production. In a lignocellulosic feedstock biorefinery, the major parts of biomass, cellulose, hemicellulose and lignin, are converted to valuable chemicals, materials and energy. Furfural production is one option for the use of the pentose sugars available in hemicellulose, and the process could be integrated with the pulp or cellulosic ethanol industry. In the past, furfural production catalysed by organic acids has been in industrial use, but no detailed studies about the kinetics exist. However, the use of organic acid would prevent the waste problems linked to the mineral acids widely used in the furfural industry. In this thesis, furfural formation in formic acid media was studied. The major part of this work concerns the kinetics of xylose dehydration into furfural and further furfural degradation. Based on the results of this thesis and a literature review, adequate prediction of furfural yield in the conditions used can be achieved using a simple kinetic model, including three reactions: 1) Xylose dehydration into furfural, 2) Furfural degradation, and 3) Xylose degradation to products other than furfural. Moreover, it was shown that the overall order of the furfural degradation reaction, usually modelled as a first order reaction, changes with acidity (H+-concentration). Suggestions for a possible reaction mechanism have been made based on the results. In the last part of this thesis, furfural formation in the presence of kraft lignin (Indulin AT) was considered. Sulphuric acid was used as a baseline for formic acid. It was shown that the lignin has an acid-neutralising capacity, but the higher pH did not explain all the changes in the xylose conversion and the furfural yield. Thus, it is highly likely the lignin inhibits the formation of furfural. Altogether, the effects were smaller in formic acid than in sulphuric acid. This thesis confirms the fact that formic acid is an effective catalyst for furfural production. The focus of the thesis was on the reaction kinetics, and the results can be used in conceptual process design. Moreover, the results emphasise the importance of including acidity explicitly in the kinetic model and monitoring acidity changes when real process streams are used. Keywords: biorefinery, formic acid, furfural, lignin, reaction kinetics, xylose Lamminpää, Kaisa, Muurahaishappokatalysoitu ksyloosin dehydraatio furfuraaliksi Oulun yliopiston tutkijakoulu; Oulun yliopisto, Teknillinen tiedekunta Acta Univ. Oul. C 543, 2015 Oulun yliopisto, PL 8000, 90014 Oulun yliopisto Tiivistelmä Lignoselluloosaa, kuten puita tai maanviljelyn jäännösmateriaaleja, on laajasti saatavilla kemial- lisen tuotannon raaka-aineeksi. Biojalostamossa lignoselluloosan pääjakeet, selluloosa, hemisel- luloosa ja ligniini, muutetaan arvokkaiksi kemikaaleiksi, materiaaleiksi ja energiaksi. Furfuraalin tuotanto on yksi vaihtoehto hemiselluloosan sisältämien pentoosien hyödyntämiseksi. Furfuraa- liprosessi voidaan yhdistää sellun tai bioetanolin tuotantoon, ja orgaanisia happoja käyttämällä voitaisiin välttää mineraalihappoihin liittyvät jäteongelmat furfuraalin tuotannossa. Tämän väitöskirjan aiheena on muurahaishappokatalysoitu furfuraalin muodostuminen ksy- loosista. Pääpaino on reaktiokinetiikassa, ja työssä on kehitetty kineettinen malli ksyloosin dehydraatiolle furfuraaliksi ja sitä seuraaville furfuraalin sivureaktioille. Tehdyn tutkimuksen ja kirjallisuusselvityksen perusteella yksinkertainen kolmen reaktion malli antaa riittävän tarkan ennustuksen furfuraalisaannoista käytetyissä olosuhteissa. Reaktiot ovat 1) ksyloosin dehydraa- tio sekä 2) furfuraalin ja 3) ksyloosin reaktiot sivutuotteiksi. Lisäksi huomattiin, että reaktion, jossa syntyy furfuraalin häviämistuotteita, reaktioaste on riippuvainen happamuudesta (H+-kon- sentraatio). Työssä onkin ehdotettu mahdollisia reaktiomekanismeja furfuraalin sivureaktioille. Työn viimeisessä osassa tutkittiin ligniinin vaikutusta furfuraalin muodostumiseen. Vertailu- kohtana muurahaishapolle käytettiin rikkihappoa. Tutkimuksessa selvisi, että käytetty ligniini, Indulin AT, huononsi furfuraalisaantoa. Suurin osa vaikutuksesta johtui ligniinin neutralointika- pasiteetista, jolloin reaktioliuoksen happamuus laski, mutta mahdollisia sivureaktioita ei voitu sulkea pois. Kaiken kaikkiaan vaikutukset olivat pienempiä muurahaishapolla kuin rikkihapolla. Tämä väitöskirjatutkimus osoitti, että muurahaishappo katalysoi furfuraalin tuotantoa tehok- kaasti. Tutkimuksessa muodostettiin reaktiokineettinen malli, jota voidaan käyttää käsitteellises- sä prosessisuunnittelussa. Tulosten perusteella on tärkeää huomioida reaktioliuoksen happa- muus kinetiikassa ja tarkkailla happamuuden muutoksia käytettäessä prosessisivuvirtoja. Asiasanat: biojalostamo, furfuraali, ksyloosi, ligniini, muurahaishappo, reaktiokinetiikka Acknowledgements This work has been conducted in the Chemical Process Engineering Research Group in University of Oulu for the duration 2008-2015. The work was part of two Academy of Finland projects PEGRES and PhaseStabEq (Decision No. 118177 and 253871). I am also grateful to the Emil Aaltonen Foundation, Finnish Cultural Foundation and Yliopiston apteekin rahasto for their financial support. I would not have been able to finish this work without help from other people. First of all, I would like to thank my supervisor Prof. Juha Tanskanen for giving me this opportunity and for all his invaluable advices during these years. Besides, I am very grateful to my other supervisor, Dr. Juha Ahola, for all the conversations, Matlab tricks, and guidance. Moreover, I have been lucky to have a fellow-researcher standing by me and sharing all the good and bad moments with experimental devices as well as during courses and seminars. Thanks Laura! My sincere thanks go also to the pre-examiners of my thesis, Prof. Tapio Salmi from Åbo Akademi and Dr. Ir. Wiebren de Jong from TU Delft. Thank you for your encouraging feedback. Sue Pearson and Mike Jones from Pelc Southbank Languages are acknowledged for correcting the English of my work. I am also grateful to Jorma Penttinen, who helped me with the experimental devices, and Ismo Koskenkorva, who performed HPLC analyses, and Esa Dubatscheff, who conducted numerous experiments and pH measurements. I would also like to thank Elisa Wirkkala, who helped in any practical laboratory issue I ever had, Ismo Moisio, Jarmo Murto and Toivo Nissinaho, who helped with experimental device, and Pekka Niemistö, who helped in many practical problems. I am thankful for all my colleagues at former Department of Process and Environmental Engineering and Graduate School of Chemical Engineering for all the seminars, meetings and courses who provided simulating conversations. And the life without coffee room conversations, nights out and every day work life with present and former members of Chemical Process Engineering Research Group would have been so boring. Many thanks for each and every one of you. Finally, my warmest thanks go to my family and friends. Especially many thanks go to Ville for being my other half and keeping the house standing during my long days at the university. And a warm thanks to Ruut and Verna, my smart and lovely daughters. You are my sunshine! Limerick, August 2015 Kaisa Lamminpää 8 List of symbols and abbreviations Greek symbols α star distance at central composite design Χ conversion Latin symbols C concentration [M] E activation energy [kJ mol-1] k rate constant or number of variables in central composite design m order of acid catalysed furfural degradation reaction n order of uncatalysed furfural