Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

We thank Dr Alan McCue from the Department of Chemistry, University of Aberdeen, for assisting in carrying out the TPO measurements. CRediT authorship contribution statement Marinela D. Zhurka: Investigation, Writing - original draft. Angeliki A. Lemonidou: Resources, Writing - review & editing. Panagiotis N. Kechagiopoulos: Conceptualization, Methodology, Writing - review & editing, Supervision.Peer reviewedPostprin

Kinetic analysis of the steam reforming of ethanol over Ni/SiO2 for the elucidation of metal dominated reaction pathways

Peer reviewedPostprin

Investigation of support effects during ethanol steam reforming over a Ni/Sepiolite catalyst

Peer reviewedPublisher PD

Catalytic Biomass Gasification in Supercritical Water and Product Gas Upgrading

The gasification of biomass with supercritical water, also known as SCWG, is a sustainable method of hydrogen production. The process produces a mixture of hydrogen, carbon oxides, and hydrocarbons. Upgrading this mixture through steam or dry reforming of hydrocarbons to create synthesis gas and then extra hydrogen is a viable way to increase hydrogen production from biomass. This literature review discusses combining these two processes and recent experimental work on catalytic SCWG of biomass and its model compounds and steam/dry reforming of produced hydrocarbons. It focuses on catalysts used in these processes and their key criteria, such as activity, selectivity towards hydrogen and methane, and ability to inhibit carbon formation and deposition. A new criterion is proposed to evaluate catalyst performance in biomass SCWG and the need for further upgrading via reforming, based on the ratio of hydrogen bound in hydrocarbons to total hydrogen produced during SCWG. The review concludes that most catalysts used in biomass SCWG trap a large proportion of hydrogen in hydrocarbons, necessitating further processing of the product stream

Increasing the Dissolution Rate of Polystyrene Waste in Solvent-Based Recycling

Solvent-based recycling of plastic waste is a promising approach for cleaning polymer chains without breaking them. However, the time required to actually dissolve the polymer in a lab environment can take hours. Different factors play a role in polymer dissolution, including temperature, turbulence, and solvent properties. This work provides insights into bottlenecks and opportunities to increase the dissolution rate of polystyrene in solvents. The paper starts with a broad solvent screening in which the dissolution times are compared. Based on the experimental results, a multiple regression model is constructed, which shows that within several solvent properties, the viscosity of the solvent is the major contributor to the dissolution time, followed by the hydrogen, polar, and dispersion bonding (solubility) parameters. These results also indicate that cyclohexene, 2-pentanone, ethylbenzene, and methyl ethyl ketone are solvents that allow fast dissolution. Next, the dissolution kinetics of polystyrene in cyclohexene in a lab-scale reactor and a baffled reactor are investigated. The effects of temperature, particle size, impeller speed, and impeller type were studied. The results show that increased turbulence in a baffled reactor can decrease the dissolution time from 40 to 7 min compared to a lab-scale reactor, indicating the importance of a proper reactor design. The application of a first-order kinetic model confirms that dissolution in a baffled reactor is at least 5-fold faster than that in a lab-scale reactor. Finally, the dissolution kinetics of a real waste sample reveal that, in optimized conditions, full dissolution occurs after 5 min

ETHYLENE PRODUCTION VIA CATALYTIC STEAM CRACKING OF N-HEXANE

IN THIS THESIS IT WAS STUDIED THE PRODUCTION OF ETHYLENE IN THE PRESENCE OF CATALYSTS VIA STEAM CRACKING OF N-HEXANE. VARIOUS TYPES OF CATALYSTS WERE PREPAREDAND TESTED IN AN EXPERIMENTAL PYROLYSIS UNIT. THE CATALYST SAMPLE WITH THE COMPOSITION 12CAO7AL2O3 SHOWED THE HIGHEST SELECTIVITY IN RELATION TO ETHYLENE PRODUCTION. THE EFFECT OF CALCINATION TEMPERATURE IN CATALYST PERFORMANCE WAS ALSOSTUDIED AND IT WAS POINTED OUT THAT TEMPERATURES HIGHER THAN 1100 C ARE ESSENTIAL FOR THE NEGLIGIBLE COKE AND CO, CO2 PRODUCTION. THE EFFECT OF OPERATING VARIABLES WAS STUDIED. IT WAS FOUND THAT THE CATALYTIC ACTION IS DUE TO PEROXIDIC OXYGEN THAT IS PRESENT. IN THE CRYSTAL PHASE OF THE CATALYST. A SIMPLIFIED FIRST ORDER MODEL WAS USED TO DESCRIBE THE OVERALL DECOMPOSITION REACTION OF N-HEXANE. A MECHANISTIC MODEL WAS PROPOSED FOR THE SIMULATION OF N-HEXANE THERMAL ANDCATALYTIC CRACKING. THE REACTION THEME ADOPTED INCLUDES 92 REACTIONS (88 ELEMENTARY AND 4 MOLECULAR). THE MODEL WAS SUCCEEDED IN PREDICTING ALL THE PRODUCT DISTRIBUTION AT VARIOUS OPERATING CONDITIONS.ΣΤΗΝ ΔΙΑΤΡΙΒΗ ΑΥΤΗ ΜΕΛΕΤΗΘΗΚΕ Η ΠΑΡΑΓΩΓΗ ΑΙΘΥΛΕΝΙΟΥ ΜΕ ΠΥΡΟΛΥΣΗ ΕΞΑΝΙΟΥ ΠΑΡΟΥΣΙΑ ΚΑΤΑΛΥΤΩΝ. ΑΡΧΙΚΑ ΠΑΡΑΣΚΕΥΑΣΤΗΚΑΝ ΔΕΙΓΜΑΤΑ ΚΑΤΑΛΥΤΩΝ ΜΕ ΔΙΑΦΟΡΕΤΙΚΗ ΧΗΜΙΚΗ ΣΥΣΤΑΣΗ ΚΑΙ ΔΟΚΙΜΑΣΤΗΚΑΝ ΣΕ ΠΕΙΡΑΜΑΤΙΚΗ ΜΟΝΑΔΑ ΠΥΡΟΛΥΣΗΣ Κ-ΕΞΑΝΙΟΥ. ΒΡΕΘΗΚΕ ΟΤΙ ΟΚΑΤΑΛΥΤΗΣ ΜΕ ΣΥΣΤΑΣΗ 12CAO7AL2O3 ΕΜΦΑΝΙΖΕΙ ΤΙΣ ΥΨΗΛΩΤΕΡΕΣ ΑΠΟΔΟΣΕΙΣ ΣΕ C2H4 ΚΑΙ C3H6 ΧΩΡΙΣ ΥΨΗΛΑ ΠΟΣΟΣΤΑ ΚΩΚ. ΣΤΗ ΣΥΝΕΧΕΙΑ ΕΠΙΚΕΝΤΡΩΘΗΚΕ Η ΕΡΕΥΝΑ ΣΤΗ ΛΕΠΤΟΜΕΡΗ ΜΕΛΕΤΗ ΤΟΥ ΚΑΤΑΛΥΤΗ 12CAO7AL2O3. ΕΙΔΙΚΩΤΕΡΑ ΜΕΛΕΤΗΘΗΚΕ Η ΕΠΙΔΡΑΣΗ ΤΗΣ ΘΕΡΜΟΚΡΑΣΙΑΣ ΠΥΡΩΣΗΣ ΣΤΗΝ ΕΝΕΡΓΟΤΗΤΑ ΚΑΙ ΕΚΛΕΚΤΙΚΟΤΗΤΑ ΤΟΥ ΚΑΤΑΛΥΤΗ ΚΑΘΩΣ ΚΑΙ Η ΕΠΙΔΡΑΣΗ ΤΩΝ ΜΕΤΑΒΛΗΤΩΝ ΛΕΙΤΟΥΡΓΙΑΣ. Η ΔΡΑΣΗ ΤΟΥ ΚΑΤΑΛΥΤΗ ΒΡΕΘΗΚΕ ΟΤΙ ΟΦΕΙΛΕΤΑΙ ΣΤΗΝΥΠΑΡΞΗ ΥΠΕΡΟΞΕΙΔΙΚΟΥ ΟΞΥΓΟΝΟΥ ΣΤΟ ΚΡΥΣΤΑΛΛΙΚΟ ΠΛΕΓΜΑ ΤΟΥ ΚΑΤΑΛΥΤΗ ΠΟΥ ΕΥΝΟΕΙ ΤΙΣ ΑΝΤΙΔΡΑΣΕΙΣ ΕΝΑΡΞΗΣ ΤΗΣ ΔΙΑΣΠΑΣΗΣ ΤΟΥ Κ-ΕΞΑΝΙΟΥ. ΜΕΛΕΤΗΘΗΚΕ ΕΠΙΣΗΣ Η ΣΥΝΟΛΙΚΗ ΚΙΝΗΤΙΚΗ ΤΗΣ ΔΙΑΣΠΑΣΗΣ ΚΑΙ ΒΡΕΘΗΚΕ ΟΤΙ ΑΚΟΛΟΥΘΕΙ ΤΗΝ ΚΙΝΗΤΙΚΗ ΤΩΝ ΑΝΤΙΔΡΑΣΕΩΝ1ΗΣ ΤΑΞΗΣ. ΤΕΛΟΣ ΑΝΑΠΤΥΧΘΗΚΕ ΕΝΑ ΜΗΧΑΝΙΣΤΙΚΟ ΜΟΝΤΕΛΟ ΜΕ 92 ΣΤΟΙΧΕΙΩΔΕΙΣ ΑΝΤΙΔΡΑΣΕΙΣ ΕΛΕΥΘΕΡΩΝ ΡΙΖΩΝ ΓΙΑ ΤΗΝ ΠΡΟΣΟΜΟΙΩΣΗ ΤΗΣ ΑΠΟΔΟΣΗΣ ΟΛΩΝ ΤΩΝ ΠΡΟΙΟΝΤΩΝ ΤΗΣ ΠΥΡΟΛΥΣΗΣ ΤΟΥ Κ- ΕΞΑΝΙΟΥ

Olefins from Biomass Intermediates: A Review

Over the last decade, increasing demand for olefins and their valuable products has prompted research on novel processes and technologies for their selective production. As olefins are predominately dependent on fossil resources, their production is limited by the finite reserves and the associated economic and environmental concerns. The need for alternative routes for olefin production is imperative in order to meet the exceedingly high demand, worldwide. Biomass is considered a promising alternative feedstock that can be converted into the valuable olefins, among other chemicals and fuels. Through processes such as fermentation, gasification, cracking and deoxygenation, biomass derivatives can be effectively converted into C2–C4 olefins. This short review focuses on the conversion of biomass-derived oxygenates into the most valuable olefins, e.g., ethylene, propylene, and butadiene

Catalytic Glycerol Hydrodeoxygenation under Inert Atmosphere: Ethanol as a Hydrogen Donor

Glycerol hydrodeoxygenation to 1,2-propanediol (1,2-PDO) is a reaction of high interest. However, the need for hydrogen supply is a main drawback of the process. According to the concept investigated here, 1,2-propanediol is efficiently formed using bio-glycerol feedstock with H2 formed in situ via ethanol aqueous phase reforming. Ethanol is thought to be a promising H2 source, as it is alcohol that can be used instead of methanol for transesterification of oils and fats. The H2 generated is consumed in the tandem reaction of glycerol hydrodeoxygenation. The reaction cycle proceeds in liquid phase at 220–250 °C and 1.5–3.5 MPa initial N2 pressure for a 2 and 4-h reaction time. Pt-, Ni- and Cu-based catalysts have been synthesized, characterized and evaluated in the reaction. Among the materials tested, Pt/Fe2O3-Al2O3 exhibited the most promising performance in terms of 1,2-propanediol productivity, while reusability tests showed a stable behavior. Structural integrity and no formation of carbonaceous deposits were verified via Temperature Programmed Desorption of hydrogen (TPD-H2) and thermogravimetric analysis of the fresh and used Pt/FeAl catalyst. A study on the effect of various operating conditions (reaction time, temperature and pressure) indicated that in order to maximize 1,2-propanediol productivity and yield, milder reaction conditions should be applied. The highest 1,2-propanediol yield, 53% (1.1 g1,2-PDO gcat−1·h−1), was achieved at a lower reaction temperature of 220 °C