Thi Minh Chau Hoang

Humin based by-products from biomass processing as a potential carbonaceous source for synthesis gas production

Lignocellulosic biomass is addressed as potential sustainable feedstock for green fuels and chemicals. (Hemi)cellulose is the largest constituent of the material. Conversion of these polysaccharides to bio-based platform chemicals is important in green chemical/fuel production and biorefinery. Hydroxymethyl furfural, furfural and levulinic acid are substantial building blocks from (poly)saccharides. Synthesis of these molecules involves acid catalysed hydrolysis/dehydration reactions which leads large formation of insoluble by-products, called humins. Humin obtained from dehydration of glucose is used in this study. Fractionisation of humin was investigated using various solvents (e.g., acetone, H2O, and NaOH 1%). Characterisation of humin using various techniques including ATR-IR, HR-SEM, solid state NMR, elemental analysis, Raman spectroscopy, pyrolysis, etc. confirms its furan rich structure with aliphatic oxygenate linkages. The influence of thermal treatment on humin was investigated. Humin undergoes a lot of changes both in morphology and structure. Humin loses ca. 45 wt% when preheated to 700 °C (prior to the gasification temperature) and contains above 92 wt% C in mainly aromatic/graphitic structures. Valorisation of humin via dry reforming was studied. Non-catalytic dry reforming of humin is very difficult; however, alkali catalysts (e.g. Na2CO3) can enhance the reaction rate tremendously.

Valorization of Humin‐Based Byproducts from Biomass Processing—A Route to Sustainable Hydrogen

The synthesis of biomass-based top value-added chemical platforms, for example, 5-hydroxymethyl furfural, furfural, or levulinic acid from the acid-catalyzed dehydration of sugars results in high yields of insoluble by-products, referred to as humin. Valorization of humin by steam reforming for H2 is discussed. Both thermal and catalytic steam gasification were investigated systematically. Humin undergoes drastic changes under thermal pre-treatment to the gasification temperature. Alkali-metal-based catalysts were screened for the reactions. Na2 CO3 showed the highest activity and was selected for further study. The presence of Na2 CO3 enhances the gasification rate drastically, and gas-product analysis shows that the selectivity to CO and CO2 is 75% and 25%, respectively, which is a H2 /CO ratio of 2 (corresponding to 81.3% H2 as compared to the thermodynamic equilibrium). A possible process for the complete, efficient conversion of humin is outlined.

Invesitgation of Ce-Zr oxide supported Ni catalysts in steam reforming of meta-cresol as model component for bio-derivated tar

Phenols are major components in the tar vapours formed during gasification of biomass‐based feedstocks. The steam reforming of m‐cresol was demonstrated for tar removal and H2 production in this study. Ceria–zirconia based catalysts containing nickel were developed and investigated by using multiple characterisation techniques such as X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, and temperature‐programmed reduction and oxidation. These catalysts show high activity and excellent stability for producing hydrogen. The influence of the preparation method for the support on the catalyst performance was studied. Ni deposited on a hydrothermally prepared Ce–Zr solid solution was shown to be the most promising catalyst because of its excellent anti‐coking properties resulting from its high oxygen mobility. Insight into the steam‐reforming reactions was gained by inu2005situ FTIR spectroscopy. The IR results reveal different geometries of adsorbed m‐cresol on the different supports. It also indicates that multiple sites (Ni and Ce) on the catalysts are involved in the reactions.