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The main objective of the present work was the evaluation of commercial ZSM-5 catalysts (diluted with a silica-alumina matrix) in the in situ upgrading of lignocellulosic biomass pyrolysis vapours and the validation of their bench-scale reactor performance in a pilot scale circulating fluidized bed (CFB) pyrolysis reactor. The ZSM-5 based catalysts were tested both fresh and at the equilibrium state, and were further promoted with cobalt (Co, 5% wt%) using conventional wet impregnation techniques. All the tested catalysts had a significant effect on product yields and bio-oil composition, both at bench-scale and pilot scale experiments, producing less bio-oil but of better quality. Incorporation of Co exhibited no additional effect on water or coke production induced by ZSM-5, compared to non-catalytic fast pyrolysis. On the other hand, Co addition significantly increased the formation of CO 2 compared to the CO increase which was favored by the use of ZSM-5 alone. These changes in CO 2 /CO yields are indicative of the different decarbonylation/decarboxylation mechanism that applies for Co 3 O 4 compared to ZSM-5 zeolite, due to the differences in their acidic properties (mainly type of acid sites). Co-promoted ZSM-5 catalysts simultaneously enhanced the production of aromatics and phenols with a more pronounced performance in the pilot-scale experiments resulting in the formation of a three phase bio-oil, rather than the usual two phase catalytic pyrolysis oil (aqueous and organic phases). The third phase produced is even lighter than the aqueous phase and consists mainly of aromatic hydrocarbons and phenolic compounds. Addition of Co in ZSM-5 is thus suggested to strongly enhance aromatization reactions that result in selectivity increase towards aromatics in the bio-oil produced. Possible routes of catalyst deactivation in the pilot plant's continuous operation process have been suggested and are related to pore blocking and masking of acid sites by formed coke (reversible deactivation), partial framework dealumination of the fresh zeolitic catalyst, and accumulative ash deposition on the catalyst that depends on the nature of biomass (content of ash). † Electronic supplementary information (ESI) available. See

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Bio-oil (pyrolysis oil) is the liquid product of biomass thermochemical conversion. It is a dark, viscous liquid that contains the depolymerization products of hemicellulose, cellulose, and lignin. The physicochemical properties of bio-oils are determined by employing the conventional methods for fuels analysis with proper adaptations. However, the detailed composition of bio-oils in terms of analytes as well as their concentration remains ambiguous and is a challenging task for analytical chemistry. The compounds in the bio-oil range from nonpolar (e.g., hydrocarbons) to highly polar (e.g., phenolics) and from volatile (e.g., organic acids) to nonvolatile (e.g., sugar derivatives), covering a molecular weight (MW) range of about 50-2000 Da. Hence a combination of analytical techniques such as high pressure liquid chromatography, gas chromatography (GC), gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), and Fourier transform infrared spectroscopy (FTIR) are required to determine the bio-oil's composition. Despite the significant breakthroughs of these techniques, they face limitations regarding the sample pretreatment, the incomplete separation and determination of components, and the need of multiple analyses with each method for more complete results. The development of sophisticated, comprehensive, and hyphenated chromatographic and spectrometric techniques such as GC × GC, LC × LC, high-resolution mass spectrometry (HRMS), and 2D-NMR has brought actual advancement in the field of bio-oil analysis. GC × GC and LC × LC have allowed the development of qualitative and quantitative methods for the individual determination of lower MW compounds. However, HRMS and 2D-NMR have facilitated the elucidation of the structure of the higher MW components, offering insight in the effect of pyrolysis conditions on biomass depolymerization and the possibilities for further upgrading of bio-oils.

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Fructose is one of the most important aldoses and has been gaining attention as the starting material for the synthesis of biobased platform and high-added value chemicals such as 5-hydroxymethylfurfural (5-HMF), levulinic acid and lactic acid. However, due to its low natural occurrence, fructose is produced from glucose, an abundant hexose, via isomerization. Currently, the conventional industrial process utilizes glucose isomerase as a catalyst and is therefore subjected to the limitations of enzymatic reactions. Consequently, an alternative efficient solid catalyst is required that will exhibit high activity, selectivity and stability/reusability. Toward this end, we have demonstrated the effectiveness of using natural MgO, derived from simple calcination of magnesite ores, as a low cost catalyst with increased basicity. A series of industrial and laboratory prepared natural MgO materials with different morphology, porosity and basicity were investigated and the optimum catalyst afforded 44.1 wt % glucose conversion and 75.8 wt % fructose selectivity (33.4 wt % fructose yield), at 90 °C for a 45 min reaction in aqueous solution. The activity of the MgO catalysts was directly correlated with their basicity, which in turn depended on their crystal size, surface area and composition. CaO impurities of the natural MgO materials generated strong basic sites that enhanced glucose conversion but at the expense of fructose selectivity. The stability and reuse of the optimum catalyst was confirmed for at least 4 cycles of reaction–regeneration, whereas the mechanism of glucose isomerization was validated via a first-order kinetic modeling set.