Co-processing of wood and wheat straw derived pyrolysis oils with FCC feed—Product distribution and effect of deoxygenation

Abstract

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Performance of mesoporous HZSM-5 and Silicalite-1 coated mesoporous HZSM-5 catalysts for deoxygenation of straw fast pyrolysis vapors

“…Ultimate and proximate characterization for wheat straw particles of the size <1.4 mm was reported earlier [15]. In this study, a sieve fraction of 106-250 m was used and re-analyzed.…”

“…Unfortunately, catalyst deactivation at increasing B:C ratios was not investigated and the tests were performed with direct contact between the catalyst and biomass (in-situ), which can lead to poisoning of acid sites by the biomass indigenous ash [46]. Transfer of alkali metals to the catalyst can be avoided by placing the catalyst downstream of the pyrolysis section [15,16] (ex-situ), which allows for vapor-phase upgrading of agriculture residues like wheat straw with higher ash content and lower cost compared to woody biomass. To the best of our knowledge, the performance of silicalite-1 coated mesoporous HZSM-5 in ex-situ CFP has not yet been reported.…”

“…Those parameters were introduced for assessment of the quality of the never condensed vapors. The acidity of the vapors was defined as (mass of acids in vapors)/(mass of vapors) and is expected to correlate with the total acid number of the condensed vapors [16,17]. The oxygen content of the vapors-defined as (mass of oxygen in vapors)/(mass of vapors) -gives an indication on the effectiveness of deoxygenation and serves as an indicator for the chemical stability of bio-oils.…”

“…The pyrolysis oil contains hundreds of different oxygenated species, which-unfortunately-render the oil acidic and unstable. Catalytic deoxygenation of the biomass pyrolysis vapors prior to condensation reduces the acidity of the oil and improves its chemical stability, heating value, and miscibility with petroleum derived streams [13][14][15][16][17]. However, these improvements come at the expense of carbon loss as light hydrocarbons, CO, CO2, and coke [18,19].…”

“…HZSM-5 zeolite is considered among the most suitable solid acid catalysts for the production of aromatics and gasoline range products from biomass derived pyrolysis vapors since the shape selective micropores (~5.5 Å) improve the selectivity to aromatics and limit coke formation [20,21]. Nevertheless, rapid deactivation by coking occurs [15,22].…”