Optimizing the Aromatic Product Distribution from Catalytic Fast Pyrolysis of Biomass Using Hydrothermally Synthesized Ga-MFI Zeolites

Abstract

A series of gallium-containing MFI (Ga-MFI) zeolites with varying Ga2O3/Al2O3 ratios were synthesized using hydrothermal synthesis and tested as catalyst in catalytic fast pyrolysis (CFP) of beech wood for aromatic production. The results show that the incorporation of Ga slightly reduced the effective pore size of Ga-MFI zeolites compared to conventional HZSM-5 zeolites. Therefore, the Ga-MFI zeolites increased the aromatic selectivity for smaller aromatics such as benzene, toluene, and p-xylene and decreased the aromatic selectivity for bulkier ones such as m-xylene, o-xylene, and polyaromatics in CFP of beech wood relative to HSZM-5. In particular, the yield and selectivity of p-xylene, the most desired product from CFP of biomass, increased considerably from 1.64 C% and 33.3% for conventional HZSM-5 to 2.98–3.34 C% and 72.1–79.6% for the synthesized Ga-MFI zeolites. These results suggest that slightly reducing the pore size of MFI zeolite by Ga incorporation has a beneficial effect on optimizing the aromatic selectivity toward more valuable monoaromatic products, especially p-xylene, during CFP of biomass.

Regeneration of pristine HZSM-5 extrudates during the production of deeply deoxygenated bio-oil fromex situcatalytic fast pyrolysis of biomass in a bench-scale fluidised-bed reactor

“…63 Based on procedure A of ASTM D5758-01, the estimates of the relative crystallinity of the regenerated catalysts were obtained from the intensity of the peaks of 2θ = 22.5-25.0°i n comparison with that of the reference fresh (Re0) catalyst. The integrated peak area encompassing five strong peaks was calculated for relative crystallinity by applying the following equation: %XRD relative crystallinity = (S x /S r ) × 100 (4) where S x is the integrated peak area for the regenerated HZSM-5 catalysts (Re5 and Re9) and S r is the integrated peak area for the reference fresh HZSM-5 (Re0) catalyst. After baseline subtraction, this method suggests that the relative crystallinity was reduced to 86.6% after regenerating for 5 cycles and further to 64.0% after 9 reaction/regeneration cycles.…”

“…The majority of the work has been performed on microreactors, known as pyrolysis-GC/MS systems, where a very small amount of biomass (milli-or micrograms) was pyrolysed in the presence of catalysts and the evolved products are analysed using GC/MS. [1][2][3][4][5][6] This technique is very useful for catalyst screening or comparison with different process parameters, but it may not be representative of a fullscale production as no real bio-oil or liquid is produced. A comprehensive review on catalytic pyrolysis of biomass by Yildiz et al 2016 (ref.…”

“…The efficiency and effectiveness of ZSM-5 catalyst regeneration, which is sometimes called catalyst stability study, is monitored through the changes of pyrolysis product yields and quality, especially oxygen content and hydrocarbon yields, in comparison with the fresh catalyst, and the extent to which the catalyst regains its initial catalyst properties including specific surface area, porosity and acidity (strength and number of acid sites). This has been investigated in a variety of scales including micro-scale using pyrolysis-GC/MS systems, 4,[9][10][11] a few grams scale using fixed-bed reactors 1,12,13 and bench or lab scale using continuous biomass feeding systems such as bubbling or circulating fluidised-bed reactors, 8,14-22 conical spouted-bed reactors, 23 a mechanically agitated bed reactor, 24,25 an ablative reactor 26,27 and fixed-bed reactors, [28][29][30][31] where real liquid bio-oil could be produced and analysed. Some important previous studies related to the regeneration of ZSM-5-based catalysts applying other types of raw materials rather than biomass or its pyrolysis vapour include crude glycerol, 32 carinata oil, 33 black liquor, 6 kraft lignin, 30 oil sludge, 34 plastic mixtures, 35 waste tire 36 and model compounds such as furan 37 and ethylene.…”

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites

“…Several zeolites (Y, β , ZSM-5, SAPO-34, MCM-22, ITQ-2, etc.) were applied for CFP and the best performance was demonstrated by ZSM-5 with high yield of aromatics rather than aliphatic hydrocarbon and significant percentages of deoxygenation ( Zheng et al, 2017 ; Naqvi and Naqvi, 2018 ; Li J. et al, 2019 ; Cai et al, 2020 ). CFP on ZSM-5 is currently the most studied and is already employed in refineries ( Jae et al, 2011 ; Taarning et al, 2011 ; Kubička et al, 2013 ).…”

Selective Mesitylene Oxidative Coupling Reaction by Metastructured Electrocatalyst Comprised of Carbonaceous Scaffold Coated with Pd Derived from Zeolitic Imidazole Framework

“…We have designed electrocatalysts (via pore size modulation) to selectively promote bimesityl from mesitylene due to size selectivity. The molecular sizes [59] (shortest dimension X longest dimension) of mesitylene, bimesityl and termesityl molecules are ̴ 7.8 Å X 8.7 Å, ̴ 8.7 Å X 14.4 Å and ̴ 9.7 Å X 18.8 Å as measured with the help of ImageJ and Chem-Draw11 softwares (Fig. S4), taking kinetic diameter (d) of mesitylene (8.7 Å) as reference [60].…”