(640f) Co-Feeding Lignin-Derived Compounds and Hydrocarbons On Different Acid Zeolites
Abstract for the AIChE 2011 Annual Meeting
The conversion of pure anisole and guaiacol, a model compound of lignocellulosic biomass-derived oils, and its mixtures with tetralin, propylene, n-decane, or benzene, has been investigated over zeolites (HZSM-5 and HY) in continuous flow and pulse reactors. The dominant reaction of pure anisole and guaiacol is transalkylation, which produces catechols, phenol, cresols, xylenols, and methyl anisoles as main products. From the pulse experiment, it is suggested that coking and adsorption of the products of anisole conversion and guaiacol are more severe on HZSM-5 catalyst, and leads to a stronger catalyst deactivation as compared to HY. While with pure anisole in the feed a fast deactivation is observed, the addition of tetralin, which is an effective hydrogen donor, to the feed results in lower amounts of carbon deposits and much higher catalyst stability. Hydrogen transfer from tetralin helps desorbing and dehydrating phenolic products from anisole conversion. However the role of hydrogen transfer is more effective in HY than HZSM-5. The other hydrocarbons with weaker hydrogen transfer capability have lower effect (e.g. n-decane), negligible effect (e.g. benzene), or even a detrimental effect (e.g. propylene) on activity. Transalkylation reaction was also observed when anisole was co-fed with tetralin. Experiments with subsequent pulses of anisole and tetralin were also carried out to elucidate the transalkylation reaction pathway between anisole and tetralin. Dissociative pathway occurs dominantly over HZSM-5, while both dissociative and non-dissociative bimolecular pathways are possible over HY. The alkylation reaction of m-cresol with propanols and propylene over HBeta were also tested. Propanols were dehydrated fast to propylene and then reacted with m-cresol. Propylene formed oligomers which deactivated the catalyst. Water can reduce the oligomers and might generate new weak Bronsted acid sites thus enhance the activities.