Aromatic Production from Catalytic Fast Pyrolysis of Biomass-Derived Feedstocks

Abstract

The conversion of biomass compounds to aromatics by thermal decomposition in the presence of catalysts was investigated using a pyroprobe analytical pyrolyzer. The first step in this process is the thermal decomposition of the biomass to smaller oxygenates that then enter the catalysts pores where they are converted to CO, CO 2 , water, coke and volatile aromatics. The desired reaction is the conversion of biomass into aromatics, CO 2 and water with the undesired products being coke and water. Both the reaction conditions and catalyst properties are critical in maximizing the desired product selectivity. High heating rates and high catalyst to feed ratio favor aromatic production over coke formation. Aromatics with carbon yields in excess of 30 molar carbon% were obtained from glucose, xylitol, cellobiose, and cellulose with ZSM-5 (Si/Al = 60) at the optimal reactor conditions. The aromatic yield for all the products was similar suggesting that all of these biomass-derived oxygenates go through a common intermediate. At lower catalyst to feed ratios volatile oxygenates are formed including furan type compounds, acetic acid and hydroxyacetaldehyde. The product selectivity is dependent on both the size of the catalyst pores and the nature of the active sites. Five catalysts were tested including ZSM-5, silicalite, beta, Y-zeolite and silica-alumina. ZSM-5 had the highest aromatic yields (30% carbon yield) and the least amount of coke.

Catalytic Cracking of Pyrolysis Oil Derived from Rubberwood to Produce Green Gasoline Components

“…The formation of aromatic hydrocarbons in OLP supported the hypothesis that the oxygenated compounds, particularly substituted phenols, in the pyrolysis oil can be converted into aromatic hydrocarbons by dehydroxylation, decarbonylation, and decarboxylation with the HSZM-5 catalyst (Carlson et al 2009;Zhao et al 2010;Cheng and Huber 2011). In addition, as the pyrolysis oil contained some acids, alcohols, aldehydes, ketones and esters, it was suggested that during the conversion of these compounds, olefins were formed as intermediate products, and they underwent a variety of further reactions to yield aromatic hydrocarbons (Adjaye and Bakhshi 1995a).…”

Relationships between Biomass Composition and Liquid Products Formed via Pyrolysis

“…However, this process converts any C1-C5 oxygenates, representing as much as half of the carbon in bio-oil, to C1-C5 hydrocarbons that are too volatile for liquid fuels (Resasco, 2011). Another straightforward approach is to "crack" the pyrolysis vapors using acidic zeolite catalysts into light olefins and aromatic hydrocarbons (primarily benzene, toluene, and o/m/p-xylene) (Bridgwater, 1994;Carlson et al, 2008Carlson et al, , 2009). This approach is appealing because of the lack of an external H2 requirement and the simplicity of the product streams.…”

Catalytic Pyrolysis of Wild Reed over a Zeolite-Based Waste Catalyst

“…Pyrolysis with the biomass-to-catalyst ratio of 1:1 ( Figure 6) promoted the production of low-molecular-mass phenolics to a large extent, while high-molecular-mass phenolics were increased or decreased depending on the species. This result is attributed to promoted decomposition of lignin to phenolics and of high-molecular-mass phenolics to low-molecular-mass phenolics or aromatics owing to deoxygenation (dehydration, decarbonylation, and decarboxylation) and cracking occurring on the acid sites of the catalysts [7,18]. When the catalyst dosage was increased further (Figure 7), the conversion of high-molecular-mass phenolics to low-molecular-mass phenolics was more evident.…”