VERTIMASS WHITE PAPERS
Technoeconomic and life-cycle analysis of single-step catalytic conversion of wet ethanol into fungible fuel blendstocks
Abstract
Technoeconomic and life-cycle analyses are presented for catalytic conversion of ethanol to fungible hydrocarbon fuel blendstocks, informed by advances in catalyst and process development. Whereas prior work toward this end focused on 3-step processes featuring dehydration, oligomerization, and hydrogenation, the consolidated alcohol dehydration and oligomerization (CADO) approach described here results in 1-step conversion of wet ethanol vapor (40 wt% in water) to hydrocarbons and water over a metal-modified zeolite catalyst. A development project increased liquid hydrocarbon yields from 36% of theoretical to >80%, reduced catalyst cost by an order of magnitude, scaled up the process by 300-fold, and reduced projected costs of ethanol conversion 12-fold. Current CADO products conform most closely to gasoline blendstocks, but can be blended with jet fuel at low levels today, and could potentially be blended at higher levels in the future. Operating plus annualized capital costs for conversion of wet ethanol to fungible blendstocks are estimated at $2.00/GJ for CADO today and $1.44/GJ in the future, similar to the unit energy cost of producing anhydrous ethanol from wet ethanol ($1.46/GJ). Including the cost of ethanol from either corn or future cellulosic biomass but not production incentives, projected minimum selling prices for fungible blendstocks produced via CADO are competitive with conventional jet fuel when oil is $100 per barrel but not at $60 per barrel. However, with existing production incentives, the projected minimum blendstock selling price is competitive with oil at $60 per barrel. Life-cycle greenhouse gas emission reductions for CADO-derived hydrocarbon blendstocks closely follow those for the ethanol feedstock.
Catalytic Conversion of Biomass-Derived Ethanol to Liquid Hydrocarbon Blendstock Effect of Light Gas Recirculation
Catalytic-Conversion-of-Biomass-Derived-Ethanol-to-Liquid.pdf
Abstract
We describe a light gas recirculation (LGR) method to increase the liquid hydrocarbon yield with a reduced
aromatic content from catalytic conversion of ethanol to hydrocarbons. The previous liquid hydrocarbon yield is ∼40% from
one-pass ethanol conversion over the V-ZSM-5 catalyst at 350 °C and atmospheric pressure, where the remaining ∼60% yield is
light gas hydrocarbons. In comparison, the liquid hydrocarbon yield increases to 80% when a simulated light gas hydrocarbon
stream is co-fed at a rate of 0.053 mol g−1 h−1 with ethanol as a result of the conversion of most of the light olefins. The LGR also
significantly improves the quality of the liquid hydrocarbon blendstock by reducing the aromatic content and overall benzene
concentration. For 0.027 mol g−1 h−1 light gas mixture co-feeding, the average aromatic content in liquid hydrocarbons is 51.5%
compared to 62.5% aromatic content in the ethanol only experiment. The average benzene concentration decreases from 3.75 to
1.5%, which is highly desirable because the United States Environmental Protection Agency (U.S. EPA) limits the benzene
concentration in gasoline to 0.62%. As a result of a low benzene concentration, the blend wall for ethanol-derived liquid
hydrocarbons changes from ∼18 to 43%. The remaining light paraffins and olefins can be further converted to valuable benzene,
toluene, and xylenes (BTX) products (94% BTX in the liquid) over Ga-ZSM-5 at 500 °C. Thus, the LGR is an effective approach
to convert ethanol to liquid hydrocarbons with a higher liquid yield and low aromatic content, especially a low benzene
concentration, which could be blended with gasoline in a much higher ratio than ethanol or ethanol-derived hydrocarbon
blendstock.
Heterobimetallic Zeolite, InV-ZSM-5, Enables Efficient Conversion of Biomass Derived Ethanol to Renewable Hydrocarbons
Abstract
Direct catalytic conversion of ethanol to hydrocarbon blend-stock can increase biofuels use in
current vehicles beyond the ethanol blend-wall of 10–15%. Literature reports describe quantitative
conversion of ethanol over zeolite catalysts but high C 2 hydrocarbon formation renders this approach
unsuitable for commercialization. Furthermore, the prior mechanistic studies suggested that ethanol
conversion involves endothermic dehydration step. Here, we report the complete conversion of
ethanol to hydrocarbons over InV-ZSM-5 without added hydrogen and which produces lower C 2
(<13%) as compared to that over H-ZSM-5. Experiments with C 2H5OD and in situ DRIFT suggest that
most of the products come from the hydrocarbon pool type mechanism and dehydration step is not
necessary. Thus, our method of direct conversion of ethanol offers a pathway to produce suitable
hydrocarbon blend-stock that may be blended at a refinery to produce fuels such as gasoline, diesel,
JP-8, and jet fuel, or produce commodity chemicals such as BTX.
Selective conversion of bio-derived ethanol to renewable BTX over Ga-ZSM-5†
Selective-conversion-of-bio-derived-ethanol-to-renewable-BTX-over-Ga-ZSM-5.pdf
Abstract
Selective conversion of bio-derived ethanol to benzene, toluene and xylenes (BTX) is desirable for producing
renewable BTX. In this work, we show that addition of Ga to H-ZSM-5 leads to a two-fold increase in
the BTX yield as compared with H-ZSM-5 when ethanol is converted over these zeolites at 450 °C and
ambient pressure. Besides promoting BTX formation, Ga also plays an important role in enhancing molecular
hydrogen production and suppressing hydrogen transfer reactions for light alkane formation. The
ion exchange synthesis of Ga-ZSM-5 results in the majority of Ga at the outer surface of zeolite crystals
as extra-zeolitic Ga2O3 particles and only a small fraction of Ga exchanging with the Brønsted acid sites
which appears to be responsible for higher ethanol conversion to BTX. The interface between H-ZSM-5
and Ga2O3 particles is not active since H-ZSM-5 and the physical mixture of β-Ga2O3/H-ZSM-5 furnish
an almost identical product distribution. Hydrogen reduction of the physical mixtures facilitates movement
of Ga to ion exchange locations and dramatically increases the BTX yield becoming comparable to
those obtained over ion-exchanged Ga-ZSM-5, suggesting that exchanged Ga(III) cations are responsible
for the increased BTX production. A linear correlation between the BTX site time yield and exchanged Ga
sites further confirms that Ga occupying cationic sites are active sites for enhancing BTX formation.
Reduction of physical mixtures (β-Ga2O3/H-ZSM-5) also provides an economical and environmentally
friendly non-aqueous method for large scale catalyst synthesis without sacrificing catalyst performance
for ethanol conversion application.