Glycerol, a commodity by-product of the biodiesel industry, has value as a fuel feedstock and chemical intermediate. It is also a simple prototype of sugars and carbohydrates. Through catalytic partial oxidation (CPOx), glycerol can be converted into syngas without the addition of process heat. We explored the CPOx of glycerol using a nebulizer to mix droplets with air at room temperature for reactive flash volatilization. Introducing this mixture over a noble-metal catalyst oxidizes the glycerol at temperatures over 600 degrees C in 30-90 ms. Rhodium catalysts produce equilibrium selectivity to syngas, while platinum catalysts produce mainly autothermal non-equilibrium products. The addition of water to the glycerol increases the selectivity to H(2) by the water gas shift reaction and reduces non-equilibrium products. However, water also quenches the reaction, resulting in a maximum in H(2) production at a steam/carbon ratio of 2:3 over a Rh-Ce catalyst. Glycerol without water produces a variety of chemicals over Pt, including methylglyoxal, hydroxyacetone, acetone, acrolein, acetaldehyde, and olefins.

The catalytic conversion of esters and carboxylic acids into synthesis gas or chemicals could permit optimal utilization of organic intermediates such as pyrolysis bio-oils. To examine the ester moiety, two esters, ethyl lactate and ethyl propionate, and two acids, lactic acid and propionic acid, were reformed by catalytic partial oxidation. Autothermal reforming was examined over platinum and rhodium based catalysts supported on alumina foam monoliths at a contact time on the order of 10 ms. Conversions >98% were observed for all four fuels. The addition of cerium or lanthanum was found to increase the selectivity to synthesis gas. At higher fuel to oxygen ratios, nonequilibrium species such as ethylene and acetaldehyde were observed. Ethyl propionate produced twice as much ethylene as ethyl lactate but very little acetaldehyde. The additional hydroxyl group in ethyl lactate produced acetaldehyde such that the ratio of ethylene to acetaldehyde was ∼1:1. The results provide evidence that the homogeneous decomposition of esters to intermediate acids can contribute to the overall reforming process. Products are highly tunable between synthesis gas and olefins by varying the fuel-to-oxygen ratio and the catalyst.

As the lowest cost biomass-derived liquids, pyrolysis oils (also called bio-oils) represent a promising vector for biomass to fuels conversion. However, bio-oils require upgrading to interface with existing infrastructure. A potential pathway for producing fuels from pyrolysis oils proceeds through gasification, the conversion to synthesis gas. In this work, the conversion of bio-oils to syngas via catalytic partial oxidation over Rh-Ce is evaluated using two reactor configurations. In one instance, pyrolysis oils are oxidized in excess steam in a freeboard and passed over the catalyst in a second zone. In the second instance, bio-oils are introduced directly to the catalyst. Coke formation is avoided in both configurations due to rapid oxidation. H 2 and CO can be produced autothermally over Rh-Ce catalysts with millisecond contact times. Co-processing of bio-oil with methane or methanol improved the reactor operation stability.

We performed a long-term study of the autothermal reforming of glycerol. Liquid glycerol and water were introduced into a quartz reactor at room temperature and mixed with air in a nebulizer. The aerosol reacted to form H2, H2O, CO, and CO2 over a bed of spherical Rh−Ce/CeO2/Al2O3 particles, with minor production of C2+ species. Catalyst deactivation was exhibited by a decrease in the production of H2 and CO2 and increases in CO and temperature over 450 h. The product changes suggest reduction in the water−gas shift reaction, which is typically promoted by Ce. SEM analysis indicated sintering of the catalyst due to high reaction temperatures, and EDS showed inorganic deposits on the walls of the quartz reactor and on the catalyst spheres. Etching of the quartz reactor shell was also observed.

Autothermal partial oxidation is a promising technique to upgrade bio-oil into syngas and commodity chemicals. This work aims to clarify preferred chemical routes in an autothermal system by investigating individually two-carbon molecules containing the functional groups found in bio-oil. Acids, alcohols, aldehydes, esters, ethers, and polyols were reacted over PtÀ and RhÀAl 2 O 3 catalysts. Also, to investigate thermal effects independent of O 2 -induced reactions, these molecules were passed over the same catalysts under similar conditions but in the absence of O 2 . Oxygen and adsorption geometry (the latter deduced from surface science literature) appear to play a key role in reaction initiation (manifested via overall conversion) and in the subsequent reaction of intermediate compounds. The catalyst identity also played a significant role in the observed product spectrum, and conversion was higher over the Rh catalyst. Polyols, ethers, and acids were the least reactive, while esters were the most reactive. The Rh catalyst yielded slightly higher selectivity to syngas products, while the Pt catalyst yielded slightly higher selectivity to combustion and intermediate products. Product selectivities and the surface science literature are used to propose reaction pathways.