Aqueous phase reforming

Good reviews dealing with different aspects of this process can be found in the literature [80, 81]. 

Notably, once the oxygenated hydrocarbons have been converted into synthesis gas, it is then possible to carry out the subsequent conversion of synthesis gas into a variety of liquid products by well-established catalytic processes, such as the production of long-chain alkanes by Fischer-Tropsch synthesis and/or the production of methanol. 

The leaching of catalyst components into the aqueous phase during the reaction represents a possible disadvantage of the process. Therefore, the choice of catalyst support materials has to be limited to those that exhibit long-term hydrothermal stability (e.g. carbon, titania, zirconia). 

It is also interesting that if the goal is to produce H2-CO gas mixtures, for instance in the Fischer-Tropsch synthesis, one needs to suppress the WGSR operating in the vapor phase or to operate at higher concentrations of the oxygenated reactant in water or to use a catalyst on which the rate of the WGSR is slow. 

---

Shabaker, J. W. Davda, R. R. Huber, G. W. Cortright, R. D. Dumesic, J. A., Aqueous-phase reforming of methanol and ethylene glycol over alumina-supported platinum catalysts. Journal of Catalysis 2003, 215, 344. 

Dumesic has reviewed the aqueous-phase reforming of polyols to H2 and CO2 under milder conditions, i.e., 200-250 °C [43], He also showed the possibility to divert the reaction towards to production of alkanes by using an acidic support for the Pt or Pd reforming catalyst. 

The catalytic aqueous phase reforming might prove useful for the generation of hydrogen-rich gas from carbohydrates extracted from renewable biomass and biomass waste streams. The biomass-derived hydrocarbons are suitable to hydrogen generation from biomass, as well as for the reforming. 

Four hydrogen production techniques are reviewed hydrocarbon reforming ammonia cracking and two other, less common, production techniques, pyrolysis and aqueous phase reforming. 

An alternative approach for the utilization of biomass resources for energy applications is the production of dean-buming liquid fuels. In this respect, current technologies to produce liquid fuels from biomass are typically multi-step and energy-intensive processes. Aqueous phase reforming of sorbitol can be tailored to produce selectively a clean stream of heavier alkanes consisting primarily of butane, pentane and hexane. The conversion of sorbitol to alkanes plus CO2 and water is an exothermic process that retains approximately 95% of the heating value and only 30% of the mass of the biomass-derived reactant [278]. 

Aqueous phase reforming of EG takes place according to the following reaction H0CH2CH20H + 2H20 5H2 + 2C02 (6.35)... 

The addition of Sn to Raney Ni catalysts also improves the stability and corrosion resistance of the catalyst under aqueous phase reforming conditions. 

Aqueous phase reforming of glycerol in several studies by Dumesic and co-workers has been reported [270, 275, 277, 282, 289, 292, 294, 319]. The first catalysts that they reported were platinum-based materials which operate at relatively moderate temperatures (220-280 °C) and pressures that prevent steam formation. Catalyst performances are stable for a long period. The gas stream contains low levels of CO, while the major reaction intermediates detected in the liquid phase include ethanol, 1,2-pro-panediol, methanol, 1-propanol, propionic acid, acetone, propionaldehyde and lactic acid. Novel tin-promoted Raney nickel catalysts were subsequently developed. The catalytic performance of these non-precious metal catalysts is comparable to that of more costly platinum-based systems for the production of hydrogen from glycerol. 

Catalytic dihydrogen production form biomass is known as aqueous phase reforming (APR) [38]. It is interesting to note the absence of CO in the dihydrogen produced by the biosystem, which makes it immediately suitable for use in fuel-cells... 

A possibly more sophisticated method for utilizing biomass to produce synthesis gas is by aqueous phase reforming (APR), a processing method that was developed for carbohydrates and other more readily accessible biomass oxygenates by Dumesic et Valenzuela et al. however,... 

APR [Aqueous-Phase Reforming] A process for making hydrogen or lower alkanes from carbohydrates, biomass, or glycerol from biodiesel production. The catalyzed process operates at a relatively low temperature (180 to 260°C). Developed from 2001 at the University of Wisconsin and later by Virent Energy Systems, which operated a demonstration plant from 2006. 

Recently, extensive efforts have been made to synthesize liquid hydrocarbons from biomass feedstocks. In 2004, Dumesic and co-workers reported that a clean stream of alkanes could be produced by aqueous phase reforming of sorbitol over a bifunctional catalyst. The sugar is repeatedly dehydrated using a solid acid catalyst and then hydrogenated using a precious metal catalyst such... 

---