Reforming Reactions for Hydrogen Production

Methane dry reforming (MDR) becomes increasingly attractive because it allows us to reduce greenhouse gases (both CH4 and CO2) in the atmosphere. 

It is a highly endothermic process and requires severe operational temperatures (800-1000°C) to reach high conversion levels in conventional fixed bed reactors. These severe operating conditions will result in catalyst deactivation by coke deposition due to deep cracking of methane, which is thermodynamically favored at high temperatures. In the MRs, it is possible to achieve either a higher conversion than the traditional process at a fixed temperature, or the same conversion but at lower temperatures. Catalyst deactivation can be suppressed by lowering the temperature, as coke deposition via methane decomposition is thermodynamically limited. 

Methanol is an attractive source of hydrogen due to its high H C ratio, its production from sustainable sources (biomass, sugar beets), and its ease of storage as a liquid at atmospheric pressure. The methanol steam reforming (methanol-SR) process is considered to be a more suitable system for fuel cells because higher methanol conversions can be achieved at a low reaction temperature in the range of 250-350°C, and the products contain lower concentrations of CO. 

Ethanol is particularly appealing, since it is less toxic, easy to handle and distribute, and readily available. Recently, much attention has been paid to ethanol as a CO,-neutral and renewable energy source because it can be produced from biomass. 

Dimethyl ether (DME) is a potential clean fuel and energy source of the next generation since it burns without producing NOx, smoke, or particulates. Steam reforming of DME may be another promising process as the hydrogen source for polymeric membrane fuel cells. 

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The catalytic combustor provides heat for the endothermic reforming reaction and the vaporization of liquid fuel. The endothermic reforming reaction is carried out in a parallel flow-type micro-channel of the reformer unit. It is well known that the methanol steam reforming reaction for hydrogen production over the Cu/ZnO/AbOs catalyst involves the following reactions [10]. Eq. (1) is the algebraic summation of Eqs. (2) and (3). 

Glycerol steam reforming reaction for hydrogen production... 

Table 2.8 Reforming reactions for hydrogen production in porous membrane reactors... 

The demonstration test of the coupling of the steam reforming system to the HTTR will contribute to the technical solution of all other hydrogen production system because basic system arrangement and endothermic chemical reactions for hydrogen production are similar. 

Finally, the reactions for hydrogen production are often quite endothermic (reforming reactions) or exothermic (e.g. CPO). The temperature control is thus quite important because a decrease in temperature on the membrane surface leads to a decrease in hydrogen flux through the membrane while an increase in temperature could result in crack on the membrane surface with a consequent decrease of permselectivity (and thus deteriorating the MR performance). The heat management and temperature control in PBMRs is quite... 

The reaction for hydrogen production via the hydrogen sulfide reforming of methane is as follows [21] ... 

Fuel reforming is popular way for hydrogen production for fuel cell use. Hydrocarbons are used for the fuel resource. Methane (CH4) steam reforming process consists of the following two gas phase reactions with various catalysts. 

Steam reforming of glycerol for hydrogen production involves complex reactions. As a result, several intermediate by-products are formed and end up in the product stream, affecting the final purity of the hydrogen produced. Furthermore, the yield of hydrogen depends on several process variables, such as the system pressure, temperature and water-to-glycerol feed ratio. 

Ethanol is a natural renewable product normally produced from biomass, which is an important factor for near-zero carbon dioxide (C02) emissions. It is accessible, easy to transport, ecofriendly, nontoxic, and it can be transformed by catalytic reactions into hydrogen, which is important for fuel cell fuel processing [151], Section 9.8.10 discusses different processes for hydrogen production by the steam-reforming of ethanol. 

Reforming or gasification produces syngas whose H2/CO ratio depends on the feedstock and process conditions such as feed steam/carbon ratio and reaction temperature and pressure. Water-gas shift reaction can further increase the H2/CO ratio of syngas produced from coal to the desired range for conversion to liquid fuels. This reaction is also an important step for hydrogen production in commercial hydrogen plants, ammonia plants, and methanol plants that use natural gas or coal as feedstock. 

Steam reforming is a process in which either natural gas or naphtha is reacted with steam to produce H2, CH4, CO, and CO2. After the initial formation of CO and H2 from naphtha and steam, the primary reactions are the same as for natural gas feed, i.e., CH4 + H2O CO + 3H2 and CO + H2O CO2 + H2. The latter reaction is the water-gas shift. The conditions used depend on both the feed and the intended primary product, e.g., H2 vs. synthesis gas (a mix of CO and H2) vs. CH4 (from naphtha). For hydrogen production from methane the typical conditions are 800-850°C, l MPa, 5 mol H20/lmol C in the feed. The catalyst used is normally Ni/NiO on a Ca0-Al203... 

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