Hydrogen production/purification

Defining hydrogen fuel quality specifications is a high priority for the Roadmap. Such specifications must be quantified at the vehicle-station interface and must consider how the presence of small amounts of contaminants affects the performance and durability of fuel cell and balance of plant material compatibility of onboard and stationary hydrogen storage systems and the operation and maintenance of hydrogen production, purification, and delivery systems. Most importantly, fuel quality specification must consider... 

Integrated hydrogen production, purification and compression system, http // www.hydrogen.energy.gov/pdfs/progress08/ ii a 7 tamhankar.pdf... 

Another notable element of the cost increases is the inclusion in the Shaw flow sheets of subsystems for hydrogen product purification and for feed water purification. For S-I and to a lesser extent for HyS, concern with the carry-over of sulphur to the product necessitated a significantly costly purification subsystem on the product end of the cycle. For HTSE, the issue is uncertainty in the purity of input steam and effects on the electrolysis cells, and so a large feedwater purification subsystem impacts the overall capital cost. In the earlier evaluations these subsystems were not considered significant enough to include. 

An acrylonitrile plant eliminated 500,000 pounds of in-process storage of hydrogen cyanide by accepting a shutdown of the entire unit when the product purification area shut down. This forced the plant staff to solve the problems which caused the purification area shutdowns. 

Rhodium catalyzed carbonylations of olefins and methanol can be operated in the absence of an alkyl iodide or hydrogen iodide if the carbonylation is operated in the presence of iodide-based ionic liquids. In this chapter, we will describe the historical development of these non-alkyl halide containing processes beginning with the carbonylation of ethylene to propionic acid in which the omission of alkyl hahde led to an improvement in the selectivity. We will further describe extension of the nonalkyl halide based carbonylation to the carbonylation of MeOH (producing acetic acid) in both a batch and continuous mode of operation. In the continuous mode, the best ionic liquids for carbonylation of MeOH were based on pyridinium and polyalkylated pyridinium iodide derivatives. Removing the highly toxic alkyl halide represents safer, potentially lower cost, process with less complex product purification. 

Existence of water, especially when it concerns large hydrogen production stations, is another factor that affects the construction of an electrolysis unit. However, water consumption (0.9 L/Nm 1 2 3 4 H2) for electrolysis is relatively low compared to other matters in an electrolysis station. Its transport is easy and it may be more convenient to acquire the water ready for electrolysis than to construct a secondary unit for water purification inside the plant. 

Although considerable research has been conducted with Pd-alloy foils, tubes, and thinner composite membranes, long-term durability and stability need to be further demonstrated, especially in the fuel reforming or WGS operating conditions, for acceptance of this technology in a commercial sector. Furthermore, mass-scale and cost-effective production of industrial-scale Pd-alloy thin-film composite membranes need to be demonstrated to be competitive in the hydrogen production and purification market. 

In the 1990s and beyond 2000, there has been an explosion of interest in metal/ partially reducible oxide catalysts for low temperature water-gas shift, mainly directed at the production/purification of hydrogen in a fuel processor for fuel cell applications. 

Hydrogen production from carbonaceous feedstocks requires multiple catalytic reaction steps For the production of high-purity hydrogen, the reforming of fuels is followed by two water-gas shift reaction steps, a final carbon monoxide purification and carbon dioxide removal. Steam reforming, partial oxidation and autothermal reforming of methane are well-developed processes for the production of hydro-... 

---