Hydrogen production and storage

, par Valérie Meille, Isabelle Pitault, Daniel Schweich, Hector Osuna, Yousef Swesi, Gabriela Santa-Cruz, Jérôme Anfray, Philippe Kerleau, Ann Forret, Lucile Courthial

Several projects are developed withing this theme :

  1. Methane cracking
  2. Hydrogen storage in liquid hydrocarbons
  3. Fischer-Tropsch synthesis

1) Methane cracking

Methane cracking was studied in LGPC as an alternative of steamreforming. The reaction occurs in two steps on a Pt/CeO_2/Al_2O_3 catalyst trapping the carbone in carbonate or formiate :

CH_4 \rightarrow C + 2H_2

C + O_2 \rightarrow CO_2

2) Hydrogen storage in liquid hydrocarbons

Due to its physico-chemical properties, hydrogen is not easily transported, neither under liquid nor gaseous form. However, it can be stored in a safer and more economical way in hydrocarbon molecules. We have chosen to reexaminate the naphthene dehydrogenation as a possible way to obtain hydrogen.

Methylcyclohexane is able to store 6.1wt-% of hydrogen. Its dehydrogenation does not directly produce some CO_2. Whatever the heating method chosen, the CO_2 production of a car wouldn’t go beyond 40g_{CO_2}/km.

The overall process of hydrogen restitution can be divided in two parts :
- dehydrogenation of cycloalcane. The catalytic reaction being highly endothermic, an efficient heating of the catalyst is required. This implies the design of a catalytic heat-exchange-reactor coupling an endothermic and an exothermic reactions.
- a separation and purifying process to produce pure hydrogen, free from toluene vapors (< 1ppm).

3) Fischer-Tropsch synthesis

The project has started in July 2000 and presents a real challenge : how to scale up a bubble column with a slurry catalyst (till 30% solid) to 5m diameter and 20m height ? How do the gas, the liquid and the solid circulate ? These questions have been studied during two PhD thesis :
- A. Forret thesis (june 2003) in collaboration with IFP and Professor Krishna from Amsterdam University ; the experimental work has been carried out at IFP (Solaize) where large pilot units are available (1m diameter column).
- J. Anfray thesis (december 2005) in collaboration with Air Liquide ; a model for Fischer-Tropsch bubble column has been proposed in agreement with lab experiments. During the second year, the collaboration was enlarged to Total group and Lille catalysis lab "UCCS".