Synthesis of SAPO-34 on graphite foams for adsorber heat exchangers

Graphite cellular structures have been prepared and used as supports for direct synthesis of SAPO-34 zeolite. The zeolite deposition was obtained by hydrothermal synthesis after a preliminary oxidation of the graphite foams to increase their chemical affinity with the zeolite. The thermal conductivity of graphite foams was evaluated by a “guarded hot plate” method. A comparison with aluminum foams of equivalent porosity showed that graphite foams perform similar or even better. In particular, the thermal conductivity of a graphite foam of 85% porosity was 24 W/m K. After the zeolite deposition process the thermal conductivity of the graphite composites was unchanged. Water adsorption measurements conducted on the coated foams by a McBain test unit confirmed the behavior observed for the pure SAPO-34, showing that interphase interactions between zeolite and support surface had no negative influence on the crystal growth process.