1a. Objectives (from AD-416):
Develop novel sorbents, destructive catalysts, and combustion techniques to eliminate the atmospheric input of the most widely used quarantine and pre-shipment (QPS) fumigant, MB.
1b. Approach (from AD-416):
Utilizing a cooperative effort between USDA-ARS, industry, Yale University, Conneticut Agricultural Experiment Station, and U California at Berkeley, research in the context of retaining specialty crops exports that have quarantine and pre-shipment (QPS) fumigation requirements. The team will develop a commercially viable, cost efficient and effective process to contain, destroy, or recapture/reuse methyl bromide and its alternatives following postharvest fumigations.
3. Progress Report:
This Assistance Type Cooperative Agreement was established to support objective 1 of the in-house project and is related to finding postharvest methyl bromide alternatives and techniques for improving methyl bromide fumigations. A Yale University collaborator synthesized and tested catalysts that destroy methyl bromide in a continuous fixed-bed quartz reactor. A constant flow of 64 mg/L methyl bromide, a level that might be encountered at the end of a chamber fumigation event, was conveyed through stainless steel coil tubing to the reactor. The bed depth was ~1.5 mm corresponding to a residence time of the air stream over the catalyst of ~0.014 seconds. The potential for the catalysts to oxidize methyl bromide followed the order CeO2 > CeO2-Al2O3 mixtures > Al2O3 > TiO2. In addition, chloropicrin was used as a surrogate molecule to study the potential for sulfur-containing nucleophiles to destroy methyl bromide. The rate constant for thiosulfate destruction of chloropicrin in aqueous solution was measured and reaction products were characterized. The results indicate that chloropicrin degraded much faster than previously thought, as it was detectable at only trace levels after 2 h.