Thermochemical cycles for energy storage: Thermal decomposition of ZnCO sub 4 systems

The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH{sub 4}HSO{sub 4}) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, reported herein, we have shown that when NH{sub 4}HSO{sub 4} is mixed with ZnO and decomposed, the resulting products can be released stepwise (H{sub 2}A{sub (g)} at {approximately}163{degrees}C, NH{sub 3(g)} at 365--418{degrees}C, and a mixture of SO{sub 2(g)} and SO{sub 3(g)} at {approximately}900{degrees}C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO{sub 4}). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V{sub 2}A{sub 5} and possibly other metal oxides

Endothermic photo-catalytic reactions

The overall objective of this report is to present the results of an investigation to provide guidelines for future experimental work, on solar energy driven endothermic photo-catalytic reactions, and primarily to select candidate synthesis reactions which lead to high $-value products. An intensive literature search was conducted to find properties, market demand, and prices of pertinent chemicals; meeting four criteria: (1) the reaction must be endothermic and favorable; (2) the reaction must be catalytic; (3) the product must be produced from low cost feedstocks; and (4) the product must have a sales price >$1.00/lb. Initial examination of low cost feedstocks to high value products lead to consideration of n-paraffins to aromatics and substituted aromatics. Fifteen candidate endothermic synthesis reactions, meeting the above criteria, are suggested. The ratio of product price by reactant cost indicates {approximately}5--8 for the best possibilities; all can be visualized as starting with low cost paraffin and methanol feedstocks