Simultaneous recovery of carbon and sulfur resources from reduction of CO_2 with H_2S using catalysts

An approach to the simultaneous reclamation of carbon and sulfur resources from CO2 and H2S has been proposed and effectively implemented with the aid of catalysts. A brief thermodynamic study reveals the potential of direct reduction of CO2 with H2S（15：15 mol% balanced with N2） for selective production of CO and elemental sulfur. The experiments carried out in a fixed-bed flow reactor over the temperature range of 400–800 °C give evidence of the importance of the employment of catalysts. Both the conversions of the reactants and the selectivities of the target products can be substantially promoted over most catalysts studied. Nevertheless, little difference appears among their catalytic performance. The results also prove that the presence of CO2 can remarkably enhance H2S conversion and the sulfur yield in comparison with H2S direct decomposition. A longtime reaction test on Mg O catalyst manifests its superior durability at high temperature（700 °C） and huge gas hourly space velocity（100,000 h-1）. Free radicals initiated by catalysts are supposed to dominate the reactions between CO2 and H2S.

Recovery of rare earths from spent FCC catalysts by solvent extraction using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester(EHEHPA)

A process to recover rare earth（RE） metals from spent fluid catalytic cracking（FCC） catalysts by solvent extraction was studied, using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester（EHEHPA or P507）. The recovery process involved three steps：（1） leaching REs（mainly lanthanum and cerium）;（2） solvent extraction by applying saponified P507-kerosene system;（3） stripping. Experiments to assure optimal operating conditions were conducted. Results indicated that RE metals could be recovered effectively from spent catalyst with saponified P507-kerosene-HCl system. At room temperature of 25 oC, 10 g spent catalyst with 110 m L of HCl（1 mol/L） could achieve a leaching efficiency of 85%. For extraction, initial pH value of 3.17, organic/aqueous ratio（O/A ratio） of 2：1 with an extractants＇ saponification rate of 20% could obtain 100% efficiency. In the stripping process, 1 mol/L HCl with O/A ratio of 1：1 led to a stripping efficiency of 96%. In the present study, RE metals from spent FCC catalysts were effectively recovered, which avoided wasting a large amount of RE resources. It provides a theoretical support for commercial recycling of RE resources.