Showing papers in "Journal of Chemical Engineering of Japan in 2019"

Selective Recovery of Platinum Group Metals from Spent Automotive Catalysts by Leaching and Solvent Extraction

Abstract: Platinum group metals (PGMs) play an important role in the automotive industry as key components of exhaust catalysts. Recycling of PGMs from secondary resources, such as waste products, is encouraged to ensure their sustainability. A highly e cient and environmentally benign technique for the separation of PGMs is currently required. In the present study, the recovery of PGMs from a spent automotive catalyst was investigated using the trioctyldodecyl phosphonium chloride (P8,8,8,12Cl) ionic liquid (IL) as the PGM extraction solvent. First, leaching from the catalyst was investigated. Pt and Pd are selectively extracted into undiluted P8,8,8,12Cl from the 5 mol L−1 HCl leachate containing various metals together with Pt, Pd, and Rh. Subsequently, Rh is extracted into fresh P8,8,8,12Cl from the ra nate adjusted to an appropriate HCl concentration. Mutual separation of Pt and Pd is possible by stripping processes. Some common metals coextracted with PGMs, such as Fe, Cu, and Zn, are removed by each stripping process. Recovery of high purity Pt, Pd, and Rh is achieved by the proposed recycling process. The results demonstrate that separation using phosphonium-based ILs is useful for recycling PGMs.

Recovery of Phosphate Rock Equivalents from Incineration Ash of Chicken Manure by Elution-Precipitation Treatment

Abstract: In order to obtain calcium phosphates - a phosphate rock equivalent - from the incineration ash of chicken manure, which is obtained from power generation systems that use the manure for fuel, incineration ash was treated with an aqueous solution of nitric acid to elute phosphorus. By using 0.3 M of HNO3, most of the phosphorus could be eluted from 1.0 g of ash within 0.1 h. Compared with the composted chicken manure that was previously examined in our laboratory, the concentration of HNO3 was increased for this session of elution. Using the incineration ash of chicken manure made it possible to remove inorganic species at a lower boiling or sublimation temperature, and organic species by calcination in the power generation system. Compared with composted chicken manure, the concentrations of phosphorus contained in the incineration ash and the nitric acid extract were higher in the incineration ash. XRD analysis showed that the obtained nitric acid extract could be treated with aqueous NH3 to form a precipitation of poorly-crystallized calcium hydroxyapatite (Ca10(PO4)6(OH)2), which is one of main components in phosphate rock. In order to confirm the formation and purity of calcium phosphate species, the precipitation calcination was conducted at 1,078 K for 5 h. XRD revealed that the calcined solid was tricalcium phosphate, and no contamination was evident. These results reveal that a phosphate rock equivalent could be easily obtained from the incineration ash of chicken manure, which means that approximately 14% of the phosphate rock that is currently being imported into Japan could be replaced by this product.

Absorption of Carbon Dioxide at High Temperature with Molten Alkali Carbonate Using Bubble Column Reactor

Abstract: The purpose of this study is to examine the possibility of establishing a novel CO2 absorption process with molten alkali carbonate using a bubble column reactor. In our previous study, a hot CO2 recovery process using Li4SiO4 suspended in molten Li2CO3–K2CO3 was developed. In the process, molten alkali carbonate itself showed great potential for CO2 absorption at high temperature. If a hot CO2 absorption process were established using only molten alkali carbonate, it could make the system simpler and the operating temperature range could be extended without the limitation of reaction temperature of solid absorbent. In the study, molten Li2CO3, Na2CO3, K2CO3 and its eutectic mixture were selected as CO2 absorbent. A bubble column was chosen as the device for gas absorption at high temperature. First, the CO2 absorption performance of each single molten alkali carbonate was investigated. The result showed that the molten Li2CO3 had a great ability to absorb CO2 at high temperature. Li2O was thought to be produced by decomposition of Li2CO3 during the melting and purging process and a reaction of CO2 with Li2O occurred during the absorption process. Further, the CO2 absorption performance of eutectic mixture increased exponentially with increasing the ratio of Li2CO3 in composition. Second, the possibility of establishing a CO2 absorption process using molten Li2CO3 was examined. The overall CO2 absorption process in the bubble column was investigated and the experimental results showed that the mass transfer of CO2 into molten Li2CO3 was the rate-controlling step. The operational conditions of the bubble column were optimized. The super cial gas velocity was an important operational parameter that a ected both the CO2 absorption rate and total amount of CO2 nally absorbed in the bubble column. The operating temperature also greatly a ected the amount of absorbed CO2.

Preparation of Isoamyl Acetate by High Performance ZSM-5 Zeolite Membrane

Abstract: Miao Xue1, Mei-Hua Zhu1, Cai-Jun Zhong1, Yu-Qin Li1, Na Hu1, Izumi Kumakiri2, Xiang Shu Chen1,2 and Hidetoshi Kita2 1 State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, Institute of Advanced Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, P. R. China 2 Department of Environmental Science and Engineering, Graduate School Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan