The importance of pre-treatment of spent hydrotreating catalysts on metals recovery

Abstract

Recebido em 25/1/10; aceito em 2/6/10; publicado na web em 17/9/10 This work describes a three-step pre-treatment route for processing spent commercial NiMo/Al 2 O 3 catalysts. Extraction of soluble coke with n-hexane and/or leaching of foulant elements with oxalic acid were performed before burning insoluble coke under air. Oxidized catalysts were leached with 9 mol L -1 sulfuric acid. Iron was the only foulant element partially leached by oxalic acid. The amount of insoluble matter in sulfuric acid was drastically reduced when iron and/or soluble coke were previously removed. Losses of active phase metals (Ni, Mo) during leaching with oxalic acid were compensated by the increase of their recovery in the sulfuric acid leachate.

Processing of spent NiW/Al2O3 catalysts

“…This value agrees with the amounts reported in the literature for spent HDT catalysts 1,8,25 (12-30 wt.%). The volatile matter is basically due to coke burning (CO 2 , H 2 O).…”

Advances in Ethanol Reforming for the Production of Hydrogen

“…For this process, the catalyst must be stable, active, selective, and maximize hydrogen production while minimizing the generation of byproducts, such as CO and CH 4 . Addition of a metal dopant or precursor improves the activity of catalysts in most cases.…”

“…Therefore, for bringing about greater conversions of CO and H 2 , the WGSR reaction is performed in two steps: a high-temperature shift (HTS; 623-643 K) and low-temperature shift (LTS; 473-493 K). 5 However, alternate reactions can lead to ethanol decomposition (pathways 2, 4, and 5), which results in a series of undesirable reactions (pathways 6 and 7) that can lead to the production of CH 4 and C 2 H 4 . The latter favors coal-production pathways, which causes coking of the catalyst (pathways 8, 12, and 13), and consequently hinders hydrogen production.…”

“…3 In addition, the regeneration and reuse of the catalysts are features that must be considered for a more efficient application. 4 Various review articles on the design of the catalyst for the SRE have been published. 2,[5][6][7] In these articles, the selection of active metals and catalyst support has been analyzed as the critical factor that allows for obtaining catalysts with high activity and selectivity.…”

Contextualizando reações ácido-base de acordo com a teoria protônica de Brönsted-Lowry usando comprimidos de propranolol e nimesulida

“…A nimesulida (Figura 1) é um fármaco anti-inflamatório não esteroide (AINE) prescrito no Brasil como anti-inflamatório, analgésico e antitérmico. 7 A segurança do uso farmacológico de nimesulida tem sido amplamente discutida pelos países da União Europeia devido a inúmeros relatos de insuficiência hepática produzida pelo uso contínuo e prolongado deste fármaco. Apesar disto, a ANVISA ainda mantém a autorização para a comercialização deste anti-inflamatório no Brasil para crianças acima de 12 anos de idade.…”