Preparation of Palladium Catalysts by Pretreatment Steps in Electroless Plating toward Partial Oxidation of Methanol with Steam Reforming

Abstract

ᠪҽ╫ɩɋȵ֭ᥴకᲦȡ᧸ǦǮɩɇɖʀɳȤոɛ‫ك‬ᕮ⋛ᕧტ‫ۀ‬අ Pd ╮ǽΰ⓯ ତአ↽ᨇ í ɿ‫ޗ‬ቆᗱ౪ɿ‫ڢ‬ᑼӡడଉ ɿ͑ʅᨇ ኇ‫ل‬গકগકрకકᮾ᳣ᲇ‫ك‬કకકଗფࢫ980-8579 ͜۞లԂ⊡ٚ∕ఫઆԂ⊡ 6-6-07 ଉ ᮸႒ᰓʄకᏡጋ࣠ᬬᮾ᳣ཀࢫ235-8501 ᑥᘛలᰚٚᄽ˛‫ڤ‬ᨊ A previously proposed method for depositing Ag nanoparticles on silica particles was extended to the preparation of ZnO-supported Pd PdZnO catalysts. The method presented in this work consists of two steps: 1 Sn 2ࢪ ions are adsorbed on the surfaces of ZnO particles, and 2 Pd 2ࢪ ions added are reduced by oxidization of Sn 2ࢪ to Sn 4ࢪ and simultaneously adsorbed on the surface. TEM observations revealed that Pd nanoparticles with an average size of 2-3 nm were formed on the 20 nm ZnO particles. The Pd nanoparticles were transformed into a Pd-Zn alloy by partial oxidation and steam reforming of methanol, and consequently the PdZnO attained CH 3 OH conversion efficiencies of 35-50ಚ at reaction temperatures of 310-370c C.

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

“…98, 99, 103 However, mixtures of ZnPd, Zn 3 Pd 2 , and ZnPd 2 have also been obtained by interaction between Pd and ZnO, depending on the synthesis conditions 1. 79 The Pd/CeO 2 system has been scrutinized in detail under comparable reducing conditions, but no signs of a well‐defined intermetallic compound have been observed up to 1180 K (over 20 h), neither by XRD, selected area electron diffraction (SAED), nor high‐resolution (HR)TEM analyses. A solid solution of Ce in the Pd structure was proposed instead 59.…”

“… Refs. : [a] 105; [b] 35; [c] 24; [d] 83; [e] 3–6, 48, 49; [f] 17, 102; [g] 92; [h] 3–5, 12, 24, 36, 37, 50–52, 54–65, 85–88, 118, 122, 124, 130, 131–135, 139, 141, 145, 147, 148, 150, 152, 153; [i] 79; [j] 3–6; [k] 12; [l] 50, 51, 58, 59, 74, 75; [m] 58, 59; [n] 3, 6; [o] 12; [p] 11; [q] 7; [r] 8; [s] 154; [t] 9; [u] 10; [v] 138. …”

Intermetallic Compounds in Catalysis

“…In the case of Pd/ZnO, a catalyst used for the decomposition (83), the partial oxidation (84)(85)(86)(87)(88)(89) and the steam reforming of methanol (90)(91)(92)(93)(94), the interaction between the supported Pd particles and the partial reduced support can lead to a mixture of ZnPd, Zn 3 Pd 2 , and ZnPd 2 . When this catalyst is used for the hydrogenation of unsaturated hydrocarbons, such as butenes, isoprene, or crotonaldehyde, only the formation of ZnPd is observed (95)(96)(97).…”