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New Uses for Hemicellulose
Published in Jorge M.T.B. Varejão, Biomass, Bioproducts and Biofuels, 2022
The hydrogenation process is a practical and easy alternative to reduce xylose to xylitol, since it does not generate any by-products or increases the ionic strength of the medium with the addition of any undesirable ionic species, as occurs with chemical reducers. The process uses hydrogen at low to medium pressures (PH2 = 3–50 atm), in the presence of a catalyst. The most used catalyst is Raney nickel, although several other hydrogenation catalysts can be used, such as noble metal salts (Pt, Pd, Ru). The last stage of production consists of isolation/purification and eventually crystallization of xylitol. The yield of the chemical process, as well as the quality of xylitol, are dependent on the purity of the initial xylose stream, since the presence of impurities interferes with the reduction process. In global terms, hydrogenation is a relatively simple and desirable technique, often a method to be chosen in the production of xylitol.
Global Outlook on the Availability of Critical Metals and Recycling Prospects from Rechargeable Batteries
Published in Abhilash, Ata Akcil, Critical and Rare Earth Elements, 2019
Pratima Meshram, B.D. Pandey, Abhilash
Nickel alloys are also used in industrial processes requiring catalytic assistance, for example, in petrochemical processing (cracking) and food processing (fat hydrogenation). Raney nickel is an example of a hydrogenation catalyst (developed in 1926), containing (by mass) ~90% Ni and 10% Al (Marafi and Stanislaus, 2008). Nickel spent catalysts have metallic nickel and nickel oxide, although nickel aluminate, spinel-like compounds, and nickel sulfides may occasionally occur, besides admixtures of coke, hydrocarbons, or fat. Hydro and pyrometallurgy are frequently used for metal recovery from spent catalysts (Marafi and Stanislaus, 2008; Singh, 2009). Leaching of nickel from spent catalysts in sulfuric acid, and separation as NiSO4 are most often practiced (Ivascan and Roman, 1975; Al-Mansi and Monem, 2002; Miazga and Mulak, 2008; Lee et al., 2010).
Syntheses, characterization and DFT studies of two new (π-allyl) palladium(II) complexes of β-8,9-dihydrohimachalene
Published in Journal of Coordination Chemistry, 2023
Abdelmajid Faris, Youssef Edder, Ismail Hdoufane, Intissar Ait Lahcen, Mohamed Saadi, Lahcen EL Ammari, Moha Berraho, Driss Cherqaoui, Brahim Boualy, Abdallah Karim
Raney nickel was obtained after treatment of Ni/Al (50%/50%) with 30% of NaOH. Then, in an autoclave, a mixture of α, γ and β-himachalene (1 g, 4.9 mmol) in 10 mL of ethanol and 0.5 g (8.47 mmol) of Raney nickel was added and the mixture was stirred for 12 h under hydrogen pressure (8 bars). After completion, the reaction mixture was filtered, and the filtrate was evaporated. The crude product was purified by silica gel column chromatography (hexane 100%). The structures of the obtained products were qualitatively determined by gas chromatography coupled with mass spectrometry.