Oxidation of furfural in aqueous H2O2 catalysed by titanium silicalite: Deactivation processes and role of extraframework Ti oxides

Abstract

2 Graphical abstract Highlights  The use of TS-1 for the oxidation of furfural to maleic acid with H2O2 is reported.  Extraframework TiO2 nanodomains can also be located in the channels and cavities of TS-1.  When present, it blocks the access of reactants to active sites.  Coke deposition and Ti leaching are identified as the main causes of deactivation. AbstractTitanium silicalites (TS-1) with different Ti/Si atomic ratio (0.01-0.08) have been prepared, characterised by different techniques (X-Ray Diffraction, Transmission Electron Microscopy and Raman, Diffuse Reflection Infrared Fourier Transform and XRay Photoelectron spectroscopies), and their catalytic properties were investigated for the liquid phase oxidation of furfural with aqueous H2O2. For samples prepared with an initial Ti/Si > 0.01, extraframework Ti oxide is present and become more important as Ti loading increases. Two types of extraframework Ti have been identified: (i) anatase Ti oxide located at the external surface of zeolite crystals and (ii) Ti oxide nanodomains occluded within the channels and cavities of the zeolite. The latter can block the access of reactants to the active framework Ti(IV) sites for samples prepared with an initial Ti/Si > 0.04 and their removal results in an improvement in the selective oxidation of furfural to valuable products. The fouling by deposition of heavy by-products and Ti leaching were identified as two main causes of catalyst deactivation. The former can be reverted by removal of the deposits through calcination under air at 773 K. Leaching affects both the extraframework Ti and the active framework Ti species. During the first runs of reutilization, the Ti leaching is severe, affecting mainly to extraframework Ti oxide. Initially this leaching may be positive because its removal leads to the 3 elimination of species blocking the access of reactants to the active Ti species; but in the longer term, the continuous leaching of active framework Ti irreversibly deactivates the catalyst.

Kinetics and modelling of furfural oxidation with hydrogen peroxide over a fibrous heterogeneous catalyst: effect of reaction parameters on yields of succinic acid

“…Another possibility to perform oxidation in the aqueous phase is to use hydrogen peroxide. The reaction can be carried out under the autocatalytic effect of acids, which are formed in the reaction mixture or in the presence of metal‐containing catalysts such as sodium molybdate, vanadium sulphate, vanadium pentoxide, sodium vanadate, vanadium, niobium, molybdenum, chromium salts, vanadyl sulphate‐sodium acetate system, niobium pentoxide, magnesium salts and titanium silicate . These metal‐containing catalysts provoke hydrogen peroxide decomposition and suffer from catalyst deactivation by leaching of the active metal.…”

Added-Value Chemicals from Lignin Oxidation

“…Guaiacol peroxide oxidation using TS-1 in mild alkaline conditions achieved high percentages of MA and oxalic acid, with small percentages of FA and MAL [ 98 ]. Other works oxidizing furfural reported good yields on MA [ 99 , 100 ]. Following these promising results, the LSRE research group selected this catalyst to evaluate the conversion of lignin and lignin model compounds into C 4 -DCA, with particular attention on SA yield, due to its high value to polymer production and chemical precursor [ 13 , 65 ].…”

Value-Added Bio-Chemicals Commodities from Catalytic Conversion of Biomass Derived Furan-Compounds

“…In the last years different conversion routes have been technically demonstrated to turn this petrochemical into a renewable chemical by the oxidation of different renewable platforms like 1-butanol [69], levulinic acid [70], HMF [33,[71][72][73] and FF [13,31,[74][75][76][77][78][79][80][81] using O 2 (see Table 4). Moreover, contrary to the current conventional process carried out in the gas phase, depending on the reaction conditions and the used reactant, the MAN production can be performed in the aqueous or gas phase.…”