TEMPO-Ru-BEA Composite Material for the Selective Oxidation of Alcohols to Aldehydes

Abstract

The selective aerobic oxidation of alcohols to aldehydes is an important industrial challenge due to the easy further overoxidation of these products to acids and esters. The most common industrial methods require organic radicals such as 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO) for the selective conversion of alcohols to carbonyl compounds with the formation of TEMPOH, which can be regenerated back to TEMPO by oxygen over metal complexes. The high cost and difficulties related to the separation of complexes prompted us to develop heterogeneous catalysts by coordinating TEMPO over acid sites in zeolite BEA with encapsulated RuO2 nanoparticles. The catalyst demonstrates excellent activity, selectivity, and stability for the oxidation of alcohols to aldehydes. The analysis of the reaction mechanism confirms the activation of alcohols by TEMPO and the subsequent regeneration of TEMPOH by RuO2.

Probing Local pH Change during Electrode Oxidation of TEMPO Derivative: Implication of Redox-Induced Acidity Alternation by Imidazolium-Linker Functional Groups

“…The solution pH of 0.1 M MIMAcO-T at equilibrium is 3.2. Thus, the equilibrium constant of reaction 3, K eq,(2) , is 4 × 10 −6 M. The change in bulk pH, ΔpH bulk , of a 5 mM MIMAcO-T solution was measured as a function of time to determine the forward rate constant of reaction 3, k f, (2) . The initial pH was adjusted to 6.4, and ΔpH bulk was plotted versus time for MIMAcO-T and for blank and 4-OH-T solutions as a control (Figure 2b).…”

Organic Synthesis Using Nitroxides

“…For example, RuCl 2 (PPh 3 ) 3 was employed in combination with a superstoichiometric amount of 4-benzoyloxy-TEMPO under oxygen atmosphere, and for primary alcohols α-aminoxygenated alkanals and for secondary alcohols ketones were obtained . By using a catalytic amount of TEMPO at an oxygen pressure of 10 bar, oxidation of aliphatic alcohols was achieved. − Ruthenium dioxide nanoparticles, polymer-incarcerated ruthenium under thermal conditions, and a ruthenium or iridium photoredox catalyst , with irradiation also act as cooperative catalysts in TEMPO-catalyzed alcohol oxidation using oxygen as the terminal oxidant.…”

“…578 By using a catalytic amount of TEMPO at an oxygen pressure of 10 bar, oxidation of aliphatic alcohols was achieved. 579−581 Ruthenium dioxide nanoparticles, 582 polymer-incarcerated ruthenium 583 under thermal conditions, and a ruthenium or iridium photoredox catalyst 562,584 with irradiation also act as cooperative catalysts in TEMPO-catalyzed alcohol oxidation using oxygen as the terminal oxidant.…”

Electrochemical Properties and Local Structure of the TEMPO/TEMPO+ Redox Pair in Ionic Liquids

“…It is used in energy storage devices (dye-sensitized solar cell, redox flow batteries, Li–O 2 batteries, supercapacitors, etc. ), − as spin labels in the electron spin resonance (ESR) technique, , as a catalyst for biomass and cellulose processing, , and for the oxidation of alcohols to aldehydes . Therefore, finding a way of tuning the reactivity of TEMPO becomes an important issue in the context of the development of new TEMPO-based systems and improvement of the performance of the existing ones.…”