When high metal dispersion has a detrimental effect: Hydrogen peroxide direct synthesis under very mild and nonexplosive conditions catalyzed by Pd supported on silica

Synthesis and performance of PdMulti@HCS catalysts with Pd nanoparticles partially embedded in the inner wall of hollow carbon spheres for the direct synthesis of hydrogen peroxide from hydrogen and oxygen

PdMulti@HCS catalysts ensure the maximum exposure of Pd active sites and optimal transfer and diffusion ability for H2O2 synthesis.

Direct synthesis of H2O2 over Pd–M@HCS (M = Sn, Fe, Co, or Ni): effects of non-noble metal M on the electronic state and particle size of Pd

Direct synthesis of H2O2 in a yolk–shell structure assisted by M (M = Fe,Co,Ni,Sn) metal doping.

Effect of polyvinylpyrrolidone (PVP) on palladium catalysts for direct synthesis of hydrogen peroxide from hydrogen and oxygen

Addition of polyvinylpyrrolidone to Pd/SiO₂ catalyst improved H₂O₂ selectivity by adjusting electronic state of palladium active species.

Looking for the “Dream Catalyst” for Hydrogen Peroxide Production from Hydrogen and Oxygen

The reaction between hydrogen and oxygen is in principle the simplest method to form hydrogen peroxide, but it is still a “dream process”, thus needing a “dream catalyst”. The aim of this review is to analyze critically the different heterogeneous catalysts used for the direct synthesis of H2O2 trying to determine the features that the ideal or “dream catalyst” should possess. This analysis will refer specifically to the following points: (i) the choice of the metal; (ii) the metal promoters used to improve the activity and/or the selectivity; (iii) the role of different supports and their acidic properties; (iv) the addition of halide promoters to inhibit undesired side reactions; (v) the addition of other promoters; (vi) the effects of particle morphology; and (vii) the effects of different synthetic methods on catalyst morphology and performance.

Boosting the Characterization of Heterogeneous Catalysts for H2O2 Direct Synthesis by Infrared Spectroscopy

Infrared (IR) spectroscopy is among the most powerful spectroscopic techniques available for the morphological and physico-chemical characterization of catalytic systems, since it provides information on (i) the surface sites at an atomic level, (ii) the nature and structure of the surface or adsorbed species, as well as (iii) the strength of the chemical bonds and (iv) the reaction mechanism. In this review, an overview of the main contributions that have been determined, starting from IR absorption spectroscopy studies of catalytic systems for H2O2 direct synthesis, is given. Which kind of information can be extracted from IR data? IR spectroscopy detects the vibrational transitions induced in a material by interaction with an electromagnetic field in the IR range. To be IR active, a change in the dipole moment of the species must occur, according to well-defined selection rules. The discussion will be focused on the advancing research in the use of probe molecules to identify (and possibly, quantify) specific catalytic sites. The experiments that will be presented and discussed have been carried out mainly in the mid-IR frequency range, between approximately 700 and 4000 cm−1, in which most of the molecular vibrations absorb light. Some challenging possibilities of utilizing IR spectroscopy for future characterization have also been envisaged.

Recent Advances in the Direct Synthesis of Hydrogen Peroxide Using Chemical Catalysis—A Review

Hydrogen peroxide is an important chemical of increasing demand in today’s world. Currently, the anthraquinone autoxidation process dominates the industrial production of hydrogen peroxide. Herein, hydrogen and oxygen are reacted indirectly in the presence of quinones to yield hydrogen peroxide. Owing to the complexity and multi-step nature of the process, it is advantageous to replace the process with an easier and straightforward one. The direct synthesis of hydrogen peroxide from its constituent reagents is an effective and clean route to achieve this goal. Factors such as water formation due to thermodynamics, explosion risk, and the stability of the hydrogen peroxide produced hinder the applicability of this process at an industrial level. Currently, the catalysis for the direct synthesis reaction is palladium based and the research into finding an effective and active catalyst has been ongoing for more than a century now. Palladium in its pure form, or alloyed with certain metals, are some of the new generation of catalysts that are extensively researched. Additionally, to prevent the decomposition of hydrogen peroxide to water, the process is stabilized by adding certain promoters such as mineral acids and halides. A major part of today’s research in this field focusses on the reactor and the mode of operation required for synthesizing hydrogen peroxide. The emergence of microreactor technology has helped in setting up this synthesis in a continuous mode, which could possibly replace the anthraquinone process in the near future. This review will focus on the recent findings of the scientific community in terms of reaction engineering, catalyst and reactor design in the direct synthesis of hydrogen peroxide.

TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis: the influence of N and Au doping

Nitrogen doping is a new strategy to improve catalysts for H₂O₂ direct synthesis.

Depressing the hydrogenation and decomposition reaction in H2O2 synthesis by supporting AuPd on oxygen functionalized carbon nanofibers

The introduction of oxygen functionalities to the surface of CNFs depressed the hydrogenation and decomposition reaction during the synthesis of H₂O₂.

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over activated-carbon-supported Pd–Ag alloy catalysts

A series of bimetallic PdAg catalysts on an activated carbon support were prepared for the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The addition of Ag to Pd caused an increase in selectivity due to ensemble and electronic effects.

A highly stable Pd/SiO2/cordierite monolith catalyst for 2-ethyl-anthraquinone hydrogenation

Pd/SiO₂/cordierite monolith catalysts show superior stability in a 1000 h test for anthraquinone hydrogenation.

Lamellar Ni/Al-SBA-15 fibers: preparation, characterization, and applications as highly efficient catalysts for amine and imine syntheses

A novel lamellar Ni/Al-SBA-15 fiber catalyst was prepared and successfully utilized in one-pot syntheses of amines and imines.