Advances in the production technology of hydrogen peroxide (2023)

Hydrogenation of 2-ethyl-anthraquinone (EAQ) is a key reaction in the anthraquinone process for industrial production of H₂O₂, a green chemical with a variety of applications. Herein, Ce-doped SBA-15 was synthesized via a one-step hydrothermal method with ethylenediamine as pH regulator and explored as the support of Pd catalyst for EAQ hydrogenation. Part of Ce species was incorporated into SBA-15 framework and the rest existed as extra-framework Ce and fluorite phase CeO₂ particles. The framework Ce species had a suppressing effect on the aggregation of Pd particles. Their amount increased with lowering Si/Ce molar ratio (SCA) from 50 to 20 and reached a plateau at 30. The content of Ce³⁺ and the number of oxygen vacancies showed the same trend as the amount of framework Ce with SCA, but monotonously increased with raising reduction temperature from 200 to 600°C. In addition, hydrogen spillover from metal to support and an increase in the binding energy of Pd were observed. Compared with Pd/SBA-15, Ce-doped catalysts presented significantly improved catalytic performance. Among them, the catalyst with SCA of 30 and reduced at 400°C exhibited the highest activity (3.8 times of Pd/SBA-15) and selectivity to 2-ethyl-anthrahydroquinone (94.2% from 91.8% over Pd/SBA-15).

We report an approach of direct production of H₂O₂ from water by applying altering potential in the electrocatalysis. By switching potentials periodically between positive to negative, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) occurs sequentially on a single electrode loaded catalysts, which leads to the reduction of the newly-formed OER active species, forming H₂O₂ directly. The H₂O₂ production is dependent on the time and potentials of OER and ORR, which is optimized in this study. Besides, a waiting time is set after each period to let H₂O₂ diffusion from the catalyst surface. Different catalysts are employed to test the feasibility of this approach, including glassy carbon, graphene oxide, nickel particles, nickel foam, and palladium particles. All these catalysts result in the production of H₂O₂ at various reaction rates. Ni offers the highest H₂O₂ productivity. With the prolonging of the reaction time, the decomposition of H₂O₂ occurs on the surface of Ni catalysts, which is inhibited by the addition of Zn into the catalysts. The in-situ generated H₂O₂ is used for partial oxidation of propylene by passing propylene into the porous electrode during the reaction, which lead to the formation of dimethyl ether and adipic acid. This study shows a new route of the direct synthesis and utilization of H₂O₂ for the generation of valuable chemicals.

Among the currently multitudinous analytical methods for hydrogen peroxide (H₂O₂), photoelectrochemical (PEC) sensors stand out for their potential advantages of high sensitivity, low cost, and easy preparation. In this work, WO₃/Mo:BiVO₄ heterojunction photoanode was constructed for non-enzymatic H₂O₂ sensing via PEC route. At first, WO₃ nanoplates was prepared by chemical bath method, then WO₃/Mo:BiVO₄ composite was achieved by spin coating Mo:BiVO₄ film on the surface of WO₃. Such heterojunction structure allow photogenerated electrons transferred into WO₃ and holes accumulated on Mo:BiVO₄, which boosts the charges separation and decreases charge carrier recombination, thus resulting a remarkable enhancement for H₂O₂ sensing. As a result, the WO₃/Mo:BiVO₄ photoanode presents a sensitive response of 186.2 μA cm⁻² mM⁻¹ for H₂O₂ detection in the concentration region of 0.1-2.0 mM accompanied with a good correlation coefficient of 0.996, this sensing performance is much superior than the pristine WO₃ photoanode. Furthermore, the fabricated heterojunction sensor has a good stability and distinguish H₂O₂ from the interferents of ascorbic acid (AA), uric acid (UA), glucose and common inorganic salts, etc. This study provides an efficient way for H₂O₂ detection and inspires more interests in the design and construction of a novel heterojunction for advanced PEC analysis.

Acetonitrile is used as an effective, non-corrosive selectivity enhancer for the direct synthesis of hydrogen peroxide (HP). Palladium catalysts supported by activated carbon or poly-divinylbenzene are poisoned by acetonitrile, which makes them very little productive. Conversely the catalysts supported by strongly acidic ion-exchange resin are much more selective and productive in the presence of acetonitrile, and for relatively long time. TEM shows that the size of their metal nanoparticles can be decreased by a reconstruction process, possibly sustained by leached palladium(II) species. HP decomposition experiments show that acetonitrile inhibits the OO bonds splitting.

The photosynthesis of H₂O₂ is a promising green process that is expected to revolutionize industrial H₂O₂ synthesis. However, it is still far from application because of the limited performance of photocatalysts. In this study, benzyl alcohol (BA) is excited under UV light with a wavelength shorter than 400nm after it forms an epoxy with dissolved oxygen to generate high-concentration H₂O₂ without a photocatalyst. An H₂O₂ yield of up to 176.43mM·h⁻¹ in aqueous solution is achieved, which is close to the yield required for commercial production. The by-product benzaldehyde (BD) accelerates H₂O₂ production in the early stage but consumes H₂O₂ in the later stage, where it is further converted to benzoic acid (BC). In this photoreaction, only air is employed as the oxidant, and sunlight provides the reaction energy; no photocatalyst is needed. This reaction, combined with a simple mild H₂ reduction process using BD, can be used for green closed-loop H₂O₂ production without waste and by-product discharge, where BA is a recycled intermediate. This study provides a sustainable strategy for low-cost, low-energy H₂O₂ production with excellent application potential.

Hydrogen peroxide (H₂O₂), one of the most versatile oxidants in industry, is widely used in the production of chemicals and medicines, sterilization, and bleaching. The direct synthesis of H₂O₂ from hydrogen and oxygen is an environmental-friendly route to replace the anthraquinone method, while the selectivity and activity are greatly affected by the electronic environment of active sites, e.g., Pd species. Here, we report a catalyst with trace amounts of Pt single atoms as electronic promoters in fully exposed Pd clusters on TiO₂, which exhibits superior catalytic performance (37.3mol g_Pd⁻¹h⁻¹H₂O₂ productivity and 86.5% H₂O₂ selectivity) for the direct synthesis of H₂O₂. The results of in situ CO-DRIFTS, XPS, isotope experiments, and DFT calculations demonstrate that the addition of Pt single atoms in fully exposed Pd clusters modifies the electronic structure to generate electron-rich Pd species, which favors H₂ dissociation and *OOH formation, thus enhancing H₂O₂ productivity and selectivity.

Molecular Catalysis, Volume 429, 2017, pp. 43-50

Pd catalysts prepared by a sonochemical method that is known to be effective in metal dispersion are applied to direct H₂O₂ synthesis. To determine the effect of the preparation method on the catalytic performance, Pd catalysts were supported on TiO₂ and SiO₂ by a sonochemical method and general incipient wetness method (IWI), and supports were compared. The sonochemical preparation method achieved the highest Pd dispersion value of 16.6% in the TiO₂ supported catalyst, which is attributed to a synergistic effect between the sonochemical method and TiO₂ support. A near-homogeneous and small size nucleation is often reported in sonochemical methods, and oxygen vacancies in TiO₂ are reported to be strong adsorption sites for Pd nucleation. However, SiO₂ support has not been reported to have obvious oxygen vacancies, and sonochemically prepared Pd/SiO₂ showed the lowest Pd dispersion in addition to a large Pd particle size. In the direct synthesis of H₂O₂, a remarkably high H₂ conversion of 22% was achieved in sonochemical Pd/TiO₂, which led to the highest H₂O₂ yield of 16% and H₂O₂ production rate of 729.0mmol/g_{Pd h}.

Applied Catalysis A: General, Volume 517, 2016, pp. 168-175

Highly dispersed Pd/SiO₂/cordierite monolith catalysts (PSC) were prepared to investigate the influence of support alkalinity on 2-ethyl-anthraquinone (eAQ) hydrogenation. The support alkalinity was adjusted by the MgO content in SiO₂ washcoat. The behavior of the PSC catalysts was tested by liquid phase hydrogenation of eAQ in a continuous trickle bed reactor. PSC catalyst with 2wt.% MgO (Mg-2 sample) exhibited excellent for hydrogenation of eAQ. The support alkalinity directly influenced the electronic properties of the Pd nanoparticles as proved by Fourier transformed infrared spectroscopy with CO probe molecule and X-ray photoelectron spectroscopy. The electron density at lower binding energy of the supported Pd particles increased with the increasing alkalinity. PSC catalysts with alkali modifiers exhibited higher hydrogenation efficiency for benefiting the activation of CO group in eAQ and the adsorption of eAQ via the enhanced interaction of lone pair of CO electrons. However, increased support alkalinity contributed to higher Pd loss due to the weak coating strength. Besides, the active quinone selectivity decreased with the progressive MgO addition due to the tautomerization of 2-ethylanthrahydroquinone to 2-ethyloxoanthrone, which is the precursor of other degradations. Consequently, a volcano shape curve between hydrogenation efficiency (H₂O₂ yield) and MgO content was obtained.

Chinese Journal of Catalysis, Volume 39, Issue 6, 2018, pp. 1070-1080

We studied the hydrogenation of 2-ethylanthraquinone (eAQ) over Pd/SiO₂/COR (COR = cordierite) monometallic and Pd-M/SiO₂/COR (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts, which were prepared by the co-impregnation method. Detailed investigations showed that the particle sizes and structures of the Pd-M (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts were greatly affected by the second metal M and the mass ratio of Pd to the second metal M. By virtue of the small particle size and the strong interaction between Pd and Ni of Pd-Ni alloy, Pd-Ni bimetallic monolithic catalysts with the mass ratio of Pd/Ni = 2 achieved the highest H₂O₂ yield (7.5 g/L) and selectivity (95.3%). Moreover, density functional theory calculations were performed for eAQ adsorption to gain a better mechanistic understanding of the molecule-surface interactions between eAQ and the Pd(1 1 1) or PdM(1 1 1) (M = Ni, Fe, Mn, and Cu) surfaces. It was found that the high activity of the bimetallic Pd-Ni catalyst was a result of strong chemisorption between Pd₃Ni₁ (1 1 1) and the carbonyl group of eAQ.

Applied Catalysis A: General, Volume 528, 2016, pp. 168-174

Highly dispersed Pd/AlPO-5 catalyst was prepared and tested in the hydrogenation of 2-ethylanthraquinone. Characterization results suggested that the abundant surface P-OH groups of AlPO-5 zeolite substituted NH₃ ligands of [Pd(NH₃)₄]²⁺ precursor to form [Pd(NH₃)₃(POH)]²⁺. After calcination, the latter formed Pd-O-P interfacial linkage between Pd nanoparticles and AlPO-5, benefiting the suppression of Pd sintering. SiO₂ and SiO₂-AlPO-5 composite were used as supports for comparison. Catalyst supported on SiO₂-AlPO-5 composite (25wt% AlPO-5) exhibited improved catalytic activity and stability in consideration of reactant activation as well as the mass transfer of reactant molecules, which is expected to decrease precious metal loading in industrial application.

Food Chemistry, Volume 332, 2020, Article 127229

Hydrogen peroxide plays a key role in honey antibacterial activity. The production of H₂O₂ in honey requires glucose oxidase (GOx) that oxidizes glucose to gluconolactone and reduces molecular oxygen to hydrogen peroxide. The content of GOx of honeybee origin was believed to be the main predictor of H₂O₂ concentration in honey. The observed variations in H₂O₂ levels among honeys questioned however the direct GOx-H₂O₂ relationship and left its absence opened for exploration. Here, we evaluated principal causes underlying the imbalance in the quantitative enzyme-product relationship with respect to: (a) enzyme and the product inactivation or destruction by honey compounds; (b) non-enzymatic pathway of H₂O₂ formation, and (c) a potential contribution of enzymes with GOx activity originating from nectars and microorganisms inhabiting honey. We also bring new facts on the relationship between honey colloidal structure and H₂O₂ production that change our traditional understanding of honey function as antimicrobial agent.

Chinese Journal of Catalysis, Volume 39, Issue 4, 2018, pp. 673-681

TiO₂-supported Pd-Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H₂O₂ at ambient pressure. The addition of Sb to Pd significantly enhanced catalytic performance, and a Pd₅₀Sb catalyst showed the greatest selectivity of up to 73%. Sb promoted the dispersion of Pd on TiO₂, as evidenced by transmission electron microscopy and X-ray diffraction. X-ray photoelectron spectroscopy indicated that the oxidation of Pd was suppressed by Sb. In addition, Sb₂O₃ layers were formed and partially wrapped the surfaces of Pd catalysts, thus suppressing the activation of H₂ and subsequent hydrogenation of H₂O₂. In situ diffuse reflection infrared Fourier transform spectroscopy for CO adsorption suggested that Sb homogenously located on the surface of Pd-Sb catalysts and isolated contiguous Pd sites, resulting in the rise of the ratio of Pd monomer sites that are favorable for H₂O₂ formation. As a result, the Sb modified Pd surfaces significantly enhanced the non-dissociative activation of O₂ and H₂O₂ selectivity.