Propene epoxidation with in‐site H2O2 produced by H2/O2 non‐equilibrium plasma

Zhao, Jianghong; Zhou, Juncheng; Su, Junfeng; Guo, Hongchen; Wang, Xiangsheng; Gong, Weimin

doi:10.1002/aic.11317

Cited by 31 publications

(24 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1,2 Despite its importance, there is still no direct oxidation process that uses only propene and molecular oxygen (O 2 ) as reactants for industrial propylene oxide production. [3][4][5][6][7][8][9] The cumene hydroperoxide process also consumes one equivalent of H 2 to produce mainly water as the co-product. The chlorohydrin process produces enormous amounts of byproducts in the form of salts and chlorinated organic molecules.…”

Section: Introductionmentioning

confidence: 99%

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

Manz

2015

RSC Adv.

View full text Add to dashboard Cite

New zirconium (Zr) based organometallic catalysts for direct olefin epoxidation using O 2 as oxidant without coreductant were introduced in a previous computational study (T. A. Manz and B. Yang, RSC Adv., 2014, 4, 27755-27774). In this paper, we use density functional theory (DFT) to study three Hf-based catalysts with the same bis(bidentate) ligands as the preceding Zr-based catalysts: (a) the diimine ligand N(Ar)-CH-CH-N(Ar) aka NCCN, (b) the imine-nitrone ligand N(Ar)-CH-CH-N(Ar)-O aka NCCNO, and (c) the dinitrone ligand O-N(Ar)-CH-CH-N(Ar)-O aka ONCCNO [Ar ¼ -C 6 H 3 -2,6-i Pr 2 ]. Complete reaction cycles and energetic spans (i.e., effective activation energies for the entire catalytic cycle) are computed for propene epoxidation. For Hf_NCCNO and Hf_ONCCNO, the reaction cycles are similar to the Zr-basedanalogs and the formation of h 3 -ozone intermediates is still crucial. Hf_ONCCNO has a large enthalpic energetic span (60.4 kcal mol À1 ) due to forming inert octahedral complexes as the catalyst resting state.Our calculations predict an energetic span $40 kcal mol À1 for Hf_NCCN, which indicates it will not be a good catalyst. Computed enthalpic energetic spans of $30 kcal mol À1 are achieved for the Hf_NCCNO and Zr_NCCNO catalysts; however, transfer of allylic hydrogen from the reaction product forms a low energy deactivation product. Therefore, the Hf_NCCNO and Zr_NCCNO catalysts are only suitable for direct epoxidation of alkenes that do not have any allylic hydrogen atoms. As an example of an alkene with no allylic hydrogens, we computed enthalpic energetic spans (kcal mol À1 ) for direct ethylene epoxidation of (a) 25.0 for Hf_NCCNO, (b) 30.2 for Zr_NCCNO, and (c) 52.7 for Zr_NCCN. † Electronic supplementary information (ESI) available: DFT-optimized geometries and energies; imaginary frequency for each transition state; singlet-triplet crossing curves for O 2 addition to Hf_ONCCNO and Hf_NCCN dioxo complexes; constrained optimization curves showing oxo h 3 -ozone and peroxo h 3 -ozone complexes do not exist for the Hf_NCCN system; chemical potential diagrams for Hf_ONCCNO and Hf_NCCN; assigned spin magnetic moments tables; master cycle and table of reaction energies and energetic spans for direct propene epoxidation catalyzed by Hf_ONCCNO; master cycles and tables of reaction energies and energetic spans for direct ethylene epoxidation catalyzed by Zr_NCCN, Hf_NCCNO, and Zr_NCCNO. See

show abstract

Section: Introductionmentioning

confidence: 99%

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

Manz

2015

RSC Adv.

View full text Add to dashboard Cite

show abstract

“…In several liquid-phase epoxidation routes to convert propene into propene oxide, much attention has been directed to heterogeneous catalytic oxidation using hydrogen peroxide as a more environmentally benign and profitable chemical process [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Titanium silicalite (TS-1) catalyst has been extensively investigated for this route because propene oxide can be produced with a high selectivity in methanol under mild conditions [4,5,[10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

The effects of impregnation of precious metals on the catalytic activity of titanium silicate (TS-1) in epoxidation of propene using hydrogen peroxide

Shin

Lee

Chadwick

2016

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

Propene oxide is an important chemical intermediate and titanium silicalite (TS-1) has been widely investigated as a promising catalyst for the direct epoxidation of propene with ex-situ or in-situ produced hydrogen peroxide as an oxidant. In order to clarify the effects of the kind of precious metal and treatment process in the catalyst preparation on the propene epoxidation and the hydrogen peroxide decomposition, TS-1 was impregnated with gold and palladium via drying, calcination and reduction and the experiments to check its catalytic performance were conducted in a gas aspirating autoclave reactor in the absence of mass transfer limitations. The presence of precious metals vigorously catalyzed the side reactions and hydrogen peroxide decomposition. Some of the precious metal containing TS-1 catalysts showed high initial rates but there was no catalyst with a propene oxide yield after 5 h reaction time comparable to TS-1 alone because of the enhancement of side reactions by precious metals. The significant decline in the selectivity to propene oxide over the dried precious metal containing TS-1 catalysts was attributed to the leaching of precious metals into the reaction medium. Palladium containing TS-1 showed exceptionally high decomposition of hydrogen peroxide. Reduction and calcination increased the decomposition by forming metallic gold and palladium. Homogeneous dispersion of gold nanoparticles was achieved by a sol immobilization method which led to a decrease of propene oxide selectivity and an increase of hydrogen peroxide decomposition.

show abstract

“…It has also been successfully integrated with a titanium silicate molecular sieve catalyst for propene epoxidation. [28] On the other hand, the selectivity of H 2 O 2 should be improved further, because it is still much lower than that of the AQ process (above 95 %); moreover, more energy efficient means of triggering the H 2 /O 2 plasma reaction should be studied in the future. Significantly, the mechanism of the control process sheds new light on plasma chemistry, [29] radical chemistry, [30,31] and material treatment by plasma.…”

Section: Methodsmentioning

confidence: 99%

Safe Direct Synthesis of High Purity H₂O₂ through a H₂/O₂ Plasma Reaction

Zhou

Guo

et al. 2013

Angewandte Chemie

Self Cite

View full text Add to dashboard Cite

Hydrogen peroxide (H 2 O 2 ), the most desired green oxidant, [1] is almost exclusively produced by an anthraquinone (AQ) process. [2] Direct oxidation of H 2 with O 2 has long been considered an ideal alternative for H 2 O 2 production. [3] Extensive studies have been done on direct H 2 O 2 synthesis from a H 2 /O 2 mixture. To achieve high efficiency, direct H 2 O 2 synthesis is generally performed in acidified solvent over supported noble-metal catalysts (Au, Pd, Au-Pd, and Pd-Pt). [4][5][6][7][8][9][10][11] However, the direct synthesis of H 2 O 2 from a H 2 /O 2 mixture catalyzed by metals is quite hazardous, and it is very difficult to directly obtain high-purity and high-concentration H 2 O 2 .Research [12,13] published in the 1960s has demonstrated that H 2 O 2 can be generated in H 2 /O 2 non-equilibrium plasma through free-radical reactions in the absence of any catalyst or chemical. However, this plasma method has not yet drawn much attention, owing to low H 2 O 2 yield (less than ca. 5 %) and safety concerns about the discharge-triggered H 2 /O 2 reaction. [12,14] The content of O 2 must be strictly controlled below 4 mol % in order to prevent explosion and ignition. [15] Our previous research [16] showed that the structure of the plasma reactor played an important role in the direct synthesis of H 2 O 2 . A H 2 /O 2 mixture containing 3 mol % of O 2 reaches 100 % O 2 conversion, but the H 2 O 2 selectivity is only 3.5 % (based on O 2 ) in a single dielectric barrier discharge (SDBD) plasma reactor with a naked metal highvoltage (HV) electrode and an aqueous grounding electrode. On the other hand, 57.8 % O 2 conversion and 56.3 % H 2 O 2 selectivity (based on O 2 ) can be obtained by using a double dielectric barrier discharge (DDBD) plasma reactor with a pyrex-covered metal HV electrode (the pyrex cover acts as an additional dielectric barrier) and an aqueous grounding electrode. Although the selectivity has been greatly improved, the safety concerns and low efficiency, owing to low O 2 content, are still big challenges.Herein, we report an experimental realization of controllable H 2 /O 2 combustion processes by an optimized plasma reactor. High purity (Grade 1 electronic grade H 2 O 2 according to the SEMI standard) and highly concentrated H 2 O 2 solution (ca. 60 wt %) can be directly produced from a H 2 /O 2 mixture without explosion. These results suggest a different mechanism from conventional H 2 /O 2 combustion processes in the H 2 /O 2 plasma reaction. As shown in Scheme 1, the electron activation of H 2 into H is responsible for H 2 O 2 formation. However, the electron activation of O 2 into O and O 2 * (vibrational and electronic excited states) leads to H 2 O formation and explosion of the H 2 /O 2 mixture. Moreover, low-electron-density H 2 /O 2 plasma leads to a low degree of H 2 and O 2 activation, which plays quite a significant role in producing H 2 O 2 and controlling H 2 /O 2 combustion.The plasma reactor used in our experiments is a double aqueous electrode DDBD reactor (Support...

show abstract

Propene epoxidation with in‐site H₂O₂ produced by H₂/O₂ non‐equilibrium plasma

Cited by 31 publications

References 25 publications

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

The effects of impregnation of precious metals on the catalytic activity of titanium silicate (TS-1) in epoxidation of propene using hydrogen peroxide

Safe Direct Synthesis of High Purity H₂O₂ through a H₂/O₂ Plasma Reaction

Contact Info

Product

Resources

About

Propene epoxidation with in‐site H2O2 produced by H2/O2 non‐equilibrium plasma

Cited by 31 publications

References 25 publications

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

Hafnium catalysts for direct alkene epoxidation using molecular oxygen as oxidant

The effects of impregnation of precious metals on the catalytic activity of titanium silicate (TS-1) in epoxidation of propene using hydrogen peroxide

Safe Direct Synthesis of High Purity H2O2 through a H2/O2 Plasma Reaction

Contact Info

Product

Resources

About

Propene epoxidation with in‐site H₂O₂ produced by H₂/O₂ non‐equilibrium plasma

Safe Direct Synthesis of High Purity H₂O₂ through a H₂/O₂ Plasma Reaction