Steam-assisted crystallized Fe-ZSM-5 materials and their unprecedented activity in benzene hydroxylation to phenol using hydrogen peroxide

Polyethylene upcycling to aromatics by pulse pressurized catalytic pyrolysis

To address the challenging issues of waste plastic pollution and petroleum shortage, we report herein a pulse pressurized catalytic pyrolysis process where polyethylene is continuously converted into aromatics using HZSM-5 catalyst incorporated with hydrated SiO2. Pressurization improves the activity of single-pulse pyrolysis of polyethylene by 14.42%. In contrast to the linear decrease of BTEXS relative yield with a K value of - 0.23 under non-pressurized conditions, pressurization results in a notable stability in the latter stage, characterized by a K value of only - 0.063. Comprehensive catalyst characterization demonstrates that pressurization promotes the release of water from hydrated SiO2, enabling HZSM-5 to effectively undergo dealumination and obtain suitable acidity and pore structure, and ultimately enhancing the resistance to carbon deposition. In summary, pressurization improves both pyrolysis activity and catalysis stability, offering a promising strategy for the high-value utilization of waste plastics.

Highly selective oxidation of benzene to phenol with air at room temperature promoted by water

Phenol is one of the most important fine chemical intermediates in the synthesis of plastics and drugs with a market size of ca. $30b¹ and the commercial production is via a two-step selective oxidation of benzene, requiring high energy input (high temperature and high pressure) in the presence of a corrosive acidic medium, and causing serious environmental issues^2-5. Here we present a four-phase interface strategy with well-designed Pd@Cu nanoarchitecture decorated TiO₂ as a catalyst in a suspension system. The optimised catalyst leads to a turnover number of 16,000-100,000 for phenol generation with respect to the active sites and an excellent selectivity of ca. 93%. Such unprecedented results are attributed to the efficient activation of benzene by the atomically Cu coated Pd nanoarchitecture, enhanced charge separation, and an oxidant-lean environment. The rational design of catalyst and reaction system provides a green pathway for the selective conversion of symmetric organic molecules.

Novel catalysts with multivalence copper for organic pollutants removal from wastewater with excellent selectivity and stability in Fenton-like process under neutral pH conditions

Fenton-like reaction has been widely used for organics degradation. However, most Fenton-like reaction works at low pH range (pH < 4) with uncontrollable selectivity of hydroxyl radicals from H₂ O₂ activation, and unsatisfied catalyst stability, which is compromised advanced oxidation performance for water/wastewater treatments. In this work, to solve the drawbacks, novel copper catalysts were fabricated via hydrogen reduction/calcination of Cu²⁺ -supported Al/MCM-41 with precisely controllable copper valence state. Compared with catalysts with monovalence copper (i.e., CuO, Cu, and Cu²⁺ ), the obtained catalysts with multivalence copper present higher selectivity, excellent stability towards •OH radical pathways, and outperformance in pCBA degradation efficiency at neutral state. In addition, the fabricated catalysts also exhibited excellent phenol removal efficiency (75.5%) and H₂ O₂ utilization efficiency (47.9%) within neutral environment. Moreover, the degradation efficiency of phenol approaches to 100% within only 2 h. The catalyst also shows good stability for organic pollutants removal, which shows good potential in catalytic oxidation for phenolic compounds-containing wastewater in Fenton-like reaction, especially under neutral pH conditions. PRACTITIONER POINTS: Multivalence copper presents great potentials for organic compounds removal at neutral condition. Multivalence copper shows higher selectivity toward •OH and good stability at neutral condition. Multivalence copper exhibiters outperformed phenol removal efficiency at neutral condition.

Lignin-to-chemicals: Application of catalytic hydrogenolysis of lignin to produce phenols and terephthalic acid via metal-based catalysts

Lignin is the only renewable aromatic material in nature and contains a large number of oxygen-containing functional groups. High-value and green utilization of "lignin-to-chemicals" can be realized via using lignin to produce fine chemicals such as phenols and carboxylic acids, which can not only reduce the waste of lignin in the process of lignocellulosic biomass treatment, but gradually make the substitution of traditional fossil fuels come true. The hydrogenolysis process under catalysis of metal catalyst has high product selectivity and less impurity, which is suitable for the production of same type or single fine chemicals. Hydrogenolysis of lignin via metal catalysts to produce lignin oil, and further modification of functional groups (e.g. methoxyl, alkyl and hydroxyl group) of depolymerized monomers in the bio-oil to yeild phenols and terephthalic acid are reviewed, and catalytic mechanisms are briefly summarized in this paper. Finally, the problems of lignin catalytic conversion existing currently are investigated, and the future development of this field is also prospected.

N2O Decomposition over Fe-ZSM-5: A Systematic Study in the Generation of Active Sites

We have carried out a systematic investigation of the critical activation parameters (i.e., final temperature (673–1273 K), atmosphere (He vs. O₂/He), and final isothermal hold (1 min–15 h) on the generation of “α-sites”, responsible for the direct N₂O decomposition over Fe-ZSM-5 (Fe content = 1200–2300 ppm). The concentration of α-sites was determined by (ia) transient response of N₂O and (ib) CO at 523 K, and (ii) temperature programmed desorption (TPD) following nitrous oxide decomposition. Transient response analysis was consistent with decomposition of N₂O to generate (i) “active” α-oxygen that participates in the low-temperature CO→CO₂ oxidation and (ii) “non-active” oxygen strongly adsorbed that is not released during TPD. For the first time, we were able to quantify the formation of α-sites, which requires a high temperature (>973) treatment of Fe-ZSM-5 in He over a short period of time (<1 h). In contrast, prolonged high temperature treatment (1273 K) and the presence of O₂ in the feed irreversibly reduced the amount of active sites.

Efficient Conversion of Pine Wood Lignin to Phenol

Obtaining chemical building blocks from biomass is attractive for meeting sustainability targets. Herein, an effective approach was developed to convert the lignin part of woody biomass into phenol, which is a valuable base chemical. Monomeric alkylmethoxyphenols were obtained from pinewood, rich in guaiacol-type lignin, through Pt/C-catalyzed reductive depolymerization. In a second step, an optimized MoP/SiO2 catalyst was used to selectively remove methoxy groups in these lignin monomers to generate 4-alkylphenols, which were then dealkylated by zeolite-catalyzed transalkylation to a benzene stream. The overall yield of phenol based on the initial lignin content in pinewood was 9.6 mol %.

A new iron-based metal-organic framework with enhancing catalysis activity for benzene hydroxylation

A new Fe-based metal-organic framework (MOF), termed Fe-TBAPy Fe2(OH)2(TBAPy)·4.4H2O, was solvothermally synthesized. Structural analysis revealed that Fe-TBAPy is built from [Fe(OH)(CO2)2]∞ rod-shaped SBUs (SBUs = secondary building units) and 1,3,6,8-tetrakis(p-benzoate)pyrene (TBAPy4-) linker to form the frz topological structure highlighted by 7 Å channels and 3.4 Å narrow pores sandwiching between the pyrene cores of TBAPy4-. Consequently, Fe-TBAPy was used as a recyclable heterogeneous catalyst for benzene hydroxylation. Remarkably, the catalysis reaction resulted in high phenol yield and selectivity of 64.5% and 92.9%, respectively, which are higher than that of the other Fe-based MOFs and comparable with those of the best-performing heterogeneous catalysts for benzene hydroxylation. This finding demonstrated the potential for the design of MOFs with enhancing catalysis activity for benzene hydroxylation.

Amorphous Cr-doped g-C3N4 as an efficient catalyst for the direct hydroxylation of benzene to phenol

The intrinsic correlations between catalyst structure and catalytic performance at different calcination temperatures were studied.

Zeolite acidity strongly influences hydrogen peroxide activation and oxygenate selectivity in the partial oxidation of methane over M,Fe-MFI (M: Ga, Al, B) zeolites

Brönsted acidity plays a crucial role in the partial oxidation of methane to oxygenated products.