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The catalytic dehydrogenation of light alkanes over Pt catalysts is generally accepted to follow a reverse Horiuti–Polanyi mechanism. Using a microkinetic analysis in combination with results from ...

The chloroxylenol (PCMX) has shown well virucidal efficacy against COVID-19, but the large-scale utilization of which will undoubtedly pose extra environmental threaten. In the present study, the recycled industrial phenylenediamine residue was used and an integrated strategy of “carbonization-casting-activation” using super low-dose of activator and templates was established to achieve in-situ N/O co-doping and facile synthesis of a kind of hierarchical hyperporous carbons (HHPC). The sample of HHPC-1.25-0.5 obtained with activator and template to residue of 1.25 and 0.5 respectively shows super-high specific surface area of 3602 m2/g and volume of 2.81 cm3/g and demonstrates remarkable adsorption capacity of 1475 mg/g for PCMX in batch and of 1148 mg/g in dynamic column adsorption test. In addition, the HHPC-1.25-0.5 exhibits excellent reusability and tolerance for PCMX adsorption under various ionic backgrounds and real water matrix conditions. The combined physio-chemistry characterization, kinetic study and DFT calculation reveal that the enhanced high performances originate from the hierarchical pore structure and strong electrostatic interaction between PCMX and surface rich pyridinic-N and carbonyl groups.

Both increasing emission of chlorophenol chemicals and plastic waste pollution are severe global environmental challenges, which is worth being explored to respond with a "waste eliminated by waste" coupling treatment strategy. Herein, we propose a one-step recyclable nano-MgO template strategy to prepare in-situ N, O-doped novel porous carbon coral reefs (PCNCR) directly derived from the mixture of real waste PET and melamine formaldehyde resin. The template precursor can be conveniently recycled by facile acetic acid pickling, vacuum evaporation and drying, and the whole preparing process does not involve any toxic solvents, massive consumption of pore-forming agents, or discharge of salty wastewater. The obtained PCNCRs have hierarchical porous structures and abundant N, O-doped species, and the textural parameters can be modulation linearly by varying the mass ratio of magnesium acetate to mixed waste plastics. The optimized PCNCR-1.25 exhibited remarkable adsorption capacity for chlorophenol contaminants (777.5 mg/g for 4-Chloro-3,5-dimethylphenol, PCMX and 538.74 mg/g for 4-Chloro-3-methylphenol, PCMC) in aqueous solution. Adsorption isotherm fitting studies revealed chlorophenol contaminants tended to be rapidly adsorbed on the PCNCR surface in the form of monolayer. And the system reached adsorption equilibrium at about 15 min, which was described by linear driving force model. Reusability test verified that PCNCR-1.25 had excellent adsorption stability for chlorophenol in continuous adsorption-regeneration cycles. DFT calculation illustrated the enhancement of chlorophenol adsorption by heteroatom species, especially nitrogen dopants. This work highlighted a low-cost and sustainable approach to defuse the dual environmental threat of chlorophenol emissions and plastic waste pollution simultaneously.

Both nitrophenol wastewater and aromatic amine industrial waste residue are serious threats to our environment. In this paper, N-rich porous carbons (NPC) derived from industrial aromatic amine waste residue were prepared via a facile “carbonization-activation” one-step approach. Owing to the extremely high activation efficiency of amine residue-NaOH matching strategy, NPC prepared with 1.5 of NaOH-residue ratio obtained an ultra-high specific surface area of 3120 m2/g with a huge pore volume of 2.381 cm3/g. XPS analysis shows that graphitic-N and pyridinic-N are the main N-doped species. The plentiful pore structure, ultra-high surface area, and modification of nitrogen-doped sites rendered the NPCs remarkable adsorption capacity (1030.51 mg/g) for p-nitrophenol (PNP). Adsorption isotherms and adsorption kinetics indicated the adsorption behavior of PNP molecules on NPCs surface adhered to the mechanism of monolayer adsorption and pseudo-second-order kinetic. DFT calculation studies revealed that N-doped species could effectively enhance the adsorption energy of PNP on carbon surface due to the enhanced dispersion and electrostatic attraction. Particularly, the pyridinic-N made an outstanding contribution to improve the interactions through hydrogen bonding. Furthermore, the NPC-1.5 showed an excellent adsorption stability for PNP in the reusability test of 12 cycles, reflecting its great potential in practical application.

Supported vanadium oxides are promising in propane non-oxidative dehydrogenation and the activity of which shows clear support effects. The present study reports the effects of alumina polymorphs on the structure and performances of VOx-based catalysts. VOx/Al2O3 catalysts with the same V surface density were prepared over four different alumina supports (γ-Al2O3, δ-Al2O3, θ-Al2O3, θ,α-Al2O3) obtained by varying the calcination temperature of boehmite. The alumina calcination temperature was shown to affect the surface acid properties and VOx-support interactions and make it possible to tune the activity and coking behavior of catalysts. Weakening the VOx-support interactions due to the change in alumina surface properties was found critical to improve the intrinsic activity of catalysts. The coking behavior of catalysts was shown to depend on both total acid sites and VOx polymerization degree. This study may provide basic principles to tune the performance of VOx-based catalysts for non-oxidative dehydrogenation.

To investigate the role of steam on the structure and activities of platinum-based catalyst, a tin modified Pt/γ-Al2O3 catalyst was prepared for propane dehydrogenation in the presence of steam. The propane conversion could be prominently elevated by nearly twofolds with only 1.0% loss of selectivity to propene when an optimum amount of H2O was added. The retarding effects of steam on the activities are also observed at higher H2O/C3H8 molar ratios (>1). Kinetic studies results show that the apparent activation energies for steam dehydrogenations are lower than those without steam addition. The fresh, spent and steam pretreated catalysts were characterized by TG, Raman, H2-chem, HAADF-STEM, XPS and CO adsorption FT-IR (CO-FTIR). It is observed that the platinum particles sizes are smaller in the samples subjected to certain period of steam pretreatment. The changes of platinum dispersion in steam conditions are related to the changes of tin oxidation states and the segregation of platinum from Pt–Sn alloys, as revealed by CO-FTIR and XPS results. More accessible Pt sites that are generated in the steam due to the phase transformation of Pt–Sn catalyst as well as the removal of coke accumulated on the catalyst surface would account for the increase of catalytic activities and the decrease of activation energies in steam atmosphere. Competitive adsorption of H2O and other reagent over Pt sites would lead to the retarding effects of steam on the activities at high H2O partial pressure.

Catalytic propane dehydrogenation over an alumina supported Pt catalyst in the presence of steam is carried out and it is found that the catalyst activity is increased and the apparent activation energy is lowered due to the presence of steam. Three possible mechanisms, i.e. co-adsorption, Langmuir–Hinshelwood and Eley–Rideal, of changes in energetics and pathways for propane dehydrogenation due to the presence of steam are explored by DFT calculation. The results show that co-adsorption of C3 species with surface oxygenated species would elevate dehydrogenation energy barriers due to repulsive interactions between them. Surface –OH is more active than surface –O in activating the C–H bond in propane and propyl species through either the Langmuir–Hinshelwood or Eley–Rideal mechanism and plays an important role in propane dehydrogenation with steam. The Langmuir–Hinshelwood mechanism is kinetically favorable, in which the activations of the first H in propane by surface −OH are the rate determining steps, but the activation energies are higher than that on a clean Pt(111) surface. The observed enhanced catalyst's activity is ascribed to the lowered coking rates as well as the changes in surface coverage due to the co-adsorption of water and the surface oxygenated species.