Paper-like Sintered Stainless Steel Fibers Research Articles

Preparation of microfiber composite nitrogen doped carbon nanotube membranes and their degradation properties of phenol in the structured fixed bed

Microfiber composite nitrogen doped carbon nanotube membranes (NCNT/PSSF) were prepared by chemical vapor deposition on paper-like sintered stainless steel fibers (PSSF) using both camphor and melamine as precursors. FE-SEM, TEM, Raman, TG and other characterization methods were employed to investigate the influence of synthesis temperature, carrier gas flow rate and the ratio of precursors on the performance of NCNT/PSSF, respectively. Besides, the metal composition encapsulated in the NCNT tube was analyzed by XRD, XPS and HR-TEM. The pretreatment of PSSF promoted the migration of Fe and Cr to the stainless steel surface and reduced the particle size of the catalyst. Fe, as the only catalyst form, drove the growth of NCNT and was transformed into Fe3C after the reaction. Subsequently, the performance of NCNT/PSSF as a metal free catalyst for activating PMS (peroxymonosulfonate) to degrade phenol was evaluated on a structured fixed bed. The results revealed that about 85 % and 50 % of the phenol was transformed and mineralized during the first few hours of the reaction. Non-mineralized organic aromatic compounds included catechol, hydroquinone and p-benzoquinone. The concentration difference between the intermediate and the remaining total organic carbon represented some refractory open-loop carboxylic acids. Finally, the satisfactory results of the removal of phenol by NCNT/PSSF in actual water highlight its advantages in continuous treatment. Nonmetallic nitrogen doping not only provided a creative strategy for the development of nanocarbon materials, but also afforded an excellent catalyst to assist advanced oxidation techniques for the continuous removal of phenols from wastewater.

Kinetics study of CWPO of phenol wastewater over Cu‐ZSM‐5/PSSF catalysts prepared by ion‐exchanged method

AbstractBACKGROUNDCu‐ZSM‐5 was prepared on paper‐like sintered stainless steel fibers (PSSF) by ion‐exchange method for the catalytic wet peroxide oxidation (CWPO) of phenol in a fixed bed reactor. The prepared Cu‐ZSM‐5/PSSF catalyst was characterized by scanning electron microscope (SEM), Brunner−Emmet−Teller (BET), X‐ray diffraction (XRD), Fourier Transform InfraRed (FT‐IR), Ultraviolet–visiblespectroscopy (UV–vis) and X‐ray photoelectron spectroscopy (XPS).RESULTSThe XRD results showed that the ZSM‐5 membrane was loaded well over PSSF with good crystallinity, even after the process of ion‐exchange. The UV–vis inferred that isolated copper was the predominant species over ZSM‐5 pores of the catalyst. Then, the effects of different catalyst bed heights, reaction temperatures, and feed flow rates on catalytic performance were investigated to obtain optimum reaction conditions.CONCLUSIONSFinally, the catalytic reaction kinetics analysis over Cu‐ZSM‐5/PSSF catalyst were carried out with the Power‐rate Law Kinetic model. The experimental results showed that the reaction order was the first‐order reaction, and the activation energy of the oxidation reaction was Ea = 72.9 kJ/mol. The initial oxidation rate equation (−rA0 = 5.36 × 108 e−72 994/RT CA) was obtained for phenol degradation using Cu‐ZSM‐5/PSSF catalyst. © 2022 Society of Chemical Industry (SCI).

Preparation of structured N-CNTs/PSSF composite catalyst to activate peroxymonosulfate for phenol degradation

Four different types of structured nitrogen-doped carbon nanotube membranes (C50, NC25, NC50, N25C25) were used as metal-free catalysts for phenol degradation. Firstly, nitrogen-doped carbon nanotubes were prepared on paper-like sintered stainless steel fibers (PSSF) by chemical vapor deposition using melamine and acetylene as dual precursors, then the nitric acid was used to remove amorphous carbon and catalyst particles in the tubes. Subsequently, TEM, XPS, N2 adsorption and desorption and other characterization techniques were used to investigate the structure and morphology of the catalysts. Characterization results showed that the use of dual precursor could well adjust the nitrogen content in carbon nanotubes, and nitrogen doping could change the hollow structure of carbon nanotubes into rough bamboo-like and corrugated structure. Meanwhile, acid treatment significantly increased the specific surface area, among which the value of HN25C25 reached 38.15 m2/g. Pristine and acid-treated catalysts were then used to activate peroxymonosulfonate (PMS) in a structured fixed bed reactor. NC25 and N25C25 were able to mineralize 46% and 17.5% of phenol at 1 h, but the TOC conversion rate only maintained at about 10% in the subsequent reaction time. After acid treatment, HNC25 and HN25C25 were able to mineralize up to 76% and 84% of phenol, and the TOC conversion rate maintained at about 70% within 7 h. the high leaching of Fe in the acid-treated catalysts could be attributed to the formation of small carboxylic acids and the destruction of the PSSF support during the reaction. At last, radical inhibition experiments and ESR spectra showed that sulfate radicals and hydroxyl radicals were the main active species in the reaction. The increase in the proportion of active nitrogen species and the improvement in contact efficiency could explain the higher mineralization efficiency of phenol catalyst after acid treatment.

Highly efficient nitrogen-doped carbon nanotubes coated on paper-like sintered stainless steel fibers as metal-free structured catalyst for phenol degradation

Three types of carbon nanotubes coated on paper-like sintered stainless steel fibers (PSSF) were synthesized and applied for continuous catalytic wet hydrogen peroxide oxidation (CWPO) of phenol. The novel metal-free nitrogen-doped carbon nanotube-coated PSSF catalyst (N-CNTs/PSSF) was designed by direct chemical vapor deposition using melamine as solid precursor for the first time, and CNTs/PSSF and Fe2O3-deposited CNTs/PSSF (Fe-CNTs/PSSF) catalysts were synthesized for comparison. Characterization results showed that all the catalysts exhibited three-dimensional networks structure, with nanotubes wrapping on the stainless steel fibers successfully, and the N-CNTs showed distinct irregular corrugated morphology with nitrogen-doping level about 5.18 at.%. CWPO of phenol revealed that the N-CNTs/PSSF catalyst achieved favorable catalytic activity and highest stability during 100-h reaction (phenol and TOC conversions reached about 90% and 50%, respectively), while phenol conversions of CNTs/PSSF and Fe-CNTs/PSSF catalysts decreased over time to 72% and 58%, respectively. The N-CNTs/PSSF catalyst also showed the lowest Fe weight loss ratio (about 2.44 wt%) among the three catalysts. The favorable catalytic results of N-CNTs/PSSF can be ascribed to the synergistic effects of the strong affinity toward polar molecules of N-CNTs, as well as the enhancement in contact efficiency associated with three-dimensional networks structure of the PSSF.

Preparation of novel catalyst-free Fe3C nanocrystals encapsulated NCNT structured catalyst for continuous catalytic wet peroxide oxidation of phenol

Novel nitrogen-doped carbon nanotubes encapsulating Fe3C nanocrystals coated paper-like sintered stainless steel fibers (PSSF) structured catalyst (Fe3C@NCNT/PSSF) was designed for continuous catalytic wet peroxide oxidation of phenol. Firstly, Fe3C@NCNT/PSSF was fabricated by directly growing the Fe3C encapsulated NCNTs onto the three-dimensional PSSF substrate through CVD method using melamine as precursor, the monolithic PSSF substrate served as a self-catalyzing agent for catalyst preparation. Secondly, the surface morphology and structure of Fe3C@NCNT/PSSF were investigated to optimize the synthesis condition. Then Fe3C@NCNT/PSSF was employed as a structured catalyst for continuous CWPO of phenol, effect of operating conditions was studied. Catalytic results showed that the encapsulated Fe3C nanoparticles significantly enhanced the degradation efficiency of phenol, and catalytic performance was improved with the increase of temperature. However, catalytic performance appeared unusual when residence time was considered, due to the effect of strongly polar surface of NCNTs on the contact efficiency between pollutants and hydroxyl radicals. Reusability experiments showed that catalytic performance of catalyst was improved with the increase of reusability cycles although the iron leaching concentration decreased, attributing to enhanced reaction within internal channel of Fe3C@NCNT. The fourth reaction run achieved a stable phenol conversion of 90%, TOC conversion around 41% under optimized conditions.

Graphene as efficient and robust catalysts for catalytic wet peroxide oxidation of phenol in a continuous fixed-bed reactor

Monolayer graphene film (Gr) as a metal-free catalyst was synthesized on the paper-like sintered stainless steel fibers (PSSF) with three-dimensional net structure by chemical vapor deposition (CVD) technique. The prepared PSSF-Gr was characterized by SEM, EDS, XRD, AFM, TEM, and Raman spectroscopy. Then, the optimum reaction conditions for catalytic wet peroxide oxidation (CWPO) of phenol in a continuous reactor using PSSF-Gr catalysts were explored by analyzing the effects of reaction temperature, feed flow rate, and catalyst bed height on catalytic performance. Moreover, the long-term stability of PSSF-Gr catalyst was investigated and demonstrated complete phenol oxidation and dramatic TOC removal (values ranging between 80.7% and 91.0%) after continuously operating for 72 h under optimum condition. Finally, a reasonable reaction mechanism for CWPO of phenol was proposed by analyzing the HPLC results and evolution of aromatic intermediates content. From these results, seldom toxic aromatic intermediates were observed on account of the production of short-chain organic acids by opening of aromatic ring, which subsequently mineralized to CO2 and H2O. The simple preparation method, unique structure, extraordinary catalytic activity and stability of the graphene-based material would provide a new potential catalyst for environmental catalysis.

Synthesis of graphene with different layers on paper-like sintered stainless steel fibers and its application as a metal-free catalyst for catalytic wet peroxide oxidation of phenol

Different layers of graphene (Gr) films are prepared on the paper-like sintered stainless steel fibers (PSSF) support with three-dimensional structure by CVD method. The effects of acetylene flow rate, deposition time, and deposition temperature on the properties of PSSF-Gr are investigated by EDS, AFM, SEM, TEM, and Raman spectroscopy, respectively. Then, the catalytic performances of PSSF-Gr with different layers of Gr films as metal-free catalysts for catalytic wet peroxide oxidation (CWPO) of phenol are assessed in the continuous fixed-bed reactor. The catalytic results demonstrate that the PSSF-Gr catalyst with single layer graphene film achieves the best catalytic performance (phenol and TOC removal efficiency reach 99% and 73%, respectively) after continuously operating for 6 h. Under the treatment of the PSSF-Gr catalyst with single-layer graphene, total phenol oxidation and excellent TOC removal (maintain about 71%) have been achieved for the long-term operation (38 h). Moreover, the phenol conversion of blank experiment (without catalyst) and PSSF are around 40%, which are caused by thermal degradation and thus, the excellent catalytic activity of PSSF-Gr is ascribed to graphene. Like other Fenton’s catalysts, the catalytic mechanism of PSSF-Gr catalyst in phenol degradation is also a ·OH mechanism.

Catalytic combustion of isopropanol over Co-Mn mixed oxides modified ZSM-5 zeolite membrane catalysts coated on stainless steel fibers

Abstract A novel gradient porous Co-Mn mixed oxides modified ZSM-5 zeolite membrane/PSSF (paper-like stainless steel fibers) catalyst was prepared for catalytic combustion of isopropanol in a membrane reactor. First, the paper-like sintered stainless steel fibers (PSSF) support was fabricated by wet lay-up papermaking method and sintering process. Then, ZSM-5 zeolite membranes were synthesized on the surface of stainless steel fibers by using secondary growth process. Finally, the cobalt and manganese mixed oxides modified ZSM-5 zeolite membrane catalysts were prepared by wet impregnation method. These novel modified membrane catalysts were characterized by using SEM, XRD, N2 adsorption–desorption isotherms and XPS, respectively. The catalytic activity test was carried out over a membrane reactor filled with ZSM-5 zeolite membrane catalysts and granular catalysts, respectively. The experimental results showed that the junctures of stainless steel fibers were completely sintered together to form a three-dimensional network structure and ZSM-5 zeolite membrane was fabricated on the PSSF support with the thickness of 1.78 μm. The cobalt element existed as Co3+and Co2+, maganese element existed as Mn4+ and Mn3+. The results of catalytic activity tests showed that catalytic activity for isopropanol over ZSM-5 zeolite membrane catalyst was superior to that over granular ZMS-5 catalyst, the reaction temperature of 50% and 90% conversion of isopropanol over ZSM-5 zeolite membrane catalyst dramatically decreased. The Co-Mn(1:4)/ZSM-5/PSSF catalysts presented the most excellent catalytic activity for isopropanol combustion, compared with Co/ZSM-5/PSSF and Mn/ZSM-5/PSSF catalysts, respectively.

Catalytic combustion kinetics of isopropanol over novel porous microfibrous‐structured ZSM‐5 coating/PSSF catalyst

Porous thin‐sheet cobalt–copper–manganese mixed oxides modified microfibrous‐structured ZSM‐5 coating/PSSF catalysts were developed by the papermaking/sintering process, secondary growth process, and incipient wetness impregnating method. Paper‐like sintered stainless steel fibers (PSSF) support with sinter‐locked three‐dimensional networks was built by the papermaking/sintering process, and ZSM‐5 coatings were fabricated on the surface of stainless steel fibers by the secondary growth process. Catalytic combustion performances of isopropanol at different concentrations over the microfibrous‐structured Co–Cu–Mn (1:1:1)/ZSM‐5 coating/PSSF catalysts were measured to obtain kinetics data. The catalytic combustion kinetics was investigated using power–rate law model and Mars–Van Krevelen model. It was found that the Mars–Van Krevelen model provided fairly good fits to the kinetic data. The catalytic combustion reaction occurred by interaction between isopropanol molecule and oxygen‐rich centers of modified microfibrous‐structured ZSM‐5 coating/PSSF catalyst. The reaction activation energies for the reduction and oxidation steps are 60.3 and 57.19 kJ/mol, respectively. © 2014 American Institute of Chemical Engineers AIChE J, 61: 620–630, 2015

Preparation of novel Fe-ZSM-5 zeolite membrane catalysts for catalytic wet peroxide oxidation of phenol in a membrane reactor

Abstract Novel Fe-ZSM-5 zeolite membrane catalysts were prepared for catalytic wet peroxide oxidation (CWPO) of phenol in a membrane reactor. Firstly, the ZSM-5 zeolite membrane with a Si/Al ratio of 80 was fabricated by using secondary growth process on the surfaces of paper-like sintered stainless steel fibers (PSSFs) which was prepared by wet lay-up papermaking process and sintering process. Then, Fe-ZSM-5 zeolite membrane catalysts with Fe loading of 15%, 25% and 35% were prepared and systematically characterized by using X-ray diffraction (XRD), N2 adsorption–desorption, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectra (XPS), respectively. Finally, catalytic activity of Fe-ZSM-5 zeolite membrane catalysts was evaluated by investigating the conversion of phenol, H2O2 and TOC as well as the Fe leaching concentration in the treated effluent based on the CWPO processes in a membrane reactor. The characterization results showed that ZSM-5 zeolite membrane with a thickness of 6 μm was fabricated on the surface of PSSFs and Fe element with a form of Fe2O3 was uniformly dispersed on the surface of ZSM-5 zeolite membrane support. The results of CWPO of phenol showed that the catalyst with Fe loading around 25% achieved the highest activity (phenol conversion about 95% and TOC conversion about 45%, respectively) after continuously ran for 7 h. Meanwhile, low loss of Fe species was observed on all of the catalysts (Fe leaching concentration lower than 7 mg/L).

Fabrication of porous copper/manganese binary oxides modified ZSM-5 membrane catalyst and potential application in the removal of VOCs

Abstract Copper-manganese binary oxides modified ZSM-5 membrane catalysts were synthesized by using incipient wetness impregnating method. Specifically, the PSSF (paper-like sintered stainless steel fibers) support was fabricated by wet lay-up papermaking/sintering process and the ZSM-5 membranes were synthesized on the surface of stainless steel fibers by using secondary growth process. The catalysts were characterized by using scanning electron microscopy (SEM), Energy dispersive X-ray spectrometer (EDS) mapping, X-ray diffraction (XRD), N 2 adsorption–desorption, X-ray photoelectron spectra (XPS) as well as H 2 -TPR (Temperature programmed reduction). The most efficient catalyst was Cu–Mn(1:6)/ZSM-5/PSSF, exhibiting best catalytic activity (% of isopropanol conversion was 210 °C) and excellent reaction rate. It can be also demonstrated that the zeolite membrane reactor performs better for isopropanol oxidation, giving a T 90% that is around 70 °C lower than obtained in the traditional particles fixed bed. The excellent catalytic performance of the Cu–Mn(1:6)/ZSM-5/PSSF catalysts can be attributed to the presence of ZSM-5 zeolite membrane, well dispersion of catalysts actives, reasonable mass/heat transfer efficiency, excellent oxygen storage ability as well as higher contacting efficiency. Furthermore, the Cu–Mn(1:6)/ZSM-5/PSSF catalyst exhibits a high stability after being used at 260 °C for 50 h.

Gradient porous Co–Cu–Mn mixed oxides modified ZSM-5 membranes as high efficiency catalyst for the catalytic oxidation of isopropanol

Novel gradient porous mixed cobalt–copper–manganese mixed oxides modified ZSM-5 membrane catalysts were synthesized by the incipient wetness impregnating method. The paper-like sintered stainless steel fibers (PSSF) support was fabricated by the wet lay-up papermaking/sintering process, and the ZSM-5 membranes were synthesized on the surface of stainless steel fibers by using secondary growth process. These novel modified membrane catalysts have been characterized by a series of techniques including SEM, EDS mapping, XRD, N2 adsorption–desorption, XPS and H2-TPR method. Catalytic performances of isopropanol oxidation over these novel catalysts were investigated. Among the series of catalysts, the as-prepared Co–Cu–Mn (1:1:1)/ZSM-5/PSSF catalysts have exhibited the best catalytic activity, demonstrating by a lowest T90% at 210°C. The gradient porous modified ZSM-5 membrane as high efficiency catalyst can offer a much higher catalytic activity, excellent reaction stability, and higher contact efficiency.

Preparation and characterization of a novel gradient porous ZSM-5 zeolite membrane/PSSF composite and its application for toluene adsorption

A novel gradient porous ZSM-5 membrane/PSSF composite was prepared by the wet lay-up papermaking process and secondary growth process. Firstly, the paper-like sintered stainless steel fibers (PSSFs) support was prepared by the wet lay-up papermaking process and sintering process, then a ZSM-5 membrane was fabricated on this PSSF support by secondary growth process. The morphology and structure of ZSM-5 membrane/PSSF composite were characterized by SEM, XRD and ASAP 2020, respectively. The experimental results indicated that the junctures of stainless steel fibers were completely sintered together to form a three-dimensional network structure and ZSM-5 membrane was fabricated on the PSSF support. The specific surface area of composite was 145.1m2/g, which was calculated with the BET (Brunauer–Emmett–Teller) method, and the total pore volume was 0.1547cm3/g. The adsorption breakthrough curve of toluene in the structured fixed bed filled with both granular activated carbons (GACs) of 2.4cm in the inlet of bed and NaZSM-5/PSSF composites of 0.6cm in the outlet of bed was also investigated, comparing with that in individual GAC fixed bed with bed height of 3cm. The length of unused bed was calculated according to the breakthrough curve data. The experimental results showed that the length of unused bed in structured fixed bed was obviously decreased.