Synthesis of ascorbic acid enhanced TiO2 photocatalyst: its characterization and catalytic activity in CO2 photoreduction

To date, the development of solar environmental remediation has shifted more emphasis on the green and simple synthesis of catalyst for CO2 photocatalysis process. Herein, TiO2 photocatalyst was successfully synthesized via hydrothermal method. The effects of the different molar ratio of ascorbic acid C6H8O6, (AA) added during the preparation of TiO2 nanoparticles were comprehensively studied. The characterization of TiO2 nanocrystals was performed via XRD, XPS, DRUV-vis, and FTIR. The results show the AA loading into TiO2 nanoparticles significantly intensified the XRD spectra of anatase structure. In fact, this feature had signified a reactivity of the photocatalyst in the visible region. In an instance, BET surface area was also enhanced with the highest recorded value of 135.14 m2/g for 0.8AA. Meanwhile, the CO2 photoreduction over synthesized TiO2 had produced the highest amount of HCOOH at 39.3 μmol/g cat for 0.8AA within 6 hours of reaction time. Furthermore, the DRUV-vis analysis had illustrated better light absorption ability of 0.8AA. This profound finding is attributed to the correlation between large surface area, pure anatase phase, and high adsorbed water molecules. Therefore, this study had significantly demonstrated the potential of modified TiO2 with AA in CO2 photocatalysis area while simultaneously presents a green and simple method for TiO2 synthesis

Mechanism And Rate Limiting Step For The Catalytic Decomposition Of Methane To Hydrogen And Carbon Nanotube.

The main focus of this paper is to report a mechanism, a rate-limiting step, and a rate law consistent with experimental observation for the decomposition of methane to hydrogen and carbon nanotube over Ni/Mn based catalyst

Correlation between Fischer-Tropsch catalytic activity and composition of catalysts

This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on alumina. The catalysts were prepared by a wet impregnation method. Samples were characterized using temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), CO-chemisorption, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM-EDX) and N2-adsorption analysis. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H2/CO = 2 v/v and space velocity, SV = 12L/g.h. The physicochemical properties and the FTS activity of the bimetallic catalysts were analyzed and compared with those of monometallic cobalt and iron catalysts at similar operating conditions

Co-Production of Methanol and Methyl Formate via Catalytic Hydrogenation of CO₂ over Promoted Cu/ZnO Catalyst Supported on Al₂O₃ and SBA-15

Cu/ZnO catalysts promoted with Mn, Nb and Zr, in a 1:1:1 ration, and supported on Al2O3 (CZMNZA) and SBA-15 (CZMNZS) were synthesized using an impregnation method. The catalytic performance of methanol synthesis from CO2 hydrogenation was investigated in a fixed-bed reactor at 250 °C, 22.5 bar, GHSV 10,800 mL/g·h and H2/CO2 ratio of 3. The CZMNZA catalyst resulted in higher CO2 conversion and MeOH selectivity of 7.22% and 32.10%, respectively, despite having a lower BET surface area and pore volume compared to CZMNZS. Methyl formate is the major product obtained over both types of catalysts. The CZMNZA is a promising catalyst for co-producing methanol and methyl formate via the CO2 hydrogenation reaction

Effect of the support on physicochemical properties and catalytic performance of cobalt based nano-catalysts in Fischer-Tropsch reaction

In this paper, comparative investigations of the effects of CNTs and ?-Al2O3 on the physicochemical properties and catalytic performances of Co based nano-catalyst during FTS have been presented. Catalysts were prepared via a wet impregnation method and characterized by various analytical techniques such as transmission electron microscopy (TEM), temperature programmed reduction (H2-TPR), carbon dioxide temperature programmed desorption (CO2-TPD) and X-ray photoelectron spectroscopy (XPS). Fischer-Tropsch reaction (FTS) was carried out in a fixed-bed microreactor (220 �C and 1 atm and with H2/CO = 2 v/v, SV of 12 L/g h). Various characterization techniques revealed that Co nanocatalysts supported on CNTs and Al2O3 were different in physicochemical properties. There was a stronger interaction between Co and Al2O3 support compared to that of CNTs support. CNTs support increased the reducibility, dispersion, active metal surface area and decreased Co particle size. A significant increase in% CO conversion and FTS reaction rate was also observed over CNTs support compared to that of Co/Al2O3. Co/CNTs resulted in higher C5+ hydrocarbons selectivity compared to that of Co/Al2O3 catalyst.The authors acknowledged financial support provided by Ministry of Science, Technology and Innovation (E-Science Fund No: 03-02-02-SF0036), FRGS grant (project No: (FRGS/1/2012/SG01/UTP/02/01) and Short Term Internal Fund Universiti Teknologi PETRONAS (Project No.31/09.10) and Gas Processing Centre, College of engineering, Qatar University, Qatar.Scopu

Effects of Promoter’s Composition on the Physicochemical Properties of Cu/ZnO/Al₂O₃-ZrO₂ Catalyst

Cu/ZnO catalysts were synthesized via an impregnation method on an Al2O3-ZrO2 support and modified by the addition of manganese and niobium as promoters. The effect of the selected promoters on the physicochemical properties and performance toward the hydrogenation of CO2 to methanol are presented in this paper. The Mn and Nb promoters improved the reducibility of the catalyst as evidenced by the shifting of the H2-TPR peaks from 315 °C for the un-promoted catalyst to 284 °C for the Mn- and Nb-promoted catalyst. The catalytic performance in a CO2 hydrogenation reaction was evaluated in a fixed-bed reactor system at 22.5 bar and 250 °C for 5 h. Amongst the catalysts investigated, the catalyst with equal ratio of Mn and Nb promoters exhibited the smallest particle size of 6.7 nm and highest amount of medium-strength basic sites (87 µmol/g), which resulted in the highest CO2 conversion (15.9%) and methanol selectivity (68.8%)

Effect of pH, Acid and Thermal Treatment Conditions on Co/CNT Catalyst Performance in Fischer–Tropsch Reaction

Multiwalled carbon nanotubes (CNT) supported cobalt oxide was prepared as a catalyst by strong electrostatic adsorption (SEA) method. The CNT support was initially acid- and thermal-treated in order to functionalize the support to uptake more Co clusters. The Co/CNT were characterized by a range of analytical methods including transmission electron microscopy (TEM), temperature programmed reduction with hydrogen (H2-TPR), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic absorption spectroscopy (AAS), Zeta sizer particle size analysis and Brunauer-Emmett-Teller (BET) surface area analysis. TEM images showed cobalt particles were highly dispersed and impregnated at both exterior and interior walls of the CNT support with a narrow particle size distribution of 6-8 nm. In addition, the performance of the synthesized Co/CNT catalyst was tested using Fischer-Tropsch synthesis (FTS) reaction which was carried out in a fixed-bed micro-reactor. H2-TPR profiles indicated the lower reduction temperature of 420 °C was required for the FTS reaction. The study revealed that cobalt is an effective metal for Co/CNT catalysts at pH 14 and at 900 °C calcination temperature. Furthermore, FTS reaction results showed that CO conversion and C5+ selectivity were recorded at 58.7% and 83.2% respectively, which were higher than those obtained using a Co/CNT catalyst which pre-treated at a lower thermal treatment temperature and pH. © 2019 by the authors

Effects of Cobalt Loading, Particle Size, and Calcination Condition on Co/CNT Catalyst Performance in Fischer–Tropsch Reactions

The strong electrostatic adsorption (SEA) method was applied to the synthesis of a cobalt (Co) catalyst on a multi-walled carbon nanotube (CNT) support. In order to uptake more of the cobalt cluster with higher dispersion, the CNT was functionalized via acid and thermal treatment. The Co/CNT catalyst samples were characterized by a range of methods including the Brunauer–Emmet–Teller (BET) surface area analyzer, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis, atomic absorption spectroscopy (AAS), and H2-temperature programmed reduction (H2-TPR) analysis. The data from the TEM images revealed that the catalyst was highly dispersed over the external and internal walls of the CNT and that it demonstrated a narrow particle size of 6–8 nm. In addition, the data from the H2-TPR studies showed a lower reduction temperature (420 °C) for the pre-treated catalyst samples. Furthermore, a Fischer–Tropsch synthesis (FTS) reaction was chosen to evaluate the Co/CNT catalyst performance by using a fixed-bed microreactor at different parameters. Finally finding the optimum value of the cobalt loading percentage, particle size, and calcination conditions of Co/CNT catalyst resulted in a CO conversion and C5+ selectivity of 58.7% and 83.2%, respectively