Radwa A. El-Salamony

Ni supported high surface area CeO2–ZrO2 catalysts for hydrogen production from ethanol steam reforming

The catalytic activity of nano-sized x%Ni/Ce0.74Zr0.26O2 (x = 0, 2, 10 and 20wt%) catalysts have been investigated to develop highly active catalysts for ethanol steam reforming (ESR) into hydrogen. The structure and surface properties of the catalysts were tested by XRD, TPR, HRTEM and BET surface areas. The effect of reaction temperature from 200 °C to 600 °C was studied in a flow system at atmospheric pressure with an ethanol/water molar ratio of 1 : 8. Selectivity was calculated for the catalytic products H2, CO, CO2 and CH4, as well as the intermediates C2H6, C2H4, C3H8, CH3CHO and CH3COCH3, at different reaction temperatures. It was found that complete conversion of ethanol with considerable amounts of H2 was obtained at 400 °C over all catalysts. H2 was produced at a very low temperature (200 °C) over 10% and 20% Ni loadings, while a maximum H2 selectivity (75%) is reached at 600 °C over the 2%Ni/Ce0.74Zr0.26O2 catalyst; this is most likely due to the small nickel particle size (2–4 nm) in 2%Ni, which results in enhancement of the metal–support interactions. Thermal decomposition of ethanol in an ethanol/water mixture under the same reaction conditions, but in the absence of catalyst, was also studied. HRTEM of the spent catalyst (8 h ESR) shows the deposition of carbon in the form of carbon nanotubes (CNTs).

Highly stable nano Ce–La catalyst for hydrogen production from bio-ethanol

The catalytic activity of a metal free nano particle, whose size ranged from 1–10 nm, was studied according to HRTEM and DLS results. The effect of reaction temperature (300–600 °C) on the catalytic activity of the prepared catalysts was studied in a flow system under atmospheric pressure with an ethanol–water molar ratio of 1 : 10. Selectivity was calculated for the products H2, CO, CO2 and CH4, as well as the intermediates C2H6, C2H4, CH3CHO and CH3COCH3, at different reaction temperatures. It was found that the addition of La increased the activity and stability of the Ce catalyst. H2 was produced at the lowest temperature (300 °C) over Ce–La0.2 & Ce–La0.5 catalysts. Complete conversion of ethanol with high hydrogen selectivity was obtained at 500 °C over Ce–La0.2 catalysts. Further increases of La content lead to decrease in the catalyst activity in accordance with the decrease of surface area to 9.6 m2 g−1. To study the stability of the prepared catalyst, the ESR reactions of Ce–La0.2 and Ce–La1 catalysts were investigated at 500 °C for 15 h. It was found that the Ce–La0.2 catalyst is more stable than the Ce–La1 catalyst over entire 15 h. Finally, we can say that lanthanum oxide (La2O3) is particularly suitable as a modifier due to its effectiveness in the prevention of sintering and improvement of thermal resistance at high temperatures. This oxide is also able to gasify the coke through the formation of La2O2CO3 oxy-carbonate.

Superabsorbent enhanced-catalytic core/shell nanocomposites hydrogels for efficient water decolorization

Spherical polyacrylamide (PAM) nanoparticles were prepared by inverse emulsion polymerization and were found to have an average particle size of 20 nm. In situ inverse emulsion polymerization of acrylamide in the presence of metal oxides nanoparticles (TiO2 and ZnO, either individually or in a mixture) was performed. Transmission electron microscope images clearly confirmed the formation of core/shell nanocomposite structures with inner metal oxide cores coated with a polyacrylamide shell. The composites were further cross-linked to prevent structural deformation in water. The water absorbencies of the prepared composites were 1660, 900, 1000 and 700% for PAM, TiO2/PAM, ZnO/PAM, and TiO2–ZnO/PAM core/shell nanocomposites, respectively. The water decontamination efficiency of the prepared composites was investigated using organic dyes as models of organic contaminants. The decolorization efficiency of the prepared composites was investigated in the dark and under illumination. The nanocomposites showed good ability for photodecolorization, especially the titania nanocomposite, which showed the best ability to photodecolorize Black T and Indigo dyes. A synergetic effect between the adsorption properties of the polymer and the photocatalytic activity of the metal oxides is proposed.

Biomass to fuel gas conversion through a low pyrolysis temperature induced by gamma radiation: an experimental and simulative study

Currently, 80% of global energy is supplied by carbon-based fossil fuels, which has led to concerns over the environmental impact of increasing atmospheric CO2 levels and has sparked ever-growing interest in renewable energy sources. The aim of this study is in line with adding value to low or negative valued biomass feedstocks by converting them into marketable bio-fuel gases, to replace the current one, as a renewable resource for energy via the pyrolysis technology. As a promising thermal conversion method in terms of high reliability, good flexibility through processing and production of versatile range of products pyrolysis is considered to be an important process for the generation of sustainable energy and chemicals from biomass. The pyrolysis process converts biomass carbon-containing materials into a combustible gas, which is primarily composed of carbon monoxide, hydrogen, and methane. However, the literature available over the last few decades have reported that the pyrolysis process should be carried out at elevated temperatures, which is at least 500 °C. The current study is focused on the conversion of some biomass into certain fuel gases at low operational temperatures assisted by γ radiation. First, using raw untreated biomass, gas mixtures composed of different percentages of carbon dioxide and methane were obtained under different operating conditions of time and temperature. In practical, the maximum temperature and time of 300 °C and four hours, respectively, were applied through this conversion process. A complete shift in the produced gas composition towards pure methane (natural gas) was obtained under the same operating conditions via the introduction of gamma ray-treated biomass samples in the pyrolysis system. On the other hand, nano-carbon black particles were obtained as the by-product of the thermal conversion of the irradiated biomass, whereas amorphous structured carbon was obtained when untreated biomass was applied. The gas composition analysis was conducted using a GC instrument equipped with a TC detector and carbon particle characterization was carried out using both HR TEM and Raman spectroscopy.

Enhancement of hydrogen production via hydrogen peroxide as an oxidant

The performance of different Ni/Ce1−xZrxO2 (ss) catalysts of varying composition (x = 0, 0.12, 0.18 and 0.26) were investigated for hydrogen production by ethanol steam reforming (ESR). All catalysts were prepared by co-precipitation method and characterized for their surface area, pore volume, structure and morphology using different techniques (N2-BET, XRD and HRTEM). The Ce4+/Ce3+ redox couple in ceria-containing catalysts is known to be responsible for the OSC of these materials, so, the redox behaviors of these materials were investigated by EPR. Reaction parameters were optimized by varying steam to ethanol molar ratio (6, 8 and 10) in order to produce hydrogen with low carbon monoxide formation as low as possible. The minimum amounts of CO and carbon deposited are observed over Ni/CeZr-8 catalyst at 1:10 ethanol–water ratios. The obtained data are compared with data obtained from oxidative steam reforming of ethanol (OSRE) using hydrogen peroxide as an oxidant. The activity data indicated that hydrogen peroxide is an effective oxidant for OSRE over Ni/Ce1−xZrxO2 catalysts due to its ability to suppress CO formation and increase H2/CO ratio.

Titania modified activated carbon prepared from sugarcane bagasse: adsorption and photocatalytic degradation of methylene blue under visible light irradiation

ABSTRACT Activated carbon (AC), prepared from sugarcane bagasse waste through a low-temperature chemical carbonization treatment, was used as a support for nano-TiO2. TiO2 supported on AC (xTiO2–AC) catalysts (x = 10, 20, 50, and 70 wt.%) were prepared through a mechano-mixing method. The photocatalysts were characterized by Raman, X-ray diffraction analysis, FTIR, SBET, field emission scanning electron microscope, and optical technique. The adsorption and photo-activity of the prepared catalysts (xTiO2–AC) were evaluated using methylene blue (MB) dye. The photocatalytic degradation of MB was evaluated under UVC irradiation and visible light. The degradation percentage of the 100 ppm MB at neutral pH using 20TiO2–AC reaches 96 and 91 after 180 min under visible light and UV irradiation, respectively. In other words, these catalysts are more active under visible light than under UV light irradiation, opening the possibility of using solar light for this application.

Mesoporous waste-extracted SiO2–Al2O3-supported Ni and Ni–H3PW12O40 nano-catalysts for photo-degradation of methyl orange dye under UV irradiation

Rather than looking at wastes as “unwanted materials,” this study considers their potential positive value and explores the production of waste-based catalysts. Herein, mesoporous SiO2–Al2O3 was prepared from both rice husk (source for silica) and waste aluminum foils using isophthalic acid as a textural modifier. X-ray diffraction and BET surface analyses of the as-prepared aluminosilicate demonstrated an amorphous structure with an average pore radius of 5.4 nm. The FTIR spectrum revealed the existence of SiO2–Al2O3 interaction. To produce an efficient photocatalyst, Ni nanoparticles were subsequently loaded onto the aluminosilicate surface by reduction of NiCl2 using hydrazine. Another catalyst, namely Ni–H3PW12O40/aluminosilicate, with strong Bronsted acid sites was also prepared by impregnating the support with an aqueous solution of H3PW12O40. TEM images of the as-prepared materials show that the aluminosilicate particles are slab-like, and the loading of Ni and H3O40PW12 has conserved the morphology of the mesoporous support due to metal–metal interaction. The prepared catalysts were then employed in the purification of water throughout the photocatalytic degradation of methyl orange (MO) dye. The maximum MO adsorption on the surface of the prepared materials was first determined in the absence of UV radiation (dark). The photoactivity of the three materials under the effect of UV irradiation was then detected. The Ni/aluminosilicate catalyst exhibits highest rate of MO removal among the employed materials. A maximum removal of 86% was obtained after an irradiation time of 180 min using the catalyst at a dose of 3 g L−1.

Zn +2 -doped x -Ti–SiO 2 tricomposites for enhancement the photo-catalytic degradation of phenol under UV irradiation

A series of zinc-doped titania–silica tricomposites (Zn/xTi–SiO2) with different Ti-molar ratios were prepared by sol–gel method. Zn+2 ions of 25 wt% were doped on the photo-catalysts using wet impregnation method. The as-synthesized Zn/xTi–SiO2 nano-catalysts were characterized through N2-adsorption–desorption, X-ray diffraction, transmission electron microscope, fourier transform infrared, dynamic light scatterings, photoluminescence, and diffuse reflectance techniques. Photo-catalytic degradation of phenol (PhOH) under 8-W ultraviolet C irradiation was examined. 96% removal was achieved in 150 min by using Zn/20Ti–SiO2. The kinetic study revealed that photo-degradation of PhOH follows pseudo-first order reaction mechanism, where the rate constant was 77.4 × 10−3 min−1. One-way analysis of variance, as well as Student’t-test at α = 0.05 level (95% confidence interval) was performed to comparing the means of the results obtained.Graphical Abstract

Response surface methodology for carbon dioxide reforming of natural gas

ABSTRACT The performance of 0.5% wt Rh/γ-AL2O3 catalyst for the dry reforming of natural gas using carbon dioxide has been studied. The response surface methodology (RSM) is used to study the effect of two different operating parameters, namely the hourly space velocity at the levels 18,000, 36,000, 45,000, and 60,000 ccg−1 h−1 and the reaction temperature at the levels 600, 700, and 800°C, on the conversion of the different components comprising commercial natural gas. The RSM is used to illustrate such effect in the three dimensions and shows the location of the optimum for the conversion or production of each component.

Visible light sensitive activated carbon-metal oxide (TiO2, WO3, NiO, and SnO) nano-catalysts for photo-degradation of methylene blue: a comparative study

Abstract Four composites of metal oxide doped with activated carbon with a metal oxide weight of 20% were prepared using mechano-mixing method. The nano-catalysts were characterized by N2-adsorption–desorption, X-ray diffraction analysis, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV-diffuse reflectance, and photoluminescence spectroscopy. Photo-catalytic degradation of methylene blue dye under UV 254  nm and visible light was examined. In general, prepared catalysts are more active for degradation of dye under visible light than UV, reaching 96% within 180 min irradiation using the SnO catalyst. Photo-degradation of methylene blue followed pseudo first order reaction mechanism with a rate constant of 14.8 × 10−3 min−1, and the time required for removal of 50% of dye was 47 min.