SCR of NO with C3H6 in the presence of excess O2 over Cu/Ag/CeO2-ZrO2 catalyst

The catalytic activity of a series of CeO2-ZrO2 mixed oxides in the selective catalytic reduction (SCR) of NO by C3H6 at 400'C has been investigated. The NO reduction activity of pure CeO2 is enhanced in the presence of Zr, reaching a maximum NO conversion with CeO2(75)-ZrO2(25) catalyst. Then, the catalytic performances of Cu(4)/Ag(1)/CeO2 and Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalysts were compared and the latter showed better activity especially in the low temperature region (250-350 C). The stronger metal-support interaction and higher reducibility shown by the Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalyst were believed to enhance its performance compared to Cu(4)/Ag(1)/CeO2 catalyst by activating more C3H6 to selectively reduce NO within this temperature region. Central composite response surface design methodology was employed to study the effect of operating variables such as temperature, NO and C3H6 concentrations on the SCR of NO by C3H6 over Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalyst and to determine the optimum value of operating variables for maximum NO conversion. Numerical results indicated that the optimum NO conversion of 82.89% is attained at reaction temperature =415.38 C, NO concentration= 1827.16 ppm and C3H6 concentration = 1908.13 ppm. The addition of water vapor to the reactant significantly decreased the NO conversion over Cu(4)/Ag(1)/CeO2 and Cu(4)/Ag(1)/CeO2 (75)-ZrO2(25), but the inhibition was more pronounced over Cu(4)/Ag(1)/CeO2 catalyst

Process optimization studies of dual-bed catalytic reactor system for conversion of methane to liquid hydrocarbons using design of experiments (DOE)

A reactor system with two catalyst beds is proposed for converting methane directly to liquid hydrocarbons. In this dual-bed system, methane is converted in the first stage to oxidative coupling of methane reaction (OCM) products by selective catalytic oxidation with oxygen over a La supported on MgO catalyst. The second bed comprises of a nickel loaded HZSM-5 zeolite catalyst that has been tested as an oligomerization function to convert the OCM products mainly ethylene to liquid hydrocarbons. Thus, the research objective is to establish the factors that exert a greater impact on the dual-bed system and to determine the optimal reaction conditions to achieve the maximum yield of C5+. Three independent factors (temperature (X1), wt% of Ni nickel loading (X2) and methane to oxygen ratio, CH4/02 (X3)) were investigated on the response, yield of C5+ hydrocarbons products (YC5+). These independent variables were coded at three levels and their actual values were selected on the basis of preliminary experimental results. The central composite design (CCD) coupled with response surface methodology (RSM) based on the design of experiments was successfully applied to map the response and to obtain the optimal reaction design. The experimental data was analyzed using an analysis of variance (ANOVA) to determine the significance of the factors tested. Based on the significance of each coefficient, the variable with the largest effect was the quadratic term of temperature, followed by the quadratic term of CH4/02, linear term of Ni wt% and quadratic term of Ni wt%. Numerical results indicated that the optimum C5+ yield of 8.901% was attained at reaction temperature = 742 °C, Ni loading = 0.67 wt% and CH4/02 ratio = 9.68. The model had a satisfactory coefficient of R2 (=0.903) and was verified experimentally. The actual experiment results were in agreement with the prediction. This verification confirmed the validity of the models built, thus indicating the suitability of the model employed and the success of RSM in optimizing the reaction parameters. Furthermore, this optimization strategy led to an increase in the yield of C5+ in the dual- bed system. This exploration also suggests that the concept of this dual catalyst bed system is an interesting candidate for application in methane utilization to produce liquid hydrocarbons

Liquefaction of empty palm fruit bunch (EPFB) in alkaline hot compressed water

Effect of alkalis (NaOH, KOH and K2CO3) on liquefaction of EPFB (emptypalmfruitbunch) biomass liquefaction was investigated under subcritical water conditions in a batch reactor operating at 270 °C and 20 bars for a period of 20 min. Catalytic performance and suitable biomass to water ratio that supported higher EPFB conversion, liquid hydrocarbons yield and lignin degradations were screened. Analytical results indicate that maximum of 68 wt% liquids were produced along with 72.4 wt% EPFB mass conversions and 65.6 wt% lignin degradation under 1.0 M K2CO3/2:10 (biomass/water) conditions. In comparison, the experiments that were performed in the absence of alkalis yielded only 30.4 wt% liquids, converted 36 wt% EPFB and degraded 24.3 wt% lignin. Furthermore, biomass to water ratios >2:10 decreased both solid mass conversion and liquid hydrocarbons' yield. The reactivity of the alkalis was in the order of K2CO3 > KOH > NaOH. The liquid compositions were dominantly phenols and esters; the highest value of phenol (60.1 wt% of liquid yield) was achieved in the case of K2CO3 (1.0 M) with 5 g EPFB/25 ml water ratio while 1.0 M NaOH yielded maximum esters (86.4 wt% of liquid yield). The alkali promoted process assisted with hotwater treatments seemed promising for production of bio-oils from EPFB

Dry Reforming of Methane Over Oil Palm Shell Activated Carbon and ZSM-5 Supported Cobalt Catalysts

In this study, cobalt supported oil palm shell activated carbon (Co/OPS-AC) and ZSM-5 zeolite (Co/ZSM-5) catalysts have been prepared for dry reforming of methane. Cobalt ratios of 6.0 and 14.0 wt% were deposited via wet impregnation method to the OPS-AC and ZSM-5 catalysts. The catalysts were characterized by XRD, N2 adsorption--desorption isotherms, BET surface area, SEM, FESEM-EDX, TPR-H2, and TPD-NH3. The dry reforming of methane was performed using a micro reactor system under the condition of 10,000 ml/h.g-cat, 3 atm, CH4/CO2 ratio of 1.2:1.0 and temperature range from 923 K to 1023 K. The gaseous products were analyzed by gas chromatography (GC) with thermal conductivity detector (TCD) and further quantified to determine the conversions of CH4 and CO2, and the yields of CO and H2. Experimental results revealed both catalysts exhibited lower conversions of CO2 and CH4 with the increase in temperature from 923 K to 1023 K. The reduced conversions may be due to the formation of carboneous substance on the catalyst known as coking. Comparatively, Co/OPS-AC gave higher conversions of CO2 and CH4 as well as higher yields of H2 and CO as it has a higher surface area than Co/ZSM-5 which subsequently rendered higher activity for the reforming of methane. With the increasing cobalt loadings and reaction temperature, OPS-AC(14) catalyst exhibited improved activity and H2/CO ratio. Based on these results, cobalt supported OPS activated carbon catalyst was suggested to be more effective for CO2 and CH4 conversions

Electrochemical Generation of Hydrogen and Methanol using ITO Sheet Decorated with Modified-Titania as Electrode

Current issues of global warming and environmental pollution due to extensive use of fossil fuels has been reached to an alarming position. Being CO2 as main byproduct of fossil fuel consumption and water as abundantly available on earth surface has great potential to replace fossil fuels as energy source. Herein, electrocatalytic CO2 reduction with water for methanol and hydrogen gas (H2) production over ITO sheet decorated with modified-Titanium nanorods (TiO2 NR), has been investigated. The performance comparison of electrocatalytic activity of hydrothermally modified-titania with commercial TiO2 microparticles (MP) were further investigated. Electrochemical reactor containing KHCO3 aqueous solution with CO2 as an electrolyte and modified TiO2 nanorods (NR) as working electrodes offer an eco-friendly system to produce clean and sustainable energy system. The typical rates of product, i.e. methanol and H2 generation from the ITO sheet decorated with modified TiO2 NR layer recorded higher than those for the ITO sheet with commercial TiO2 microparticle. At 2.0V applied potential vs Ag/AgCl as reference electrode, the modified TiO2 NR electrocatalyst yielded methanol at a rate of 3.32 µmol.cm−2.L−1 and H2 at a rate of 6 µmol.cm−2.L−1 which was higher than that of commercial TiO2 MP electrocatalyst (methanol = 1.5 µmol.cm−2.L−1 and H2 = 3.7 µmol.cm−2.L−1). The enhancement in product yields of methanol and H2 was mainly due to the notable improvements and modification in texture of TiO2 working electrode interface. Hence, it is concluded that the modified TiO2 NR can be considered as a competent candidate for sustainable energy conversion applications. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Photocatalytic CO2-hydrogen conversion via RWGSR over Ni/TiO2 nanocatalyst dispersed in Layered MMT Nanoclay

The production of cleaner fuels from renewable and safer energy resources are highly demanding to mitigate energy crises and global warming. In this study, the use of cleaner photo-technology for selective and enhanced CO2 reduction to fuels over nickel (Ni) modified titanium dioxide (TiO2) dispersed in structured montmorillonite (MMT) nanoclay for photocatalytic CO2-hydrogen conversion via reverse water gas shift (RWGS) reaction has been investigated. The catalyst samples, prepared by a single step sol-gel method, were characterised by XRD, FTIR, FESEM and UV-visible spectroscopy. XRD results revealed reduced in TiO2 crystallite size with Ni and MMT loading and produced anatase phase of TiO2. MMT is found efficient for the enhanced dispersion of TiO2 while Ni-promoted efficient charges separation with hindered recombination rate over the structured MMT/TiO2 nanocomposite. The photoactivity of Ni/TiO2-MMT composite for CO2 reduction was conducted in a continuous flow photoreactor using hydrogen as the reducing agent. The main products detected were CO and CH4 with appreciable amounts of C2H4, C2H6 and C3H6 hydrocarbons. The maximum yield of CO produced as the main product over 3 wt% Ni-10 wt% MMT/TiO2 catalyst was 9,429 µmole/g-cat, 209-fold higher than the amount of CO detected over the pure TiO2. Evidently, Ni-promoted TiO2 photocatalytic activity, while MMT is favourable for improved dispersion of Ni/TiO2 catalyst. The dynamic and selective CO evolution was evidently due to efficient light distribution, enlarged active surface area and efficient charges separation with their hindered recombination rate by Ni and MMT. The stability of Ni/TiO2 dispersed over MMT sustained over the irradiation time. With the use of green nanocomposite catalyst, CO2 can be efficiently converted to cleaner fuels with all sustainable systems

Single and two-step homogeneous catalyzed transesterification of waste cooking oil: optimization by response surface methodology

Large number of studies related to alkali and acid catalyzed transesterification of waste cooking oil are widely available, but references for optimization and modeling comparison between single and two-step transesterification are scarce. Therefore, response surface methodology (RSM) has been employed to study the relationship between process variables and predict the optimal conditions. Sulfuric acid and sodium hydroxide were utilized in the pretreatment step and alkali catalyzed transesterification reaction, respectively. The highest free fatty acid (FFA) conversion in the two- and single-step reactions was 93.8% and 82.7%, respectively at the optimal reaction conditions being 1.1 wt% catalyst loading, 6.5:1 methanol to oil ratio, 60°C reaction temperature, and 65 min reaction time.RSM could accurately predict the optimal FFA conversion in both two- and single-step processes by only 0.3% and 1.01% error, respectively. In addition, the two-step method produced higher fatty acid methyl ester (FAME) yield (86.7%) and also improved the final product quality compared to single-step method with only 73.7% biodiesel yield

Supported silicotungstic acid on zirconia catalyst for gas phase dehydration of glycerol to acrolein

The gas phase dehydration of glycerol to acrolein over a series of supported silicotungstic acid (HSiW) on zirconia (10HZ, 20HZ, 30HZ and 40HZ) has been investigated. The catalysts were characterized by temperature programmed desorption, nitrogen adsorption-desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy and energy dispersive X-ray techniques. The large pore diameters (>19 nm) of the prepared catalysts alleviated the coke deposition effect. Also, the specific surface area and acidity of the samples surged from 18 to 22 m2/g and 0.38 to 1.24 mmol/g cat, respectively by varying HSiW loadings from 10 to 40 wt% on zirconia. The highest acrolein yield achieved was 63.75% at 92% glycerol conversion over 30HZ catalyst for 10 wt% glycerol feed concentration and 300 C reaction temperature in 3 h. The combined physico-chemical characteristics of 30HZ made it more superior compared with other samples in the current study

Preparation and characterization of impregnated magnetic particles on oil palm frond activated carbon for metal ions removal

The magnetic adsorbents i.e. oil palm frond-magnetic particles (OPF-MP) and oil palm frond activated carbon-magnetic particles (OPFAC-MP) have been prepared by impregnation of iron oxide via co-precipitation method. The magnetic adsorbents and their parent materials were characterized using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), Brunauer Emmett Teller (BET), Barrett, Joyner & Halenda (BJH) and t-plot method, x-ray diffraction (XRD) and also using vibrating sample magnetometry (VSM) to study their properties and surface chemistry. The activated carbon magnetic adsorbent confers high surface area of 700 m2/g with amorphous structure and magnetic properties of 2.76 emu/g. The OPF-MP and OPFAC-MP were then applied in adsorption study for ions removal of Pb(II), Zn(II) and Cu(II). OPFAC-MP has shown high removal efficiency of 100 % with adsorption capacity up to 15 mg/g of Pb(II), Zn(II) and Cu(II) ions compared to OPF-MP. In addition, the magnetic adsorbents were also compared with their parent materials to observe the effect of magnetic particles. Accordingly, the impregnation of magnetic particles enhances the metal ions adsorption comparing to their parent materials

Thermodynamic Analysis of Glycerol Conversion to Olefins

AbstractThermodynamic equilibrium analysis of glycerol steam reforming to light olefins has been investigated based on the total Gibbs free energy minimization method. Equilibrium product compositions for glycerol steam reforming were determined according to the following range: temperature, 573–1273K; GWR (glycerol/water ratio), 1:12 - 2:1 and pressure, 1-12 bars. Analysis of the feasible reactions revealed hydrogen as the main product followed by carbon monoxide, methane and ethane. The equilibrium analysis indicated light olefins formation was not spontaneous. The amount of ethylene produced was very small, but improved at higher pressure and temperature between 873-1023K. Coking was also dependent on GWR and temperature. From Gibbs analysis, light olefin formation at equilibrium is thermodynamically not feasible, but experimental work involving catalyst proved that ethylene selectivity could be improved in a heterogeneous reaction