Catalytic gasification of oil palm frond biomass in supercritical water using MgO supported Ni, Cu and Zn oxides as catalysts for hydrogen production

Non-noble metal supported catalysts such as 20NiO/MgO, 20CuO/MgO and 20ZnO/MgO were catalyzed the gasification of oil palm frond biomass in supercritical water for hydrogen production. All the catalysts are found to be pure with no impurities present. The specific surface area of these catalysts can be arranged in the order of 20NiO/MgO (30.1 m2 g–1) > 20CuO/MgO (16.8 m2 g–1) > 20ZnO/MgO (13.1 m2 g–1). Although catalysts with larger specific surface area are beneficial for catalytic reactions, in this study, the largest specific surface area did not lead to the highest catalytic performance. It is found that the 20ZnO/MgO catalyst (118.1 mmol ml−1) shown the highest H2 yield than the 20CuO/MgO (81.1 mmol ml−1) and 20NiO/MgO (72.7 mmol ml−1) catalysts. In addition, these supported catalysts also shown higher H2 selectivity with reached 83.8%, 84.9% and 87.6% for 20CuO/MgO, 20NiO/MgO and 20ZnO/MgO catalysts. Other factors such as dispersion, basicity and bond strength play more important roles in supercritical water gasification of biomass to produce hydrogen

Free-H2 deoxygenation of Jatropha curcas oil into cleaner diesel-grade biofuel over coconut residue-derived activated carbon catalyst

Diesel-like hydrocarbons were produced by the catalytic deoxygenation (DO) of Jatropha curcas oil (JCO) over novel Agx/AC and Niy-Agx/AC catalysts under an H2-free atmosphere. The AC was synthesized from coconut fibre residues (CFR), where CFR is the by-product from coconut milk extraction and is particularly rich in soft fibres with high mineral content. The Niy-Agx/AC catalyst afforded higher DO activity via the decarboxylation/decarbonylation (deCOx) route than Agx/AC due to the properties of Ni, synergistic interaction of Ni and Ag species, adequate amount of strong acid sites and large number of weak acid sites, which cause extensive C-O cleavage and lead to rich formation of n-(C15+C17) hydrocarbons. The effect of Ag and Ni content were studied within the 5 to 15 wt% range. An optimum Ni and Ag metal content (5 wt%) for deCOx reaction was observed. Excess Ni is not preferable due to a tendency for cracking and Ag-rich containing catalyst weakly enforced triglycerides breaking. The Ni5-Ag5/AC govern exclusively decarbonylation reaction, which corroborates the presence of Ni²⁺ species and a high amount of strong acid sites. Ultimately, Ni5-Ag5/AC in the present study shows excellent chemical stability with consistent five reusability without drastic reduction of hydrocarbon yield (78–95%) and n-(C15+C17) selectivity (82–83%), which indicate favourable application in JCO DO

Catalytic supercritical water gasification of oil palm frond biomass using nanosized MgO doped Zn catalysts

In this work, nanosized MgO doped Zn catalysts (Mg1-x Znx O; x = 0.05, 0.10, 0.15, 0.20) were catalyzed the supercritical water gasification (SCWG) of oil palm frond (OPF) biomass for hydrogen production. Increased the amount of Zn in the catalyst enlarged the crystallite size, thus, reduced the surface area. Interestingly, all the synthesized catalysts have crystallite sizes of less than 50 nm. In-depth Rietveld refinement analysis revealed that the enlargement of the crystallite size is due to the phenomenon of cell expansion when the smaller Mg2+ ions being replaced by the larger Zn2+ ions during the doping process. Increased the Zn content also improved the basicity properties. Among the synthesized catalysts, the Mg0.80 Zn0.20 O exhibited the highest total gas volume of 213.5 ml g-1 of the biomass with 438.1% of increment in terms of H2 yield. The metal oxide doped materials serve as a new catalyst structure system for the SCWG technology

Structural and catalytic studies of Mg1-xNixO nanomaterials for gasification of biomass in supercritical water for H2-rich syngas production

Nowadays, catalytic supercritical water gasification (SCWG) is undoubtedly used for production of H2-rich syngas from biomass. The present study reported the synthesis and characterisation of Mg1-xNixO (x ¼ 0.05, 0.10, 0.15, 0.20) nanomaterials that were obtained via self-propagating combustion (SPC) method, and catalysed the SCWG for the first time. It had found that increased the nickel (Ni) content in the catalyst reduced the crystallite size, thus, increased the specific surface area, which influenced the catalytic activity. The specific surface area followed the order of Mg0.95Ni0.05O (36.2 m2 g1 ) < Mg0.90Ni0.10O (58.9 m2 g1 ) < Mg0.85Ni0.15O (63.6 m2 g1 ) < Mg0.80Ni0.20O (67.9 m2 g1 ). From the Rietveld refinement, the Ni that was successfully partial substituted in the cubic crystal structure of MgO resulting in a cell contraction which ascribed the reduction of crystallite size. Increased the amount of Ni also narrowed the pore size distribution ranging between 4.17 nm and 6.23 nm, as well as increased the basicity active site up to 5741.0 mmol g1 at medium basic strength. All the synthesised nanocatalysts were catalysed the SCWG of OPF (oil palm frond) biomass. Among them, the mesoporous Mg0.80Ni0.20O nanocatalyst exhibited the highest total gas volume of 193.5 mL g1 with 361.7% increment of H2 yield than that of the non-catalytic reaction

SiO2-rich sugar cane bagasse ash catalyst for transesterification of palm oil

This study demonstrated the performance of the sugarcane bagasse ash (SCBA) impregnated with calcium oxide (CaO) as a novel heterogeneous basic catalyst in biodiesel production. The SCBAwas prepared by calcination for 2 h at 500 to 800 °C and impregnated with CaO loadings (10 to 40 wt.%). The prepared SCBA/CaO catalyst was characterized using Fourier transform infrared spectros-copy (FTIR), scanning electron microscopy(SEM), X-ray diffraction (XRD), temperature programmed desorption of carbon dioxide(TPD-CO2), thermal gravimetric analysis (TGA), X-ray fluorescence (XRF) and Brunauer-Emmett-Teller (BET) surface characteristics. A series of transesterification reactions were conducted to evaluate the performance of the catalysts. As a result, highest FAME yield of 93.8% was obtained by using SCBA600°CCaO (40%) catalyst at 20:1 methanol-to-oil molar ratio, reaction temperature of65 °C, with 6 wt.% catalyst in 3 h. Besides, the catalyst can be reused up to 5 reaction cycles with biodiesel yield of 93.0% and 70.3%at first and fifth cycles, respectively. In this work, it was found that the natural SiO2in the SCBA has a significant role to enhance the catalytic performance and reduce the catalyst’s deactivation drawback by minimizing the leaching of active sites

Production of renewable diesel from Jatropha curcas oil via pyrolytic-deoxygenation over various multi-wall carbon nanotube-based catalysts

Jatropha curcas is a highly toxic plant that produces seed containing viscous oil with productivity (2 ton/ha), it grows in tropical and sub-tropical regions and offer greater adaptability to a wide range of climatic and soil conditions. Its oils have been noted as an important alternative to produce green diesel via deoxygenation reaction. This study, deoxygenation of jatropha curcas oil (JCO) was carried out over NiO–Fe2O3 and NiO–ZnO catalysts that supported onto multi-walled carbon nanotube (MWCNT). It had found that high Fe and Zn dosages were ineffective in deoxygenation and greatest activity was observed on NiO(20) Fe2O3(5)/MWCNT catalyst. Structure-activity correlations revealed that low metal loading, large density of weak + medium acidic sites and strong basic sites play key role in enhancing the catalytic activities and n-(C15+C17) selectivity. Comparing carbon nanostructures and carbon micron size supported NiO-Fe2O3 revealed that green diesel obtained from NiO–Fe2O3/MWCNT catalysed deoxygenation had the highest heating value and the lowest amounts of oxygen content. Thereby, it confirmed the importance of carbon nanostructure as the catalyst support in improving the diesel quality. Considering the high reusability of NiO-Fe2O3/MWCNT (6 consecutive runs) and superior green diesel properties (flash point, cloud properties and cetane index) demonstrated the NiO–Fe2O3/MWCNT catalyst offers great option in producing excellent properties of green diesel for energy sector

Catalytic gasification of oil palm frond biomass in supercritical water for hydrogen production using supported and doped magnesium oxide catalysts

Utilization of hydrogen as an energy carrier for transportation sector and other energy utilities could reduce the dependency on conventional fossil fuels and cater the increasing energy demands. The combustion of hydrogen gas (H2) in a fuel cell engine produces only water as its by-product with zero greenhouse gases that did not promoting the global warming. Production of H2 from biomass is one of the ultimate goals in renewable and sustainable energy development program. Various technologies have been developed for the conversion of biomass into combustible hydrogen. In this study, supercritical water gasification (SCWG) was used to convert the oil palm frond (OPF) biomass into H2-rich syngas. Two series of catalysts namely supported and doped magnesium oxide (MgO) catalysts were synthesized and characterized before catalyzing the SCWG reaction that enhanced the total H2 yield. Non-noble metal supported catalysts such as 20NiO/MgO, 20CuO/MgO and 20ZnO/MgO were synthesized using an impregnation method. The 20ZnO/MgO catalyst found to be produced the highest H2 yield even though it possessed the smallest specific surface area. Other factors such distribution, basicity and bond strength of the catalysts played important roles for higher catalytic performances. It is also believed that the catalyst stability can be further improved by doping the active metal into the crystal structure of the MgO catalyst. Therefore, the Ni doped MgO catalysts (Mg1-xNixO) and the Zn doped MgO catalysts (Mg1-xZnxO) with x = 0.05, 0.10, 0.15, 0.20, were synthesized using a self-propagation combustion method. Interestingly, the Rietveld refinements showed contraction of crystal structure for the Ni doped MgO catalysts and expansion of crystal structure for the Zn doped MgO catalysts, upon increasing the metal contents. It means the crystallite size, surface area, porosity and basicity were affected. The correlation between catalytic performance and properties for selected supported and doped MgO catalysts were investigated. The doped catalysts have larger surface areas than the supported catalysts, which can be arranged in the order of Mg0.80Ni0.20O (67.9 m2 g-1) > Mg0.80Zn0.20O (36.3 m2 g-1) > 20NiO/MgO (30.1 m2 g-1) > 20ZnO/MgO (13.1 m2 g-1). Whether supported or doped, the Ni-based catalysts always exhibited larger surface area than that of the Zn-based catalysts. Unexpectedly, the Zn-based catalysts produced higher H2 yield from the SCWG of OPF biomass although these catalysts have smaller surface areas. When compared to the non-catalytic SCWG reaction, the H2 yield increased by 187.2% for 20NiO/MgO, 269.0% for 20ZnO/MgO, 361.7% for Mg0.80Ni0.20O, and 438.1% for Mg0.80Zn0.20O. The Mg0.80Ni0.20O catalyst gave the highest H2 yield because it had the highest number of basic sites approximately twenty-fold higher than that of the 20ZnO/MgO catalyst. It also proved to be the most stable catalyst, as verified from the X-Ray photoelectron spectroscopy (XPS) outcomes. As such, this study concludes that the catalytic performances do not only depend on the specific surface area, but also influenced by the basicity properties and the catalyst stability. In addition, the doped catalysts may serve as a new catalyst system for the SCWG for hydrogen production

Effects of Cationic Surfactant in Sol-gel Synthesis of Nano Sized Magnesium Oxide

AbstractIn this study, sol-gel method was used to synthesize nano sized of magnesium oxide (MgO). Magnesium acetate tetrahydrate and tartaric acid have been dissolved in ethanol and formed a precursor before calcined at 600 ¡C for 6h to produce MgO nanoparticles. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) had used in the sol-gel reaction to reduce agglomeration of the nanoparticles. Two samples (MgO and MgO-CTAB) were characterized using simultaneous thermogravimetric analyzer (STA), X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM) and nitrogen adsorption-desorption measurement. Formation of the samples via a sol-gel route is discussed and confirmed using the STA results. The precursor formed was identified as magnesium tartrate and decomposed to MgO and MgO-CTAB after the calcinations, and gave a single phase of samples as shown by the XRD patterns. The used of CTAB in this sol-gel method gives the MgO nanoparticles with less agglomeration. This was proved by the FESEM micrographs, the MgO-CTAB has spherical shape and the agglomeration seems to be less than the MgO. It suggests that the cationic surfactant controls the morphology of the samples

Effect of stabilizers in the synthesis of silver nanoparticles and Methylene blue oxidation

Metal nanocatalysts have received increasing attention in catalysis due to their higher reactivity and surface area-to-volume ratio at nano-size. Silver nanoparticle (AgNP) is among metal nanocatalysts that have been studied in various catalytic reactions (e.g., hydrogenation and oxidation). However, the high reactivity of AgNPs at nano-size caused instability and aggregation. Therefore, stabilizing molecules (or stabilizers) are always applied to maintain the nano size of AgNPs and prevent aggregation. Herein, the effects of different types and molar ratio of stabilizers-to-Ag precursor, to the synthesized AgNPs (i.e, size and concentration) were investigated. Two types of stabilizers, polyvinylpyrrolidone (PVP) and citrate were used in this study. The roles of stabilizers to the catalytic performance of synthesized AgNPs were then elucidated by using methylene blue oxidation as the model reaction. The UV-Vis absorption analyses showed that both stabilizers produced slightly different size and concentration of AgNPs based on the different wavelength and absorption intensity of the peak. We also found that the molar ratio of stabilizers-to-Ag precursor that produced better yield of AgNPs was 1:1 and 1:3 for PVP and citrate, respectively. Then, AgNPs stabilized by citrate was found having slightly higher catalytic activity in the methylene blue oxidation than AgNPs stabilized by PVP. This study provides insights to the roles of stabilizers for the synthesis of stable AgNPs with efficient catalytic reaction and can be used as guideline to other metal nanocatalysts

Green synthesis of silver nanoparticles using coffee extract for catalysis

The green synthesis method for producing metal nanoparticles has become more popular because it is more environmentally friendly and low cost. This study used a green approach to synthesize silver nanoparticles (AgNPs) using coffee Arabica bean's extract to reduce and stabilizing agents. The coffee extract was analyzed using GC-MS to identify the bioactive compounds in the extract, and Folin-Ciocalteu colorimetric test was done to find the total phenols in the extract. Later, the extract was used in the synthesis of AgNPs. Effects of synthesis parameters such as temperature, reaction time, pH, and amount of coffee extract on the formation of AgNPs were investigated. The formation of AgNPs was mainly observed using UV-Vis absorption spectroscopy. It was found that pH influenced the size of particles produced in which higher pH produce smaller particles than lower pH while other synthesis parameters mainly affected the yield of the AgNPs. The catalytic application of as-synthesized AgNPs was then evaluated in reducing methylene blue (MB) dye in a solution using NaBH4 as a reducing agent. The results show that the green-synthesized AgNPs were capable of catalyzing the reduction of MB dye in the solutio