Household food waste conversion to biohydrogen via steam gasification over copper and nickel-loaded SBA-15 catalysts.

Household food waste (FW) was converted into biohydrogen-rich gas via steam gasification over Ni and bimetallic Ni (Cu-Ni and Co-Ni) catalysts supported on mesoporous SBA-15. The effect of catalyst method on steam gasification efficiency of each catalyst was investigated using incipient wetness impregnation, deposition precipitation, and ethylenediaminetetraacetic acid metal complex impregnation methods. H2-TPR confirmed the synergistic interaction of the dopants (Co and Cu) and Ni. Furthermore, XRD and HR-TEM revealed that the size of the Ni particle varied depending on the method of catalyst synthesis, confirming the formation of solid solutions in Co- or Cu-doped Ni/SBA-15 catalysts due to dopant insertion into the Ni. Notably, the exceptional activity of the Cu-Ni/SBA-15-EMC catalyst in FW steam gasification was attributed to the fine distribution of the concise Ni nanoparticles (9 nm), which resulted in the highest hydrogen selectivity (62 vol%), gas yield (73.6 wt%). Likewise, Cu-Ni solid solution decreased coke to 0.08 wt%.

Hydrogen-rich gas production via steam gasification of food waste over basic oxides (MgO/CaO/SrO) promoted-Ni/Al2O3 catalysts.

Food waste, a renewable resource, was converted to H2-rich gas via a catalytic steam gasification process. The effects of basic oxides (MgO, CaO, and SrO) with 10 wt% Ni/Al2O3 on the gasification properties of food waste were investigated using a U-shaped gasifier. All catalysts prepared by the precipitation method were analyzed by X-ray diffraction, H2-temperature-programmed reduction, NH3-temperature-programmed desorption, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The Ni/Al2O3 catalyst was reduced incompletely, and low nickel concentrations were detected on the surface of the alumina. The basic oxides minimized the number of acid sites and suppressed the formation of nickel-aluminate (NiAlxOy) phase in catalyst. In addition, the basic oxides shifted nickel-aluminate reduction reaction to lower temperatures. It resulted in enhancing nickel concentration on the catalyst surface and increasing gas yield and hydrogen selectivity. The low gas yield of the Ni/Al2O3 catalyst was attributed to the low nickel concentration on the surface. The maximum gas yield (66.0 wt%) and hydrogen selectivity (63.8 vol%) of the 10 wt% SrO- 10 wt% Ni/Al2O3 catalyst correlated with the highly dispersed nickel on the surface and low acidity. Furthermore, coke deposition during steam gasification varied with the surface acidity of the catalysts and less coke was formed on 10 wt% SrO- 10 wt% Ni/Al2O3 due to efficient tar cracking. This study showed that the steam gasification efficiency of the Ni/Al2O3 catalyst could be improved significantly by the addition of SrO.

Catalytic upgrading of Quercus Mongolica under methane environment to obtain high yield of bioaromatics.

This work investigated the impact of pyrolysis medium and catalyst on the production of bio-BTX (benzene, toluene, and xylene) from Quercus Mongolica (Q. Mongolica) via catalytic pyrolysis. Two different pyrolysis media (N2 and CH4) and five different zeolite catalysts (HY, HBeta, HZSM-5, 1 wt% Ni/HZSM-5, and 1 wt% Ga/HZSM-5) were considered for the Q. Mongolica pyrolysis. The HZSM-5 yielded more BTX than the HY and HBeta due to its strong acidity. The employment of CH4 as the pyrolysis medium improved the BTX yield (e.g., 2.7 times higher total BTX yield in CH4 than in N2) and resulted in low coke yield (e.g., 5.27% for N2-pyrolysis and 2.57% for CH4-pyrolysis) because the CH4-drived hydrogen simulated a hydropyrolysis condition and facilitated dehydroaromatization reaction. CH4 also led to direct coupling, Diels-Alder, and co-aromatization reactions during the pyrolysis, contributing to enhancing the BTX yield. The addition of Ga to the HZSM-5 could further increase the BTX yield by means of facilitating hydrocracking/demethylation and methyl radical formation from CH4 assisting the generation of >C2 alkenes that could be further converted into BTX on acid sites of the HZSM-5.

Enhancement of aromatics from catalytic pyrolysis of yellow poplar: Role of hydrogen and methane decomposition.

The present study examined the effects of the pyrolysis environment on BTEX (benzene, toluene, ethylbenzene, and xylenes) production in the catalytic upgrading of yellow poplar pyrolysis vapors. Three different gas environments, N2, CH4, and pre-decomposed CH4 stream (10 wt%-Ni/5 wt%-La2O3-5 wt% CeO2-Al2O3), which is a mixture of H2 (55.62%) and CH4, were studied using two types of zeolite catalysts, HZSM-5, and 1 wt% Ga/HZSM-5. The BTEX yields were enhanced linearly in the order N2 < CH4 < CH4 ex-situ decomposition. The highest BTEX yield of 9.58 wt% was obtained under the CH4 ex-situ decomposition environment over 1 wt% Ga/HZSM-5. The methane and hydrocarbons derived from biomass were activated on highly dispersed (GaO)+ sites and transformed smoothly to BTEX by aromatization on the BrØnsted acid sites of Ga/HZSM-5. The hydrogen produced from methane decomposition also assisted in aromatics production through the hydrodeoxygenation of methoxyphenols, guaiacols and catechols.

Pyrolysis of solid waste residues from Lemon Myrtle essential oils extraction for bio-oil production.

Solid waste residues from the extraction of essential oils are projected to increase and need to be treated appropriately. Valorization of waste via pyrolysis can generate value-added products, such as chemicals and energy. The characterization of lemon myrtle residues (LMR) highlights their suitability for pyrolysis, with high volatile matter and low ash content. Thermogravimetric analysis/derivative thermogravimetric revealed the maximum pyrolytic degradation of LMR at 335 °C. The pyrolysis of LMR for bio-oil production was conducted in a fixed-bed reactor within a temperature range of 350-550 °C. Gas chromatography-mass spectrometry showed that the bio-oil contained abundant amounts of acetic acid, phenol, 3-methyl-1,2-cyclopentanedione, 1,2-benzenediol, guaiacol, 2-furanmethanol, and methyl dodecanoate. An increase in pyrolysis temperature led to a decrease in organic acid and ketones from 18.09% to 8.95% and 11.99% to 8.75%, respectively. In contrast, guaiacols and anhydrosugars increased from 24.23% to 30.05% and from 3.57% to 7.98%, respectively.