H2-rich Gas Research Articles

H2-Rich Gas Production from Gasification of Oily Sludge via Supercritical Water Technology: Synergy Effect of KOH, K2CO3, and Reaction Parameters

Yielding H2 as a sustainable gaseous fuel from oily sludge is of critical importance in mitigating the environmental effects linked with the usage of conventional fossil fuels. The deficiency in the drying of biomass has ensued to the exploration of supercritical water gasification (SCWG) as an effective method for harvesting H2-rich gas. This study utilized a combination of two alkali catalysts (KOH and K2CO3) in supercritical water to generate a H2-rich gas from a conventional oily sludge. The Box-Behnken design was utilized to assess the impact of different operational variables, including temperature (400-600°C), feed concentration (FC) (between 5 and 25 wt.%), residence time (RT) (15-45 min), and catalyst to feed mass ratios (FMR) (0-0.50). The maximum production of H2 at 3.22 mmolg-feed-1 was achieved under optimal conditions of 600°C, 32.76 min, and a KOH to FMR of 0.45 and K2CO3 to FMR of 0.28.

Adaptability analysis of H2-rich gas injection and sintered ore performance with different raw material ratios

As a source substitution technology that reduces pollutants emission and optimizes sinter properties, H2-rich gas injection-assisted iron ore sintering holds significant practical value. This study analyzed the adaptability of this technology to different ore blend ratios and basicity levels by comparing sintering indexes, pore structure, mineral phase composition, and metallurgical performance before and after H2-rich gas injection. The carbon emission reduction following H2-rich gas injection was calculated. The results indicate that increasing the proportion of high-silica, low-alumina ore (Ore-A) and basicity, along with H2-rich gas injection, can effectively enhance sinter yield and quality, but shrink the pore structure of sinter. Under H2-rich gas injection conditions, decreasing Ore-A ratios and increasing basicity can augment SFCA phase formation and mineral phase uniformity, thereby improving the anti-pulverization ability and reductivity of the sinter. H2-rich gas injection presents better adaptability to sintered ore with lower Ore-A ratio and basicity, which can achieve greater improvements in the sintering indexes, RDI, and RI. For a 265 m2 sinter plant producing sinter with 18 wt.% Ore-A and 2.0 basicity, annual CO2 emissions can be reduced by approximately 40,000 t.

Microwave-assisted chemical looping gasification of plastics for H2-rich gas production

Microwave-assisted heating coupled with chemical looping gasification was first proposed for the recycling of plastics into H2 rich gas, achieving a hydrogen conversion efficiency of up to 84.3 %. In the experiment, plastic was initially decomposed into hydrocarbon volatiles, followed by the gasification reactions in the presence of an oxygen carrier under vacuum conditions for 10 min. Subsequently, air was introduced for wax removal and oxygen carrier recovery for another 10 min. This study evaluated the chemical looping gasification performances of polypropylene using oxygen carriers NiaFebOx with different Ni/Fe molar ratios (0, 1:40, 1:20, 1:10, 3:20, and 1:5). NiFe20Ox showed the highest gas yield of 81.3 mmol/gPP with an H2 yield of 46.0 mmol/gPP. Among different microwave powers (590 W, 690 W, 790 W, 890 W, and 990 W), 890 W was identified as the ideal microwave power for maximum gas yield and H2 yield. Microwave-assisted heating exhibited high efficiency, achieving a heating rate of 450°C/min at 890 W, with the microwave oven consuming only 0.182 kWh of electrical power during the entire experiment. In the chemical looping gasification of various plastics (polypropylene, high-density polyethylene low-density polyethylene, polystyrene, and plastics mixture) over NiFe20Ox under 890 W microwave power, polypropylene yielded the highest gas and H2 production. This study provides a novel approach for efficiently recycling plastics, alleviating environmental pollution and contributing to energy sustainability.

In-situ and ex-situ selective catalysis of biochar-based catalysts for the production of high-quality bio-oil and H2-rich gas from tobacco stem

Optimizing the catalytic pyrolysis process is a promising approach to enhance the quality of the resulting products. Thus, four metals (Ni, Fe, Co, Cu) were loaded on biochar support to prepare biochar-based catalysts, and the mechanism of its effect on quality improvement of bio-oil and pyrolysis gas during in-situ and ex-situ pyrolysis of tobacco stem was investigated. The results showed that the biochar-based catalyst has high selectivity for H2-rich and phenols production during in-situ pyrolysis, while the phenols content reached 57.99 % and H2 content reached 49.91 % in Fe@BC group. It is highly selective to H2-rich and N-containing compounds during ex-situ pyrolysis, and the content of N-containing compounds reached 47.23 % and the content of H2 reached 47.59 % in the Ni@BC group. This contributes to the efficient use of high-quality bio-oils and the production of clean gases. Biochar-based catalysts hold significant potential for the pyrolysis industry, paving the way for large-scale production and application of high-quality pyrolysis products.

Optimization of Raceway Adiabatic Flame Temperature Model for H2-Rich Gas Injection Blast Furnace

Optimization of Raceway Adiabatic Flame Temperature Model for H2-Rich Gas Injection Blast Furnace

Investigation of simultaneous production of H2 and separable carbon from CH4 in a fluidised bed of NiO/Ca2Fe2O5/CaO particles

This work investigated the possibility of simultaneous production of hydrogen/syngas and separable solid carbon in a fluidised bed by using CH4-CO2 cycles and exploring the carbon growth over solid catalytic particles of NiO/Ca2Fe2O5/CaO. This two-stage process included i) stage I: H2-rich gas and carbon were simultaneously generated from the interaction between CH4 and NiO/Ca2Fe2O5/CaO particles; and ii) stage II: the reduced/carbon-deposited particles were regenerated in CO2. Following our previous successful demonstration of the process for stable hydrogen production over cycles, this study focused on the formation of solid carbon and aimed at understanding its growth mechanism as well as demonstrating the potential of using fluidisation as a means of automatic carbon separation. By tracking the carbon growth history and the change in phases of the reacted NiO/Ca2Fe2O5/CaO particles at temperatures from 700 to 900 °C, we discovered the formation of various forms of nano-structured carbon from CH4 conversion (e.g. partial oxidation, pyrolysis). These include carbon nanotubes (CNTs), carbon graphite sheets, carbon onions (CNOs), and carbon fibres. Amorphous carbon was also observed, particularly in the initial stage of CH4 conversion. Higher temperatures like 800 °C and 900 °C gave faster kinetics of CH4 conversion and more formation of solid carbon. Fe3C phase was observed on the reduced catalytic particles and could act as an intermediate phase or carbon sink for carbon growth. The results suggested that other mechanisms for carbon deposition, such as directly over Fe sites, may also exist. Fluidisation with a higher U/Umf ratio separated more carbon-rich fines from the bulk catalytic particles in the fluidised bed. Fluidising with air at 700 °C effectively removed amorphous carbon on the reacted catalytic particles, whilst structured carbon remained. Full separation and purification to obtain pure carbon require furthers optimisation of e.g. fluidisation parameters and material design.

Supercritical water valorization of a model wastewater containing anxiolytic and antidepressant drugs: Experimental and thermodynamic assessment

This study presents a continuous hydrothermal process based on the supercritical water (ScW) technology for the treatment of pharmaceutical contaminants in wastewater. Using a simulated wastewater as feedstock, which was prepared with 5 psychoactive drugs (sertraline, paroxetine, zolpidem, escitalopram, and clonazepam), the impact of temperature, feed flow rate, and concentration of H2O2 in the degradation of organic matter was investigated. Thermodynamic aspects of the process were also assessed. The optimal conditions of treatment were at a temperature of 692.8 °C, feed flow rate of 6.6 mL/min, and H2O2 concentration in terms of oxidant coefficient (Ox. C.) of 1.03. Under these conditions, the experimental test achieved a total organic carbon removal efficiency (%RTOC) of 85.9 ± 0.5 %. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations decreased from 559.0 and 1118.4 mg/L to 66.0 and 152.5 mg/L, respectively. The liquid phase was also assessed by toxicity assays against Artemia salina microcrustaceans. For the gaseous phase, hydrogen was identified as the main component (57.7 %). Additionally, an assessment of the energy efficiency of the process scale-up was investigated. The ScW process showed a promising potential for large-scale continuous operations as an energy-efficient solution for wastewater treatment and valorization due to the concomitant production of H2-rich gas.

Upcycling of medical protective clothing for H2 production through catalytic steam reforming over Ni-impregnated catalysts

Disposing medical protective clothing (MPC) presents a significant challenge due to the potential risk of virus contamination. Catalytic steam reforming using Ni-impregnated catalysts was proposed to upcycle MPC for H2-rich gas production. Parametric studies validated that an optimal steam rate of 42 mL/h and a catalytic reforming temperature of 800 ℃ were ideal for H2-rich gas production. 10 wt% Ni impregnated on diverse supports (HY, ZSM-5, MCM-41, γ-Al2O3, MgO, CaO, and activated carbon) were prepared for steam reforming of MPC to assess the impact of support type on H2 production. Of these Ni-impregnated catalysts, Ni/CaO was found to present the highest gas yield (141.4 mmol/g) with a high H2 proportion of 65.2 vol%, due to its superior catalytic cracking and reforming ability of Ni/CaO, favoring the conversion of MPC intermediates into H2-rich gas. To evaluate the recyclability and reforming activity, the optimized Ni/CaO with and without catalyst regeneration was evaluated throughout the successive tests. It was found that Ni/CaO regenerated throughout the successive tests could more effectively mitigate the decreasing tendency of gas yields, favor H2 production, and reduce tar formation than the catalyst without regeneration. That was due to the removal of carbon deposition by catalyst regeneration, thereby mitigating the catalyst deactivation. In contrast, Ni/CaO without the catalyst regeneration was more responsible for the CO2 reduction, accompanying with a more significant decrease of ƞ (4.8 – 3.5 g CO2 /g H2). Overall, this study demonstrated the feasibility of valorizing medical plastic waste into H2-rich gas using effective Ni-based catalysts.

Nickel nanocatalyst on lanthanum aluminate: Optimizing preparation and evaluating performance in glycerol dry reforming for syngas production

In this study, mesoporous nanocrystalline Ni/La-Al catalysts with varying nickel (Ni) loadings (5, 10, 15, and 20 wt.%) were synthesized using a solid-state method for the glycerol dry reforming (GDR) reaction. The effects of different Ni loadings and the addition of steam on the structural and catalytic performance of the catalysts were investigated. Characterization techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and X-ray diffraction (XRD) were employed to analyze the catalysts' properties. Results showed that increasing Ni loading to 10 wt.% improves the catalytic properties. However, by increasing the Ni loading, a decrease in catalytic properties due to increasing particle size, creating NiO bulk phase and surface pore blockage is obvious. A series of experiments were performed to investigate the effect of steam usage on catalytic properties. TPO analysis revealed that steam addition reduces the carbon deposition and shifts oxidation peaks to lower temperatures; consequently, the activity and stability of the catalyst will be enhanced. Although the 5 - 7.5 vol.% of steam in the feed composition significantly stabilizes the catalyst, it is possible to produce H2-rich synthesis gas, and conversely, increasing the temperature reduces the H2/CO ratio. Various examinations were conducted under different conditions, including varying gas hourly space velocity (GHSV), carbon-to-glycerol ratio (CGR), and temperature, to obtain more comprehensive data on the catalysts.

Synthetic opal decorated by Co and Ce oxides as a nanoreactor for the catalytic CO oxidation

Macroporous synthetic opal grown from non-porous silica nanoparticles and decorated by Co and Ce oxides was applied for the catalytic CO oxidation in the inert (TOX) and H2-rich (PROX) gas mixtures. Prepared materials were studied by methods of SEM, TEM, EDX, XRD, XPS and FTIR spectroscopy. The relationship between synthesis conditions, structure, and catalytic behavior of composites is discussed. The best Co-O-Ce interaction and the highest activity in the CO-TOX and PROX are achieved when cerium oxide was added prior to the addition of cobalt oxide. In this case highly dispersed particles of Co3O4 and CeO2 are located in close proximity on the silica surface and anchored between the opal spheres. The use of Co/Ce decorated synthetic opal as a nanoreactor for the catalytic oxidation of CO in the H2 excess makes it possible to achieve 99.5 % conversion of CO at 150°C, the high efficiency and selectivity of the process are maintained in multiple cyclic tests in heating and cooling modes. The synergistic activity of Co and Ce oxides was observed when they both were located together on the outer surface of non-porous SiO2 nanospheres. These results are superior to known data for other catalysts based on Co and Ce oxides.

RuNi/TiZr-MMO Catalysts Derived from Zr-Modified NiTi-LDH for CO-Selective Methanation.

CO-selective methanation (CO-SMET) is an efficient hydrogen-rich (H2-rich) gas purification technology for proton exchange membrane fuel cells. It is vital to develop suitable catalysts with good low-temperature activity for CO-SMET reactions. In this study, RuNi/TiZrx-mixed metal oxide (RuNi/TiZrx-MMO) catalysts with different molar ratios of Zr/Ti, derived from a Zr-promoted NiTi-layered double hydroxide (NiTi-LDH) precursor were successfully prepared using the co-precipitation and wet impregnation methods. The RuNi/TiZr0.2-MMO catalyst possesses higher catalytic performance in a lower temperature window of 180-280 °C, which can reduce the CO concentration to be below 10 ppm. The characterization results obtained from XRD, BET, SEM, TEM, XPS, TPR, and TPD suggest that the addition of ZrO2 increases the surface area of the catalyst, improves the dispersion of metallic nanoparticles, increases the reducibility of Ni species on the RuNi/TiZr0.2-MMO catalyst's surface, and enhances the adsorption and activation ability of CO, resulting in remarkable catalytic performance at lower reaction temperatures. Moreover, the RuNi/TiZr0.2-MMO catalyst demonstrated long-term catalytic stability and carbon resistance.

Valorization of cheese-making residues in biorefineries using different combinations of dark fermentation, hydrothermal carbonization and anaerobic digestion

Dark fermentation (DF), hydrothermal carbonization (HTC) and anaerobic digestion (AD) are applied, in different combinations, to cheese whey (CW), which is the liquid effluent from the precipitation and removal of milk casein during the cheese-making process. The aim and novelty of this research is to investigate the production of various biofuels (H2-rich gas, hydrochar and biogas) in cascade, according to the waste biorefinery concept. The simplest case is the direct AD of CW. The second investigated possibility is the preliminary HTC of CW, producing hydrochar, followed by the AD of the process water from which hydrochar is separated by filtration. The third possibility is based on DF of CW, followed by the AD of the fermentate (F) from DF. The final possibility is based on DF of CW, followed by HTC of the F, and then AD of the process water. Accordingly, the physical and chemical properties of CW, F, resulting hydrochar and process water (PW), and biomethane potentials of CW, F, and process waters are studied to determine the energy and carbon balances of all variants. In brief, the first variant, direct AD of CW, is believed to be the most energy efficient method.

On controllability of fluidized bed reduction of iron ore by CH4 for selective formation of magnetite

Magnetization roasting technology is one of the most representative ways to improve the magnetic separation efficiency and iron recovery of refractory weakly magnetic iron ores. However, utilization of CO-rich or H2-rich gas of strong reducibility as reducing agent for magnetization roasting would lead to over-reduction of Fe2O3 in the ore to non-magnetic FeO, which makes the magnetism of the roasted ore be lower than its maximum, and hence leads to a lower iron recovery than expected. To explore the possibility of using CH4 as reducing agent for controllable reduction of Fe2O3 in iron ores to selectively forming magnetic Fe3O4, i.e., for maximizing the magnetism of the reduced ore for efficient iron separation and recovery, a series of fluidized bed reduction tests in CH4 were carried out on two iron ores of 55 % and 33 % iron at different temperatures for different periods of time, and the resultant reduced ore particles were magnetically separated for recovery of iron concentrate. XRD and ICP analyses were performed on all recovered iron concentrates to identify the crystal forms of their iron species and to quantify their iron contents. The results have shown that the controllable reduction by CH4 of Fe2O3 in the iron ores to strongly magnetic Fe3O4 can be realized by controlling the reduction temperature and time condition applied. The resultant concentrates can be fully recovered by magnetic separation in a weak magnetic field of 60 kA/m to attain a maximum iron recovery of 98 % for the high-grade ore and that of 65 % for the low-grade ore. Besides, the results have also shown that the most critical factor affecting the controllability of the ore reduction process and the selectivity to the generation of magnetic Fe3O4-containing particles is the reduction temperature, and that the upper temperature threshold for the controllable reduction and selective generation of strongly magnetic iron concentrate is about 650℃.

A combined experimental and simulations assessment of CO2 capture and CO2/H2 separation performance of aminosilane-grafted MCM-41 and pore-expanded MCM-41

Amine-functionalized mesoporous silica materials have attracted considerable attention as robust adsorbents for large-scale CO2 capture and direct air capture (DAC). Amine grafting increases selective affinity at low pressures, yet also often reduces the adsorbent's pore volume and surface area, affecting the kinetics and capacity upon CO2 adsorption. MCM-41 and pore-expanded MCM-41 (PE-MCM-41) were developed here, functionalized using 3-aminopropyl triethoxy silane (APTES), and comparably evaluated for their carbon capture performance at different conditions by a combinational experimental, equilibrium and kinetic modelling, and molecular simulations approach. In specific, CO2 adsorption capacity, CO2/N2 selectivity, CO2 adsorption at humid conditions, heat of adsorption, and regeneration/cyclability were assessed, coupled to molecular simulation insights on the physisorption and chemisorption contribution to the overall adsorption uptake. Indicatively, a capacity value of 3.07 and 2.44 mmol/g was obtained for APTES-PE-MCM-41, and 2.27 and 1.89 mmol/g for APTES-MCM-41, under wet and dry conditions, respectively. The CO2 selective adsorption from H2 rich gas streams was also examined over APTES-MCM-41 in order to assess the potential application in H2 stream purification process. The latter is of high significance in order to use hydrogen as fuel e.g. in anion exchange membrane fuel cells for power production since the presence of CO2 in the feed composition is considered a major drawback in their commercialization.

Catalysis/sorption enhanced pyrolysis-gasification of biomass for H2-rich gas production: Effects of various nickel-based catalysts addition and the combination with calcined dolomite

The effects of addition of various Ni-based catalysts and their combination with calcined dolomite on H2-rich gas production were investigated during catalysis/sorption enhanced pyrolysis-gasification of sawdust. It was found that catalyst support greatly affected the catalytic performance of Ni-based catalysts, the highest H2 concentration and yield was obtained by NiO/SiO2, followed by NiO/γ-Al2O3 and NiO/ZSM-5. Additional active sites on Ni-based catalyst would be formed by introduction of secondary metals onto NiO/γ-Al2O3. Positive synergistic effect between secondary metals and Ni was observed, especially for Mg and Co, resulting in further improved H2 production. Calcined dolomite was further introduced into the process to enhance H2 production, simultaneous catalysis and sorption was found to be better for H2 production than sequential catalysis and sorption. The addition of calcined dolomite could offset the catalytic performance difference for varied Ni-based catalysts due to its catalysis/sorption enhancing effect. Comparatively, bimetallic catalysts were more effective than monometallic catalysts when combined use with calcined dolomite, the H2 concentration was significantly improved despite of the slight changes in H2 yield. Ni-Cu/γ-Al2O3 and Ni-Zn/γ-Al2O3 with good performance on WGS reaction showed better synergistic effect with calcined dolomite, a highest H2 concentration of 87.06 vol.% was achieved by Ni-Cu/γ-Al2O3 catalyst.

Co-production of porous N-doped biochar and hydrogen-rich gas production from simultaneous pyrolysis-activation-nitrogen doping of biomass: Synergistic mechanism of KOH and NH3

In this study, a method of simultaneous activation and nitrogen doping during biomass fast pyrolysis for co-production of porous N-doped biochar and H2-rich gas production was proposed. The effect of temperature on chemical interaction mechanism of KOH and NH3 was investigated at 500–800 °C. Results showed that KOH and NH3 had a synergistic effect on pore development and nitrogen doping, and the specific surface area and nitrogen content reached maximum values of 2008.37 m2/g and 5.05 wt%, respectively. It may be due to that NH3 entered pores generating by KOH activation for further activation, and at the same time, excessive NH3 could convert new O-containing groups to N-containing groups for more effective nitrogen doping. What's more, the H2 concentration and yield were up to 56.67 vol% and 517.95 mL/g, respectively. It indicates that the synchronization method of fast pyrolysis-activation-nitrogen doping is a promising approach, which is of great significance for the high-value utilization of biomass.

Woody biomass waste derivatives in decarbonised blast furnace ironmaking process

Modern ironmaking process relies significantly on fossil-related fuels, which ultimately results in the enormous CO2 emitted into the atmosphere. Biomass of plant origin, as a carbon-neutral energy source, has been considered as an alternative to fossil-based reducing agents such as coke. This study aims to investigate the potential of three woody biomass waste derivatives produced from biomass waste pyrolysis and gasification, namely charcoal, bio-oil, and bio-syngas, as the reducing agents in blast furnace. A model based on heat and mass balance and Gibbs free energy minimisation is proposed to simulate an ironmaking process with assistance of these derivatives. The effects of specific composition of biomass waste derivatives on process operation, CO2 emissions, and coke replacement are explored. Also the effects of H2-rich gas produced from biomass waste gasification on the blast furnace operation are estimated. Results indicate that reactions of woody biomass waste derivatives in blast furnace are complex and greatly dependent on composition. When charcoal has a higher carbon content, lower CO2 concentration is found from the top gas. The higher content of hydrogen in bio-oil will inhibit further reduction in CO2 emissions. Bio-syngas with H2/CO ratio of 1.3 proves to have a remarkable potential to reduce CO2 emissions. From the aspects of available biomass waste resources across the world, woody biomass waste derivatives as reducing agents are more suitable for countries with the limited pig iron production. This study provides a reference on the future of moving forward the decarbonised ironmaking by using woody biomass waste derivatives.

Quantification of Mixing Quality Effects on Flashback Limits for H2-Rich Fuel Gases in Lean Premixed Combustion Using Laser-Induced Fluorescence of Acetone

Abstract One of the main challenges arising from hydrogen-rich fuel mixtures is to prevent flame flashback. In typical gas turbines, the fuel is commonly injected through holes in the axial swirler vanes to achieve a high mixing quality. However, this injection method is not perfect and can cause nonhomogeneous mixing regions, so that locally rich fuel clusters can significantly increase flashback propensity. This work aims to establish a link between the local mixing quality of fuel and air and flashback limits obtained experimentally under elevated pressure conditions. The nonreacting experiments have been conducted at an atmospheric mockup test rig and acetone-planar laser-induced fluorescence (PLIF) has quantified the local fuel concentration. Zones of high equivalence ratio are evident close to the center body wall. The near-wall equivalence ratio fields reveal that the critical probability of the local equivalence ratio being greater than the one for perfect premixing is between 20% and 35% for all hydrogen concentrations at the flashback limits observed. A probability of 35% is selected as a critical threshold to derive a correlation between the local and the global equivalence ratio in technical premixing. Even though the correlation is specific to the investigated burner configuration, the presented methodology offers valuable insights into the impact of the local mixing quality on flashback propensity, which can improve flashback prediction models formulated for perfect premixing conditions.

High quality oil and H2-rich gas production from municipal solid wastes through pyrolysis and catalytic reforming: Comparison of differently modified waste char-based catalysts

Pyrolysis, a promising method for extracting energy and value-added chemicals from municipal solid waste (MSW), encounters challenges associated with generation of inferior quality oil and low-quality char byproducts. In this context, this study proposed catalytic reforming of pyrolysis volatiles derived from MSW, using MSW char (MSWC) and modified MSWC-based catalysts to produce high-quality oil containing monocyclic aromatic hydrocarbons (MAH), alkanes and alkenes, and H2-rich gas products. Three groups of modified MSWC-based catalysts are prepared through the activation of MSWC with Na2CO3, Zn(NO3)2⋅6 H2O and ZnCl2 for the reforming process. Experimental findings reveal that impregnating MSW with ZnCl2, specifically the ZnCl2/C-1:1 char from one-step pyrolysis, exhibits the most favorable catalytic performance, with a 47% selectivity of MAH in oil product, yielding > 25 wt% oil at 450 °C and a calorific value of 26.24 MJ/kg. Simultaneously, 44 wt% of MSW is converted into gas products with a 49 v/v% H2 concentration for ZnCl2/C-1:2 catalyst. The Na2CO3-activated MSWC catalyst corresponds to the highest oil yields and achieves an alkane selectivity of 45.95 area% in the oil product, while Zn(NO3)2-activated MSWC catalyst corresponds to the highest oxygen compounds in the oil product, thus with the lowest calorific value of 19.4 MJ/kg. These results highlight that varying catalyst modifications to MSW char can effectively improve the production of distinct oil compounds, with Zn[OH]+ species and higher Lewis-acid content in the catalyst exerting a positive influence on aromatic hydrocarbon production; and Na2CO3 facilitating alkane production. This study thus provides valuable insights for upgrading oil product quality and increasing H2 concentration in gas products, particularly at lower pyrolysis and reforming temperatures.

Enhanced mono-aromatics production by the CH4-assisted pyrolysis of microalgae using Zn-based HZSM-5 catalysts

This study presents the catalytic pyrolysis of microalgae, Chlorella vulgaris (C. vulgaris), using pure CH4 and H2-rich gas evolved from CH4 decomposition on three different HZSM-5 catalysts loaded with Zn, Ga, and Pt, aimed specifically at producing high-value mono-aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEX). In comparison with that for the typical inert N2 environment, a pure CH4 environment increased the bio-oil yield from 32.4 wt% to 37.4 wt% probably due to hydrogen and methyl radical insertion in the bio-oil components. Furthermore, the addition of bimetals further increased bio-oil yield. For example, ZnPtHZ led to a bio-oil yield of 47.7 wt% in pure CH4. ZnGaHZ resulted in the maximum BTEX yield (6.68 wt%), which could be explained by CH4 activation, co-aromatization, and hydrodeoxygenation. The BTEX yield could be further increased to 7.62 wt% when pyrolysis was conducted in H2-rich gas evolved from CH4 decomposition over ZnGaHZ, as rates of aromatization and hydrodeoxygenation were relatively high under this condition. This study experimentally validated that the combination of ZnGaHZ and CH4 decomposition synergistically increases BTEX production using C. vulgaris.