H2-rich Syngas Production Research Articles

Selective production of phenol from the end-of-life wind turbine blade through catalytic pyrolysis

This study employed catalytic pyrolysis to enhance the selectivity and yield of phenol in the pyrolysis oil derived from the end-of-life wind turbine blade (WTB). It was confirmed that the NiO(10)/Al2O3 catalyst exhibited the best activity, reaching a phenol selectivity of 28.57 % at 500 °C with a heating rate of 10 °C/min. Furthermore, a competitive phenomenon between the catalytic formation of phenol and that of gaseous products was observed. Characterization results indicated that at lower loading content of NiO on the Al2O3 carrier, NiAl2O4 crystals tended to form preferentially, which reduced catalyst activity by covering surface strong acid sites. With increasing the loading content of NiO, saturation of NiAl2O4 formation occurred, and free NiO crystals became dominant. This resulted in the creation of abundant Lewis acid sites, enhancing the catalytic formation of phenol. Whilst, excessive accumulation of free NiO crystals increased strong acid sites and significantly generated lattice oxygen, promoting the cracking of pyrolysis oil to gaseous products, which was detrimental to phenol enrichment but facilitated the production of H2-rich syngas. The conclusions offered valuable insights for upgrading pyrolysis products derived from epoxy resin polymers during the recovery of end-of-life WTB.

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.

Development of nickel-based bimetallic catalysts for production of hydrogen-rich syngas via supercritical water gasification of liquid residue from hydrothermal pretreatment of food waste

Hydrothermal carbonization has become increasingly prevalent in the pretreatment of food waste, leading to the generation of substantial volumes of liquid effluent. This hydrothermal liquid effluent from food waste (HLF) contains high content of organic compounds, making it challenging to treat using conventional methods. In this regard, the HLF was considered a potential source for energy production via supercritical water gasification (SCWG). This study aimed to develop effective bimetallic catalysts based on Ni/Al2O3 with four different promoters (Cu, Co, La, and Ce), and investigated their performance in the catalytic SCWG for the treatment of HLF and hydrogen production. Among the tested promoters, the Ce-Ni catalyst was considered the most suitable in terms of its highest H2 yield and H2 selectivity. The optimal Ce content was found to be 5 wt%, with a catalyst dosage of 5 % by weight of HLF. These conditions resulted in the highest H2 selectivity of 1.61 and a relatively high H2 yield of 749.60 mmol/L under SCWG operating conditions of 480 °C and 30 min. Excessive catalyst dosages increased total syngas yield but reduced H2 selectivity. The stability test demonstrated that the Ce promoter contributed to enhancing the catalyst resistance to deactivation by coke deposition. The hydrogen production of 5Ce-Ni decreased by 13.8 % after three reuses, whereas a larger decrease of 26.0 % was observed with Ni/Al2O3. These findings indicate that Ce-Ni catalyst show promise for enhancing H2-rich syngas production in the SCWG of hydrothermal liquid effluent from food waste.

H2-enriched gaseous fuel production via steam-gasification of biomass by using lime-based sorbents

The main objective of the present study was to compare the catalytic activity of selected limestones (Göynük, Dikmen, Polatlı Yolu, Kınık Tüneli and Köserelik) in terms of H2-rich syngas production from biomass gasification. In order to achieve this goal, an ASPEN plus-based model for biomass gasification integrated with carbonation reaction was developed. Tar formation was also considered and the gasification process was carried out based on Gibbs free energy minimization. A combined effect of temperature (600-710 °C), steam/biomass ratio, S/B (0.58-1.58), and limestone/biomass ratio, L/B (0-2.0) on gas composition, H2 yield (HY) and gas yield (GY) was also studied. An increase in both S/B and L/B was beneficial for H2 enrichment. The CO2 content declined sharply from 16.83 vol% to 10.28 vol% with increasing L/B from 0 to 1.5; however, a marginal reduction in CO2 content was observed with further increase in L/B. The highest HY (51.01 g/kg) was produced with Dikmen followed by Göynük, Polatlı Yolu, Kınık Tüneli and Köserelik. The results also showed that the limestone samples with high CaO content in general exhibits a better H2 production capacity than limestones with low CaO content. To the best of our knowledge, no simulation study has been presented to compare the catalytic activity of different limestones in terms of H2 production.

In-situ plasma assisted lithium-ion battery cathodes to catalytically pyrolyze lignin for H2-rich syngas production

In-situ plasma assisted lithium-ion battery cathodes catalysis was investigated to pyrolyze lignin to H2-rich syngas, oil and char. The effects of temperature, cathode to lignin ratio and plasma current on syngas production were investigated by using the typical ternary cathode NCM111 (LiNi1/3Co1/3Mn1/3O2) as catalyst and adopting dielectric barrier discharge mode. Response surface methodology based on BOX-BEHNKEN design was used to analyze the significance and interactions of process factors on the syngas yield. The conditions of 837℃, 10.4 %, and 185 mA for obtaining high-yield syngas (22.58 %) were more stringent; thereinto, from high to low, the intensity of factors on the yield was temperature, plasma current, and cathode ratio. Furthermore, different cathodes (non-cathode, NCM811 (LiNi4/5Co1/10Mn1/10O2), LCO (LiCoO2), and LMO (LiMn2O4)) were applied to decouple the catalytic effects of three metals in the NCM111. NCM111 enhanced both lignin gasification and carbonization by reducing condensable components, and NCM811 further improved gasification, but LCO and LMO had weaker gasification ability. NCM111 increased H2 volume fraction from 22.35 % to 67.31 %, NCM811 elevated the micro-discharge performance, promoting the hydrogasification reactions between energetic H species and char to produce more CH4, while LCO and LMO tended to produce the CO-rich syngas. Besides, in-situ plasma and its synergy with cathodes inhibited the formation of heavy aromatics and produced some high-value bio-oils rich in light aromatics, in which NCM111 achieved 92.30 % selectivity towards MAHs. High Ni ratio was beneficial for improving the char porosity, and the chars obtained by using NCM811 had a surface area of 409.29 m2/g, and a pore volume of 0.401 cm3/g. Comparably, the degree of catalytic lignin gasification for preparing H2-rich syngas could be ranked as Ni > Co > Mn in the ternary cathode.

Upcycling of hazardous plastic waste by CO2 transformation-enhanced steam reforming over MgO-promoted Ni/C bifunctional catalyst

Disposing hazardous plastic waste (e.g., used masks) poses a challenging issue, as these waste plastics often carry the risk of virus infection. CO2 transformation-enhanced steam reforming (CTESR) route was developed and newly synthesized dual-support Ni bifunctional catalysts were explored for the upcycling of disposed mask. Among the single-support Ni catalysts, Ni/CaO presented a high H2 yield (52.18 mmol/g), but it was inferior to Ni/MgO and Ni/C in terms of CO2 transformation capacity. Importantly, Ni/MgO demonstrated the lowest carbon deposition (∼2.67 wt%) due to the interaction between MgO and NiO, forming a NiO-MgO solid solution. In this sense, dual-support Ni catalysts were prepared to achieve extensive H2 production and CO2 reduction. Dual-support Ni/MgO-C was superior to other dual-support catalysts in terms of H2 selectivity (57.77 vol%), H2 yield (51.58 mmol/g), CO2 emission (1.72 mmol/g), and H2 production efficiency (ƞ: 0.74 g CO2/g H2). Moreover, it presented a remarkable synergistic effect on H2 yield and production efficiency, with an enhancement of 117.27 % and 32.58 %, respectively. The super catalytic performance was attributed to the unique properties of Ni/MgO-C, high dispersion of Ni/NiO active core, and proper interaction of Ni/NiO with the dual supports. In addition, MgO-promoted Ni/C catalysts with multiple MgO proportions were examined. Ni/MgO5-C5 was identified as the optimal bifunctional catalyst for H2-rich syngas production and CO2 elimination. Overall, this study established a highly effective and promising route by using dual-support Ni catalysts for upcycling hazardous plastic waste into H2-rich syngas while suppressing CO2 emission.

Co-gasification behavior and products distribution of wet sewage sludge and corn stalks: Effect and mechanism analysis of self-moisture utilization

Wet sewage sludge (WSS) self-moisture gasification is a promising route for H2-rich syngas production. This research investigated the co-gasification of WSS and corn stalks (CS), focusing on the effects of self-moisture content. Thermogravimetric analysis of the pyrolysis of the mixture (WSS:CS = 40:60 wt%) revealed that the reactions followed a three-parallel-reaction model. The co-gasification process was performed to compare the effects of self-moisture and external steam used as gasification agents, respectively. The results showed that the self-moisture gasification led to higher H2 yields (0.057–0.11 L/g), gas yields (0.19–0.21 L/g), and specific gas energy (2.62–2.72 MJ/kg) than those in external steam gasification (0.055–0.090 L/g, 0.16–0.18 L/g and 2.32–2.52 MJ/kg, respectively). Additionally, self-moisture gasification also resulted in lighter tar with primarily light organic acids (28.0%), and char with weaker aromatic structure features, attributed to longer reaction time during diffusion of pyrolysis products. Overall, this study provided theoretical foundations for the high-value exploitation of WSS.

Long-term evaluation of palm oil mill effluent (POME) steam reforming over lanthanum-based perovskite oxides

To replace the obsolete ponding system, palm oil mill effluent (POME) steam reforming (SR) over net-acidic LaNiO3 and net-basic LaCoO3 were proposed as the POME primary treatments, with promising H2-rich syngas production. Herein, the long-term evaluation of POME SR was scrutinized with both catalysts under the optimal conditions (600 °C, 0.09 mL POME/min, 0.3 g catalyst, & 74–105 μm catalyst particle size) to examine the catalyst microstructure changes, transient process stability, and final effluent evaluation. Extensive characterization proved the (i) adsorption of POME vapour on catalysts before SR, (ii) deposition of carbon and minerals on spent SR catalysts, and (iii) dominance of coking deactivation over sintering deactivation at 600 °C. Despite its longer run, spent LaCoO3 (50.54 wt%) had similar carbon deposition with spent LaNiO3 (50.44 wt%), concurring with its excellent coke resistance. Spent LaCoO3 (6.12 wt%; large protruding crystals) suffered a harsher mineral deposition than spent LaNiO3 (3.71 wt%; thin film coating), confirming that lower reactivity increased residence time of reactants. Transient syngas evolution of both SR catalysts was relatively steady up to 4 h but perturbed by coking deactivation thereafter. La2O2CO3 acted as an intermediate species that hastened the coke removal via reverse Boudouard reaction upon its decarbonation. La2O2CO3 decarbonation occurred continuously in LaCoO3 system but intermittently in LaNiO3 system. LaNiO3 system only lasted for 13 h as its compact ash blocked the gas flow. LaCoO3 system lasted longer (17 h) with its porous ash, but it eventually failed because KCl crystallites blocked its active sites. Relatively, LaCoO3 system offered greater net H2 production (72.78%) and POME treatment volume (30.77%) than LaNiO3 system. SR could attain appreciable POME degradation (>97% COD, BOD5, TSS, & colour intensity). Withal, SR-treated POME should be polished to further reduce its incompliant COD and BOD5.

Prediction of syngas properties of biomass steam gasification in fluidized bed based on machine learning method

Steam gasification of biomass is a promising technology to produce hydrogen-rich syngas. While the complex correlation between gasification process and syngas properties has not been effectively explained. In this study, 222 relevant experimental data from peer-reviewed publications was collected to predict the syngas properties in fluidized bed reactors by machine learning (ML) method. Five algorithms were adopted and the Extreme Gradient Boosting regression (XGBoost) showed the most consistent predictive performance with the testing R2 of 0.89–0.92. The equivalent ratio (ER) and steam to biomass ratio (S/B) were the most significant determinants of H2 concentration. Optimal H2 production (around 45%) was achieved by favorably choosing operating conditions characterized by the range of ER < 0.08 and 1 < S/B < 2.5. The valuable insights provided by ML models may contribute to the better understanding of biomass steam gasification process for the H2-rich syngas production.

Tailoring strontium-promoted alumina-zirconia supported Ni-catalysts for enhanced CO2 utilization via dry reforming of methane: Sr loading effects and process optimization

An urgent need exists in the dry reforming of methane (DRM) community for a cost-effective and high-performance catalyst system to facilitate the industrial production of H2-rich syngas. In this study, we propose a catalyst composed of a 10 wt% ZrO2-90 wt% Al2O3 support, Ni as active sites, and a strontium promoter, which offers a promising solution. Characterization of the 5NixSr/10Zr+Al catalyst series (x = 0–4 wt%) was conducted using XRD, surface area and porosity analysis, and TPR, TPO, TPD techniques, revealing the stability of metallic Ni derived from the reduction of "moderately interacted NiO-species" under oxidizing-reducing conditions. Incorporating 3 wt% Sr in the 5Ni/10Zr+Al catalyst enhanced reducibility and promoted efficient oxidation of carbon deposits by CO2. The resulting 5Ni3Sr/10Zr+Al catalyst exhibited additional strong basic sites, leading to ∼82% H2 yield and effective inhibition of parallel H2-consuming reactions. Remarkably, the H2 yield remained stable at ∼79% over a 51-hour time on stream, while process optimization using response surface methodology yielded an optimized H2 yield of 89% under specific conditions. Experimental validation demonstrated an H2 yield of 87.4% with excellent stability for a 10-hour time on stream. Overall, the proposed catalyst system demonstrates cost-effectiveness, high performance, and stability, making it a promising candidate for DRM applications.

Fluidized bed gasification of wood chips using bottom ash derived from coal: optimization of operating conditions

ABSTRACT Although biomass gasification is well recognized as a practical method for producing syngas, the generated gas cannot be used in a variety of applications because of technological issues like tar formation. In this research, coal bottom ash (CBA) was used as an in-bed material for the experimental examination of biomass (wood chips) gasification in a fluidized bed system. All tests were conducted at reaction temperatures between 750 and 900 C, steam to biomass ratios between 0.24 and 0.96, CBA particle sizes between 0.22 and 1.2 mm, and biomass particle sizes between 0.5 and 3.0 mm. The primary objective of this research is to use an experimental set-up to assess the effectiveness of steam gasification of biomass using CBA with various particle sizes. The findings showed that using steam as a gasification agent and raising the temperature improved tar cracking and H2 generation. The findings also demonstrated that the catalyst particle size is efficient for H2 production and that CBA can be used as an in-bed material for the production of H2-rich syngas. Under an 850°C reaction temperature, a S/B of 0.96, a CBA size of 0.2–0.4 mm (Case I), and a biomass particle size of 0.5–1.2 mm, the H2 concentration achieved a maximum of 65.7 vol%. (Case I).

Catalytic pyrolysis of waste cooking oil for hydrogen-rich syngas production over bimetallic Fe-Ru/ZSM-5 catalyst

Waste cooking oil (WCO) energy development offers an effective method for producing renewable fuels, enabling simultaneous resource recovery and pollution reduction. This study aims to develop a novel bimetallic Fe(Ni)-Ru/ZSM-5 catalyst toward H2-rich syngas production from WCO. The results show that Fe-Ru/ZSM-5 produced a higher maximum H2 yield (84.05 μmol·gcat.−1·s−1) than did Ni-Ru/ZSM-5 (41.76 μmol·gcat.−1·s−1) when fed at a 50 L/min rate at an optimal temperature of 700 °C. Fe-Ru/ZSM-5 presented a more prolific microporous distribution, whose structure contributes to the diffusion of the short-chain hydrocarbon intermediate reactants to enhance hydrogen production. Fe(III) can help to improve the conversion ratio of benzene and the anti‑carbon deposition capability of the catalyst. The dealumination and oxidation decreases the stability of the catalyst and may lead to inactivation. Furthermore, this study discusses the mechanism of bimetallic-loaded catalysts combining noble metals with transition metals in WCO pyrolysis. The results point to effective new approaches to increase H2 production through the catalytic pyrolysis of WCO.

H2-rich syngas production from biogas reforming: Overcoming coking and sintering using bimetallic Ni-based catalysts

Dry reforming of methane is a very appealing catalytic route biogas (mainly composed by greenhouse gases: carbon dioxide and methane) conversion into added value syngas, which could be further upgraded to produce liquid fuels and added value chemicals. However, the major culprits of this reaction are coking and active phase sintering that result in catalysts deactivation. Herein we have developed a highly stable bimetallic Ni–Rh catalyst supported on mixed CeO2–Al2O3 oxide using low-noble metal loadings. The addition of small amounts of rhodium to nickel catalysts prevents coke formation and improves sintering resistance, achieving high conversions over extended reaction times hence resulting in promising catalysts for biogas upgrading.

Utilization of fruit waste for H2-rich syngas production via steam co-gasification with brown coal

In this work, to efficiently utilize waste fruit and low-rank coal for the hydrogen (H2)-rich syngas production, steam co-gasification of banana peel (BP) and brown coal (BC) was studied in a fixed-bed reactor. The results showed that the gasification rate of BC was highly enhanced after mixing it with BP and the obvious synergistic effect was observed in all investigated three mixing weight ratios (i.e., 1:1, 1:4, 4:1), resulting in a higher carbon conversion as well as a H2-rich gas production yield for the co-gasification. However, the extent of promotion by synergistic effect was affected by the reaction temperature, mixing ratio, and steam amount. It was found that the high potassium (K) species content in the BP provided the catalytic effect not only on water–gas shift reaction but also on tar reforming/cracking, thereby enhancing the gasification of BC. In addition, it is confirmed that steam should be an important factor to promote the synergistic effect and H2-rich gas production.

Chemical Kinetic Modeling of Air-Steam Gasification of Eucalyptus Wood Sawdust for H2-Rich Syngas Production.

The aim of this research paper is to develop a chemical kinetic model, based on the mechanism of surface reactions, for air-steam gasification of eucalyptus wood sawdust (CH1.63O1.02) and analyze the hydrogen-rich syngas production. Experiments are performed on a bubbling fluidized-bed gasifier using air-steam as a gasifying agent. For validation of the developed kinetic model, the outcome of the model is compared with that of experimental data, which shows a root-mean-square error of less than 4. Different parameters such as equivalence ratios (0 ≤ ER ≤ 0.4), particle size (100 ≤ Dp ≤ 1000 μm), gasification temperature (900 ≤ T ≤ 1200 K), pressure (1 ≤ P ≤ 20 atm), and steam-to-biomass ratio (0 ≤ SBR ≤ 2) are considered for the analysis. The one-parameter-at-a-time concept is employed to maximize the production of H2-rich syngas. Results indicate that the maximum concentration of hydrogen is 55.04 vol % (experimental) and 51.81 vol % (predicted) at optimum conditions: ER = 0, Dp = 100 μm, T = 1100 K, P = 1 atm, and SBR = 0.75. Gasification performance parameters such as hydrogen gas yield, heating values, cold gas efficiency, etc., are evaluated.

Hydrogen-rich syngas production from the lignocellulosic biomass by catalytic gasification: A state of art review on advance technologies, economic challenges, and future prospectus

Global population growth, modernization, and industrialization have all significantly increased energy consumption, which has worsened the climate and led to greenhouse gas emissions, forcing researchers to look into eco-friendly, renewable, and sustainable energy sources. Hydrogen (H2) is emerging as one of the cleanest and most carbon-free future energy carriers generated from diverse domestic resources, organic wastes, lignocellulosic biomass, natural gas, and fossil fuels by biochemical and thermochemical routes. Applying thermochemical routes, lignocellulosic biomass for sustainable H2 production have shown great potential for industrial implementation. As a result, the current study emphasizes the state-of-the-art review of developments in gasification technologies, operating circumstances, and catalysts employed for producing H2-rich syngas. Emerging catalytic technologies to improve H2-rich syngas production were discussed in detail. New technologies including, solar gasification, microwave gasification, plasma gasification, and integrated pyrolysis-gasification were also highlighted. Finally, the prospects and challenges of the process are also pointed out in brief to assist future researchers and stakeholders working for its commercialization.

Gasification integrated with steam co-reforming of agricultural waste biomass over its derived CO2/O2/steam-mediated porous biochar for boosting H2-rich syngas production

This study proposed a novel concept of producing H2-rich syngas and eliminating tar formation via biomass gasification integrated with inline steam co-reforming (BGSCR). Initially, direct gasification of wheat straw in diverse gasifying agents was conducted to produce CO2/O2/steam-mediated porous biochar materials (PBMs), which were innovatively used as catalytic reforming agents and co-reactants for BGSCR process. With the aid of gasifying agents, the surface structures of PBMs were apparently fabricated with more micropores. Particularly, C[steam] achieved the highest surface area (502 m2/g) and total pore volume (0.297 cm3/g). Further, catalytic reforming temperature and type of PBMs were examined in relation to gas formation behaviors during BGSCR process. The maximum gas yield (58.53 mmol/g), H2 yield (28.29 mmol/g), and syngas yield (45.96 mmol/g) were achieved in the presence of C[10%O2]. Simply put, this study presents a promising gasification route to directly integrate H2-enriched syngas generation and in-situ tar abatement with biochar reutilization.

H2-rich syngas production from gasification involving kinetic modeling: RSM-utility optimization and techno-economic analysis.

In this research article, H2 rich syngas production is optimized using response surface methodology (RSM) and a utility concept involving chemical kinetic modeling considering eucalyptus wood sawdust (CH1.63O1.02) as gasification feedstock. By adding water gas shift reaction, the modified kinetic model is validated with lab scale experimental data (2.56 ≤ root mean square error ≤ 3.67). Four operating parameters (i.e., particle size "d p", temperature "T", steam to biomass ratio "SBR", and equivalence ratio "ER") of air-steam gasifier at three levels are used to frame the test cases. Single objective functions like H2 maximization and CO2 minimization are considered whereas for multi-objective function a utility parameter (80% H2 : 20% CO2) is considered. The regression coefficients (R H2 2 = 0.89, R CO2 2 = 0.98 and R U 2 = 0.90) obtained during the analysis of variance (ANOVA) confirm a close fitting of the quadratic model with the chemical kinetic model. ANOVA results indicate ER as the most influential parameter followed by T, SBR, and d p. RSM optimization gives H2|max = 51.75 vol%, CO2|min = 14.65 vol% and utility gives H2|opt. = 51.69 vol% (0.11%↓), CO2|opt. = 14.70 vol% (0.34%↑). The techno-economic analysis for a 200 m3 per day syngas production plant (at industrial scale) assured a payback period of 4.8 (∼5) years with a minimum profit margin of 142% when syngas selling price is set as 43 INR (0.52 USD) per kg.

The synergistic role of Ni-Co bimetallic catalyst for H2-rich syngas production via glycerol dry reforming

A by-product of biodiesel manufacturing, glycerol, is known for its potential to generate syngas via the glycerol dry reforming (GDR) reaction. This study evaluates monometallic and bimetallic Nickel–Cobalt (Ni–Co) (with 15%Co, 3%Ni–12%Co, 4.5%Ni-10.5%Co, 7.5%Ni-7.5%Co, 10.5%Ni-4.5%Co and 15%Ni loading) on Alumina (Al2O3) support extracted from aluminium dross. The catalysts were prepared using an ultrasonic-assisted impregnation process and used in GDR at temperatures ranging from 873 to 1173 K at stoichiometric feed ratio. Analyses result showed that the diluting impact of Ni–Co bimetallic precursors resulted in a reduction of metal crystallite size and improved H2 and CO2 uptake. The conversion of glycerol and product yield were in the order of 3%Ni–12%Co/Al2O3 > 4.5%Ni-10.5%Co/Al2O3 > 7.5%Ni-7.5%Co/Al2O3 > 10.5%Ni-4.5%Co/Al2O3 > 15%Co/Al2O3 > 15%Ni/Al2O3, with 3%Ni–12%Co/Al2O3 having values of 75.6%, 64.7% and 44.8%, for glycerol conversion, H2 and CO yield respectively. All catalysts achieved product ratios ranging from 1.20 to 1.44. The high oxygen vacancies in Ni–Co bimetallic catalysts aided the reduction of carbon formation. Enhanced Ni–Co particles dispersion on Al2O3 support reduced the agglomeration of metal particles, thus, creating smaller crystallite size. The changes in binding energy peaks of Ni and Co were indicative of strong electronic interaction which created Ni–Co bimetallic alloys. 3%Ni–12%Co was regarded as the best catalyst for this study since it was effective in enhancing the conversion of glycerol and product yield.

H2-rich syngas production from pyrolysis of agricultural waste digestate coupled with the hydrothermal carbonization process

A novel process to produce a H2-rich syngas from a high moisture-containing agricultural waste digestate is proposed. This process combines the use of hydrothermal carbonization (HTC), dewatering, pyrolysis, and catalytic reforming. Due to the feature of the high moisture content in the digestate, the effect of the HTC and dewatering on the process performance is of interest, and four scenarios were considered. Furthermore, three pyrolytic temperatures were chosen to understand the effect of pyrolysis conditions on the produced H2-rich syngas. A life cycle assessment was conducted to investigate the environmental impact of the proposed process. Results show that the application of HTC technology, increases the process efficiency, produces less syngas from one ton of digestate, lowers the cumulative energy demand and the negative carbon emissions. When the dewatering technology is used, the syngas yield is promoted but the H2 concentration in the syngas is reduced. The H2 to CO molar ratio reaches the maximum value of 9.2 when using a 450 ˚C pyrolysis temperature, by only using HTC. When the combining process of HTC and dewatering is used, it results in the highest process efficiency, but the smallest relative negative CO2 equivalent emissions by treating one ton of dry digestate.