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The alarming global warming issue has sparked interest in researchers to mitigate greenhouse gas emissions via CO 2 reforming of CH 4 (CRM). Regrettably, the main drawback of CRM is catalyst deactivation because of coking and metal sintering. Therefore, exceptional resistance towards coking and sintering is crucial to formulate viable CRM catalysts. This article reviewed the latest development of nanosilica-based catalysts (mesoporous nanosilica, dendritic fibrous nanosilica, green nanosilica, and core@shell nanosilica) for CRM application. The physicochemical properties of nanosilica supports could be modulated by synthesis methods to improve their resistance towards coking and sintering. Furthermore, this review compiled the influence of catalytic properties of nanosilica supported catalysts, such as active metal dispersion, crystallite size, acid-basic properties, oxygen mobility, reducibility, porosity, and morphology on CRM. To conclude, nanosilica supports with strong metal-support interaction, homogeneous metal dispersion, appropriate crystallite size, and moderate acidity/basicity, exhibited satisfactory catalytic activity, thermal stability, and resistance towards coking and sintering. The fundamental study and depth understanding on this catalysis field is of worth in configuring robust catalysts for future industrial applications success of CRM reaction with superb activity and carbon resistance for CRM. [Display omitted] • Nanosilica supports are preferred due to their high thermal stability and porosity. • Type of nanosilica supports: mesoporous, dendritic fibrous, and core@shell. • Dendritic fibrous nanosilica has high accessible active sites and minor clogging. • Core@shell nanosilica has low internal diffusion resistance and confinement effect. • Coke management based on basic nature and oxygen storage capacity of the supports. [ABSTRACT FROM AUTHOR]

To replace the obsolete ponding system, palm oil mill effluent (POME) steam reforming (SR) over net-acidic LaNiO 3 and net-basic LaCoO 3 were proposed as the POME primary treatments, with promising H 2 -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 LaCoO 3 (50.54 wt%) had similar carbon deposition with spent LaNiO 3 (50.44 wt%), concurring with its excellent coke resistance. Spent LaCoO 3 (6.12 wt%; large protruding crystals) suffered a harsher mineral deposition than spent LaNiO 3 (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. La 2 O 2 CO 3 acted as an intermediate species that hastened the coke removal via reverse Boudouard reaction upon its decarbonation. La 2 O 2 CO 3 decarbonation occurred continuously in LaCoO 3 system but intermittently in LaNiO 3 system. LaNiO 3 system only lasted for 13 h as its compact ash blocked the gas flow. LaCoO 3 system lasted longer (17 h) with its porous ash, but it eventually failed because KCl crystallites blocked its active sites. Relatively, LaCoO 3 system offered greater net H 2 production (72.78%) and POME treatment volume (30.77%) than LaNiO 3 system. SR could attain appreciable POME degradation (>97% COD, BOD 5 , TSS, & colour intensity). Withal, SR-treated POME should be polished to further reduce its incompliant COD and BOD 5. [Display omitted] • Prolonged catalytic POME steam reforming over LaNiO 3 (13 h) and LaCoO 3 (17 h). • Similar carbon deposition of spent LaCoO 3 (50.54 wt%) and spent LaNiO 3 (50.44 wt%). • Harsher mineral deposition in spent LaCoO 3 (6.12 wt%) than spent LaNiO 3 (3.71 wt%). • Overall net H 2 production of LaCoO 3 system was 72.78% larger than LaNiO 3 system. • Total POME treatment volume of LaCoO 3 system was 30.77% higher than LaNiO 3 system. [ABSTRACT FROM AUTHOR]

Steam reforming (SR) of palm oil mill effluent (POME) over net-basic LaCoO 3 was optimised for syngas production ( F S y n g a s ) and degradation efficacies ( X P ) by tuning temperature (T), POME flow rate ( V ˙ P O M E ), catalyst weight ( W c a t ), and particle size ( d c a t ). Net-basicity of LaCoO 3 facilitated the adsorption of Lewis acid CO 2 , thereby assisted carbon removal via reverse Boudouard reaction. POME SR over LaCoO 3 was promoted by using (i) higher T (endothermicity), (ii) greater V ˙ P O M E (larger partial pressure at constant weight-hourly-space-velocity and total feed rate), (iii) larger W c a t (longer residence time for POME vapour), and (iv) smaller d c a t (higher surface area to volume ratio). Nevertheless, the catalytic activity of LaCoO 3 declined with (i) severe coking and sintering deactivation (T ≥973 K), (ii) carbon-encapsulation ( V ˙ P O M E = 0.10 mL/min), (iii) agglomeration ( W c a t >0.3 g), and (iv) pore occlusion ( d c a t <74 μm). Hence, the optimum conditions of POME SR over LaCoO 3 were T = 873 K, V ˙ P O M E = 0.09 mL/min, W c a t = 0.3 g, and d c a t = 74–105 μm. The optimised process able to produce syngas at a rate of 86.60 μmol/min whilst degrading POME to a less polluted liquid condensate (COD = 435 mg/L and BOD 5 = 62 mg/L). Image 1 • POME steam reforming was performed over net-basic LaCoO 3. • Net-basicity enhanced CO 2 adsorption for C-consuming reverse Boudouard reaction. • Optimum T = 873 K, V ˙ P O M E = 0.09 mL/min, W c a t = 0.3 g, and d c a t = 74–105 μm. • Optimised reaction gave 86.60 μmol H 2 -rich syngas/min. • Less polluted liquid condensate (COD = 435 mg/L and BOD 5 = 62 mg/L) was obtained. [ABSTRACT FROM AUTHOR]

In current paper, thermodynamics study of palm oil mill effluent (POME) steam reforming was performed to investigate its feasibility for syngas production. By using the minimization of total Gibbs free energy method, the thermodynamic simulation is executed to study the effect of reaction temperature (573–1173 K) on product yield (Y i) and syngas ratio (H 2 :CO). Based on preliminary analysis, the POME liquor composed of 99.73% water and 0.27% organic contents by mole. Complete conversion of POME's organic contents is accomplished regardless of reforming temperature. However, the equilibrium constant reveals that not every organic constituent in POME are reformed into syngas via steam reforming at ≤673 K, so their disappearance hints at the occurrence of thermal decomposition. The steam reforming of all organic contents in POME is only viable at ≥773 K. From POME steam reforming at 573–1173 K, H 2 -rich syngas (H 2 :CO ratio = 25–3457) is produced. For syngas production, the optimum temperature is 1073 K because it gives highest Y s y n g a s (58348 μmol syngas/mol POME) with a Q r e q u i r e d of 12.05 kJ/mol POME. In a nutshell, the POME steam reforming is an alluring process that viable for syngas production as it potentially mitigates the environmental issue inflicted by palm oil processing. • Thermodynamics analysis of POME steam reforming was completed for 573–1173 K. • Complete conversion of POME's organic contents regardless of reforming temperature. • Amelioration of all POME's organic contents into syngas viable at ≥773 K. • H 2 -rich syngas is generated from POME steam reforming. • Maximum Y s y n g a s (58348 μmol syngas/mol POME) accomplished at 1073 K. [ABSTRACT FROM AUTHOR]

This paper reports on the novel application of catalytic steam reforming process to convert palm oil mill effluent (POME) into syngas over a 20wt%Ni/80wt%Al 2 O 3 catalyst. The catalyst possessed high degree of crystallinity and was impurity-free, judging from the obtained XRD pattern. Furthermore, the BET specific surface area of catalyst was low (2.09 m2 g−1), consistent with smooth surface captured by the FESEM images. CO 2 -desorption and NH 3 -desorption profiles showed a presence of both acid and basic sites on the surface of catalyst. In the absence of catalyst, about 7.0% reduction of chemical oxygen demand (COD) was achieved at 6.0 mL h−1 flow rate of POME, reforming temperature of 873 K and 20 mL min−1 of N 2 -flow. Significantly, the COD reduction shot up to 93.7% in the presence of catalyst and liquid-hourly-space-velocity (LHSV) of POME of 90 mL h−1 g cat −1 at 873 K. The corresponding biochemical oxygen demand (BOD) reduction recorded was 93.8%. However, normalized carbon loss indicates that a high LHSV would favour carbon deposition. In addition to high LHSV, the carbon deposition was also influenced by reaction temperature. High reaction temperature has reduced carbon deposition, as well as organics removal. COD reduction was 99.41% and BOD reduction was 99.52% at 1173 K when LHSV was 60 mL h−1 g cat −1. In the gas phase, four species were consistently detected, viz. H 2 , CO 2 , CO and CH 4 , with H 2 as the major component. The H 2 selectivity increased with both LHSV and reaction temperature. • More than 99% of organics in POME was degraded in the presence of catalyst. • The H 2 selectivity increased with both LHSV and reaction temperature. • Carbon deposition was reduced at elevated reaction temperature. [ABSTRACT FROM AUTHOR]

Abstract Valorization of palm oil mill effluent (POME) over a sol-gel synthesized lanthanum nickel trioxide (LaNiO 3) catalyst via steam reforming pathway was investigated from 573 to 1173 K. The blank run (steam reforming) at 873–1173 K neutralized the acidic POME with complete total suspended solids (TSS) removal, which accomplished >88% chemical oxygen demand (COD) removal, >97% 5-days biochemical oxygen demand (BOD 5) removal, and >95% decolourization. From 773 K onwards, LaNiO 3 greatly enhanced syngas production from POME steam reforming. The principal role of LaNiO 3 was to enhance the syngas production. The XRD, FESEM-EDX, and TPO results of spent LaNiO 3 were also correlated with gaseous product profiles to scrutinize its catalytic effects. At an optimum temperature of 873 K, catalytic POME steam reforming over LaNiO 3 generated 73.91 μmol/min of H 2 -rich syngas (H 2 :CO ratio of 107.88). Withal, the aforesaid system was able to neutralize the acidic POME feedstock and eliminate its TSS content while reduced 98.38% COD, 99.10% BOD 5 , and 99.52% colour intensity. Graphical abstract Image 1 Highlights • POME was degraded by steam reforming over LaNiO 3 at 573–1173 K. • 773–1173 K granted complete neutralization and excellent degradation. • H 2 , CH 4 , CO 2 , and CO were released from the steam reforming of POME. • The optimum temperature of catalytic steam reforming of POME was 873 K. • 73.91 μmol/min of syngas (H 2 /CO ratio = 107.88) was generated at 873 K. [ABSTRACT FROM AUTHOR]

Abstract In this work, the syngas production rate ( F S y n g a s ) of LaNiO 3 -catalysed steam reforming of palm oil mill effluent (POME) was optimized with respect to POME flow rate ( V ˙ P O M E ), catalyst weight ( W c a t ), and particle size ( d c a t ). With a net acidity, the synthesized LaNiO 3 catalysed POME steam reforming by cracking the bulky compounds and valorising simpler intermediates into syngas. The degradation efficiencies ( X P ) were also evaluated by assessing wastewater parameters, viz. pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD 5), total suspended solids (TSS), and colour intensity (A). After steam reforming at 873 K, the liquid condensate has neutral pH and zero TSS. The parallel trend of F S y n g a s and X P verified syngas generation from degradation of POME's organics. At higher V ˙ P O M E (0.05–0.09 mL/min), greater POME partial pressure promoted its steam reforming and water gas shift, which enhanced catalytic performance. Beyond optimum V ˙ P O M E (0.09 mL/min), coke-forming Boudouard reaction deteriorated catalytic activity. Catalytic performance was boosted for a longer residence time at higher W c a t (0.1–0.3 g); nonetheless, it was reduced by agglomerated catalyst when W c a t > 0.3 g. Finer LaNiO 3 ( d c a t > 74 μm) with greater surface area to volume ratio exhibited better performance; however, ultrafine LaNiO 3 ( d c a t < 74 μm) had poor performance because of occluded pores. Remarkably, optimized POME steam reforming over LaNiO 3 (T = 873 K, V ˙ P O M E = 0.09 mL/min, W c a t = 0.3 g, d c a t = 74–105 μm) has generated 132.47 μmoL/min of H 2 -rich syngas, whilst achieved 99.53% X C O D , 99.88% X A , 99.75% X B O D 5 , and 100% X T S S . Graphical abstract Image 1 Highlights • POME steam reforming over LaNiO 3 was studied at 873 K and 1 atm. • Reaction was optimized at V ˙ P O M E = 0.09 mL/min, W c a t = 0.3 g, and d c a t = 74 – 105 μm. • At optimised conditions, 132.47 μmol/min of H 2 -rich syngas was generated. • The treatment can achieve 99.53% X C O D , 99.88% X A , 99.75% X B O D 5 , and 100% X T S S . [ABSTRACT FROM AUTHOR]

The current work describes a novel application of steam reforming process to treat palm oil mill effluent (POME), whilst co-generating H 2 -rich syngas from the treatment itself. The effects of reaction temperature, partial pressure of POME and gas-hourly-space-velocity (GHSV) were determined. High crystallinity 20 wt%Ni/80 wt%Al 2 O 3 catalyst with smooth surface was prepared via impregnation method. Baseline runs revealed that the prepared catalyst was highly effective in destructing organic compounds, with a two-fold enhancement observed in the presence of 20 wt% Ni/80 wt%Al 2 O 3 catalyst, despite its low specific surface area (2.09 m 2 g −1 ). In addition, both the temperature and partial pressure of POME abet the COD reduction. Consequently, the highest COD reduction of 99.7% was achieved, with a final COD level of 73 ± 5 ppm from 27,500 ppm, at GHSV of 40,000 mL/h.g cat and partial pressure of POME equivalent to 95 kPa at 1173 K. In terms of gaseous products, H 2 was found to be the major component, with selectivity ranged 51.0%–70.9%, followed by CO 2 (17.7%–34.1%), CO (7.7%–18.4%) and some CH 4 (0.6%–3.3%). Furthermore, quadratic models with high R 2 -values were developed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel solar-driven biomass chemical looping gasification system is studied. • The system achieves a carbon-gas yield of 0.69 and an energy upgrade factor of 0.71. • The fuel reactor produced CH 4 , CO, CO 2 and H 2 at 0.63, 11.86, 8.85, and 18.53 mmol/g. • High-purity H 2 is produced at 7.17 mmol/g in a separated stream. • Fayalite is found as a byproduct due to the interaction between reactants. A novel solar-driven biomass chemical looping gasification (SBCLG) system was proposed and experimentally demonstrated for the co-production of pure hydrogen and syngas from biomass wastes using high-flux solar irradiation. In this system, a steam reactor and a solar fuel reactor were adopted to replace the air and fuel reactors in a typical biomass chemical looping gasification (BCLG) system, respectively. The SBCLG exhibits two advantages over BCLG: (1) the syngas yield is raised as the high-temperature process heat is provided by solar radiation rather than biomass combustion, and (2) a pure hydrogen stream is generated in addition to the syngas stream, which allows a flexible adjustment of the carbon-to-hydrogen ratio for downstream chemical processes. This study marked the first demonstration of a complete cycle of SBCLG in a cavity-type packed-bed solar reactor under simulated high-flux solar irradiation. Magnetite (Fe 3 O 4) was circulated between the steam reactor and the solar fuel reactor as the oxygen carrier (OC). The optimal operational parameters, the reaction temperature and solid contact pattern, were first determined in preliminary experiments in an electric furnace. Then, the effect of biomass to oxygen carrier mass ratio (m RH : m OC) on the key performance indicators was also investigated in a solar reactor. When m RH : m OC = 1:2, the highest values of the average carbon-gas yield of 0.69 ± 0.05 and energy upgrade factor of 0.71 ± 0.04 were achieved. The solar fuel reactor produced CH 4 , CO, CO 2 and H 2 at 0.63, 11.86, 8.85, and 18.53 mmol/g biomass, respectively, with the steam reactor yielding high-purity H 2 at 7.17 mmol/g biomass. The results indicated that the SBCLG is a viable method for co-production of pure hydrogen and syngas in separate streams. [ABSTRACT FROM AUTHOR]