Photocatalytic conversion of carbon dioxide to methanol over different precursors of graphitic carbon nitride supported on fibrous silica iron

In this study, the graphitic carbon nitride (g-C3N4) was successfully synthesized through thermal polymerization under three different g-C3N4 precursors such as urea (U-gC3N4), melamine (M-gC3N4) and dicyandiamide (D-gC3N4) and then doped into the fibrous silica iron (FSFe), denoted as U-gC3N4/FSFe, MgC3N4/FSFe, and D-gC3N4/FSFe, respectively. The synthesized catalysts were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis/DRS) and also tested for photocatalytic conversion of carbon dioxide (CO2) to methanol (CH3OH). The study indicated that altering the precursors had a substantial impact on the physicochemical features of the FSFe, which in turn increased the catalytic performance of the conversion of CO2 to CH3OH. U-gC3N4/FSFe exhibits the highest CH3OH yield (2.3 x 104 µmol gcat−1) compared to bare FSFe, D-gC3N4/FSFe and M-gC3N4/FSFe under visible light irradiation within 240 min. The higher CH3OH yield over U-gC3N4/FSFe is mostly owing to the lower bandgap energy of U-gC3N4/FSFe, as well as the advantageous interaction between g-C3N4 and FSFe

Insight into the development of silica-based materials as photocatalysts for CO2 photoconversion towards CH3OH : A review and recent progress

High exploitation of fossil fuel energy has resulted in substantial CO2 emissions into the atmosphere, leading to severe global warming. Tremendous strategies have been developed to explore possible approaches in minimizing the content of CO2 in the atmosphere. CO2 photoconversion into CH3OH has been put forward as a promising strategy since anthropogenic CO2 is utilized to generate valuable CH3OH assisting by clean solar energy. Silica-based materials have emerged as potential candidates for photocatalysts is accredited to their mesoporous framework with a large surface area, flexible tunability pore sizes, excellent thermal stability, and capability to suppress metal particle growth. Thus, this review encompasses the current progress on applying and developing silica-based materials as photocatalysts for CO2 photoconversion into CH3OH. Apart from that, fundamental aspects of the mechanism, the factors affecting performance, and the efficiency of silica-based materials in CO2 photoconversion to CH3OH are also comprehensively highlighted. The difficulties and prospects of CO2 photoconversion into CH3OH via silica-based materials are also discussed. In general, the most recent scenarios recommended further investigation to explore these materials since CO2 photoconversion to CH3OH has not been adequately investigated in the literature

Mesoporous alumina : A comprehensive review on synthesis strategies, structure, and applications as support for enhanced H2 generation via CO2-CH4 reforming

Lately, the generation of hydrogen out from carbon dioxide (CO2) - methane (CH4) reforming has been touted as a feasible option for reducing two of the most harmful greenhouse gases (CO2 and CH4) in the atmosphere. However, this technology typically suffered from catalyst deactivation triggered by sintering and coke deposition. Therefore, designing a feasible catalyst by making efficient support selections is vital for overcoming this challenge. Mesoporous alumina (MA) has aroused great attraction attributed to their potential applications as catalysis supports resulted from their high surface areas combined with tunable, narrow, and uniform pore size distribution, as well as their ability to constrain active metal from sintered and deactivated during the reaction. These materials' morphology, composition, and pore structure can be directly tailored during synthesis by altering the synthesis parameters like the type of the surfactants/templates employed, pH conditions, or selection of alumina precursors. As a result, this review's major focus is on synthesizing unique MA using a range of synthesis routes and conditions. Apart from that, this review also focuses on the applications and performance of MA as catalyst support during the CO2-CH4 reforming. We believe that this effort provides the complete grasp of MA contribution towards improving the CO2-CH4 reforming activity

Kinetic exploration of CO2 methanation over nickel loaded on fibrous mesoporous silica nanoparticles (CHE-SM)

A novel series of nickel (Ni) loaded on Fibrous Mesoporous Silica Nanoparticles (CHE-SM) support with varying Ni contents (x=1–30 wt%) were synthesized, denoted as xNi/CHE-SM and then investigated for carbon dioxide (CO2) methanation. The catalysts underwent comprehensive characterization using XRD, N2 adsorption-desorption, FESEM, FTIR-KBr, H2-TPR, and CO2-TPD techniques. The XRD and FESEM analyses confirmed the structural integrity of CHE-SM, irrespective of the Ni loading. However, the size of the nanocrystalline NiO particles appeared to be influenced by the Ni loading. Notably, 20Ni/CHE-SM exhibited the highest CO2 conversion of 92% at 350 °C, demonstrating its potential for low-temperature activation. H2-TPR and CO2-TPD results revealed favorable NiO reduction at lower temperatures, indicating medium-strength basicity that facilitated efficient CO2 and H2 adsorption and activation. Consequently, 20Ni/CHE-SM exhibited superior catalytic performance compared to other catalysts, with lower activation energy (61.5 kJ/mol). Kinetic studies focusing on 20Ni/CHE-SM indicated a molecular adsorption mechanism of CO2 and H2 on a single site after evaluation using four Langmuir-Hinshelwood models. This result was attributed to the high amount of medium strength basicity possessed by the 20Ni/CHE-SM catalyst which provided an abundance of adsorption sites, resulting in greater fractional coverage of reactants and enhancing the CH4 formation rate

Cobalt-based catalysts for hydrogen production by thermochemical valorization of glycerol: a review

Rising energy needs and the exhaustion of fossil fuels are calling for renewable fuels such as dihydrogen (H2), commonly named 'hydrogen.' Biomass treatment produces glycerol, which can be further used to generate dihydrogen or syngas. Here, actual challenges comprise the design of efficient and economically viable catalysts for attaining high hydrogen yield and minimizing coke deposition. Here, we review glycerol valorization routes for hydrogen or syngas generation, such as pyrolysis, steam reforming, aqueous phase, dry, supercritical water, partial oxidation, and autothermal reforming. We focus on cobalt-based catalysts due to their high availability, low cost, thermal stability, and coke resistance. The efficiency of cobalt-based catalysts can be improved by modifying textural properties, particle size and distribution, the strength of metal–support interaction, surface acidity and basicity, oxygen mobility, and reducibility. Such improvements have led to 100% glycerol conversion, 90% dihydrogen yield, and coke deposition of about 0.05%

Optimization of boron dispersion on fibrous-silica-nickel catalyst for enhanced CO2 hydrogenation to methane

There are numerous reports regarding boron-containing catalysts for hydrogen-related reactions from CO2 including dry reforming of methane and methanation. Besides enhancing the productivity, boron also improved nickel activity and stability. However, the detailed mechanistic study, particularly in explaining the starring role of boron in the enhanced reactions, is still lacking. Thus, herein we loaded boron on fibrous-silica-nickel and investigated their physicochemical properties and mechanistic route by means of in-situ FTIR for enhanced CO2 methanation. It was found that the appropriate dispersion of boron surrounds the nickel particles is an important factor to improve the adsorption of CO2 before interacting with split hydrogen atom from the nickel sides to form intermediates which are subsequently dehydrated, and then serial hydrogenation gave the final product of methane. Boron also accelerated the methanation and restricted coke formation. A hybrid approach on optimization via a face-centered central composite design and a response surface methodology showed that reaction using H2/CO2 ratio of 6, GHSV of 10,500 mL g−1 h−1, at 500 °C gave the highest percentage of CH4 of 84.3%. To indicate the error, the predicted values were compared to the experimental values, yielding an accurately minimal error ranging from 0 to 11%. As a result, the empirical models generated for CO2 hydrogenation to methane were reasonably accurate, with all actual values for the confirmation runs fitting within the 94% prediction interval

Catalytic biohydrogen production from organic waste materials: a literature review and bibliometric analysis

Global population growth and accelerated urbanisation have resulted in massive amounts of fossil fuel use and waste production. Because of its high energy content, pure nature, and fuel quality, hydrogen fuel is a viable option to fossil fuels. Biohydrogen from agricultural waste, in particular, piques concern because it generates hydrogen while still disposing of waste. This review conducted a bibliometric analysis of biohydrogen production from organic waste to trace the research trends and hotspots based on the literature in the Web of Science (WOS) database from 1970 to 2020. The present review article also focuses on highlighting various processes for converting organic waste into hydrogen, raw materials for biohydrogen production, and catalysts that could distil the latest perceptions that could shed light on a route advancing for successful catalyst design. It also seems that some intentions have been paid on studying waste materials such as pure polysaccharides, disaccharides, and monosaccharides. Among all the catalysts used, non-noble and low-cost active metals over reduced graphene oxide (rGO) support can significantly affect the activity of fermentative hydrogen production from organic waste materials. However, researches focusing on developing anaerobic membrane bioreactors for these technologies are still needed

Platinum-promoted fibrous silica Y zeolite with enhanced mass transfer as a highly selective catalyst for n-dodecane hydroisomerization

A fibrous silica zeolite Y (HY@KCC-1) catalyst with a high surface area of 568 m2/g and unique core-shell morphology was successfully synthesized via a modified KCC-1 synthesis method. Characterization of the catalysts was achieved with X-ray powder diffraction (XRD), field emission scanning microscope (FESEM), N2 adsorption/desorption, and 2,6-dimethylpyridine adsorbed Fourier-transform infrared spectroscopy (FTIR). The Pt/HY@KCC-1 has displayed complete n-dodecane conversion coupled with an incredibly enhanced isomer yield of 72% at 350°C, nearly two-fold higher than that of unmodified Pt/HY catalyst. Remarkably, Pt/HY@KCC-1 had an internal effectiveness factor (η) of unity and negligible internal diffusion limitation, thus suggesting its potential application in hydroisomerization of higher hydrocarbons for enhancing fuel properties

Conversion of polyethylene terephthalate plastic waste and phenol steam reforming to hydrogen and valuable liquid fuel: Synthesis effect of Ni–Co/ZrO2 nanostructured catalysts

Ni–Co/ZrO2 (NCZ) nano-structure catalysts prepared by the hydrothermal method (NCZ-hyd) and conventional impregnation (NCZ-imp) method. The comparative catalytic activity and coke resistance for each prepared catalyst were examined in steam reforming of phenol and polyethylene terephthalate (PET) plastic waste. The Physico-chemical catalysts properties were characterized by N2-adsorption, XRD, FTIR, TEM, SEM, EDX, H2-TPR, CO2-TPD, and TGA. The effects of preparation methods of NCZ nano-structure catalyst on the catalytic performances in PET-phenol steam reforming were investigated. The NCZ-hyd nanostructure catalyst exposed more outstanding catalytic activity and more excellent coke resistance in comparison with the NCZ-imp. The experimental findings exhibited that catalyst synthesized by hydrothermal method were uniform with the size of 8.8 nm, while NCZ particles prepared by conventional impregnation method were un-uniform, unshaped, and agglomerated, and the size distribution of its particles was from 25 to 50 nm. PET-Phenol conversion and hydrogen yield of 56.5% and 52.5% for the NCZ-imp while 67.6% and 64.8% for the NCZ-hyd catalyst were achieved, respectively. The kinetic study of steam reforming of PET-phenol was also implemented. The activation energy was found to be 69.03 J/mol for NCZ-imp while 107.3 J/mol for the NCZ-hyd nanostructured catalysts. The PET-phenol steam reforming produced valuable liquid products such as benzene, 2-methyl phenol, and dibenzofuran which is one of the crucial keys to solving the waste plastic recycling problem