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The mesoporous silica zirconia (m- SiO2/ZrO2) was successfully synthesized in this study using a microwave method, and the effect of the calcination process was studied. In this study, half of the sample was left untreated (labeled "untreated sample"), while the other half was calcined at 850 °C for 3 hours in an air atmosphere in a muffle furnace to remove the surfactant. X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible differential reflectance spectroscopy, nitrogen adsorption-desorption spectroscopy, and electron spin resonance spectroscopy were utilized in order to analyze the catalysts that were produced. The findings from the characterization showed that the calcination procedure caused the creation of oxygen vacancies and increased the surface area, both of which affected the photocatalytic activity. The photocatalytic activity of the calcined m-SiO2/ZrO2 (80%) catalyst was superior to that of the untreated m-SiO2/ZrO2 (19%) catalyst. Zirconia's greater surface area and its natural occurrence in the tetragonal phase are both to blame for this phenomenon. In addition, there is the possibility that a greater proportion of oxygen vacancy will result in a smaller band gap and a lower electron-hole recombination rate. After five cycles, the photocatalytic activity exhibited by both catalysts remained unchanged.

Optimization of hierarchical ZSM-5 structure by variation of the first hydrothermal step at different times provides insight into the evolution of micro/mesopores and its effect as a catalyst for deoxygenation reaction.

This research looks at the potential of utilizing microplastics waste (MPW) found in oceans and soil as a source of liquid fuel. A significant portion of this pollutant is presently untreated and ends up in landfills, exacerbating the worldwide issue of marine and land pollution. Pyrolysis is a tertiary recycling process that is presented as a solution in the presence of a catalyst. This study aimed to develop bifunctional Ni-Pt nanocatalysts supported on TiO2 and Al2O3 for hydrogen and valued fuels generation from pyrolysis-catalytic steam reforming conditions of microplastics waste dissolved in phenol. The chemical and physical properties of nanocatalysts were characterized by BET, XRD, TEM, FESEM, FTIR, H2-TPR, CO2-TPD, NH3-TPD, TGA, ICP and CHNS. It was found that the introduction of a small portion of Pt (2 wt%) metal to the Ni/Ti-Al nanocatalyst was found to significantly enhance the reducibility, acidity, basicity nanocatalyst performance and stability. C–O(H), C C–C, and C–O were the major functional clusters of the liquid yields surveyed from the FTIR spectrums during pyrolysis. A valuable liquid product such as trimethyl-(2-trimethylsilylphenyl)silane, cyclohexane-1,3-dione, 2-allylaminomethylene-5,5-dimethyl-, bis(2-ethylhexyl)phthalate (BEHP), etc. compounds were produced from the pyrolysis-catalytic steam reforming reaction. This sight is a crucial indication of utilizing microplastics pollution for value-added fuel production and decreasing the risk threats of marine life.

CO methanation has arisen as an attractive research area due to its ability to transform syngas into substituted natural gas. Current monometallic catalysts have a severe problem; quickly deactivated. It is generally known that by introducing another metal to create a bimetallic catalyst, synergistic interaction between both metals considerably enhances catalyst effectiveness. This paper provides a detailed overview of bimetallic catalysts for CO methanation, covering its synthesis method and effect on physicochemical characteristics. The bimetallic catalyst can both reinforce or weaken the metal-support and metal-metal interaction, which weakening it favors reducibility while reinforcing it favors stability. Particle size and dispersion also improve, whereas adding lanthanides can increases the basicity. We also present the mechanism of CO methanation over the bimetallic catalyst, which modifies the mechanism's energy and rate value. This review provides insights on how reaction effectiveness is enhanced, enabling catalyst development with the highest possible performance.

Conversion of lignocellulosic biowastes from agricultural industry into nanocrystalline cellulose provides pathway to reduce environmental pollution while enhancing the economic value of biowastes. Nanocellulose (NCC) with uniform morphology was isolated from pepper (Piper nigrum L.) stalk waste (PW) using acid hydrolysis method. The role of inorganic acids (sulfuric acid, hydrochloric acid, phosphoric acid), organic acids (oxalic acid, citric acid, acetic acid) and variation of sonication times were investigated on the physicochemical characteristics, self-assembled structure, crystallinity, particle size, zeta potential and thermal stability of the isolated nanocellulose. Hydrolysis using inorganic acids transformed cellulose from PW into a spherical shaped NCC at ~33-67 nm of average diameter. Meanwhile hydrolysis in organic acids produced rod-shaped NCC at 210-321 nm in length. This study highlighted the role of acidity strength for organic acid and inorganic acid in controlling the level of hydrogen bond dissociation and the dissolution of amorphous fragments, which consequently directing the morphology and the physicochemical properties of NCCs.

Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually. One solution is biodiesel production

Bisphenol A (BPA) is an endocrine disruptor, and removing it from contaminated water is a major environmental concern. Herein, graphene derivatives such as graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) supported silica-zirconia (SZ) were successfully synthesized for photodegradation of BPA. The photodegradation of BPA was ordered as follows: rGO/SZ (88%)>GO/SZ (63%)>G/SZ (58%)>SZ (55%). This is because rGO has bigger regions for π-π stacking and less negatively charged carboxyl groups, which BPA has a higher adsorption affinity than GO. In addition, the highest degradation is predominantly due to the high number of carbon-support interactions and defects sites, including oxygen vacancy. This encouraged effective mobility of charge carriers and subsequently enhanced photoactivity. In this study, the rGO/SZ catalyst was chosen to optimize further the reaction parameters including catalyst dosage, pH and initial concentration of BPA. According to the analysis of variance, the catalyst dosage was the most important variable in the degradation of BPA, followed by pH and initial concentration. The optimum BPA degradation predicted from response surface methodology is 88% at conditions of 8.09 mg L−1 using 0.469 g L−1 of rGO/SZ at pH 6.1, which is reasonably close to the predicted value (89.8%). The rGO/SZ catalyst was found to be stable even after five cycles in the reusability testing.

It has been well established that carbon dioxide (CO2) is one of the main greenhouse gasses and a leading driver of climate change. The chemical conversion of CO2 to substitute natural gas (SNG) in the presence of renewable hydrogen is one of the most promising solutions by a well-known process called CO2 methanation. There have been comprehensive efforts in developing effective and efficient CO2 methanation catalytic systems. However, the choice of competitive and stable catalysts is still a monumental obstruction and a great challenge towards the commercialization and industrialization of CO2 methanation. It is necessary to emphasize the critical understandings of intrinsic and extrinsic interactions of catalyst components (active metal, support, promoter, etc.) for enhanced catalytic performance and stability during CO2 methanation. This study reviews the up-to-date developments on CO2 methanation catalysts and the optimal synergistic relationship between active metals, support, and promoters during the catalytic activity. The existing catalysts and their novel properties for enhanced CO2 methanation were elucidated using the state-of-the-art experimental and theoretical techniques. The selection of an appropriate synthesis method, catalytic activity for CO2 methanation, deactivation of the catalysts, and reaction mechanisms studies, have been explicitly compared and explained. Therefore, future efforts should be directed towards the sustainable developments of catalytic configurations for successful industrial applications of CO2 utilization to SNG using CO2 methanation.

Santa Barbara Amorphous-15 (SBA-15) is a promising molecular sieve material with its highly uniform porosity; nonetheless, its tubular pore channels discouraged mass transfer of reactants during catalysis. Herein, SBA-15 was altered by microemulsion technique to prepare two fibrous SBA-15 with distinct morphologies, viz. rod-liked F-SBA-15 and dendritic DFSBA-15. After Ni impregnation, the Ni/fibrous SBA-15 catalysts (Ni/F-SBA-15 and Ni/DFSBA-15) were catalytically evaluated with methane dry reforming (MDR). From characterization, rod-shaped F-SBA-15 had outer fibrous layer whereas dendritic DFSBA-15 consisted of a solid core with radially projected fibres. Besides, Ni/F-SBA-15 possessed uneven sized NiO but Ni/DFSBA-15 had uniform NiO dispersion. Characterization also proved that fibrillation and Ni impregnation did not alter the pristine properties of SBA-15. However, the surface attributes of SBA-15 remarkably reduced after fibrillation and Ni impregnation. The strength of metal-support (Ni-SiO2) interaction could be ranked as: Ni/DFSBA-15 > Ni/F-SBA-15 > Ni/SBA-15 (previously reported). Both Ni/fibrous SBA-15 catalysts exhibited high proportion of moderate basicity, which favoured the carbon removal via reverse Boudouard reaction. In accordance with endothermicity, the optimal temperature of MDR over both catalysts was 800 °C as greater temperature provoked conspicuous CH4 thermal decomposition. For 50 h MDR at 800 °C, both catalysts presented superior catalytic activity and stability. With a fully accessible siliceous framework, Ni/DFSBA-15 attained greater reactant conversions (84.05–87.40% X C H 4 and 81.80–85.60% X C O 2 ) than Ni/F-SBA-15 (80.30–85.80% X C H 4 and 76.73–84.10% X C O 2 ). In overall, Ni/DFSBA-15 was more coke-resistant than Ni/F-SBA-15 by virtue of its fully accessible structure, uniformly dispersed Ni phase, and stronger metal-support interaction.

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.

The contamination by hexavalent chromium and organic pollutants is a serious health issue. Moreover, hexavalent chromium can react with organic pollutants to form a complex which is difficult to treat, and thus remains in the natural environment for long times. Simultaneous photocatalysis can remove both organic pollutants and hexavalent chromium. Here we review the use of period 4 metal oxide-based photocatalysts for the removal of organic pollutants and hexavalent chromium. Titanium dioxide exhibited the highest performance, up to 100%, in removing both hexavalent chromium and organic pollutants from water.

The fibrous silica HZSM-5 (HFZ) was synthesized by microemulsion method assisted with ZSM-5 seed crystallization under different amounts of a silica source, tetraethyl orthosilicate (TEOS, 1.0–1.5 mol) for superior benzene methylation activity. The aptness of the physicochemical properties of HFZ offered an abundance of active sites, allow benzene conversion up to 90% and toluene production at the lower temperature of 300 °C, with the following order of yields: 1.0HFZ (66.1%) > 1.5HFZ (46.2%) > commercial HZSM-5 (41.9%). Additionally, the less extraframework alumina-possessing 1.0HFZ was found to display the lowest activation energy and substrate diffusion limitation, compared to microstructured commercial HZSM-5 (HZ). The 1.0HFZ also possessed a lower Lewis acidic nature and able to decrease subsequent production of ethylbenzene (EB) while significantly improved further methylation to xylene. The in-situ FTIR study gave insights on the adsorption of both methanol and benzene on the active sites of catalyst, revealing that 1.0HFZ followed the associative mechanism in which both methanol and benzene were adsorbed onto the active sites. Meanwhile, HZ followed the consecutive mechanism due to the presence of intermediate methoxy.

The performance of cobalt supported on mesoporous alumina (MA) under the influence of reaction temperature (923 K–1073 K) and reactant partial pressure (10 kPa–40 kPa) for CO2–CH4 reforming was executed by using a tubular fixed-bed reactor. 10%Co/MA exhibited great catalytic performance ( X C H 4 = 70.9 % , X C O 2 = 71.7 % and D a = 1.3 % ), credited to the well dispersion of Co within pore MA, strong metal-support interaction, and MA confinement ability. Based on Langmuir-Hinshelwood kinetic analysis, the dissociative adsorption of both reactants on a single Co active site was selected for this study. The lower value of activation energy (28.9 kJ mol−1) suggested that Co particles were finely scattered on the MA surface. Regardless of carbon types, the amount of coke accumulated on the spent 10%Co/MA within 8 h of CO2–CH4 reforming was inhibited due to fine Co distribution inside MA structure, as well as lessened with the raise of reforming temperature from 923 to 1073 K due to improvement in reverse Boudouard reaction.

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N2 adsorption-desorption, NH3 and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.

The mesoporous gamma-alumina (γ-Al2O3) synthesized via evaporation-induced self-assembly method (EISA) using inorganic salt, Al(NO3)3·9H2O precursor and water-ethanol solvent mixture was implemented as a support for Co catalyst in methane dry reforming at 973–1073 K under 1 atm. The γ-Al2O3 support possessed filament-shaped morphology with surface area of 173.4 m2 g−1 and cobalt nanoparticles were successfully dispersed on support with small crystallite size of 7.8 nm. The stability of 10%Co/Al2O3 was evident for CH4 and CO2 conversions at 1023 and 1073 K. CH4 conversion could reach to 76.2% while 81.6% was observed for CO2 conversion at 1073 K. Although graphitic and amorphous carbons were unavoidably formed on used catalyst, 10%Co/Al2O3 exhibited an outstanding performance comparable to noble metals with the desired ratio of H2/CO for downstream Fischer-Tropsch process.

In this study, unique fibrous silica ZSM-5 was successfully synthesized by using three type of alcohol possessing different alkyl-chain length as the co-surfactant. The effect of diverse co-surfactant was observed in the changes of physical properties, such as crystallinity, inter-dendrimer distances and pore properties. According to the IR and temperature programmed desorption of ammonia (NH3-TPD) analyses, all catalysts exhibited different acid strengths which could be triggered by the different amount of additional silica species. All catalysts exhibited high catalytic performance in the hydrocracking of 1,3,5-triisopropylbenzene due to the absence of diffusion limitation. However, FZSM5C3 exhibited the highest catalytic activity which corresponded to its high number of Bronsted acid sites. It was observed that different length of co-surfactant alkyl-chain has resulted in different degree of oil penetration into the microemulsion system which subsequently triggered in various inter-dendrimer distances and amount of incorporated silica species. Hence, the altered physicochemical properties led to the difference in catalytic performance due to the presence of different number of Bronsted acid sites.

The first investigation of La-promoted Co/Al2O3 catalysts in Ethylene Glycol-CO2 conversion (EGCC) for syngas (H2 + CO) production was conducted in this work. Co/Al2O3 catalysts modified with different La promoter loadings (1, 3, and 5%) were generated through sequential incipient wetness impregnation technique and employed for EGCC. The physicochemical attributes of the generated catalysts were examined via Brunauer-Emmett-Teller (BET), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Raman, and temperature-programmed oxidation (TPO). 3%La-promoted catalyst owned the largest specific surface area, smallest Co crystallite size of 9.8 nm, and lowest reduction temperature among the promoted catalysts. These excellent properties resulted in the highest catalytic performance on the 3%La-promoted catalyst (i.e., C2H6O2 conversion = 77.6 %, CO2 conversion = 43.1 %, H2 yield = 75.3 %, and CO yield = 76.8 %). The significant reduction in carbon deposition of the 3%La-promoted catalyst was due to the La capability in eliminating deposited carbon via the formation of intermediate lanthanum dioxycarbonate, La2O2CO3.

The impact of La2O3 promoter loading on alumina-supported cobalt catalysts was investigated in terms of physicochemical properties and catalytic performance for CO2 reforming of methane (CRM) at stoichiometric CH4/CO2 ratio and 1023 K. Both Co3O4 (with crystal size: 5.2–8.4 nm) and La2O3 nanoparticles were finely dispersed on support surface. The promotional La2O3 effect could noticeably increase CH4 and CO2 conversions to 29.3% and 17.3%, correspondingly due to improved basic site concentration and decreasing crystallite size of active metal in association with promoter addition. 5%La loading was an optimal promoter content for reactant conversions as well as yield of H2 and CO. 5%La-10%Co/Al2O3 also exhibited the highest resistance to carbon deposition owing to the basic nature, redox feature and oxygen vacancy of La2O3 dopant. Notably, the H2/CO ratio obtained within 0.84–0.98 is preferable for Fischer-Tropsch reaction in downstream to yield liquid hydrocarbon fuels.

Red mud as industrial waste from bauxite was utilized as a precursor for the synthesis of mesoporous ZSM-5. A high concentration of iron oxide in red mud was successfully removed using alkali fusion treatment. Mesoporous ZSM-5 was synthesized using cetyltrimethylammonium bromide (CTABr) as a template via dual-hydrothermal method, and the effect of crystallization time was investigated towards the formation of mesopores. Characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicated the formation of cubic crystallite ZSM-5 with high surface area and mesopore volume within 6 h of crystallization. Increasing the crystallization time revealed the evolution of highly crystalline ZSM-5; however, the surface area and mesoporosity were significantly reduced. The effect of mesoporosity was investigated on the adsorption of methylene blue (MB). Kinetic and thermodynamic analysis of MB adsorption on mesoporous ZSM-5 was carried out at a variation of adsorption parameters such as the concentration of MB solution, the temperatures of solution, and the amount of adsorbent. Finally, methanol, 1-butanol, acetone, hydrochloric acid (HCl), and acetonitrile were used as desorbing agents to investigate the reusability and stability of mesoporous ZSM-5 as an adsorbent for MB removal.

An eco-benign procedure was developed to synthesize ultrafine and discrete spherical shape silver nanoparticles (5–20 nm) in the presence of ionic liquid. Different types of leaves extract, including Cymbopogon nardus, Polygonum minus, Allium Cepa, and Petroselinum crispum, were used as a green reducing and capping agents for the synthesis process. The Ag nanoparticles were denoted as AgCN, AgPM, AgAC, and AgPC, respectively. Notably, it was demonstrated that the Ag nanoparticles' size could simply be altered by varying the amount of total phenolic content (TPC) using different leaves. It was indicated from the characterization results that the AgPC nanoparticles’ size was nine-fold smaller compared to the conventional Ag nanoparticles due to the high amount of total phenolic compounds (TPC) in the Petroselinum crispum. The results also revealed that ionic liquid and phenolic compounds had a synergistic effect on reducing silver ions (Ag+) into silver nanoparticles (Ag) and the stabilization of the nanoparticles. The order obtained for the degradation of methylene blue (MB) was AgPC > AgPM > AgCN > AgAC > Ag was influenced by a large amount of TPC and led to a decrease in particle size and enhanced photocatalytic activity. The AgPC remained effective and stable even after five subsequent cycles.

Limestone was converted to high surface area CaO/MgO catalysts via calcination-hydration-dehydration (CHD) method for transesterification of coconut oil to biodiesel. Thermal decomposition at 900°C transformed dolomite CaMg(CO3)2 to large crystallite and low surface area CaO/MgO. CHD treatment eliminated the large CaO/MgO aggregates and increased the surface area and the activity of CaO/MgO. The addition of polyethylene glycol (PEG) as surfactant during CHD reduced the CaO/MgO crystallite size to ~377 nm and enhanced the surface area (39 m2/g), the pore volume (0.0322 m3/g), and the basicity of the catalysts (7.8 mmol/g). Transesterification of coconut oil showed an increase in oil conversion from 16.45 to 49.27% when CaO/MgO was produced using PEG. Optimization studies at the variation of reaction temperatures, the ratio methanol:oil, and the amount of catalysts produced the optimum biodiesel yield of 81.76%. Impregnation with 5% NiO introduced acid-base functionality for esterification FFA to FAME, further improved biodiesel yield to 90%, and reduced the FFA yield. The kinematic, density, flash point, acid numbe,r and carbon residue of biodiesel from coconut oil were determined at 1.93 mm2/s, 0.86g/cm3, 137°C, 0.27 mg KOH/g, and 0.22% respectively, and were within the ASTM D6751 standard.

Rising concerns about petroleum depletion and energy demand are calling for alternative processes such as methane partial oxidation to produce syngas for downstream synthetic fuel production. However, industrial application is limited by catalyst deactivation caused by carbon deposition and reoxidation of active metals. Here we synthesized dendritic fibrous Pd, Ru and Rh/KAUST Catalysis Centre 1 (KCC-1) catalysts by microemulsion followed by wetness impregnation. Catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, electronic spin resonance, Fourier transform infrared spectroscopy and UV–Vis diffuse reflectance spectroscopy. We measured catalytic performance, stability and regenerability at 900 °C over 16 h-on-stream. Results reveal that oxygen vacancies into the KCC-1 framework enhance the interaction with noble metal particles, creating a strong metal–support interaction decreasing in the order Rh/KCC-1, Pd/KCC-1, Ru/KCC-1. Interestingly, CH4 conversion followed the same order: 74−80% for Rh/KCC-1, 60−71% for Pd/KCC-1, 53−63% for Ru/KCC-1, without a significant carbon deposit. These findings mean that oxygen vacancies retained the metal in the active metallic phase and prevented carbon deposits. Overall, metal/KCC-1 is as bifunctional catalyst whereby oxygen vacancies generate labile electrons contributing to electrostatic metal–support interactions, stabilization of metal phases and providing labile oxygen ions for carbon gasification.

The visible-light response is a necessary condition for titanium dioxide (TiO2) photocatalyst to function as a visible light active photocatalyst. This condition can be solved by investigation of the bandgaps and the optimization of doping levels of multivalency metal-doped TiO2. In this study, pure and Cu, Fe, and Ni-doped TiO2 photocatalysts were prepared by the sol‐gel method. The photocatalysts were characterized using XRD, FTIR, FESEM, EDX, N2 physisorption, and UV‐Vis spectrophotometry techniques. The XRD patterns of all pure TiO2 and Cu/TiO2, Fe/TiO2, and Ni/TiO2samples showed the dominant structure of the anatase TiO2 phase. The presence of functional groups at the interface of TiO2 particles was showed by FTIR. The FESEM analysis showed that the particle size of the prepared samples was uniform with spherical morphology. EDX results showed that TiO2 has successfully incorporated Cu, Fe, and Ni metals onto its surface. The BET analysis showed that the specific surface area of the doped samples increased with the amount of doping. The optical properties of all samples were carried out using UV-DRS measurements and their obtained bandgap energies were in the range of 3.22 - 3.42 eV. The pure TiO2 displayed more than 98% and 97% decolorization rates for MB solution at the end of irradiation time of 5 h under UV and visible light, respectively. Among the doped samples, 3 mol% Ni/TiO2 and Cu/TiO2 demonstrated the highest photocatalytic activity (97.65%) under UV light and 6 mol% Ni/TiO2 under visible light for MB (96.86%) decolorization.