Search Results (7)

The efficient conversion of methane into hydrogen-rich syngas is essential for sustainable energy; however, integrating methane partial oxidation (POM) with the water–gas shift (WGS) reaction remains a significant challenge due to thermal and kinetic mismatches. This research presents a spatially decoupled dual-bed reactor configuration, utilizing Ni/GDC and Cu/GDC catalysts, to achieve synergistic hydrogen production. Unlike conventional physically mixed systems, which suffer from thermal hotspots and the unintended promotion of the endothermic Reverse Water–Gas Shift (RWGS) reaction, the dual-bed architecture effectively segregates the reaction zones. Advanced characterization, including O₂-TPO and Raman spectroscopy, reveals that the GDC support acts as a critical oxygen buffer via the Mars-van Krevelen mechanism, modulating the dynamic redox state of the active metal sites to prevent deep oxidation and carbonaceous deactivation. Furthermore, macroscopic performance and carbon–oxygen mass balance analyses confirm that this rational architectural design facilitates a seamless integration of POM and WGS pathways, resulting in significantly maximized H₂ yield. From a broader engineering perspective, this dual-bed strategy offers a practical, low-complexity alternative to intensive integrated technologies such as sorption-enhanced reforming (SER) or chemical looping, providing a robust and scalable framework for durable, high-efficiency hydrogen production. Full article

The increasing energy demand and global dependence on conventional fuels have resulted in severe greenhouse gas (GHG) emissions, necessitating the development of sustainable bioenergy alternatives. Algal is recognized as a promising feedstock for the production of fourth-generation biofuels. This study optimizes catalytic pyrolysis of Arthrospira platensis for bio-oil production via a dual-bed catalyst system of iron-impregnated dolomite (Fe/DM) and a copper-impregnated spent fluid catalytic cracking catalyst (Cu/sFCC). A face-central composite design (FCCD) and response surface methodology (RSM) were used for the delineation of optimal conditions, ensuring that all experimental tests remained within feasible operating conditions of 500–600 °C, a reaction time of 45–75 min, a N₂ flow rate of 50–200 mL/min, and a catalyst loading of 5–20 wt%. The bio-oil yield was maximized at 39.73 ± 2.86 wt% at 500 °C for 45 min, a N₂ flow of 50 mL/min, and 5 wt% catalyst loading to feedstock with a 0.4:0.6 mass ratio of Fe/DM: Cu/sFCC. The dual-catalysts combined Brønsted and Lewis acid sites enhanced the catalytic activity, which promotes the cleavage of carbon–carbon and carbon–hydrogen bonds, including the mechanism of catalytic pathways such as dehydration, decarboxylation, oligomerization, aromatization, and further cracking reactions, and was successful in converting high-molecular-weight molecules into lighter hydrocarbons and significantly improving product selectivity, demonstrating a highly effective pathway for producing high-quality sustainable biofuel. Full article

A single-bed and dual-bed catalyst system was studied to maximize H₂ production from the combination of partial oxidation of CH₄ and water gas shift reaction. In addition, the different types of catalysts, including Ni, Cu, Ni-Re, and Cu-Re supported on gadolinium-doped ceria (GDC) were investigated under different operating conditions of temperature (400–650 °C). Over Ni-based catalysts, methane can easily dissociate on a Ni surface to give hydrogen and carbon species. Then, carbon species react with lattice oxygen of ceria-based material to form CO. The addition of Re to Ni/GDC enhances CH₄ dissociation on the Ni surface and increases oxygen storage capacity in the catalyst, thus promoting carbon elimination. In addition, the results showed that a dual-bed catalyst system exhibited catalytic activity better than a single-bed catalyst system. The dual-bed catalyst system, by the combination of 1%Re4%Ni/GDC as a partial oxidation catalyst and 1%Re4%Cu/GDC as a water gas shift catalyst, provided the highest CH₄ conversion and H₂ yield. An addition of Re onto Ni/GDC and Cu/GDC caused an increase in catalytic performance because Re addition could improve the catalyst reducibility and increase metal surface area, as more of their surface active sites are exposed to reactants. Full article

Recycling plastics on an industrial scale is a key approach to the circular economy. This study presents a techno-economic analysis aimed at recycling polypropylene waste, one of the main consumer plastics. Specifically, it evaluates the technical and economic feasibility of achieving a large-scale cracking process that converts polypropylene waste into an alternative fuel. Pyrolysis is considered as a promising technique to convert plastic waste into liquid oil and other value-added products, with a dual benefit of recovering resources and providing a zero-waste solution. This study concerns a fast catalytic pyrolysis in a fluidized bed reactor, with the presence of a fluid catalytic cracking catalyst of low acidity for high heat transmission, for an industrial plant with a capacity of 1 t/h of polypropylene waste provided by the Greek Petroleum Industry. From the international literature, the operational conditions were chosen pyrolysis temperature at 430 °C, pressure at 1atm, heating rate at 5 °C/min, and yields of products to 71, 14, and 15 wt.%, for liquid fuel, gas, solid product, respectively. The plant design includes a series of apparatuses, with the main one to be the pyrolyzer. The catalytic method is selected over the non-catalytic because the presence of catalyst increases the quantity and quality of the liquid product, which is the main product of the plant. The energy loops of recycling pyrolysis gas and char as a low-carbon fuel in the plant were considered. The production cost, annual revenue, for 2023, are anticipated to reach €13.7 million (115 €/t) and €15 million (15 €/t), respectively, with an estimated investment equal to €5.3 million. The Payback Time is estimated to 2.4 years to recover the cost of investment. The endeavor is rather economically sustainable. A critical parameter for large scale systems is securing feedstock with low or negligible price. Full article

Utilizing carbon dioxide as a carbon source for the synthesis of olefins and aromatics has emerged as one of the most practical methods for CO₂ reduction. In this study, an improved selectivity of 85% for targeting products (ethylbenzene and propylbenzene) is achieved with a benzene conversion of 16.8% by coupling the hydrogenation of carbon dioxide to olefins over the bifunctional catalyst “Oxide-Zeolite” (OX-ZEO) and the alkylation of benzene with olefins over ZSM-5. In addition to investigating the influence of SAPO-34 and ZSM-5 zeolite acidity on product distribution, catalyst deactivation due to coke formation is addressed by modifying both molecular sieves to be hierarchical to extend the catalyst lifespan. Even after 100 h of operation at 400 °C, the catalysts maintained over 80% selectivity towards the target products, with benzene conversion over 14.2%. Furthermore, the pathway of propylbenzene formation is demonstrated through simple experimental design, revealing that the surface Brønsted acid sites of SAPO-34 serve as its primary formation sites. This provides a novel perspective for further investigation of the reaction network. Full article

Rice straw is an agricultural byproduct primarily produced in Asian regions. It is crucial to discover an effective method for converting this waste into chemicals that can be utilized to substitute goods derived from fossil fuels. Pyrolysis serves as an interesting procedure to obtain bio-oil from this rice straw. The composition of the bio-oil obtained after the pyrolysis procedure contains a small quantity of value-added chemicals in addition to various gas components in the gas product. Therefore, the development of catalytic systems that improve this pyrolytic reaction is mandatory. Herein, the design of a dual catalyst bed (CEM/ZSM-5) that catalyzes the volatiles that it releases has been developed. The highest output of 42.1 wt.% of bio-oil, 29.9 wt.% of gases and 28.0 wt.% of bio-char was obtained. Nevertheless, the inclusion of single zeolites to biomass yields biofuel outputs of 42.8 wt.%, gas yields of 27.7 wt.%, and a bio-char yielding of 29.5 wt.%. Additionally, the addition of cement to biomass results in a bio-oil yield of 40.4 wt.% and 30.5 wt.% of gas, along with 29.1 wt.% of char. Regarding pyrolysis gas products, the H2 yield in the produced biogas was increased from 35.9 mL/g to 45.7 mL/g, and the CH4 output was increased from 21.1 mL/g to 27.4 mL/g. The bioenergy output was evaluated employing GC-FID and GC-MS (gas and biofuel). The dual catalytic bed had a significant impact on the contents of the generated biofuel, increasing the quantity of hydrocarbons and other value-added compounds. Full article

Bifunctional Al₂O₃/Cu/ZnO catalysts with Al composition of between 30 mol% and 80 mol% were prepared by sequential precipitation (SP) for the conversion of CO₂ into dimethyl ether (DME). In the SP synthesis, the concentration of a precipitation agent managed to be high enough to induce the complete precipitation of Al³⁺. The prepared precipitates were composed of zincian malachite and amorphous AlO(OH). Furthermore, the calcined mixed metal oxide materials of 60% and 80% Al exhibited a higher acidity than commercial Al₂O₃ and the H₂-reduced catalysts showed the similar Cu dispersion of 6%–7% at all Cu loadings. In the activity test at 573 K and 50 bar, the SP-derived catalyst of 80% Al (SP-80) displayed the best performance corresponding to CO₂ conversion of 25% and DME selectivity of 75% that are close to equilibrium values. In order to overcome the thermodynamic limitation, a dual-bed catalyst system was made up of SP-80 in the first layer and zeolite ferrierite in the next. This approach enabled DME selectivity to be enhanced to 90% while CO₂ conversion increased a little. Consequently, the studied catalyst system based on the SP-derived catalysts can contribute greatly to selective DME production from CO₂. Full article