Effect of Polyethylene Pyrolysis Oil Hydrotreatment on the Pt/Al2O3 Catalyst: Experimental Characterization.

The dramatic increase in plastics production, coupled with a low recycling and recovery rate, has been a major challenge for sustainable practices and combating climate change. Hydrotreatment processing to upgrade fuel oils is a well-known process in the petroleum industry. In this work, we aim to investigate the catalyst properties before and after the hydrotreatment of pyrolysis oil derived from plastics, namely, linear low-density polyethylene, as no such report is available in the literature. Granular and powder forms of the Pt/Al2O3 catalyst were used in this study with characterization methods executed as such: transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and IR-RIS. XRD data show that the crystallinity of the catalyst support was unaffected by the hydrotreatment without any residues left, as the characteristic diffraction peaks were indicated for the crystalline phase of the support as 37.4, 39.8, 46.3, and 67.3°. In addition, the TGA experiments revealed that the carbon deposition on the spent catalyst was higher, as indicated by the higher weight loss (15.359%) compared to the fresh catalyst sample (11.43%). XPS analysis showed that the carbon deposition is more intense on the granular spent catalyst, as the intensity of the peaks is some 15 times greater than the peaks from the fresh catalyst. Also, compared to the observed peaks of the powder catalyst, less coke is formed. The band at 1624.05 cm-1 from the IR-RIS spectra was attributed to a shifted C=O band from the coke formation. The extension of these investigations using different catalysts to improve their characteristics and performance and to inhibit coke deposition will contribute to the incorporation of such processes in industry as well as the cost of fuels.

Formic Acid Decomposition Using Palladium-Zinc Preformed Colloidal Nanoparticles Supported on Carbon Nanofibre in Batch and Continuous Flow Reactors: Experimental and Computational Fluid Dynamics Modelling Studies.

The need to replace conventional fuels with renewable sources is a great challenge for the science community. H2 is a promising alternative due to its high energy density and availability. H2 generation from formic acid (FA) decomposition occurred in a batch and a packed-bed flow reactor, in mild conditions, using a 2% Pd6Zn4/HHT (high heated treated) catalyst synthesised via the sol-immobilisation method. Experimental and theoretical studies took place, and the results showed that in the batch system, the conversion was enhanced with increasing reaction temperature, while in the continuous flow system, the conversion was found to decrease due to the deactivation of the catalyst resulting from the generation of the poisoning CO. Computational fluid dynamics (CFD) studies were developed to predict the conversion profiles, which demonstrated great validation with the experimental results. The model can accurately predict the decomposition of FA as well as the deactivation that occurs in the continuous flow system. Of significance was the performance of the packed-bed flow reactor, which showed improved FA conversion in comparison to the batch reactor, potentially leading to the utilisation of continuous flow systems for future fuel cell applications for on-site H2 production.

Recent progress on sonochemical production for the synthesis of efficient photocatalysts and the impact of reactor design.

Sonochemical-assisted synthesis has flourished recently for the design of photocatalysts. The main power used is ultrasound that allows the nanomaterials shape and size modification and control. This review highlights the effect in formation mechanism by ultrasound application and the most common photocatalysts that were prepared via sonochemical techniques. Moreover, the challenge for the suitable reactor design for the synthesis of materials or for their photocatalytic evaluation is discussed since the most prominent reactor systems, batch, and continuous flow, has both advantages and drawbacks. This work summarises the significance of sonochemical synthesis for photocatalytic materials as a green technology that needs to be further investigated for the preparation of new materials and the scale up of developed reactor systems to meet industrial needs.

Computational Studies on Microreactors for the Decomposition of Formic Acid for Hydrogen Production Using Heterogeneous Catalysts.

Sustainable alternatives to conventional fuels have emerged recently, focusing on a hydrogen-based economy. The idea of using hydrogen (H2) as an energy carrier is very promising due to its zero-emission properties. The present study investigates the formic acid (FA) decomposition for H2 generation using a commercial 5 wt.% Pd/C catalyst. Three different 2D microreactor configurations (packed bed, single membrane, and double membrane) were studied using computational fluid dynamics (CFD). Parameters such as temperature, porosity, concentration, and flow rate of reactant were investigated. The packed bed configuration resulted in high conversions, but due to catalyst poisoning by carbon monoxide (CO), the catalytic activity decreased with time. For the single and double membrane microreactors, the same trends were observed, but the double membrane microreactor showed superior performance compared with the other configurations. Conversions higher than 80% were achieved, and even though deactivation decreased the conversion after 1 h of reaction, the selective removal of CO from the system with the use of membranes lead to an increase in the conversion afterwards. These results prove that the incorporation of membranes in the system for the separation of CO is improving the efficiency of the microreactor.

Different reactor configurations for enhancement of CO2 methanation.

Greenhouse gas emissions are a massive concern for scientists to minimize the effect of global warming in the environment. In this study, packed bed, coated wall, and membrane reactors were investigated using three novel nickel catalysts for the methanation of CO2. CFD modelling methodologies were implemented to develop 2D models. The validity of the model was investigated in a previous study where experimental and simulated results in a packed bed reactor were in a good agreement. It was observed that the coated wall reactor had poorer performance compared to the packed bed, approximately 30% difference between the results, as the residence time of the former was lower. In addition, two membrane configurations were proposed, including a membrane packed bed and membrane coated wall reactor. Additional studies were performed in the coated wall reactor revealing that lower flow rates lead to higher conversion values. As for the bed thickness the optimum layer was found to be 1 mm. In both membrane reactor configurations, the effect of the thickness of M1 membrane, which indicates the membrane for the removal of H2O, didn't show difference while the reduction of the thickness of M2 membrane, which indicates the membrane for the removal of CO2, H2 and H2O, showed better results in terms of conversion.