In this study, an innovative methodology for the preparation of high-performance polyolefin-based materials combining a unique dendrimeric silica (DS) catalyst carrier, a straightforward in-situ supporting procedure and in-situ ethylene polymerization...
Several aluminum containing dendrimeric silica nanospheres, DSAl materials, were prepared using different synthesis and post-synthetic procedures. These materials were used for the immobilization of Cp2ZrCl2 via direct impregnation. The support materials were rigorously characterized by TEM, N2 adsorption, FTIR (using pyridine as probe molecule) and SS-NMR in order to assess their morphological, textural and surface acidic properties. Supported catalysts were tested in ethylene homopolymerization using methylaluminoxane (MAO) as co-catalyst and scavenger. The relationships between the types and strength of acid sites, as well as the textural and morphological parameters of DSAl materials with the behavior of catalytic systems is explored in this work. The results analyzed in this paper confirm the importance that support surface acidity plays in the formation of the active species for ethylene polymerization and in its activity without neglecting the contribution of support textural properties as well.[a]Dr.
The production of Refused Derived Fuel (RDF) from Municipal Solid Waste is one of the routes to attain a circular economy as it promotes the circular loop of materials and energy. Furthermore, in addition to the waste‐to‐energy approach, RDF production reduces the amount of waste disposed in landfills, thus reducing greenhouse gasses emissions and water streams' contamination. Nevertheless, there are still numerous technological constraints to RDF use, namely, its moisture content and granulometry that are highly dependent on the production process. In this context, this work discusses the contribution of RDF to the promotion of the circular economy, presenting the main RDF properties and production processes. An analysis of the RDF market in Europe, Asia, North America, and Africa was performed by analyzing imports and exports. The analysis highlights the expansion of RDF as an energy source in current times with Europe as a driving force for its integration following circular economy guidelines. However, incentives would significantly speed up RDF adoption and decrease the carbon footprint as a short‐term mitigation strategy.
The current energy and climate crisis calls for immediate action in replacing fossil fuels with those derived from renewable sources. The Energreen process performs the direct liquefaction of biomass to produce a liquid biofuel for the cement industry and an aqueous solution of added-value compounds for further processing. The present work details the development of an Aspen Plus® model to simulate this biomass liquefaction process. The proposed model describes the Energreen liquefaction process using simplified reaction kinetics and thermodynamic models. The model was validated using data from a real liquefaction pilot plant with a deviation of 6.4%. The simulation, conducted with several biomass samples of variable compositions, showed that the process is robust enough to deal with different compositions and, due to the substitution of the fossil fuels presently used in the cement plant, it will allow savings of up to USD 102,000 per year to be achieved. Several analyses of the sensitivity of the results to the process variables were performed and it was possible to identify the reactor temperature and the reaction activation energy as the most impactful parameters on the process output. Overall, the results allow us to conclude that the proposed model is a solid framework for the optimization of industrial liquefaction processes.
The current manuscript presents a review on existing kiln burner technologies for the cement production process, in the context of the current climate of energy transition and environmental remediation. Environmental legislation has become ever stricter in response to global climate change, and cement plants need to adapt to this new reality in order to remain competitive in the market and ensure their longevity. The cement production process is a well-established technology with more than a century of existence. There are several plants in operation whose process is outdated by modern standards, particularly considering the current industry decarbonization needs. The cement process requires tremendous amounts of energy, mainly recovered from the combustion of solid, liquid or gaseous fuels, which yields massive emissions of greenhouse gases. Thus, an important onus is placed upon the minimization of pollutant emission in the combustion system, as well as a substitution of fossil fuels with more sustainable alternatives. One of the sustainable alternative fuels comes in the form of refuse derived fuels (RDF). These high caloric fractions of municipal solid waste present a double advantage by reducing the amount of fossil fuels used and reducing the landfilling fraction of waste. However, their use in rotary kiln burners comes with important limitations for burner operation, namely that a high degree of control over primary air supply is needed to ensure complete combustion with minimal pollutant emission.
The electrolysis of black liquor (BL) has emerged as a new form to valorize this byproduct from the pulp and paper industry. BL electrolysis produces a green fuel, hydrogen, and lignin, a high added-value compound. In opposition to water electrolysis, a symmetric process with two different gases produced at the electrodes, hydrogen and oxygen, BL electrolysis is seen as an asymmetric process, as hydrogen is the only gas generated (at the cathode), while solid lignin is electrodeposited at the anode. The present work intended to develop a model in Aspen Plus® to simulate BL electrolysis and consequently evaluate the performance of the BL electrolyzer. Aspen Plus® does not include a package for electrolyzers, so it was necessary to use the Aspen Custom Modeler (ACM) tool. The model developed in ACM is valid for the following conditions: nickel electrodes with 2 cm interelectrode distance, cell voltage between 1.5 V and 2.0 V, and temperatures between 25 and 35 °C for batch operation and 25 and 65 °C for continuous operation. Sensitivity analysis demonstrated that the optimum working temperature for batch operation is 35 °C, whereas it is 45 °C for continuous operation. An economic analysis was carried out, calculating the real gross profit (RGP) for the process and the electricity cost. A 2 kW electrolyzer with 80 cells and an active area of 0.3 m2 was simulated. For the electrolyzer in batch operation, RGP values of 1056 €/year and 1867 €/year for the worst and the best scenario were obtained, respectively, and the electricity cost was 1431 €/year. For continuous operation, the RGP values were 2064 €/year and 3648 €/year for the worst and best scenario, respectively, and 2967 €/year for the electricity costs.
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