Oxidative coupling of methane to light olefins using waste eggshell as catalyst

Fe Nanoparticle Size Control of the Fe-MOF-Derived Catalyst Using a Solvothermal Method: Effect on FTS Activity and Olefin Production

The design of a highly active Fe-supported catalyst with the optimum particle and pore size, dispersion, loading, and stability is essential for obtaining the desired product selectivity. This study employed a solvothermal method to prepare two Fe-MIL-88B metal-organic framework (MOF)-derived catalysts using triethylamine (TEA) or NaOH as deprotonation catalysts. The catalysts were analyzed using X-ray diffraction, N₂-physisorption, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, H₂ temperature-programed reduction, and thermogravimetric analysis and were evaluated for the Fischer-Tropsch synthesis performance. It was evident that the catalyst preparation in the presence of TEA produces a higher MOF yield and smaller crystal size than those produced using NaOH. The pyrolysis of MOFs yielded catalysts with different Fe particle sizes of 6 and 35 nm for the preparation in the presence of TEA and NaOH, respectively. Also, both types of catalysts exhibited a high Fe loading (50%) and good stability after 100 h reaction time. The smaller particle size TEA catalyst showed higher activity and higher olefin yield, with 94% CO conversion and a higher olefin yield of 24% at a lower reaction temperature of 280 °C and 20 bar at H₂/CO = 1. Moreover, the smaller particle size TEA catalyst exhibited higher Fe time yield and CH₄ selectivity but with lower chain growth probability (α) and C₅₊ selectivity.

Glass Lightweight Aggregates from Glass Cullet and Mining and Food Industry Carbonate Waste

Lightweight aggregates are extensively used in construction and other industrial applications due to their technological characteristics. The extraction of natural aggregates results in serious environmental effects. Thus, within the circular economy concept, the valorization of waste through the optimization of materials and product design is encouraged. In this work, glass lightweight aggregates were prepared from mixtures of white glass cullet and carbonate wastes from mining (wastes originating from the extraction, manufacture and marketing of magnesite and its derivatives) and the food industry (eggshell and mussel shell). The effects of different processing parameters, such as the particle size of the base glass, percentage of the blowing additive, shaping method, heating rate, temperature and processing time, were evaluated. The results indicate that the mineralogical composition of the blowing agent and the particle size of the base glass are the two processing parameters with the greatest impact on expansion efficiency. Thus, glass artificial aggregates were obtained with characteristics similar to those of commercial products (density values ranged between 0.3 and 0.8 g/cm3 and mechanical strength between 0.7 and 1.5 MPa) from thermal shock expansion treatments in the temperature range 800–900 °C and with dwell times no longer than 15 min.

A Review on Production of Light Olefins via Fluid Catalytic Cracking

The fluid catalytic cracking (FCC) process is an alternative olefin production technology, with lower CO2 emission and higher energy-saving. This process is used for olefin production by almost 60% of the global feedstocks. Different parameters including the operating conditions, feedstock properties, and type of catalyst can strongly affect the catalytic activity and product distribution. FCC catalysts contain zeolite as an active component, and a matrix, a binder, and a filler to provide the physical strength of the catalyst. Along with the catalyst properties, the FCC unit’s performance also depends on the operating conditions, including the feed composition, hydrocarbon partial pressure, temperature, residence time, and the catalyst-to-oil ratio (CTO). This paper provides a summary of the light olefins production via the FCC process and reviews the influences of the catalyst composition and operating conditions on the yield of light olefins.

State-of-the-Art of Eggshell Waste in Materials Science: Recent Advances in Catalysis, Pharmaceutical Applications, and Mechanochemistry

Eggshell waste is among the most abundant waste materials coming from food processing technologies. Despite the unique properties that both its components (eggshell, ES, and eggshell membrane, ESM) possess, it is very often discarded without further use. This review article aims to summarize the recent reports utilizing eggshell waste for very diverse purposes, stressing the need to use a mechanochemical approach to broaden its applications. The most studied field with regards to the potential use of eggshell waste is catalysis. Upon proper treatment, it can be used for turning waste oils into biodiesel and moreover, the catalytic effect of eggshell-based material in organic synthesis is also very beneficial. In inorganic chemistry, the eggshell membrane is very often used as a templating agent for nanoparticles production. Such composites are suitable for application in photocatalysis. These bionanocomposites are also capable of heavy metal ions reduction and can be also used for the ozonation process. The eggshell and its membrane are applicable in electrochemistry as well. Due to the high protein content and the presence of functional groups on the surface, ESM can be easily converted to a high-performance electrode material. Finally, both ES and ESM are suitable for medical applications, as the former can be used as an inexpensive Ca2+ source for the development of medications, particles for drug delivery, organic matrix/mineral nanocomposites as potential tissue scaffolds, food supplements and the latter for the treatment of joint diseases, in reparative medicine and vascular graft producing. For the majority of the above-mentioned applications, the pretreatment of the eggshell waste is necessary. Among other options, the mechanochemical pretreatment has found an inevitable place. Since the publication of the last review paper devoted to the mechanochemical treatment of eggshell waste, a few new works have appeared, which are reviewed here to underline the sustainable character of the proposed methodology. The mechanochemical treatment of eggshell is capable of producing the nanoscale material which can be further used for bioceramics synthesis, dehalogenation processes, wastewater treatment, preparation of hydrophobic filters, lithium-ion batteries, dental materials, and in the building industry as cement.