Volume 38, Issue 5

We review scientific works carried out on the influence of surface hydrophobicity on activity and product selectivity of supported cobalt and iron catalysts during Fischer-Tropsch synthesis (FTS). The characteristics of the surface of catalyst support may influence metal-support interactions, which leads to various degrees of metal dispersion and reducibility. Also, these support surface properties may influence the mass transfer of reactants and products at the catalyst active sites and subsequently affects the performance of the catalyst during FTS. Pre-silylated and post-silylated catalysts have been used to study the influence of surface hydrophobicity on the performance of FTS catalysts. The enhancement of FTS activity by hydrophobicity was mainly ascribed to the improved reducibility of metal oxide species. Furthermore, post-silylated supported iron catalysts favoured the suppression of water-gas shift (WGS) reaction, thereby hindering CO 2 formation.

Stringent environmental regulations and energy insecurity necessitate the development of an integrated process to produce high-quality fuels from renewable resources and to reduce dependency on fossil fuels, in this case Fischer–Tropsch synthesis (FTS). The FT activity and selectivity are significantly influenced by the pretreatment of the catalyst. This article reviews traditional and developing processes for pretreatment of cobalt catalysts with reference to their application in FTS. The activation atmosphere, drying, calcination, reduction conditions and type of support are critical factors that govern the reducibility, dispersion and crystallite size of the active phase. Compared to traditional high temperature H 2 activation, both hydrogenation–carbidisation–hydrogenation and reduction–oxidation–reduction pretreatment cycles result in improved metal dispersion and exhibit much higher FTS activity. Cobalt carbide (Co 2 C) formed by CO treatment has the potential to provide a simpler and more effective way of producing lower olefins, and higher alcohols directly from syngas. Syngas activation or direct synthesis of the metallic cobalt catalyst has the potential to remove the expensive H 2 pretreatment procedure, and consequently simplify the pretreatment process, which would make it more economical and thus more attractive to industry.

Slurry polymerization processes using Zeigler–Natta catalysts, are most widely used for the production of polyethylene due to their several advantages over other processes. Significant advancements have been made in the modeling of these processes to obtain high-quality final products. The modeling work in this field has a very wide scope due to the great diversity of the catalyst types, polymerization processes, polymerization conditions, product qualities and microstructures that exist at the commercial scale. In this article, we have reviewed and discussed the slurry polymerization processes for the production of polyethylene and the multiscale modeling and simulation framework in slurry reactors. The multiscale modeling framework mainly comprises of the kinetic model, single-particle diffusion models, multiphase hydrodynamics, phase equilibria, reactor residence time distribution and the overall mass and heat balances. Guidelines to implement the multiscale mathematical modeling and simulation in slurry-phase olefin polymerization processes are proposed. Special focus is given on the need to reduce the computational effort for the simulation of industrial reactors so that the models can be used as an effective tool-kit for optimization studies using state-of-art algorithms.

Magnetic hyperthermia therapy (MHT) is a highly promising therapeutic modality for the treatment of different kinds of cancers and malignant tumors. The therapy is based on the concept that; iron oxide nanoparticles deposited at cancer sites can generate heat when exposed to an alternating current magnetic field or near infrared radiation and consequently destroying only the cancer cells by exploiting their vulnerability to heat. The fact that the treatment is at molecular level and that iron oxide nanoparticles provide more guided focus heating justifies its efficacy over treatment such as surgery, radiation therapy and chemotherapy. Nevertheless, the spread of MHT as the next-generation therapeutics has been shadowed by insufficient heating especially at the in vivo stage. This can be averted by modifying the iron oxide nanoparticle structure. To this end, various attempts have been made by developing a magnetic hybrid nanostructure capable of generating efficient heat. However, the synthesis method for each component (of the magnetic hybrid nanostructure) and the grafting process is now an issue. This has a direct effect on the performance of the magnetic hybrid nanostructure in MHT and other applications. The main objective of this review is to detail out the different materials, methods and characterization techniques that have been used so far in developing magnetic hybrid nanostructure. In view of this, we conducted a comprehensive review and present a road map for developing a magnetic hybrid nanostructure that is capable of generating optimum heat during MHT. We further summarize the various characterization techniques and necessary parameters to study in validating the efficiency of the magnetic hybrid nanostructure. Hopefully, this contribution will serve as a guide to researchers that are willing to evaluate the properties of their magnetic hybrid nanostructure.

The fertilizer manufacturing faces an ongoing challenge to develop its products to raise the effectiveness of their application, mainly of nitrogenous fertilizers, as well as to reduce any probable adverse ecological effect. In general, chemical fertilizers are very necessary for agricultural lands to provide the essential nutrients for plant growth, which are lost and leached into the surrounding environment during irrigation, which then leads to unwanted side effects, such as crop failure or increased losses to the environment. To solve this problem of nutrients being wasted, the most effective way is to use slow or controlled-release fertilizers (S/CRFs). The current review provides an insight vision into the methods used to save agricultural fertilizers from being wasted due to irrigation. The functional materials or physical techniques are used to maintain a steady release of nutrients. Fertilizers are encapsulated with various compounds based on synthetic or natural polymers to be used as SRFs. In this review paper, a comprehensive survey is presented on SRFs as an effective method in dealing with the problem of fertilizer wastage during irrigation. This review discusses the technology and applications of the latest research findings in this field.