Hyper-Cross-Linked Polystyrene as a Stabilizing Medium for Small Metal Clusters

Among different polymers nanostructured cross-linked aromatics have the greatest potential as catalytic supports due to their exceptional thermal and chemical stability and preservation of the active phase morphology. This work studies the ability of hyper-cross-linked polystyrene (HPS) to stabilize small Pdn and Ptn (n = 4 or 9) clusters. Unrestricted DFT calculations were carried out for benzene (BZ) adsorption at the BP level of theory using triple-zeta basis sets. The adsorption of BZ rings (stepwise from one to four) was found to result in noticeable gain in energy and stabilization of resulting adsorption complexes. Moreover, the interaction of metal clusters with HPS micropores was also addressed. For the first time, the incorporation of small clusters in the HPS structure was shown to influences its geometry resulting in the stabilization of polymer due to its partial relaxation.

Phytomass-Derived Multifunctional Activated Carbon as a “Wonder-Material”: A Paradigm Shift of Filth-to-Wealth

Activated carbon (AC) is a wonder-material that finds multifarious applications such as catalytic supports, removal of pollutants, electrodes in energy gadgets, gas storage etc. Surface area, chemical constituents and pore structures are a few traits required in the ACs which largely depend on the source of the precursors and processing methodologies adopted. In this context, the idea of recycling phytomass for producing ACs has attracted researchers seeing that the inexpensive and renewable nature of the phytomass can reduce the overall cost of producing ACs with diversified features and that it does not add CO2 to the atmosphere leading to global warming (plants release only the same amount of CO2 as they consumed while growing). Further, phytomass after their life possess no value but their conversion into ACs would be an economically profitable option leading to inexpensive ACs. As a consequent of these advantages this chapter has been planned and designed to provide certain interesting multifunctional aspects of low-cost phytomass derived ACs. The chapter is expected to provide research insights oriented towards identification of unexplored phytomass or wastes which could lead to carbon with novel properties tunable to the applications. Filth-to-wealth or in other words, recycling of wastes provides a strategy categorized under circular-bioeconomy, which is the want of the hour.

Surfactant-Free Synthesis of Three-Dimensional Perovskite Titania-Based Micron-Scale Motifs Used as Catalytic Supports for the Methanol Oxidation Reaction

We synthesized and subsequently rationalized the formation of a series of 3D hierarchical metal oxide spherical motifs. Specifically, we varied the chemical composition within a family of ATiO3 (wherein “A” = Ca, Sr, and Ba) perovskites, using a two-step, surfactant-free synthesis procedure to generate structures with average diameters of ~3 microns. In terms of demonstrating the practicality of these perovskite materials, we have explored their use as supports for the methanol oxidation reaction (MOR) as a function of their size, morphology, and chemical composition. The MOR activity of our target systems was found to increase with decreasing ionic radius of the “A” site cation, in order of Pt/CaTiO3 (CTO) > Pt/SrTiO3 (STO) > Pt/BaTiO3 (BTO). With respect to morphology, we observed an MOR enhancement of our 3D spherical motifs, as compared with either ultra-small or cubic control samples. Moreover, the Pt/CTO sample yielded not only improved mass and specific activity values but also a greater stability and durability, as compared with both commercial TiO2 nanoparticle standards and precursor TiO2 templates.

Ammonium Salts Catalyzed Acetalization Reactions in Green Ethereal Solvents

Cyclopentyl methyl ether and 2-methyltetrahydrofuran, low impact ethereal solvents forming a positive azeotrope with water, were successfully employed as solvents in the synthesis of a variety of acetals carried out under Dean–Stark conditions in the presence of heterogeneous acidic catalysts. Under these conditions, ammonium salts, either as such or supported on SiO2, performed better or equally well than widely employed homogeneous and heterogeneous acidic catalysts such as p-toluenesulfonic acid, Amberlyst 15®, or Montmorillonite K10. Several examples highlight the advantage of tuning the relative acidities of ammonium salts by appropriately selecting the counterion. Within one of these examples, our protocol clearly outweighs the classic p-toluenesulfonic acid/toluene protocol in terms of chemoselectivity. Silica-supported catalysts were characterized by SEM, TEM, and FTIR spectroscopies, as well as by N2 physisorption. Such a characterization reveals an even distribution of ammonium salts on silica, thus confirming the formation of expected catalytic supports.

Evolution of Specific Heat Capacity with Temperature for Typical Supports Used for Heterogeneous Catalysts

Heterogeneous catalysts are widely used in the chemical industry. Compared with homogeneous catalysts, they can be easily separated from the reaction mixture. To design and optimize an efficient and safe chemical process one needs to calculate the energy balance, implying the need for knowledge of the catalyst’s specific heat capacity. Such values are typically not reported in the literature, especially not the temperature dependence. To fill this gap in knowledge, the specific heat capacities of commonly utilized heterogeneous catalytic supports were measured at different temperatures in a Tian–Calvet calorimeter. The following materials were tested: activated carbon, aluminum oxide, amberlite IR120 (H-form), H-Beta-25, H-Beta-38, H-Y-60, H-ZSM-5-23, H-ZSM-5-280, silicon dioxide, titanium dioxide, and zeolite 13X. Polynomial expressions were successfully fitted to the experimental data.

A Review: Electrospinning and Electrospinning Nanofibre Technology, Process & Application

Electrospinning is a versatile and viable technique for ultra-thin fiber generation. Remarkable progress has been made with regard to the development of Electrospinning methods and the engineering of Electrospinning Nanofibre to suit or enable different applications. We aim to provide a comprehensive overview of Electrospinning, including principles, methods, materials and applications. We begin with a brief introduction to the early history of Electrospinning, followed by a discussion of its principle and its typical apparatus. Subsequently, we discuss the applications of electrospun Nanofibre, including their use as smart mattresses, filtration membranes, catalytic supports, energy harvesting / conversion / storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent developments in the application of electrospun Nanofibre by focusing on the most representative examples.

Synthesis and applications of carbon nanofibers: a review

Carbon nanofibers (CNFs) have shown great potential in multiple applications. Their versatility is derived from the possibility of tuning their physical and chemical properties. CNFs can be synthesized using two main methods: the catalytic decomposition of carbon precursors or the electrospinning and carbonization of polymers. The most appropriate method relies on the desired characteristics of the CNFs. Some of their applications include the synthesis of catalysts and catalytic supports, as electrodes for fuel cell devices, in hydrogen storage systems, and in functional nanocomposites. In this review, recent advances in the synthesis and potential applications of CNFs are examined.

Activation of persulfate by different biochars for the degradation of sulfamethoxazole

<p>Advanced oxidation processes (AOPs) based on persulfates have become very popular for in-situ water/wastewater treatment since persulfates are more stable and less costly than other oxidants such as hydrogen peroxide. The conversion of persulfates to sulfate radicals requires an activation agent, including transition metals, high temperature, ultraviolet irradiation, ultrasound irradiation, and microwaves. Recently, there have been several reports concerning the use of carbonaceous materials such as graphene, graphene oxide, carbon nanotubes, and activated carbons as persulfate activators. Biochars, the solid residue produced from biomass thermal decomposition with no or little oxygen at moderate temperatures, are low-cost materials with high surface area and desirable physicochemical properties in terms of pore size distribution, the number of functional groups, and minerals that can be employed as catalytic supports.</p><p>The aim of this work is to test whether biochar produced from malt spent rootlets (MSR) and olive kernels are suitable activators of persulfates for the degradation of sulfamethoxazole (SMX) under various operating conditions and aqueous matrices.  Olive kernels and MSR were pyrolyzed at 850 and 900<sup>o</sup>C, respectively.  The actual matrix effect on degradation was minor and so was the effect of radical scavengers. Persulfate activation seems to occur on the biochar surface through interactions with the surface functional groups, generating radicals that are not released in the solution.</p>