Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: a review.

Activated carbon refers to a wide range of carbonised materials of high degree of porosity and high surface area. Activated carbon has many applications in the environment and industry for the removal, retrieval, separation and modification of various compounds in liquid and gas phases. Selection of the chemical activator agent is a major step controlling the performance and applicability of activated carbon. Here, we review chemical activators used to produce activated carbon. We compare the impregnation method with the physical mixing method used in activating with alkali hydroxides. We selected 81 articles from Google Scholar, PubMed, Scopus, Science Direct, Embase and Medlin databases. Eighteen articles report the activation with potassium hydroxide, 17 with phosphoric acid, 15 with zinc chloride, 11 with potassium carbonate, nine with sodium hydroxide, and 11 with new activating agents. Activation with phosphoric acid is commonly used for lignocellulosic material and at lower temperatures. Zinc chloride generates more surface area than phosphoric acid but is used less due to environmental concerns. Potassium carbonate, in comparison with potassium hydroxide, produces higher yields and a higher surface area for the adsorption of large pollutant molecules such as dyes. Activating with potassium hydroxide in terms of surface area and efficiency shows better results than sodium hydroxide for various applications. Also, the comparison of the physical mixing method and the impregnation method in activation with alkali metals indicates that the activated carbon obtained through physical mixing had a higher porosity than the activated carbon produced by the impregnation method.

Methods for preparation and activation of activated carbon: a review

Carbon-based functional materials hold the key for solving global challenges in the areas of water scarcity and the energy crisis. Although carbon nanotubes (CNTs) and graphene have shown promising results in various fields of application, their high preparation cost and low production yield still dramatically hinder their wide practical applications. Therefore, there is an urgent call for preparing carbon-based functional materials from low-cost, abundant, and sustainable sources. Recent innovative strategies have been developed to convert various waste materials into valuable carbon-based functional materials. These waste-derived carbon-based functional materials have shown great potential in many applications, especially as sorbents for water remediation and electrodes for energy storage. Here, the research progress in the preparation of waste-derived carbon-based functional materials is summarized, along with their applications in water remediation and energy storage; challenges and future research directions in this emerging research field are also discussed.

Carbon-Based Functional Materials Derived from Waste for Water Remediation and Energy Storage.

Metal-organic frameworks (MOFs), which consist of central metal nodes and organic linkers, constitute a fast growing class of crystalline porous materials with excellent application potential. Herein, a series of Mn-based multimetallic MOF (bimetallic and trimetallic MIL-100) nano-octahedra are prepared by a facile one-pot synthetic strategy. The types and proportions of the incorporated elements can be tuned while retaining the original topological structure. The introduction of other metal ions is verified at the atomic level by combining X-ray absorption fine structure experiments and theoretical calculations. Furthermore, these multimetallic Mn-based MIL-100 nano-octahedra are utilized as sulfur hosts to prepare cathodes for Li-S batteries. The MnNi-MIL-100@S cathode exhibits the best Li-S battery performance among all reported MIL-100@S composite cathode materials, with a reversible capacity of ≈708.8 mAh g-1 after 200 cycles. The synthetic strategy described herein is utilized to incorporate metal ions into the MOF architecture, of which the parent monometallic MOF nano-octahedra cannot be prepared directly, thus rationally generating novel multimetallic MOFs. Importantly, the strategy also allows for the general synthesis and study of various micro-/nanoscale MOFs in the energy storage field.

Rational Design and General Synthesis of Multimetallic Metal-Organic Framework Nano-Octahedra for Enhanced Li-S Battery.

3.2. One-Step Sol-Gel Method 2187 4. Structural Characterization 2188 4.1. XRD Studies 2188 4.2. FTIR Studies 2189 4.3. Raman Studies 2189 4.4. TG and DTG Analysis 2190 4.5. SEM and TEM 2190 5. Structure of Sulfated Zirconia 2191 6. Superacidity and Measurement 2192 6.1. Uncertainties about Superacidity 2192 6.2. Acidity Measurement 2193 7. Application of Sulfated Zirconia Catalysts 2193 7.1. Biginelli Reaction 2193 7.2. Knoevenagel Condensation 2194 7.3. Synthesis of Formamidine 2194 7.4. Acylation of Aromatic Compounds 2194 7.4.1. Acylation of Benzene 2194 7.4.2. Acylation of Substituted Benzenes 2194 7.4.3. Acylation of Naphthalenes and Anthracenes 2195

Organic syntheses and transformations catalyzed by sulfated zirconia.

Surface characterization and catalytic activity of sulfated tin oxide catalyst

WO3 loaded on nano-crystalline sulfated tin oxide solid acid catalyst has been synthesized and studied for selective nitration of phenol. The catalysts were characterized by various analytical and spectroscopic techniques including thermal analysis, powder X-ray diffraction (XRD), N2 adsorption and FTIR spectra. The surface acidity was measured by no aqueous potentiometric titration and FTIR spectra of chemically adsorbed pyridine. The acidity measurements showed that the samples contain both Lewis and Bronsted acid sites; moreover, the total acidity increases with the rise of WO3 content up to 30 wt.% (monolayer coverage) and decreases thereafter. The results also showed the possibilities of interaction of WO3 with sulfate and/or SnO2 surface that led to some changes in the surface structure of the catalyst. The catalytic activity well correlates with Bronsted acid sites of these catalysts. The effect of the reaction parameters, i.e. reactants molar ratio, reaction temperature and time was also investigated. The catalyst was reused for five times with excellent percentage conversion and high selectivity towards ortho isomer. The possible reaction mechanism for the formation of ortho and para isomers was also discussed.

Selective nitration of phenol over nanosized tungsten oxide supported on sulfated SnO2 as a solid acid catalyst

Structural, photocatalytic, biological and catalytic properties of SnO 2 /TiO 2 nanoparticles

Photocatalytic activity of mesoporous WO3/TiO2 nanocomposites for the photodegradation of methylene blue

Nanocrystalline sulfated tin oxide with different sulfate contents (5–30 wt%) were prepared from hydroxylated tin oxide obtained by the precipitation method, followed by wet impregnation with SO 4 2− species using a sulfuric acid solution. In samples calcined at 400, 500 and 600 °C the characterization of the solids was made by DTA, XRD and nitrogen adsorption. The strength and number of acid sites were determined by nonaqueous titration of n-butylamine in acetonitrile. Both Bronsted and Lewis acid sites were determined by FTIR spectra of pyridine adsorbed. Sulfated tin oxides were tested in the synthesis of 7-hydroxy-4-methyl coumarin via solvent free Pechmann reaction of resorcinol:ethylacetoacetate (molar ratio 1:2), at 120 °C. DTA measurements showed that SO 4 2− addition tends to slow down the formation of SnO 2 crystallites. XRD profiles showed that the sulfating inhibits the SnO 2 crystal growth. The SO 4 species remained strongly bonded at the SnO 2 surface stabilizing its crystallite size against sintering and it acts as a structure porogen director mediating nanoparticle growth and assembly yielding a mesostructured form of SnO 2 with wormhole morphology and high thermal stability. The surface areas of the investigated samples were influenced with the sulphate content and calcination temperature. The acidity measurements showed that the total acidity increases with the rise of sulfate content up to 25 wt%. FTIR spectra of pyridine adsorbed on the catalysts showed the presence of both Bronsted and Lewis acid sites. The formation of 7-hydroxy-4-methyl coumarin increases with the increase of surface acidity showing a maximum when the sulfate content and calcination temperature were 25 wt% and 400 °C, respectively.

Awad I. Ahmed

Papers

Surface characterization and catalytic activity of sulfated tin oxide catalyst

Selective nitration of phenol over nanosized tungsten oxide supported on sulfated SnO2 as a solid acid catalyst

Structural, photocatalytic, biological and catalytic properties of SnO 2 /TiO 2 nanoparticles

Photocatalytic activity of mesoporous WO3/TiO2 nanocomposites for the photodegradation of methylene blue

Nanostructure sulfated tin oxide as an efficient catalyst for the preparation of 7-hydroxy-4-methyl coumarin by Pechmann condensation reaction