Carbon-based solid acid

As an advance in this area, the same group developed a sugar-based catalyst, which made its first appearance in 2005. In this work the preparation of the carbon-based solid acid was carried out using u-glucose as precursor, again the approach consisted in the partial carbonisation of the precursor followed by its sulfonation with sulfuric acid at 150 °C (Figure 4.2). 

Carbon-based solid acids exhibited remarkable activity for many acid-catalyzed reactions including esterification, Friedel-Crafts alkylation, hydrolysis, and hydration. Important reactions for biomass transformations, such as the transesterification of fatty acids with alcohols (biodiesel production) [64] and... 

The disadvantages of using mineral acids such as concentrated HCl or H2SO4 to hydrolyse biomass is that they are toxic, corrosive, hazardous and difficult to recycle. The use of heterogeneous solid acids can ease product separation and provide better catalyst recyclability. For example, mesoporous transition metal oxides have been used in biomass transformations. " Polymer-based acids have been employed for the hydrolysis of various organic substrates. " In particular, carbon-based solid acids made by sulfonation of carbonized polymers, such as the solid acid shown in Figure 7.7, have shown promise. Sulfonated bio-char has been similarly used. ... 

Figure 7.7 A form of carbon-based solid acid.

Rao, B. V. S. K., Chandra Mouli,K., Rambabu,N.,Dalai,A. K., and Prasad, R. B. N. Carbon-based solid acid catalyst from de-oiled canola meal for biodiesel production. Catal Comm 14,20-26 (2011). 

Rapeseed-based biodiesel production has been widely studied in terms of optimization and kinetics of alkali catalyzed transesterihcation reaction (Luque et al., 2011). Recaitly, production of solid base catalysts, such as Ca/Zr mixed oxide catalysts (Liu et al., 2015), CaO-based catalysts or4-sulfophenyl activated carbon-based solid acid catalyst, has been reported with a performance similar to commacial heterogeneous catalyst Amberly st-15 (Malins et al., 2015). Present researches are also focusing on the use of supercritical ethanol and methanol as reagents to avoid drawbacks due to the use of homogeneous catalysts (Farobie and Matsumura, 2015a,b). Technoeconomic and performance studies on the use of supercritical methanol concluded that lower direct costs and environmental impacts are achieved at highest biodiesel yields, where oil consumption per unit of biodiesel... 

Shu, Q., et al., 2010. Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid add catalyst. Applied Energy 87 (8), 2589—25%. Available at http //www.scienceditect.eom/science/article/pii/S0306261910000887 (accessed 26.05.14.). 

Other acids have also been explored. For instance, a heleropoly acid catalyzed Friedel-Crafts alkylation of indole and pyrrole with enones and electron-deficient olefins in water at room temperature, affording good yields at 0.3mol% catalyst loading [112]. Similarly, a carbon-based solid add was shown to catalyze effidendy the reaction of indoles with a,p-unsaturated carbonyl compounds in water, and the... 

The chemical composition with respect to Si and metallic impurities (mainly Fe, Ca, Al) is generally determined by wet chemical methods in combination with standard spectroscopic techniques (AAS, AES, XRF) (Table 8) [224-226]. A precondition is the dissolution of the powder. Typical dissolving processes are fusion with sodium carbonate or mixtures of sodium carbonate and boric acid, with alkaline hydroxides [225, 226] and special acid treatments [225]. A more effective analysis based on optical emission spectroscopy allows the direct analysis of impurities in the solid state and requires no dissolution step [227]. 

Johnson (9) had proposed that one could titrate the acidity of colored solids by adding white solid acids and then titrate while observing the color changes on the white solid acids. This idea is based on the assumption that the colored and white solids do not interact with each other but only with the titrant and dyes. This assumption has been used for many years without challenge, but T. Fabish (14) has just recently shown that carbon blacks do indeed interact with silica-alumina particles and can appreciably change their surface acidity. 

The TC content of a sample can be subdivided into many fractions depending on the particular needs. The classification is often based on purely operational parameters, for example, the method used to release the carbon from the sample (examples include purgeable organic carbon—POC or acid-released organic carbon—AROC). Table 10.1 lists examples of the different fractions of TC that can be determined in liquid and solid samples. This particular classification is based on the determination of carbon content, but similar classifications could be prepared for other elements present in the pollutants. 

Carbon is a prominent catalyst support material as it allows the anchoring of metal particles on a substrate which docs not exhibit solid acid-base properties. Carbon is finally a catalyst in its own right, enabling the activation of oxygen and chlorine for selective oxidation, chlorination, and dechlorination reactions. 

Fulvic acids. Marine sedimentary humic substances soluble in base and acid (fulvic acids) have previously been examined by and NMR (12). The dominant structural components were postulated to be polysaccharide - like substances, probably polyuronic acids. Solid-state NMR spectra of fulvic acids isolated from a number of marine and estuarine sediments are shown in Figure 1. Major peaks at 72 and 106 ppm betray the overwhelming presence of polysaccharide -like substances, and, as shown by Hatcher and others (12.), the moderate peak for carboxyl or amide carbon at 175 ppm suggests that these polysaccharides are more like polyuronides. Aromatic carbons (110 to 160 ppm) are decidedly minor components. Aliphatic carbons (0-50 ppm) are also minor components. H NMR spectra shown by Hatcher and others (12) indicate that these aliphatic structures are highly branched. 

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