Mineral acid

About: Mineral acid is a research topic. Over the lifetime, 4130 publications have been published within this topic receiving 30186 citations. The topic is also known as: inorganic acid.

Conversion of hemicellulose into furfural using solid acid catalysts in γ-valerolactone.

Abstract: The effective conversion of lignocellulosic biomass into fuels and chemicals requires the utilization of both hemicellulose and cellulose, consisting primarily of C5 and C6 sugars, respectively. Catalytic conversion strategies for hemicellulose are of particular importance because biological conversion of C5 sugars is not as efficient as the conversion of C6 sugars. In addition, C5 sugars/oligomers are produced as a side stream in the pulp and paper industry, which provides an opportunity to create value-added products. Among the products that can be obtained from C5 sugars, furfural is a particularly promising option, as it can replace crude-oil-based organics for the production of resins, lubricants, adhesives, and plastics, as well as valuable chemicals, such as furfuryl alcohol and tetrahydrofurfuryl alcohol. Current methods for production of furfural from hemicellulose use mineral acid catalysts which are corrosive, difficult to recover from the reaction mixture, and pose environmental and health risks. Importantly, current yields for the production of furfural in water are low (e.g., < 60%). Biphasic systems improve the yield of furfural and its separation from the mineral acid, and can be employed for lignocellulosic biomass which has been pretreated with mineral acids. Ideally, it is desirable to replace mineral acids with solid acids in lignocellulose processing. However, the use of solid acid catalysts in an aqueous environment is challenging in view of catalyst degradation and/or leaching in aqueous solution at elevated temperatures (e.g., 430 K). Moreover, biphasic systems typically require the use of salts to achieve good separation of the phases and to improve the efficiency of the extracting organic layer, and solid catalysts cannot be used in this case because the exchange of protons on the catalyst with cations in solution leads to deactivation of the heterogeneous catalyst. The aforementioned difficulties associated with the conversion of xylose into furfural can be alleviated by using gvalerolactone (GVL) as a solvent in a monophasic system with solid acid catalysts. Importantly, GVL is a solvent which can be produced from lignocellulose, and Horvath and coworkers have been strong proponents for the use of GVL as a solvent in biomass processing. Using GVL as the solvent increases the rate of xylose conversion and decreases the rates of furfural degradation reactions. In addition, furfural has a higher volatility than GVL and can thus be obtained as a top product in a distillation step. Alternatively, GVL, a valuable chemical with multiple uses, can be synthesized as the end product of the process, thereby eliminating product purification steps. Furthermore, the use of a monophasic reaction system eliminates the loss of the product in the aqueous phase, the need for a liquid–liquid separation step, and reduces mixing requirements. Additionally, by minimizing the concentration of water present in the reactor, it is possible to use solid catalysts for the conversion of xylose (and xylose oligomers) into furfural with minimal degradation of the catalyst and without leaching of acid sites into solution. Figure 1 shows the furfural yields achieved, after complete xylose conversion, for different solid acid catalysts. The catalysts contained Bronsted and/or Lewis acid sites, and just GVL was used as the solvent. Even though water was not added in the reaction mixture, it is a by-product of dehydration, and its concentration can reach up to 0.7 wt% with quantitative yields of furfural. Catalysts, such as g-Al2O3 (galumina), Sn-SBA-15, and Sn-beta, which contain only Lewis acid sites, resulted in the lowest yields of furfural (see Figure S1 in the Supporting Information for FTIR measure-

Hydrodeoxygenation of lignin-derived phenols into alkanes by using nanoparticle catalysts combined with Bronsted acidic ionic liquids

Abstract: The transformation of lignin-derived phenolic compds. to alkanes was achieved using catalysts based on Bronsted acidic ionic liqs. (ILs). The catalytic system is composed of metal nanoparticles (NPs) and a functionalized Bronsted acidic IL immobilized in a nonfunctionalized IL, allowing hydrogenation and dehydration reactions to occur in tandem. Compared to previous systems that are either performed with metal sulfite or with mineral acid/ supported metal catalysts in water, this system allows lignin derivs. to be upgraded in an efficient and less energy-demanding process.

Individual elution of noradrenaline (together with adrenaline), dopamine, 5-hydroxytryptamine and histamine from a single, strong cation exchange column, by means of mineral acid-organic solvent mixtures.

Abstract: Individual elution of noradrenaline (together with adrenaline), dopamine, 5-hydroxytryptamine and histamine from a single, strong cation exchange column, by means of mineral acid-organic solvent mixtures Few methods have been published which demonstrate the quantitative measurement of the biogenic amines noradrenaline, adrenaline, dopamine, 5-hydroxytryptamine (~-HT) and histamine, and their metabolites, in the same, small sample of tissue after a single extraction and purification procedure. Recently Sadavongvivad (1 970) published a technique employing butanol in the organic extractions of catecholamines, and of ~ H T together with histamine, from the same, small sample of tissue. We have developed a column adsorption chromatographical procedure which permits the total amount of each amine, derived from the tissue, to be concentrated into small, individual fractions. Noradrenaline together with adrenaline has been separated from dopamine on strong cation exchange columns of dimensions 50 mm (in buffer) by 4.2 mm (i.d.). The resin used is Dowex 50W-X4, 200400 mesh, sodium form (Bertler, Carlsson & Rosengren, 1958, as later modified by Carlsson & Lindqvist, 1962). Noradrenaline, together with adrenaline, is eluted with 8 ml, and dopamine with the following 12 ml, aqueous N HCl. Adopting the procedures of Kahlson, Rosengren & Thunberg (1963) and of Green & Erickson (1964), we were able to elute histamine with 5 ml of aqueous 2~ HCl after eluting the catecholamines. Using large volumes (up to 20 ml) of eluant, ~ H T could be eluted after histamine with 4 -6~ aqueous HC1 or 0 . 0 1 ~ aqueous NaOH, the latter being an adaptation of the technique of Wiegand & Scherfling (1962). The eluate volume could be reduced to 4 ml by eluting with 3~ ethanolic (50%) HCl, when adopting the procedure of Schildkraut, Schanberg & others (1969). Whilst the procedure so far described permits the separation of all the amines, with the exception of noradrenaline from adrenaline, some further interesting observations and improvements were made. In common with ~ H T , the elution of noradrenaline, adrenaline and dopamine is also greatly facilitated by the use of certain