Influence Of Acid Catalysts Research Articles

Microwave radiation-assisted synthesis of levulinic acid from microcrystalline cellulose: Application to a melon rind residue

The circular economy considers waste to be a new raw material for the development of value-added products. In this context, agroindustrial lignocellulosic waste represents an outstanding source of new materials and platform chemicals, such as levulinic acid (LA). Herein we study the microwave (MW)-assisted acidic conversion of microcrystalline cellulose (MCC) into LA. The influence of acidic catalysts, inorganic salt addition and ball-milling pre-treatment of MCC on LA yield was assessed. Depolymerization and disruption of cellulose was monitored by FTIR, TGA and SEM, whereas the products formed were analyzed by HPLC and NMR spectroscopy. The parameters that afforded the highest LA yield (48 %, 100 % selectivity) were: ball-milling pre-treatment of MCC for 16 min at 600 rpm, followed by MW-assisted thermochemical treatment for 20 min at 190 °C, aqueous p-toluenesulfonic acid (p-TSA) 0.25 M as catalyst and saturation with KBr. These optimal conditions were further applied to a lignocellulosic feedstock, namely melon rind, to afford a 51 % yield of LA. These results corroborate the suitability of this method to obtain LA from agroindustrial wastes, in line with a circular economy-based approach.

Influence of acidic catalysts in Hydrothemal Carbonization (HTC) process for synthesis of carbon nanomaterial prepared from horse manure

Influence of acidic catalysts in Hydrothemal Carbonization (HTC) process for synthesis of carbon nanomaterial prepared from horse manure

Influence of acid catalyst on two step transesterification of Karanja oil with high free fatty acids

Karanja oil methyl ester (KOME) was produced by the two step transesterification of oil with an alcohol in the presence of various acid catalysts and base catalysts. The best result was obtained with H2SO4 as acid catalyst and KOH as base catalyst; the yield was 97% at 60°C after 150 min. The high yield was observed due to the reduction of free fatty acids (FFA) % by using an acid catalyst in the first step of transesterification. HCl and H3PO4 was less active than H2SO4 during the process as it presented very low ester yields for the various molar ratios of fatty acid to alcohol studied. The fatty acid profile of the oil (palmitic acid: 11.64%; stearic acid: 7.70%; docosanoic acid: 4.46%; tetracosanoic acid: 1.08%; linolenic acid: 16.66%; oleic acid: 51.61%; eicosanoic acid: 1.33) and the different reactive actions of the acids were responsible for the observed differences in conversion to methyl esters. The result attained by this study might contribute to the economic utilization of a nonedible feedstock.

Influence of acid catalysts on the structural and magnetic properties of nanocrystalline barium ferrite prepared by sol–gel method

BaFe 12O 19 powders with nanocrystalline size were prepared by sol–gel techniques. Nitric, hydrochloric, acetic and stearic acid were used to improve the magnetic properties. Amorphous gels were formed with Fe/Ba molar ratio of 10.5. Then powders were obtained by subsequent heat treatment at 800–1000 °C for 1 h. Barium ferrite powder was also synthesized by solid state reaction at 1210 °C. X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM) experiments were conducted to evaluate structural properties of the samples. The value of the effective magnetic susceptibility was measured. The results show that the magnetoplumbite structure was formed in all of the powders. The TEM observation showed that the minimum particle size (20 nm) was produced with the stearic acid catalyst. The highest value of the effective magnetic susceptibility was achieved also using stearic acid.

Catalyzed Beckmann rearrangement of cyclohexanone oxime in heterogeneous liquid/solid system: Part 2: Influence of acid catalysts and organic promoters

The influence of some transition metal oxide promoters in the catalyzed Beckmann rearrangement of cyclohexanone oxime was studied by preparing several heterogeneous H 2SO 4/M/SiO 2 catalysts using SiO 2 as support and H 2SO 4 as acid source. A definite effect of each metal has been observed and the best results have been obtained with Cr-, Zr- and Zn-oxides based promoter, which have shown an improved selectivity towards ɛ-caprolactam formation if compared to the H 2SO 4/SiO 2 catalytic system. Moreover, the influence of some organic promoters on the reaction pathway was investigated. Acetic and trifluoroacetic anhydrides gave the best results, even if only the latter allowed the rearrangement even without solid acid catalysts. The transacetylation of the cyclohexanone oxime by using the acetyl caprolactam, which is the product of rearrangement of the acetyl cyclohexanone oxime, was studied for developing a step wise catalytic cycle. Finally, some preliminary results on a homogeneous organic catalyzed process are reported.

ChemInform Abstract: Friedel—Crafts Chemistry. Part 21. Cyclization versus Elimination Behavior of Some 1‐Naphthyl‐Containing Carbinols under the Influence of Acid Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Friedel-Crafts Chemistry. XXI. Cyclisation versus Elimination Behaviour of some 1-Naphthyl-containing Carbinols under the Influence of Acid Catalysts

Friedel-Crafts Chemistry. XXI. Cyclisation versus Elimination Behaviour of some 1-Naphthyl-containing Carbinols under the Influence of Acid Catalysts

Solid‐state polyamidation of hexamethylenediammonium adipate. II. The influence of acid catalysts

AbstractLoss of diamine and distinct transition phenomena from the solid to the melt state restrain solid‐state polymerization (SSP) of nylon salts from industrial application. To depress these phenomena temperatures well below the melting point of the starting material are employed, resulting however in low reaction rates. The need to use catalysts arises and accordingly in this study hexamethylenediammonium adipate (HMA) particles were polymerized containing a strictly controlled amount of uniformly distributed catalyst. The catalysts included boric, sulphuric, and phosphoric acids with boric acid being the most effective in accelerating the reaction while eliminating the tendency to agglomeration. In general, catalyst concentration up to a critical value plays a considerable role in the overall behavior. Furthermore, in agreement with non catalytic processes, the reaction temperature remains an influential parameter. © 1994 John Wiley & Sons, Inc.

The isomerization of α‐pinene oxide with Brønsted and Lewis acids

Abstractα‐Pinene oxide (2) is a very reactive substrate which isomerizes rapidly under the influence of acid catalysts. A large number of products can be formed from a single intermediate. Selectivity to the industrially important campholenic aldehyde can be achieved with metal‐halogen compounds, especially zinc chloride and zinc bromide. A possible explanation for this behaviour is offered, stipulating a stabilized carbenium‐ion intermediate. Protonic catalysts are typically highly active but unselective. No evidence was found for the earlier reported selectivity to campholenic aldehyde with zeolite catalysts.

Chemical Stablilisation of Sand : Part VIII Furan Resins as Dune and Coastal Sand Stabiliser

Studies on furan resin as dune sand stabiliser are presented. Influence of acid catalysts, viz. phenol disulphonic acid, sulphuric acid, hydrochloric acid and phosphoric acid and other catalysts, viz. trichlorotoluene and benzoyl chloride along with promoters, zinc chloride and ferric chloride, on the strength of stabilised furan resin-sand specimens has been discussed. Optimisation studies on resin content, catalysts and promoters and curing conditions have revealed that maximum strength of 260 kg/cm/sup 2/ of the standard specimens made by compaction of coastal sand using furan resins (10 per cent), sulphuric acid (9N, 30 per cent) and a curing time of 2 hr at 40 degree Centigrade is higher than the 170 kg/cm/sup 2/ of specimens made of Rajasthan desert sand. Sandy patches stabilised by seepage technique recorded a maximum strength of 125 kg/cm/sup 2/. Physico-chemical characteristics of this system and effect of environment on stabilised specimens have also been studied and field trials conducted successfully. This resin-catalyst system would be extremely useful in humid and saline field (coastal) areas for different military applications.

On the modelling of catalytic activity in homogeneous liquid phase acid-base reactions

Many industrial reactions take place under the influence of acid catalysts in a homogeneous liquid phase, but very little information is available on the modelling of this catalysis from a chemical engineering point of view. Most physico-chemical discussions have led to complex models with a considerable number of unknown parameters. In a previous work, a power law for the influence of the Hammett acidity function on the chloromethylation of toluene in a complex medium with acetic acid, hydrochloric acid and zinc chloride was reported. This work describes the modelling of the acid catalytic activity as a function of the mixture composition. Taking into account that third order polynomial correlations have been used for the excess of acidity in hydrochloric acid-water mixtures, similar correlations have been obtained for hydrochloric acid-acetic acid-zinc chloride-water mixtures as a function of hydrochloric acid concentration. Parameters of the correlation are given depending on the amounts of acetic acid and zinc chloride, which are usually constant for each reaction. Correlations for the excess of acidity in complex mixtures solve the usual problem of the composition influence on the kinetic constant, which has been found in many acid-catalyzed reactions, allowing a mathematical description for the quantitative influence of the different acids on the reaction rate.

Influence of acid catalysts on the solid-state polyamidation of dodecamethylenediammonium adipate

Solid-state polyamidation is an alternative route for polyamide synthesis. Solid-state polyamidation of dodecamethylenediammonium adipate was studied in the presence of acid catalysts. Boric acid proved to be the most effective catalyst, followed by sulphuric acid, so that—even at high reaction rates—the reaction was maintained in the solid state throughout the process. On the other hand, phosphoric acid showed a clearly weaker action resulting eventually in a transition of the process from the solid to the melt state, in accordance with noncatalysed behaviour. In general, catalyst concentration plays a considerable role in the catalytic effectiveness obtained.

Erosion of poly(ortho ester) matrices in buffered aqueous solutions

The influence of acid catalysts on the erosion rate of a poly(ortho ester) matrix in aqueous buffered solutions has been investigated. In strong acid solutions, the erosion rate appears to be directly proportional to the hydronium ion activity in the dissolution medium. The catalytic power of the hydronium ion in a solution prepared with perchloric acid appears to be greater compared with a solution of hydrochloric acid at the same pH. The contribution of free acid species depends on their p K a but more importantly on their hydrophobicity. For relatively hydrophilic acid, the reaction occurs primarily at the surface of the polymeric device. The many fold increase in the erosion rate in solution of more hydrophobic acids is attributed to the preferential partitioning of the free acid species into the surface layer of the matrix. In this case, the hydrolytic cleavage of the polymer molecules occurs both at the liquid— solid interface and in a reaction zone beneath the surface of the device.

ChemInform Abstract: Influence of Some Acidic Catalysts on the Condensation of Indene with Formaldehyde.

AbstractThe influence of acidic catalysts (H2SO4, HCl, p‐toluenesulfonic acid) on the condensation of the title compound (I) and (II) was investigated.

Chemical and Physical Effects of Finishing Cotton With Methylol Derivatives of Ethyleneurea

A study has been made of the mechanism by which cotton is made wrinkle resistant by dimethylol ethyleneurea. Estimates are made of the length of cross-links and the relative effect of several factors, including processing conditions, cross-linkage, and acid damage, on the loss in strength of the fabric on treatment. ' Various methylol derivatives of ethyleneurea were used in the study of the effect on chemical and physical properties. It has been demonstrated that the methylol deriva tives of ethyleneurea react chemically with cellulose under the influence of acidic catalysts. Metallic salts are most efficient in promoting this reaction. Both mono functional and difunctional compounds react with the cellulose. The latter, however, cause cross-linkage, which effects marked changes in the physical properties of the treated cotton fabric, particularly wrinkle resistance. Dimethylol ethyleneurea forms cross-links averaging 1.4-1.5 ethyleneurea residues in length. These residues are con nected by methylene groups. The effects of variations in catalyst, composition of the finishing agent, and curing conditions are shown. Relation of the findings to practical finishing is discussed.