A comparison of the esterification of acetic acid with methanol using heterogeneous versus homogeneous acid catalysis

Abstract Background Xylo-oligosaccharide is the spotlight of functional sugar that improves the economic benefits of lignocellulose biorefinery. Acetic acid acidolysis technology provides a promising application for xylo-oligosaccharide commercial production, but it is restricted by the aliphatic (wax-like) compounds, which cover the outer and inner surfaces of plants. Results We removed aliphatic compounds by extraction with two organic solvents. The benzene–ethanol extraction increased the yield of acidolyzed xylo-oligosaccharides of corncob, sugarcane bagasse, wheat straw, and poplar sawdust by 14.79, 21.05, 16.68, and 7.26% while ethanol extraction increased it by 11.88, 17.43, 1.26, and 13.64%, respectively. Conclusion The single ethanol extraction was safer, more environmentally friendly, and more cost-effective than benzene–ethanol solvent. In short, organic solvent extraction provided a promising auxiliary method for the selective acidolysis of herbaceous xylan to xylo-oligosaccharides, while it had minimal impact on woody poplar.

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FATTY ACID ESTERIFICATION: EFFECTS OF UNSATURATION AND SYNTHESIS WITH THERMAL HEATING VIA ULTRASON AND MICROWAVES

Periódico Tchê Química ◽

10.52571/ptq.v15.n30.2018.450_periodico30_pgs_447_462.pdf ◽

2018 ◽

Vol 15 (30) ◽

pp. 447-462

Author(s):

M. C. de M. SOUZA ◽

L. DI SOUZA ◽

V. P. da S. Caldeira ◽

A. G. D. SANTOS ◽

B. ADILSON

Keyword(s):

Fatty Acids ◽

Oleic Acid ◽

Fatty Acid ◽

Energy Demand ◽

Fossil Fuels ◽

Acid Catalysis ◽

Thermal Heating ◽

Ultrasonic Methods ◽

Homogeneous Acid ◽

Acid Esterification

With the increasing selective energy demand, fossil fuels are becoming scarce and environmentally incorrect, a viable alternative to this problem being the production of biodiesel. However, the esterification and transesterification reactions used are slow, expensive and ecologically incorrect because they produce polluting waste. Thus, it is necessary to develop techniques, reagents and equipment that make them fast, cheap and environmentally friendly. This work evaluated the performance of the thermal heating, microwave and ultrasonic methods in the esterification efficiency of oleic and stearic fatty acids via homogeneous acid catalysis. The efficiency of the reaction was certificated with the variables: time, yield and conversion and the biodiesel characterization were done with TG / DTG, FTIR and NMR. Conversions were determined by TG and 1H NMR and the yield by gravimetry. The results showed conversion with all methods with differences in the analyzed variables. The yields decrease in the microwave order (52%) conduction (33%) ultrasound (30%) for reactions with oleic acid and are practically the same (22, 22 and 20), independently of the stearic acid. Among the methods used, the most efficient is the microwave, because it has a higher yield in the case of oleic acid and reducing the reaction time.

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Acid Catalysis in Sulfuric Acid-Acetic Acid Solutions. The Rate of Bromination of m-Nitroacetophenone1

Journal of the American Chemical Society ◽

10.1021/ja01302a027 ◽

1936 ◽

Vol 58 (11) ◽

pp. 2182-2187 ◽

Cited By ~ 12

Author(s):

Martin A. Paul ◽

Louis P. Hammett

Keyword(s):

Acetic Acid ◽

Sulfuric Acid ◽

Acid Catalysis ◽

Acid Solutions

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Fasteners: Acid Catalysis

Reactions ◽

10.1093/oso/9780199695126.003.0022 ◽

2011 ◽

Author(s):

Peter Atkins

Keyword(s):

Acetic Acid ◽

Acid Catalysis ◽

Positive Charge ◽

Proton Donor ◽

Electron Cloud ◽

Base Catalysis ◽

Acid Molecule ◽

General Basis ◽

Missile Attack ◽

Powerful Electron

I explained the general basis of catalysis in Reaction 11, where I showed that it accelerated a reaction by opening a new, faster route from reactants to products. One of the ways to achieve catalysis in organic chemistry is to carry out a reaction in an acidic or basic (alkaline) environment, and that is what I explore here. In Reaction 27 you will see the enormous importance of processes like this, not just for keeping organic chemists productive but also for keeping us all alive; I give a first glimpse of that later in this section too. Various kinds of acid and base catalysis, sometimes both simultaneously, are going on throughout the cells of our body and ensuring that all the processes of life are maintained; in fact they are the very processes of life. I deal with acid catalysis in this section and base catalysis in the next. The point to remember throughout this section is that an acid is a proton donor (Reaction 2) and a proton is an aggressive, nutty little centre of positive charge. If a proton gets itself attached to a molecule, it can draw electrons towards itself and so expose the nuclei that they formerly surrounded. That is, a proton can cause the appearance of positive charge elsewhere in the molecule where the nuclei shine through the depleted fog of electrons. Because positive charge is attracted to negative charge, one outcome is that a molecule may be converted into a powerful electron-sniffing electrophile (Reaction 16). Another way of looking at the outcome of adding a proton is to note that a C atom with a positive charge is a target for nucleophilic missile attack (Reaction 15). Therefore, if a proton draws the electron cloud away from a nearby atom, then its presence is like a fifth-column agent preparing a target for later attack. Let’s shrink and watch as some acid is added to a molecule that contains a –CO– group, such as acetic acid. The protons provided by the added acid are riding on water molecules, as H3O+ ions, and arrive in the vicinity of the acetic acid molecule.

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