Dawid Lisicki

Nowadays, a global trend in the chemical industry is the search for and implementation of methods that are environmentally benign and consistent with the principles of green chemistry. In response to this concept, environmentally friendly deep eutectic solvents (DESs) enable chemical processes to be conducted under mild, non-toxic conditions, and thus align with the philosophy of green chemistry. This study aimed to evaluate the applicability of eutectic mixtures based on choline chloride or tetramethylammonium chloride as hydrogen bond acceptors (HBA) in oxidation processes. The oxidation of ethylbenzene with oxygen was selected as a model reaction, leading to a mixture of acetophenone, 1-phenylethanol, ethylbenzene hydroperoxide, benzaldehyde, and benzoic acid. The results demonstrate that the use of a DES composed of choline chloride and triethylene glycol, in combination with cobalt(II) chloride or cobalt(II) acetylacetonate, enables the achievement of relatively high ethylbenzene conversion (20.3-26.3%) along with high selectivity toward the main product, acetophenone (88.7-91.2%). Furthermore, the study confirmed that both the substrate loading and the amount of eutectic mixture have a significant impact on conversion and on the composition of ethylbenzene oxidation products. The obtained results indicate that the DES system based on choline chloride and triethylene glycol can be recovered and reused up to six times without a significant loss of catalytic activity.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Nicotinic acid (NA) is a heteroaromatic carboxylic acid mainly used as feed, in breakfast cereals, and as a beverage additive. Moreover, it is used as an anti-pellagra drug and as an ingredient in multivitamin supplements. It is manufactured using the Lonza process from 3-ethyl-3-methylpyridyne as a raw material using HNO₃ as the oxidant agent. However, the use of such an oxidant is connected with greenhouse gases, thus making the technology non-ecological. Another industrial process is oxidative ammonolysis of 3-picoline followed by hydrolysis of a reaction intermediate to NA. This paper presents the results of research on the selective oxidation of 3-picoline with oxygen to NA. Bromide organic salts, including ionic liquids, N-hydroxyphtalimide, and cobalt(II) salts, were used as the catalysts. The reaction was carried out with acetic acid (AcOH) as a solvent. The bromide salts imidazolium bromide, quaternary ammonium bromide, and quaternary phosphonium bromide were used. They also fill the role of corrosion inhibitors caused by the acidic and highly oxidative reaction environment.

An efficient method for the synthesis of 2-ethylhexanoic acid has been reported. The method involves the 2-ethylhexanal oxidation using oxygen or air in the presence of N-hydroxyphthalimide in isobutanol as a solvent under mild conditions. A high selectivity of >99% for 2-ethylhexanoic acid was achieved. The influence of catalyst amount, solvent type and quantity, temperature, and reaction time on the product composition was studied. The developed method is in line with the global trends aimed at developing green oxidation processes as well as having potential for implementation in industry due to its high selectivity, cost-effective oxidizing agent, and mild reaction conditions. The use of isobutanol as a solvent is of crucial importance providing an opportunity for potential producers of 2-EHAL from butanal to employ the less valuable alcohol.

This paper presents a not previously reported catalytic system consisting of transition metals Co²⁺ and Mn²⁺ and alkyl nitrites R-ONO for the oxidation of cyclohexanone with oxygen to adipic acid. The influence of type and amount of catalyst, temperature, time, and type of raw material on conversion and product composition were determined. In addition, the oxidation of selected cyclic ketones such as cyclopentanone, cyclohexanone, cyclooctanone, cyclododecanone, 2-methylcyclohexanone, 3-methylcyclohexanone, and 4-methylcyclohexanone in acetic acid as solvent was performed. The results showed that R-ONO systems, under established reaction conditions, form NO·radicals, which oxidize to NO₂ under a strong oxidization reaction environment. The Co²⁺/Mn²⁺/NO₂ system was shown to be highly active in the oxidation of cyclic ketones with oxygen.

Herein, an alternative method for adipic acid (AA) synthesis of industrial importance has been reported. The proposed novel method involves the one-step, solvent-free oxidation of a cyclohexane/cyclohexanone (CH/CH=O) mixture, with a cheap oxidizing agent such as O₂ or air under mild conditions in the presence of N-hydroxyphtalimide (NHPI) and transition metals as catalysts. It has been showed that CH/CH=O mixture under applied mild conditions oxidized faster than CH and CH=O separately. This was due to the greater oxidizability of CH=O compared to CH. The peroxyl radicals formed by CH=O oxidation initiated the oxidation of the less reactive CH. Additionally, CH=O increased the polarity of the reaction mixture, promoting the solubility of NHPI. The influence of type and amount of catalyst, cyclohexane to cyclohexanone ratio, temperature, time, type of oxidizing agent on the composition of CH/CH=O oxidation products have been reported.

Nicotinic acid is a naturally occurring pyridine carboxylic acid, contained in vitamin PP, an essential nutrient for humans and animals, and used as an antipelagic agent. Nicotinic acid can be made from tryptophan by plants and animals but is usually not completely bioavailable. Industrially, nicotinic acid is produced mainly by oxidation of 5-ethyl-2-methylpyridine with nitric acid. One of the by-products of the process is nitrous oxide, a gas that is difficult to recycle and manage, with a greenhouse effect 300 times stronger than CO₂. A new technology for the industrial production of nicotinic acid is undoubtedly necessary to meet the needs of green chemistry and not burden the environment. We carried out a literature review on ecological methods to produce nicotinic acid from commercially available raw materials such as 3-methylpyridine and 5-ethyl-2-methylpyridine, especially focusing on those methods with potential industrial applications.

Studies on the oxidation of α-olefins via the two-stage method are presented. The new method consisted of oxidizing C30+ α-olefins with hydrogen peroxide (2 equiv.) and subsequent oxidation with oxygen. Products with high acid numbers (29–82 mgKOH/g) and saponification numbers (64–140 mgKOH/g) were obtained and compared with products obtained using only hydrogen peroxide or oxygen. It was demonstrated that H₂O₂ can be partially replaced by oxygen in the oxidative cleavage reaction of α-olefins. N-hydroxyphthalimide in combination with Co(acac)₂ demonstrated high activity in the oxidation stage using oxygen.