Selective oxidation of o‐chlorotoluene to o‐chlorobenzaldehyde catalyzed by (Co,Mn)(Co,Mn)₂O₄ catalysts

Abstract

Catalytic oxidation of chlorotoluene is an important reaction for the production of chlorobenzaldehyde. Many works have focused on the oxidation of p-chlorotoluene, while little attention has been paid to the oxidation of o-chlorotoluene (OCT). Herein, we, for the first time, report on the selective oxidation of OCT to o-chlorobenzaldehyde (OCBD) with a cobalt-manganese composite oxide ((Co,Mn)(Co,Mn) 2 O 4 ) as a catalyst and O 2 as a green and free oxidant. The Co centres are slightly more active than the Mn centres toward the catalytic oxidation of OCT. However, the Co sites seem active enough to further oxidize the OCBD to o-chlorobenzoic acid. It is also found that the crystallinity of the (Co,Mn)(Co,Mn) 2 O 4 catalysts or the valence state of the surface cations in the catalysts affects the activity and selectivity.

Hierarchical 0D/2D Co3O4 hybrids rich in oxygen vacancies as catalysts towards styrene epoxidation reaction

“…The catalytic oxidation of hydrocarbons is a very important reaction in the chemical industry [1][2][3][4][5]. Among the various oxidation reactions, the catalytic epoxidation of alkenes has aroused much attention in recent years both academically and industrially since epoxide products are vital intermediates in pharmaceutical industrials and production of fine chemicals [6][7][8][9][10][11][12].…”

Catalytic Oxidation of o-Chlorotoluene with Oxygen to o-Chlorobenzaldehyde in a Microchannel Reactor

“…On the basis of the experimental investigation, the optimum reaction conditions for the aerobic oxidation of OCT to synthesize OCBD in a microchannel reactor were concluded to be the following: acetic acid/H 2 O as the solvent (aq, 1.65 wt %), 0.88 mol % catalyst with a Co/Mn/Br molar ratio of 0.3:0.3:1, an oxygen/OCT molar ratio of 5.5:1, a residence time of 9.4 s, a reaction temperature of 423 K, and an oxygen pressure of 0.5 MPa. Under these conditions, the conversion of OCT was 10.3% with a selectivity for OCBD of 71.8%, corresponding to an OCBD yield of 7.4%, which is higher than that in the literature. ,,, …”

“…o -Chlorobenzaldehyde (OCBD) is an important intermediate for the synthesis of drugs, dyes, and pesticides. − There are several methods to synthesize OCBD, which include hydrolysis of o -chlorobenzal chloride, electrochemical oxidation, and direct oxidation of o -chlorotoluene (OCT) with hydrogen peroxide or molecular oxygen. ,,, Very recently, it was reported that OCBD could also be synthesized by iron-catalyzed oxidation of OCT with K 2 S 2 O 8 as the oxidant in the presence of excess polymethylhydrosiloxane or molecular oxygen over a CdS–ZnS photocatalyst. , Until now, however, OCBD has mainly been produced in industry through side-chain chlorination of OCT to form o -chlorobenzal chloride followed by hydrolysis, which suffers from the disadvantages of a complicated process and serious environmental pollution. It is better to synthesize OCBD via aerobic oxidation of OCT because of the low cost, ready availability, environmental friendliness, and atom economy of molecular oxygen as an oxidant.…”

“…It is better to synthesize OCBD via aerobic oxidation of OCT because of the low cost, ready availability, environmental friendliness, and atom economy of molecular oxygen as an oxidant. In the past decades, the direct aerobic oxidation of substituted toluenes to their benzaldehydes and benzoic acids over various catalysts has received much attention. ,− Among the catalytic systems, the MC catalysts (combinations of Co, Mn, and Br compounds that were discovered by Mid-Century Corporation) have been successfully applied to the production of both benzoic acids and benzaldehydes in batch reactors in industry. , However, there is an explosion risk when aerobic oxidations are performed in batch reactors with MC catalysts. Meanwhile, the selective catalytic oxidation of chlorotoluenes to chlorobenzaldehydes with high selectivity remains a big challenge because of the further oxidation of chlorobenzaldehydes to acids. , Many of the safety and process challenges involved in performing gas–liquid aerobic oxidations in batch reactors can be overcome by employing continuous flow microchannel reactor technology, which provides the possibility of minimizing safety hazards while allowing the use of high-temperature and -pressure conditions to obtain an efficient oxidation process.…”

The optimization of hydrothermal synthesis of MnxCo3‐xO4/GC catalyst for low temperature NH3‐SCR /using design of experiments

“…The peaks around 3100-3400 cm −1 and 3430 cm −1 could be attributed to the OH stretching vibration on the surface of the samples. 40 The peaks at 1650, 1404, and 866 cm −1 were assigned to C C stretching vibration, COO symmetrical stretching vibration, and COH out-of-plane bending vibration, respectively. As can be seen from Fig.…”