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Methanol Conversions
Published in Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda, 1 Chemistry, 2022
Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda
The production of acetic acid by iridium catalytic system was commercialized as Cativa process by BP Amaco in 1996 (Sunley and Watson, 2000). Although to achieve similar activity level as Rh, more Ir is required, the catalyst is capable of operating at reduced levels of water (lower than 8 wt% for Cativa compared to 14–15 wt% for traditional Monsanto). Therefore, byproduct formation is reduced, carbon monoxide-based yield improves and steam consumption decreases. One of the main advantages of Ir-based processes is high stability of catalytic species of iridium. Tolerating low water concentrations (0.5 wt%) of the catalyst is especially important and is ideal for optimizing methanol carbonylation process. It has been found that iridium catalyst is active in wide range of conditions in which the rhodium counterparts are decomposed to completely inactive and to large extent nonregenerable salts. In addition to higher stability, iridium catalysts are much more soluble than rhodium catalysts; therefore, higher solution concentrations are achieved which provide much higher reaction rates available.
Homogeneous Methane Functionalization
Published in Jianli Hu, Dushyant Shekhawat, Direct Natural Gas Conversion to Value-Added Chemicals, 2020
Anjaneyulu Koppaka, Niles Jensen Gunsalus, Roy A. Periana
The Monsanto process, based on a rhodium catalyst, is used for the conversion of methanol to acetic acid (more recently it has been largely replaced by the greener and more efficient Cativa process, developed by BP Chemicals Ltd, which is a process similar to the Monsanto process but uses an iridium-based catalyst) by carbonylation of methanol (Jones 2000; Sunley and Watson 2000). The required use of methanol in this process is less than ideal because the methanol is produced through the energy intensive, syngas process. The capability to directly convert methane to acetic acid using CO, and O2 is an economically desirable process. Although the thermodynamics are not favorable for the functionalization of methane to acetaldehyde by reaction with CO (ΔG = +14 kcal/mol), the reaction of methane with CO and O2 to generate acetic acid is thermodynamically favorable (Chepaikin et al. 1998).
Chemicals from Olefin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
The Reppe reaction involves the addition of carbon monoxide and an acidic hydrogen donor to the organic substrate. Commercial processes using this type of chemistry include the Monsanto process and the Cativa process which converts methanol to acetic acid—acetic anhydride is prepared by a related carbonylation of methyl acetate (CH3COOCH3). In the related hydrocarboxylation and hydroesterification reaction, alkene derivatives (>C=C<) and alkyne derivatives (–C≡C–) are the substrates. This method is used in industry to produce propionic acid from ethylene: RCH=CH2+H2O+CO→RCH2CH2CO2H
Understanding oxidative addition in organometallics: a closer look
Published in Journal of Coordination Chemistry, 2022
Nabakrushna Behera, Sipun Sethi
This Cativa process delivers many benefits over the conventional Monsanto methanol carbonylation process. These benefits include lower cost of iridium, better overall reaction rate, good turnover number (TON) of the catalyst, high solubility of the iridium complex in the reaction mixture, small water content (can be reduced up to 0.5%) (which otherwise becomes difficult in the Monsanto process due to the precipitation of catalytic intermediate RhI3, thereby reducing the yield, and on the other hand, it requires high input of energy for separating acetic acid from water if more water is used), formation of less by-products, etc. [5, 23].
Rhodium(I) carbonyl complexes containing amino acid ester ligands: synthesis, reactivity and DFT studies
Published in Journal of Coordination Chemistry, 2022
Bhaskar Jyoti Sarmah, Jayashree Nath, Ankur Kanti Guha
Platinum complexes of different types of donor atoms have been the area of prior interest because of their diverse catalytic activities which has become a major synthetic tool in industrial processes [1–4]. The activation of small molecules such as CO, CH3I, H2O2, etc. by metal complexes [5] is important and interesting due to their catalytic reactions; for instance, oxidative addition of CH3I is an important step in the rhodium-catalyzed Monsanto [6] and iridium-based Cativa [7] process for acetic acid production. The development of new N-donor ligands with two different coordinative heteroatoms may be an attractive alternative to diphosphines [8, 9]. The bifunctional character of hybrid ligands has proven to be very useful in homogeneous catalysis and some important organic reactions catalyzed by transition metal complexes with N∩X ligands (X = O, P, S, N, etc.) are quite impressive in terms of selectivity and reactivity [10]. Thus, a transition metal complex with a bidentate ligand in which the two coordinating atoms are electronically different can impart stereoelectronic control in the formation of a specific product, resulting in enhanced selectivity [11]. Sharma et al. [12] reported the preparation of rhodium carbonyl complexes of the type [Rh(CO)2ClL] with aminobenzoic and substituted aminobenzoic acid, where L is aminobenzoic acid or substituted aminobenzoic acid. The ligands are found to act monodentately as N-donors and the carbonyl COO- remains uncoordinated in all the complexes. D.J. Cole-Hamilton and C.R. Saha reported complexes of the type [Rh(AA)(PPh3)3] and [Rh(PAA)(PPh3)2] (AAH = 2-aminobenzoic acid, PAAH = N-phenylanthranilic acid) [13, 14] which show catalytic activity for reductive carbonylation of nitroaromatics as well as in hydrogenation reactions of unsaturated compounds.