Vapor phase ethanol carbonylation over Rh supported on zeolite 13X

Abstract

While methanol carbonylation has been extensively studied, higher alcohol carbonylation has received relatively little attention, even though, for example, ethanol carbonylation could be a useful route for the production of propionates. Here we use Rh/Na13X to investigate the vapor phase carbonylation of ethanol with an ethyl iodide co-feed. In the base case, the catalyst is ~40% selective to propionates, with the remainder forming ethylene and diethyl ether. Deposition of additional alkali can increase selectivities to ~60%. Isotopic labeling of ethyl iodide demonstrates reversible formation of ethyl iodide from ethanol, and that preferential incorporation of ethyl iodide initiates the Rh-catalyzed carbonylation cycle. XPS and in situ X-ray absorption spectroscopy are consistent an active anionic Rh I iodide species at a zeolite exchange site. This proposed structure and the attendant catalytic reaction network are directly analogous to those of classic solution-phase Rh catalysts and other supported Rh catalysts. However, important differences are noted in the reaction orders and apparent activation barrier, which suggest that the rate of ethyl iodide formation is overall rate limiting under these conditions and for this catalyst.

Quaternary phosphonium polymer-supported dual-ionically bound [Rh(CO)I3]2– catalyst for heterogeneous ethanol carbonylation

“…Thus, higher pressure favors the formation of propionyl products and enhances the carbonylation activity. Notably, the activity of 436 h -1 achieved in the reaction over Rh-TPISP was much higher than that previously reported for corresponding homogeneous and heterogeneous systems [38,[49][50][51], accompanied by a satisfactory There is little research on the stability of catalysts for ethanol carbonylation [50,51]; thus, we studied the stability of Rh-TPISP for carbonylation, as depicted in Fig. 9.…”

“…The Rh-TPISP catalyzed heterogeneous ethanol carbonylation is hypothesized to proceed via a mechanism analogous to the reported homogeneous and heterogeneous ethanol carbonylation mechanism [50,65], except for the difference in the structure of the active Rh center, which is depicted in Scheme 2 to provide better understanding of the excellent catalytic performance of Rh-TPISP. It has been demonstrated that the mechanisms of methanol carbonylation and ethanol carbonylation are similar.…”

“…For a deep study of the catalyst structure, Rh L3-edge XANES, XPS, EXAFS, and other analyses were used to characterize [Rh(CO)I3] 2-as the structure of the Rh active center for the carbonylation reaction; this anion is thought to Scheme 2. Proposed mechanism for heterogeneous ethanol carbonylation on Rh-TPISP according to typical homogeneous ethanol carbonylation [50] and heterogeneous ethanol carbonylation [65].…”

“…Homogeneous ethanol carbonylation is a single-step selective process for generating PA [38][39][40][41], but the homogeneous catalysis of ethanol carbonylation is much less effective than that of methanol carbonylation [42][43][44][45][46][47][48], and the development of heterogeneous ethanol carbonylation processes remains challenging because of the low stability of the catalysts. Nefedov et al [49] and Notesteina et al [50,51] reported valuable studies on heterogeneous ethanol carbonylation. The Rh species were supported on a zeolite, with a highest TOF of approximately 70 h -1 at 1 atm and 473 K, and the Rh species were supported on Cs heteropolyacid with a maximal propionate selectivity of 96% under 1 atm at 473 K with the addition of water.…”

Kinetic study of carbonylation of ethanol using homogeneous Rh complex catalyst

“…A number of catalysts can used for ethanol carbonylation, such as Rh, Ru, Co, Pd and Ir compounds. [ 7–13 ] However, except Rh, these catalysts require extremely high pressures (~40 MPa) and suffer from poor yields. Therefore, the carbonylation of ethanol with rhodium complex as catalyst can be carried out under more mild conditions and has higher activity and selectivity due to its high activity.…”