Silica adsorbent design and process evaluation for recovery of homogeneous catalysts by reverse flow adsorption

Abstract

in Wiley InterScience (www.interscience.wiley.com).The goal of this work is to demonstrate the stability of reverse flow adsorption process for recovery of homogeneous catalysts and to study the influence of catalyst and adsorbent properties for optimizing the RFA process operation. Data used in simulations were obtained from our previous work. Two models are developed to describe the reversible adsorption. One which describes the adsorption of the metal containing species and second model that describes adsorption of the free ligand. It is shown that stable operation is reached, where leaching of metal is prevented. The RFA process can be applied for wide ranges of the catalyst's stability constants [10 0 -10 12 (dm 3 / mol) 2 ] and it is specially applicable for the recovery of homogeneous catalysts that have a low metal concentration. Values of the adsorbent (b M ¼ 0.8, a ¼ 1850, Pe P ¼ 376.4, d p ¼ 100 lm and e b ¼ 0.5) and the column characteristics (Bo ¼ 1.74 3 10 4 and N ¼ 6.6 3 10 4 ) that provide a sharp concentration profile inside the bed are determined. Simulation of the recovery of Rh catalyst in the BASF hydroformylation process required a total adsorption bed volume of 6% of reactor volume.

Reverse‐Flow Adsorption for Process‐Integrated Recycling of Homogeneous Transition‐Metal Catalysts

“…Recently, a model for the determination of the binding strength ( K ads ) for a reversible host–guest adsorption process was developed 7. Modeling of reactor conditions showed that a binding constant, or adsorption constant, around 1×10 3 M −1 of the catalyst to the support is ideal for the RFA concept.…”

“…We anticipated that an ideal value of the adsorption constant for the binding of homogeneous catalysts on adsorption beds in RFA reactors should be in the range of 10 3 M −1 . This range of adsorption constants gives the sharpest concentration profile in the adsorption bed for RFA in which a continuous adsorption/desorption process is applied 7. We carried out an experiment to evaluate the effect of multiple adsorption/desorption for the current system, which has an adsorption constant four times higher than ideal.…”

“…The system under investigation, which involves specific adsorption beds (loading of 0.19 mmol g −1 and K ads of 3.9×10 3 M −1 ) with a volume of 12.5 % of that of the reactor, does not represent the ideal system,7 which instead has adsorption beds (loading of 1.0 mmol g −1 and K ads of 0.8×10 3 M −1 ) that are only 3 % of the reactor volume. However, the results obtained so far are in line with those previously shown by modeling studies 7…”