Cartridge catalyst

Several limitations hamper the development of efficient systems for cartridge catalysts based on the more conventional regulated systems (1) Thermal and/ or chemical stress can lead to deactivation of the organometallic catalyst (2) Additives used to induce precipitation may accumulate in the catalyst... 

Scheme 3.15 Hydroformylation as a benchmark reaction to validate the cartridge catalyst system MeOPEG750-PPh2/[Rh(acac)(CO)2]/scCO2 (Reproduced from Ref. [76], with the permission of John Wiley and Sons)...

Basically, tliere are two classes of anunonia converters, tubular and multiple bed. The tubular bed reactor is limited in capacity to a maximum of about 500 tons/day. In most reactor designs, the cold inlet synthesis gas flows tlirough an annular space between the converter shell and tlie catalyst cartridge. This maintains the shell at a low temperature, minimizing the possibility of hydrogen embrittlement, which can occur at normal synthesis pressures. The inlet gas is then preheated to syntliesis temperature by the exit gas in an internal heat e.xchaiiger, after which it enters tlie interior of the anunonia converter, which contains tlie promoted iron catalyst. 

Fabrication was done by photolithography and deep reactive ion etching (DRIB). The catalyst was inserted by sputtering. Such a prepared microstructure was sealed with a Pyrex cover. The bonded micro device was placed on a heating block containing four cartridge heaters. Five thermocouples monitored temperature on the back side. A stainless-steel clamp compressed the device with graphite sheets. 

The heat of adsorption of 2-nitropropane is very high, so carbon-containing respirators should not be used in high vapour concentrations. Also, if Hopcalite catalyst (co-precipitated copper(II) oxide and manganese (IV) oxide) is present in the respirator cartridge, ignition may occur. 

Metal-catalyzed cross-couplings are key transformations for carbon-carbon bond formation. The applicability of continuous-flow systems to this important reaction type has been shown by a Heck reaction carried out in a stainless steel microreactor system (Snyder et al. 2005). A solution of phenyliodide 5 and ethyl acrylate 6 was passed through a solid-phase cartridge reactor loaded with 10% palladium on charcoal (Scheme 2). The process was conducted with a residence time of 30 min at 130°C, giving the desired ethyl cinnamate 7 in 95% isolated yield. The batch process resulted in 100% conversion after 30 min at 140°C using a preconditioned catalyst. 

Most recently, a catalyst system based on PEG-modified phosphine ligands was reported to allow for a highly effective C02-induced separation procedure. In this case, the scC02 was used only at the separation stage to precipitate the catalyst and extract the products. The hydrogenation of styrene to ethyl benzene was used as a benchmark reaction, and it was shown that the catalytic active species could be recovered and not only re-used for another hydrogenation but also be subjected as a cartridge to a series of different transformations [43]. 

Household waste, 25 864 House-of-cards glass-ceramic microstructure, 12 635 Housewares, LLDPE, 20 207-203 Housewrap, 17 482 Housings, for cartridge filters, 11 369 Hoveya-Grubbs catalysts, 26 934 H-phosphonate DNA synthesis method, 17 624-625... 

An oxidation catalyst containing cobalt, copper, manganese and silver species. It adsorbs nitroalkanes strongly, which may then ignite. Respirator cartridges containing it should not be used in high concentrations of nitroalkanes. 

Consequently a cartridge system for the hydroformylation of a variety of different alkenes using a single batch of catalyst was developed to fully exploit the potential of this approach (Scheme 1). Four different alkenes were applied in total using the same batch of catalyst for nine consecutive catalytic cycles. Conversion was driven to completeness in all cases, with selectivities remaining unchanged. Only 1.2% of rhodium and 2.4% of phosphorus was lost in nine cycles. Representative results are shown in Table 1. 

Fig. 1 Organometallic cartridge catalysis. A selection from a variety of transition metal complex catalysed conversions of substrates S,- with different reagents to the desired product Pix is possible using a single catalyst batch with the same apparatus and separation techniques...

The Csajagi research group used a commercial X-Cube continuous flow reactor system [32] to perform similar reactions. The reactor is made of stainless steel, capable of reaching pressures of up to 150 bar, and equipped with preloaded catalyst cartridges. Monoamides of aryldicarboxylic acids are obtained in a reaction over a tetrakis(triphenylphosphine)palladium catalyst using A-methylpyrrolidone as base [33]. Terephtalic acid was reported as the byproduct, but not the oc-ketoamide. 

After the optimization of these conditions, by adding an azide to the input stream it was possible to synthesize a range of substituted triazoles in a heterogeneously catalysed three-component reaction (Scheme 18). After the CFC, the stream was passed through a column containing a resin-immobilized copper-based catalyst, which was used in a previous work by the same authors to successfully catalyze the formation of triazoles from alkynes and azides [44]. An immobilized thiourea-containing cartridge was subsequently used to remove any leached Cu catalyst. In a similar way as for the alkynes production, the series of resins was used to purify the product. 

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