Reactors Parr hydrogenator

Apparatus for carrying out hydrogenation at several atmospheres can be constructed readily (1,78,93), but there seems little point in this exercise since good commercial equipment is available. The most commonly used commercial low-pressure equipment is the Parr hydrogenator (manufactured by Parr Instrument Co., Moline, Illinois). This equipment (Fig. 1) has withstood the test of time it was first described in 1922 and offered commercially in 1926. It comes in two sizes one for 500-ml reactor bottles and one for 1000-and 2000-ml reactor bottles. Specially made smaller bottles, down to 50 ml, can be used also but require special holders to compensate for differences in bottle heights. Shaker bottles should not be more than half full to ensure good mixing, a consideration in selection of bottle size. 

Aqueous lactose (40 wt-% in water) and xylose (50 wt-%) solutions were hydrogenated batchwise in a three-phase laboratory reactor (Parr Co.). Reactions with lactose were carried out at 120 °C and 5.0 MPa H2. Xylose hydrogenations were performed at 110 °C and 5.0 MPa. The stirring rate was 1800 rpm in all of the experiments to operate at the kinetically controlled regime. 

Reactions were carried out in liquid phase in a well-stirred (1000 rpm) high-pressure reactor (Parr Instruments, 300 mL) at 30 bar and 150°C. The reaction mixture consisted of 61 g of ADPA (Acros Chemicals), 53 g MIBK (Acros Chemicals) and 370 mg of catalyst. The test procedures used here is similar to that described earlier by Bartels et al. (7). The reactor was operated at a constant pressure with the liquid phase in batch mode and the hydrogen fed in at a rate proportional to its consumption. The reaction was monitored by hydrogen uptake and the product yield was determined from gas chromatographic (Agilent Technologies, 6890N) analysis. 

The most common low pressure reactor is the Parr hydrogenator shown in Fig. 6.5. This system is composed of a reaction bottle that is coimected to a gas reservoir that has a capacity of about four liters. Two versions of the apparatus are commercially available a standard model that takes 250 mL and 500 mL reaction bottles and that can be used to pressures up to about 60 psig and a larger size that uses 1 liter and 2 liter bottles that have about a 40 psig pressure limit. The bottles are coimected to the gas reservoir by a tube inserted through a rubber stopper in the mouth of the bottle. The common black rubber stoppers may contain catalyst poisons that can be extracted into the reaction mixture by some solvents. The use of neoprene stoppers will minimize this problem. 

Fig. 6.6. Threaded reactor bottles for the Parr Hydrogenator. a) Small scale bottle with threaded Nylon spacer b) bottle for standard reactor and c) bottle for large scale reactor, each with threaded Teflon adapters. (Courtesy Ace Glass, Inc.)...

Phenyl-1,2-propanedione (Aldrich, 99%) was hydrogenated in a pressurized reactor (Parr 4560, V=300 cm ) in the absence of external and internal mass transfer limitation (verified experimentally). The reactor was equipped with an propeller type stirrer (four blades, propeller diameter 35 mm) operating at stirring rate of 1950 rpm. The hydrogen (AGA, 99.999%) pressure was 6.5 bar and teii ierature was 15 - 35°C. Pt/Al203 (Strem Chemicals, 78-1660) was used as a catalyst. The catalyst mass and liquid volume were 0.15 g and 150 cm, respectively The metal content was 5 wt.%, BET specific surface area 95 m / g, the mean metal particle size 8.3 nm (XRD), dispersion 40% (H2 chemisorption), the mean catalyst particle size 18.2 pm (Malvern). Catalysts were activated under hydrogen flow (100 cm / min) for 2 h at 400°C prior to the reaction. 

The hydrogenation reactor consisted of a 1-L Hastelloy C autoclave (Model 464IM, Parr instmment company, Moline Illinois) equipped with a belt-driven, magnetic stirrer (1000 rpm). 

Hydrogenations. Hydrogenation was accomplished using a Series A000 Parr High Pressure Reactor. The polymers were end-capped before... 

Figure 3 Product distribution as a function of time for debenzylation of SM(S) on Delink io%Pd/CPS4. Parr Reactor, 25 °C, 45 psig hydrogen.

Table 2. Hydrogenation of Schiff s base B, 38 °C, 30 psig, 700 rpm in a Parr reactor...

Catalytic Experiments. Activities were performed in a 1 liter Parr reactor. A typical experiment was performed as follows at a temperature of 100 °C, 100 mg of the catalyst and 1.5 /. wt of (-)-carvone (Aldrich) in n-hexane solution (100 ml) were Introduced in a high pressure Parr reactor equipped with mechanical stirring and automatic temperature control. Before introducing the hydrogen the system was purged 2 or 3 times with Nz> The total hydrogen pressure was 21 atm. The reaction products were analysed by gas chromatography. NMR and Mass Spectrometry and identified as unreacted carvone, carvotanacetone, carvomenthone and three carvomenthol stereoisomers (axial-equatorial, equatorial-equatorial and equatorial-axial). 

Pd occluded in SAPO-11 Acetone MIBK (Acid or base) + dehydration + hydrogenation 31 84 50 ml acetone 37 bar 473 K 4h H2/acetone = 1 Parr reactor no solvent [9]... 

A Parr reactor was charged with the Step 4 product (118.8 g) and 1200 ml THF, then heated until dissolution, and then treated with 10% palladium on carbon (0.47 g). The mixture was shaken under 50psi hydrogen 24 hours at ambient temperature, then filtered through celite, and concentrated. The residue was triturated with 1100 ml MTBE, refiltered, washed with 110 ml MTBE, dried, and the product isolated. 

Special reactor bottles having working volumes of 1 mL to 1000 mL are also available. As depicted in Fig. 6.6, these bottles have threaded Teflon adapters to hold the hydrogen inlet tube so catalyst contamination by the reactor is virtually eliminated. The smaller bottles, which have working volumes between 1 mL and 20 mL, use a spacer to secure them into the shaker assembly (Fig. 6.6a). Those with capacities of 20 mL to 200 mL (Fig. 6.6b) fit directly into the shaker assembly of the smaller Parr apparatus while 500 mL and 1000 mL vessels of this type (Fig. 6.6c) are available for the larger unit. 

Hydrogenation experiments with simultaneous acoustic irradiation were carried out by using iso-propanol (2-propanol) as solvent in an automatic laboratory-scale autoclave (Parr 4560) with an effective liquid volume of 250 ml. The operating conditions were as follows 50 bar hydrogen pressure and 70°C (343 K) as the reaction temperature. The catalyst-to-citral ratio was 1 25 (wt wt) in the beginning of the reaction. A commercial molybdenum promoted Raney nickel catalyst with a mean particle size of approx. 22 pm and the specific surface area in the range of 80 m /g was used in the experiments. The reactor contents were analyzed oiF-line with gas chromatography (GC). 

Screening reactions were carried out with 10-15 wt% solutions of PVOH in a 100 mL stirred stainless steel Parr autoclave. Catalyst (5% Pd/AlaOs 5 wt%, based on PVOH) was added, the reactor was purged and pressiue checked with nitrogen, purged and pressurized with hydrogen, and heated with stirring to the desired tenqterature for the desired time (see Table 1) at the desired pressure (typi-... 

Standard reaction conditions. Reactions were carried out in a Parr high pressure steel reactor. A solution in methanol (10 ml) of reactant (100 mg) and modifier (15 mg) was added to the catalyst in the reactor, which was then closed, purged twice with 3 bar helium and twice with 3 bar hydrogen, and pressurised with hydrogen to 10 bar. Reactions occurred at ambient temperature (293 - 295 K) and the mixture was stirred at 1000 rpm. Because of the small quantities of reactant used (0.46 mmol for (I)) hydrogen uptake, and hence conversion, could not be measured accurately. Consequently, reactions were allowed to proceed for 3 h within which time 100% conversion was normally achieved. 

The evaluation of catalytic hydrogenation was carried out in batch reactor of 450 mL and under pressure (Parr autoclave). To eliminate the diffusion effects, the reactor was equipped with double-helix stirring device at specific positions near the bottom and on the surface of the reactant (height of the liquid mixture). To visualization of the system. Figure 25.11 presents the reactor used for this example. 

Hydrogenation of the aromatic acids was accomplished in a 600 ml capacity Parr Company mini-reactor (type 4563). Catalyst action was provided by a commercial (Alfa Inorganics) Raney nickel... 

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