Quench cooling methanol synthesis

Figure 11.6 Examples of methanol synthesis converters (a) tube-cooled, low-pressure reactor A nozzles for charging and inspecting catalyst B outer wall of reactor as a pressure vessel C thin-walled cooling tubes D port for catalyst discharge by gravity (b) quench-cooled, low-pressure reactor, A,B,D, as in (a) C ICI lozenge quench distributors (Twigg, 1996, pp. 450, 449 reproduced with permission from Catalyst Handbook, ed. M.V. Twigg, Manson Publishing Company, London, 1996.)...

The de novo discovery synthesis of capecitabine (1) was reported by the Nippon Roche Research Center scientists9,19 and was followed up with a preparation invented by a team at the Hoffinann-La Roche laboratories in New Jersey for the conversion to 1 from 5 -DFCR (10).2° In the first route, 5-fluorocytosine (15) was mono-silated using one equivalent of hexamethyldisilazane in toluene at 100 °C followed by stannic chloride-catalyzed glycosidation with known 5-deoxy-l,2,3-tri-0-acetyl-p-D-ribofuranoside (17) in ice-cooled methylene chloride. While this procedure provided the 2, 3 -di-0-acetyl 5-fluorocytidine 18 in 76% yield on a 25-g scale, an alternative method was also devised using in situ-generated trimethylsilyl iodide in acetonitrile at 0°C to provide a 49% yield of 18 on smaller scale. Acylation of the N -amino group of the bis-protected 5 -DFCR derivative was accomplished by the slow addition of two equivalents of -pentyl chloroformate to a solution of 18 in a mixture of pyridine and methylene chloride at -20 °C, followed by a quench with methanol at room temperature to provide the penultimate intermediate 19 on 800-g scale. The yield of intermediate 19 was assumed to be quantitative and was subjected to the final deprotection step, with only a trituration to... 

In this paper the various routes to methanol synthesis are summarized and compared with a new catalytic partial oxidation route. Also compared are quench, steam raising and tube cooled converters, along with comparative energy and economic stannaries of the various routes. 

Fig.3.3a-d. Various types of methanol synthesis reactors, (a) Cold gas quench (b) cooling by evaporation - multistage, adiabatic (c) cooling by evaporation - tubular, near isothermal (d) liquid entrained system using heat carrier liquid... 

Fig. 6A, B and C show operating lines for the three types of reactors in methanol synthesis (confer Table 4, case 2). The situation is the same here. The internally cooled reactor gives the best approach to the optimum operating line and may as a consequence be designed for the smallest catalyst volume, whereas the quench cooled reactor requires the largest volume. It is not, however, possible to base a choice between the reactor types solely on the required catalyst volume. As indicated in Table 1, a number of other considerations must be taken into account.

In Haldor Tops0e s ammonia and methanol synthesis processes a series of adiabatic beds with indirect cooling between the beds is normally used, at least in large plants. In smaller plants internally cooled reactors are considered. In ammonia synthesis, the Tops0e solution is today the so-called S-200 converter (Fig. 7) and L6j. This converter type, which is a further development of the S-100 quench-type converter, was developed in the mid seventies the first industrial unit was started up in 1978, and today about 20 are in operation or on order. Both the S-100 and the S-200 reactors are radial flow reactors. The radial flow principle offers some very specific advantages compared to the more normal axial flow. It does, however, also require special catalyst properties. The advantages of the radial flow principle and the special requirements to the catalyst are summarized in Table 5. 

Quench Converter. The quench converter (Fig. 7a) was the basis for the initial ICl low pressure methanol flow sheet. A portion of the mixed synthesis and recycle gas bypasses the loop interchanger, which provides the quench fractions for the iatermediate catalyst beds. The remaining feed gas is heated to the inlet temperature of the first bed. Because the beds are adiabatic, the feed gas temperature increases as the exothermic synthesis reactions proceed. The injection of quench gas between the beds serves to cool the reacting mixture and add more reactants prior to entering the next catalyst bed. Quench converters typically contain three to six catalyst beds with a gas distributor in between each bed for injecting the quench gas. A variety of gas mixing and distribution devices are employed which characterize the proprietary converter designs. 

The total synthesis of several amaryllidaceae alkaloids including that of narciclasine was accomplished in the laboratory of T. Hudlicky. The C2 stereochemistry was established by a two-step sequence Luche reduction of the a,(3-unsaturated cyclic ketone followed by a Mitsunobu reaction. The ketone was first mixed with over one equivalent of CeCIs in methanol and then the resulting solution was cooled to 0 °C, and the sodium borohydride was added. In 30 minutes the reaction was done, and the excess NaBH4 was quenched with AcOH. The delivery of the hydride occurred from the less hindered face of the ketone and the allylic alcohol was obtained as a single diastereomer. 

After hot-cyclone recycle of char to the gasifier, generation of medium-pressure steam in a horizontal fire-tube boiler cools the hot (about 1,800°F) raw coal gas. The gas is then water quenched and CO shifted. The gas is compressed to about 500 psig pressure before undergoing purification in the chilled methanol physical solvent Rectisol process. The purified synthesis gas moves via pipeline to nearby Wesseling, where one or Union Kraftstaffs plants converts it into 350 t/d of methanol. 

Synthesis of 38 To a 4-L toluene solution was added ketone 34 (400 g, 1.24 mol, 1.0 equiv), (5)-a-phenylethylamine (181 g, 1.49mol, 1.2 equiv), and Ti(0 Pr)4 (91.6g, 0.322mol, 0.26 equiv). The reaction mixture was refluxed under azeotropic distillation to achieve 99.1% conversion after 23 hours. The reaction mixture was cooled and inverse quenched to a 2-N NaOH solution. After filtration and phase split, the toluene solution was concentrated to 2L. To the above toluene concentrate was added 2L of methanol and 5% Pd-Cu/C dry catalyst with Pd-Cu (wt/wt) ratio of 4 1 from Johnson Matthey (A701023-4) (25 g, 6.25 wt/wt% based on... 

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