Catalytic reactors methanol production

In a fixed-bed catalytic reactor for a fluid-solid reaction, the solid catalyst is present as a bed of relatively small individual particles, randomly oriented and fixed in position. The fluid moves by convective flow through the spaces between the particles. There may also be diffusive flow or transport within the particles, as described in Chapter 8. The relevant kinetics of such reactions are treated in Section 8.5. The fluid may be either a gas or liquid, but we concentrate primarily on catalyzed gas-phase reactions, more common in this situation. We also focus on steady-state operation, thus ignoring any implications of catalyst deactivation with time (Section 8.6). The importance of fixed-bed catalytic reactors can be appreciated from their use in the manufacture of such large-tonnage products as sulfuric acid, ammonia, and methanol (see Figures 1.4,11.5, and 11.6, respectively). 

It is of interest to assess the process potential of methanol production by a direct partial oxidation of methane. This way the steam reformer and the shift reactor can be saved, and the catalytic methanol reactor can be replaced by a noncatalytic partial oxidation reactor. It is estimated that direct partial oxidation is competitive if a conversion of methane of at least 5.5% can be obtained with a methanol selectivity of at least 80%. 

Using the pulse flow catalytic reactor mentioned earlier, we were able to create a pentamethylbenzenium (Figure 1) in zeolite HZSM-5 (16). The cation was synthesized in the channel intersections or pore mouths by alkylating benzene or toluene with methanol at 523 K. This cation cannot be prepared in detectable concentration when the reaction is carried out in a sealed rotor, as is commonly done in in situ NMR studies. In contrast, when alkylation is carried out in a flow reactor, the co-product—water—is removed, and the cation accumulates as a significant product in the zeolite. 

Preheated natural gas is fed at about 600°C to the reformer and exits at about 880°C and 2.1 MPa. Methanol synthesis is then performed over copper-based catalysts at about 240-270°C and 10.3 MPa. The product gas contains about 5% methanol. By-products are 1-2% dimethyl ether and 0.3-0.5% higher alcohols. Because of equilibrium limitations, conversion of synthesis gas is only a few percent per pass in the catalytic reactor, and the product gas stream after... 

The ultimate goal in methanol production will be achieved if satisfactory catalysts and reactor technologies can be developed for efficient direct catalytic oxidation of methane or natural gas. 

The concept of zeolite membrane encapsulated catalyst (ZMEC) is an original way to use zeolite membranes in catalytic reactors [158,159]. The concept of coating catalyst particles with a selective zeolite layer can reveal useful for either increasing reactant selectivity (e.g. selective hydrogenation of linear molecules) or product selectivity (e.g. animation of methanol). It also protects the catalyst from poisoning. 

Finally, integrating chemical reaction and separation in a single vessel offers opportunities for waste reduction. As an example of this strategy, consider the synthesis of methyl-tert-butyl ether (MTBE). Two processes are in common industrial use in the synthesis of MTBE from methanol and isobutylene. In one process, a series of fixed-bed catalytic reactors send a mix of product, unreacted methanol, and unreacted isobutylene to a series of separation devices. In an alternative process configuration, the feed materials are sent to a distillation column that contains a series of catalytic beds. The processes are contrasted in Fig. 17. There are several advantages to the catalytic distillation configuration ... 

In the conventional method for the generation of methanol from synthesis gas, a mixture of CO, CO2, and H2 is compressed and introduced into a fixed-bed catalytic reactor. The reactions are exothermal and volume-reducing, thus low temperatures and high overpressures are desirable. A catalyst is required to maximize methanol output. Methanol production generates a surplus of hydrogen which can, by adding CO2, be utilized to increase the methanol yield. Methanol is basically used in the chemical industry as... 

METHANOL PRODUCTION IN PACKED CATALYTIC TUBULAR REACTORS 573... 

When processing wood pyrolysis liquids, the two pyrolysis product liquid layers were homogenized (EHI of the blend was 0.32) by high speed mixing and fed immediately to the fluid bed catalytic reactor. When co-processed with methanol, the two pyrolysis liquid layers were dissolved in the methanol to provide a mixture having an apparent EHI of 1.2-1.3. 

The conventional processes for the manufacture of MTBE uses a catalytic reactor with a slight excess of methanol (methanol/isobutylene = 1.05 to 2). The products correspond to the near-equilibrium conversion of 90-95 %. The reaction mixture is separated using distillation, but this is complicated by the formation of the binary azeotropes methanol-MTBE and isobutylene-methanol. The unreacted isobutylene is difficult to separate from other volatile C4 products. In the RD process. 

Catillon, S, Louis, C, Topin, F, Vicente, J, Rouget R. Improvement of methanol steam reformer for FI2 production by addition of copper foam in both the evaporator and the catalytic reactors. Chem. Eng. Trans. 2004 4 111-116. 

The conversion of methanol and ammonia to methylamines is achieved over dehydration catalysts operated in the temperature range 300450°C and 0.12 MPa pressure. The reactions are exothermic, and excess ammonia is used to control the product distribution. The dehydration catalysts are generally promoted Si-Al composites. The promoters include molybdenum sulfide and silver phosphate [68]. In the commercial Leonard process, a gas-phase downflow catalytic reactor operating at about 350°C and 0.62 MPa is used [69]. Recovery of the desired product is achieved throu a series of four distillation and extractive distillation columns. Unwanted product is recycled, suppressing further formation of the undesired component in the reactor. A very small amount of methanol is lost to CO and H2, and yields from the commercial process based on methanol and anunonia are >97% [70]. 

Problem 1-5 (Level 2) Carbon monoxide (CO) and hydrogen (H2) are fed to a continuous catalytic reactor < erating at steady state. There are no other components in the feed. The outlet stream contains unconverted CO and H2, along witii the products methanol (CH3OH), etiianol (C2HSOH), isopropanol (C3H7OH), and carbon dioxide (CO2). These are the only species in the product stream. 

Catalytic gas-phase reactions play an important role in many bulk chemical processes, such as in the production of methanol, ammonia, sulfuric acid, and nitric acid. In most processes, the effective area of the catalyst is critically important. Since these reactions take place at surfaces through processes of adsorption and desorption, any alteration of surface area naturally causes a change in the rate of reaction. Industrial catalysts are usually supported on porous materials, since this results in a much larger active area per unit of reactor volume. 

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