Fluid-bed MTG process

It was earlier used for fluid-bed MTG process development and is more fully described elsewhere O). In the fluid-bed pilot-plant, uniform temperature profiles were obtained, with as little as 1 C AT over the entire 7.6 meter length. 

Two factors complicate the development of a fluid-bed MTG process. One is the need to ensure the complete conversion of methanol the other is to develop a fluid catalyst sufficiently rugged to withstand the abrasive forces inherent in fluid-bed operation. 

Thus, the fluid-bed MTG process was assessed as being a desirable but a long-term development. The scale-up would have to proceed through several stages before it would be ready for commercialization. 

Fig. 19.25. Schematic of Mobil s fluid-bed MTG process, which uses a unique zeolite catalyst to convert methanol to high octane, unleaded gasoline. (CourtesyThe Pace Company, Denver, CO.)...

MOGD and its companion process, MTO, are ready for commercial use. MOGD has been proved in a commercial test in refinery scale equipment, and the MTO process has been successfully demonstrated in the same experimental 100 barrel/day plant used to prove the fluid bed MTG process in Germany (Ref. 22). 

Avidan, A., and Edwards, M. Modeling and Scale-up of Mobil s Fluid Bed MTG Process, 5th Int. Conf. on Fluidization, Elsinore, Denmark, 18-23 May, 1986. 

Avidan A, Edwards M. Modeling and scale up of Mobil s fluid bed MTG process. In Ostergaard K, Sorensen A, eds. Fluidization V. New York Engineering Found, 1986. 

Comparison of Direct and Indirect Conversion Processes. To make direct comparison between the OCE cases and the SRM/DPOM cases, a fluid-bed MTG process must be attached to the end of the latter cases to convert CH3OH into CJ hydrocarbons. Following approximate rules of this process, derived based on commercial plant design data (Avidan et al. (1986)), were used ... 

Avidan, A.A., Edwards, M., Loeffler, W., Gierlich, H.-H., Thiagarajan, N., and Nitschke, E. (1986) The Fluid-Bed MTG Process , paper presented at the ACS State-of-the-Art Symp. on Methanol as a Raw Material for Fuels and Chemicals, June 15-18, at Marco Island, FL. 

It is likely that future commercialization of Methanol-to-Olefins (MTO) will take place in a fluid-bed reactor for many of the same reasons which encouraged fluid-bed MTG development, including better temperature control and constant product composition. The olefins produced by this process can be readily converted to gasoline, distillate and/or aviation fuels by commercially available technologies such as Mobil s MOGD process. 

Experimental work to date confirms that the MTO process, which is an extension of fluid-bed MTG technology, has been scaled up successfully in a 4 BPD fluid-bed pilot plant at Mobil s Paulsboro Laboratory. Product yields and catalyst performance were nearly identical to those of bench top microunits. The process is currently being demonstrated in the 100 BPD fluid-bed semi-works plant in Germany. The plant was started up February, 1985 after completing modifications required to enable extended operation at MTO conditions. 

Interest in this process has increased following the successful demonstration of fluid-bed MTG in the 100 B/D demonstration plant in Germany. The 100 B/D MTG project was supported by the USA Department of Energy, the German Federal Ministry for Research and Technology (BMFT), and the three industrial participants ... 

The 100 BPD MTG project was extended recently to demonstrate a related fluid bed process for selective conversion of methanol to light olefins (MTO). The products of the MTO reaction make an excellent feed to the commercially available Mobil Olefins to Gasoline and Distillate process (MOGD) which selectively converts olefins to premium transportation fuels ( 1). A schematic of the combined processes is shown in Figure 1. Total liquid fuels production is typically greater than 90 wt% of hydrocarbon in the feed. Distillate/gasoline product ratios from the plant can be adjusted over a wide range to meet seasonal demands. 

One of the most important considerations in designing a process for converting methanol to olefins was to find the best way to remove the considerable heat of reaction. Despite the fact that we are stopping the reaction at the intermediate olefin product, the reactions leading to these intermediates give off almost 90% of the heat released in the overall MTG reaction scheme (49 vs. 56 kJ/mole of methanol converted for MTO vs. MTG). Efficient removal of the heat of reaction is one of the main reasons a fluid-bed reactor was selected for scale-up demonstration. A second advantage of the fluid-bed is that product composition can be kept constant, since optimum catalyst activity can be maintained by continuous make-up and regeneration. 

Two versions of the MTG process, one using a fixed bed, the other a fluid bed, have been developed. The fixed-bed process was selected for installation in the New Zealand gas-to-gasoline (GTG) complex, situated on the North Island between the villages of Waitara and Motonui on the Tasman seacoast (60). A simplified block flow diagram of the complex is shown in Figure 6 (61). The plant processes over 3.7 x 106 m3/d(130 x 106 SCF/d) of gas from the offshore Maui field supplemented by gas from the Kapuni field, first to methanol, and thence to 2.3 x 103 m3/d (14,500 bbl/d) of gasoline. Methanol feed to the MTG section is synthesized using the ICI low pressure process (62) in two trains, each with a capacity of 2200 t/d. 

In this lecture, the development of the MTG process will be reviewed. First, the unique aspects of MTG — the catalyst, chemistry, and its special reactor design aspects — will be discussed. Next, the choices for the conversion system will be presented along with the dual-pronged strategy for development of both the fixed- and fluid bed processes. Finally, our future development plans for this general area of technology will be highlighted. 

All of the above factors must be considered in the various reactor systems for the MTG process fixed-bed reactors, fluid-bed reactors and tubular reactors. Figure 5a shows three varieties of fixed-bed reactors and Figure 5b illustrates heat-exchanger and fluid-bed reactor variants. 

A fluid bed version of the MTG process has been demonstrated successfully in an experimental 100 barrel/day plant at Wesseling, Federal Republic of Germany, and now awaits scale up to commercial application (Ref. 16). A photograph of the 100 barrel/day fluid pilot plant is shown in Figure 15. 

Isothermal temperature control in the fluid-bed reactor was easily maintained under all process conditions investigated. The temperature gradients in the catalyst bed did not exceed 5 C even at mean temperature gradients of 200 to 300 C between the catalyst bed and the heat transfer medium. The plant accumulated 17 months-on-strearn of MTG/MTO operation, including 5 months at MTO conditions. MTO operation started with sensitivity studies to determine the effects of temperature and pressure on selectivity. Deactivation periods to vary catalyst activity and to Drovide a comDarison with the 4 B/D Dilot Diant were Derformed... 

The conversion efficiency of the 100 B/D plant was better than the 4 B/D unit, which in turn was better than the bench-scale reactor. Such improvements in fluid-bed efficiency as its size increased were also observed for the MTG process. 

The conversion of methanol to aromatic hydrocarbons over ZSM-5 zeolites is the basis of the Mobil MTG (methanol-to-gasoline) process. Although the Mobil team considered a variety of configurations, including tubular heat-exchanger reactors, staged fixed-bed reactors, and fluid-bed reactors, the fixed-bed process and the fluid-bed route were selected for the initial development studies [69,70]. 

Gould, R. M., Avidan, A. A., Soto, J. L., Chang, C. D. and Socha, R. F., "Scale-up of a Fluid-bed Process for Production of Light Olefins from Methanol", paper presented at the AIChE National Mtg., New Orleans, LA, April 6-10, 1986. 

The methanol-to-gasoline route proved in New Zealand starting in 1985 (Mobil MTG process), which includes an improved MTG fluid-bed oligomerization reactor that... 

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