Methanol-to-olefins process

Marcus, D.M., McLachlan, K.A., Wildman, M.A., Ehresmann, P.W., and Haw, ).F. (2006) Experimental evidence from H/D exchange smdies for the failure of direct C-C coupling mechanisms in the methanol-to-olefin process catalyzed by HSAPO-34. Angew. Chem. Int. Ed., 45, 3133-3136. 

Lewis, J.M.O. (1988) Methanol to olefins process using silicoalumino-phosphate molecular sieve catalysts, in Catalysis 1987 (ed. J.W. Ward), Elsevier, Amsterdam, p. 199. 

The methanol transformations discussed precedingly can be modified to produce high amounts of light alkenes.437 454 474 475 The key to achieve this change is to prevent C2-C4 olefinic intermediates to participate in further transformations. Such decoupling of alkene formation and aromatization can be done by the use of small-pore zeolites or zeolites with reduced acidity. Reduced contact time and increased operating temperature, and dilution of methanol with water to decrease methanol partial pressure, are also necessary to achieve high alkene selectivities. This approach has led to the development of the MTO (methanol-to-olefin) process, which yields C2-C5 alkenes with about 80% selectivity. 

This is an important industrial reaction, alone or in combination with others. The CH3OH production is often coupled to oxidation to formaldehyde, methanol to gasoline (Mobil) process, methanol to olefins process, carbonylation, etc. Due to this, a large volume of information already exists on catalyst preparation, kinetics, reactors and all other aspects of the related chemical technology [53]. However, let us concentrate our attention here on just one selected problem the role of the promoter and the nature of the active site on the metal on oxides catalysts. Let us mention in passing that pure metals (promoter free) most likely do not catalyze the synthesis. 

Application To produce ethylene, propylene and butenes from natural gas or equivalent, via methanol, using the UOP/Hydro MTO (methanol to olefins) process. 

Using a similar approach, Masuda et al. [219] employed a ZSM-5 zeolite membrane in a flow-through configuration for the methanol-to-olefins process. As in the previous work, permeating molecules would ideally have a uniform residence time... 

In our laboratory, we have studied the coupling of two methanol molecules at the acid site of chabazite (see Fig. 1) (Giurumescu and Trout, 2001). This is hypothesized to be an important elementary step in the formation of the first carbon-carbon bond in methanol-to-olefins processes. Because this step has a significant activation barrier, we have chosen to use the method of constraints, with the constraint being the carbon-carbon distance. Simulations were performed at 673 K for 1.5 ps at each point. Our free energy profile is shown in Fig. 15. 

An additional specific dehydration, the transformation of methanol to gasoline-range hydrocarbons (MTG process [15,16]) has been running on a commercial scale for a short time. A partial conversion, the methanol-to-olefin process (MTO process [15,16]), might become more important as selective means of obtaining lower olefins. 

Methanol to Olefins Process (MTO) Process. Methanol can be converted to olefins by using modified pentasil catalysts. This interesting process, which is not yet used on an industrial scale, will presumably be of practical importance some... 

Lower olefins are today produced by steam cracking of naphtha, LSR or other paraffinic feeds. Hie actual methanol price does not allow the methanol to olefins process to compete economically. However, if methanol will become more available firom natural gas transforming routes, then there is a great chance for that process to become commercial. 

Recent advances have shown zeolites are effective in catalysing the direct conversion of synthesis gas to motor fuels. The MTO (methanol-to-olefins) process converts MeOH to C2-C4 alkenes and is also catalysed by ZSM-5. The development of a gallium-modified ZSM-5 catalyst (Ga-ZSM-5) has provided an efficient catalyst for the production of aromatic compounds from mixtures of C3 and C4 alkanes (commonly labelled LPG). 

The supply of methanol to the area is expected to grow in the future. This will attract new large-scale installations that process methanol to convert it into derivatives, such as olefins, through the Methanol to Olefins process (MTO) and it will cause expansion of the production of formaldehyde. At its turn, formaldehyde can be used in the production of fiber board, a key ingredient for the furniture industry. In addition to the import of biomass for gasification purposes, imported wood chips can be used in the production of fiber board. 

Methanol has been utilized as a practical Cl source in bulk-scale methanol-to-gasoline and methanol-to-olefin processes [120-123], as well as processes for the production of acetic acid, such as the Monsanto and Cativa processes [124—128]. 

Alwahabi SM, Froment GF Single event kinetic modeling of the methanol-to-olefins process on SAPO-34, Ind Eng Chem Res 43 5098—5111, 2004a. 

Van Speybroeck V, De Wispelaere K, van der Mynsbru e J, Vandichel M, Hemeboet K, Waroquier M First principle chemical kinetics in zeohtes the methanol-to-olefin process as a case study, Chem Soc Rep 43 7326—7357, 2014. 

Wragg DS, O Brien MG, Bleken FL, Di Michiel M, Obbye U, FJellvag H Watching the methanol-to-olefin process with time- and space-resolved high-energy operando X-ray diffraction, Angew Chem Int Ed 51 7956—7959, 2012. 

MTBE is produced by reacting methanol with isobutene. Isobutene is contained in the C4 stream from steam crackers and from fluid catalytic cracking m the crude oil-refining process. However, isobutene has been in short supply in many locations. The use of raw materials other than isobutene for MTBE production has been actively sought. Figure 2 describes the reaction network for MTBE production. Isobutene can be made by dehydration of i-butyl alcohol, isomerization of -butenes [73], and isomerization and dehydrogenation of n-butane [74, 75]. t-Butanol can also react with methanol to form MTBE over acid alumina, silica, clay, or zeolite in one step [7678]. t-Butanol is readily available by oxidation of isobutane or, in the future, from syngas. The C4 fraction from the methanol-to-olefins process may be used for MTBE production, and the C5 fraction may be used to make TAME. It is also conceivable that these... 

Reaction mechanism for the formation of DME by dehydration of methanol over H-ZSM-5 catalyst. (H" ) acidic site, MeOH (+) protonated methanol (methoxonium ion), /R, ) surface methoxy species, DMO" ) protonated DME (dimethyloxonium ion). Adapted from Park T-Y, Froment CF. Analysis of fundamental reaction rates in the methanol-to-olefins process on ZSM-5 as a basis for reactor desigfi and operation. Ind Eng Chem Res 2004 43 682-9 Park F-Y, Froment CF. Kinetic modelingofthe methanol to olefins process. 2. Experimental results, model discrimination, and parameter estimation. Ind Eng Chem Res 2001 40 4187-96 Park F-Y, Froment CF. Kinetic modelingofthe methanol to olefins process. 1. Model formulation. Ind Eng Chem Res 2001 40 4172-86. 

Reaction scheme (bs basic site of the catalyst, R carbenium ion ethyl, R carbenium ion propyl ). Adapted from Alwahabi SM, Froment GF. Conceptual reactor design for the methanol-to-olefrns process on SAPO-34. Ind Eng Chem Res 2004 43 5112-22 Alwahabi SM, Froment GF. Single event kinetic modelingof the methanol-to-olefins process on SAPO-34. Ind Eng Chem Res 2004 43 5098- 111. 

Barger PT, Lesch DA. Hydrothermal stability of SAPO-34 in the methanol-to-olefins process. Arab J Sci... 

In the development of the methanol-to-olefin process Union Carbide Corporation (UCC) synthesized SAPO-34 to be used as catalyst. SAPO-34 was considered to be the best catalyst, both with respect to activity and selectivity for the production of light olefins [24]. Ni substitution to this catalyst (NiAPSO-34) has been demonstrated to give high yields of ethylene from methanol [25-27]. In a recent paper [28] the four mentioned catalysts, HZSM-5, SAPO-34, NiASPO-34 and AI2O3, were compared with respect to selectivity, activity and stability. The optimal temperatures for the catalysts were 300, 350, 350 and 450 C, respectively. With respect to conversion of ethanol and selectivity to ethylene, HZSM-5 and NiAPSO-34 showed the best performance followed by SAPO-34 and AI2O3 in that order. NiAPSO-34 and SAPO-34 showed much better stability and the final conclusion was that NiAPSO-34 is the best choice in the production of ethylene from ethanol. 

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