Makarand R. Gogate

A novel single-step dimethyl ether (DME) synthesis in a three-phase slurry reactor from co-rich syngas

Abstract The productivity of liquid phase methanol synthesis reactor in limited by the chemical equilibrium barrier caused by high local methanol concentration in the liquid phase. This barrier can be partly lifted by either selective physical remoal of methanol from the liquid phase or in-situ conversion to other chemical species. A novel process for manufacturing dimethyl ether (DME) from CO-rich syngas in the liquid phase has been developed. Two functionally different catalysts are slurried in the inert liquid phase, in this dual catalytic mode of operation. The (methanol+DME) co-production approach is extremely effective in increasing the per-pass syngas conversion and reactor productivity over those of methanol synthesis alone. The co-production approach can also co-produce methanol and DME in any fixed proportion, from practically pure DME to pure methanol. Scientific aspects of the process including the process feasibility domain, reaction kinetics, catalytic management, and thermodynamic modeling will be discussed.

Methanol-To-Gasoline vs. . . . DME-To-Gasoline. II. Process Comparison and Analysis

Abstract Methanol can be converted into gasoline boiling range hydrocarbons over zeolite ZSM-5 catalyst using the Mobil MTG process. Methanol feed in the MTG process can be derived from coal or natural gas based syngas. The Mobil MTG process involves the conversion steps of syngas-to-methanol and methanol-to-gasoline. Dimethyl Ether (DME), a product of methanol dehydrocondensation, is an intermediate species in the methanol-to-gasoline conversion. Syngas can be directly converted to DME using the Liquid Phase Dimethyl Ether Synthesis (LP-DME) process developed at the University of Akron in conjunction with Electric Power Research Institute. This direct one-step conversion of syngas-to-DME can then be an ideal front end for further conversion to gasoline. This substitution (syngas-to-methanol by syngas-to-DME) is justified because DME results in an identical hydrocarbon distribution over the ZSM-5 catalyst as methanol. The DME-to-Gasoline (DTG) process thus involves the conversion steps of syngas-to-DME an...

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS I. DUAL CATALYTIC ACTIVITY AND PROCESS FEASIBILITY

ABSTRACT A novel process for manufacturing dimethyl ether (DME) from CO-rich syngas in a single stage has been developed. This novel approach was based on the application of dual catalysis in the liquid phase process, in which two functionally different catalysts are slurried in the inert mineral oil. The experimental reaction rate studies for methanol and dimethyl ether synthesis were conducted in a three-phase, mechanically agitated slurry reactor. The effects of catalyst ratio, temperature, and pressure on the dual catalytic activity were studied. The experimental data bear additional significance because this is the first study of such kind to be conducted on the liquid phase methanol synthesis process.

MASS TRANSFER IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS

ABSTRACT The mass transfer characteristics of the liquid phase methanol synthesis process were experimentally investigated using a one-liter, mechanically agitated slurry reactor. The CuO/ZnO/Al2O3 catalyst was crushed to -140 mesh and suspended in an inert mineral oil (Witco # 40). The catalyst loading was varied within limits of experimental feasibility. The effects of temperature, pressure, level of oil, impeller speed, and gas flow rate on the overall gas-liquid mass transfer coefficient KLiaB were studied The results obtained using a two-level, half-fractional factorial design of experiments indicated that the impeller speed, feed flow rate, and temperature had significant effects on the mass transfer coefficient at the experimental conditions examined. Correlations were developed for the Sherwood number based on the Reynolds number, the Schmidt number, the reciprocal gas flow number, the gas-liquid viscosity ratio, and the dimensionless temperature. A simplified power-law type approach was also used...

KINETICS OF LIQUID PHASE CATALYTIC DEHYDRATION OF METHANOL TO DIMETHYL ETHER

ABSTRACT The kinetics of the liquid phase catalytic dehydration of methanol to dimethyl ether were investigated. The experiments were carried out under low concentrations of feed in a 1-L stirred autoclave, according to a statistical experimental design. The inert liquid phase used for this investigation was a 78:22 blend of paraffinic and naphthenic mineral oils. A complete thermodynamic analysis was carried out in order to determine the liquid phase concentrations of the dissolved species. A global kinetic model was developed for the rate of dimethyl ether synthesis in terms of the liquid phase concentration of methanol. The activation energy of the reaction was found to be 18,830 cal/gmol. Based on a step-wise linear regression analysis of the kinetic data, the order of the reaction which gave the best fit was 0.28 with respect to methanol. Effects of the solid to liquid and the gas to liquid mass transfer resistances on the kinetic rate have also been investigated.

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS IV. THE WODYNAMIC ANALYSIS OF THE LPDME PROCESS SYSTEM

Abstract In the LPDME process, methanol synthesis catalyst (composed of CuO, ZnO, and Al2O3) and the methanol dehydration catalyst (gamma-alumina) are slurried in the inert liquid phase. The catalysts constitute the solid phase. Syngas components (H2, CO, CO2, and CH4) and the products (CH3OH, H2O, and DME) constitute the vapor phase. At least three chemical reactions, viz., methanol synthesis, water-gas shift, and methanol dehydration also occur simultaneously in the liquid phase. The multicomponent phase equilibrium and the simultaneous chemical reaction equilibrium for this process system have been studied. The thermodynamic analysis has been presented in terms of the equilibrium conversions for H2and CO, syngas, and the concentration driving forces for H2 and CO. Methanol synthesis alone and co-production of methanol and DME are compared. The effects of water and CO2addition to the feed syngas on the equilibrium conversions are also investigated.

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS II. COMPARISON OF PER-PASS SYNGAS CONVERSION, REACTOR PRODUCTIVITY AND HYDROGENATION EXTENT

ABSTRACT In part I of this series on the development of a single-stage, liquid-phase dimethyl ether (DME) synthesis process from syngas, the process feasibility and the process variable effects on the dual catalyst activity were discussed. This part focuses on the comparison of the single-stage reactor productivity of liquid phase methanol synthesis to that of the co-production of methanol and DME. It is experimentally demonstrated that the single-stage reactor productivity for the co-production of methanol and DME could be as much as 60% higher than that for liquid phase methanol synthesis alone. Along with this, a 50% increase in the syngas conversion is also obtained. Further, this approach is shown to co-produce methanol and DME in any fixed proportion, ranging from 5% DME to 95% DME, at significant synthesis rates of DME.

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS III. DUAL CATALYST CRYSTAL GROWTH, DEACTIVATION, AND ACTIVITY CONSERVATION STUDIES

ABSTRACT In the liquid phase dimethyl ether (DME) synthesis process, both the methanol synthesis catalyst )composed of CuO, ZnO, and Al2O3) and the methanol dehydration catalyst (composed of gamma-alumina) are slurried in the inert oil phase. Various long-term activity checks were conducted on these dual catalysts to characterize the crystal growth and the thermal aging behavior. X-ray powder diffraction, X-ray fluorescence and elemental intensity compositions, and the crystallite size distributions of the aged catalysts were examined. Based on the current investigation, it was established that the crystal growth and the catalyst deactivation problems in the methanol synthesis catalyst are less severe when it is used along with the methanol dehydration catalyst.

DESIGN AND OPERATION OF A FLUIDIZED BED REACTOR MINI-PILOT PLANT FOR GASOLINE SYNTHESIS

Abstract MethanoI-to-Gasoline (MTG) process is an excellent process which produces aromatics-rich gasoline from methanol over the ZSM-5 catalyst. The methanol feed in this process is usually derived from coal or natural gas based syngas. The dehydration of methanol to dimethyl ether (DME) is a key intermediate step in converting methanol into gasoline. The substitution of syngas-to-methanol step in the MTG process by the direct one stage conversion of syngas-to-DME is thus a very attractive option. This substitution is particularly justified on the basis of the fact that DME results in virtually identical hydrocarbon product distribution as methanol. Synthesis of gasoline via this direct DME route has several significant advantages over the MTG process, in the areas of product yield, selectivity, overall syngas conversion, exothermicity, and reactor size. The conceptual advantages of this DME-to-gasoline (DTG) process can be demonstrated in a laboratory scale fluidized bed gasoline synthesis unit. This pa...

The direct, one-step process for synthesis of dimethyl ether from syngas. III. DME as a chemical feedstock

ABSTRACT In Parts I & II of this Series, we illustrated the process research studies on a new, trendsetting indirect syngas conversion process, the direct, one-step LPDMEtm process, which is now a shining example of “dual catalysis” or “cooperative/adaptive” catalysis and also of thermodynamic/kinetic coupling in series-parallel reactions. In this part III, we take a look at several processes on the research and pilot scale that employ methanol and DME as chemical feedstocks for further conversion to value-added chemicals. A most rational and cogent argument for the use of DME as a feedstock is that the unit production cost of DME from the direct, one-step DME processes, most notably the LPDMEtm process, can be lower than methanol (from LPMeOHtm), on a methanol-equivalent basis. DME also has inherently more benign physical and chemical properties, contains 1 less mole of water, and results in a substantially similar product distribution, as methanol, for the methanol-to-gasoline (MTG) and methanol-to-olefins (MTO) process. DME can also be converted to several other important chemicals; some of these include dimethoxymethane, dimethoxyethane, methylal, formaldehyde, acetic acid, methyl acetate, and polyoxymethylene ethers. In this report, we offer a critical assessment of the current status of these processes and a projected path to commercialization. Considering the trendsetting and impactful nature of DME as a chemical entity and as a chemical feedstock, along with its “free” cost, we are of the opinion that the future of DME, and of its chemical conversions, as so-called “DME economy”, is very bright.