Liquid phase methanol and dimethyl ether synthesis from syngas

Abstract

The Liquid Phase Methanol Synthesis (LPMeOH TM ) process has been investigated in our laboratories since 1982. The reaction chemistry of liquid phase methanol synthesis over commercial Cu/ZnO/Al 2 O 3 catalysts, established for diverse feed gas conditions including H 2 -rich, CO-rich, CO 2 -rich, and CO-free environments, is predominantly based on the CO 2 hydrogenation reaction and the forward water-gas shift reaction. Important aspects of the liquid phase methanol synthesis investigated in this in-depth study include global kinetic rate expressions, external mass transfer mechanisms and rates, correlation for the overall gas-to-liquid mass transfer rate coefficient, computation of the multicomponent phase equilibrium and prediction of the ultimate and isolated chemical equilibrium compositions, thermal stability analysis of the liquid phase methanol synthesis reactor, investigation of pore diffusion in the methanol catalyst, and elucidation of catalyst deactivation/regeneration. These studies were conducted in a mechanically agitated slurry reactor as well as in a liquid entrained reactor. A novel liquid phase process for co-production of dimethyl ether (DME) and methanol has also been developed. The process is based on dual-catalytic synthesis in a single reactor stage, where the methanol synthesis and water gas shift reactions takes place over Cu/ZnO/Al 2 O 3 catalysts and the in-situ methanol dehydration reaction takes place over c-Al 2 O 3 catalyst. Co-production of DME and methanol can increase the single-stage reactor productivity by as much as 80%. By varying the mass ratios of methanol synthesis catalyst to methanol dehydration catalyst, it is possible to co-produce DME and methanol in any fixed proportion, from 5% DME to 95% DME. Also, dual catalysts exhibit higher activity, and more importantly these activities are sustained for a longer catalyst on-stream life by alleviating catalyst deactivation.

In-situ regeneration mechanisms of hybrid catalysts in the one-step synthesis of dimethyl ether from syngas

“…Lee and Sardesai [10] found that in the LPMeOH process, deactivated catalysts restored their activity through a redox cycle. According to Andreasen et al [13], in gas-phased methanol synthesis over Cu, Zn solid solution oxide catalyst, the shape and size of Cu crystalline have undergone a reversible change during a redox cycle.…”

“…In these studies, different problems associated with Cu-based catalyst deactivation, such as Cu particle sintering and coke deposition, are approached [7][8][9]. In the LPMeOH process, Lee and Sardesai [10] found that sintering velocity of Cu particles was dependent on reaction conditions. The rate of thermal aging and the crystal growth pattern of methanol synthesis catalyst slowed down, when it was used in a co-production mode along with c-alumina.…”

Experimental and theoretical study of the intrinsic kinetics for dimethyl ether synthesis from CO2 over Cu–Fe–Zr/HZSM‐5

“…However, DME synthesis generates more water than methanol synthesis alone, and as such, the activity and stability of catalysts could be adversely affected by the hydrophilicity of ZnO. 17,18 By considering recent research that used a CuO-ZnO-based catalyst in the catalysis of the one-step process 6,11 as well as reports of Cu-Fe-based catalysts that have been used to synthesize CO and CH 4 , 19,20 and taking into account the fact that ZrO 2 is often used as a textural promoter, 11,[21][22][23] a bifunctional catalyst was developed using CuO-Fe 2 O 3 -ZrO 2 as the methanol synthesis component and HZSM-5 as the methanol dehydration component. 24 Up until this point, studies regarding the kinetic aspects of DME synthesis have focused on its generation from syngas: Iliuta et al 25 have elucidated a model for DME synthesis in a fixed-bed membrane reactor, and Sierra et al 26 investigated the deactivation kinetics for direct DME synthesis on a CuO-ZnO-Al 2 O 3 /c-Al 2 O 3 catalyst, among other works.…”

A one-step Cu/ZnO quasi-homogeneous catalyst for DME production from syn-gas

“…[6][7][8][9][10] Hybrid catalytic systems comprising a heterogeneous Cu-based methanol synthesis catalyst and a solid acid as methanol dehydration catalyst are well suited for the direct DME synthesis process. Most often, the well-known heterogeneous Cu-ZnO-Al 2 O 3 ternary methanol catalyst is combined with -Al 2 O 3 or zeolites for methanol dehydration.…”