Thomas Hsiao-Ling Hsiung

Novel technology for the synthesis of dimethyl ether from syngas

Abstract A novel process for producing dimethyl ether (DME) from synthesis gas in a single-step reaction sequence has been developed. The new process uses a slurry reactor in which methanol synthesis, methanol dehydration to DME, and water-gas shift reactions all proceed concurrently. All three reactions are exothermic and reversible. Operation with a back-mixed slurry reactor exploits synergisms of the three reactions, and moderates the reaction exotherm to permit higher conversion of the syngas to liquid products than could be achieved from the three reactions practiced separately. The process offers potential lower capital and operating costs than processes using individual shift, methanol, and DME reaction stages. Process development to-date has focused on the use of coal-derived synthesis gas that is rich in CO. Catalysts used in the process can be a physical mixture of methanol, shift, and dehydration catalysts. Selection of commercially available catalysts and the effect of their different ratios have been investigated. Some process variable results are presented. Commercial applications of the new process are illustrated. Further development of the process is currently underway. In the laboratory, the effects of temperature and feed composition are being studied in detail. Catalyst aging characteristics are also being defined. In addition, plans are being made to demonstrate the process in the Department of Energys Alternative Fuels Development Unit at LaPorte, Texas.

Single-step synthesis of dimethyl ether in a slurry reactor

Abstract Dimethyl ether (DME) is an important intermediate in several alternative fuels processes which ultimately convert synthesis gas to liquid products. Our work details a novel slurry-based process which yields DME and variable amounts of co-product methanol (MeOH) from synthesis gas in a single step. The water-gas shift, MeOH synthesis, and MeOH dehydration reactions proceed concurrently in a three-phase reactor. Operation with a back-mixed slurry reactor exploits the synergy of the three reactions, and moderates the reaction exotherm to permit high per-pass conversions. Feed gases with CO concentrations ranging from 20% to 60%, and H 2 /CO ratios varying from 0.01 to 2.9 have been tested with several multi-functional catalyst systems. The process offers the potential for both lower capital and operating costs compared to processes using independent shift, MeOH, and DME reactors.

Catalyst poisoning during the synthesis of methanol in a slurry reactor

Abstract A novel methanol synthesis process, the Liquid-Phase Methanol (LPMEOH ® 2 Process, has been developed and scaled up to a nominal 380 kg./hr. (10 ton/day) pilot plant. The process is based on a slurry reactor instead of a conventional, fixed-bed reactor. As in conventional methanol synthesis processes, the catalyst can be deactivated by chemical poisons and by thermal mechanisms. Laboratory and pilot-plant studies have shown that poisoning of the catalyst by iron and nickel carbonyls and by carbonyl sulfide is severe and highly specific. The rate of catalyst deactivation is very slow with a poison-free feedstream, even when the CO/H 2 ratio is substantially greater than stoichiometric.

Adsorptive Removal of Catalyst Poisons from Coal Gas for Methanol Synthesis

Abstract As an integral part of the liquid-phase methanol (LPMEOH) process development program, the present study evaluated adsorptive schemes to remove traces of catalyst poisons such as iron carbonyl, carbonyl sulfide, and hydrogen sulfide from coal gas on a pilot scale. Tests were conducted with coal gas from the Cool Water gasification plant at Daggett, California. Iron carbonyl, carbonyl sulfide, and hydrogen sulfide were effectively removed from the coal gas. The adsorption capacities of Linde H-Y zeolite and Calgon BPL carbon for Fe(CO)5 compared well with previous bench-scale results at similar CO2 partial pressure. Adsorption of COS by Calgon FCA carbon appeared to be chemical and nonregenerable by thermal treatment in nitrogen. A Cu/Zn catalyst removed H2S very effectively. With the adsorption system on-line, a methanol catalyst showed stable activity during 120 h of operation, demonstrating the feasibility of adsorptive removal of trace catalyst poisons from the synthesis gas. Mass transfer coe...

Thermal Deactivation of Methanol Synthesis Catalysts in A Slurry Reactor

Summary The deactivation of methanol-synthesis catalyst was studied in laboratory and pilot-plant slurry reactors using a concentrated, poison-free, CO-rich feedstream. The extent of catalyst deactivation correlated with the loss of BET surface area. A model of catalyst deactivation as a function of temperature and time was developed from experimental data. The model suggested that continuous catalyst addition and withdrawal, rather than temperature programming, was the best way to maintain a constant rate of methanol production as the catalyst ages. Catalyst addition and withdrawal was demonstrated in the pilot plant.