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.
Condensation reaction of a propionate with formaldehyde is a novel route for synthesis of methyl methacrylate (MMA). The reaction mechanism involves a proton abstraction from the propionate on the basic sites and activation of the aliphatic aldehyde on the acidic sites of the catalyst. The acid-base properties of ternary V-Si-P oxide catalysts and their relation to the NWA yield in the vapor phase condensation of formaldehyde with propionic anhydride has been studied for the first time. Five different V-Si-P catalysts with different atomic ratios of vanadium, silicon, and phosphorous were synthesized, characterized, and tested in a fixed-bed microreactor system. A V-Si-P 1:10:2.8 catalyst gave the maximum condensation yield of 56% based on HCHO fed at 300{degrees}C and 2 atm and at a space velocity of 290 cc/g cat{center_dot}h. A parameter called the ``q-ratio`` has been defined to correlate the condensation yields to the acid-base properties. The correlation of q-ratio with the condensation yield shows that higher q-ratios are more desirable. The long-term deactivation studies on the V-Si-P 1: 10:2.8 catalyst at 300{degrees}C and 2 atm and at a space velocity of 290 cc/g cat{center_dot}h show that the catalyst activity drops by a factor of nearly 20 over a 180 h period. The activity can be restored to about 78% of the initial activity by a mild oxidative regeneration at 300{degrees}C and 2 atm. The performance of V-Si-P catalyst has been compared to a Ta/SiO{sub 2} catalyst. The Ta- catalyst is more stable and has a higher on-stream catalyst life.
or propionic acid with formaldehyde. RTI has demonstrated a novel correlation among the catalyst acid-base properties, condensation reaction yield, and long-term catalyst performance. Eastman and Bechtel have used the RTI experimental results of a 20 percent Nb/Si0{sub 2} catalyst, in terms of reactant conversions, MAA selectivities, and MAA yield, for their economic analysis. Recent research focuses on enhancing the condensation reaction yields, a better understanding of the acid-base property correlation and enhancing the catalyst lifetime.
Research Triangle Institute (RTI), Eastman Chemical Company, and Bechtel have developed a novel process for synthesis of methyl methacrylate (MMA) from coal-derived syngas, under a contract from the US Department of Energy/Fossil Energy Technology Center (DOE/FETC). This project has resulted in five US patents (four already published and one pending publication). It has served as the basis for the technical and economic assessment of the production of this high-volume intermediate from coal-derived synthesis gas. The three-step process consists of the synthesis of a propionate from ethylene carbonylation using coal-derived CO, condensation of the propionate with formaldehyde to form methacrylic acid (MAA); and esterification of MAA with methanol to yield MMA. The first two steps, propionate synthesis and condensation catalysis, are the key technical challenges and the focus of the research presented here.
Research Triangle Institute (RTI), Eastman Chemical Company, and Bechtel collectively are developing a novel three-step process for the synthesis of methyl methacrylate (MMA) from coal-derived syngas that consists of the steps of synthesis of a propionate, its condensation with formaldehyde to form methacrylic acid (MAA), and esterification of MAA with methanol to produce MMA. RTI has completed the research on the three-step methanol-based route to MMA. Under an extension to the original contract, RTI is currently evaluating a new DME-based process for MMA. The key research need for DME route is to develop catalysts for DME partial oxidation reactions and DME condensation reactions. Over the last month, RTI has finalized the design of a fixed-bed microreactor system for DME partial oxidation reactions. RTI incorporated some design changes to the feed blending system, so as to be able to blend varying proportions of DME and oxygen. RTI has also examined the flammability limits of DME-air mixtures. Since the lower flammability limit of DME in air is 3.6 volume percent, RTI will use a nominal feed composition of 1.6 percent in air, which is less than half the lower explosion limit for DME-air mixtures. This nominal feed composition is thus considered operationally safe, for DME partial oxidation reactions. RTI is also currently developing an analytical system for DME partial oxidation reaction system.
As a stand-alone reaction, it is an important industrial reaction used in the manufacture of ammonia, to balance the H2/CO ratio, and provide pure H2 at the expense of CO. It is also an important side reaction that occurs in parallel to the main synthesis reactions in conjunction with steam reforming of methane (over Ni-based catalysts), and methanol synthesis from CO/CO2/ H2 mixtures (over Cu/ZnO/Al2O3) [1-4]. The WGSR is also a critical component in reducing CO concentrations from feed gas streams in proton exchange membrane fuel cells (PEMFC). The Pt electrodes are highly susceptible to CO poisoning to levels as low as 1ppm [5,6].
The use of coal-derived syngas to produce high value chemicals is an important means of upgrading this resource. One example of a chemical that can be produced from coal-derived syngas is methyl methacrylate (MMA). Poly-methyl methacrylate is widely used in coatings and in various industrial molded products. The most widely practiced commercial technology for the synthesis of MMA is the acetone cyanohydrin (ACH) process. This process requires handling of large quantities of toxic hydrogen cyanide and generates one mole of ammonium bisulfate waste per mole of MMA. This bisulfate must either be regenerated or discarded, either of which substantially increases the cost. The ACH technology is thus environmentally and economically untenable for any new MMA plant expansions that would be needed to meet increasing demand. The RTI-Eastman-Bechtel research team is developing an alternative, environmentally benign route to MMA consisting of three steps; (step 1) synthesis of a propionate from ethylene, carbon monoxide, and steam, (step 2) condensation of this propionate with formaldehyde, and (step 3) esterification of resulting methacrylic acid with methanol to form MMA. This paper describes the preliminary economics of the overall process compared to other emerging processes, and focuses on step 2, including long term testing ofmore » catalysts for the condensation of propionic acid with formaldehyde to form MAA.« less
