(693b) Single-Step Co-Synthesis of Methanol, Dimethyl Ether and Dimethyl Carbonate from Biomass Derived Syngas

Gasification of biomass to syngas (CO, CO₂ and H₂) is attractive biomass utilization route due to high throughput, fast reaction rates, and low separation costs. Moreover, the syngas from biomass paves way for the greener synthesis route for important industrial intermediates, oxygenates and solvents such as methanol, dimethyl ether (DME) and dimethyl carbonate (DMC). The production of DME and DMC are industrially mature technologies that are carried out as a two-step process via methanol dehydration and methanol oxy-carbonylation respectively. However, the single-step co-synthesis of these chemicals from syngas has not been reported. Moreover, the enhanced utilization of CO₂ requires the use of novel catalytic systems for improved yields and selectivity.

In this research, mixed-oxide supported Cu and In₂O₃ catalysts have been developed and specifically the support-active component effects have been investigated. CeO₂-ZrO₂ mixed oxides have been used as the supports in this study mainly because of their varying acidity and basicity that influence the product distribution. The chemical synthesis experiments using the developed catalysts were carried out in the range of 100-300^oC, 20-50bar and a space velocity of 23000-60000 hr^-1 in a tailor-made high pressure packed bed reactor with an online GC-TCD/FID/FPD analyser. In-depth catalyst characterization was conducted including the in-situ synchrotron powder diffraction, X-ray absorption spectroscopy, in-situ diffuse reflectance infrared Fourier transform (DRIFTS) and scanning transmission electron microscopy (STEM).

Several optimization experiments were carried out including the influence of process parameters such as temperature, pressure, space velocity and CO co-feeding in addition to catalyst parameters such as support composition (Ce/Ce+Zr=0,0.2,0.5,0.8,1) and active metal loading. The products from the synthesis include DME, methanol, DMC and methane. Support composition has a strong influence on the yields and product selectivity. The novel catalysts developed in this study exhibit exceptional performance in terms of yields and stability compared to the ones reported in literature. CeO₂ support was found to be the most efficient for both the Cu (0.47g_MeOH h^-1 g_Cu^-1) and In₂O₃ (1.5 g_MeOH h^-1 g_In^-1) catalysts. The results from this study contribute to significant process improvement through the design of a versatile catalyst enabling co-production of methanol, DME and DMC.