A process network towards a future methanol economy

Abstract

Introduction and objectives Besides hydrogen, methanol is suggested as a base component for a future methanol economy to replace fossil fuels. Methanol is already used today on a large scale to produce a variety of chemicals and products. The current main products are olefins and formaldehyde. These base chemicals are subsequently processed to produce a wide range of products integral to daily life, including paints, plastics, building materials, and automotive components. Additionally, with a heating value ranging from 19.66 to 22.2 MJ/kg, methanol is recognized as a valuable energy source. Nowadays, methanol is gaining significance as an alternative fuel, particularly in the shipping sector, and is discussed as an option for H2-storage and transport. Methodology Due to its applicability in multiple daily life product and potential as a fuel, the expected global demand for methanol is constantly increasing further amplifying the driving force for establishing sustainable synthesis methods of methanol, since, it is mainly produced from fossile resources via steam reforming of natural gas and subsequent catalytic conversion of formed synthesis gas. Process simulation is used to setup a network of processes to produce methanol based on renewable and carbon neutral sources, to show the potential and limitation of a future methanol economy. Process steps under investigation involve provision of raw materials, conversion technologies as well as utilization and processing options. As feedstocks biogenic waste streams, wood and forest residues are considered to obtain synthesis gas derived from biogas/biomethane reforming and biomass gasification. Besides synthesis gas, CO2 from different sources and throughout different technologies is considered - either capuring CO2 from hardly to abate sources (cement industy/iron and steel production) or based on renewable carbon sources like bioenergy carbon capture and storage (BECCS). Alternatively, direct air capture (DAC) as well as the use of CO2 as a gasification agent - thus working as carbon capture and utilization (CCU) technology for producing a CO-rich gas from renewable resources - are under investigation. Providing synthesis gas enables the production of methanol via established processes, however, considering potentially smaller plant scale. Starting from CO2, methanol can be produced in a one step conversion via direct hydrogenation of CO2. Alternatively, in two steps conversion, CO2 is first converted into CO through the Reverse Water Gas Shift (RWGS) reaction and then hydrogenated to methanol. Both options strongly depend on the development of new catalysts to improve the conversion efficiency of CO2 to methanol. Utilisation scenarios under investigation involve upgrading to pure methanol for use as a fuel. However, through the methanol-to-gasoline (MTG) and the methanol-to-olefin (MTO) process, methanol can also be converted to gasoline as well as ethylene and propylene – the latter two chemicals produced in largest amounts by the petrochemical industry. Although methanol is usually toxic for microbes, the methylotrophic yeast Pichia pastoris - widely used as cell factory for recombinant protein production - is able to efficiently use glycerol and/or methanol as energy and carbon sources, offering to extend the products that can be obtained form methanol. Results and conclusions Mass- and energy balances provided by process simulation will be improved applying heat and process integration and used to calculated key performance indicators (KPI) for selected process routes including methanol yield, biomass use and CO2 conversion, hydrogen and energy demand as well as generation of additional CO2-emissions. On a longer term the results will form the basis for LCA and technoeconomic analysis. Implementation in a process simulation environment allows picking selected routes for detailed analysis and optimization. Easily integration of new processes and applying improved catalysts enables the increase of conversion and process efficiencies as well as the consideration of changed boundary conditions. Acknowledgement This study was carried out within the doctoral college CO2 Refinery at TU Wien.