Master of Engineering Science
Chemical and Biochemical Engineering
Herrera, Jose E.
A critical step for the synthesis of renewable oxy methyl ethers (OME) targeted towards diesel substitution, is the catalytic production of a dimethoxymethane/formaldehyde mixture from methanol and air. The bifunctional catalyst requirements needed for methanol to undergo both the acidic and oxidative steps required for dimethoxymethane formation have been recently established for TiO2-supported vanadia catalysts. However, translating these requirements to a catalyst capable of industrial operation remains a challenge. This thesis examines the considerations and adjustments needed to translate the molecular active phase to a large-scale catalytic pellet, including active phase distribution and possibility of hot-spot creation during catalysis. Multiple formulations are explored to evaluate the consequences on catalytic performance of systematic changes on vanadia dispersion as well as its distribution throughout the solid catalyst pellet. By controlling the distribution of vanadia, we constrained undesirable pathways in the reaction maximizing dimethoxymethane production; however, formaldehyde production was still slightly limited.
Summary for Lay Audience
Bio-derived oxy methyl ethers (OMEs) have the capacity to partially substitute diesel fuels providing an additional sustainable additive to transportation fuels, similar to the role ethanol plays in gasoline. A key starting stage in the manufacturing process of OMEs molecules is reacting a pure methanol gas stream with air to create an intermediate stream of dimethoxymethane (DMM) and formaldehyde, which can then be used for OME production. Methanol transformation to DMM and formaldehyde can be accomplished in a single step by exposing methanol to material than can speed up a process that involves both proton (acid reaction) and electron exchanges (redox reaction) between the molecules of methanol and air. This type of material is known as a bifunctional catalyst. Current work done on catalysts able to carry these transformations is conducted at the microscale, using milligram amounts of catalyst in laboratories, focusing on designing the molecular structure of the catalyst. For industrial operation to be realized, the size of the catalyst material must be scaled up. Scaling up requires in turn that the material preserves its original catalytic properties, but also that the material can offer performance levels required to handle industrial amounts of feedstock.
This thesis attempts to bridge the gap between the knowledge of the molecular structure required to produce DMM and the general industrial requirements for a scaled-up version of the catalyst and combine them to establish a protocol for the preparation of a catalyst capable of industrial production of an OME feed stream comprised of DMM and formaldehyde. To accomplish this several formulations of catalyst pellets were prepared, evaluated, and tested with altered molecular structures and/or altered distribution of catalytic material throughout the pellet. Altering the distribution of the catalytic phase through the pellet had a significant effect on the reaction as pellets with less vanadium available in the material core resulted in an increase on the production of unwanted side products. By improving the distribution of the catalytic phase material, the sites identified to be responsible for methyl formate production were covered. However, undesired by-products began to be produced via alternative routes.
Cook, Sebastian M K, "Catalytic Consequences of Catalyst Pellet Architecture on the Methanol to Oxymethylene Process" (2023). Electronic Thesis and Dissertation Repository. 9316.
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