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In the context of the bio-based economy, lignin is a major source of aromatic compounds. Fast pyrolysis of lignin with catalytic reforming of the liquid fraction provides an efficient approach for producing aromatic hydrocarbons (AHs) as fuel additives. Methoxy compounds abundantly exist in the primary liquid products from fast pyrolysis of lignin, which further convert into phenolic and aromatic compounds via secondary pyrolysis and the upgrading reactions. This thesis focuses on the decomposition mechanism of the methoxyl group, using anisole as a model compound. Methyl transfer (transmethylation) as the primary reaction of the thermal decomposition of anisole, led to the prominent production of phenolic compounds (Phs). Plausible mechanisms for both non-catalytic and catalytic transmethylation were proposed, based on the analyses of the active sites on anisole and phenol by the means of DFT modelling. The intrinsic transfer orientation preferences onto relevant compounds were then predicted by corresponding reaction energy barriers. Experiments investigated the decomposition of anisole in a fluidized bed reactor over no catalysts and a series of HZSM-5 zeolite catalysts with different Si/Al atomic ratios. Study on transmethylation illustrated how the acid catalysts promoted the preferential formation of Phs. Deoxygenation reaction of the Phs as second stage reaction at higher temperatures produced AHs. Metal loaded acid (Bi-functional) catalysts designed by multiscale modelling were used in the investigation. Novel mechanism of anisole decomposition over bi-functional catalyst was proposed with the illustration of each role for metal and acid site in the catalysis. DFT modelling also predicted the reaction energy barriers of deoxygenation for various Phs to exhibit the metals effect in promoting the reactions. Experiments of anisole decomposition over the designed single and bi-metal based bi-functional catalysts revealed the distinct characteristics of each metal loading and their synergistic effect in promoting the BTX production.