H-ZSM-5 and γ-alumina were treated with formaldehyde and sodium carbonate. The treatment increased the
amounts of weak acid sites, removing strong acid sites. The maximum temperature of weak acid sites in their
ammonia TPD spectra shifted in the direction of high temperature. The modified H-ZSM-5 and γ-alumina were
mixed with the methanol synthesis catalyst to perform dimethyl ether synthesis from syn-gas. The modified
catalysts showed better selectivity to dimethyl ether, minimizing the reforming reaction to carbon dioxide. The
maximum yield of 53.3% to dimethyl ether was achieved under the reaction conditions of 54.4 atm, 523 K, and
the feed rate of 4500 Lhr−1·gcat−1.