Apparent kinetics and prospective operation on synthesizing Poly(oxymethylene) dimethyl ethers over shaped zeolite BETA in Fixed-bed reactor

Poly(oxymethylene) dimethyl ethers (PODE n=3-5 ), as promising diesel additive, were synthesized by reaction of 1,3,5-Trioxan (TOX) and methylal (PODE 1 ) on the catalyst of zeolite BETA in a fixed-bed reactor and kinetically researched under reaction temperature from 308 to 358 K, initial mole ratio 3∙ N TOX / N PODE1 from 0.8 to 1.2, space time from 0.33 to 20.78 min⋅kg⋅l −1 and water content from 0 to 2  wt %. A series of rate laws were formulated for quantifying not only their reaction rates but also the role of water. The obtained activation energies of propagation and decomposition reactions of PODE n (n = 3 ∼ 8) are 22.89 kJ⋅mol −1 and 27.46 kJ⋅mol −1 respectively, and their pre-exponential factors depend on the “n” in PODE n . Through optimizing the Schulz-Flory distribution of PODE n based on the kinetics, the maximal selectivity of TOX to PODE 3-5 of 57.80% will achieve under anhydrous conditions, while this will become 54.60% under 5  wt % water in TOX.