Novel Short Process for p-Xylene Production Based on the Selectivity Intensification of Toluene Methylation with Methanol

Abstract

Toluene methylation using methanol offers a high potential molecular engineering process to produce p -xylene (PX) based on shape-selective catalysts. To further improve the process economics, a novel short process was proposed by reducing the high-energy consumption separation of xylene isomers in existing processes since the PX selectivity of the xylene isomers can be enhanced more than the industrial product quality of 99.7%. The PX selectivity intensification was achieved as a result of decreased contact time by considering factors such as the feed ratio, diluents, temperature, and pressure in a toluene methylation reactor. This proposed short process indicated that the reactor effluent could be purified only through the two conventional distillation towers by removing the methanol recovery and separation of xylene isomers. The raw material utilization, energy consumption, and economic data were also analyzed for the six contrastive cases. The short process using catalyst Si–Mg–P–La/ZSM-5 exhibited the highest effective utilization rates of 96.27 and 95.50% for toluene and methanol, respectively. The short process also showed a good economic value in terms of capital investment and operating costs due to the multistage reactor without benzene byproducts. Thus, the obtained total annual cost (TAC) value of 13 848.1 k$·year –1 was 68.9 and 87.9% of the two existing processes.

Stiffening Polymer Brush Membranes for Enhanced Organic Solvent Nanofiltration Selectivity

“…To demonstrate the versatility of cross-linked brush membranes, we tested two commercially relevant feed solutions: (i) 80–20 mol % methanol–toluene and (ii) 95–5 mol % toluene–triisopropyl benzene (TIPB). − The methanol–toluene mixture is an industrially important separation frequently encountered in the synthesis of pharmaceuticals and fine chemicals. ,− The molecular weights of methanol and toluene are 32 and 92 g/mol, respectively, and mixtures form a low boiling azeotrope at high methanol concentrations. Additionally, this mixture is commonly separated by energy-intensive distillation or low-throughput adsorption and therefore presents an opportunity to use synthetic membranes to increase capacity and reduce cost.…”

p-Xylene Oxidation to Terephthalic Acid: New Trends

“…[ 15 , 16 ] Another major feature is the availability of pure p- xylene from the other isomers. As demonstrated by Wang et al [ 17 ], the production of p- xylene is still a challenge. Most catalytic systems tend to perform poorly when applied to the other isomers, and there is also a need to address the difficulty of separation.…”

Thermodynamic and Mechanistic Analyses of Direct CO2 Methylation with Toluene to para-Xylene

“…9,10 Generally, PX is produced using CO 2 as C1 feedstocks through two routes. One is the indirect methylation route including CO 2 hydrogenation to methanol 11,12 and subsequent methanol methylation with toluene, 7,13,14 where the metal oxide (MO X ) and modified zeolite are the catalysts for these two steps separately. The other one is the direct methylation route upon a bifunctional catalyst combining CO 2 hydrogenation and methylation as a tandem catalysis process.…”

“…Generally, PX is produced using CO 2 as C1 feedstocks through two routes. One is the indirect methylation route including CO 2 hydrogenation to methanol , and subsequent methanol methylation with toluene, ,, where the metal oxide (MO X ) and modified zeolite are the catalysts for these two steps separately. The other one is the direct methylation route upon a bifunctional catalyst combining CO 2 hydrogenation and methylation as a tandem catalysis process. − Similarly, syngas (CO + H 2 ), as another C1 feedstock, has also been introduced in the direct methylation route, − while direct CO 2 methylation with benzene has also demonstrated to be more advantageous. , For direct CO 2 methylation, Zuo and Yuan et al concluded that the methoxy H 3 CO* species formed on MO X preferably migrate into the channel of zeolite for methylation with adsorbed toluene rather than desorb as methanol.…”