The transesterification of propylene carbonate (PC) or ethylene carbonate (EC) to dimethyl carbonate (DMC) by using catalytic reactive distillation (RD) is a promising approach for carbon dioxide utilization. However, there is still scarcity of comprehensive comparison between the two RD processes. Hence, using the UNIQUAC model and kinetics calibrated by literature and our experiments, we conduct an extensive comparison of the two RD processes. Based on the kinetic insights, laboratory RD processes for both reactions are modeled, analyzed, and experimentally validated. Consequently, two RD processes designed to produce 60 ktpy of DMC are optimized and compared. The interplay and control factors between reaction and separation are elucidated and clarified via investigating variations of the actual chemical equilibrium constant profile compared with theoretical values along the reactive section at various pressures, liquid holdups, etc. The results reveal that the optimized EC RD process achieves almost 50 % reductions in both total annual cost and carbon dioxide emission compared to the PC RD process. This work facilitates the carbon neutrality and provides an essential guide for quantitatively assessing the two routes.

Ethanol is used to produce various value-added chemicals and as automobile fuel. Acetic acid hydrogenation to ethanol is of practical significance to meet the increasing market. However, limited engineering research for reactor and crude separation process for the acetic acid hydrogenation to ethanol despite the increasingly mature catalyst system. Moreover, the traditional approach of industrial reactor design mainly relies on point data and inadequately quantifies the strong coupling between reaction rate and transfers within the reactor, which is prone to local and loose design and optimization. In this work, a coupled design approach that combines kinetics with transfers is proposed for designing and optimizing the multi-tubular fixed-bed reactor for the acetic acid hydrogenation to ethanol. To efficiently achieve the products crude separation, staged cooling/flash/absorption/desorption units featuring with N-methyl-2-pyrrolidone as an absorbent is proposed, numerically designed and optimized. Further heuristic heat integration is also investigated to conserve extra energy of the preliminary process, which features that a by-product steam generated from ethanol synthesis reactor is utilized to drive the reboiler of the desorption. It is demonstrated that the heat-integrated process presents significant economic and emission advantages compared with the preliminary process, specifically with 36.5 % and 10.9 % reductions in operating cost and total annual cost respectively, as well as 58.1 % reductions in CO₂ emissions. The cost of synthesizing ethanol with 100 ktpy production is as low as 14.25 $/t. This work could provide a feasible and promising reactor and crude separation process for acetic acid hydrogenation to ethanol, which features economic, high-efficient, energy-saving, and low-carbon.

The one-step methanol oxidation to dimethoxymethane (DMM) is a promising method for value-added chemical synthesis. However, vanadium cerium (VCe) catalysts commonly exhibit insufficient DMM selectivity in spite of its moderate high-temperature methanol conversion. In this work, titanium dioxide (TiO2) with relatively strong acidity was introduced into VCe catalyst to improve the catalysis performance of VCe. The results showed that the addition of TiO2 enhanced the oxidation reduction and surface acidity of the catalyst, and effectively improved the selectivity and yield of DMM. Furthermore, a scaled-up conceptual process for the one-step oxidation of methanol to DMM was explored, designed and economically evaluated based on the TiO2 modified catalysts. The entire conceptual process featured that multiple condensation-separation/absorption units offered a complete collection of the DMM. Through the optimization of the process, the generated products and unreacted methanol can be directly stripped from N2 and O2, and complete separation of DMM-methanol azeotrope was achieved with only one vacuum distillation unit. The entire process at what catalysis performance (methanol conversion, DMM selectivity, etc.) could bring profit was revealed and discussed. This study emphasizes the interaction between catalyst design, conceptual process design and economic evaluation, providing new ideas for the development of efficient industrial catalysts.