Chemical Engineering Research & Design, Vol.166, 121-134, 2021
Sustainable process design for manufacturing acrylic acid from glycerol
Acrylic acid is a high-value monomer produced today only from petrochemical resources. This paper investigates the conceptual design of an eco-efficient process using renewable low-cost glycerol. The key step is glycerol dehydration to acrolein, performed in a fluidized bed reactor employing fast nanosheet zeolite catalyst. The investigation makes use of hydrodynamic modelling and computer simulation in Aspen Plus. The feasibility of four alternatives is studied: conventional bubble (BFB) and turbulent (TFB) fluidized bed, as well as two types of circulating fluidized bed (CFB) reactors. Working with smaller bubble size, in the range 2.5-10 cm, a BFB reactor may achieve a productivity of 0.45 kg/kg-cat h for 99.7% conversion, which is only 20% of the performance of an ideal plug flow reactor. Changing to TFB regime raises the productivity to 0.9 kg/kg-cat h. Implementing CFB reactors leads to a spectacular improvement. High productivity of 3 and 4 kg/kg-cat h is achieved with turbulent (CTFB) and high-density (HD-CFB) reactors, respectively. The TFB reactor is preferred when catalyst coking is low or moderate, while CTFB is favoured when continuous regeneration is needed. Employing m-xylene driven azeotropic distillation leads to the lowest energy consumption reported so far by acrylic acid purification. The integration of reaction and separation sections by combined heat and power system leads to a positive energy process. Dynamic simulation demonstrates flexibility and robustness of the separation section faced with disturbances occurring in the reaction system. The sustainability indices show substantial improvement in eco-performance with respect to the propylene-based process. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.