Published June 2018
This review presents a technoeconomic analysis of an ester-grade acrylic acid (EAA) manufacturing process, commercialized by BASF Corporation. BASF is one of the largest producers of crude acrylic acid (CAA). BASF follows the conventional vapor-phase, two-stage propylene oxidation chemistry, in which the first stage oxidizes propylene to acrolein, and the second stage oxidizes acrolein to acrylic acid. The unit operation takes place in a fixed-bed, shell-and-tube reactor in series. Ester-grade acrylic acid is recovered by crystallization of reactor effluent.
Acrylic acid is a major building block in the production of many industrial and consumer products. Acrylic acid demand is driven by two factors. One is the growing demand for glacial acrylic acid (GAA) for superabsorbent polymers for the production of diapers and other hygiene products. The other is in the more industrial sectors—paint, coatings, and resin formulations—which account for more than 50% of acrylic acid demand.
Acrylic acid is produced in only 17 countries in the world, with plants on all continents except Australia. In 2016, world production of acrylic acid was estimated to be approximately 5.6 million metric tons, with Northeast Asia holding the largest share at 50%, and China accounting for almost 67% of the regional capacity and 39% of the global capacity. The second-largest producing region is North America, with approximately 19%. Well over 70% of global acrylic acid production capacity is concentrated in the business of the top 10 producers. The largest global producer is BASF, with 10% of the global capacity—far ahead of the second-largest producer, Dow.
In the first reaction stage, propylene is oxidized with air in the presence of steam to form acrolein. The oxygen-to-propylene molar ratio is generally 1.6 to 2.0. Propylene concentration in the range of 7–15 vol% can be used. Steam and nitrogen (in air) are used as diluents. The reaction temperature is in the 300–350°C range, and the reaction pressure is 0.1–0.5 MPa (14.5–72.5 psi). The space velocity is in the range of 500–3,000 hr-1. One-pass propylene conversion is high, >96%, and selectivity to acrolein and acrylic acid is >94%.
The second reaction stage oxidizes acrolein to acrylic acid. The reaction is highly exothermic. The typical feed concentration to the second-stage reactor is 1–15 vol% acrolein, 1–10 vol% O2, and the balance diluent gases such as N2, CO2, and H2O. The reactor temperature is 240–300°C, and the space velocity is 300–5,000 hr-1 (STP). One-pass acrolein conversion is high, >96%, and selectivity to acrylic acid is >94%.
This review updates the process of BASF technology that was presented in PEP Report 6D, Acrylic Acid and Esters, published in July 2003. The focus of this review includes capital and production costs for 160,000 metric tons/yr of acrylic acid product by a stand-alone plant, along with utilities consumptions and equipment sizes. An interactive module is included—the iPEP Navigator for acrylic acid—that provides a snapshot of the process economics and allows the user to select the units and global region of interest.