Fine Chemicals

Acetonitrile production via ammonolysis of acetic acid

Background Art

　　The primary use of acetonitrile is as a solvent, serving, for example, as an extractant for butadiene and isoprene, a spinning solvent in the production of synthetic fibers, and a solvent for certain oils, phenols, and colored substances. In the fats and oils industry, it is employed as a solvent for extracting fats from animal and vegetable oils; in pharmaceuticals, it functions as a reaction medium for the recrystallization of steroidal drugs. Acetonitrile also serves as an intermediate in the manufacture of pharmaceuticals (such as vitamin B1) and fragrances, and it is a feedstock for producing 2‑methylpyridine, triazines, ethylamines, diacrylonitrile, imidazole, and propylene‑bis‑acetonitrile, among others.

　　In the conventional process for synthesizing and purifying acetonitrile via the ammonolysis of acetic acid, acetic acid and ammonia are first vaporized and then fed into a reactor. Under the catalytic action of an alumina‑supported catalyst, an ammonolysis reaction yields acetonitrile. The crude product obtained at the end of the reaction contains acetonitrile, water, and a small amount of ammonia. After ammonia is removed by absorption in a two‑stage absorber, the stream is sequentially sent to a concentration column, a vacuum tower, and a pressurized tower to produce the final acetonitrile product.

　　Because acetonitrile forms an azeotrope with water (at atmospheric pressure, the acetonitrile–water azeotrope contains approximately 16 wt.% water), conventional distillation cannot directly refine the acetonitrile mother liquor from the absorption section into commercial‑grade acetonitrile (which typically has a water content of ≤0.1 wt.%). Currently, in the ammoniation process for producing acetonitrile from acetic acid, acetonitrile is usually purified using one concentration column, one vacuum column, and one pressurized column. Such processes are characterized by high steam consumption, large equipment footprints, lengthy process flows, substantial liquid circulation, complex operation, and low acetonitrile yields.

Traditional craftsmanship

New process

Technological Advantages

　　The new process developed by Jiutian High-Tech boasts a high recovery rate, a simple process flow, a high safety margin, and excellent energy efficiency. It features a small feed‑liquid circulation volume and low operating energy consumption—compared with the conventional process, which consumes 4 t of steam per ton, the new process requires only 1.6 to 2 t per ton—and involves no addition of third‑party components.

Engineering Case Studies

　　Shandong Huihai, Nantong Liyang

Shandong Huihai’s 10,000-ton-per-year acetonitrile plant

Hydrogenation of acetone to produce isopropanol

Background Art

　　Isopropyl alcohol is an important chemical product and raw material with a wide range of applications. China is the largest importer of isopropyl alcohol in Asia. Currently, domestic production stands at approximately 160,000 tons per year; however, constrained by factors such as feedstock availability, process technology, and environmental regulations, domestic output falls far short of annual market demand. In 2010, imports totaled 115,000 tons, while in 2011 they amounted to 100,000 tons. The direct hydration of propylene is the primary industrial route for producing isopropyl alcohol, involving the direct hydration of propylene over a catalyst to yield isopropyl alcohol, with n‑propanol as a co‑product. Due to tight domestic propylene supplies, this process entails high propylene consumption and energy use, resulting in elevated production costs. By contrast, domestic acetone capacity is substantial, with ample supply and lower prices. Industrially, acetone is almost exclusively produced via the cumene hydroperoxide process (in conjunction with phenol). As demand for phenol rises, coproduction of large quantities of acetone creates an imbalance, often leading to oversupply and driving acetone prices below those of both isopropyl alcohol and propylene. Consequently, developing catalytic hydrogenation of acetone to produce isopropyl alcohol holds significant potential for widespread application.

　　During the hydrogenation of acetone to produce isopropanol, a small amount of side reactions occurs, yielding by‑products such as water, diisopropyl ether, diacetone alcohol, and 4‑methylpentanol. These side products must be separated during the subsequent purification of isopropanol. Isopropanol purification typically employs a two‑column distillation sequence: in the first column, water and a minor fraction of unreacted acetone are removed from the overhead, while the bottoms stream contains isopropanol along with other high‑boiling by‑products; in the second column, the overhead product has a water content of less than 0.03 wt.%, and the remaining heavy components are collected in the bottoms. Because isopropanol forms a ternary azeotrope with water and acetone (8 wt.% acetone, 81 wt.% isopropanol, 11 wt.% water), conventional dehydration methods such as azeotropic distillation or extractive distillation are operationally complex, excessively costly, and cause significant environmental pollution. As a result, manufacturers often dispose of this stream as waste liquid, leading to reduced isopropanol yields and elevated production costs.

Production process

Typical Engineering Case Studies

Yancheng Supuer Chemical’s 8,000-ton-per-year isopropanol/acetone/water membrane unit