How Acetone Is Made: Biological and Industrial Paths

Acetone is a widely used solvent and chemical building block in industries such as pharmaceuticals, plastics, and cosmetics. Its production includes both industrial petrochemical processes and biological methods, each with distinct advantages in cost, efficiency, and sustainability.

Starting Materials

Acetone production begins with carefully selected raw materials. In industrial settings, hydrocarbons from crude oil and natural gas serve as primary feedstocks. Propylene, a three-carbon alkene, is a key starting compound due to its availability from petroleum refining and steam cracking. Its reactivity makes it ideal for acetone production, particularly in oxidation or hydration reactions. While petrochemical sources enable large-scale production, they also raise concerns about sustainability and environmental impact.

Beyond petrochemicals, alcohols such as isopropanol play a central role. Isopropanol, commonly produced through propylene hydration, serves as a direct precursor. Its conversion to acetone involves oxidation or dehydrogenation, offering controlled reaction conditions that minimize byproducts and improve yield. Its availability and low cost make it a preferred industrial starting material.

Biological sources also contribute to acetone production, particularly in fermentation-based methods. Certain bacteria, such as Clostridium acetobutylicum, metabolize carbohydrates into acetone under anaerobic conditions. Sugars derived from plant biomass, including glucose and starch, serve as feedstocks. While microbial pathways are not as dominant as petrochemical methods, advances in metabolic engineering and bioprocess optimization are improving their efficiency and commercial viability.

Industrial Methods

Industrial acetone production relies on well-established chemical processes that maximize efficiency and yield. The most widely used methods include the indirect hydration of propylene, dehydrogenation of isopropanol, and other petrochemical routes involving oxidation and catalytic reactions. Each has distinct advantages in cost, energy consumption, and byproduct formation.

Indirect Hydration of Propylene

One of the most common industrial methods is the cumene process. This begins with the alkylation of benzene using propylene to form cumene (isopropylbenzene). Cumene is then oxidized with molecular oxygen to produce cumene hydroperoxide, which undergoes acid-catalyzed cleavage to yield acetone and phenol.

The cumene process is widely favored because it simultaneously produces phenol, a valuable chemical used in resins, plastics, and pharmaceuticals. This integration reduces waste and improves cost efficiency. However, reliance on benzene and propylene, both fossil fuel-derived, presents environmental and resource concerns. Advances in catalysts and process optimization continue to enhance efficiency.

Dehydrogenation of Isopropanol

Another common method is the catalytic dehydrogenation of isopropanol. This process removes hydrogen from isopropanol in the presence of a metal catalyst, typically copper or zinc, at elevated temperatures (250°C–400°C). The reaction produces acetone and hydrogen gas, which can be captured for other industrial applications.

Dehydrogenation offers high selectivity for acetone, minimizing unwanted byproducts. It is a simpler alternative to the cumene process, as it does not require complex intermediates. However, its energy-intensive nature and the need for continuous catalyst regeneration affect operational costs. Research is focused on improving catalysts and reaction conditions to reduce energy consumption.

Other Petrochemical Routes

Alternative petrochemical methods exist for acetone production. One approach involves the direct oxidation of propylene using palladium or molybdenum-based catalysts, bypassing the need for cumene intermediates. However, challenges with catalyst stability and selectivity have limited its adoption.

Another route involves hydrocarbon oxidation, such as butane or propane, which can yield acetone as a secondary product. These processes typically rely on high-temperature oxidation reactions and are often integrated into broader petrochemical operations. However, due to lower selectivity and efficiency, they are less commonly used for dedicated acetone production.

Efforts to develop more sustainable petrochemical routes continue, with research focused on alternative catalysts, process intensification, and carbon capture technologies.

Microbial Pathways

Biological acetone production relies on anaerobic bacteria, particularly Clostridium acetobutylicum, which converts carbohydrates into acetone through fermentation. The acetone-butanol-ethanol (ABE) fermentation pathway was historically significant during World War I for producing acetone used in cordite, a smokeless propellant.

The process begins with glycolysis, where sugars break down into pyruvate, generating ATP and reducing equivalents. Under anaerobic conditions, C. acetobutylicum initially produces acetic and butyric acids. As fermentation progresses, these acids convert into solvents, including acetone. The key enzymatic step involves acetoacetate decarboxylase, which catalyzes acetoacetate’s conversion into acetone and carbon dioxide.

Advancements in metabolic engineering have improved microbial acetone production by enhancing pathway efficiency and expanding substrate utilization. Genetic modifications in C. acetobutylicum and related species aim to increase acetone selectivity while reducing unwanted byproducts. Synthetic biology has also introduced acetone biosynthesis into non-native hosts like Escherichia coli and yeast, allowing for more controlled fermentation and improved scalability. These engineered strains can use diverse feedstocks, including lignocellulosic biomass and industrial waste streams, making microbial acetone production more adaptable to sustainable bioprocessing.

Laboratory Approaches

Laboratory synthesis of acetone provides a controlled environment for studying its chemical properties and refining small-scale production techniques. A common method involves the oxidation of isopropanol using mild oxidizing agents such as chromic acid or copper catalysts. This reaction occurs under relatively low temperatures, making it practical for research settings. The choice of oxidant influences reaction efficiency and acetone purity, with catalytic systems preferred to minimize byproducts.

Another approach is the thermal decomposition of calcium acetate, historically used before industrial-scale production. When heated, calcium acetate undergoes pyrolysis, releasing acetone and forming calcium carbonate as a solid residue. Though simple and reagent-free, this method is less efficient and requires higher energy input, limiting its practical use. However, it remains a useful educational demonstration of organic decomposition reactions.