About Benzene. Benzene (a.k.a. Benzol) is an essential organic compound classified within the aromatic hydrocarbon group. Specifically, it stands as the fundamental unit of these compounds, characterized by a singular aromatic ring structure. Benzene itself manifests as a colorless, volatile, and flammable liquid, exhibiting insolubility in water but solubility in a wide range of organic compounds. It is considered a thermally stable material but very chemically reactive, serving as a source for several chemical productions, mainly by reactions of substitution, oxidation, and addition. Its presence in nature is scarce, predominantly occurring as minute traces within crude oil and coal reserves. Historical accounts trace the isolation of benzene back to 1825, followed by the commencement of large-scale production in 1849, which experienced remarkable growth in the 1950s, driven by the escalating demand for polymers. Undoubtedly, benzene holds profound significance as a versatile and fundamental building block for a vast array of organic compounds, primarily of aromatic nature.

Nowadays, benzene, toluene, and xylene – the so-called BTX aromatics – are primarily produced from petroleum. In this context, Benzene is produced on a commercial scale mainly by reforming and separation, thermal or catalytic dealkylation of toluene, and disproportionate. The catalytic reforming process involves high-pressure units with fixed-bed reactors, utilizing base-metal catalysts that are regenerated in specific intervals. In the dealkylation of toluene, the two main thermal routes employed are HDA (Hydrogenation-Dealkylation) and THD (Thermal Hydrodealkylation). Catalysts commonly used in the catalytic route consist of supported chromium or molybdenum oxides and platinum or platinum oxides on silica or alumina supports. The two main catalytic processes are the Detol and the Hydeal ones. Finally, the Disproportionate route, also referred to as transalkylation, involves the conversion of two toluene molecules into one molecule of benzene and one molecule of mixed-xylene isomers. This process route is considered economically feasible only when there is a toluene excess and a high demand for benzene.

Regarding different process routes, Benzene can also be obtained from pyrolysis gasoline, which is derived from the steam cracking of heavy naphthas or light hydrocarbons, such as propane or butane. Pyrolysis gasoline is a source responsible for a significant part of worldwide benzene production and typically contains over 60% BTX content, with benzene content reaching up to 50%. Alternatively, other routes have been used, although in minor proportions, such as the Benzene recovery from light oils obtained through the carbonization or coking of coal.

Benzene Handling. Due to its inherent flammability, volatility, and toxicity, the handling, storage, and transportation of Benzene necessitate stringent adherence to regulatory guidelines. The appropriate storage options for Benzene include steel drums or tanks to safely contain the material. When it comes to shipping, various modes of transportation such as rail tank cars, trucks, barges, and tankers are employed. Given the hazardous nature of Benzene, the transfer of this substance from one vessel to another is executed within closed systems to minimize risks. During such transfers, it is crucial to ground metal tanks and storage containers as a precautionary measure. Moreover, workers that handle benzene must be protected from inhalation of fumes and skin contact. Smaller quantities of Benzene are routinely transported using steel or glass containers.

Benzene Production. Until the 1930s, commercial Benzene was primarily produced from coal; more specifically, it was recovered by extraction and distillation of byproduct gas and aromatic liquid from the pyrolysis of coal. Since then, as new catalytic processes were developed, petroleum became the main source for this chemical and related aromatics. Raw materials and the respective production processes employed in the manufacturing of Benzene are listed below.

Benzene Uses. The uses and applications of Benzene may vary according to its specification. The main forms of Benzene are crude or BTX cut fraction (14-17 wt%, reformate and 44-48 wt%, pygas); nitration grade (no evidence of acidity, H2S or SO2); thiophene-free (min 99% purity); 99 mole%; and 99.94 mole%.

The main uses of Benzene are in the production of ethylbenzene, cumene, and cyclohexane. All such chemicals are important intermediates, employed respectively for the production of styrene (monomer of several polymeric and copolymeric products), phenol and acetone (used in phenolic resins) and adipic acid (raw material for nylons).