Catalytic hydrogenation process hazard analysis

Most of the hydrogenation reactions are exothermic, and most of them are carried out at high temperatures. The hydrogen and most of the materials used have the danger of ignition and explosion, and some of the materials, products or intermediate products are toxic and corrosive. In case of leakage, reactor blockage and other failures, there is a great risk of fire and explosion.

Inherent danger

The inherent danger refers to the hazardous and harmful characteristics of the raw materials, products and intermediate products in the hydrogenation reaction itself, including the following.

Fire hazard

① Hydrogen gas: It can become explosive mixture when mixed with air, and can cause combustion when it meets with spark and high heat. When hydrogen is used or stored indoors, when there is a leak, the hydrogen gas will rise and stay on the roof, which will not be easily discharged naturally and will cause an explosion when it meets a spark.

② Raw materials and products: The raw materials and products of hydrogenation reaction are mostly flammable and combustible substances. For example: benzene, naphthalene and other aromatic hydrocarbons; cyclopentadiene, cyclopentene and other unsaturated hydrocarbons; nitrobenzene, ethylenedinitrile and other nitro compounds or nitrogen-containing hydrocarbons; carbon monoxide, butyraldehyde, methanol and other oxygen-containing compounds as well as petrochemical distillates, depressurized distillates and other oil products.

③ Catalysts: Some catalysts used in hydrogenation reactions, such as Raney nickel hydrogenation catalysts, are flammable solids that can spontaneously combust.

④During the hydrogenation reaction: the by-products produced such as hydrogen sulfide and ammonia are mostly combustible.

Explosion hazard

In some hydrogenation processes such as carbon monoxide hydrogenation to methanol, the raw material carbon monoxide is also a flammable and explosive gas, and the product methanol is a Class AB flammable liquid, and the methanol is gaseous at the operating temperature. 

Such as benzene hydrogenation of cyclohexane, phenol hydrogenation of cyclohexanol, butyraldehyde gas phase hydrogenation of butanol and other processes in the raw materials, products at room temperature for liquid, but in the operating conditions for the gas state, when there is a leak leads to an explosion. In addition, such as nitrobenzene liquid phase hydrogenation to produce aniline and other processes, the reaction temperature and pressure is relatively low, the reaction is a gas-liquid two-phase reaction, the explosion risk mainly from hydrogen.

① Physical explosion: hydrogenation process is mostly gas-liquid phase or gas-phase reaction, in the whole hydrogenation process, the device is basically under high pressure conditions. Under the operating conditions, hydrogen corrosion equipment produces hydrogen embrittlement phenomenon and reduces the strength of the equipment. If improperly operated or in case of an accident, a physical explosion occurs.

② Chemical explosion: hydrogen explosion limit is 4.1%-74.2% in hydrogenation process, when there is leakage; or air or oxygen is mixed in the device; explosion hazard easily occurs.

Poisoning danger hazards

The toxicity of different raw materials and products in hydrogenation reaction varies greatly, as follows.

① Unsaturated hydrocarbons and distillate oils: such as cyclopentadiene, acetylene, often, depressurized distillate oils, etc. are non-toxic.

②Aromatic hydrocarbons: such as phenol, toluene, etc. are low-to-moderate toxic substances, some of which are corrosive.

③Nitrogenous compounds: such as nitrobenzene, aniline, etc. have strong toxicity.

Corrosion and other hazards

Hydrogenation reactions are corrosive as follows.

①Hydrogen: Hydrogenation reaction is mostly carried out under high temperature and pressure, under such conditions, hydrogen can corrode the equipment steel and appear steel brittle phenomenon.

②Byproducts: In petrochemical industry, hydrogenation refining is mostly accompanied by desulfurization and denitrogenation process, and the by-products such as hydrogen sulfide and ammonia gas are corrosive.

③Other: For some hydrogenation process, the raw material or product itself is corrosive, such as phenol.