Figure 5 plots a typical time course of the liquid-phase hydrogenation of crotonaldehyde on Au/APTS-SBA-15. Similar curves were obtained on the other two catalysts. Typically, the amount of crotyl alcohol increases first, reaches a maximum, and then gradually decreases in accordance with the known behavior of continuous reactions. The simultaneous presence of butyraldehyde and crotyl alcohol at the initial stage may indicate that the hydrogenation of C=C and C=O bonds occurs through parallel reactions.

Acute exposure to butyraldehyde vapors causes inflammation of the alveolar and bronchial regions and death due to pulmonary edema. Severe irritation of eyes and nose noted. Sperm morphology was abnormal in rats drinking relatively high concentrations of butyraldehyde in their drinking water for 50 days. Rodents exposed to low concentrations of butyraldehyde recover rapidly after cessation of exposure.

Butyraldehyde has low acute toxicity. Exposure to large doses may have a temporary narcotic effect. Exposure to low concentrations of butyraldehyde vapor can irritate the eyes, nose and throat. This compound has an unpleasant odor. An impurity (butyric acid) may be present, making the smell even worse. Health effects attributable to long-term exposure to low doses of butyraldehyde vapor have not been described. Dermatitis may develop after prolonged and repeated exposure to solutions containing butyraldehyde.

The hydroformylation reaction, discovered by Otto Roelen in 1938, is used in the chemical industry, mainly for the production of n-butyraldehyde from propylene.