Abstract: A process for desulfurization and, if necessary, for denitrification of hydrocarbon fractions is characterized in that:

Abstract: A process for production, from an olefinic C4 fraction, on the one hand, of high-purity isobutene and, on the other hand, of propylene by metathesis is described.

Abstract: A direct-injection spark-ignition four-stroke internal-combustion engine includes a combustion chamber defined by a piston, a cylinder with a cylinder head, an intake pipe associated with an intake valve, an exhaust pipe with which an exhaust valve cooperates, and a first ignition device situated close to intake valve. The engine further includes a fuel injection element situated close to the first ignition device, with the intake pipe, the fuel injection element, and the first ignition device being situated in the same half of the cylinder head. The fuel injection element may be placed below the first ignition device. A second ignition device may be positioned in the half of the cylinder head containing the exhaust valve.