Method of conveying liquids

A process for hydrogenating aromatic compounds, wherein an aromatic compound or a solution of an aromatic compound is fed to the reactor by means of a displacement pump having physically separate forward-transport valves and a liquid-filled bidirectional flow line between displacement pump and forward-transport valves, where an auxiliary liquid which is the product of the hydrogenation of the aromatic compound is present in the bidirectional flow line and the auxiliary liquid has a melting point which is below the melting point of the aromatic compound or below the saturation temperature of the solution of the aromatic compound, the auxiliary liquid being the hydrogenated aromatic compound, the auxiliary liquid forming a liquid barrier which prevents spreading of the liquid to be conveyed into the bidirectional flow line, and the auxiliary liquid reducing formation of deposits in the pump system.

A process for preparing esters, wherein a carboxylic acid or a carboxylic acid derivative or a solution of a carboxylic acid or a carboxylic acid derivative is fed to the reactor by means of a displacement pump having physically separate forward-transport valves and a liquid-filled bidirectional flow line between displacement pump and forward- transport valves, where an auxiliary liquid which is the product of the ester preparation or an alcohol used as starting material is present in the bidirectional flow line and the auxiliary liquid has a melting point which is below the melting point of the carboxylic acid or the carboxylic acid derivative or below the saturation temperature of the solution of the carboxylic acid or the carboxylic acid derivative, the auxiliary liquid forming a liquid barrier which prevents spreading of the liquid to be conveyed into the bidirectional flow line, and the auxiliary liquid reducing formation of deposits in the pump system.

The use of a product formed by hydrogenation of an aromatic compound as auxiliary liquid for conveying aromatic compounds by means of a pump system which comprises a displacement pump having physically separate forward-transport valves and a liquid-filled bidirectional flow line between displacement pump and forward-transport valves.

The use of an alcohol or a carboxylic ester as auxiliary liquid for conveying a carboxylic acid or carboxylic acid derivative or a solution of a carboxylic acid or a carboxylic acid derivative by means of a pump system which comprises a displacement pump having physically separate forward-transport valves and a liquid-filled bidirectional flow line between displacement pump and forward-transport valves.