Abstract: For the continuous manufacture of n-butyraldehyde by selective hydrogenation of crotonaldehyde, the hydrogenation is conducted in the liquid phase in the presence of a palladium-aluminum oxide supported catalyst containing the palladium in the outer layer of the supporting grain of a thickness of 0.05-0.2 mm. The palladium content of this catalyst is 0.1-0.6% by weight. The aluminum oxide support, with a specific pore volume of 0.4-0.6 cm.sup.3 /g, has 40-60% of its pores of a diameter of >0.5 nm and an internal surface area of 130-160 m.sup.2 /g. The hydrogenation is conducted under absolute pressures of 5-50 bar and at temperatures of 20.degree.-100.degree. C. The resultant n-butyraldehyde is of a high purity without interfering by-products.

Abstract: Silica gel esterification catalysts which are mechanically stable and are highly abrasion free, particularly suitable for the esterification of dimethyl terephthalate, are prepared by impregnating silica gel in solutions of aluminum, titanium, zinc and tin compounds, separating the excess solutions and drying at elevated temperatures. The catalysts are further improved by treatment with a gaseous mixture of methanol and water.

Abstract: The process of recovering methanolic mother liquor obtained by the esterification of terephthalic acid with methanol, where the terephthalic acid may be unprepurified, is improved by adjusting to a specific gravity of about 0.85 - 0.98 by addition of water and/or methanol distillate, a mother liquor containing esterification water and dissolved solids at a concentration of about 1.0 to 6.0 percent by weight and cooling the mother liquor from a temperature of about 65.degree. - 85.degree. C to a temperature of about 10.degree. - 30.degree. C to separate the solids and remove the separated solids. The separated solids may be recycled into the esterification reaction and the unseparated solids may be recycled for oxidation to terephthalic acid following distillation to remove the methanol.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor.

Abstract: Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor.