A continuous process for the preparation of propylene oxide, comprising a start-up stage and normal run stage, wherein the normal run stage comprises (i) continuously providing a liquid feed stream comprising propene, hydrogen peroxide, acetonitrile, a formate salt, water and optionally propane, wherein in the liquid feed stream, the molar amount of the formate salt relative to the molar amount of hydrogen peroxide at a given point of time during the normal run stage is a.sup.N(Fo/H.sub.2O.sub.2); (ii) continuously passing the liquid feed stream provided in (i) into an epoxidation zone comprising a catalyst comprising a titanium zeolite having framework type MWW, and subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, obtaining a reaction mixture comprising propylene oxide, acetonitrile, water, the formate salt, optionally propene, and optionally propane; (iii) continuously removing an effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, acetonitrile, water, at least a portion of the formate salt, optionally propene, and optionally propane; wherein the normal run stage is characterized in an average rate of change of a.sup.N(Fo/H.sub.2O.sub.2) of less than 0 h.sup.1.

A continuous process for the preparation of propylene oxide, comprising a start-up stage and normal run stage, wherein the normal run stage comprises (i) continuously providing a liquid feed stream comprising propene, hydrogen peroxide, acetonitrile, a formate salt, water and optionally propane, wherein in the liquid feed stream, the molar amount of the formate salt relative to the molar amount of hydrogen peroxide at a given point of time during the normal run stage is a.sup.N(Fo/H.sub.2O.sub.2); (ii) continuously passing the liquid feed stream provided in (i) into an epoxidation zone comprising a catalyst comprising a titanium zeolite having framework type MWW, and subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, obtaining a reaction mixture comprising propylene oxide, acetonitrile, water, the formate salt, optionally propene, and optionally propane; (iii) continuously removing an effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, acetonitrile, water, at least a portion of the formate salt, optionally propene, and optionally propane; wherein the normal run stage is characterized in an average rate of change of a.sup.N(Fo/H.sub.2O.sub.2) of less than 0 h.sup.1.

In a process for the epoxidation of propene, comprising the steps: reacting propene with hydrogen peroxide in the presence of a titanium silicalite catalyst and a methanol solvent; separating non-reacted propene and propene oxide from the resulting reaction mixture to provide a solvent mixture comprising methanol and water in a combined amount of at least 90% by weight; and feeding this solvent mixture as a feed stream to a continuously operated methanol distillation column at a feed point in the middle section of said column to provide an overhead product comprising at least 90% by weight methanol and a bottoms product comprising at least 90% by weight water; the addition of a liquid defoamer, having a solubility in the feed stream of less than 10 mg/kg at 25 C. and a surface tension at the liquid air interface of less than 22 mN/m at 20 C., at or above the feed point in an amount exceeding the solubility of the liquid defoamer in the feed stream suppresses foam formation in the methanol distillation column.

In a process for the epoxidation of propene, comprising the steps: reacting propene with hydrogen peroxide in the presence of a titanium silicalite catalyst and a methanol solvent; separating non-reacted propene and propene oxide from the resulting reaction mixture to provide a solvent mixture comprising methanol and water in a combined amount of at least 90% by weight; and feeding this solvent mixture as a feed stream to a continuously operated methanol distillation column at a feed point in the middle section of said column to provide an overhead product comprising at least 90% by weight methanol and a bottoms product comprising at least 90% by weight water; the addition of a liquid defoamer, having a solubility in the feed stream of less than 10 mg/kg at 25 C. and a surface tension at the liquid air interface of less than 22 mN/m at 20 C., at or above the feed point in an amount exceeding the solubility of the liquid defoamer in the feed stream suppresses foam formation in the methanol distillation column.

A catalytic system containing a titanium zeolite of structure type MWW optionally containing zinc and containing at least one of an inorganic potassium salt and an organic potassium salt is provided. The catalyst system is useful in the preparation of propylene oxide.

A catalytic system containing a titanium zeolite of structure type MWW optionally containing zinc and containing at least one of an inorganic potassium salt and an organic potassium salt is provided. The catalyst system is useful in the preparation of propylene oxide.

In a process for the epoxidation of propene, comprising the steps: reacting propene with hydrogen peroxide in the presence of a titanium silicalite catalyst and a methanol solvent; separating non-reacted propene and propene oxide from the resulting reaction mixture to provide a solvent mixture comprising methanol and water in a combined amount of at least 90% by weight; and feeding this solvent mixture as a feed stream to a continuously operated methanol distillation column at a feed point in the middle section of said column to provide an overhead product comprising at least 90% by weight methanol and a bottoms product comprising at least 90% by weight water; the addition of a liquid defoamer, having a solubility in the feed stream of less than 10 mg/kg at 25 C. and a surface tension at the liquid air interface of less than 22 mN/m at 20 C., at or above the feed point in an amount exceeding the solubility of the liquid defoamer in the feed stream suppresses foam formation in the methanol distillation column.

In a process for the epoxidation of propene, comprising the steps: reacting propene with hydrogen peroxide in the presence of a titanium silicalite catalyst and a methanol solvent; separating non-reacted propene and propene oxide from the resulting reaction mixture to provide a solvent mixture comprising methanol and water in a combined amount of at least 90% by weight; and feeding this solvent mixture as a feed stream to a continuously operated methanol distillation column at a feed point in the middle section of said column to provide an overhead product comprising at least 90% by weight methanol and a bottoms product comprising at least 90% by weight water; the addition of a liquid defoamer, having a solubility in the feed stream of less than 10 mg/kg at 25 C. and a surface tension at the liquid air interface of less than 22 mN/m at 20 C., at or above the feed point in an amount exceeding the solubility of the liquid defoamer in the feed stream suppresses foam formation in the methanol distillation column.

A moderator management process that can be employed during an epoxidation process is disclosed. The disclosed moderator management process provides optimum catalyst performance without having to rely on a trial and error or using elaborate equations as disclosed in the prior art. In the disclosed moderator management process, the optimum halide-containing moderator concentrations can be determined by maintaining Ea from 30 kJ/mol to 300 kJ/mol, wherein Ea is the difference in activation energies between the reaction to remove halide from the surface of the epoxidation catalyst and the reaction to deposit halide on the surface of the epoxidation catalyst.

A moderator management process that can be employed during an epoxidation process is disclosed. The disclosed moderator management process provides optimum catalyst performance without having to rely on a trial and error or using elaborate equations as disclosed in the prior art. In the disclosed moderator management process, the optimum halide-containing moderator concentrations can be determined by maintaining Ea from 30 kJ/mol to 300 kJ/mol, wherein Ea is the difference in activation energies between the reaction to remove halide from the surface of the epoxidation catalyst and the reaction to deposit halide on the surface of the epoxidation catalyst.