A method for preparing methyl methacrylate from methacrolein and methanol. The method comprises contacting in a tubular reactor having at least four zones a mixture comprising methacrolein, methanol, oxygen and a base with a catalyst bed of heterogeneous catalyst comprising a support and a noble metal, wherein reaction zones comprising catalyst beds alternate with mixing zones not comprising catalyst beds.

A method for preparing methyl methacrylate from methacrolein and methanol; said method comprising contacting in a reactor a mixture comprising methacrolein, methanol and oxygen with a catalyst bed of heterogeneous catalyst comprising a support and a noble metal, wherein mass transfer rate of oxygen in hour.sup.1 divided by space-time yield in moles methyl methacrylate/kg.Math.catalyst hour in the catalyst bed is at least 20.

A method for preparing methyl methacrylate from methacrolein and methanol; said method comprising contacting in a reactor a mixture comprising methacrolein, methanol and oxygen with a catalyst bed of heterogeneous catalyst comprising a support and a noble metal, wherein mass transfer rate of oxygen in hour.sup.1 divided by space-time yield in moles methyl methacrylate/kg.Math.catalyst hour in the catalyst bed is at least 20.

A method for preparing methyl methacrylate from methacrolein and methanol; said method comprising contacting in a reactor a mixture comprising methacrolein, methanol and oxygen with a heterogeneous catalyst comprising a support and a noble metal, wherein pH at the reactor outlet is from 3 to 6.7.

A method for preparing methyl methacrylate from methacrolein and methanol; said method comprising contacting in a reactor a mixture comprising methacrolein, methanol and oxygen with a heterogeneous catalyst comprising a support and a noble metal, wherein pH at the reactor outlet is from 3 to 6.7.

The invention relates to a process for preparing a carboxylic ester by reacting an aldehyde in the presence of an aluminum alkoxide, wherein the aluminum alkoxide is obtained either by reacting an aluminum hydride with an aldehyde or by reacting a different aluminum alkoxide with a carboxylic ester.

The invention relates to a process for preparing a carboxylic ester by reacting an aldehyde in the presence of an aluminum alkoxide, wherein the aluminum alkoxide is obtained either by reacting an aluminum hydride with an aldehyde or by reacting a different aluminum alkoxide with a carboxylic ester.

The invention relates to a process for preparing a carboxylic ester by reacting an aldehyde in the presence of an aluminum alkoxide, wherein the aluminum alkoxide is obtained either by reacting an aluminum hydride with an aldehyde or by reacting a different aluminum alkoxide with a carboxylic ester.

A method can prepare a carboxylic ester. The method includes reacting an aldehyde in the presence of an aluminium alkoxide applied to a support material.

A method can prepare a carboxylic ester. The method includes reacting an aldehyde in the presence of an aluminium alkoxide applied to a support material.