Production of high purity butene-1 from an n-butane feedstock

A process for producing butene-1 and butadiene from a feedstock containing n-butane which comprises the steps:

• (a) dehydrogenating a feedstock containing n-butane in the presence of a chromia-alumina catalyst to produce a reaction product containing butene-1, butene-2, butadiene, and unreacted material;
• (b) distilling the reaction product from step (a) in a distillation column separating butene-2 from butadiene and butene-1, the butene-2, being removed as a bottoms fraction and the butene-1 and butadiene as an overheads fraction;
• (c) treating the bottoms fraction from the distillation column in a deoiler thereby removing butene-2 as an overhead fraction and any C.sub.5 plus material as a bottoms fraction;
• (d) separating the overhead fraction from the distillation column by contacting with a solvent selective for butadiene into a high purity butadiene product and a raffinate stream containing butene-1, isobutane, isobutene and a small portion of residual butadiene;
• (e) passing the raffinate stream from the butadiene extraction through a hydrogenation zone thereby hydrogenating residual butadiene to form butene-1 and butene-2;
• (f) fractionating the reaction product from the hydrogenation in step (e) generating an overhead containing butene-1, isobutane and isobutene;
• (g) contacting the isobutene and butene-1 in the overhead from step (f) with methanol in a methyl tertiary butyl ether unit thereby forming methyl tertiary butyl ether;
• (h) fractionating the reaction product from the methyl tertiary butyl ether unit separating methyl tertiary butyl ether from the reaction product;
• and
• (i) fractionating the overhead fraction containing butene-1 and isobutane thereby producing an overhead containing isobutane for recycle to the dehydrogenation zone and a high purity butene-1 as a bottoms fraction.

A process for producing butene-1 from a feedstock containing n-butane and other C.sub.2 to C.sub.6 hydrocarbons which comprises the steps:

• (a) dehydrogenating a feedstock containing n-butane in the presence of a chromia-alumina catalyst to produce reaction product containing butene-1, butene-2, butadiene, and unreacted materials;
• (b) hydrogenating the butadiene product produced in the dehydrogenation step to produce additional butene-1 and butene-2;
• (c) fractionating the reaction product from the butadiene hydrogenation step to produce an overhead stream comprising butene-1, butene-2, and isobutene and a bottoms fraction containing C.sub.5 plus hydrocarbons;
• (d) contacting the overhead stream from the fractionation of step (c) with a solvent selective for extracting butene-1 from butene-2 and saturated hydrocarbons;
• (e) separating the butene-2 from the saturates by fractionation;
• (f) isomerizing the butene-2 from the butene-1 extraction by contact with an isomerization catalyst and recycling the isomerization reaction product to the feed to the deoiler in step (c);
• (g) contacting the butene-1 from the extraction in step (d) with methanol to convert the isobutylene to methyl tertiary butyl ether thereby generating a reaction product containing said ether and unreacted butene-1;
• (h) fractionating the methyl tertiary butyl ether from the reaction product in step (g) to produce a bottoms comprising methyl tertiary butyl ether and an overhead fraction comprising butene-1;
• and then
• (i) recovering said butene-1 and methyl tertiary butyl ether.