Application: To achieve selective hydrogenation of butadiene to n-butenes in a catalytic distillation column.
Description: The C4 CDHydro catalytic distillation technology processes C4 streams from refineries or steam crackers within an methyl tertiary butyl ether (MTBE)/ethyl tertiary butyl ether (ETBE) debutanizer to produce a raffinate with a high butylenes content that is essentially butadiene free. After methanol recovery, the treated C4 raffinate can be used for butene-1 production or alkylation feed.
Selective hydrogenation increases butenes available for alkylation or isomerization, reduces acid consumption in alkylation units, and greatly improves the quality of HF alkylate. The process uses commercially available catalyst in its proprietary catalytic distillation structures (CDModules).
The C4 stream is combined with hydrogen in the MTBE/ETBE debutanizer. Treated C4 raffinate is taken overhead. The washing action of the reflux minimizes oligomer formation, flushing heavy compounds from the catalyst and promoting long catalyst life. Excess hydrogen and lights are vented from the overhead drum. The catalyst is sulfur tolerant.
Feed sulfur compounds react with diolefins to form heavy compounds that exit in the tower bottoms with the MTBE/ETBE product. The distillate product is essentually mercaptan-sulfur free.
Process advantages include:
• Low capital cost
• Low catalyst requirements
• Low operating cost
• High product yield (low saturation to paraffins)
• No polymer recycle across catalyst
• Use of reaction heat
• Sulfur tolerant catalyst
• Essentially mercaptan-sulfur-free distillate product
• Flexible butene-1/butene-2 ratio
• Retrofit to existing C4 columns
• All carbon steel construction.
Economics: Capital costs are considerably lower than conventional hydrotreaters since the single column design eliminates costs associated with fixed-bed systems. The C4 CDHydro process would typically be installed in a conventional or catalytic MTBE/ETBE debutanizer, either as a retrofit or in a new column.