Application: To process C4 streams from refineries to produce a stream with high butylenes content that is essentially butadiene-free, suitable for methyl tertiary butyl ether (MTBE) production, butene-1 production or alkylation feed.
Description: The patented C4 CDHydro process achieves selective hydrogenation of butadiene to n-butenes in a catalytic distillation column. 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 proprietary catalytic distillation structures.
The unique catalytic distillation column combines reaction and fractionation in a single unit operation. This constant pressure boiling system assures precise temperature control in the catalyst zone. Low reaction temperature and isothermal operation enhance selectivity and minimize yield losses to paraffins. Isomerization of butene-1 to butene-2 can be maximized to improve HF alkylate quality or minimized for increased butene-1 recovery.
Refinery C4 streams are combined with hydrogen in the catalytic column. Treated C4 products are 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 will react acidic sulfur compounds with diolefins to form heavy compounds which exit in the tower bottoms. The distillate product is essentially mercaptansulfur-free.
Economics: Capital costs are considerably lower than conventional hydrotreaters since the single column design eliminates costs associated with fixed-bed systems. Additionally, the ability to remove acidic sulfur compounds eliminates the need for sweetening. The C4 CDHydro process would typically be installed in a debutanizer, either as a retrofit or in a new column.
Process advantages include:
• Low operating pressure
• Low operating cost
• High product yield (low paraffin make)
• No polymer recycle across catalyst
• No sweetening required
• Essentially mercaptan sulfur-free distillate product
• Flexible butene-1/butene-2 ratio
• Retrofit to existing C4 columns
• All carbon steel construction
• Isomerization option
• No hydrogen compressor.