Olefin Etherification Process by Refining Hydrocarbon Technologies

Application: New processing methods improve etherification of C4– C7 reactive olefins including light catalytic naphtha (LCN) with alcohol (e.g., methanol and ethanol). The processes, RHT-MixedEthers, RHT-MTBE, RHT-ETBE, RHT-TAME and RHT-TAEE, use unique concepts to achieve the maximum conversion without applying cumbersome catalyst in the column. The processing economics provide improvements over other available ether technologies currently available. The technology suite can be applied to ethyl tertiary butyl ether (ETBE) production in which wet ethanol can be used in place of dry ethanol. The drier can be eliminated, which is approximately half the cost for an etherification unit. The RHT ethers processes can provide the highest conversion with unique multiple equilibrium stages.

Description: The feed is water washed to remove basic compounds that are poisons for the resin catalyst of the etherification reaction. The C4 ethers—methyl tertiary butyl ether (MTBE)/ETBE), C5 – tertiary amyl methyl ether (TAME/ tertiary amyl ethyl ether (TAEE) and C6 /C7 ethers are made in this process separately. The reaction is difficult; heavier ethers conversion of the reactive olefins are equilibrium conversion of about 97% for MTBE and 70% for TAME and much lower for C6 /C7 ethers are expected.

Higher alcohols have similar effects (azeotrope hydrocarbon/alcohol relationship decreases when using methanol over ethanol). The equilibrium conversions and azeotrope effects for higher ethers are lower, as is expected. After the hydrocarbon feed is washed, it is mixed with alcohol with reactive olefin ratio control with alcohol.

The feed mixture is heated to reaction temperature (and mixed with recycle stream (for MTBE/ETBE only) and is sent to the first reactor (1), where equilibrium conversion is done in the presence of sulfonated resin catalyst, e.g. Amberlyst 15 or 35 or equivalent from other vendors.

Major vaporization is detrimental to this reaction. Vapor-phase reactive olefins are not available for reaction. Additionally at higher temperatures, there is slight thermal degradation of the catalyst occurs. The reactor effluent is sent to fractionator (debutanizer or depentanizer) to separate the ether and heavy hydrocarbons from C4 or C5 hydrocarbons, which are taken as overhead. Single or multiple draw offs are taken from the fractionation column. In the fractionation column, unreacted olefins (C4 or C5) are sent to the finishing reactor (5). This stream normally does not require alcohol, since azeotrope levels are available. But, some additional alcohol is added for the equilibrium-stage reaction. Depending on the liquid withdrawn (number of side draws), the conversion can be enhanced to a higher level than via other conventional or unconventional processes.

By installing multiple reactors, it is possible to extinct the olefins within the raffinate. The cost of side draws and reactors can achieve pay-off in 6 to 18 months by the higher catalyst cost as compared to other processes. This process could provide 97– 99.9% isobutene conversion in C4 feed (depending on the configuration) and 95 – 98+% of isoamylenes in C5 stream.

The ether product is taken from the bottom, cooled and sent to the storage. The raffinate is washed in extractor column (6) with and is sent to the OSBL. The water/alcohol mixture is sent to alcohol recovery column (7) where the alcohol is recovered and recycled as feed.

For ETBE and TAEE, ethanol dehydration is required for most of the processes, whereas for RHT process, wet ethanol can be used providing maximum conversions. If need be, the TBA specification can be met by optimum design with additional equipment providing high ETBE yield and conversion. Cost of ethanol dehydration is much more than the present configuration for the RHT wet-ethanol process.

The total capital cost /economics is lower with conventional catalyst usage, compared to other technologies, which use complicated structure, require installing a manway (cumbersome) and require frequently catalyst changes outs.

The RHT ether processes can provide maximum conversion as compared to other technologies with better economics. No complicated or proprietary internals for the column including single source expensive catalyst. Distillation is done at optimum conditions. Much lower steam consumption for alcohol recovery. For example, the C5 feed case requires less alcohol with RHT configuration (azeotropic alcohol is not required) and lowers lower steam consumption.

Licensor: Refining Hydrocarbon Technologies LLC.