Abstract:
A process for the production of olefin sulfonates is presented. The process comprising generating olefins from normal alkanes through a dehydrogenation unit to produce a mixture of alkanes and alkenes. The mixture is sulfonated to react the olefins and generate olefin sulfonates. The olefin sulfonates are separated from the normal alkanes to produce a product stream, with the normal alkanes recycled to the dehydrogenation unit.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to the process of generating alkylsulfonates. The production of alkylsulfonates are for the production of surfactants. 
     BACKGROUND OF THE INVENTION 
     Detergent range linear paraffins and linear olefins are typically produced using kerosene as a feedstock. While desirable carbon number chains vary, typical carbon number ranges for products are C10-C14, though at times it is desirable to produce heavier products, up to C18-C20 carbon number. Surfactants have other uses, and can require heavier hydrocarbon components. Generally, surfactants require both a water soluble characteristic and an oil soluble characteristic. These mixed properties enable surfactants to facilitate lowering of interfacial tension and the mixing and flowing of viscous liquids. 
     Surfactants have been used in chemical flooding systems for enhanced oil recovery processes. For enhanced oil recovery, higher molecular weight surfactants, or longer chained molecules are desirable. However, the production of surfactants is an expensive process. With increasing oil prices, the production has become more favorable, but producing surfactants through cheaper processes can improve the use of surfactants in enhanced oil recovery even at lower oil prices. Therefore, it is beneficial to seek improved and cheaper methods of producing surfactants. 
     SUMMARY OF THE INVENTION 
     The present invention provides for a cheaper process of generating heavy olefin sulfonates. Heavy olefin sulfonates are useful for surfactants in enhanced oil recovery processes. The process includes providing a heavy normal alkane stream in the C14 to C30 range. The heavy normal alkane stream is passed to a dehydrogenation reactor to generate an intermediate olefin stream. The intermediate olefin stream is degassed in a light gas separation unit, and passed to a selective hydrogenation unit to remove diolefins, and to generate a second intermediate olefin stream. The intermediate olefin stream does not separate out the unreacted paraffins, but passes the stream to a sulfonation unit, where the olefins are converted to olefin sulfonates, and generates an intermediate product stream. The olefin sulfonates are passed to an extraction unit where the olefin sulfonates are recovered in a product stream, and the n-alkanes are separated into a recycle stream. The n-alkanes are passed back to the dehydrogenation unit for further conversion to olefins. 
     In a preferred embodiment, the feedstream is passed to a fractionation unit for generating multiple feedstreams having a smaller range of carbon numbers. Each feedstream generated by the fractionation unit is passed to a parallel processing system, as described above, for converting the n-alkanes to olefin sulfonates. 
     Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a design for the process of sulfonating heavy olefins; and 
         FIG. 2  is an alternate design for the process of sulfonating heavy olefins 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The process of generating olefins from paraffins generally includes passing a process stream having the paraffins to a dehydrogenation unit to generate a process stream having olefins, and then separating the olefins from the paraffins through separation processes such as distillation. Distillation requires heating the process stream with olefins to a temperature sufficient to boil the components within the process stream. When the process stream comprises heavy hydrocarbons, the temperatures are greater to vaporize the hydrocarbons and lead to many problems in the process. Among the problems include thermal cracking of the hydrocarbons, which can significantly reduce yields and render the process uneconomical. 
     Alkylsulfonates, or olefin sulfonates, are useful as detergents, and are increasingly useful as surfactants in enhanced oil recovery processes. The olefin sulfonates for an enhanced oil recovery process preferably have long chained normal alkyl groups. However, cost is important, as the material is pumped into the ground and requires substantial quantities. 
     The present invention generates olefin sulfonates through a new process, can increase yields and saves energy and costs in the recovery of the product in a product stream. The process is a low cost method to manufacture olefin sulfonates from low cost paraffins. In particular, low cost Fischer-Tropsch paraffins in the C14 to C30 range are advantageous for this process. The process involves passing a feedstream of normal alkanes to a paraffin dehydrogenation unit, thereby generating a first effluent stream comprising olefins and light gases, as well as paraffins. The first effluent stream is passed to a separator to generate a light gas stream, and a second effluent stream comprising olefins and paraffins. The second effluent stream is liquid, and is passed to a selective hydrogenation unit to hydrogenate diolefins and generate an olefin process stream. The olefin process stream is passed to a sulfonation unit to sulfonate the olefins in the olefin process stream, thereby generating a sulfonate process stream. The sulfonate process stream is passed to an extraction unit to generate a first extract process stream comprising olefin sulfonates, and a second extract process stream comprising paraffins. 
     The process of sulfonating the stream comprising olefins and n-alkanes followed by separation is more economical than the normal process of separating the olefins from n-alkanes before sulfonation. This saves on the more expensive process of separating olefins from n-alkanes with little effect on the sulfonation process as the n-alkanes are relatively inert in the sulfonation process. 
     The second extract process stream can be passed back to the dehydrogenation unit for further conversion of unreacted paraffins. The second extract stream may contain small amounts of sulfates in the process stream from the extraction process. Due to the possibility of deleterious effects of sulfur compounds on the dehydrogenation catalyst, the second extract process stream can be passed to a sulfur removal unit to generate a substantially sulfur free second extract process stream, which is then passed to the dehydrogenation unit. 
     The dehydrogenation process can generate a small amount of aromatics. The aromatics can be removed by passing the olefin process stream to an aromatics extraction unit to generate the olefin process stream without aromatics. An aromatics process stream generate can be passed to other processing units. The olefin process stream with the aromatics removed is then passed to the sulfonation unit for converting olefins to olefin sulfonates. 
     The extraction process can be a liquid phase separation process. The sulfonate process stream can be combined with a water stream to form an aqueous phase and a non-aqueous phase. The aqueous phase will comprising the olefin sulfonates, which can be subsequently separated from the water through known processes. The non-aqueous phase will comprise mostly paraffins. The non-aqueous phase can be passed to a drying unit to remove residual water and to generate a dried paraffins stream. The dried paraffins stream is then passed to the dehydrogenation unit. The drying unit can comprise a molecular sieve, over which the non-aqueous phase is passed. The molecular sieve removes the water, and leaves a dried paraffin stream. 
     The hydrocarbon feedstream can be produced from several sources, with economics being a driving factor. In one embodiment, the feedstream comprising normal paraffins is generated from a heavy paraffin feedstock comprising heavy paraffins in the C14 to C30 range. The paraffin feedstock is passed to and adsorption separation unit to generate the feedstream comprising normal paraffins in the C14 to C30 range, and a raffinate stream comprising non-normal paraffins and other hydrocarbons. The feedstream is then passed to the dehydrogenation unit. 
     In a preferred embodiment, the paraffins are the C14 to C28 range. The dehydrogenation unit runs more efficiently when the paraffins have a more narrow distribution. The process can further include fractionating the normal paraffins feed stream to generate two or more effluent streams. The effluent streams from the fractionation unit are passed to the dehydrogenation unit. For molecular weights in the C14 to C28 range, the fractionation unit is normally operated as a vacuum fractionation unit, and operated at temperatures and pressures to provide for desired separations. 
     In one embodiment, the fractionation unit can comprise multiple fractionation towers, and the unit can generate multiple streams, or a more narrow range of n-paraffins can be chosen from the feed with a fractionation unit separating the desired carbon number range from the feedstream. 
     In one embodiment, the process is operated to select a narrower range of normal alkanes. The process includes passing the feedstream of normal alkanes in the C15 to C28 range to a fractionation unit. The fractionation unit is designed and operated to generate two or more streams of n-alkanes. The fractionation can be designed for a first stream comprising C15 to C18 n-alkanes, a second stream comprising C19 to C22 n-alkanes, a third stream comprising C20 to C24 n-alkanes, and a fourth stream comprising C24 to C28 n-alkanes. 
     The process can pass the individual streams to separate dehydrogenation reactors, or the first stream to a first dehydrogenation reactor, the second stream is passed to a second dehydrogenation reactor, the third stream is passed to a third dehydrogenation reactor, and the fourth stream is passed to a fourth dehydrogenation reactor, wherein each dehydrogenation reactor is operated to optimize the dehydrogenation process for the different feedstreams, with each dehydrogenation reactor effluent subsequently combined and processed through the light gas separation unit, the selective hydrogenation unit to remove diolefins, and the sulfonation unit. The dehydrogenation reactors are operated at different conditions, in particular different inlet temperatures, due to the different rates of conversion of the n-paraffins at different inlet temperatures. 
     The combined streams are then passed to a light gas separation unit to separate light gases from the olefin and n-paraffin process stream. The olefin and n-paraffin process stream is passed to a selective hydrogenation unit to selectively hydrogenate diolefins and acetylenes to generate an intermediate olefin stream. The intermediate olefin stream is passed to the sulfonation unit to form an olefin sulfonates process stream. The olefin sulfonate process stream is passed to an extraction unit to separation the olefin sulfonates from the unreacted n-alkanes, and the n-alkanes are passed back to the fractionation unit. 
     The process can include passing each n-alkane stream recovered from each extraction unit to a sulfur removal unit to generate a substantially sulfur free n-alkane stream. The substantially sulfur free n-alkane stream is passed back to the fractionation unit for converting the unreacted n-alkanes into the olefin sulfonates. 
     An alternative includes processing each stream in a rotation sequence, wherein the first stream is processed the dehydrogenation unit with the dehydrogenation unit effluent stream passed to the light gas separation unit, the selective hydrogenation unit, and the sulfonation unit. The second stream is then processed in the dehydrogenation unit with the effluent stream passed to the subsequent units in the overall process. The third stream and fourth stream can follow. 
     Another alternative depends upon the end use, and upon the selection of process stream or streams for generating an olefin sulfonate. As an example, if the plant only desires larger olefins, such as C24 to C28 olefins, the fractionation unit can be set to recycle or redirect the lighter n-alkanes to other process units, with the C24 to C28 n-alkanes passed to the dehydrogenation unit, and subsequent process units for forming the olefin sulfonates. 
     The choice and design of the number of dehydrogenation units can depend on the size of the process streams and the size of storage for intermittently storing unprocessed n-alkane streams. In one embodiment, the process can comprise multiple sets for processing each stream generated by the fractionation unit. The n-alkanes recovered in each stream therefore will only need to be passed back to the dehydrogenation unit, rather than back to the fractionation unit. When the conversion rate is low, the process can be more economical for processing each n-alkane stream with a narrow carbon range through a separate process stream wherein each process stream comprises the dehydrogenation unit, the light gas separation unit, the selective hydrogenation unit, the sulfonation unit, and the olefin sulfonate extraction unit. 
     The process is shown in  FIG. 1  where an n-alkane feed  8 , comprising C15 to C28 n-alkanes is passed to a fractionation unit  10 . The fractionation unit  10  is operated to generate multiple process streams, a first stream  12 , a second stream  14 , a third stream  16  and a fourth stream  18 . Each stream will follow a separate, but parallel path through parallel sets of equipment and process units. The first stream  12  is passed to a first dehydrogenation reactor  20  to generate a dehydrogenation reactor effluent stream  22 . The dehydrogenation reactor effluent  22  is passed to a light gas separation unit  30  to separate hydrogen and other light gases in an overhead stream  32 , and generates a second effluent stream  34 . The second effluent stream  34  is passed to a selective hydrogenation unit  40  and generates an intermediate olefin process stream  42 . The intermediate olefin process stream  42  is passed to a sulfonation unit  50  to generate a sulfonate process stream  52 . The sulfonate process stream  52  is passed to an extraction unit  60  to generate a first process stream comprising olefin sulfonates  62  and a second extract stream comprising n-alkanes  64 . The second extract stream  64  is passed to the dehydrogenation unit  20  for further processing of the unreacted paraffins. The process can include passing the second extract stream  64  through a sulfur removal unit prior to passing the second extract stream  64  to the dehydrogenation unit  20 . 
     Another embodiment of the process is shown in  FIG. 2  where the n-alkane feed is split into three fractions. The process comprises passing C15 to C28 n-alkanes to a fractionation unit  10 . The fractionation unit  10  is operated to generate three process streams, a first stream  12 , a second stream  14 , and a third stream  16 . The first stream  12  is passed to a first dehydrogenation reactor  20   a  to generate a first dehydrogenation reactor effluent stream  22 . The second stream is passed to a second dehydrogenation reactor  20   b  to generate a second dehydrogenation reactor effluent stream  24 . The third stream is passed to a third dehydrogenation reactor  20   c  to generate a third dehydrogenation reactor effluent stream  26 . The dehydrogenation reactor effluents  22 ,  24  and  26  are passed to a light gas separation unit  30  to separate hydrogen and other light gases in an overhead stream  32 , and generates a second effluent stream  34 . The second effluent stream  34  is passed to a selective hydrogenation unit  40  and generates an intermediate olefin process stream  42 . The intermediate olefin process stream  42  is passed to a sulfonation unit  50  to generate a sulfonate process stream  52 . The sulfonate process stream  52  is passed to an extraction unit  60  to generate a first process stream comprising olefin sulfonates  62  and a second extract stream comprising n-alkanes  64 . The second extract stream  64  is passed to the fractionation unit  10  for further processing of the unreacted paraffins. 
     The dehydrogenation process has different operating conditions for different paraffins. The conversion is generally in the range from 10 to 15 percent of the n-alkanes converted to olefins. The dehydrogenation process includes operation under a pressure between 150 kPa and 400 kPa, with a preferred pressure between 200 kPa and 300 kPa, and a general operating pressure around 240 kPa. The LHSV is in the range from 10 to 40 hr-1, with a preferred range from 20 to 30 hr-1. The process is operated under a hydrogen rich atmosphere, with a hydrogen to hydrocarbon mole ratio (H2/HC) between 2 and 10, and preferably between 5 and 7. The operational temperature of the process is a function of average molecular weight, with the temperature declining for increasing average molecular weight. The operational temperature is the feed inlet temperature. For a feedstream in the C10 to C13 range, the range is 450° C. to 470° C., with a preferred operational inlet temperature of 460° C. For a feedstream in the C15 to C18 range, the range is 440° C. to 460° C., with a preferred operational inlet temperature of 450° C. For a feedstream in the C19 to C22 range, the range is 425° C. to 445° C., with a preferred operational inlet temperature of 435° C. For a feedstream in the C20 to C24 range, the range is 420° C. to 440° C., with a preferred operational inlet temperature of 430° C. For a feedstream in the C24 to C28 range, the range is 400° C. to 425° C., with a preferred operational inlet temperature of 414° C. 
     Other configurations can be imagined for this process, and the invention is intended to cover other variations of the processing of the n-alkane feedstream. While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.