Patent Publication Number: US-2013253239-A1

Title: Heavy Alkylbenzene Production Through Oligomerization

Description:
FIELD OF THE INVENTION  
     The present invention relates to the production of heavy olefins, and in particular the production of heavy olefins from a feedstock having C5 and C6 paraffins. 
     BACKGROUND OF THE INVENTION  
     High molecular weight olefins, also known as heavy olefins, are useful in many applications. Heavy olefins generally include olefins having carbon chains in the range from 18 to 30 carbon atoms. These olefins are useful in the production of surfactants for specialty applications. One area of growth for these specialty surfactants is enhanced oil recovery processes. As oil prices increase the economics of recovering oil from formerly marginal fields becomes favorable. Methods of recovering this oil include adding chemicals to improve the flow of the difficult to recover oil, and surfactants enhance the ability to get the oil to flow. The surfactants used in enhanced oil recovery processes can be recovered with the oil and can go through the normal processing of oil from an oil field. 
     The current process for generating heavy olefins is from processing heavy, or high molecular weight, paraffins. The heavy paraffins are separated from the heavy cuts from a crude oil feedstock, and the paraffins are then dehydrogenated to generate the heavy olefins. However, this process can be costly, and heavy paraffins can have other high value purposes, but the relatively low molecular weight C5 and C6 paraffins are low value hydrocarbons and can be converted to higher value products. 
     It is desirable to use an inexpensive feedstock that can be converted to a more valuable product. Therefore, the conversion of lower value feeds containing C5 and C6 paraffins to higher value product streams comprising heavy olefins is desirable for forming a low cost material for use in enhanced oil recovery processes. 
     SUMMARY OF THE INVENTION  
     The present invention comprises integrating the production of heavy alkylbenzenes for the production of heavy surfactants. The heavy surfactants can be used in enhanced oil recovery processes. The process includes utilizing a feedstock having C4 to C6 olefins and oxygenated compounds. The feedstock is contacted with a liquid extractant to remove oxygenated compounds and generate a deoxygenated feedstock. The deoxygenated feedstock is passed to an oligomerization reactor, operated under chain growth conditions to generate a stream having heavy mono-olefins in the C15 to C36 range. The olefins are passed to an alkylation reactor, along with an aromatic stream under alkylation conditions to generate an alkylaromatic compound process stream. The alkylaromatic compound process stream is passed to a separation unit to separate the aromatic compound from the alkylaromatic compound and to generate an alkylaromatic product stream and an aromatic stream for recycle. 
     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  shows the process of generating heavy olefins for aromatic alkylation; and 
         FIG. 2  shows the process of generating heavy alkylaromatics from light olefins generated from a stream having olefins and oxygenates. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     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. With a shift in markets, and product specifications for gasoline and other products, there is an increase in lower value products such as pentane and hexane, as these hydrocarbon components are removed from commercial products. The process for increasing the value of low value hydrocarbons into higher value products is important and provides a means for producing high molecular weight alkylbenzenes from lower value hydrocarbons. The present invention allows for the production of large alkylbenzenes from renewable sources, and can utilize feedstocks that have an oxygenate component. 
     The present invention utilizes the use of a cheap feedstock comprising C4 to C6 paraffins and/or olefins to produce heavy alkylbenzenes, and in particular heavy linear alkylbenzenes. For enhanced oil recovery, linearity is not required as biodegradability is not an issue. Therefore, larger alkyl groups can be used with significant branching. The process of the present invention allows for flexibility in creating heavy alkylbenzenes for use in surfactant manufacture. This allows for tailoring surfactant design for different oil fields, due to the different makeup of petroleum in different oil fields. The process includes generating olefins having between 15 and 36 carbon atoms, with a preferred range in the C18 to C28 range for the olefins. 
     In one embodiment, the source of the feedstock is from a light cracked naphtha. The light cracked naphtha can be processed to remove light olefins, i.e. ethylene and propylene, before passing the light cracked naphtha to the present process. 
     The process of the present invention is shown in  FIG. 1 . The process includes passing a hydrocarbon feedstock  12  to an oligomerization reactor  20 , to generate a first stream  22  comprising heavy olefins in the C15 to C36 range. The feedstock  12  comprises olefins having from 4 to 6 carbon atoms. The first stream  22  is passed to a first separation unit  30  to generate a product stream  32  comprising heavy olefins in the C15 to C36 range, and a recycle stream  34  comprising lighter hydrocarbon compounds, including lighter olefins. 
     The recycle stream  34  can be passed to the oligomerization reactor  20 , or can be passed to a second separation unit  40  to generate a first recycle stream  42  and a second recycle stream  44 . The first recycle stream  42  comprises olefins in the C4 to C14 range and is passed to the oligomerization reactor  20 . The second recycle stream  44  has a reduced olefin content. The process can further include passing the second recycle stream  44  to a dehydrogenation reactor  50  to generate a dehydrogenation stream  52  having olefins. The dehydrogenation stream  52  can be passed to the oligomerization reactor for increasing the molecular weight of the olefins. 
     In one embodiment, the dehydrogenation stream  52  is passed to a selective hydrogenation reactor  60  to generate a dehydrogenation stream  62  having reduce diolefin and acetylene content. The subsequent stream  62  can be passed to the oligomerization reactor  20 . The choice of oligomerization catalyst is preferably one that is relatively sulfur tolerant to enable the process to run with a feedstock having some sulfur in the feedstock. 
     The dehydrogenation stream  52 , or the dehydrogenation stream with reduced diolefin and acetylene content  62  can be passed to a third separation unit  70  to generate a light stream  74  comprising C4 to C8 olefins, and a heavy stream  72  comprising C9 to C14 olefins. The heavy stream  72  is passed to a dimerization reactor  80  to generate a dimerization product stream  82 . The dimerization product stream  82  can be passed to an alkylation reactor  90 , where an aromatic stream  88  is passed to the reactor  90  to form an alkylaromatic process stream  92 . The light stream  74  is passed to the oligomerization reactor  20 . 
     In one embodiment the product stream  32  can be passed to the alkylation reactor  90 . An aromatic stream  88  is passed to the alkylation reactor, where the reactor  90  is operated as alkylation conditions to generate an alkylaromatic process stream  92  comprising alkylaromatic compounds having alkyl group chains in the C15 to C36 range. The aromatic compounds can be benzene or toluene or mixtures thereof. The product stream  92  can comprise alkylbenzenes, or alkyltoluenes. The alkylaromatic process stream  92  can be passed to a separation unit to form an alkylaromatic product stream, and an aromatic process stream. The aromatic process stream can be recycled to the alkylation reactor  90 . 
     One embodiment of the present invention is the integration of this invention into processes that generate hydrocarbons in the C4 to C6 range from a variety of sources. The process, as shown in  FIG. 2 , includes extracting and processing hydrocarbons generated from oxygenated compounds, such as from a Fischer-Tropsch liquid. A feedstock  8  comprising olefins in the C4 to C6 range and oxygenated compounds is passed to an extraction unit  10 . In the extraction unit  10 , the feedstock  8  is contacted with a liquid extractant  6  to generate a deoxygenated feedstock  12 . The deoxygenated feedstock  12  is passed to an oligomerization reactor  20  under chain growth conditions to provide for an oligomerization reactor process stream  22 . The oligomerization reactor process stream  22  comprises heavy mono-olefins in the C15 to C36 range. 
     The liquid extractant stream  14  leaving the extraction unit  10  can be regenerated and recycled to the extraction unit  10 . Extracted components can be passed to other processing units. The liquid extractant comprises at least one of alcohol and diol having 1 to 3 carbon atoms per molecule and a minor amount of water and is contacted with the olefin containing feedstock under extraction conditions. In one embodiment, the liquid extractant can comprise methanol and preferably contains less than 25 mass-percent water. 
     The oligomerization stream  22  is passed to a separation unit  30  to generate a heavy olefin product stream  32  and a second stream  34  having a reduced heavy olefin content. The heavy olefin product stream  32  is passed to an alkylation reactor  90  with a stoichiometric excess amount of an aromatic compound to alkylate the aromatic compound under alkylation conditions to generate an alkylation effluent stream  92  comprising alkylaromatics and benzene. The alkylation effluent stream  92  is passed to a separation unit  100  to generate a alkylaromatic product stream  102  and an aromatic stream  104 . At least a portion of the aromatic stream  104  can be passed to the alkylation reactor  90 . 
     The second stream  34  can be passed to a dehydrogenation reactor  50  to generate a third stream  52  comprising olefins. The third stream  52  is passed to the oligomerization reactor  20 , wherein the third stream comprises between 1 and 50 mass-percent of C5 and C6 mono-olefins. In one embodiment, the third stream is passed to a selective hydrogenation unit  60  to reduce the amount of diolefins and acetylenes to generate an olefin stream  62  having a reduced diolefin content. 
     The aromatic compounds for alkylation can include benzene and toluene, with benzene preferred. For the surfactants used in enhanced oil recovery, the aromatic compounds can include other aromatic compounds such as monoethyl benzene, or other aromatic compounds with mono-substitution of small alkyl groups. This process can be incorporated into existing processes to utilize materials that might be unacceptable for detergent grade linear alkylbenzenes. 
     Other configurations can be imagined for this process, and the invention is intended to cover other variations of the generation of heavy olefins. 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.