115 can be sent to the ether absorber 315 where it is contacted with the alcohol stream 317 to produce an ether lean crude olefin stream 320 and an ether rich alcohol stream 325. The ether lean crude olefin stream 320 can be sent to the oxygenate absorber 330 and contacted with the water stream 332 to produce an ether and oxygenate lean crude olefin stream 335 and an oxygenate rich water stream 340 before being sent to the crude olefin compressor 300.

The compressed crude olefin stream 305 may be sent directly to the dryer 310.

Alternatively, the compressed crude olefin stream 305 can be sent to an oxygenate absorber 330′ where it is contacted with a water stream 332′ to produce an oxygenate lean crude olefin stream 335′ and an oxygenate rich water stream 340′. The oxygenate lean crude olefin stream 335′ can be sent to the dryer 310 or to another treatment step.

The compressed crude olefin stream 305 (or the oxygenate lean crude olefin stream 335′) can be sent to a second compressor 345. The second compressed crude olefin stream (or the oxygenate lean crude olefin stream) 350 can be sent directly to the dryer 310 or to another treatment step.

The compressed crude olefin stream 305 (or the oxygenate lean crude olefin stream 335′ or the second compressed crude olefin stream 350) can be sent to a light olefin stripper 355 where it is stripped to produce an ether rich light crude olefin stream 360 and an ether lean heavy crude olefin stream 365. The ether rich light crude olefin stream 360 can be sent directly to the dryer 310 or to another treatment step.

The compressed crude olefin stream 305 (or the oxygenate lean crude olefin stream 335′, or the second compressed crude olefin stream 350, or the ether rich light crude olefin stream 360) can be sent to a caustic scrubber 370 where it is contacted with a caustic stream 372 to produce a carbon dioxide lean crude olefin stream 375 and a carbon dioxide rich spent caustic stream 380. The carbon dioxide lean crude olefin stream 375 can be sent directly to the dryer 310 or to another treatment step.

The compressed crude olefin stream 305 (or the oxygenate lean crude olefin stream 335′, or the second compressed crude olefin stream 350, or the ether rich light crude olefin stream 360, or the carbon dioxide lean crude olefin stream 375) can be sent to a chiller 385 where it is chilled to produce a chilled crude olefin stream 390 and water stream 395. The chilled crude olefin stream 390 can be sent directly to the dryer 310 or to another treatment step.

When the chiller 385 is present, the dryer 310 comprises a liquid dryer and a vapor dryer. In this case, there will be a dried crude olefin liquid stream and a dried crude olefin vapor stream.

The dried crude olefin stream is the concentrated olefin stream 125 which is sent to the olefin fractionation zone 130.

The unsaturated light gas recycle stream 160 from the oligomerization fractionation zone 155 can be sent to the crude olefin compressor 300, the dryer 310, or the second compressor 345.

FIG. 3 is an illustration of one embodiment of the olefin fractionation zone 130. The concentrated olefin stream 125 is sent to a light ends stripper column 400 where it is separated into a light ends stripper overhead stream 405 comprising hydrogen, methane, and carbon monoxide, and a light ends stripper bottom stream 410 comprising C₂olefins.

The light ends stripper overhead stream 405 is sent to the waste gas stream 135.

The light ends stripper bottom stream 410 is sent to a deethanizer column 415 where it is separated into a deethanizer overhead stream 420 comprising C₂olefins and paraffins and a deethanizer bottom stream 425 comprising C₃₊ olefins and paraffins.

The unsaturated light gas recycle stream 160 from the oligomerization fractionation zone 155 can be sent to the light ends stripper column 400 or the deethanizer column 415. It can be sent as a separate stream to the light ends stripper column 400 or the deethanizer column 415, or it can be combined with the column feed (i.e., concentrated olefin stream 125 or light ends stripper bottom stream 410).

The deethanizer overhead stream 420 is sent to a C₂splitter column 430 where it is separated into an ethylene stream 435 and an ethane stream 440. In some embodiments, a portion 422 of the deethanizer overhead stream 420 can bypass the C₂splitter column 430 and be combined with the fractionated olefin stream 140. The ethane stream 440 is sent to the waste gas stream 135.

The deethanizer bottom stream 425 is sent to a olefin rectifier column 445 where it is separated into a olefin rectifier overhead stream 450 comprising C₃olefins and paraffins and an olefin rectifier bottom stream 455 comprising C₄₊ olefins and paraffins.

The olefin rectifier overhead stream 450 is sent to a C₃splitter column 460 where it is separated into a propylene stream 465 and a C₃₊ stream 470 comprising propane, and in some cases dimethyl ether.

The propylene stream 465 forms part of the fractionated olefin stream 140 sent to the oligomerization reaction zone 145. In some embodiments, a portion 452 of the olefin rectifier overhead stream 450 can bypass the C₃splitter column 460 and be combined with the fractionated olefin stream 140.

The olefin rectifier bottom stream 455, the ether lean heavy crude olefin stream 365, and a hydrogen stream 477 are sent to a selective hydrogenation zone 475 where diolefins and acetylenes are selectively hydrogenated to olefins.

The saturated stream 480 is sent to a oxygenate removal zone 485 where trace oxygenates, such as dimethyl ether are removed forming a purified heavy olefin stream 490. The purified heavy olefin stream 490 forms part of the fractionated olefin stream 140 sent to the oligomerization reaction zone 145.

The C₃₊ stream 470 is sent to an ether absorber 495 with water stream 500. The purified propane stream 505 exits the top of the ether absorber 495 and an ether-rich water stream 510 exits the bottom.

The ether-rich water stream 510 is sent to column 515 where it is separated into an ether overhead stream 520 and a lean water stream 525. The lean water stream 525 is sent to the ether absorber 495. The ether overhead stream 520 is recycled to an upstream alcohol to olefins conversion zone (not shown).

Alternatively, the ether absorber 495 could be upstream of the olefin rectifier column 445. In this case, the deethanizer bottom stream 425 is sent to the ether absorber 495. The purified propane stream 505 is sent to the olefin rectifier column 445.

The fractionated olefin stream 140 comprises the ethylene stream 435, the propylene stream 465, optionally the purified heavy olefin stream 490, and optionally portion 422 of the deethanizer overhead stream 420 and/or portion 452 of the olefin rectifier overhead stream 450.

The waste stream 135 comprises the light ends stripper overhead stream 405, the ethane stream 440, the purified propane stream 505 or the C₃₊ stream 470, and optionally the olefin rectifier bottom stream 455.

FIG. 4 illustrates one embodiment of the oligomerization reaction zone 145, the oligomerization fractionation zone 155, the hydrogenation reaction zone 175, and the hydrogenation fractionation zone 185.

The fractionated olefin stream 140 from the olefin fractionation zone 130 is sent to the oligomerization reaction zone 145. The fractionated olefin stream 140 comprises C_2-6olefins. Alternatively, instead of combining the ethylene stream 435 and the propylene stream 465, and optionally the purified heavy olefin stream 490, and optionally portion 422 of the deethanizer overhead stream 420 and/or portion 452 of the olefin rectifier overhead stream 450, two (or more) separate streams could be sent to the oligomerization reaction zone 145.

As shown, the oligomerization reaction zone 145 includes first stage oligomerization reactor 600 and second stage oligomerization reactor 605. The effluent stream 610 from the first stage oligomerization reactor 600 is sent to the second stage oligomerization reactor 605.

The oligomerization effluent stream 150 from the second stage oligomerization reactor 605 comprising C₉₊ olefins and unreacted C_2-8olefins is sent to the oligomerization fractionation zone 155. The oligomerization effluent stream 150 is sent to the depropanizer column 615 where it is separated into a depropanizer overhead stream 620 comprising unconverted C_2-4olefins and a depropanizer bottom stream 625 comprising C₄₊ olefins.

The depropanizer bottom stream 625 is sent to the olefin splitter column 630 where it is separated into an olefin splitter overhead stream 635 comprising C_4-8olefins and an olefin splitter bottom stream 640 comprising C₉₊ olefins.

The olefin splitter overhead stream 635 is cooled in air cooler 645 and heat exchanger 650, and the condensed stream 655 is sent to the olefin splitter receiver 660 where it is separated into olefin splitter vapor stream 663 and olefin splitter liquid stream 665. The olefin splitter liquid stream 665 from the olefin splitter receiver 660 can be divided into multiple liquid streams, for example, a drag stream 670 and a recycle stream 165. In addition, a portion 680 of the olefin splitter liquid stream 665 can be refluxed to the olefin splitter column 630.

The depropanizer overhead stream 620 and the olefin splitter vapor stream 663 are combined to form the unsaturated light gas stream 160 and sent to the crude olefin compressor 300, the dryer 310, or the second compressor 345 in the olefin concentration zone 120 and/or the light ends stripper column 400 or the deethanizer column 415 in the olefin fractionation zone 130.

The recycle stream 165 can be recycled to the first stage oligomerization reactor 600 of the oligomerization reaction zone 145.

The olefin splitter bottom stream 640 comprising C₉₊ olefins and the drag stream 670 from the olefin splitter liquid stream 665 comprising C_4-8olefins are combined to form fractionated oligomerization stream 170 which is sent to the hydrogenation reactor 685 in the hydrogenation reaction zone 175 along with hydrogen stream 172 where the olefins are converted to paraffins.

The hydrogenation reactor effluent stream 180 is sent to the stripper column 700 in the hydrogenation fractionation zone 185 where it is separated into a saturated light gas stream 190 comprising hydrogen and C₁to C₄paraffins, a renewable liquid naphtha stream 195 comprising C_5-8paraffins, a stripper sidedraw stream 705 comprising C₉₊ paraffins, and a stripper bottom stream 710 comprising C₁₀₊ paraffins. Recycle stream 210 which is a portion of the stripper bottom stream 710 may be recycled to the first stage oligomerization reactor 600 of the oligomerization reaction zone 145.

The saturated light gas stream 190 can be used as a fuel gas. The renewable liquid naphtha stream 195 comprises paraffins and can be stabilized and used as gasoline blending stock, as a feedstock to steam cracking processes and the like, or pumped to a fired heater as fuel.

The stripper sidedraw stream 705 comprising C₉₊ paraffins and stripper bottom stream 710 comprising C₁₀₊ paraffins are sent to a jet fractionation column 715 where they are separated into a liquid aviation fuel stream 200, and a diesel blendstock stream 205. The liquid aviation fuel stream 200 comprises C_9-19paraffins, meeting ASTM D7566 Annex 5 specifications and may be blended into aviation fuel. The diesel blendstock stream 205 comprises C₁₉₊ paraffins and may be used as diesel blendstock. Those of skill in the art will understand that other separations could be performed.

Recycle stream 210 which is a portion of stripper bottom stream 710 comprising C₁₀₊ paraffins from the stripper column 700 can be recycled to the oligomerization reaction zone 145. It can be mixed with the mixed olefin stream 105 and the recycle stream 165 from the olefin splitter receiver 660.

Typical process conditions for various streams are shown in Table 1.

TABLE 1

Stream /
Temperature range
Pressure range

Equipment
° F.
° C.
psig
kPa(g)

115
40-130
5-55
15-100
100-700

305

200-600
1400-4100

125
40-120
5-50
200-600
1400-4100

400
Top: −180-10
Top: −120-−10
150-600
1000-4100

Bottom: 0-100
Bottom: −15-40

415
Top: −20-30
Top:-30-0
300-450
2100-3100

Bottom: 120-350
Bottom: 50-180

430
Top: −30-20
Top: −35-−5
250-350
1700-2400

Bottom: 0-50
Bottom: −15-10

445
Top: 90-150
Top: 30-65
220-350
1500-2400

Bottom: 200-450
Bottom: 90-235

460
Top: 80-130
Top: 25-55
150-350
1000-2400

Bottom: 100-160
Bottom: 35-70

495
80-110
25-45
250-350
1700-2400

515
250-330
120-165
40-80
250-550

600
300-550
150-290
500-1200
3400-8300

605
300-550
150-290
500-1200
3400-8300

615
Top: 120-250
Top: 50-120
100-200
700-1400

Bottom: 300-450
Bottom: 150-235

630
Top: 150-250
Top: 65-120
5-50
35-350

Bottom: 350-500
Bottom: 175-260

685
350-650
175-345
500-650
3400

700
Top: 250-350
Top: 120-175
50-150
350-1000

Bottom: 550-750
Bottom: 285-400

715
Top: 200-450
Top: 90-235
3 psia-15 psig
20 kPa(a)-100

Bottom: 550-750
Bottom: 285-400

kPa(g)

EXAMPLE

A comparison of a standard alcohol to renewable fuel process and one incorporating the unsaturated light gas stream recycle according to the present invention was made using a commercially available computer process modeling (UniSim Design Suite available from Honeywell).

The study was performed based on a methanol to jet process with 1,200,000 metric tonnes per year (1,200 kmta) of methanol feed with the process tuned to optimize the yield of SAF. The results are shown in Table 2. The study showed an improvement in the yield of SAF when the unsaturated light gas stream is recycled to the olefin concentration zone and the olefin fractionation zone includes the layout as described above.

TABLE 2

Present

Base process
invention

Methanol Capacity (99.85 wt %), KMTA
1,200

Operational Efficiency, hrs/yr
8,600

SAF, KMTA
435.4
453.3

Diesel Blendstock, KMTA
7.9
7.9

Renewable Naphtha, KMTA
16.9
15.6

MeOH % C Yield to SAF
82.1 wt-%
85.4 wt-%

Light Olefin % C Yield to SAF
88.6 wt-%
89.9 wt-%

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

A first embodiment of the invention is a process to produce fuels from light olefins comprising concentrating a crude olefin stream comprising C₂to C₆olefins to produce a concentrated crude olefin stream; fractionating the concentrated crude olefin stream in an olefin fractionation zone comprising an olefin fractionation column to produce an olefin stream comprising C₂to C₆olefins and a waste gas stream comprising C₁to C₃paraffins, hydrogen, and carbon monoxide; oligomerizing the olefin stream in an oligomerization reaction zone comprising an oligomerization reactor to produce an oligomerization effluent stream comprising C₂to C₂₂₊ olefins; fractionating the oligomerization effluent stream in an oligomerization fractionation zone comprising an oligomerization fractionation column into a fractionated oligomerized stream comprising C₉₊ olefins, a recycle olefin stream comprising C₄to C₈olefins, and an unsaturated light gas stream comprising C₂to C₃olefins and C₂to C₃paraffins; recycling at least a portion of the unsaturated light gas stream to the olefin concentration zone or the olefin fractionation zone; and fractionating the fractionated oligomerized stream to produce at least one fuel stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising; hydrogenating the fractionated oligomerized stream in the presence of hydrogen in a hydrogenation reaction zone comprising a hydrogenation reactor before fractionating the fractionated oligomerized stream to form a hydrogenated stream comprising C