Hydro Cracking

  • Published on
    24-Jul-2015

  • View
    1.002

  • Download
    0

Embed Size (px)

Transcript

<p>CHNG I: TNG QUAN V QU TRNH HYDROCRACKING 1.1. Gi thiu Hydrocracking l qu trnh b gy mch C - C vi s tham gia ca hydro v xc tc, sn phm cui cng thu c l cc hydrocacbon no. l s kt hp ca qu trnh cracking xc tc cc hp cht ban u v hydro ha cc hp cht khng no va c to ra. 1.2. Mc ch Cng nh cc qu trnh ch bin du m khc nh reforming xc tc, cracking, isomer ha, th qu trnh hydrocracing cng nhm ch bin cc phn ct ca du m thnh cc sn phm nhin liu, cc loi du bi trn v cc sn phm trung gian cho cng nghip tng hp ha du. 1.3. Nguyn liu Nguyn liu cho qu trnh hydrocracking rt a dng, n l mt phn on kh rng, t xng nng ti du nng, cc nguyn liu u c nhit si cao hn so vi nguyn liu trong cracking xc tc. l: Phn on xng sn xut kh ha lng. Phn on kerosene-diesel v distilat chn khng sn xut xng, nhin liu phn lc v nhin liu diesel. Sn phm cn ca cc qu trnh ch bin du.</p> <p>1</p> <p>Du c hm lng lu hunh cao, mazut, gudron sn xut distilat hoc nhin liu t l vi hm lng lu hunh thp. 1.4. Sn phm c im ca sn phm ca qu trnh Hydrocracking so vi qu trnh Cracking thng thng l t olefin, aromatc v nhiu iso parafin. V d nh xng i t hydrocracking c ch s octan trung bnh kh, n nh cao. Phn on Kerozen c smoke point cao v phn on Gasoil th c ch s cetan kh cao. Ngoi ra, qu trnh Hydrocracking cn to ra phn on C4 vi nhiu iso butan, y l phn on rt hu ch cho qu trnh Alkyl ha trong nhmy lc du. Qu trnh ny cn tn dng c cc phn nng nhiu Aromatic chuyn ho thnh xng, kerozen v gasoil. L cc sn phm trng nh xng, kerosene, diesel t dng nguyn liu l phn nng.</p> <p>2</p> <p>CHNG II: HA HC CA QU TRNH HYDROCRACKING 2.1. Nhit ng hc Phn ng cracking v hydro ha: y l hai phn ng chnh din ra trong qu trnh hydrocracking. Hai phn ng mong mun ny c tc dng tng h ln nhau trong cng mt qu trnh. Phn ng cracking s to ra v cung cp olefin cho qu trnh hydro ho v ngc li, phn ng hydro ho s cung cp nhit lng cho qu trnh cracking. Tuy nhin, nhit ta ra t qu trnh hydro ha cao hn so vi nhit ta ra t qu trnh cracking, v th khi xem xt ton b qu trnh th c th xem hydrocracking l phn ng ta nhit. Cc phn ng chnh trong qu trnh hydrocracking nh: Hydro ha cc hp cht d nguyn t. Hydro ng phn ha alkane. Hydro ha vng thm. Hydro phn vng naphtene. Ct mch cc paraffin v mch nhnh alkyl. Ct vng naphten. Bo ha hydro cc lin kt khng no mi c to ra. Bn cnh cc phn ng chnh, vi tc dng ca nhit v cht xc tc, mt s phn ng khc s din ra song song ng thi nh:</p> <p>3</p> <p>Hydro deankyl ho aromatic. Phn ng HDS, HDN. Phn ng cc ho. Phn ng hydrocracking l phn ng ta nhit v t c s thay i th tch. Nhng n c tin hnh di p sut hydro rt cao vi mc ch l no ha cc sn phm, trnh s ngng t to thnh cc lm gim hot tnh xc tc. Hiu ng nhit trung bnh ca cc phn ng c trnh by bng di y. Bng 1: Hiu ng nhit ca phn ng Cc loi phn ng 1. Hydrocrracking - Parafin: RH + H2 R1H + R2H - Naphten:R</p> <p>Nhit phn ng (trung bnh) Kcal/mol Kcal/H2 11-14 0.49-0.625</p> <p>10-12 + H2 + RH</p> <p>0.45-0.54</p> <p>R</p> <p>Hydrocacbon thm: + H2 RH 10-11 0.45-0.49</p> <p>2. Hydro ha - Olefin: CnH2n + H2 CnH2n+2 RHa + H2 naphten a. Dn xut cha S:-</p> <p>27-31 48-52</p> <p>1.2-1.4 0.71-0.77</p> <p>Mercaptan:4</p> <p>12.5-17</p> <p>R-SH + H2 RH + H2S-</p> <p>Thioete: Thiofen:R</p> <p>13.5-17</p> <p>R-S-R + H2 RH + H2S-</p> <p>16.25-16.7 +H2 H2S + RH Desunfua: 14</p> <p>S</p> <p>-</p> <p>R-S-S-R + H2 RH + H2S + RH b. Cc hp cht cha Nit: R-NH2 + H2 RH + NH3 19</p> <p>T s liu ca bng trn ta thy, cc phn ng bo ha hydro thng l cc phn ng ta nhit nhiu hn so vi phn ng hydrocracking. Hiu ng nhit ca qu trnh vo khong 0.55 - 1 kcal/lit H2. Cc phn ng bo ha lin kt thng l cc phn ng ta nhit nhiu hn. Do l phn ng ta nhit, v vy qu trnh thch hp nhit thp. Nhng nu nhit qu thp th tc phn ng s gim, do nhit c xem nh l tc nhn duy tr hot tnh xc tc. Thng thng i vi ch hot ng nh th nhit ca qu trnh dao ng t 6500F - 8500F.</p> <p>5</p> <p>2.2. ng hc v tc phn ng S bin i c trng trong qu trnh phn ng va mang tnh ni tip, va mang tnh song song. Th t phn ng (tc phn ng) hon ton ph thuc vo bn cht ca hp cht vi nhng mc nng lng lin kt khc nhau, ph thuc vo hot ng ca xc tc c s dng v iu kin tin hnh qu trnh hydrocracking. Hiu sut cc i ca cc sn phm c ch c m bo bi s chn la xc tc ph hp, bng cch hn ch su bin i ca nguyn liu v tun hon phn nguyn liu cha b bin i. t c hiu qu bin i cao, xc tc ca qu trnh hydrocracking cn c kh nng thc y mnh qu trnh cracking c th m bo bin i c cc cu t kh chuyn ha nht ca nguyn liu. ng thi xc tc phi c kh nng izomer ho cao tng t l gia izo-parafin v nparafin trong sn phm cui. Hn na xc tc hydrocracking cn phi c hot tnh hydro ha nht nh no ha cc phn t nh to ra trong qu trnh phn ng. Do vy gia chc nng cracking v chc nng hydro ha nn chn mt iu kin ti u nht phn ng cracking khng nn qu mnh, qu nhanh so vi s hydro ha cc sn phm ca cracking. Nu khng ngay trn b mt ca xc tc s xy ra s ct mch tip cc olefin to kh hay ngng t cc bm trn xc tc.</p> <p>6</p> <p>CHNG III: XC TC CHO QU TRNH V VAI TR CA CHT MANG 3.1. Xc tc cho qu trinh hydrocracking i nt v lich s pht trin: u tin xc tc c s dng l W/t st. Xc tc ny c hot tnh tt v s dng c hiu qu trong qu trnh hydro ha xng. Song c nhc im l rt nhanh b mt hot tnh khi c mt cc cht nit. Nm 1937 hng Esso ch to xc tc sunfit W/t st c b sung HF. Nm 1939 nhn c xng c kh nng chng kich n cao, chu u dung xc tc hai chc nng: Hydro ha v cracking (Fe/t st c b sung HF). Cho n ngy nay xc tc Ni,Pt,Pd mang trn aluminosilicat v nh hnh hoc oxyt nhm, zeolit l nhng xc tc rt ph bin. Cht xc tc s dng c chc nng acid c to ra bi thnh phn aluminosilicat, cn chc nng hydro ha c to ra bi cc kim loi. Cc trnh hydrocracking thng thng l tinh th alumino silicat c mang cc kim loi t him. y l xc tc lng kim loi t him thng c s dng ch yu l Pt, Pd, Ni-Mo, Ni-W. Cc kim loi ny lm xc tc cho c hai qu trnh hydro ha v dehydro ha. Cc cht mang thng s dng l cc zeolite tinh th v alumino silacat v nh hnh. Xc tc cho qu trnh hydrocracking rt d b u c bi cc tc nhn c hi trong nguyn liu, do phi x l nguyn liu trc khi a vo qu trnh ny. Nu trong nguyn liu c mt lng ln hydrosunfua th xc tc s b u c bi lu hunh, ammoniac s lm gim chc nng acid ca xc tc, chc nng hydro ha ca kim loi s b bin mt bi cc kim loai bn c trong nguyn liu. Ngoi ra, nguyn liu cn phi c loi tr hi m, v y l tc nhn ph hy cu trc tinh th ca cht xc tc nhit cao.7</p> <p>Sau thi gian lm vic xc tc c th mt hot tnh v cc c th hnh thnh ngay khi c mt hydro, do cn phi ti sinh xc tc sau mt chu k lm vic. Khi xc tc trng thi c nh th thng xy ra s ngng t cc v qu nhit cc b do vic to dng qua lp xc tc. Cn xc tc tng si c nhiu u im hn v mt truyn nhit v truyn khi. 3.2. Xc tc lng chc Nh bit xc tc cho qu trnh hydrocracking l h xc tc hai chc nng vi thnh phn xc tc bao gm cc tm hot ng axit, tm hot ng kim loi v cht xc tin.</p> <p>Tm hot ng acid: Ngy nay xc tc cho qu trinh thng s dng l zeolite: zeolite alumina</p> <p>silica, zeolite Y. Hu ht cc cng ngh gn y u x dng zeolit Y vi nhiu c tnh ni tri. Zeolit Y: Trong cu trc zeolit dng Y, c hnh bt din ct c sp xp theo tinh th kim cng. Mi nt mng ca zeolit Y u l cc bt din ct v mi bt din ct li lin kt vi 4 bt din ct khc 6 mt cnh thng qua lin kt cu oxy. S mt 6 cnh ca bt din ct l 10, do vy lun tn ti 4 mt, 6 cnh cn trng ca mi bt din ct trong zeolite Y. S t din SiO4 hoc AlO4 trong mi t bo c bn ca zeolite Y l 192 v s nguyn t oxy l 348 nguyn t. Cng thc ha hc ca mt t bo c s loi zeolite ny nh sau: Na56[(AlO2)86.(SiO2)136].260H2O T s Si/Al ca zeolit Y l 2. Vi ng knh ca zeolit Y l 12,7Ao</p> <p>8</p> <p>Hnh1 : Zeolite y Tm hot ng kim loi: Chc nng kim loi c th nghim i vi cc kim loi nh Pt, Pd, NiMo, Ni-W. Kim loi, oxit kim loi, sunfua kim loi, hoc mt s kt hp ca nhng hp cht ny c th cung cp chc nng kim loi ca cht xc tc. Yu cu quan trng cho chc nng kim loi l n phi kch hot cc hydro v l cht xc tc kh v hydro ha phn ng. Cc chc nng kim loi c s dng ph bin nht cho cc cht xc tc hydrocracking l s kt hp gia nhm kim loi VI A (Mo, W) v nhm VIII A (Co, Ni) sunfua. u im chnh ca s kt hp ny ca sulfua kim loi l n chu c lu hunh, tuy nhin, n ch hot ng mc va phi so vi Pd hoc Pt. S kt hp thuc nhm VI A v Nhm VIII A kim loi sulfide c c im ni bt hn trong phn ng hydrocracking. Nhm VIII A kim loi tr xc tc tng tc h tr vi nhm kim loi sunfua VI A to ra mt s gia tng ng k vo cc hot ng.</p> <p>9</p> <p>Trong phn ng hydrocracking c hai phn ng chnh: phn ng cracking v phn ng hydro ha-dehydro ha. Phn ng cracking din ra trn tm acid trong khi phn ng hydro-dehydro ha din ra trn tm kim loi. Do xc tc hydrocracking phi l xc tc lng chc. Trong cc xc tc hydrocraking hin nay, phn ng hydrocracking c h tr bi cht mang c tnh acid nh alumina, alumina silicat v nh hnh, zeolite hoc hn hp ca cc cht mang ny. Hot tnh cracking ca ba cht mang ny c sp xp theo th t gim tnh acid: Zeolite &gt; Alumina silicat v nh hnh &gt; alumina chn lc phn on naptha cng theo th t ging nh trn. Do vi s quan trng ln v chn lc naptha ti u, ngi ta s s dng mt xc tc cha 80% thnh phn l zeolite. Ngoi ra tng hiu sut distillate th ta phi gim thnh phn zeolite xung. Vi cc xc tc chn lc distillate, thnh phn zeolite chim thnh phn rt thp, t 0-10% v n c trn ln vi cht mang chnh c thnh phn l alumina silicat v nh hnh v alumina. Ly 1 v d, xc tc thng mi alumina silicat v nh hnh c s dng cho qu trnh hydrocracking nghim ngt ti u sn phm distillate trung bnh hoc chuyn ha thnh du nhn. Bng 2: Cc cht mang thng s dng trong qu trnh hydrocracking Cht mang ng dng Tnh acid Cao Rt cao</p> <p>Alumino silicat v nh Xc tc hydrocracking c chn lc phn hnh Zeolite ct Xc tc hydrocracking c bn cao</p> <p>Phn ng hydro-dehydro ha xy ra trn b mt cc kim loi qu nh platinum (Pt) hoc palladium (Pd) hoc cc kim loi thng thng khc nh vonfram (W) hoc molybdenum (Mo) vi cht xc tin l nickel (Ni). Xc tc10</p> <p>hydrocracking c chc nng hydro ha tt s gip cho cht lng distillate tt hn, t kh sinh ra v n nh hn. Tuy nhin, chc nng cracking v hydro ha phi c cn bng v t l gia tm acid v tm kim loi phi c iu chnh sao cho c hot tnh v chn lc ti u. Hot tnh v chn lc l hai trong bn tiu ch nh gi phn ng hydrocracking: - hot ha c tnh bng nhit cn thit t c sn phm mong mun. - n nh, c tnh bng tc gia nhit gi c qu trnh chuyn ha mong mun. - chn lc sn phm, c tnh bng kh nng xc tc cho phn ng to sn phm chnh. - Cht lng sn phm, c tnh bng cc ch tiu cht lng nh nh git, chiu cao ngn la khng khi v ch s cetane. Mt xc tc hydrocracking c xem l hiu qu khi c s chuyn phn t cc nhanh gia tm kim loi v tm acid trnh cc phn ng khng mong mun xy ra. Vic chuyn phn t cc nhanh xy ra khi tm kim loi nm rt gn tm acid.</p> <p>11</p> <p>Bng 3: nh hng ca t l gia tm kim loi/tm acid vi phn ng hydrocracking.</p> <p>Cc xc tc kim loi qu nh platinum hoc palladium th c hot tnh cho phn ng hydro ha ln hn xc tc Ni/W v Ni/Mo. Mt s khc bit ln gia xc tc kim loi qu v xc tc kim loi thng thng l cc xc tc kim loi qu cn phi gi trng thi kh duy tr hot tnh xc tc v kim loi qu b u c khi c lu hunh trong . iu ny tri ngc vi cc xc tc kim loi thng v chng c hot ha dng mui sulfide. nng sulfur cao, xc tc kim loi thng thng khng b hao ht khi hot ng.</p> <p>12</p> <p>Hin nay, hu ht cc quy trnh hydrocracking u s dng xc tc kim loi thng thng ch c mt s t nh my vn s dng xc tc kim loi qu v s dng xc tc kim loi qu c hot tnh cao nht v sn phm naptha c cht lng tt hn. tng thch vi xc tc kim loi qu, thit b hydrocracking c thit k c bit vn hnh trong mi trng khng c hp cht lu hunh hu c hoc H2S. Khng nhng phi loi b hu ht lu hunh trong nguyn liu m cn phi loi ht H2S trong kh tun hon. Tuy nhin k c khi thit b hydrocracking c thit k hot ng trong mi trng khng c acid, xc tc kim loi qu vn c th b u c bi cc hp cht lu hunh. iu ny dn n sn phm s c nng lu hunh cao hoc c nhiu H2S trong kh tun hon. Nu s dng xc tc kim loi thng thng, s nh hng ny s mc thp nht. Khi ta xc nh c vn th thit b c vn hnh bnh thng m khng gy hi cho xc tc kim loi thng. Tuy nhin, nu xc tc s dng l kim loi qu th s bin i nh c th u c cc tm kim loi v lm gim tui th xc tc. S hp ph lu hunh ca platinium c th l thun nghch hoc bt thun nghch. i khi, lu hunh c th c gii hp khi cho kh hydro nhit cao sc qua. Tuy nhin khi lu hunh lin kt cht vi kim loi, s hp ph l bt thun nghch. iu ny dn n gim hot tnh v tui th xc tc. Vic s dng xc tc kim loi thng c hot ha dng sulfide gip cho xc tc bn hn khi hot ng vi nguyn liu nng hn, hm lng lu hunh cao hn.</p> <p>13</p> <p>Bng 4: Cc tm hot ng kim loi thng dng trong qu trnh hydrocracking Kim loi Co-Mo Ni-Mo Ni-W Pd, Pt ng dng chnh HDS HDN, hydrocracking HDN, hydrocracking Hydrocracking Kh nng hydro ha Trung bnh Cao Rt cao Cao nht</p> <p>Pd v Pt b u c bi lu hunh v ch c th s dng trong mi trng c nng H2S thp. Trong thit b hydrocracking xc tc tng c nh, xc tc ngoi kh nng gip cc phn ng mong mun xy ra th n cn phi c din tch b mt ln v bn vt l tt chng li s va p do tc ng ca dng nhin liu chy tc cao v do trng lng bn thn xc tc . Mt tng xc tc c th cha n vi trm tn xc tc. Phn ng ha hc xy ra cc l xp nh thng thy trn b mt xc tc. thu c phn on gas oils nng v gas oil nh th bn knh l xp xc tc</p> <p>14</p> <p>phi t 75A0 n 85A0. Vi bn knh l xp t 150A0 n 250A0 ta s thu c phn on cn residue.</p> <p>CHNG IV: C CH PHN NG CA QU TRNH HYDROCRACKING XC TC V CC YU T NH HNG 4.1. C ch phn ng hydrocracking4.1.1. Chc</p> <p>nng ca xc tc</p> <p>Tm kim loi: To olefin hoc cyclo olefin qua phn ng dehydro ha Tnh Acid: To ion carbenium t olefin nh qu trnh chuyn proton. B gy ion carbenium Chuyn proton vo ion carbenium to thnh olefin Tm kim loi: No ha olefin nh phn ng hydro ha.15</p> <p>4.1.2. C ch phn ng trn xc tc S to thnh olefin: Phn ng din ra trn tm kim loi hot ng, to thnh olefin v kh hydro. Paraffin sau khi c isomer ha trn tm acid thnh i-paraffin, n s c hp ph ln tm kim loi. Ti y s din ra phn ng dehydro ha to thnh olefin.CH 3 R C H C H CH CH3</p> <p>R</p> <p>CH 2</p> <p>H2 C</p> <p>H C</p> <p>MetalCH3</p> <p>CH3 S to thnh ion tertiary carbenium:</p> <p>Phn ng din ra trn tm acid. Tm acid c 2 loi l acid Bronsted v acid Lewis. Olefin s tham gia phn ng vi tm acid ca xc tc to thnh ion carbenium.CH 3 R C H C H CH CH3 CH3</p> <p>Acid</p> <p>R</p> <p>H2 C</p> <p>H2 C</p> <p>C</p> <p>CH3</p> <p> Phn ng isomer ha v cracking: Cc ion carbenium thng thng c isomer ha thnh cc ion tertiary carbenium bn hn. Phn ng cracking ion carbenium din ra theo quy tc (ct mch v tr so vi carbon mang in tch).CH 3 R H2 C H2 C C CH 3</p> <p>Acid</p> <p>R</p> <p>CH 2</p> <p>+</p> <p>H2C</p> <p>C CH3</p> <p>CH3</p> <p>16</p> <p> Phn ng hydro ha olefin to thnh: Phn ng cracking s dng li khi ion carbenium loi b proton trn tm kim loi to thnh olefin v cc olefin to thnh tin hnh phn ng hydro ha trn tm kim loi thu c cc paraffin tng ng.CH 3 H 2C C CH 3 CH 3</p> <p>Metal H2H 3C C H CH 3</p> <p>R</p> <p>CH 2</p> <p>Metal H2</p> <p>R</p> <p>CH 3</p> <p>+</p> <p>H</p> <p>Phn ng cracking v hydro ha l hai phn ng chnh din ra trong qu trnh hydrocracking. Hai phn ng mong mun ny c tc dng tng h ln nhau trong cng mt qu trnh. Phn ng cracking s to ra v cung cp olefin cho qu trnh hydro ha v ngc li, phn ng hydro ha s cung cp nhit lng cho qu trnh cracking. Tuy nhin, nhit ta ra t qu trnh hydro ha cao hn so vi nhit ta ra t qu trnh cracking, v th khi xem xt ton b qu trnh th c th xem hydrocracking l phn ng ta nhit. Phn ng isomer ha lun din ra ng hnh cng vi phn ng cracking. Trong qu trnh isomer ha xy ra trc, sau cc lin kt C-C s b b gy bi qu trnh cracking.</p> <p>17</p> <p>Hnh 2 : C ch phn ng Hydrocracking</p> <p>4.2.</p> <p>Xc tc b mt hot tnh v ti sinh xc tc</p> <p>4.2.1 Xc tc b mt hot tnh S tch t cc: Cc hnh thnh l mt sn phm ph trong qu trinh cracking. Lp cc trn cht xc tc l mt hin tng nhit sau thi gian d...</p>