Applied Catalysis A: General 255 (2003) 345–347

Exploratory study on upgrading 1-butene using spent FCCcatalyst/additive under simulated conditions of FCCU’s stripper

Yong Lua,b,∗, Ming-Yuan Hea,c, Xing-Tian Shua, Bao-Ning Zongaa Research Institute of Petroleum Processing, China Petrochemical Corporation, Beijing 100083, PR China

b Chemical Engineering Department, Auburn University, 230 Ross Hall, Auburn, AL 36849, USAc Chemistry Department, East China Normal University, Shanghai 200062, PR China

Received 7 April 2003; received in revised form 16 July 2003; accepted 16 July 2003

Abstract

A novel method for upgradingn-butene into more useful propylene, iso-butene, iso-butane even gasoline using spent fluidcatalytic cracking (FCC) catalysts/additives in the stripper part of fluid catalytic cracking unit (FCCU) has been proposed. Thesimulative tests were carried out on a widely used MAT equipment, using 1-butene as feed. High temperature and low spacevelocity favor the formation of propylene, iso-butene and iso-butane. The presence of MFI additives promotes propylene andiso-butene but suppresses iso-butane formation.© 2003 Elsevier B.V. All rights reserved.

Keywords: FCC catalyst/additive; Stripper; Butene; Propylene; iso-Butane

1. Introduction

The modern fluid catalytic cracking (FCC) pro-cess is not only a major workhorse in refineries forthe production of motor fuel, but it also becomesan important source for propylene and precursors ofalkylate/ether that are high-octane gasoline blendingcomponents and additives. Nevertheless,n-butenesupplies from FCC family processes are excess be-cause of inadequate iso-butane supplies forn-butenealkylation. For maximizing benefit of refiners, it isworthwhile to investigate ways for upgrading excessFCC n-butene into more useful propylene, iso-buteneand iso-butane, using existing equipments such asreactor/stripper of FCC units (FCCUs).

∗ Corresponding author. Tel.:+1-334-8442005;fax: +1-334-8442085.E-mail address: yonglu@eng.auburn.edu (Y. Lu).

In this study, we proposed a method for upgradingn-butene using spent FCC catalysts/additives in thestripper part of FCCUs, instead of a separate olefinupgrader, into more useful propylene, iso-butene,iso-butane even gasoline. The simulative tests werecarried out on a widely used MAT equipment, using1-butene as feed. The effects of temperature, spacevelocity, and the presence of MFI additives on the se-lectivity of desired products were studied. Two spentcatalysts from commercial FCCUs were also tested.

2. Experimental

2.1. Catalysts and zeolites

A commercially available FCC catalyst (CC-16)containing only a novel ultrastable Y-zeolite (SRY,Changling Petrochemical Works, Hunan province, PRChina), was chosen as a base catalyst in this study. Two

0926-860X/$ – see front matter © 2003 Elsevier B.V. All rights reserved.doi:10.1016/S0926-860X(03)00588-X

346 Y. Lu et al. / Applied Catalysis A: General 255 (2003) 345–347

spent FCC catalysts both containing MFI additivesfrom commercial units, Centurion 43L and CHV-1(provided by Luoyan Oil Refinery, Henan province,PR China), were also used to upgrade 1-butene.

Two commercially available MFI type zeolites,ZRP-5 (SiO2/Al2O3: >200) and RPSA (SiO2/Al2O3:∼60) developed by Research Institute of PetroleumProcessing, were used as additives and blended withCC-16 catalyst respectively for studying the effects ofthe presence of MFI additives on upgrading reactions.

CC-16 and CC-16 with 5 wt.% ZRP-5 or RPSAwere all pressed, crushed, sieved into 20–40 mesh par-ticles, and aged then in 100% steam at 800◦C for 4 h.

2.2. 1-Butene upgrading

The 1-butene upgrading reaction was carried outin a widely used downflow MAT (micro-activity test)unit designed for handling heavy oil feeds. Cata-lyst loading was always 5 g. Prior to reaction with1-butene, CC-16 and CC-16 with 5 wt.% MFI ad-ditives were run in the MAT unit at 500◦C, 16 h−1

WHSV with the heavy oil (properties are describedin detail in literature[1]) and purged then with N2 for30 min. Spent Centurion 43L and CHV-1 were purgedby N2 flow for 30 min at 500◦C prior to use. Reactionwith 0.56 g 1-butene was carried out at the indicatedtemperatures and times followed by a 10 min N2purge. The products were quenched by ice bath andseparated into liquid and gas products. Gas was ana-lyzed using a HP5880A gas chromatograph. Coke was

Table 1Activity and selectivity of CC-16 catalyst for 1-butene upgrading at different temperatures and WHSVa

400◦C(WHSV = 4.92 h−1)

500◦C(WHSV = 1.44 h−1)

500◦C(WHSV = 4.92 h−1)

500◦C(WHSV = 6.00 h−1)

1-Butene conversion (wt.%) 80.33 83.12 83.25 79.32

Product selectivity (wt.%)C1–C2 0.12 0.53 0.47 0.31Propane 0.25 0.55 0.48 0.29Propylene 3.32 10.22 9.88 6.30n-Butane 1.16 4.30 3.99 2.97iso-Butane 1.28 5.27 4.00 2.27iso-Butene 5.18 15.83 13.93 11.10t-2-Butene 46.36 28.14 29.23 36.48c-2-Butene 32.63 20.70 21.75 27.13C5

+ 9.13 13.71 15.79 12.94Coke 0.57 0.87 0.48 0.22

a Coke on spent CC-16 catalysts before upgrading reaction is 2.06 wt.%.

determined by burning it and analyzing for CO2 usingan IR detector. The coke selectivity was defined as 100× (total coke after reaction− coke on spent catalystsbefore reaction)/(1-butene feed weight×1-butene con-version). Mass balances greater than 95% was used.

3. Results and discussion

Tables 1 and 2outline the reaction results for1-butene upgrading with neat CC-16, CC-16 with5 wt.% MFI additives, and spent Centurion 43L andCHV-1, respectively. All catalysts, even though pre-viously coked, were capable of reacting with the1-butene. As seen inTable 1, increasing tempera-ture and lowering WHSV both increased selectivityto propylene, iso-butene, iso-butane at the expenseof 2-butenes. Selectivity to those products rose from∼10% at 400◦C to ∼28% at 500◦C and from∼20%at 6 h−1 to ∼31% at 1.44 h−1; selectivity to C5

+ liquidproducts rose from∼9% at 400◦C to 15% at 500◦C.

In comparison with neat CC-16, MFI additivesincreased propylene, iso-butene but suppressed theiso-butane formation (seeTable 2). The RPSA ad-ditive (SiO2/Al2O3: ∼60) made more propylene,iso-butene and iso-butane than the ZRP-5 MFI ad-ditive (SiO2/Al2O3: >200). The ZRP-5 has higheracidic strength than RPSA zeolite but its acid densityis no more than half of the later[2]. Clearly, selectiv-ity to those desired products is parallel well with theacid density of MFI additives.

Y. Lu et al. / Applied Catalysis A: General 255 (2003) 345–347 347

Table 2Activity and selectivity of CC-16 catalyst with 5 wt.% MFI additives and two commercial spent catalysts for 1-butene upgrading at 500◦Cand WHSV of 4.92 h−1

CC-16+ ZRP-5 (2.14) CC-16+ RPSA (2.35) Centurion 43L (2.94) CHV-1 (2.81)

1-Butene conversion (wt.%) 81.22 83.50 82.96 83.35

Product selectivity (wt.%)C1–C2 0.47 0.49 0.49 0.52Propane 0.47 0.56 0.57 0.61Propylene 10.94 12.63 13.22 13.36n-Butane 3.30 3.93 3.87 3.89iso-Butane 3.67 3.79 3.76 3.75iso-Butene 15.16 17.03 17.27 17.02t-2-Butene 28.05 26.43 25.80 25.82c-2-Butene 20.90 18.91 19.35 19.27C5

+ 16.34 15.49 15.11 15.13Coke 0.68 0.73 0.55 0.61

The values in the brackets represent the coke (wt.%) on spent catalyst before the reaction.

Table 2 also shows that the spent Centurion 43Land CHV-1 catalysts gave over 34% selectivity topropylene, iso-butene and iso-butane, with >80%1-butene conversion. NH3-TPD measurements (pro-cedure is described in detail in literature[3]) show thatspent Centurion 43L and CHV-1 possessed∼30%acidity retention, compared to the correspondingequilibrium catalysts. Additionally, these two spentcatalyst offered 28–30% conversion in LCO crackingtest (ASTM-3907-80 micro-activity test). The resultsindicate that the spent catalysts did not deactivatecompletely yet. As a result, acid-catalyzed dispro-portionation, isomerization, hydrogen transfer, cokeformation reactions predominantly took place on thespent catalysts, just accompanied by slight pyrolysisthat resulted in a little C1–C2 formation.

4. Conclusions

Under simulated condition of FCCU’s stripper,the spent catalysts all are capable of reacting with

1-butene, but selectivity to propylene, iso-butene andiso-butane significantly depends on the conditionsand presence/absence of MFI additives. Increasingtemperature and lowering WHSV increase selectivityto propylene, iso-butene and iso-butane. MFI ad-ditives promote propylene, iso-butene but suppressiso-butane formation. 2-Butene is always the domi-nant product, which can be alkylated with iso-butaneto produce highly branched octane with higher octanenumber than 1-butene can.

References

[1] Y. Lu, M. He, J. Song, X. Shu, B. Zong, Stud. Surf. Sci. Catal.134 (2001) 209.

[2] Y. Lu, postdoctoral report, Research Institute of PetroleumProcessing, 1999.

[3] Y. Lu, M.-Y. He, X.-T. Shu, B.-N. Zong, Energy and Fuel(2003), in press.