Effect of Metal Contamination on the Performance of Catalyst for Deep Catalytic Cracking Process

Scientific ResearchEffect of Metal Contamination on thePerformance of Catalyst for Deep CatalyticCracking ProcessZhang Zhigang(SINOPEC Research Institute of Petroleum Processing, Bejing 100083)Abstract: The efeet of dfferent metal contamination levels of catalysts for Deep Catalytic Cracking (DCC) on the distribu-tion and seletivity ofDCC products was investigated in a FCC pilot unit. The pilot test results showed that the efects ofthemetal contamination level of catalyst on the propylene yield, the coke yield, the LPG yield, the gasoline yield, the selectivity oflow carbon olefins, and coke selectivity was significant, and that the influence of metal contamination level on the conversionand dry gas yield was minor.Key words: low cartbon olefins; metal contamination; catalytic cracking; petrochemicals1 Introductionthere is quite fewer information on the study on the influ-Producion oflow-carbon olefins fom heavy oils based on ence of metal contamination level of DCC catalysts on thethe fuid calytie cracking technology, in pricular the pro dstribution and sletivity of DCC producs. This aticle,duction of proplene, have been atracting atention ofre- taking into account the posible situation of poessisg offiners both at home and abroadI-1 The Deep Catalytic Crack-an increased ratio of resid in the DCC feedstock, has pre-ing (DCC) technology developed by the Research Istute eisely studied the infuence of the contamination levelofof Petroleum Processing can use gas oil or resid-blendedDCC catalyst on the ditribution and selectivity of the DCCgas oil as the festoco to provide a propylene yield as high products.as 18%- -24%. Since the global oil resources are becom-2 Experimentaling increasingly heavier, the refineries and petrochemicalplants at home and abroad in a bid to scramble for maximum2.1 Experimental equipmenteconomic benefits are making strenuous efforts to mini-The experiments were carried out in a FCC pilot test unitmize the yield of low-cost residuum, so that an increasingwith a feed rate of 4-12 kg/h of feed oil, with all of thenumber of FCC units are being switched to processing ofreaction system, the regeneration system and the productfeed blended with VR and even processing of 100% resid.separation system running continuously and being controlledTherefore, the DCC process for maximization of low-car-in real time by computers. The process flow diagram of thebon olefins originated from FCC technology will put morepilot unit is presented in Figure 1. The high-temperaturepunch into processing of feedstock with increased blendingcatalyst exiting the regenerator enters the bottom of theofVR.reactor to contact and react with tbe feed oil. After the ter-The DCC process as the world leader is currently being ap- mination of cracking reaction the catalyst is separated fromplied on four operating units, with other four DCC units be- oil vapors, and the separated catalyst afer being sripped bying in the phase of design or ready for startup. The research steam is routed to the regenerator for coke burning. In theworkers since the successful development of the DCC pro- regenerator the spent catalyst containing the coke contactscess are working on the upgrading of DCC catalyst in an with air to burn out the coke deposited on the catalyst, soattempt to enhance the propylene yield and the propylene that th. The regeneratedselectivity and increase the conversion of residuum. The catalys中国煤化工:ivity passes throughcurrently operating DCC units mostly run on gas oil and the regTYHC N M H Gralve and then enters3China Petroleum Processing and Petrochemical TechnologyNo.2, June 2009Cracked gas|12Mainair- +Shuy Diesel Wastewater GasolineAtomizingsteamPre litig steamFigure 1 Principle process flow diagram ofpilot FCC riser test unit1- Feed oil tank;2- Feed pump;3- Feed funace;4- Riser, 5- Flue gas meter, 6- Flue gas coler 7- Regenerator; 8- Reaction dseagager,9-Heavy oil factinator 10- Light oil factioator, 11- Cooler,12- -il/water separatorthe bottom of the reactor to undergo cracking reactions with The catalyst MMC-3 applied in the experiments was a des-the feed oil.ignated for DCC process catalyst manufactured by the QiluThe oil/gas stream exiting from the disengager of the reac-Branch of the SINOPEC Catalyst Company. This catalysttor is routed to the product separation system, where theafter having been subjected to ageing in a pilot ageing unitheavy oil and diesel fraction are separated ia the fraction-under the fllowing regime: Ageing was conducted at a tem-ation column, and the reminder of oilgas stream after be-perature of 800°C under normal pressure in the presence ofing further cooled are routed to the low-pressure separa-100 % steam for 28 hours. The property of catalyst is pre-tion system to separate water, gasoline and cracked gas. Thesented in Table 2.yield of oil products after measuring is calculated, while3 Test Results and Discussionthe coke yield is calculated after measuring the flue gas3.1 Characterization of metal contamination level ofvolume by the gas flow meter and analysis of flue gas com-position by the gas chromatograph. The volume of crackedcatalystgas is measured by the gas flow meter followed by analyz-Generally speaking the H/CH, ratio is usually evaluated asing its composition by chromatograph to calculate its yield.the metal contamination level of catalyst in the FCC process,and the H/CH, ratio under different nickel contents of the2.2 feedstock and reagentsDCC catalyst is shown in Figure 2. It can be seen from theThe feed oil used in the experiments was the hydrocrackedgraph that with an increasing content of nickel deposited ontailoil provided by the hydrocracking unit at the SINOPECthe catalyst the H/CH, ratio increased linearly. Therefore,Shanghai Petrochemical Company with its property pre-despite the dominating tbermal cracking reaction and highsented in Table 1. The hydrocracked tailoil had excellentmethane yield resulted from the high DCC temperature ofproperty with a density of0.8358 g/cm' and a bydrogen coD-540- 620C. the ipfluence of metal contamination of thetent of 14.24%.DCC中国煤化工similar to the influ-The contaminating metal compound used in the tests wasence aYHC N M H Gh could confim thatnickel naphthenate.this test method and the nickel content of the catalyst couldScientific ResearchTable 1 Property of hydrocracked taililTable 3 Operating parameters of pilot unitItemsQualityDataDeisit(0C),gcm’0.8358Reaction pressure(g), MPa0.09| Aniline point, C76.5Reaction temperature, C600355| Feed oil flow rate, kg/h5.0CCR, m%<0.02Catalyst/oil ratio20.0Refractive index (m"”)1.4438Fced preheat temperature, C228Basic nitrogen, wppm4.5Atomizing stearm, m%39Elemental analysisResidence time in riser, sec2.1C, m%85.89| Space velocity in fluidized reactor, 1/b.0H, m%14242.50N, ppm8.6S, ppm17s 2.00Hydrocarbon group analysis, m%Saturates93.6g 1.50个Aromatics!51.00 tRecsins3.9Asphaltenes<0.10.50Metal contenat, ppmiiCa1.1500 1000 1500 2000 2500 3000 3500Nickel content on catalyst, ppmCuFigure2 Influence of nickel content of catalyst on H/CH,F13ratioN.7be used to cbaracterize the influence of metal contamina-Vtion of the catalyst on the product distribution and the prod-Disillation, Cucts selectivity of the DCC process.10%3143.2 Infuence of metal contamination level of catalyst30%on the distribution of DCC products50%70%448The influence of level of metal deposited on the DCC cata-90%03lyst on the product ditribution is presented in Figures 3-Table 2 Catalyst property10. It can be seen from Figure 3 that with an increasing metaltemscontamination level of the catalyst the conversion rate wasPore volume, cm/g0.29slightly decreased. When the metal content of the catalyst| Apparent density, g/cm'0.81was increased from 0 ppm to 3000 ppm, the conversion rateSieve fraction, v%was decreased merely by 0.5%. It can be seen from Figure0- - 20μm0.94 that the metal contamination level of the catalyst had a0- 40μm7.8significant effect on the coke yield. The coke yield increased0~ 80μLm49.4linearly with an increasing metal contamination level of the0- -105μm72.0catalyst. An increase of 1000 ppm of nickel on the catalyst0--149mcould result in around 5% of coke yield increase. It can be>149μm.8seen中国煤化工raminatio level ofAPS, um80.5the catTH; on the dry gas yield.Cracking activity, m%50A sligC NMHered wi”in~3China Petroleum Processing and Petrochemical TechnologyNo.2, June 2009creasing metal contamination level of the catalyst, which97might be resulted from a slight decrease of the overall con-36-version rate. It can be seen from Figure 6 that the metal95 tcontamination level of the catalyst had a significant influ-)4 中ence on the LPG yield. The LPG yield was apparently de-)3 tcreased linearly with an increasing metal contamination level92-of the catalyst. It can be seen from Figure 7 that the metal1tcontamination level of the catalyst had a significant efct)0 L001000 1500 2000 2500 300on the gasoline yield. The gasoline yield was apparently in-Nickel content on catalyst, ppmcreased with an increasing metal contamination level of theFigure 3 Inyfuence of nickel content of catalyst on conversion catalyst.rateIt can be seen from Figure 8 that the metal contamination。16.00level of the catalyst had a significant influence on the pro-14.00pylene yield. When the nickel content of the catalyst was12.00increased from 0 ppm to 1000 ppm, the propylene yield10.00plummeted quickly from 21.3% to 19.7%; and when the8.00nickel content of the catalyst increased from 1000 ppm to6.002000 ppm, the reduction in propylene yield was slowed down.4.00When the nickel content of the catalyst exceeded 2000 ppm,2.00the amplitude of reduction in propylene yield was appar-501000 1500 2000 2500 300031.0Nickel conteat on catalyst, ppmFigure 4 Influence of nickel content in catalyst on coke yield30.02529.0 :00 1500 2000 2500 30008010001500 2000 2500 3000Figure 7 Influence of nickel content in catalyst on gasolineyieldFigure 5 Influence of nickel content in catalyst on dry gas49.021.0048.0，20.5047.0 |豆20.0046.019.50N45.019.0044.0 I1 s002000 25003000s0中国煤化Is,ppmNickel content on catalys, ppmFiguYHC N M H Ganalyst on poplmeFigure 6 Influence of nickel content in catalyst on LPG yieldytela40Scientific Research19.5036.0035.0019.00●34.00蓄18.5033.00001000 1500 2000 2500 3000Nickel content oo catalyst, ppm32.00Figure 9 Infuence of nickel content in catalyst on total0500 1000 1500 2000 2500 3000butylene yieldNickel content on catalyst, ppmFigure 11 Influence of nickel content in catalyst on concentra-tion ofgaseous propylene and total butylene●-Propylene/LPG yeld;◆- -Total buyleneLPG yieldylene io cracked gas decreased slightly in linear proportion.It can be seen from Figure 13 that with an increasing metalcontamination level of the catalyst the concentration of pro-50020002500 3000pylene in LPG at first slumped quickly and then graduallyFigurer 10 Influence of nickel content in catalyst on ethylenetapered off. When the nickel content of the catalyst in-yielacreased from 0 ppm to 1000 ppm, the concentration of pro-ently tapered off, and the change in propylene yield was notpylene in LPG decreased in big chunks, and when the nickel13.0remarkable. It can be seen from Figure 9 and Figure 10 thatthe influence of the metal contamination level of the cata-lyst on the total butylene yield was not remarkable, and theethylene yield decreased slightly with an increasing metal12.0contamination level of the catalyst.3.3 Influence of metal contamination level of catalyst on11.0product selectivity ofDCC processThe influence of amount of contaminated metals depositedon the catalyst on the selectivity of products of the DCC Figure 12 Influence of nickel content in catalyst on concentra-process is presented in Figures 11- -15. It can be seen fromtion ofethylene in gasFigure 11 that with an increasing metal contamination level44.5of the catalyst the propylene concentration in cracked gas44.0at first quickly dropped and then gradually leveled off. When43.the nickel content on the catalyst increased from 0 ppm to1000 ppm, the propylene concentration in cracked gas de-clined drastically, and then the propylene concentration in42.5cracked gas was stabilized at around 34% when the nickelE 42content on the catalyst exceeded 1000 ppm. With an in-creasing metal contamination level of the catalyst the con-41.50 50010001500 2000 2500 3000centration of total butylene in cracked gas increased slightly.中国煤化_alys, ppmIt can be seen from Figure 12 that with an increasing metalent in catalyst oncontamination level of the catalyst the concentration of eth-MHCNMHGeimLPG41China Petroleum Processing and Petrochemical TechnologyNo.2, June 200942Based on the above-mentioned facts, the metal contamina-tion level on the catalyst had an apparent influence on theyields of propylene, coke, LPG and gasoline produced bythe DCC process aimed at maximization of low-carbonolefins, and had distinct impact on the propylene, ethyleneand butylene seletivity with the biggest effect exercisedon the propylene selectivity.0二10001500 20002500 30005 ConclusionsNickel content on catalyst, ppmFigure 14 Influence of nickel content in calalyst on(1) The metal contamination level on the catalyst had anconcentration oftotal buylene in LPGapparent infuence on the yields of propylene, coke, LPGand gasoline produced by the DCC process aimed at maxi-6.9mization of low-carbon olefins, and had a distinct impact.8on the low-carbon olefins and coke selectivity.6.76.6 I(2) The metal contamination level on the catalyst for DCC6.5process aimed at maximization of low-carbon olefins dido/not have signifcant effect on the conversion rate and dry贵636.2gas yield, but had an apparent effect on the hydrogen yield.References500 1000 1500 2000 2500 3000[1]Gao Yongdi, Shan Honghong, Yang Chaohe, etal. Laboratory studyNickel content on catalys, ppmof enbancing ethylene and propylene yield by two-stage riser cata-Figure 15 Influence of nickel content of catalyst on cokelytic pyrolysis technology[J]. Petroleum Processing andselectivitycontent of the catalyst exceeded 2000 ppm, the concentrationPetrochemicals, 2008, 39(4):46 -50(in Chinese)of propylene in LPG basically did not change further. It can[2] Duan Xiuhua, Shan Honghong, Li Chunyi, et al. Study on thebe seen from Figure 14 that with an increasing metal contami-atlytic pynolysisofrecyclingC. fraction for maximum propyleneproductio[J. Petroleum Proessing and Petrochemicals, 2008,39(9):nation level of the catalyst the concentration of total buty-5-8(in Chinese)lenein LPG needenearr Itcan be scen fom Figure 15 (3)Zhang Zhoqion ui Zheng. Xie Caogag, et al. Study on thethat with an increasing metal contamination level of the cata-propylene formation during deep catalytic cracking ofheavy oil[D].,lyst the coke yield and conversion rate increased apparently. Petroleum Processing and Petrocbemicals, 2008, 39 (12):28-32(inChinese)Mechanical Completion of Oxidation Reactor of the PTAUnit at Nanjing Baose Stock Company PassedAcceptance TestIn February 2009 the first in China one-million-ton-classThe workmanship for fabrication of the reactor bas reachedoxidation reactor of the PTA unit developed by the Nanjing the domestic leading level and the intemal advanced levelBaose Stock Company had passed the acceptance test on with its cost being only balf of the price of importedmechanical completion of the equipment and had beenequipment, which can drastically reduce the investment costshipped to the PTA base at the Pengwei Petrochemical Lim- and p中国煤化工compliance with theited Liability Co. in Chongqing Fuling. The aprasal ofthe policyYHC N M H Gion of equipment insaid equipment as quoted by relevant experts is as follows. China.