High-quality fuel distillates produced from oligomerization of light olefin over supported phosphoric acid on H-Zeolite-Y
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Oligomerization of isobutene to produce high-quality fuel distillates in the range of gasoline, jet fuel and diesel free of sulfur, nitrogen and aromatic hydrocarbons has been investigated over a new environmental-friendly, clean and long-lifetime supported phosphoric acid on H-Zeolite-Y catalyst with SiO2/Al2O3 mol ratio of 60. The catalyst was obtained by acid impregnation and ultrasonic vibration technique with successive heating at different temperatures and under atmospheric pressure. The catalysts were characterized by several techniques (BET, SEM, XRD, TDA, TGA and XPS). The oligomerization reactions were carried out in a gas phase using fixed-bed flow reactor at variable temperature ranges between 50 and 100 °C under atmospheric pressure with a space velocity (WHSV) of 176 h−1.The fuel distillates were identified by GC/MS and quantified by gas chromatography. The results showed that the conversion of isobutene into distillates ranges between 97 and 100%. The maximum selectivity to C 8 = isomers is about 65%, and a flow rate of isobutene 5.0 ml/min. and temperature 50 °C were obtained. Research octane number under the above-mentioned conditions ranges between 85 and 96, and Reid pressure ranges between 27 and 125 Pa.
KeywordsAlkylates Clean fuel Oligomerization Phosphoric acid/zeolite catalyst
Alkylates containing C8 fractions or higher hydrocarbons are usually produced from the alkylation of isobutane with olefin, processed in the presence of concentrated sulfuric acid or hydrogen fluoride, which is used as a liquid catalyst. The demand for branched C8 fractions (isomers) has increased sharply due to their use as prime solvents and additives to gasoline. The present alkylation process suffers from inherent drawbacks such as corrosion, toxicity and environmental problems. Therefore, the oligomerization of light olefins might be an attractive alternative to produce liquid hydrocarbon alkylates as components of gasoline and high-value petrochemical products.
In addition, in view of the growing concern about environmental pollution, and due to US and European legislation, fuel reformulation is now carried out around the world, focusing on reducing evaporative emissions, lowering sulfur content and aromatics and on complete fuel combustion. In this context, an interesting route for the production of environmentally friendly fuel is the dimerization, trimerization, tetramerization or oligomerization of light olefins .
This process is particularly attractive, since the olefin C4 fractions of the FCC process can be used as a feed, with isobutene, 1-butene and 2-butenes as the main components of this fraction. When the olefin source is isobutene, highly substituted C8 olefins are obtained [2, 3, 4, 5, 6, 7, 8, 9].
A number of catalysts have been used in the dimerization and oligomerization of olefins [10, 11, 12, 13, 14, 15]. Phosphoric acid catalysis for light olefin oligomerization and alkylation has been around since the early 1930s in various forms: liquid-phase acid , phosphoric acid supported on quartz  and solid phosphoric acid [18, 19, 20]. The term “supported liquid-phase catalyst” has also been used to describe solid phosphoric acid . In a more recent work, supported ionic liquid-phase (SILP) catalyst was used to produce isoolefin which can be used as a fuel blending .
The oligomerization process using phosphoric acid on a silica support as a catalyst has been used for several years to produce gasoline . The reaction is carried out at temperatures over 200 °C, and products range from the dimer (C8) to higher polymeric olefins (C16) [24, 25]. More recent work  showed higher conversion of olefins to fuel distillates, up to 99%.
The scientific interest and commercial importance of the oligomerization of butenes has led to the search for new solid catalytic materials that can avoid the formation of higher molecular weight olefins due to their controlled acidity. Among the catalysts reported for this reaction, other than phosphoric acid over silica, are Ziegler–Natta-based catalysts , zeolites [31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41], sulfated zirconia [42, 43], sulfonic resins , benzyl sulfonic acid on silica , mica montmorillonite , titanium oxide , nickel (II)-exchanged amorphous silica-alumina catalysts , zirconium oxide [49, 50], cationic resins [51, 52, 53, 54, 55, 56] and SiO2-Al2O3 [57, 58, 59].
In addition, modification of the above-mentioned oxides with sulfates, tungstates or phosphates has been widely investigated by several authors in order to modify the acidic properties and stabilize the support [47, 49, 60]. A small selection of patents is included in references [61, 62, 63, 64, 65, 66, 67].
The oligomerization of isobutene over resin catalysts is a well-known reaction and was studied by Haag nearly 40 years ago .The reaction was also studied over cationic ion-exchange resin, Amberlyst-15, by Ramo et al. .
Olefin oligomerization is a reaction for which the activity and selectivity strongly depend on the catalyst, support and operating conditions such as temperature, pressure and weight hourly space velocity (WHSV). The light olefin oligomerization route, catalyzed by acid sites, is a promising way to obtain a premium-quality fuel, free of sulfur, nitrogen and aromatic compounds.
Usually, the oligomerization of olefins to obtain fuels is carried out in liquid phase, using phosphoric acid impregnated in a solid support or ionic exchange, with resins as catalysts, which presents important disposal problems or strong deactivation, respectively [70, 71].
Although preferential oligomerization of isobutene has been commercialized by using SiO2-Al2O3 catalysts, low selectivity remains a serious problem with the use of these catalysts . In addition, the lower catalytic activity of existing SiO2–Al2O3 catalysts is another problem. Therefore, new catalysts with high activity and selectivity for the oligomerization of isobutene for high conversion and high selectivity into fuel distillates are needed.
This paper is about the development of a new supported phosphoric acid on H-Zeolite-Y for the oligomerization (dimerization, trimerization and/or tetramerization) of isobutene.
The paper also discusses the production of distillates in the range of clean fuel such as gasoline, jet fuel and diesel, free of sulfur, nitrogen and aromatic compounds, by using the above type of catalyst and oligomerization reactions.
Solution (A): 4.9 g (50 mmol) of phosphoric acid was dissolved at room temperature in 40 ml of 1,1,2-trifluorochloroethane. The solution was stirred at room temperature for 30 min and then at 35 °C for 2 h until a clear solution was obtained. The resulting solution was then ultrasonated for 60 min.
The ultrasonated mixture of (1) was added to 12.5 g of zeolite as support. The resultant mixture was stirred for 60 min and ultrasonated for 12 h at temperatures of 30–40 °C until a homogeneous mixture was obtained.
The resulting mixture from (2) was heated under vacuum at a temperature of 40 °C to remove the solvent. The supported phosphoric acid was then transferred to an autoclave under dry nitrogen. The latter was sealed and placed in a vacuum oven overnight at a temperature of 150 °C.
The produced supported catalyst was then ultrasonated under dry conditions for 3 h and was then characterized with the following instruments.
Catalyst characterization and evaluation
Powder X-ray diffraction patterns (XRD) were obtained from a Bruker D8 Advance diffractometer, using Cu Kα radiation with X-ray gun operated at 40 kV and 30 mA, using a scan rate of 4°/min (2θ).
Scanning electron microscope (SEM) The crystal size and morphology of microscale supported phosphoric acid on H-ZSM-Y zeolite were determined with a FEI–NNL200 scanning electron microscope (SEM). The silicon, phosphorous, oxygen and aluminum contents of the supported and unsupported H-ZSM-Y zeolite were obtained using EDAX Ametek, Model 60040, 10 kV.
X-ray photoelectron spectroscopy (XPS) studies were recorded on a JEOL JPS 9010 MC photoelectron spectrometer using MgKα (1253.6 eV) radiation from an X-ray source operating at 10 kV and 20 mA. The measurements were performed at room temperature, and the working pressure was lower than 35 × 10-7 pa.
Surface area, pore volume and pore size measurement studies were carried out using a Micromeritics ASAP 2010 system.
Differential thermal analysis (DTA) was recorded on a Perkin Elmer (DTA-7) with a heating rate of 5 °C/min, using thermal analysis controller TAC-7/DX.
The reactor was coupled with a mass flow meter to measure unreacted isobutene. The reactor was heated in an electrical furnace, and the reactor’s temperature was measured by a thermocouple located inside the furnace and was controlled by a temperature controller (Cole Parmer Digi-sense).
One gram of catalyst was loaded into the middle of the reactor. The feedstock of the oligomerization reaction consisting of isobutene or a mixture of isobutene with helium gas was introduced at the top of the reactor. Normally, the flow rate of isobutene is 5–20 ml/min under atmospheric pressure. The flow rate of isobutene was adjusted through a separate thermal mass flow controller (Bronkhorst). The oligomerization reaction products were collected in a cooled condenser attached to the end of the reactor and were analyzed using a gas chromatograph.
the activity of the supported catalyst
the yield and selectivity of hydrocarbon distillates in the range of gasoline, jet fuel and diesel
Blank reactor runs were conducted and no significant conversions were observed under the conditions of the oligomerization reaction.
GC and GCMS
Gas chromatographic analysis of the alkylation products was performed on a Varian 3800 series instrument fitted with a flame ionization detector. The column was 100 m × 0.25 mm glass open tubular capillary PONA column.
Identification of the oligomerization reaction products was performed on Shimadzu GC/MS–QP2010. The GC was fitted with a PONA 100 m glass open tubular capillary column.
Weight hourly space velocity
The weight hourly space velocity (WHSV) value was calculated as a function of the isobutene feed (g h−1), and the weight of catalyst used (g). The effect of the addition of diluents in the feed was also studied.
Octane number and Reid vapor pressure calculation
The hydrocarbon total by group type (isoparaffins, olefins and paraffins), research octane number (RON), and Reid vapor pressure (RVP) was calculated using Varian Detailed Hydrocarbon Analysis (DHA) version 5.5 SN 00208.
(mass of converted isobutene) (mass of isobutene initially loaded)−1 × 100.
(mass of product fraction) (mass of reacted isobutene)−1 × 100.
S-dimers (C 5 = to C 8 = dimers),
S-trimers (C 9 = to C 12 = trimers),
S-tetramers (C 13 = to C 16 = tetramers).
Results and discussion
Catalyst and support characterization
XPS data of supported catalyst and support
The X-ray photoelectron spectroscopy (XPS) technique was applied to investigate the binding energies of the states of element and the possible formation of any new bonds between the phosphoric acid catalyst and support. Three samples were tested (1) H-Zeolite-Y support, (2) supported phosphoric acid on H-Zeolite-Y before heating at 150 °C and (3) supported phosphoric acid on H-Zeolite-Y after heating at 150 °C. The XPS data of wide scan, narrow scan and curve fitting for all the above samples were recorded. All binding energy referred to C1 s = 285.0 eV. Data for the elements, Al 2p1/2, P 2p, Si 2p1/2, and O1 s binding energies are shown in Table 1.
Curve fittings X-ray photoelectron spectroscopy analysis of the support and of the supported phosphoric acid on H-Zeolite-Y
Sample of supported catalyst and support
XPS BE (eV)
O 1 s
Differential thermal analysis (DTA) of supported catalyst and support
supported phosphoric acid on H-Zeolite-Y before heating at 150 °C,
supported phosphoric acid on H-Zeolite-Y after heating at 150 °C.
SEM data of supported catalyst and support
XRD data of supported catalyst and support
Physisorption data of supported catalyst and support
Texture properties of unsupported and supported H-zeolite
S BET a (m2/g)
S pore b (m2/g)
V pore c (cm3/g)
D pore d (A°)
Supported phosphoric acid on
Catalytic activity for isobutene oligomerization
Conversion of isobutene and the yield of fuel distillates
The effect of temperature on isobutene conversion as well as on oligomer distribution has been studied over a range of 50–100 °C. One reason for this is the fact that the oligomerization of isobutene is a very exothermic reaction .
The major product of the oligomerization reaction over supported phosphoric acid on H-Zeolite-Y catalyst was C5–C8 fractions. The yield of C5–C8 distillates in the range of gasoline decreased from 48% to 12% as the temperature increased from 50 °C to 100 °C. The maximum yield obtained was about 48% at 50 °C with a space velocity of isobutene 176 h−1 as shown in Fig. 9.
Similar trends in the yield of higher distillates of C13 to C16 were obtained under variable temperature. The yield of C13 to C16 fractions in the diesel range increased from 8.0% to 12.0% as the temperature increased from 50 °C to 100 °C as shown in Fig. 9.
Selectivity to gasoline–jet fuel–diesel distillates over supported P/Z catalyst
Selectivity to gasoline–jet fuel–diesel distillates over H-Zeolite-Y and supported P/Z catalyst
It is known from the work of Krawietz et al.  that the support does not contribute to the catalysis and that the phosphoric acid is the active phase, which is similar for all supported phosphoric acid catalysts at equilibrium. However, both H-ZSM-Y support and phosphoric acid play an important role in determining the accessibility to the active phase.
The selectivity of C5–C8 fractions (65%) in the gasoline range over supported phosphoric acid on H-Zeolite-Y catalyst at 50 °C is higher than that on unsupported H-Zeolite-Y at the same temperature, as shown in Fig. 11. This decreased to about 14% as the temperature increased to 100 °C because of the formation of higher distillates, C13 to C16 fractions in the jet fuel range. Consequently, the selectivity of C5–C8 fractions (58%) over unsupported zeolite at 100 °C is still lower than that of supported zeolite at 25 °C. This is due to the fact that oligomerization is an exothermic reaction, and upon raising the temperature, the rate of reaction increases. The selectivity to C5–C8 fractions is higher than that reported in other work, in which low selectivity for the dimer was reported . The conclusion which we can make is that there is better selectivity to C4–C8, C9–C12 and C13–C16 distillates over supported phosphoric acid on zeolite.
Effect of increasing time-on-stream
The supported phosphoric acid catalyst examined showed virtually identical trends with increasing time-on-stream, in that there was a steady conversion of isobutene and a steady yield of distillates over a period of more than 21 months, at variable temperatures of 50 °C, 75 °C and 100 °C, as shown in the figures below. The highest steady C5–C8 yield in the gasoline range observed was just over 40%, obtained at temperature of 50 °C with increasing time-on-stream, while C9–C12 in the jet fuel range was about 53% and C13–C16 in the diesel range was about 8%. The same trend was observed at a temperature of 75 °C, a steady conversion of 99.8% and a steady yield in the gasoline range of about 21%, in the jet fuel range about 74% and in diesel range about 15%, while 97%, 13%, 75%, 12%, respectively, were obtained at 100 °C. It can be seen from Figs. 12, 13 and 14, for a period of 7 months, that isobutene conversion fell to 97% at 100 °C, and a steady yield of 75% in the jet fuel range was obtained.
Supported phosphoric acid on H-Zeolite-Y zeolite by acid impregnation and ultrasonic vibration technique showed very high conversion and activity in the catalytic oligomerization of isobutene in a continuous gas phase. Under optimized conditions, clean fuel distillates in the range of gasoline, jet fuel and diesel, free of sulfur, nitrogen and aromatic compounds, were obtained. Selectivity to gasoline–jet fuel–diesel distillates is much better over supported phosphoric acid on zeolite catalyst than that of unsupported zeolite. The maximum conversion of isobutene was 100%, the selectivity of C5–C8 distillates 65% in the gasoline range, the selectivity to C13–C16 distillates 15% in the range of diesel, at variable temperatures (50 °C, 75 °C, 100 °C) and under atmospheric pressure. Octane number ranging between 85 and 96 and Reid vapor pressure ranging between 27 and 125 Pa were obtained, with the lifetime of the catalyst being over than 21 months.
The authors would like to acknowledge Dr. Turki bin Saud bin Mohammad Al Saud, President of King Abdulaziz City for Science and Technology, for his valuable support and for funding this work at King Abdul Aziz City for Science and Technology. They are also grateful to Mr. Abdul Rahman Alghihab and Mr. Sultan Albishi for their kind assistance in this work.
- 6.Ivars F, Lopez Nieto JM (2011) Light alkanes oxidation: targets and current challenges. In: Duprez D, Cavani F (eds) Handbook of advanced methods and processes in oxidation catalysis. Imperial College Press, London, UK, pp 767–834Google Scholar
- 11.Forni L, Invemizzi R, Van Mao L (1975) N-butene dimerization over Ni Zeolite catalyst kinetic and mechanistic study. La Chimica E L’Industria 57:577–579Google Scholar
- 12.Miller SJ (1986) Two-stage multiforming of olefins to tetramers. US Patent 4608459Google Scholar
- 14.Podrebarac G (1992) The dimerization of 1-Butene using catalytic distillation. Thesis, University of Waterloo, Waterloo, Ontario, CanadaGoogle Scholar
- 17.Langlois GE, Walkey JE (1951) Proceedings third world petroleum congress-section IV, pp 191–200Google Scholar
- 23.Gary JH, Hadwerk GH (1994) Petroleum refining technology and economics, 3rd edn. Dekker, NYGoogle Scholar
- 26.Al-Kinany M, Al-Khowaiter S, Al-Drees S, Alshehri F, Al-Rasheed R (2018) Nanocatalyst for conversion of monoolefins, process for conversion of monoolefins and process for preparing catalyst. EP2332647B1Google Scholar
- 28.Carlini C, Marchiona M, Raspollo Galleti AM, Sbrana G (2001) Olefin oligomerization by novel catalysts prepared by oxidative addition of carboxylic acids to nickel(0) precursors and modified by phosphine ancillary ligands and organoaluminum compounds. J Mol Catal A: Chem 169:79–88CrossRefGoogle Scholar
- 47.Mantilla A, Ferrat G, Tzompantzi F, López-Ortega A, Romero E, Ortiz-Islas E, Gómez R, Torres M (2004) Room temperature olefins oligomerization over sulfated titania. Chem Commun (13):1498–1499Google Scholar
- 61.Dakka JM, Geelen M, Allen PW, Mathys GMK (2001) Process for the selective dimerization of isobutene. WO Patent 01/46095Google Scholar
- 62.Evans TI, Karas LJ, Rameswaran R (2002) Selective olefin oligomerization. US Patent 6,376,731Google Scholar
- 63.Di Girolamo M, Marchionna M, Tagliabue L (2002) Process for the production of hydrocarbons with a high octane number by means of the selective dimerization of isobutene with acid catalysts. US Patent 6,500,999Google Scholar
- 64.Hamamatsu T, Kimura N, Takashima T, Morikita T (2010) Solid phosphoric acid catalyst and method for dimerization of olefin using same, to Nippon Oil Corporation, US Patent 7,741,527. 22 June 2010Google Scholar
- 65.Hamamatsu T, Kimura N, Takashima T, Morikita T (2012) Solid phosphoric acid catalyst and method for dimerization of olefin using same, to Nippon Oil Corporation, US Patent 8,203,025. 19 June 2012Google Scholar
- 66.Kimura N, Hamamatsu T (2016) Olefin dimers and method for producing and washing olefin dimers, to JX Nippon Oil & Energy Corporation, US Patent 9,314,784. 19 April 2016Google Scholar
- 67.V.-M. Purola, S. Toppinen, A. Pyhalahti, M. Lindblad, J. Gronqvist, P. Siira, US Patent Appl. 2003/0088134Google Scholar
- 68.Haag WO (1967) Oligomerization of isobutylene on cation exchange resins. Chem Eng Prog Symp Ser 63:140–147Google Scholar
- 72.Japan patent (assigned to Idemitsu Kosan), Method for producing olefin oligomer. JP 2005-015383 (2005)Google Scholar
- 73.Tsai MJ, Kolodziej R, Ching D (2002) Processing methods enable using ‘stranded' MTBE facilities and feedstocks for high-octane applications. Hydrocarbon Process 81:81–88Google Scholar
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