Production Of Light Olefins Research Articles

Secondary Cracking of Gasoline and Diesel from Heavy Oil Catalytic Pyrolysis

This paper investigated the secondary cracking of gasoline and diesel from the catalytic pyrolysis of Daqing atmospheric residue on catalyst CEP-1 in a fluidized bed reactor. The results show that the secondary cracking reactivity of gasoline and diesel is poor, and the yield of total light olefins is only about 10% (by mass). As reaction temperature increases, ethylene yield increases, butylene yield decreases, and propylene yield shows a maximum. The optimal reaction temperature is about 670°C for the production of light olefins. With the enhancement of catalyst-to-oil mass ratio and steam-to-oil mass ratio, the yields of light olefins increase to some extent. About 6.30% of the mass of total aromatic rings is converted by secondary cracking, indicating that aromatic hydrocarbons are not easy to undergo ring-opening reactions under the present experimental conditions.

Effects of large pore zeolite additions in the catalytic pyrolysis catalyst on the light olefins production

To increase the light olefins selectivity of catalytic pyrolysis catalyst for heavy oil processing, the effects of large pore zeolite additions on the selectivity to light olefins (ethylene and propylene) were studied in a micro-activity test (MAT) unit at 625 °C by using Daqing heavy oil and n-decene/ n-decane as feedstocks. Rare earth containing ultra-stable Y, Hβ and four types of alkali-treated Hβ with different pore size distributions were employed as the large pore zeolite components. The yields of C 2–C 3 light olefins showed a volcano trend with the increasing amount of large pore zeolite additions. They reached up to 24.5 and 26.7 wt%, respectively, when an optimum combination of zeolites ZSM-5 and RE-USY or ZSM-5 and alkali-treated Hβ was used. Moreover, increasing the pore size of large pore zeolites also led to the increases in the yields of light olefins, the maximum total yields of ethylene and propylene reached up to 26.7 wt% when the total pore volume of the zeolite Hβ added was 0.452 cm 3 g −1.

Effect of reaction conditions on the catalytic performance of Fe-Mn catalyst for Fischer-Tropsch synthesis

The effects of reaction conditions on the performance of an Fe-Mn catalyst for Fischer-Tropsch synthesis (FTS) have been investigated in a continuous spinning basket reactor. Experiments were carried out under a wide range of industrially relevant reaction conditions including reaction temperature of 533–573 K, pressure of 0.93–2.96 MPa, inlet H 2/CO molar ratio of 0.80–2.50 and space velocity of (0.46–1.85) × 10 −3 N m 3 kg cat −1 s −1. The selectivities to low molecular weight hydrocarbons basically increased with the increase of reaction temperature, total pressure and inlet H 2/CO ratio, except for ethylene. The FTS reaction rate and the overall oxygenates formation rate increased with increasing reaction temperature, pressure, space velocity and H 2/CO ratio on the whole. It was found that the catalyst has relatively high activity and selectivity in producing light alkenes. It also exhibited excellent stability during the 700 h run at H 2/CO ratio of 1.00, which indicates that the catalyst has good longevity and is suitable for syngas derived from coal with low H 2/CO ratio to produce light olefins and high-quality liquid fuels. Meanwhile, it may have potential promising applications in advanced stirred tank slurry reactors. In addition, the detailed investigation of FTS reaction performance for the Fe-Mn catalyst can provide full and accurate basic information for industrial scale-up.

Catalytic performance of chloromethane transformation for light olefins production over SAPO-34 with different Si content

SAPO-34s with low and high Si content were synthesized and characterized by XRD, XRF, NMR, FTIR and TG-DSC. Different Si content generated no apparent difference in XRD patterns and 31P and 27Al MAS NMR spectra. The Si coordination states studied by 29Si MAS NMR predicted the acidity difference caused by Si incorporation. The absorbance of bridge hydroxyls in FTIR spectra also showed the amount of active sites differed with Si content. Both of the two samples were employed as catalysts in the transformation of chloromethane to light olefins and proved to be very selective catalysts for light olefins production. The influences of Si content on chloromethane conversion and product selectivity were investigated in details. Coke amount and coke species were determined by TG-DSC and FTIR. Coke formation was related to the Si content of SAPO-34 and corresponded to the catalytic performance.

BEA and MOR as additives for light olefins production

Abstract The use of MFI-based additives in the fluid catalytic cracking (FCC) process in order to increase both – the production of light olefins and gasoline octane number – has been commercially proven. It is well known that impregnation by phosphorus increases the stability of aluminum atoms of H-MFI zeolite framework, resulting in higher yields of desired products. This paper discusses the possibility of combining either beta (BEA) or mordenite (MOR) zeolites – before and after treatment – with phosphoric acid (P/Al ratio of 1) with the conventional MFI-based additive. Zeolite samples were characterized by nitrogen adsorption, X-ray diffraction (XRD) and 27 Al and 31 P solid state NMR before and after hydrothermal treatment. Such treatment was responsible for decreases in zeolite surface area, crystallinity and also in the number of framework tetrahedral aluminum species of all samples. After impregnation with phosphoric acid and hydrothermal treatment, besides other species, both H-MOR/P/St and H-BEA/P/St presented resonance signals at 38 and −30 ppm at the 27 Al and 31 P MAS NMR spectra, respectively, which can be attributed to tetrahedral aluminum and phosphorus in AlPO's-like crystalline structures. After being mixed with an equilibrium FCC catalyst, the laboratory performance of the different additives was investigated using a gasoil feedstock and a fixed-bed micro activity test unit. Similarly to what was previously reported for H-MFI/P/St, the phosphoric acid treatment improved the performance of H-MOR/P/St and H-BEA/P/St zeolites with an expressive increase in lighter products yields in detriment of naphtha. The results suggest that, besides classical tetrahedral aluminum in the framework (Al tet-f ), other aluminum species also take part in the improvement of the zeolites performance.

Stabilization effect of phosphorus on steamed H-MFI zeolites

Abstract The effect of the introduction of phosphorus on H-MFI zeolite before and after hydrothermal treatment was studied. The samples were characterized by XRF, nitrogen adsorption, 27Al and 31P MAS NMR, n-propylamine temperature-programmed decomposition, n-hexane cracking and vacuum gasoil cracking. Results showed that P stabilizes the MFI zeolite structure by preventing the segregation of the framework Al atoms during the steaming treatment. Although there is an optimum phosphorus content, its effect on the selectivity towards light olefins will depend on the severity of the steaming treatment, i.e., with more severe treatment the stabilization is more evident. NMR results evidenced the presence of several types of aluminium and phosphorus species. Besides the classical framework tetracoordinated Al, which is the main responsible for the acidity of the samples, another tetrahedral aluminium probably in a distorted environment also seems to be active in n-hexane cracking, besides favouring the light olefins production during gasoil cracking.

Chloromethane Conversion to Higher Hydrocarbons over Zeolites and SAPOs

Chloromethane transformations were carried out over zeolites and SAPOs and the conversion and product distribution differed from the porous structure and acidity of the catalysts. Chloromethane was mainly transferred to higher hydrocarbons in gasoline range over most of zeolite catalysts, while SAPOs molecular sieves, SAPO-34 and SAPO-5, showed high selectivity for light olefins production, such as ethylene, propylene and butenes. TG analysis was used to study the coke formation during the transformation and the acid difference of the catalysts was evidenced by Temperature programmed desorption of ammonia. HZSM-5, with high activity and less coke formation, was proved to be a potential catalyst for hydrocarbons production from chloromethane conversion. It is of particular interest that SAPO-34 gave an excellent performance in light olefins production from chloromethane transformation, which may be attributed to the shape selectivity and medium strong acidity of SAPO-34.

CrHZSM-5 Zeolites – Highly Efficient Catalysts for Catalytic Cracking of Isobutane to Produce Light Olefins

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Cr-loading on the catalytic performances of CrHZSM-5 catalysts for the cracking of isobutane was also studied. The results suggested that when the loading of Cr in the CrHZSM-5 catalysts was less than 0.038 mmol/g Cr, especially at Cr loading of 0.004 mmol/g, both the reactivity of isobutane cracking and the selectivity to light olefins of CrHZSM-5 samples were greatly enhanced compared with the unpromoted HZSM-5, and very high yields of olefins(C2+C3) and ethylene were obtained. For instance, the yield of olefins(C2+C3) and ethylene reached 56.1% and 30.8%, respectively, at 625 °C when 0.004 mmol/g Cr was loaded on HZSM-5 sample.

Physico-chemical properties of mixed molybdenum and cerium oxides supported on silica–alumina and their use as catalysts in the thermal-catalytic cracking (TCC) of n-hexane

Mixed oxides, MoO 3–CeO 2, were being used as catalysts for the cracking (TCC) of liquid hydrocarbon feedstocks. The dispersion and interactions of MoO 3, CeO 2 and mixtures thereof impregnated into the silica–alumina surface were investigated using several techniques, which included X-ray diffraction (XRD) and laser Raman spectroscopy (LRS). The loadings and the chemical states of metal oxides incorporated separately had significant effects on the catalytic activities of the resulting monocomponent catalysts. Addition of cerium to molybdenum had a favorable effect on the production of light olefins in the TCC of n-hexane up to a certain level of cerium loading. In fact, high loadings of molybdenum and/or cerium favored the formation of aromatics, instead. The catalytic performance of the bicomponent catalysts also depended significantly on the incorporation methods. It was found that the co-impregnation of MoO 3 and CeO 2, which led to the highest production of light olefins, corresponded to the formation of (surface) cerium molybdate to the highest extent. On the other hand, the catalysts prepared by the two-step impregnation methods (sequential and reverse sequential impregnation) showed much lower catalytic performance due to low Mo–Ce interactions as suggested by an important segregation of the active phases, mostly MoO 3. The sequence of catalytic performance (to the desired products, i.e. light olefins) fully coincided with that of the dispersion of molybdate species on the support surface.

The Thermocatalytic Cracking Process for the Production of Light Olefins and Transportation Fuels from Gas Oils

The thermocatalytic cracking (TCC) process, which can selectively produce light olefins (mostly, ethylene and propylene for the petrochemical industry) and transportation fuels (gasoline and diesel fuel), combines the effects of thermal and catalytic cracking reactions. The TCC catalysts consist mainly of mixed metal oxides supported on a high-surface area – thermally stabilized alumina. The best TCC catalyst formulation includes a co-catalyst, which provides the main catalyst component with active hydrogen species formed from hydrogen and other hydrocarbons, particularly methane, produced mainly by thermal cracking. The interparticular interactions of these hydrogen spilt-over species can occur because these species can be easily transferred from one particle to the other through the newly formed pore connections

Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: Influence of lapse time of reaction

Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 °C) and high (400 °C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 °C was firstly aromatic products and then olefin products, while at 400 °C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 °C) and 83 min (at 400 °C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was concluded that the characteristics of liquid product on the pyrolysis of plastic mixtures were strongly influenced by lapse time of reaction and degradation temperature.

Production of Light Olefins by Catalytic Pyrolysis of Heavy Oil

Catalytic pyrolysis is a promising technology for the production of light olefins. In this article, current advances in catalytic pyrolysis with respect to pyrolysis catalysts, technologies and reaction mechanisms are summarized. An experimental laboratory method, based on a confined fluidized bed reactor, has been used to study catalytic pyrolysis of Chinese Daqing atmospheric residue over three different catalysts: LCM-5, CEP-1, and RSCC-29. Analysis of pyrolyzed gases shows that product yields are strongly dependent on catalyst type. The optimal operating conditions vary with catalyst type, but in each case, the yields of total light olefins show maxima with increasing temperature. Pyrolyzed liquids are primarily aromatic components, indicating that the degree of catalytic pyrolysis is very deep. Hydrogen balance analysis shows that the catalytic pyrolysis of heavy oil is capable of producing light olefins with high hydrogen contents.

Highly efficient catalytic conversion of chloromethane to light olefins over HSAPO-34 as studied by catalytic testing and in situ FTIR

The catalytic conversion of chloromethane over HSAPO-34 was followed by in situ Fourier transform infrared (FTIR) spectroscopy and catalytic testing. Our detailed IR investigation allowed the identification of the active sites and the adsorbed species. HSAPO-34 has high activity and selectivity for the production of light olefins. The FTIR results demonstrated that the conversion starts at 350 °C with the formation of alkoxy groups as intermediate products. On adsorption and conversion of chloromethane, three distinct shifts of OH bands associated with the Si(OH)Al acidic sites were observed, attributed to the interaction between Si(OH)Al with CH 3Cl, HCl and C C groups. In the 350–500 °C temperature range, chloromethane is converted to ethylene, propylene, and butylenes with 70–80% selectivity. Increasing reaction temperature increases conversion and enhances the yield of lighter olefins. The detailed FTIR study of chloromethane conversion at 450 °C at different system chloromethane loadings reveals that increasing system CH 3Cl loading increased the conversion rate. This is attributed to the participation of gas-phase chloromethane molecules with adsorbed species enhancing the reaction rate, while at lower chloromethane loadings, the reactions may just occur between the adsorbed species. The IR studies also reveal the reversible breaking of Al O P bonds on adsorption of HCl, a main product of the reaction, to generate large amounts of P OH groups. The Al O P bonding was restored after removal of HCl by evacuation at 150 °C. These IR observations combined with the catalytic test results allow us to propose a realistic reaction mechanism.

Study of Mn incorporation into SAPO framework: Synthesis, characterization and catalysis in chloromethane conversion to light olefins

MnAPSO-34 molecular sieve has been synthesized with triethylamine as the template, characterized with XRD, XRF, 31P, 27Al and 29Si NMR and FT-IR techniques and compared with SAPO-34. The template decomposition and removal have been investigated with TG–DTG–DSC coupled with mass spectrometer. Mn incorporation generates a negligible difference on the chemical shift in 31P and 27Al MAS NMR, while an effect on the intensity of resonance peaks is revealed. 29Si MAS NMR study has demonstrated that Mn incorporation favors the Si island formation, which may give rise to the stronger acidic sites. The thermal analysis (TG–DSC) on template removal in a diluted oxygen atmosphere, leading to the formation of CO 2, NO and H 2O, showed, besides a low temperature endothermic weight loss due to the desorption of water, two weight losses (200–400 and 400–600 °C) for SAPO-34 and MnAPSO-34, suggesting two different chemical location environments of template molecules in these two molecular sieves. The quantity of template removed at higher temperature range is much higher in MnAPSO-34, indicating stronger template–framework interaction and stronger acidity after calcination. The acid difference caused by Mn incorporation has also been evidenced by ammonia adsorption evaluated by FT-IR. Chloromethane transformation was carried out over MnAPSO-34 and SAPO-34 and the catalytic performance showed that both molecular sieves are very active and selective catalyst for light olefins production. MnAPSO-34 demonstrated higher activity and light olefins selectivity.

La (1− y) Co 0.4Fe 0.6O 3− δ perovskite oxides as catalysts for Fischer–Tropsch synthesis

A previous study of LaCo x Fe (1− x) O 3 perovskites demonstrated the potential of such materials to produce light olefins from syngas by Fischer–Tropsch synthesis. The partial reduction of LaCo 0.4Fe 0.6O 3 generates small Co 0 particles in interaction with a deficient perovskite. However, the stability of the perovskite limits the amount of metal to 2% in weight. To increase the amount of active phase (metal) that can be extracted from the oxide precursor by reduction, we attempted to synthesize A-site deficient perovskites. La (1− y) Co 0.4Fe 0.6O 3− δ series prepared by a sol–gel-like route revealed to be, instead of expected A-site deficient oxides, γ-Fe 2O 3/LaCo z Fe (1− z) O 3 composites. Magnetic nanocores of γ-Fe 2O 3 are surrounded by a perovskite-type shell. The epitaxial growth of the perovskite phase on the cubic iron oxides drives its crystallization toward the same cubic system. The characterization of La (1− y) Co 0.4Fe 0.6O 3− δ oxides are presented, and the structural hypotheses are discussed. The reducibility of such oxides is studied by thermoprogrammed reduction and Mössbauer experiments, and the formulae of the stable partially reduced materials are determined. These materials are composed of an equimolar Co–Fe alloy on a cubic perovskite enriched in iron with respect to that of the fresh catalyst. The γ-Fe 2O 3 disappear; one part of the Fe 3+ cations is reduced into Fe 0 in the alloy, and the other part of the Fe 3+ “replaces” a part of the Co 3+ cations of the perovskite, which also reduce into Co 0 in the alloy. After partial reduction, the reactivity of these oxides in Fischer–Tropsch synthesis is evaluated. Their efficiency to produce light olefins and their stability over 300 h of test is demonstrated.

New route for light olefins production from chloromethane over HSAPO-34 molecular sieve

HSAPO-34 molecular sieve was employed in chloromethane conversion and showed high performance in activity and selectivity in production of light olefins. Our detailed IR investigation allowed the identification of the active sites and the adsorbed species and demonstrated that the conversion started from 350 °C with alkoxy group as the intermediate. The fixed-bed catalytic testing evidenced that in the range of 350–500 °C, 70–80% of chloromethane was transferred to ethylene, propylene and butenes. Increasing reaction temperature favors the conversion and enhances the yield of lighter olefins. A very important reversible phenomenon, the breaking of Al O P bonds upon adsorption of HCl, a main product of reaction to generate a large amount of P OH groups and the recovery of Al O P upon removal of HCl was revealed.

Olefins from conventional and heavy feedstocks: Energy use in steam cracking and alternative processes

Steam cracking for the production of light olefins, such as ethylene and propylene, is the single most energy-consuming process in the chemical industry. This paper reviews conventional steam cracking and innovative olefin technologies in terms of energy efficiency. It is found that the pyrolysis section of a naphtha steam cracker alone consumes approximately 65% of the total process energy and approximately 75% of the total exergy loss. A family portrait of olefin technologies by feedstocks is drawn to search for alternatives. An overview of state-of-the-art naphtha cracking technologies shows that approximately 20% savings on the current average process energy use are possible. Advanced naphtha cracking technologies in the pyrolysis section, such as advanced coil and furnace materials, could together lead to up to approximately 20% savings on the process energy use by state-of-the-art technologies. Improvements in the compression and separation sections could together lead to up to approximately 15% savings. Alternative processes, i.e. catalytic olefin technologies, can save up to approximately 20%.

ROLE OF WATER IN THE KINETIC MODELING OF METHANOL TRANSFORMATION INTO HYDROCARBONS ON HZSM-5 ZEOLITE

The attenuating effect of reaction-medium water (feed and/or reaction product) on the kinetics of the steps of methanol transformation into hydrocarbons on a HZSM-5 zeolite catalyst was studied by means of a kinetic model. In this model, the effect of water was quantified in all the steps of the kinetic scheme by means of a kinetic parameter, which is constant with temperature under the conditions of the MTG process. At low temperature, under conditions in which only methanol dehydration occurs, the kinetics of this reaction is attenuated by the presence of water, and the coefficient that quantifies the attenuation decreases as temperature is increased. In addition to considering the effect of water content in the reaction medium, another innovation of the kinetic model proposed, compared to those proposed in the literature consisting of lumps, is the fact that the higher reactivity of dimethyl ether over methanol is taken into account. A step of cracking of gasoline lump hydrocarbons to produce light olefins (ethene and propene) was also taken into account. The kinetic model proposed was verified by using the results obtained in an integral isothermal fixed bed reactor, in the 573–723 K range, for an ample range of space time values. The results revealed that the effect of water is due to its adsorption on the active sites by competition with the intermediate compounds of the kinetic scheme.

Different process schemes for converting light straight run and fluid catalytic cracking naphthas in a FCC unit for maximum propylene production

Light straight run (LSR) and fluid catalytic cracking (FCCN) naphthas were cracked in a transported bed reactor (MicroDowner) and in a fixed bed reactor (MAT) over a commercial Y zeolite based catalyst, over a commercial ZSM-5 zeolite based additive, and over a mixture of both at selected conditions. Based on the mechanisms through which naphtha hydrocarbons are converted, we evaluated the best alternatives for processing these streams to produce light olefins and/or to reduce olefins content in commercial gasoline. The experimental set-up allowed us to simulate the cracking behaviour of the different naphtha streams in a fluid catalytic cracking (FCC) unit by different processing schemes. Results indicate that LSR only cracks at high severity, yielding large amounts of dry gas. Despite its high olefins content, FCCN practically does not crack when it is fed together with gas oil feed. When cracking FCCN alone at typical gas oil cracking conditions, olefins are transformed preferentially into naphtha-range isoparaffins and aromatics, and when cracking FCCN at high severity, olefins are transformed preferentially into propylene and butylenes. Finally, cracking naphtha in the stripper produces some propylene and increases the aromatics in the remaining gasoline.

04/00661 Performance of the sasol SPD naphtha as steam cracking feedstock: Dancuar, L. P. et al. Preprints — American Chemical Society, Division of Petroleum Chemistry, 2003, 48, (2), 132–138

The indirect conversion of natural gas to liquid products via the Fischer-Tropsch synthesis is starting to become a favoured Gas-to-Liquids (GTL) process option. One of the GTL options is the Sasol Slurry Phase Distillate (SPD) process. It comprises three steps: first natural gas is reformed to syngas, a mixture of hydrogen and carbon monoxide. Subsequently this syngas is reacted via the Fischer-Tropsch reaction into a highly paraffinic synthetic crude. Finally, this is hydroprocessed to commercial product specifications. Many studies have been published on the performance of the Sasol SPD Diesel. However, this has not been the case for the Sasol SPD Naphtha, a product that has been regarded as an excellent steam cracking feedstock for the production of light olefins. This statement has been validated after a series of pilot scale steam cracking runs. The objectives of the program included quantifying the performance at different steam cracking severities and estimating the cracking coil coking trend. The observed performance exceeded expectations. Under commercial processing conditions the Sasol PD Naphtha should produce better olefin yields and longer cracker run lengths than conventional petrochemical naphthas. This performance is analysed and compared with that of petroleum naphthas.