Production Of Light Olefins Research Articles

Effect of preparation and operation conditions on the catalytic performance of cobalt-based catalysts for light olefins production

Cobalt-based catalysts were prepared by precipitation method. This research investigated the effects of different supports cobalt loading, promoters, loading of promoters and calcination conditions on the catalytic performance of cobalt catalysts for Fisher–Tropsch synthesis (FTS). It was found that the catalyst containing 40 wt.% Co/TiO 2 promoted with 6 wt.% Zn was an optimal catalyst for the conversion of synthesis gas to hydrocarbons especially light olefins. The activity and selectivity of optimal catalyst were studied in different operational conditions. The results showed that the best operational conditions were the H 2/CO = 2/1 molar feed ratio at 240 °C and GHSV = 1100 h −1 under atmospheric pressure. Characterization of catalysts were carried out by using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), hydrogen temperature program reduction (H 2-TPR), N 2 physisorption measurements such as Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods.

Synthesis, characterization and catalytic performance of nanosized iron-cobalt catalysts for light olefins production

Nanosized Fe-Co catalysts were prepared by co-precipitation method and studied for the conversion of synthesis gas to light olefins. In particular, the effects of a range of preparation variables such as Co/Fe molar ratios of the precipitation solution, pH value of precipitate, temperature of precipitation, promoters and loading of optimum promoter on the structure and catalytic performance are investigated. The optimal nano catalyst for light olefins (C 2–C 4) production was obtained over the catalyst with Co/Fe molar ratio of 3/1 which promoted with 2 wt% K. The results show that the best operational conditions were GHSV = 2200 h −1 (H 2/CO = 2/1) at 260 °C under atmospheric pressure. Characterization of catalysts were carried out using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 physisorption measurements such as Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods.

Can We Afford to Waste Carbon Dioxide? Carbon Dioxide as a Valuable Source of Carbon for the Production of Light Olefins

Concerns about climate change have increased the amount of activity on carbon capture and sequestration (CCS) as one of the solutions to the problem of rising levels of CO(2) in the troposphere, while the reuse of CO(2) (carbon capture and recycling; CCR) has only recently received more attention. CCR is focused on the possibility of using CO(2) as a cheap (or even negative-value) raw material. This Concept paper analyzes this possibility from a different perspective: In a sustainable vision, can we afford to waste CO(2) as a source of carbon in a changing world faced with a fast depletion of natural carbon sources and in need of a low-carbon, resource-efficient economy? One of the points emerging from this discussion concerns the use of CO(2) for the production of olefins (substituting into or integrating with current energy-intensive methodologies that start from oil or syngas from other fossil fuel resources) if H(2) from renewable resources were available at competitive costs. This offers an opportunity to accelerate the introduction of renewable energy into the chemical production chain, and thus to improve resource efficiency in this important manufacturing sector.

Catalytic cracking of C5 raffinate to light olefins over NaOH-treated ZSM-5

A series of ZSM-5 catalysts (ZSM-5 (X)) treated with different NaOH concentration (X = 0, 0.05, 0.1, and 0.2 M) were prepared for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of NaOH concentration on their physicochemical properties and catalytic activity was investigated. It was found that textural and physicochemical properties of ZSM-5 (X) catalysts were strongly influenced by the NaOH concentration. Mesopore volume of ZSM-5 (X) catalysts increased with increasing NaOH concentration, while acidity of the catalysts decreased with increasing NaOH concentration. Conversion of C5 raffinate and yield for light olefins (ethylene and propylene) showed the volcano-shaped curves with respect to NaOH concentration (X). This implies that NaOH treatment of ZSM-5 was an efficient method to produce light olefins through catalytic cracking C5 raffinate, and that optimal NaOH concentration was required for maximum production of light olefins. Among the catalysts tested, ZSM-5 (0.05) catalyst showed the best catalytic performance due to its favorable porosity and acidity.

Selective conversion of bio-oil to light olefins: Controlling catalytic cracking for maximum olefins

Light olefins are the basic building blocks for the petrochemical industry. In this work, selective production of light olefins from catalytic cracking of bio-oil was performed by using the La/HZSM-5 catalyst. With a nearly complete conversion of bio-oil, the maximum yield reached 0.28±0.02kg olefins/(kg bio-oil), which was close to that from methanol. Addition of La into zeolite efficiently changed the total acid amount of HZSM-5, especially the acid distribution among the strong, medium and weak acid sites. A moderate increase of the number of the medium acid sites effectively enhanced the olefins selectivity and improved the catalyst stability. The comparison between the catalytic cracking and pyrolysis of bio-oil was studied. The mechanism of the conversion of bio-oil to light olefins was also discussed.

Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5

The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 °C, 44 hr−1 and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.

Biomass to olefins: Cracking of renewable naphtha

An alternative route for the production of light olefins is proposed starting from low value and waste fats, greases and other renewable fractions. The first step catalytically converts triglycerides and/or fatty acids from bio oils to a high quality paraffinic diesel or jet fuel and renewable naphtha. GC × GC–TOF-MS and GC × GC–FID characterization of the renewable naphtha showed that it mainly consists of n-paraffins (32.6 wt%) and iso-paraffins (60 wt%), with only small amounts of aromatics (0.8 wt%), naphthenics (6.3 wt%) and olefinics (0.3 wt%). No remaining oxygenates are measured, making it a potentially attractive feed for the production of ethylene. Steam cracking of this renewable naphtha in a pilot plant revealed that high light olefin yields can be obtained (ethylene yield of 31 wt% and a propylene yield of 17.5 wt%), while the amount of pyrolysis gasoline (15 wt%) and pyrolysis fuel oil (<1 wt%) produced remains small. An experimental coking study further confirmed the attractive character of this feed. Run length simulations show that higher run lengths can be expected in comparison with the typically used naphtha fractions from fossil resources.

The fluidized-bed catalytic cracking unit building its future environment

Fluidized-bed catalytic cracking (FCC) has been considered as one of the largest catalytic process in the world. FCC is the name for a complex process unit that cracks long molecules from gas oils and residua into added value shorter fuel compounds; additionally, this process can be used to produce important petrochemical precursors, such as propylenes. Although historically FCC has been used to optimise production of light cycle oils, gasoline and olefins, nowadays is convenient to revisit its mission. In order to integrate FCC process inside current development and environment respect, it is necessary to see it as a very flexible process. This flexibility will require deeper knowledge about environmental impact of process operation and production objectives, transport phenomena and catalytic reactions taking place inside the riser, the main reactor of the FCC converter, and energy balance integrating energy recovered/generated in the regenerator. This work is devoted to briefly review some propositions about the use of FCC converters and how these aspects demand knowledge of riser reactors, change in the methodology to estimate effective reaction rates (consequence of variation of kinetic and transport phenomena, at catalyst scale and along the riser) and catalyst activity, as well as control actions and its effect on the energy balance of the converter; operation and environmental concerns surrounding this process are addressed. Finally, it tries to draw attention on some facts that need to be analysed in order to ensure the sustainable development of this important process in the short future.

Cracking Performance and Feed Characterization Study of Catalytic Pyrolysis for Light Olefin Production

The catalytic pyrolysis of heavy oils, gas oils, cracked diesel and gasoline fractions was investigated in a confined fluidized-bed reactor. The feed with a high H/C atomic ratio and low aromaticity showed good cracking performance, high feed conversion, and high yield and selectivity of total light olefins (i.e., ethene, propene, and butene). The cracked diesel and gasoline fractions with a low H/C atomic ratio and high aromaticity showed poor secondary cracking performance. A characterization parameter (KCP) was proposed to characterize the cracking performance of various feedstocks. The yield of total light olefins increased with an increase in KCP, despite the catalytic or thermal pyrolysis. KCP could be used as a criterion to evaluate the cracking performance of a feed for the production of light olefins. The cracking performance of a feed was considered desirable for KCP above 3.6 and undesirable for KCP below 2.8. Besides KCP, the United States Bureau of Mineral Correlation Index (BMCI) was also su...

Preparation and Characterization of CoMn/TiO2 Catalysts for Production of Light Olefins

A series of x(Co, Mn)/TiO 2 catalysts (x=2-12wt.%) containing 25%Co and 75%Mn were prepared by the co-impregnation method. All prepared catalysts have been tested in Fischer- Tropsch synthesis for production of C 2-C4 olefins. It was found that the catalyst containing 8wt.%(Co,Mn)/TiO 2 is an optimal catalyst for production of C 2-C4 olefins. The effect of operation conditions such as the H 2/CO molar feed ratios, temperature, Gas Hourly Space Velocity (GHSV) and total reaction pressure on the catalytic performance of optimal catalyst was investigated. Characterizations of both precursors and catalysts were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC).

Production of Liquid Biofuels in a Fluid Catalytic Cracking Pilot-Plant Unit Using Waxes Produced from a Biomass-to-Liquid (BTL) Process

The production of synthetic transportation fuels from lignocellulosic biomass feedstocks through a biomass-to-liquid (BTL) process based on Fischer−Tropsch (F−T) synthesis is today of increasingly importance. Depending on the operating conditions of the F−T process, heavy waxy hydrocarbons could be produced (waxes) with almost zero aromatics and sulfur. The purpose of this study is the investigation of a catalytic cracking process for the upgrading of these BTL waxes in order to produce high-quality biofuels. In this work, a F−T Wax with hydrocarbons up to C40 was used, while the fluid catalytic cracking (FCC) experiments were carried out in an FCC pilot-plant unit operating in a full circulation mode with continuous catalyst regeneration. Three different catalysts, cofeeding options, and various operating conditions were investigated in the pilot plant. Our results showed that the F−T Wax is very crackable and conversions in the range of 70−90 wt % (on the feed) can be achieved with all catalysts tested. Catalyst type and cracking temperature also play an important role in improving the selectivity of specific FCC products. The process gives high gasoline yields with very low aromatics, low light cycle oil yields, and very low coke yields. The use of a ZSM-5 catalyst offers also significant advantages for the production of light olefins, while this catalyst strongly influences the gasoline composition.

Carbon modified Fe–Mn–K catalyst for the synthesis of light olefins from CO hydrogenation

A novel carbon modified Fe–Mn–K catalyst for light olefin synthesis from CO hydrogenation was prepared by the sol–gel method. The effect of carbon contents on the structure and performance of the catalysts was investigated. With the incorporation of carbon, the catalysts showed much different morphology from that prepared by co-precipitation. At the carbon contents between 0.23 and 6.66 wt%, the catalyst particles were around 10 nm while the carbon phase was amorphous. The activity test results indicated that the catalysts (Fe/Mn/K molar ratio = 60/20/1) with carbon modification showed high conversion of CO and selectivity to light olefins with low CH4 selectivity. At the carbon content of 2.43 wt%, the total C2–C4 content in all hydrocarbons and O/P (olefin/paraffin) in the C2–C4 fraction was 49 wt% and 4.89, respectively. Furthermore, when the K content in the catalyst was reduced by half, the C2–C4 olefin yield raised from 60 to 71 g/Nm3 syngas. The formation of carbon provided a more hydrophobic surface, which inhibited the water gas shift reaction (WGSR) and caused a decrease in CO2 selectivity. The dispersion of carbon favored the formation and stabilization of small particles, and promoted the production of light olefins via suppressing the chain propagation.

Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves

As an alternative to the partial oxidation of methane to synthesis gas followed by methanol synthesis and the subsequent generation of olefins, we have studied the production of light olefins (ethylene and propylene) from the reaction of methyl bromide over various modified microporous silico-aluminophosphate molecular-sieve catalysts with an emphasis on SAPO-34. Some comparisons of methyl halides and methanol as reaction intermediates in their conversion to olefins are presented. Increasing the ratio of Si/Al and incorporation of Co into the catalyst framework improved the methyl bromide yield of light olefins over that obtained using standard SAPO-34.

Alkali-treatment of ZSM-5 zeolites with different SiO2/Al2O3 ratios and light olefin production by heavy oil cracking

Four kinds of ZSM-5 zeolites with different SiO2/Al2O3 ratios are alkali-treated in 0.2M NaOH solution for 300min at 363K. Changes to the compositions, morphologies, pore sizes, and distributions of the zeolites are compared before and after alkali-treatment. The changes observed are largely influenced by the SiO2/Al2O3 ratios with which the zeolites are synthesized. A possible mechanism of desilication during alkali-treatment is proposed. The SiO2/Al2O3 ratio of zeolites is found to influence the yield of light olefins that use heavy oil as feedstock. Alkali-treated ZSM-5 zeolites produce higher yields of light olefins compared to either untreated zeolites or the industry catalyst CEP-1. It is believed that alkali-treatment introduces mesopores to the zeolites and improves their catalytic cracking ability. ZSM-5 zeolites with SiO2/Al2O3 ratios of 50 also present superior selectivity toward light olefins because of their optimized hierarchical pores.

Full Theoretical Cycle for both Ethene and Propene Formation during Methanol‐to‐Olefin Conversion in H‐ZSM‐5

AbstractThe methanol‐to‐olefin (MTO) process, catalyzed by acidic zeolites such as H‐ZSM‐5, provides an increasingly important alternative to the production of light olefins from crude oil. However, the various mechanistic proposals for methanol‐to‐olefin conversion have been strongly disputed for the past several decades. This work provides theoretical evidence that the experimentally suggested ‘alkene cycle’, part of a co‐catalytic hydrocarbon pool, offers a viable path to the production of both propene and ethene, in stark contrast to the often‐ proposed direct mechanisms. This specific proposal hinges on repeated methylation reactions of alkenes, starting from propene, which occur easily within the zeolite environment. Subsequent cracking steps regenerate the original propene molecule, while also forming new propene and ethene molecules as primary products. Because the host framework stabilizes intermediate carbenium ions, isomerization and deprotonation reactions are extremely fast. Combined with earlier joint experimental and theoretical work on polymethylbenzenes as active hydrocarbon pool species, it is clear that, in zeolite H‐ZSM‐5, multiple parallel and interlinked routes operate on a competitive basis.

Enhancing the Production of Light Olefins by Catalytic Cracking of FCC Naphtha over Mesoporous ZSM-5 Catalyst

The enhanced production of light olefins from the catalytic cracking of FCC naphtha was investigated over a mesoporous ZSM-5 (Meso-Z) catalyst. The effects of acidity and pore structure on conversion, yields and selectivity to light olefins were studied in microactivity test (MAT) unit at 600 °C and different catalyst-to-naphtha (C/N) ratios. The catalytic performance of Meso-Z catalyst was compared with three conventional ZSM-5 catalysts having different SiO2/Al2O3 (Si/Al) ratios of 22 (Z-22), 27 (Z-27) and 150 (Z-150). The yields of propylene (16 wt%) and ethylene (10 wt%) were significantly higher for Meso-Z compared with the conventional ZSM-5 catalysts. Almost 90% of the olefins in the FCC naphtha feed were converted to lighter olefins, mostly propylene. The aromatics fraction in cracked naphtha almost doubled in all catalysts indicating some level of aromatization activity. The enhanced production of light olefins for Meso-Z is attributed to its small crystals that suppressed secondary and hydrogen transfer reactions and to its mesopores that offered easier transport and access to active sites.

Performance and characterization of iron-nickel catalysts for light olefin production

A series of x (Fe, Ni)/Al 2O 3 catalysts ( x = 2-12 wt%) were prepared using incipient wetness method and studied for the conversion of synthesis gas to light olefins. 6 wt%(Fe, Ni)/Al 2O 3 catalyst was found to be the optimal catalyst for the production of C 2-C 4 olefins. The effects of calcination behaviors and operational conditions on the catalytic performance of the optimal catalyst were investigated. The best operational conditions were molar feed ratio H 2/CO = 2/1, T = 260 °C, gas hourly space velocity (GHSV) = 2600 h −1 and the pressure of 3 bar. Characterizations of both precursors and catalysts were carried out using X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscopy (SEM), N 2-adsorption-desorption measurement, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).

Highly Effective F-Modified HZSM-5 Catalysts for the Cracking of Naphtha To Produce Light Olefins

A series of fluorinated HZSM-5 zeolites (F/HZSM-5) were prepared by immersing the zeolites with different concentrations of NH4F solution, and their performances for the catalytic cracking of naphtha to produce light olefins were investigated. The results indicated that F-modified HZSM-5 zeolites are effective catalysts for the cracking of naphtha to light olefins. At the temperature of 600 °C, the yields of propene and ethene were achieved at 36.4 and 20.2%, which were 7.3 and 4.3% higher than those over parent HZSM-5 zeolite, respectively. The physicochemical features of F/HZSM-5 catalysts were characterized by means of X-ray diffraction (XRD), Brunauer−Emmett−Teller (BET), temperature-programmed desorption of ammonia (NH3-TPD), Fourier transform infrared (FTIR) spectra of adsorbed pyridine, etc. The results indicated that fluorine (F) modification not only regulates the pore characteristics of the HZSM-5 zeolites but also modulates the amount of acid sites, especially the amount of Bronsted (B) acid. C...

Catalytic Cracking of Lower-Valued Hydrocarbons for Producing Light Olefins

A number of important chemicals are made from light olefins such as propylene and ethylene, and it is expected that market demand for these light olefins will continue to grow at 4–5% annually, and the average overall growth of propylene will be about 1% higher than that of ethylene. From the viewpoint of supply of feedstock and demand of light olefins, it is anticipated that the thermal cracking process of naphtha will be gradually transformed to a catalytic process such as ACOTM that can efficiently produce both ethylene and propylene in high yield. Also, together with primary light olefin production technologies utilizing heavy feedstocks such as DCCTM, and HPFCC, supplementary propylene production technologies utilizing C4–C4 such as SUPERFLEXTM, MOITM, and PROPYLURTM will be applied gradually in commercial production.

Catalytic activity and selectivity of methylbenzenes in HSAPO-34 catalyst for the methanol-to-olefins conversion from first principles

As an attractive alternative to produce light olefins, methanol-to-olefins (MTO) conversion catalyzed by zeolites or zeotype materials was recently proposed to follow a hydrocarbon pool mechanism. In this contribution, the effect of the structure of methylbenzenes (MBs) in the pore of HSAPO-34 catalyst on the MTO activity and selectivity is investigated by first-principle calculations and kinetic simulations. We demonstrate that MBs with five or six methyl groups are not more active than those with fewer methyl groups. Propene is intrinsically more favorable than ethene when the reaction is not diffusion limited based on the side-chain hydrocarbon pool mechanism. Our theoretical results are consistent with some experimental observations and can be rationalized based on the shape selectivity of key reaction intermediates and transition states in the pore of catalyst.