Steam Cracking Of Hydrocarbons Research Articles

Optimized separation of C2H2 from binary mixtures of C2H2/CO2 and C2H2/C2H4 by coordinative copper(I) metal nodes modified from HKUST-1

Acetylene (C2H2), an industrially important gas, is produced by steam cracking of hydrocarbons and inevitably contains traces of ethylene (C2H4) and carbon dioxide (CO2) as impurities. Metal-organic frameworks (MOFs) and further post-modified MOFs are versatile and promising adsorbents for energy-efficient C2H2/C2H4 and C2H2/CO2 separation by selective adsorption of C2H2 compared to energy-consuming conventional methods. Herein, Cu(I) ion generated structures from post-synthetic modification of HKUST-1 are chosen as C2H2 selective sites over both C2H4 and CO2 gases. Protective Cu(I) ions were generated by post-coordinative reduction of Cu(II) nodes of a HKUST-1 using hydroquinone as a reducing agent to create robust C2H2 adsorptive sites. In the metal node reduced to Cu(I) by hydroquinone (HKUST-1-HQ), C2H2 selectivity was enhanced not only for C2H2/CO2 but also C2H2/C2H4 by the presence of the Cu(I) site, by virtue of the copper(I)-alkynyl chemistry. In a breakthrough test, separation of C2H2 and C2H4 did not occur at the coordinatively unsaturated site (HKUST-1), whereas separation capability appeared after monovalent copper was introduced. Enhanced C2H2/CO2 separation was also observed for HKUST-1-HQ. The adsorption behavior of C2H2 (triple bond), C2H4 (double bond), and CO2 (opposite quadruple moment) at the copper(II) open metal site and copper(I) site originating from the same structure respectively is studied to understand the C2H2 gas sorption. In HKUST-1-HQ, the study of four types of possible Cu structures (Nodes II, III, IV, and V) and adsorbates revealed that Node IV is a preferential site over the other three sites, and the CUS site (bare HKUST-1). DFT computational simulation successfully demonstrated that the Node IV type Cu(I) is a plausible adsorption site for C2H2. Overall, HKUST-1-HQ exhibits greater moisture stability, improved selectivity, and repeatability as C2H2 adsorbent.

High-Performance Co-production of Electricity and Light Olefins Enabled by Exsolved NiFe Alloy Nanoparticles from a Double-Perovskite Oxide Anode in Solid Oxide-Ion-Conducting Fuel Cells.

Light olefins (LOs) such as ethylene and propylene are critical feedstocks for many vital chemicals that support our economy and daily life. LOs are currently mass produced via steam cracking of hydrocarbons, which is highly energy intensive and carbon polluting. Efficient, low-emission, and LO-selective conversion technologies are highly desirable. Electrochemical oxidative dehydrogenation of alkanes in oxide-ion-conducting solid oxide fuel cell (SOFC) reactors has been reported in recent years as a promising approach to produce LOs with high efficiency and yield while generating electricity. We report here an electrocatalyst that excels in the co-production. The efficient catalyst is NiFe alloy nanoparticles (NPs) exsolved from a Pr- and Ni-doped double perovskite Sr2Fe1.5Mo0.5O6 (Pr0.8Sr1.2Ni0.2Fe1.3Mo0.5O6-δ, PSNFM) matrix during SOFC operation. We show evidence that Ni is first exsolved, which triggers the following Fe-exsolution, forming the NiFe NP alloy. At the same time as the NiFe exsolution, abundant oxygen vacancies are created at the NiFe/PSNFM interface, which promotes the oxygen mobility for oxidative dehydrogenation of propane (ODHP), coking resistance, and power generation. At 750 °C, the SOFC reactor with the PSNFM catalyst reaches a propane conversion of 71.40% and LO yield of 70.91% under a current density of 0.3 A cm-2 without coking. This level of performance is unmatchable by the current thermal catalytic reactors, demonstrating the great potential of electrochemical reactors for direct hydrocarbon conversion into value-added products.

A Review on the Production of Light Olefins Using Steam Cracking of Hydrocarbons

Light olefins are the main building blocks used in the petrochemical and chemical industries for the production of different components such as polymers, synthetic fibers, rubbers, and plastic materials. Currently, steam cracking of hydrocarbons is the main technology for the production of light olefins. In steam cracking, the pyrolysis of feedstocks occurs in the cracking furnace, where hydrocarbon feed and steam are first mixed and preheated in the convection section and then enter the furnace radiation section to crack to the desired products. This paper summarizes olefin production via the steam cracking process; and the reaction mechanism and cracking furnace are also discussed. The effect of different operating parameters, including temperature, residence time, feedstock composition, and the steam-to-hydrocarbon ratio, are also reviewed.

Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

One of the most challenging aspects of modern day catalysis is the activation of methane. Conventionally, methane is activated with oxidizing agents to produce syngas, which then reacts to produce high value hydrocarbons. This process is energy inefficient. A more economic process is the direct one-step activation of methane to form value-added chemicals. This report focuses on direct conversion of methane to ethylene and ethane. Ethylene and ethane are the most important feedstocks in modern day chemical industries. Conventional process for ethylene production is via steam cracking of hydrocarbons, which is not an energy efficient approach. A direct conversion route from methane to C2 hydrocarbons would be a significant advance and has been widely studied. Mo supported on solid acids have been previously reported to be promising for direct conversion of methane to higher hydrocarbons. Here, a novel catalytic approach is introduced with W, a strong oxidizing agent, doped on sulfated zirconia solid acid and studied for the activation of methane at 650–750 °C. BET, DRIFTS, ammonia TPD, XPS, XRD and SEM–EDX were used to characterize the fresh catalyst. Reaction products are primarily ethylene and ethane, along with trace aromatics. Methane activation along with production of C2 hydrocarbons increased noticeably at higher temperature but deactivated due to carbon deposition as confirmed by TPO.

Greener and sustainable production of bioethylene from bioethanol: current status, opportunities and perspectives

AbstractThe economic value of bioethylene produced from bioethanol dehydration is remarkable due to its extensive usage in the petrochemical industry. Bioethylene is produced through several routes, such as steam cracking of hydrocarbons from fossil fuel and dehydration of bioethanol, which can be produced through fermentation processes using renewable substrates such as glucose and starch. The rise in oil prices, environmental issues due to toxic emissions caused by the combustion of fossil fuel and depletion of fossil fuel resources have led a demand for an alternative pathway to produce green ethylene. One of the abundant alternative renewable sources for bioethanol production is biomass. Bioethanol produced from biomass is alleged to be a competitive alternative to bioethylene production as it is environmentally friendly and economical. In recent years, many studies have investigated catalysts and new reaction engineering pathways to enhance the bioethylene yield and to lower reaction temperature to drive the technology toward economic feasibility and practicality. This paper critically reviews bioethylene production from bioethanol in the presence of different catalysts, reaction conditions and reactor technologies to achieve a higher yield and selectivity of ethylene. Techno-economic and environmental assessments are performed to further development and commercialization. Finally, key issues and perspectives that require utmost attention to facilitate global penetration of technology are highlighted.

Sustainable innovations in steam cracking: CO2 neutral olefin production

Steam cracking of hydrocarbons is and will be the main process to produce light olefins but emits large quantities of CO2. Enhancing heat transfer in the radiation section, using green energy and novel furnace designs will be key to substantially reducing CO2 emissions.

Techno-Economic Analysis of Oxidative Dehydrogenation Options

The world-wide market for light olefins will approach one trillion pounds per year by the year 2020. Light olefins are conventionally produced by the steam cracking of hydrocarbons from ethane to gas oil. This technology is decades old and results in a wide range of by-products, some valuable, some with fuel value, and some requiring waste treatment before disposal. An economic analysis was performed using a cost of production procedure commonly called a required netback analysis. These results were compared with the expected performance of a novel catalytic route with very high selectivity, running at much lower temperatures and similar pressures. The new route uses a mixed metal oxide catalyst in packed tubes with a heat transfer fluid in the reactor shell for heat management. Results indicate that the new route has much lower variable cost, fixed costs and capital recovery reaching shutdown economic level.

Catalytic conversion of light hydrocarbons to propylene over MFI-zeolite/metal-oxide composites

Zeolite-based composite catalysts for producing propylene efficiently by cracking of light hydrocarbons were developed in the present study to meet future demand for propylene and utilize various light hydrocarbons (e.g., light-naphtha, condensates recovered from natural gas and olefinic hydrocarbons obtained from GTL-process). The composite catalysts, consisting of Al-MFI zeolites containing iron and gallium atoms (Fe–Ga–Al-MFI) at optimized ratio and aluminum-oxide binder (Al2O3), were employed for cracking of n-hexane or 1-hexene using fixed-bed-type reactor at around 550 °C. Since the Fe–Ga–Al-MFI zeolites caused acidity suitable for generating light olefins selectively, high propylene yields (18–41 wt%) were obtained by suppressing formation of aromatics at mild temperatures. The present catalyst exhibited high propylene productivity and catalytic stability simultaneously in the steam-cracking of hydrocarbons at suitable steam ratio. Moreover, in the cracking of n-hexane without dilution over the present catalyst, high propylene yields of ca. 18 wt% were maintained for at least 80 h due to its high resistance to coke formation in spite of severe conditions, suggesting that simplified cracking process for on-purpose propylene production from light hydrocarbons is feasible in fixed-bed mode by using the present composite catalysts.

U.S. Shale Gas versus China's Coal as Chemical Feedstock.

T United States and China are pursuing different choices of hydrocarbon feedstock for making chemicals. While the U.S. chemical industry is increasingly utilizing shale gas as feedstock to produce olefins and methanol, China is developing coal-to-olefins and coal-to-methanol. Shale gas chemicals are cheaper and cleaner than coal-based ones. By replacing those high-carbon coal-to-chemicals, the U.S. export of shale gas chemicals will be both profitable and environmentally beneficial. Ethylene, propylene, and methanol are the three most important building blocks in the chemical industry. In 2014, the world consumed about 160 million metric tons of ethylene, 90 million metric tons of propylene, and about 70 million metric tons of methanol. Ethylene and propylene are often grouped together with other alkenes and referred to as olefins. Olefins are made from steam cracking of hydrocarbons, with naphtha as the most common feedstock, followed by ethane and propane. Since the shale revolution, surplus of ethane and propane has triggered an investment boom in ethane crackers and exponential growth of propane/propylene exports. The announced projects are expected to increase the U.S. olefins production capacities by 14 million metric tons by 2020. The cheap and abundant ethane and propane provide the U.S. chemical industries with several competitive advantages. Manufacturing olefins from ethane and propane is cheaper, simpler, consume less energy, and less polluting than naphtha cracking. Meanwhile, China is pursuing the development of coal-toolefins (CTO). China’s 12th five-year plan (2011 to 2015) for olefins industry listed the development of CTO as a top priority. With favorable policies, China’s CTO production capacities have grown from 1.1 million metric tons per year in 2010 to 6.5 in 2014, and are expected to reach 12.4 by 2016. Coal-to-olefins requires high capital investment, complex processes, high energy consumption (therefore high carbon dioxide (CO2) emissions), and high water consumption. Despite the technical disadvantages, China is quickly building a coal-to-olefins industry with favorable government policies. For each metric ton of olefins output, ethane-to-olefins emit about 0.8 t of CO2, naphtha-to-olefins emit about 0.9 t, 1 whereas coal-to-olefins emit about 5.8 t. Similar dichotomy appears in the feedstock choice for methanol in the United States and China. While the U.S. companies are aggressively expanding methanol production from natural gas, China is building coal-to-methanol capacities. In the United States, the announced methanol projects are expected to increase the nationwide methanol production capacity from 1.6 million metric tons in 2013 to over 12 million metric tons per year by 2018, and nearly 30 million metric tons per year by the early 2020s. Because the U.S. domestic consumption of methanol has remained relatively stable at about 6 million metric tons per year, the expansion will transform the United States from a net importer to a major exporter. China is the world’s largest methanol consumer and the major target for U.S. methanol export. In 2014, China consumed about 41 million metric tons of methanol, which account for 55% of global demand. Meanwhile, China has been building a unique coal-tomethanol industry. Many coal-producing regions encourage investments in coal conversion to boost demand for coal. China has already more than enough methanol production capacities to meet its demand, yet it continues to build more. Coal-tomethanol is carbon intensive. Making a metric ton of methanol from coal emits roughly 5.3 t of CO2, while making the same amount from natural gas emits only 1.7 t. The capital investment for a coal-to-methanol plant is roughly twice as much as a methane-to-methanol plant of comparable capacity, while the feedstock costs are comparable. The capital cost of coal-to-olefins is nearly four times of that of an ethane steam cracker, with comparable feedstock costs. In terms of operation and maintenance (O&M) costs, such as catalysts, water, energy, and pollution treatment, coal-tochemicals are all much more expensive than shale gas chemicals (Figure 1). Due to great cost advantage, aggressive expansion of U.S. shale gas chemicals could eventually force some of the Chinese coal-to-chemicals producers out of business, and contribute to carbon mitigation by replacing the high-carbon coal-tochemicals.

Novel Ni–Mg–Al–Ca catalyst for enhanced hydrogen production for the pyrolysis–gasification of a biomass/plastic mixture

A Ni–Mg–Al–Ca catalyst was prepared by a co-precipitation method for hydrogen production from polymeric materials. The prepared catalyst was designed for both the steam cracking of hydrocarbons and for the in situ absorption of CO2 via enhancement of the water–gas shift reaction. The influence of Ca content in the catalyst and catalyst calcination temperature in relation to the pyrolysis–gasification of a wood sawdust/polypropylene mixture was investigated. The highest hydrogen yield of 39.6molH2/g Ni with H2/CO ratio of 1.90 was obtained in the presence of the Ca containing catalyst of molar ratio Ni:Mg:Al:Ca=1:1:1:4, calcined at 500°C. In addition, thermogravimetric and morphology analyses of the reacted catalysts revealed that Ca introduction into the Ni–Mg–Al catalyst prevented the deposition of filamentous carbon on the catalyst surface. Furthermore, all metals were well dispersed in the catalyst after the pyrolysis–gasification process with 20–30nm of NiO sized particles observed after the gasification without significant aggregation.

Coking Resistance of Specialized Coil Materials during Steam Cracking of Sulfur-Free Naphtha

The reactor material strongly affects coke formation during steam cracking of hydrocarbons. Therefore, in the past decade several specialized reactor materials have been developed that have proven to be efficient in reducing coke formation for ethane steam cracking. However, their beneficial anticoking properties are questioned when heavier feedstocks such as naphtha are cracked. Therefore, the effect of the composition of the reactor material has been investigated for ethane and naphtha cracking in an electrobalance setup under industrially relevant conditions. A significant reduction of coke formation is obtained for specialized alloys compared to typical Fe–Cr–Ni heat resistant steels when a sulfur-free naphtha is cracked. A thin layer of alumina on the surface along with manganese chromite provides the highest resistance to coking, as was demonstrated by the SEM and EDX analyses. The decrease in coking rate translates in a run length increase of 50% for a typical naphtha furnace equipped with reactors made out of an Al-enhanced alloy instead of typically applied heat resistant steel.

Ethylene Formation by Catalytic Dehydration of Ethanol with Industrial Considerations.

Ethylene is the primary component in most plastics, making it economically valuable. It is produced primarily by steam-cracking of hydrocarbons, but can alternatively be produced by the dehydration of ethanol, which can be produced from fermentation processes using renewable substrates such as glucose, starch and others. Due to rising oil prices, researchers now look at alternative reactions to produce green ethylene, but the process is far from being as economically competitive as using fossil fuels. Many studies have investigated catalysts and new reaction engineering technologies to increase ethylene yield and to lower reaction temperature, in an effort to make the reaction applicable in industry and most cost-efficient. This paper presents various lab synthesized catalysts, reaction conditions, and reactor technologies that achieved high ethylene yield at reasonable reaction temperatures, and evaluates their practicality in industrial application in comparison with steam-cracking plants. The most promising were found to be a nanoscale catalyst HZSM-5 with 99.7% ethylene selectivity at 240 °C and 630 h lifespan, using a microreactor technology with mechanical vapor recompression, and algae-produced ethanol to make ethylene.

Design Optimization of an LPG Thermal Cracker for Multiple Objectives

Ethylene and propylene, building blocks of the petrochemical industries, are mostly produced by steam cracking of hydrocarbons. In our recent work (Nabavi, Rangaiah, Niaei and Salari, Multiobjective Optimization of an Industrial LPG Thermal Cracker using a First Principles Model, Ind. Eng. Chem. Res. 2009, 48, 9523-9533), operation of an industrial liquefied petroleum gas (LPG) cracker was optimized for several sets of two and three objectives. In this work, optimization of an LPG cracker design is investigated for multiple objectives. The objectives considered are maximization of annual ethylene and propylene production, selectivity and run length, and minimization of severity and total heat duty per year. The elitist non-dominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG is used to solve the multi-objective optimization problems. The results of design optimization for multiple objectives are compared with those for operation optimization.

Design Optimization of an LPG Thermal Cracker for Multiple Objectives

Ethylene and propylene, building blocks of the petrochemical industries, are mostly produced by steam cracking of hydrocarbons. In our recent work (Nabavi, Rangaiah, Niaei and Salari, Multiobjective Optimization of an Industrial LPG Thermal Cracker using a First Principles Model, Ind. Eng. Chem. Res. 2009, 48, 9523-9533), operation of an industrial liquefied petroleum gas (LPG) cracker was optimized for several sets of two and three objectives. In this work, optimization of an LPG cracker design is investigated for multiple objectives. The objectives considered are maximization of annual ethylene and propylene production, selectivity and run length, and minimization of severity and total heat duty per year. The elitist non-dominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG is used to solve the multi-objective optimization problems. The results of design optimization for multiple objectives are compared with those for operation optimization.

Coke Formation in the Transfer Line Exchanger during Steam Cracking of Hydrocarbons

Coke formation under transfer line exchanger conditions, that is, at temperatures from 623 to 873 K and atmospheric pressure, is studied in an electrobalance setup. The coking rate is initially very high (catalytic coking) and drops after a few hours to a constant value. At the studied conditions the observed coking behavior on 15Mo3 alloy pigs can be explained via a catalytic mechanism only, and contributions of the free-radical mechanism and the condensation mechanism are insignificant. Experiments with ethane and naphtha steam cracking effluents and with well-defined reaction mixtures show that the coking rate is independent of the partial pressure of ethene (0−2.7 × 104 Pa), ortho-xylene (0−1.0 × 104 Pa), heavy aromatic hydrocarbons (0−3.0 × 102 Pa), and also 1,3-butadiene (0−2.7 × 104 Pa). The rate of coke deposition depends only on the temperature and the ratio of the partial pressures of water to dihydrogen. The activation energy for initial coke formation was estimated to be ∼90 kJ/mol, a value close to the experimentally determined diffusion energy of carbon in iron.

Influence of Silicon and Silicon/Sulfur-Containing Additives on Coke Formation during Steam Cracking of Hydrocarbons

The influence of the combination of two Si-containing additives, BTMS and TEOS, with DMDS on coke formation during steam cracking has been evaluated both on a laboratory scale and in a pilot plant unit. Under the optimal presulfidation conditions (T = 1023 K, H2O = 20 g h-1, DMDS in H2O = 750 ppm wt, duration = 1 h), the combination of Si pretreatment + presulfidation + continuous addition of 2 ppm wt DMDS results in a decrease in the rate of coke formation up to 40% when hexane is cracked in the lab-scale unit. Under similar conditions in the pilot plant the coke formation is decreased by 70%, while the CO production decreases by more than 90%. Moreover, the suppressing effect on coke formation remains significant even after several coking/decoking cycles. Simulations of an industrial ethane cracker indicate that the application of Si- and S-containing compounds as additives for the suppression of coke formation can potentially double the run length of industrial steam crackers.

Effect of Tube Materials and Special Coating on Coke Deposition in the Steam Cracking of Hydrocarbons

Effect of Tube Materials and Special Coating on Coke Deposition in the Steam Cracking of Hydrocarbons

Influence of Dimethyl Disulfide on Coke Formation during Steam Cracking of Hydrocarbons

The influence of dimethyl disulfide (DMDS), which is widely used as an additive in ethylene plants, on coke formation during the steam cracking of hydrocarbons was investigated in a continuous-flow stirred-tank reactor (CSTR) setup with n-hexane as the feed and in a pilot-plant setup with ethane as the feed. Both of the reactors were made of Incoloy 800HT. Experiments were carried out at conditions relevant to industrial steam crackers. DMDS was applied by presulfidation, continuous addition, and presulfidation followed by continuous addition. Application of DMDS suppresses CO production. The influence of DMDS on coke formation was found to depend on the application method and the amount of DMDS used. SEM examination of the coke samples obtained from the steam cracking of n-hexane indicated that application of DMDS leads to a significant change in the coke morphology. EDX analysis indicated that application of DMDS causes a significant change in the metal content and distribution in both the alloy surface and the coke layers. The mechanism of the influence of DMDS on the coke formation is discussed.

Acetylene eliminated in ethylene processes

A research group at the French Petroleum Institute (IFP) has modified the conventional approach for eliminating acetylene in ethylene processes to good effect. By applying some technology from catalytic olefin production, the researchers have increased ethylene yields, simplified equipment, and lowered the necessary investment. Some acetylene is produced during manufacture of ethylene by steam cracking of hydrocarbons. For high-purity ethylene streams (greater than 99%), the acetylene must be removed. Conventionally, this is done by catalytic hydrogenation of the ethylene, but in a few cases the acetylene is removed by the more expensive method of solvent extraction. For catalytic hydrogenation, placement of the hydrogenation reactor can be critical, according to the IFP group, which includes J. Cosyns, L. Quicke, and P. Sarrazin. If the hydrogenation reactor is placed upstream from the demethanizer, the feed to the reactor will contain light hydrocarbon components and carbon monoxide from the cracking fu...

Heat transfer control of selectivity in acetylene hydrogenation

Ethylene, produced by steam cracking of hydrocarbons, contains acetylene, which is hydrogenated to purify the ethylene for polymerization. The process is low temperature, < 80°C, and catalysts are typically peripherally deposited 0.03% Pd/Al 2O 3. Industrial experience, as well as experimentation at WPI, is that ethane yields are 100 to 150% of the acetylene in the feed at about 70% conversion. The reason for the problem is that catalyst pellet temperatures are far higher than gas stream temperatures, in order to transfer heat generated by reaction through the boundary layer to the gas stream.