Yield Of Light Olefins Research Articles

Production of Light Olefins from Polyethylene in a Two-Step Process: Pyrolysis in a Conical Spouted Bed and Downstream High-Temperature Thermal Cracking

A two-step process has been used for the selective production of light olefins by the thermal cracking of high-density polyethylene. The plastic has been continuously fed into a conical spouted-bed reactor (CSBR) operating at 500 °C, which yields 93 wt % of waxes (C21+) and C12–C21 hydrocarbons. The volatile product stream has been cracked downstream in a multitubular (quartz tubes) reactor in the 800–950 °C range, with short residence times (0.016–0.032 s). A yield of 77 wt % of light olefins (C2–C4) has been obtained by operating at 900 °C in the second step. The maximum yields of ethylene, propylene, and butenes are 40.4, 19.5, and 17.5 wt %, respectively. Given the short residence time of the products in the reactor, the yield of aromatics is only 6.2 wt %. The high light olefin yield is due to the excellent performance of both steps. The CSBR allows maximizing the yield of waxes and avoiding defluidization problems. The operating conditions in the multitubular reactor (low concentration of the compou...

Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM-5, MCM-41, SAPO-34 and Y-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order: HZSM-5>SAPO-34>MCM-41> Y-zeolite. The highest olefins yield from bio-oil using HZSM-5 catalyst reached 0.22 kg/kgbio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.

Catalyst screening for conversion of glycerol to light olefins

Screening of modified ZSM-5 catalysts for conversion of glycerol to light olefins has been investigated. In this study HZSM-5, Al/ZSM-5, Ca/ZSM-5, Cr/ZSM-5, Cu/ZSM-5, Li/ZSM-5, Mg/ZSM-5 and Ni/ZSM-5 zeolite catalysts were prepared, tested and screened. The catalysts were characterized to relate their properties with catalyst activity. XRD and FTIR characterization results demonstrated that the structure of the catalysts remained intact while BET revealed the surface and micropore areas decreased after metal loading. TPR data exhibited the reduction phenomenon of the catalysts. NH3-TPD analysis indicated that Cu/ZSM-5 catalyst has relatively more moderate and strong active acid sites compared to others. GC TCD/FID analysis detected light olefins and paraffins; methane, CO and CO2 in the gaseous product stream. The acidity of the catalyst affected olefin production, but no direct correlation between surface area and olefin yield was observed. The turnover frequency (TOF) for Cu/ZSM-5 and Cr/ZSM-5 catalysts were significantly high comparatively. Cu/ZSM-5 produced the highest light olefins selectivity and yield due to the synergistic effect of the physico-chemical properties between the parent ZSM-5 and the metals.

Light olefins from HDPE cracking in a two-step thermal and catalytic process

The continuous catalytic pyrolysis of high density polyethylene (HDPE) has been carried out in a two-step reaction system involving a pyrolysis conical spouted bed reactor followed by a catalytic fixed bed reactor. The good performance of the conical spouted bed reactor has allowed using a low temperature in thermal cracking (500°C) without defluidization problems, obtaining a volatile stream with a 90wt.% overall yield of C12–C20 and waxes in the first step. The effect of the second-step operating conditions on product yields and composition has been studied using a catalyst based on a HZSM-5 (SiO2/Al2O3=30) zeolite. The influence of temperature in the 350–550°C range and space–time in the 0–8gcat min gHDPE−1 range has been studied. An increase in temperature or space–time gives way to an increase in the yield of light olefins, reaching a value of 62.9wt.% at 550°C and 8 gcat min gHDPE−1, with the individual yields of ethylene, propylene and butenes being 10.6, 35.6 and 16.7wt.%, respectively. Although the yield of single-ring aromatics increases when both variables studied are increased, the maximum yield obtained was lower than 13wt.%. The yield of waxes (the main product in the first step) is negligible even at low temperatures or spaces-times, which evidences the efficiency of the catalytic step.

MTO reaction over SAPO-34 catalysts synthesized by combination of TEAOH and morpholine templates and different silica sources

The SAPO-34 catalyst was synthesized by the combination of TEAOH and morpholine templates, and colloidal silica and silicic acid, as the silica source under hydrothermal conditions. The effect of the template molar ratio and silica source on the physicochemical properties of each catalyst was studied by XRD, SEM, BET and TPD techniques. XRD patterns revealed the significant effect of gel composition on the crystallinity and particle size of the samples. SEM photos showed that all the catalysts have cubic morphology, but their particle size was different. According to the XRD and SEM of the catalyst prepared by silicic acid, this catalyst showed low crystallinity and large crystal size. TPD analysis indicated that the acidity reduced by increasing the morpholine content in the reaction mixture. The catalytic performance of the synthesized catalysts was tested in MTO reaction. The catalyst produced by the TEAOH/morpholine ratio of 0.5:1.5 exhibited the highest light olefins yield, as well as the longest catalyst lifetime. The maximum yield of ethylene and propylene was determined to be 94 wt%, with 100% methanol conversion.

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

For the application of zeolites as heterogeneous catalysts, low diffusion resistance for hydrocarbons within the micropore is essential for improving product selectivity and catalyst lifetime. This problem has been overcome by reducing the crystal size. This review introduces size-controlled preparation of nano-sized zeolites via hydrothermal synthesis in water/surfactant/organic solvent (emulsion method) and their application to heterogeneous catalysts. The ionicity of the hydrophilic group in surfactant molecules and the concentration of the Si source affected the crystallinity and morphology of zeolites prepared using the emulsion method. When using a non-ionic surfactant, mono-dispersed silicalite-1 nanocrystals ~60 nm in diameter were successfully prepared. Nano- and macro-ZSM-5 zeolites with crystal sizes of ~150–200 nm and 1.5 μm, respectively, were prepared and applied to n-hexane cracking and acetone-to-olefin reactions to investigate the effect of zeolite crystal size on catalytic stability and light olefin yield. Application of nano-zeolite to light olefin production was effective in achieving faster mass transfer of hydrocarbon molecules within the micropore, which led to improvements in olefin yields and catalyst lifetime.

Selective production of green light olefins by catalytic conversion of bio‐oil with Mg/HZSM‐5 catalyst

AbstractBACKGROUND: Light olefins are the basic feedstocks for the petrochemical industry. So far, the olefins yield from bio‐oil is noticeably lower than that from methanol, ethanol and naphtha, and thereby needs to be improved by optimizing catalysts and cracking conditions. The main purpose of this work is to selectively produce light olefins through the catalytic cracking of bio‐oil using the magnesium modified HZSM‐5 catalyst.RESULTSCatalytic conversion of bio‐oil and its model compounds into light olefins was performed using the Mg/HZSM‐5 catalyst. The highest olefins yield from bio‐oil was 0.25 kg olefins (kg−1 bio‐oil) with a carbon yield of 59.3 C‐mol% and nearly complete bio‐oil conversion. The reaction conditions and addition of magnesium into the HZSM‐5 zeolite can be used to control both olefins yield and selectivity. In addition, the yield of light olefins from the pyrolysis of bio‐oil is much lower than the level from bio‐oil catalytic cracking.CONCLUSIONModerately increasing the medium acid sites through addition of Mg into the zeolite effectively enhanced olefins selectivity and improved catalyst stability. The production of light olefins from bio‐oil is closely associated with the chemical composition and hydrogen to carbon effective ratios of feedstock. Copyright © 2012 Society of Chemical Industry

Study on Olefin Decrement Reformulation and Increasing Light Olefins of FCC Gasoline by Catalytic Cracking

Catalytic upgrading of fluid catalytic cracked (FCC) gasoline obtained from Huabei Petrochemical Company, PetroChina (Renqiu, Hebei, China), was investigated using a microreactor and gas chromatograph integrated unit in order to decrease the content of olefins in gasoline and increase the light olefins (ethylene, propylene, and butylene) content. The experimental results showed that the olefin content in upgraded gasoline can be decreased from 42.6% in raw material to nearly 10%, meeting the requirements of the new gasoline standard, whereas iso-alkane and aromatics contents were markedly increased, from 28.4 and 18.2% to 47 and 36.1%, respectively, so the octane number of gasoline should not be reduced. In addition, higher yields of light olefins were obtained after FCC gasoline was reformulated under laboratory conditions. Higher reaction temperature, longer reaction time, higher weight ratio of catalyst to oil, and higher catalyst activity were beneficial to decrease the olefin content of FCC gasoline and increase the yields of light olefins.

Effect of process conditions on the composition of products in the conventional and deep catalytic cracking of oil fractions

With the purpose of increasing the yield of light C2-C4 olefins in comparison with that in conventional catalytic cracking, we experimentally study the effect of temperature and catalyst-to-oil ratio on the distribution of the basic products of oil catalytic cracking on the bizeolite and industrial LUX catalysts. The bizeolite catalyst contains ZSM-5 and ultrastable Y zeolites in equivalent amounts, while the LUX catalyst contains 18 wt % of Y zeolite in the HRE form. As shown by the results of our tests, the yield of C2-C4 olefins and gasoline in the deep catalytic cracking of hydrotreated vacuum gasoil on the bizeolite catalyst within a range of catalyst-to-oil ratios of 5–7 and temperatures of 540–560°C reaches 32–36 and nearly 30 wt %, respectively. In cracking on the LUX catalyst under similar conditions, the yield of light olefins and gasoline is 12–16 and 37–45 wt %, respectively. The distribution of target products in the deep catalytic cracking of different hydrocarbon fractions (vacuum gasoil, gas condensate, its fraction distilled from the cut boiling below 216°C, and the hydrocracking heavy residue) on the bizeolite catalyst is studied. It is shown that the fractions of gas condensate and hydroc-racking residue can serve as an additional source of hydrocarbon raw materials in the production of olefins.

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Alkali-treatment and Fe–Ti-loading were used to modify ZSM-5 zeolite. It was found that alkali-treatment created mesopore and Fe–Ti-loading improved the redox property of ZSM-5 catalyst, although both modifications led to a reduction of the total acid sites amount. The catalytic performance test indicated that the coexistence of meso–microporosity and Fe–Ti-loading on ZSM-5 catalyst is benefit to improve the yield of light olefins in catalytic cracking. The catalyst containing the combined modified ZSM-5 increased the propylene yield by 0.55wt% and total light olefins yield by 0.69wt% in catalytic cracking of Canadian LGO (light gas oil), compared with the reference HZSM-5.

Kinetics of Catalytic Pyrolysis of Heavy Gas Oil Derived from Canadian Synthetic Crude Oil

The catalytic pyrolysis of heavy gas oil derived from Canadian synthetic crude oil on zeolite catalyst was conducted in a confined fluidized bed reactor. The optimal reaction temperature, weight hourly space velocity, steam-to-oil weight ratio, and catalyst-to-oil weight ratio were 660 °C, 9.5 h–1, 0.6, and 20, respectively. The yield of total light olefins was 36.4 wt % under these optimal conditions. The overall reactants and products were classified into seven species, and a seven-lump kinetic model with 15 rate constants and a catalyst deactivation constant was proposed. Kinetic constants at 620, 640, 660, and 680 °C were estimated by a nonlinear least-squares regression method. Preexponential factors and apparent activation energies were then calculated according to the Arrhenius equation. The feed lump had larger rate constants and smaller apparent activation energies than did the intermediate product lumps. The seven-lump kinetic model showed high calculation precision and the predicted yields agre...

Cracking Performance of Gasoline and Diesel Fractions from Catalytic Pyrolysis of Heavy Gas Oil Derived from Canadian Synthetic Crude Oil

The secondary cracking performance of gasoline and diesel fractions from the catalytic pyrolysis of heavy gas oil derived from Canadian synthetic crude oil was investigated. Both diesel and gasoline fractions showed poor cracking performance. The feed conversion of the diesel fraction was below 51 wt %, and the yield of total light olefins was below 11 wt %. Meanwhile, the feed conversion of the gasoline fraction was below 30 wt % and the yield of total light olefins was below 7 wt %. The selectivity of total light olefins at 660 °C was only 22% for both fractions, and the selectivity of dry gas at 660 °C reached 25% for the diesel fraction and 34% for the gasoline fraction. The selectivity of coke at 660 °C reached 26% for the diesel fraction and 16% for the gasoline fraction. The diesel and gasoline fractions could partly crack to lighter components and could partly condense to heavier components. The condensation reaction played an important role in catalytic pyrolysis, and the selectivity of condensation products at 660 °C reached 42% for the cracking of the diesel fraction and 55% for the cracking of the gasoline fraction. The monomolecular cracking is the predominant cracking type, and both the free radical and the carbonium ion mechanisms play an important role under the experimental conditions.

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%.

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...

Catalytic performance on iron-based Fischer–Tropsch catalyst in fixed-bed and bubbling fluidized-bed reactor

Fischer–Tropsch synthesis (FTS) for the co-production of C2–C4 olefins and clean fuels such as gasoline and middle distillate from syngas was investigated on four different iron-based catalysts in a fixed-bed and a bubbling fluidized-bed reactor. The catalysts were prepared by wet-impregnation using the Al2O3, SiO2 and iron ore (FeOx) supports with the active components of Fe, K and (or) Cu, and each K/FeCuAlOx catalyst was prepared by a co-precipitation method. Except for the catalyst impregnated on SiO2, CO conversion of the other catalysts is similar regardless of the type of reactor. However, the yield of light olefins in the range of C2–C4 hydrocarbons and clean fuels is closely related to the formation of active iron carbide species and to surface acidity. The impregnated K/FeOx catalyst is found to be one of the promising catalysts to be applied in a bubbling fluidized-bed reactor for middle temperature FTS reaction due to its high resistance to catalyst attrition with a high catalytic performance.

Oxidative Conversion of Hexane to Olefins-Influence of Plasma and Catalyst on Reaction Pathways

An integrated plasma-Li/MgO system is efficient for the oxidative conversion of hexane. In comparison to the Li/MgO catalytic system, it brings considerable improvements in the yields of light olefins (C 2 = –C 5 = ) at relatively low temperatures indicating synergy from combination of plasma and catalyst. The study on the influence of temperature on the performance of the integrated plasma-Li/MgO system shows dominancy of plasma chemistry at the lower temperature (500°C), while contribution from the catalyst both in hexane activation and in enhancing olefin formation becomes significant at the higher temperature (600°C). At 500°C significant amount of acetylene formation is observed. This is minimized at 600°C at oxygen depleting conditions

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.

Development of a catalytic cracking process with a high yield of light olefins: technology and implementation

A new domestic catalytic cracking process with a high yield of light olefins which corresponds to the best foreign analogs with respect to the technical and economic indexes is described. This process differs from the traditional process by more severe conditions of cracking the feedstock, an increased content of ZSM-5 additive in the equilibrium catalyst, and conducting repeated cracking of light naphtha in an additional continuous reactor.

Development of a catalytic cracking process with a high yield of light olefins: study of the structure of the yield of products

The structure of the yield of products of catalytic cracking of vacuum gasoil and repeated cracking of light naphtha in the high-temperature region was investigated. The results of the studies served as the basis for developing catalytic cracking technology with a high yield of light olefins.