Chain Paraffins Research Articles

Reference-Quality Free Energy Barriers in Catalysis from Machine Learning Thermodynamic Perturbation Theory.

For the first time, we report calculations of the free energies of activation of cracking and isomerization reactions of alkenes that combine several different electronic structure methods with molecular dynamics simulations. We demonstrate that the use of a high level of theory (here Random Phase Approximation-RPA) is necessary to bridge the gap between experimental and computed values. These transformations, catalyzed by zeolites and proceeding via cationic intermediates and transition states, are building blocks of many chemical transformations for valorization of long chain paraffins originating, e.g., from plastic waste, vegetable oils, Fischer-Tropsch waxes or crude oils. Compared with the free energy barriers computed at the PBE+D2 production level of theory via constrained ab initio molecular dynamics, the barriers computed at the RPA level by the application of Machine Learning thermodynamic Perturbation Theory (MLPT) show a significant decrease for isomerization reaction and an increase of a similar magnitude for cracking, yielding an unprecedented agreement with the results obtained by experiments and kinetic modeling.

Reference‐Quality Free Energy Barriers in Catalysis from Machine Learning Thermodynamic Perturbation Theory

AbstractFor the first time, we report calculations of the free energies of activation of cracking and isomerization reactions of alkenes that combine several different electronic structure methods with molecular dynamics simulations. We demonstrate that the use of a high level of theory (here Random Phase Approximation—RPA) is necessary to bridge the gap between experimental and computed values. These transformations, catalyzed by zeolites and proceeding via cationic intermediates and transition states, are building blocks of many chemical transformations for valorization of long chain paraffins originating, e.g., from plastic waste, vegetable oils, Fischer–Tropsch waxes or crude oils. Compared with the free energy barriers computed at the PBE+D2 production level of theory via constrained ab initio molecular dynamics, the barriers computed at the RPA level by the application of Machine Learning thermodynamic Perturbation Theory (MLPT) show a significant decrease for isomerization reaction and an increase of a similar magnitude for cracking, yielding an unprecedented agreement with the results obtained by experiments and kinetic modeling.

Thermochemical processes for CO[formula omitted] hydrogenation to fuels and chemicals: Challenges and opportunities

This manuscript discusses the potential use of CO2 as a carbon and oxygen carrier to return it to the carbon life cycle in the form of fuels or chemicals via thermochemical catalytic pathways. Theoretically, CO2 hydrogenation can form a variety of fuels and chemicals. Practically, however, the selectivity, conversion, operating range, and kinetic limitations and operational cost determine the end product. Because of their high value and versatility as a chemical or fuel, small olefins (i.e., C2H4) and methanol are often considered as target species. Whether alcohol or olefin formation, CH4 and CO are the nature’s primary choices of CO2 conversion. They can be formed over a wide operating temperature, pressure, and CO2:H2 ratios. They are often competitive carbon species in olefin or methanol formation steps. Although they are less valuable as end products, they can be used as intermediate species. Secondary processes of CO and CH4 to form chemicals and fuels can increase the overall CO2 hydrogenation yield. Independent of the choice of end product, CO2 hydrogenation requires hydrogen. Pure hydrogen derived mostly from fossil fuels adds to the overall process cost and also increases the CO2 emissions. Hydrogen produced from water electrolysis is a renewable green pathway but is limited by the process efficiency and cost. As an alternative to pure hydrogen, low-value, small chain paraffins are suggested as the hydrogen carriers. Carbon dioxide–assisted oxidative dehydrogenation of paraffins to olefins process is a direct pathway to olefin formation. The paper discusses these potential pathways for CO2 utilization based on theoretical analysis and recent advances in academia and industry.

Copper catalyzed co‐pyrolysis of polyethylene terephthalate with low and high density polyethylene for liquid fuel production

AbstractBACKGROUNDMunicipal waste contains low density polyethylene (LDPE), high density polyethylene (HDPE), and polyethylene terephthalate (PET) in enormous amount. As these plastics are non‐biodegradable and pose serious threats to the environment, efforts have been made towards their safe disposal with energy recovery and value added chemicals by subjecting them to heat under oxygen deficient conditions. This study deals with the co‐pyrolysis of the three types of waste polymers, with special focus on the conversion of PET into liquid fuel by its interaction with the other two polymers.ResultsThe individual pyrolysis of LDPE and HDPE produced pyrolysis oil, whereas PET produced only wax. The co‐pyrolysis of the three polymers with different mixing ratios showed that PET hindered oil formation and increasing its amount more than 20 wt% in the polymer mixture resulted in wax formation. The thermal process produced 8 wt% pyrolysis oil, 32.3 wt% wax, 39.7 wt% pyro‐gases and 20 wt% coke while the catalytic process with copper catalyst produced 32.5 wt% pyrolysis oil, 3 wt% wax, 46.5 wt% pyro‐gases, and 18 wt% coke under optimum conditions.ConclusionThe thermal pyrolysis oil contained long chain paraffins as major components, while short chain isoparaffin and naphthenes were predominant in the catalytic pyrolysis oil owing to which marked differences were observed in the physicochemical properties of both oils. The fractionally distilled fractions of catalytic pyrolysis oil in gasoline, kerosene, and diesel range showed profound similarities with standard fuels in terms of fuel properties particularly the gasoline range fraction. © 2022 Society of Chemical Industry (SCI).

Role of zeolite properties in bio-oil deoxygenation and hydrocarbons production by catalytic cracking

A comparison between the behavior of Y and ZSM-5 zeolites having the same Si/Al ratio was established in the catalytic cracking of bio-oil for producing fuels and platform chemicals. The catalysts were prepared by agglomerating each zeolite with a mesoporous γ-Al2O3 matrix. Properties of the zeolites and the catalysts were characterized by N2 ads/desorption, SEM-EDX, pyridine-FTIR, tBA-TPD, and NH3-TPD techniques. The experiments were conducted in a continuous two-step catalytic cracking system (TS-CC) at 450 °C. Both catalysts are highly selective to C5-C12 hydrocarbons, with a composition strongly affected by the porous structure and acidity of the zeolite. The HZSM-5 catalyst (high acid strength and Brønsted/Lewis ratio) promotes cracking and deoxygenation reactions that lead to C2−C4 olefins which condensate into aromatics, yielding 9% of 1-ring aromatics (3% BTX) and 4% of naphthalenes for a feed conversion of 85%. These reactions are less favored over the HY catalyst, which promotes olefins oligomerization and hydrogen-transfer reactions, yielding 14% of highly aliphatic gasoline (> 30% linear paraffins) and 5% of C13−C20 diesel fraction (> 90% long chain paraffins). The remaining upgraded bio-oil obtained with both catalysts is composed of light oxygenates, with ketones, acids and esters as main components and low concentration of phenolic compounds.

The production of renewable aviation fuel from waste cooking oil. Part II: Catalytic hydro-cracking/isomerization of hydro-processed alkanes into jet fuel range products

In this study, the surrogates of long chain paraffins produced from waste cooking oil through hydro-processing was hydro-cracked and hydro-isomerized for studying the process for producing renewable aviation fuel, through carrying out the experiments with varying reaction temperature, pressure, H2-to-alkane ratio and weight hourly space velocity (WHSV) over the home-made NiAg/SAPO(silicoaluminophosphate)-11catalyst. The data of conversion, selectivity, isomer yield and isomer-to-normal (I-to-N) alkane ratio were determined for evaluating the performance of the catalyst. The catalyst characterizations of the fresh and spent catalysts were examined through the technologies of Scanning Electron Microscopy (SEM), powder X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and fourier-transform infrared (FTIR) spectroscopy. It was found that the rearrangement of vapor-liquid equilibrium and increase in residence time by adjusting the operating conditions improved the performance of hydro-cracking/isomerization. In addition, based on the results of catalyst characterizations, the unreacted feed was dispersed onto the surface of the catalyst, expected to deactivate the catalyst.

Study on the effect of Kankara zeolite-Y-based catalyst on the chemical properties of liquid fuel from mixed waste plastics (MWPs) pyrolysis

We report in this study the effect of Kankara zeolite-Y-based catalyst on the chemical properties of liquid fuel from mixed waste plastics pyrolysis using a batch reactor. Fourteen set of 200 g of waste plastics comprising 27 wt%HDPE, 33 wt%LDPE, 13 wt%PP, 18 wt%PS, 9 wt%PET were de-polymerized with catalyst and a set without catalyst. The catalyst used comprises of a mixture of zeolite-Y, metakaolin, aluminum hydroxide and sodium silicate all synthesized from Kankara kaolin from Kankara in Katsina state, Nigeria. Fourteen different catalyst combinations derived from design of experiment using Design expert 11.0 were used to produce fourteen different liquid fuel samples, and the liquid sample with the highest yield was determined. Fourier transform infrared spectroscopy was used to detect various characteristic functional groups present in the samples. Furthermore, the various compounds in the uncatalyzed (thermal pyrolysis) and catalyzed samples with highest yield were determined using GC/MS. The results show that the highest yield of liquid fuel from the fourteen catalyst combination was 46.7 wt% while the thermal pyrolysis gave a yield of 66.9 wt%. The GC/MS result shows carbon in the range of C6–C13 and absence of long straight chain paraffins in the catalyzed fuel samples while the uncatalyzed sample has carbon in the range of C7–C20. Consequently, the thermal pyrolysis sample consists of 59%, 36% and 5% of gasoline, diesel and fuel oil, respectively, while the catalyzed sample consists of 93% gasoline and 7% diesel fraction.

Mild hydroisomerization of heavy naphtha on mono- and bi-metallic Pt and Ni catalysts supported on Beta zeolite

Abstract Hydroisomerization of long chain paraffins has emerged as a promising process for the valorization of low value fuel cuts, such as heavy naphtha, from crude oil-, coal- and bio-based feedstocks. In this study, the hydroisomerization reaction is investigated on a series of mono- and bi-metallic Pt (0.2 wt%) and/or Ni (10 wt%) catalysts supported on Beta zeolite with SiO2/Al2O3 ratio 75. Catalysts exhibit similar reactivity in the hydroisomerization of n-octane model compound, despite the very different loading and the 40% lower Bronsted acidity of the Ni-containing materials. This suggests that hydrogenation/dehydrogenation is the rate limiting step of the reaction due to very low loading of Pt and the weak dehydrogenating capacity of Ni. The latter also leads to up to 34% lower selectivity to i-C8 for the monometallic Ni catalyst. The addition of Pt in the bimetallic Ni-Pt catalyst, not only restores, but enhances the isomerization selectivity, favoring the production of di-branched to mono-branched isomers. The characterization results show that Pt enhances the reducibility and improves the dispersion of Ni, leading to increased metallic/acid sites ratio. Hydroisomerization tests with refinery naphtha as feed highlight the promising performance of this catalyst, as Ni-Pt/H-Beta increases the octane number of naphtha by 13% at mild temperature and pressure (260 °C, 10 bar), improving significantly the quality of naphtha for gasoline applications.

Catalytic Hydroisomerization of Long-Chain Hydrocarbons for the Production of Fuels

Hydroisomerization of long chain paraffins for the production of branched alkanes has recently been intensively studied due to a large availability of these compounds. The most interesting research topics have been the development of novel bifunctional catalysts to maximize the yield of isomers and to suppress the cracking reactions. Since both of these reactions are catalyzed by Brønsted acid sites, the optimum catalyst exhibits equal amounts of metal and acid sites, and it facilitates rapid mass transfer. Thus, several hierarchical and nano-shaped zeolites have been developed, in addition to composite catalysts containing both micro- and mesoporous phases. In addition to catalyst development, the effect of the reactant structure, optimal reaction conditions, catalyst stability and comparison of batch vs continuous operations have been made.

Production of Light Hydrocarbons from Syngas Using a Hybrid Catalyst

A hybrid catalyst consisting of a Cu-ZnO/Al2O3 methanol synthesis catalyst and a SAPO-34 molecular sieve was shown to convert syngas into a narrow mixture of short chain paraffins centered at C2–C3 with little methane and C5+ made. This product mix is expected to be an excellent cracker feedstock for the production of olefins. The hybrid catalyst system closely couples sequential reactions on each of the two independent catalysts. The function of each of the components was unraveled by performing experiments in which the reactor was loaded with discrete layers of the individual catalysts. Methanol (MeOH) synthesis over Cu-ZnO/Al2O3 is followed by methanol conversion to dimethyl ether (DME) + steam over the acidic SAPO-34 or Cu-ZnO/Al2O3 component. Simultaneously, the so generated water feeds into the water gas shift (WGS) reaction over Cu-ZnO/Al2O3, producing H2 + CO2, and the DME/MeOH undergoes methanol to olefins (MTO) conversion over SAPO-34. The olefins are subsequently hydrogenated to paraffins over ...

Enhanced microbial degradation of waxy crude oil: a review on current status and future perspective

Most of the crude oil reservoirs in the world are getting matured leading to the increased production and deposition of long chain paraffins (wax) at subsurface and surface facilities creating a challenge for flow assurance and safer operation. Deposition of wax on the inner walls of the pipelines tends to decrease the flow of crude oil thereby causing billions of dollars of loss. This article reviews in detail about the various aspects of the microbial degradation of waxy crude oil, along with different mechanisms involved in the hydrocarbon degradation. In addition, the article acts as a guide to screen the microorganism suitable for different environmental conditions for their applications in pipelines, oil spill remediation and microbial-based enhanced oil recovery technique to waxy and heavy oil reservoirs for environmentally safe operation. [Received: February 20, 2016; Accepted: March 20, 2016]

New trend for the pour point depression of a waxy petroleum fraction with in-situ desulphurization using (O2H & OH) radicals coupled with nanoparticles of titanium compounds

The depression of pour point of a petroleum fraction with high wax content is commonly based on either the dispersion of the long chain paraffins using some dispersive materials or via the cracking of these paraffins into short chains. In line with this, the development of an energy-efficient desulphurization process requires radical approach, not limited to the conventional technologies. Several processes have been employed lately, including selective adsorption on suitable materials and catalytic oxidation. Herein, the current research study introduces new techniques for the cracking of the n-paraffin of a petroleum fraction with execution of an in-situ desulphurization. In particular, two different techniques were utilized during this work. The first is based on coupling nanoparticles with an oxidizing agent while the other provides a combination of the photo-catalysis route with oxidative radicals. In both techniques, the same nanoparticles of titanium compounds were used; however, different mechanisms had undertaken through the designed application, based on the dissimilar chemistries that were provided by the nanoparticles. Both techniques also provide new advances in the oxidation process via utilizing oxygen radicals, generated from hydrogen peroxide, instead of using air or oxygen gas. At the end of these techniques, promising results were obtained through the reduction of pour point, by minimizing the percentages of the long chain n-paraffin, as well as the removal of 80% of the sulphur compound content of the feedstock. The ultimate sulphur removal at the final product was attained via a subsequent solvent extraction process. The total removal of the sulphur content had reached 95.5% by using N-Methyl Pyrrolidone (NMP) at the room temperature, and was approximately 30°C.

Rapid investigation of paraffin dehydrogenation catalyst by TPRn/SPI-TOF-MS technique for industrial application

Dehydrogenation of long chain paraffins over commercial Pt-Sn-K-Mg/Al2O3 and Pt-Sn-Na-Co/Al2O3 catalysts were investigated using a temperature programmed reaction/single-photon ionization time-of-flight mass spectrometry (TPRn/SPI-TOF-MS) system under realistic reaction conditions using model compound C120 and in the industrial PACOL dehydrogenation plant using n-C100-C130 mixture. The catalysts were characterized by BET, mercury intrusion porosimetry, CO-chemisorption and NH3-TPD. Catalytic activity, selectivity to various components and stability were compared between TPRn/SPI-TOF-MS measurement and industrial plant run data to explore the reliability, predictability and application of TPRn/SPI-TOF-MS for rapid catalyst testing and screening. Characteristics of the catalysts, such as Pt dispersion and acidity, affected paraffin dehydrogenation conversion and mono-olefin selectivity. This was reflected in the catalyst performance data obtained on TPRn/SPI-TOF-MS system, which was in good agreement with the data from industrial runs. It is shown that use of TPRn/SPI-TOF-MS measurements allows to identify the reaction temperature range for maximum mono-olefin yield. Further it is possible to judge onset temperature for all the products and help identify operation temperature for industrial plant operation. Investigation of aromatics formation over the catalysts establishes the consecutive reaction pathways of long chain paraffin dehydrogenation over modified Pt-Sn/Al2O3 catalyst.

Systematic investigations on the biodegradation and viscosity reduction of long chain hydrocarbons using Pseudomonas aeruginosa and Pseudomonas fluorescens.

The use of microorganisms has been researched extensively for possible applications related to hydrocarbon degradation in the petroleum industry. However, attempts to improve the effect of microorganisms on the viscosity of hydrocarbons, which find potential use in the development of robust models for biodegradation, have been rarely documented. This study investigates the degradation of long chain hydrocarbons, such as hexadecane and eicosane using Pseudomonas fluorescens PMMD3 (P. fluorescens) and Pseudomonas aeruginosa CPCL (P. aeruginosa). P. aeruginosa used here is isolated from petroleum contaminated sediments and the P. fluorescens is from the coastal area, and both have hydrocarbon degrading genes. The degradation of hydrocarbons is studied using carbon profiling and reduction in viscosity pre- and post-degradation of hydrocarbons. The carbon profiling has been obtained using gas chromatography-mass spectroscopy (GC-MS), and Fourier transform infrared spectrometer (FTIR) results. GC-MS results have indicated an improved biodegradation of hydrocarbons by 77-93% in one day. The yield coefficients of biomass (YX/S) for P. aeruginosa and P. fluorescens using hexadecane as a carbon source are 1.35 and 0.81 g g(-1), and the corresponding values with eicosane are 0.84 and 0.88 g g(-1). The viscosity of hexadecane is reduced by the order of 53 and 47%, while that of eicosane was reduced by 53 and 65%, using P. aeruginosa and P. fluorescens, respectively. This study also presents information on the activity of enzymes responsible for the hydrocarbon degradation. Pseudomonas species have shown their use in potential applications for bioremediation, oil-spill treatment, and flow assurance. We believe that this study will also provide stringent tests for possible model development for the bioremediation of long chain paraffins suitable for oilfield applications.

Metals modification of the paraffin dehydrogenation catalyst regenerated by coke combustion

The industrially deactivated Pt0.5-Sn1.5-K0.5-Mg1/γ-Al2O3 catalyst for dehydrogenation of long chain paraffins (n-C10°–C13°) was regenerated by coke burn off and metals (Pt, Sn and K) modification. The catalysts were characterized by TG, BET, CO-chemisorption, H2-TPR, XRD and mechanical crushing strength test. Paraffin dehydrogenation was performed on a bench reactor at the industrial site. Results showed that temperature increase during coke combustion can be effectively controlled with O2 content lower than 1%. The combustion temperature should be higher than 500°C to burn all the coke and lower than 550°C to avoid Pt sintering. Under optimal conditions, coke combustion results only in 92% recovery of catalyst activity. Subsequent metals modification with additional 0.01wt.% Pt addition can recover catalytic performance completely, paraffin conversion and olefin selectivity to the levels of fresh catalyst. The modified catalyst has longer life-time of 77 days compared to fresh catalyst of 69 days. Results are explained in terms of the characteristics of the catalysts.

Action of biosurfactant producing thermophilic Bacillus subtilis on waxy crude oil and long chain paraffins

The study has been carried out to investigate the production of biosurfactant by a thermophilic strain of Bacillus subtilis on various hydrocarbon substrates, such as waxy crude oil, model crude oil and six long chain paraffins (C16H34 to C36H74) at 35, 50 and 75 °C. Model crude oil represents the mixture of the six long chain paraffins. The maximum biosurfactant production has been found to occur at 50 °C with n-hexadecane (C16H34) as a substrate. It has also been inferred that the physico-chemical properties of the biosurfactant is reduced with an increase in carbon number in the hydrocarbon substrate. Biosurfactant production is observed to be higher in the presence of waxy crude oil than the model crude oil, which is due to the presence of short chain paraffins with fewer carbon numbers in the former. B. subtilis in the presence of waxy crude oil has been observed to show high microbial adherence, improved surface tension reduction and emulsification activity, production of higher amount of biosurfactant ‘surfactin’, and improved biosurfactant stability upto 120 °C at 10 MPa, 10% (w/v) salinity and pH 8–14. This indicates the potential of microorganism in tackling oil-spill, wax degradation, flow assurance and enhanced oil recovery.

Ideal Hydrocracking Catalysts Based on Microporous Molecular Sieves

Hydrocracking catalysts consisting of metal and microporous molecular sieves play an essential role in petroleum industry. This review summarizes the compositions, preparation approaches and applications of hydrocracking catalysts based on molecular sieves. Specifically, this review includes: (i) a brief overview of selected methods of direct synthesis and the post-synthetic modification of molecular sieves; (ii) an introduction of the existing strategies to incorporate metals with microporous molecular sieves to prepare bifunctional catalysts, e.g., impregnation and ion exchange; and (iii) a summary of various hydrocracking catalysts for long chain paraffins and aromatics. Keywords: Bifunctional catalysts, hydrocracking, molecular sieves, post-synthesis modification.

Industrial development of long chain paraffin (n-C100–C130) dehydrogenation catalysts and the deactivation characterization

Pt–Sn–K–Mg/Al2O3 catalysts for the dehydrogenation of long chain paraffins (n-C100–C130) were successfully developed and applied in the industry. The catalysts were tested on both the industrial side fixed bed reactor and the industrial PACOL dehydrogenation plant. The industrially deactivated Pt–Sn–K–Mg/Al2O3 catalysts were characterized by TG–DTA, elemental analysis, UV Raman spectroscopy, TPO, SEM, XRD, BET, MIP and CO-chemisorption. The industrial 72-day-run dada indicated that Pt–Sn–K–Mg/Al2O3 catalysts performed excellent dehydrogenation conversion of 11.6% and high mono-olefin selectivity of 94.1%. The daily output of alkylbenzene over Pt–Sn–K–Mg/Al2O3 catalysts was as high as 333.6ton/day. The deactivated catalysts were deposited by the amorphous and graphitized coke, of which the weight percentage was 3.78% and the H/C mole ratio was 1.19. The coke covered parts of the Pt and support surface, while the pore and crystalline structure of the catalysts were not destroyed.

Preparation of hierarchical SAPO-11 molecular sieve and its application for n-dodecane isomerization

The isomerization conversion of long chain paraffins for high quality lube oil production plays an important role in the petrochemical industry. The conventional isomerization catalyst, SAPO-11 molecular sieve, exhibits disadvantages for large molecule transfer and multi-branched isomer conversion. To overcome the difficulty of long chain paraffin isomerization, SAPO-11 with hierarchical structure was synthesized by acid modification. With comparison of citric acid modification and hydrochloride acid modification, the hierarchical SAPO-11 was obtained and characterized by nitrogen sorption, XRD, SEM, TEM, and Py-FTIR. The catalytic isomerization activity of prepared hierarchical SAPO-11 was evaluated by n-dodecane isomerization reaction, and the results showed that it had high isomerization conversion and multi-branched isomer selectivity.

Temperature Dependent Behavior of Oil Dispersion System in Bulk and on the Metal Surface

This article focuses on the temperature dependent behavior of oil dispersion systems containing high amount of paraffins. In particular the properties of oils in bulk and during the contact with metal surface were evaluated by methods of rheoviscometry, thermal analysis, differential scanning calorimetry, gravimetry, polarization microscopy, gas chromatography and chemical analysis. Analysis of rheological parameters of oil, morphology of paraffin crystals, and thermal properties at temperature interval between 0÷90 0 С allowed to determine the transition temperature of oil dispersion system from the molecular to free-dispersal and bounded-dispersal states. It was established that the indicated parameters depend on oil composition, molecular-mass distribution of paraffins, curing temperature and cooling rate. Contacting of high paraffinic oils with steel surface leads to formation of asphaltene-resin-paraffin deposition (ARPD). The quantity, structure, composition and adhesiveness of ARPD depends on oil composition and gradient of temperature between heated oil and cooled metal surface. In case of temperature gradient is more than 30 0 С the solid and high adhesive depositions are formed. Their structure is enriched by long chain high-melting paraffins. In case of temperature gradient is less than 20 0 С, amorphous and easy removable depositions are formed. Their structures are enriched by mechanical admixtures, water, resin, asphaltene and low-melting short chain paraffins. Key words: High-paraffinic oil; Oil dispersion system; Asphaltene-resin-paraffin depositions; Wax appearance temperature; Heat treatment