Hydrocarbon Feedstock Research Articles

Reductive Amination of Carbonyl C-C Bonds Enables Formal Nitrogen Insertion.

Given its relevance across numerous fields, reductive amination is one of the oldest and most widely used methods for amine synthesis. As a cornerstone of synthetic chemistry, it has largely remained unchanged since its discovery over a century ago. Herein, we report the mechanistically driven development of a complementary reaction, which reductively aminates the C-C σ-bond of carbonyls, not the carbonyl C-O π-bond, generating value-added linear and cyclic 3° amines in a modular fashion. Critical to our success were mechanistic insights that enabled us to modulate the resting state of a borane catalyst, minimize deleterious disproportionation of a hydroxylamine nitrogen source, and control the migratory selectivity of a key nitrenoid reactive intermediate. Experiments support the reaction occurring through a reductive amination/reductive Stieglitz cascade, via a ketonitrone, which can be interrupted under catalyst control to generate valuable N,N-disubstituted hydroxylamines. The method reported herein enables net transformations that would otherwise require lengthy synthetic sequences using pre-existing technologies. This is highlighted by its application to a two-step protocol for the valorization of hydrocarbon feedstocks, the late-stage C-C amination of complex molecules, diversity-oriented synthesis of isomeric amines from a single precursor, and transposition of nitrogen to different positions within a heterocycle.

Membrane reformer technology for sustainable hydrogen production from hydrocarbon feedstocks

Hydrogen (H2) is receiving growing interest as a clean energy carrier as the world’s energy system transitions towards net zero. Today, H2 is primarily produced from hydrocarbons using the steam methane reforming (SMR) process. This well-established method converts methane-rich gas into syngas, which is further treated with steam to increase H2 yield via the water-gas-shift (WGS) process. However, this conventional route results in high carbon intensity of 10 tons CO2/ton of H2. Therefore, there is a growing need for sustainable H2 production technologies that utilize existing fossil energy sources and infrastructure while minimizing carbon emissions and costs.Membrane reactors (MR) are a promising technology for sustainable H2 production from hydrocarbons. A H2-selective palladium-alloy (Pd–Au) membrane is integrated within the catalyst bed, creating a system where H2 production and separation occur simultaneously in a single unit. This integration offers several advantages over the conventional system; process intensification allows thermodynamic equilibrium conversion limitations to be overcome while producing high purity (>99%) H2 at milder operating temperatures of ∼550 °C compared to 800–1000 °C in conventional packed bed reactors. Downstream processes such as WGS reactors and pressure swing adsorption are eliminated, resulting in reduced capital and operating costs. Moreover, the by-product stream remains pressurized at 25–40 bar and contains CO2 at concentrations above 60%, enabling CO2 capture at reduced cost.

Calculation of the Rate Constants of Vacuum Residue Hydrogenation Reactions in the Presence of a Chrysotile/NiTi Nanocatalyst

The paper presents the results of an investigation into the kinetics of catalytic hydrogenation of vacuum residue at temperatures of 380, 400 and 420 °C and different durations, ranging from 30 to 70 min, using a nanocatalyst containing the active metals nickel and titanium supported on chrysotile. It was found that the yield of oils from 30 to 50 wt.% and tars from 12 to 18 wt.% increased with increasing temperatures and reaction times. A slight increase in the proportion of solids in the range of 2.0 to 6.0 wt.% is explained by the activity of the nanocatalyst used. In the study of the kinetics of vacuum residue hydrogenation, using the nanocatalyst developed by the authors, we were able to achieve a low yield of solids with a short contact time as well as a high yield of low-molecular-weight compounds such as oils and tars. To determine the kinetic parameters (rate constants and activation energies), Simpson’s integral method and a random search engine optimization method were used. High values of rate constants are characteristic of reactions in the formation of oils k1, tars k2 and asphaltenes k3 in the temperature range of 380–420 °C. The high values of the rate constants k1, k2 and k3 in the catalytic hydrogenation of the vacuum residue indicate the high reaction rate and activity of the nanocatalyst used. With an increase in temperature from 380 to 420 °C, the rate constant of the formation of gas products from vacuum residue and the conversion of asphaltenes into oils significantly increase, which indicates the accumulation of low-molecular-weight compounds in oils. The activation energy for reactions leading to the formation of oils, tars, asphaltenes, gas and solid products was 75.7, 124.8, 40.7, 205.4 and 57.2 kJ/mol, respectively. These data indicate that the processes of vacuum residue hydrogenation with the formation of oils and asphaltenes require the lowest energy inputs. Reducing the process temperature to increase the selectivity of the vacuum residue hydrogenation process when using the prepared nanocatalyst is recommended. The formation of oils at the initial stage plays a key role in the technology of the heavy hydrocarbon feedstock (HHF) hydrogenation process. Perhaps the resulting oils can serve as an additional solvent for high-molecular-weight products such as asphaltenes, as evidenced by the low activation energy of the process.

Formal kinetics of catalytic oxidation of diesel paraffin-naphthenic fraction in the presence of carbon nanotubes containing Co, Mn and Fe

This study identified the formal kinetics of aerobic oxidation of the paraffin-naphthenic fraction of diesel fuel in the presence of multi-walled carbon nanotubes (MWCNTs) containing three transition metals—Fe, Co, and Mn. The synthesis of metal-containing multi-walled carbon nanotubes (M@MWCNTs) was carried out by pyrolysis of cyclohexane in the presence of ferrocene (CVD synthesis), followed by sequential doping of the resulting iron-containing carbon nanotubes Fe@MWCNTs with Co and Mn clusters. The resulting Fe–Co–Mn@MWCNT samples were identified using electron microscopy (SEM, TEM) and elemental analysis. The resulting carbon nanotubes were found to have a diameter of 30–60 nm and length of 500–800 μm. Iron clusters were observed to be present within the channels, while Co and Mn particles were observed to be present in the outer space of the nanotubes. The formal kinetic regularities of the dearomatized diesel fraction aerobic oxidation promoted by M@MWCNT additives were studied. It has been demonstrated that metal-nanocarbon additives effectively catalyze the oxidation process in the absence of hydroperoxides, resulting in thermal decomposition. The introduction of Co and Mn clusters into the nanotube structure has been observed to enhance catalytic activity. A catalytic oxidation scheme is currently under consideration, with corresponding effective oxidation rates being determined. It is postulated that these findings may prove useful in the estimation of effective nano-catalytic systems for the oxidative conversion of multicomponent hydrocarbon feedstocks.

Techno-Economic Analysis of Hydrogen Generation in Hydrocarbon Reservoirs

Summary To reduce carbon emissions and meet increasing energy demands, efforts are being made to seek clean energy such as hydrogen (or H2). Currently, the dominant method to generate hydrogen is steam methane reforming at a surface plant. It would be ideal to extend this method to subsurface hydrocarbon reservoirs; hydrogen is separated from the other generated gases via a downhole hydrogen-selective membrane separator. By doing so, hydrogen is extracted from the wellhead, and other gases are left in the reservoir. The purpose of this paper is to provide a techno-economic analysis of this idea. The energy of generated hydrogen is compared with the energy of the hydrocarbon feedstock. The hydrogen selectivity (concentration) in the generated synthesis gas (syngas) and the amount of hydrogen generated per unit mass of oil in the literature are reviewed and discussed. The constraints to the hydrogen generation conditions in subsurface reservoirs are discussed. The effectiveness of the downhole membrane is discussed. It is found that the energy from generated hydrogen is much less than the energy input even in a surface reactor where reactants are fully mixed for reactions. In a subsurface reservoir, injected reactants cannot fully mix with the in-situ oil and gas, and reactions may occur only near the flood-front zone of a high temperature. As injected gas (such as steam or oxygen) displaces the oil and gases ahead, the produced hydrocarbons are much higher than hydrogen. Separation of hydrogen from other gases downhole presents challenges in many aspects in reality, such as membrane permeability or separation rate, work life (mechanical and chemical stability), and so on. Therefore, unless a revolutionary technology breakthrough occurs, the generation and production of hydrogen in a subsurface hydrocarbon reservoir may not be feasible.

STUDY OF THE EFFECT OF SUPERCRITICAL WATER ON SOLID PRODUCTS OBTAINED AFTER CRACKING

One of the possible applications of supercritical water is the conversion of heavy hydrocarbon feedstocks with a high content of resins and asphaltenes. The use of supercritical water makes it possible to reduce the yield of solid products and increase the yield of light fractions. In this work, a comparative analysis of the cracking processes of petroleum residue, asphaltenes and resins isolated from it was carried out in an environment of supercritical water and without water. The experiments were carried out in an autoclave at a temperature of 450 °С and a pressure of up to 47 MPa. Cracking duration – 60 min. Cracking of petroleum residue, as well as its individual components - resins and asphaltenes, in a supercritical water environment - showed a positive effect on conversion; in all experiments, the yield of solid products decreased and the yield of maltenes increased. Solid products were studied using X-ray diffraction and thermogravimetric analysis and scanning electron microscopy. Using X-ray diffraction analysis, the influence of supercritical water on the parameters of the macrostructure was studied. It was determined that cracking with water affects the increase in the distance between saturated fragments of molecules (dr) in the structure of solid cracking products in comparison with products obtained without water. Using scanning electron microscopy, the surface of particles of insoluble cracking products was characterized. Solid products obtained in a supercritical water environment have a porous surface. According to thermal analysis data, it is shown that solid products obtained by cracking in water are characterized by more intense dynamics of sample weight loss and a smaller residue at the final temperature. For citation: Nalgieva Kh.V., Kopytov M.A. Study of the effect of supercritical water on solid products obtained after cracking. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 113-120. DOI: 10.6060/ivkkt.20246708.14t.

Artificial neural network for predicting the performance of waste polypropylene plastic-derived carbon nanotubes

AbstractIn this study, an artificial neural network model using function fitting neural networks was developed to describe the yield and quality of multi-walled carbon nanotubes deposited over NiMo/CaTiO3 catalyst using waste polypropylene plastics as cheap hydrocarbon feedstock using a single-stage chemical vapour deposition technique. The experimental dataset was developed using a user-specific design with four numeric factors (input variable): synthesis temperature, furnace heating rate, residence time, and carrier gas (nitrogen) flow rate to control the performance (yield and quality) of produced carbon nanotubes. Levenberg–Marquardt algorithm was utilized in training, validating, and testing the experimental dataset. The predicted model gave a considerable correlation coefficient (R) value close to 1. The presented model would be of remarkable benefit to successfully describe and predict the performance of polypropylene-derived carbon nanotubes and show how the predictive variables could affect the response variables (quality and yield) of carbon nanotubes.

Non-Oxidative Coupling of Methane Catalyzed by Heterogeneous Catalysts Containing Singly Dispersed Metal Sites

Direct upgrading of methane into value-added products is one of the most significant technologies for the effective transformation of hydrocarbon feedstocks in the chemical industry. Both oxidative and non-oxidative methane conversion are broadly useful approaches, though the two reaction pathways are quite distinguished. Oxidative coupling of methane (OCM) has been widely studied, but suffers from the low selectivity to C2 hydrocarbons because of the overoxidation leading to undesired byproducts. Therefore, non-oxidative coupling of methane is a worthy alternative approach to be developed for the efficient, direct utilization of methane. Recently, heterogeneous catalysts comprising singly dispersed metal sites, such as single-atom catalysts (SAC) and surface organometallic catalysts (SOMCat), have been proven to be effectively active for direct coupling of methane to product hydrogen and C2 products. In this context, this review summarizes recent discoveries of these novel catalysts and provides a perspective on promising catalytic processes for methane transformation via non-oxidative coupling.

Asymmetric Three-Component Radical Alkene Carboazidation by Direct Activation of Aliphatic C-H Bonds.

Azide compounds are widely present in natural products and drug molecules, and their easy-to-transform characteristics make them widely used in the field of organic synthesis. The merging of transition-metal catalysis with radical chemistry offers a versatile platform for radical carboazidation of alkenes, allowing the rapid assembly of highly functionalized organic azides. However, the direct use of readily available hydrocarbon feedstocks as sp3-hybridized carbon radical precursors to participate in catalytic enantioselective carboazidation of alkenes remains a significant challenge that has yet to be addressed. Herein, we describe an iron-catalyzed asymmetric three-component radical carboazidation of electron-deficient alkenes by direct activation of aliphatic C-H bonds. This approach involves intermolecular hydrogen atom transfer between a hydrocarbon and an alkoxy/aryl carboxyl radical, leading to the formation of a carbon-centered radical. The resulting radical then reacts with electron-deficient alkenes to generate a new radical species that undergoes chiral iron-complex-mediated C-N3 bond coupling. An array of valuable chiral azides bearing a quaternary stereocenter were directly accessed from widely available chemical feedstocks, and their synthetic potential is further demonstrated through more facile transformations to give other valuable enantioenriched building blocks.

Prediction of catalytic cracking performance during co-processing of vacuum gas oil and low-margin oil refining streams

Relevance. Expansion of catalytic cracking feedstock resources both due to the need to intensify the process to increase the yield of target products (high-octane gasoline, light olefins) and to deepen oil refining through the utilization of low-margin streams at refineries. Along with this, there is an urgent need to develop domestic mathematical tools for optimizing the catalytic cracking, predicting the process performance when the modes and feedstock qualities changes, as well as planning of production. This requires in-depth analysis and detailed study of the composition of oil fractions involved in processing and thermodynamics and kinetics of a heterogeneous process. The development and application of a mathematical model of the catalytic cracking, taking into account the composition and properties of the components involved in processing, makes it possible to quantitatively assess the yield and quality of target and by-products depending on the composition, physicochemical properties of the mixed feedstock, and the parameters of the technological regime, with an assessment of the possibility of their processing at an existing industrial facility. Aim. Experimental study of the composition and properties of mixed feedstock of catalytic cracking based on vacuum gas oil containing 5 to 20 wt % of extract of selective cleaning of oils, distillate, residual slack wax, and deasphalted oil, and prediction of the catalytic cracking indicators during their co-processing using a mathematical model. Methods. Liquid chromatography method to study the composition of feedstock materials of the catalytic cracking in combination with a number of standard methods for determining physico-chemical properties. Results. Using a set of experimental studies, the authors have established the patterns of changes in the composition and physico-chemical properties of the components and mixed feedstock of catalytic cracking containing 5–20 wt % of distillate and residual slack wax, deasphalted oil, and extract. The results obtained were used in development of a mathematical model of the heterogeneous catalytic cracking of feedstock, which takes into account the composition of oil fractions involved in processing and the patterns of catalyst deactivation by coke. Using a mathematical model, the authors established the patterns of changes in the composition and yield of process products when 5–20 wt % were involved in processing distillate slack wax and extracts of selective cleaning of oils mixed with vacuum distillate. Practical recommendations were developed on the possibility of expanding the hydrocarbon feedstock of the catalytic cracking, taking into account the fuel or petrochemical regime.

Tailoring the hydrophobicity of nickel hydroxide for selective electrooxidation of methane to methanol and ethanol

Electrocatalytic oxidation of methane (CH4) to value-added chemicals under mild conditions derived by renewable electricity is an attractive approach to directly use natural gas as a hydrocarbon feedstock. Herein, we report a novel composite electrode constructed by uniformly dispersing hydrophobic polytetrafluoroethylene (PTFE) polymer on the surface of Ni(OH)2 nanosheets catalyst for selective electrooxidation of CH4 to methanol (CH3OH) and ethanol (CH3CH2OH). This hydrophobic composite electrode can establish a directional transport channel for CH4 and effectively enhance the enrichment of CH4 on the electrode surface, forming a rich solid-liquid-gas three-phase reaction interface. The optimized 6 %PTFE-Ni(OH)2 electrode can achieve the highest alcohols’ Faradaic efficiency (FE) of 75.8 %, which is 21 times higher than that of the hydrophilic Ni(OH)2/NF electrode, and the highest concentration of alcohols can reach 9.00 mM. In addition, mechanistic analysis reveals that Ni(OH)2 is oxidized to NiOOH, which can oxidizes water to *OH, and then *OH activates and oxidizes CH4 to *CH3 and CH3OH. In addition, the formation mechanism of CH3CH2OH is only formed by coupling *OCH3 with CH4 activated on the catalyst surface. This work provides a feasible approach to tailor the hydrophilicity of catalyst to improve the efficiency of CH4 oxidation.

Plasma-induced methane catalytic cracking: Effects of experimental conditions

Low-carbon conversion of hydrocarbon fuels and feedstocks, as well as the macroscopic production of H2, are central focus in the advancement of high-value and efficient conversion of CH4. The effects of Ar addition ratio, discharge power and temperature on the results of plasma methane cracking were investigated on a dielectric barrier discharge (DBD) plasma experimental system. The results show that the addition of Ar can improve the methane conversion, and the optimal ratio of CH4 conversion to H2 production after the effect is CH4: Ar = 1:1, at which the methane conversion reaches 49.62% and the H2 selectivity reaches 52.66%. The plasma at 25 °C can make the methane conversion close to the effect of catalytic cracking at 600 °C, while the H2 selectivity is lower, the H2 generation is 32.59% lower than the latter, and the products have more C2–C4 hydrocarbon impurities. The solid byproduct resulting from the DBD plasma cracking of methane primarily consisted of carbon black, possessing an average particle size of 62.21 nm. The incorporation of Ar and the amplification of power augment the CH* radical intensities, which suggests both conditions contribute positively to the dissociation of the CH4 molecule.

OXIDATIVE REGENERATION OF METAL COMPLEX CATALYTIC SYSTEM

When carrying out thermocatalytic destruction of hydrocarbon feedstock, catalysts are deactivated due to the formation of surface coke, which blocks active centers. In order to restore their previous activity and selectivity, as well as extend their service life, a process of catalyst regeneration is carried out. One of the effective methods for restoring the original activity of deactivated catalysts is oxidative regeneration, which is based on the oxidation of coke deposits on the surface of the catalyst. The article examines the dependences of the formation of surface coke when varying the temperature regime of the process from 450 °C to 550 °C during the thermocatalytic destruction of heavy petroleum feedstock – West Siberian oil fuel oil in the presence of a new metal complex catalytic system, where the active component is a chloroferrate complex (NaFeCl4 or TCFN) in an amount 10 %, deposited on a carrier, which is a deeply decationized Ymmm zeolite of the acidic form (H-form). The patterns of oxidative regeneration of a metal-complex catalytic system were studied by distilling off highly volatile products in a flow of inert gas (helium) and oxygen-containing gas. During the experiments, it was found that with an increase in the temperature of the thermocatalytic destruction process from 450 °C to 550 °C, a slight increase in coarse deposits on the surface of the catalyst was observed from 2,6 % wt. up to 3,5 % wt. respectively. When carrying out the process of oxidative regeneration of a carbonized catalyst with air oxygen (in a flow of helium) at a temperature of 500 °C for 60 min only volatile components are initially removed, and further calcination takes up to 180 min allows for complete burning of surface coke.

Low pressure hydrocracking process for the production of a high yield of middle distillates from a high boiling hydrocarbon feedstock

Low pressure hydrocracking process for the production of a high yield of middle distillates from a high boiling hydrocarbon feedstock

Co-pyrolysis coking characteristics of nC12H26 and DHN/MeOH/EtOH/MF/DMF/H2O/H2/CO2/CO/N2 under supercritical condition

The introduction of additives or carrier gases to change the physicochemical process of endothermic fuel in a regenerative cooling channel and then regulate the carbon deposition behavior is an important coking control method. In this work, the co-pyrolysis and coking behavior of several novel additives, such as alcohols, furans, flue gas, and syngas, is compared under the supercritical condition of n-dodecane (nC12H26) with the traditional hydrogen supply agent decalin (DHN) and inert nitrogen (N2) as the basis in a 304STS tube with an inner diameter of 2 mm. Results show that the addition of methanol (MeOH) / ethanol (EtOH) / 2-methylfuran (MF) / 2,5-dimethylfuran (DMF) promotes the pyrolysis of nC12H26 and shows a strong coking trend. The coking rate of carbon monoxide (CO) addition is higher than that of carbon dioxide (CO2) addition, and the system is prone to presenting an exothermic chemical effect. The addition of hydrogen (H2) does not contribute to the hydrogen source but leads to a high coking risk at a low blend ratio. Although water (H2O) and CO2 atmospheres exhibit coke inhibition potential, they weaken the heat absorption capacity of nC12H26. The co-pyrolysis of alcohols, furans, and hydrocarbon feedstock to CO needs to be controlled in a targeted manner, so that endothermic fuels have high heat sink and low coking tendency in regenerative cooling channels.

Перспективи виробництва синтетичного бензину в Україні

DOI: 10.31081/1681-309X-2024-0-1-34-40 Specialty 161. U.D.C. 662.7 PROSPECTS FOR THE PRODUCTION OF SYNTHETIC PETROL IN UKRAINE © K.V. Shevchenko, Ph.D. in Technical Sciences, A.B. Grigorov, Doctor of Technical Sciences (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine) The article analyses the possibility of using various hydrocarbon feedstocks (including secondary ones) in the technology of synthetic motor petrol production, which, together with petrol produced by classical technology (from oil or gas condensate), can satisfy the existing demand for this type of motor fuel. It is shown that, taking into account the possible production volumes and demand for raw materials, as well as the complexity (energy intensity) of their technological processing, the most promising types of raw materials are biomass, solid fossil fuels and secondary polymers. Biomass (mainly agricultural waste) is a feedstock for biogas production, which is currently being used quite successfully in the European Union. The product of this production is methane, which can be used for energy purposes or processed into petrol and biomethanol. Another promising area in biomass processing is the direct production of alcohols (biomethanol and bioethanol), which can be used as a raw material for organic synthesis and for the production of blended petrol (e.g., grades E5, E7 and E10). Given Ukraine's reserves of various grades of coal, its processing into synthetic gasoline by gasification followed by synthesis using the Fischer-Tropsch method or hydrogenation can also be considered very promising. However, to date, these processes have not been widely used in industry due to their high energy intensity. It has been determined that secondary polymers - production and consumption wastes represented by polyethylenes (HPDE and LPDE) and polypropylene (PP) - are more promising for Ukraine than other types of raw materials. The main process for their processing is thermal or thermocatalytic pyrolysis, which produces both liquid petrol fractions (boiling point 30-210 °C) and gases, represented by ethylene, propylene and butylene. Given their conversion rate (70-90 % and 100 %, respectively), propylene and butylene can be processed into polymer gasoline, which, after purification, will be suitable for use in mixed or synthetic commercial motor gasoline. Keywords: natural gas, biomass, solid fossil fuels, polymers, processing, hydrogenation, synthesis, pyrolysis, methane, propylene, butylene, synthetic petrol. Corresponding author: A.B. Grigorov, e-mail: grigorovandrey@ukr.net

100% selective cyclotrimerization of acetylene to benzene on Ag(111).

Benzene, a high-volume chemical, is produced from larger molecules by inefficient and environmentally harmful processes. Recent changes in hydrocarbon feedstocks from oil to gas motivate research into small molecule upgrading. For example, the cyclotrimerization of acetylene reaction has been demonstrated on Pd, Pd alloy, and Cu surfaces and catalysts, but they are not 100% selective to benzene. We discovered that acetylene can be converted to benzene with 100% selectivity on the Ag(111) surface. Our temperature programmed desorption experiments reveal a threshold acetylene surface coverage of ∼one monolayer, above which benzene is formed. Furthermore, additional layers of acetylene increase the amount of benzene produced while retaining 100% selectivity. Our scanning tunneling microscopy images show that acetylene prefers square packing on the Ag(111) surface at low coverages, which converts to hexagonal packing when acetylene multilayers are present. Within this denser layer, features consistent with the proposed C4 intermediates of the cyclotrimerization process are observed. Density functional theory calculations demonstrate that the barrier for forming the crucial C4 intermediate generally decreases as acetylene multilayers are formed because the multilayer interacts more strongly with the surface in the transition state than in the initial state. Given that acetylene desorbs from Ag(111) at ∼90 K, the C4 intermediate on the pathway to benzene must be formed below this temperature, implying that if Ag-based heterogeneous catalysts can be run at sufficiently high pressure and low enough temperature, efficient and selective trimerization of acetylene to benzene may be possible.

Replacing All Fossil Fuels With Nuclear-Enabled Hydrogen, Cellulosic Hydrocarbon Biofuels, and Dispatchable Electricity

Abstract We describe a roadmap using three sets of technologies to enable base-load nuclear reactors to replace all fossil fuels in a low-carbon world. The technologies integrate nuclear, wind, solar, hydroelectricity and biomass energy sources. Base-load nuclear reactors with large-scale heat storage enable dispatchable electricity to the grid. The low-cost heat storage enables buying excess wind and solar electricity to charge heat storage for later electricity production while providing assured generating capacity. Nuclear hydrogen production facilities at the scale of global oil refineries produce hydrogen to replace natural gas (gaseous fuel) as a chemical feedstock and heat source. Single sites may have tens of modular reactors produced in a local factory to lower costs by converting to a manufacturing model for reactor construction. Nuclear heat and hydrogen convert cellulosic biomass into drop-in liquid hydrocarbon biofuels to replace fossil-fuel gasoline, diesel, jet fuel, and hydrocarbon feed stocks for the chemical industry. External heat and hydrogen inputs increase the quantities of biofuels that can be produced per unit of cellulosic feedstock, thus assuring sufficient biomass feed stocks to replace all crude oil without major impacts on food and fiber prices. The biofuel production system enables the removal of large quantities of carbon dioxide from the atmosphere that is sequestered as carbon char in the soil while recycling plant nutrients (potassium, phosphorous, etc.) to assure agricultural and forest sustainability.

Influence of aluminum zoning toward external surfaces in MFI zeolites on propene oligomerization catalysis.

Brønsted acid zeolites catalyze alkene oligomerization reactions, an important route to produce fuels and chemicals from light hydrocarbon feedstocks. Propene dimerization rates (per H+, 503 K) decrease monotonically with increasing crystallite size in MFI zeolites because heavy oligomer products remain occluded within microporous voids and restrict intrazeolite diffusion of reactants and products. Here, we show that the preferential zoning of framework Al centers and their associated H+ sites toward exterior surfaces of MFI crystallites in an "egg-shell" architecture minimizes the extent of diffusion-enhanced secondary reactions within a given crystallite, which increases both propene dimerization rates (per H+) and selectivity to true oligomer products. These results show that tailoring Al distributions to be spatially zoned toward external surfaces of medium-pore zeolite crystallites is efficacious at minimizing diffusion path lengths to increase alkene oligomerization rates and selectivity to true oligomer products.

Selectivity descriptors of the catalytic n-hexane cracking process over 10-membered ring zeolites.

Zeolite-mediated catalytic cracking of alkanes is pivotal in the petrochemical and refining industry, breaking down heavier hydrocarbon feedstocks into fuels and chemicals. Its relevance also extends to emerging technologies such as biomass and plastic valorization. Zeolite catalysts, with shape selectivity and selective adsorption capabilities, enhance efficiency and sustainability due to their well-defined network of pores, dimensionality, cages/cavities, and channels. This study focuses on the alkane cracking over 10-membered ring (10-MR) zeolites under industrially relevant conditions. Through a series of characterizations, including operando UV-vis spectroscopy and solid-state NMR spectroscopy, we intend to address mechanistic debates about the alkane cracking mechanism, aiming to understand the dependence of product selectivity on zeolite topologies. The findings highlight topology-dependent mechanisms, particularly the role of intersectional void spaces in zeolite ZSM-5, influencing aromatic-based product selectivity. This work provides a unique understanding of zeolite-catalyzed hydrocarbon conversion, linking alkane activation steps to the traditional hydrocarbon pool mechanism, contributing to the fundamental knowledge of this crucial industrial process.