Catalytic Conversion Of Hydrocarbons Research Articles

Catalytic Conversion of Hydrocarbons and Formation of Carbon Nanofilaments in Porous Pellets

Catalytic conversion of hydrocarbons occurring at metal nanoparticles in porous pellets is often accompanied by the formation of coke in the form of growing heterogeneous film-like aggregates or carbon nanofilaments. The latter processes result in deactivation of metal nanoparticles. The corresponding kinetic models imply the formation and growth of film-like coke aggregates. Herein, I present an alternative generic kinetic model focused on the formation and growth of carbon nanofilaments. These processes are considered to deactivate metal nanoparticles and reduce the rate of reactant diffusion in pores. In this framework, the kinetically limited reaction regime is described by simple analytical expressions. The diffusion-limited regime can be described as well but only numerically. The model presented can be used for interpretation of experimental results.Graphical

From hydrocarbon processing to hydrocarbon synthesis: Advances in catalytic technology

Hydrocarbon is a vital kind of chemical compounds to form liquid fuels and polymer monomers. It is the backbone of the national economy and is closely related to people’s lives. Hydrocarbon processing refers to the production of hydrocarbon with different structures through the separation or chemical conversion of petroleum resources, such as refined petroleum products, which is a top-down way. Hydrocarbon processing, including series of chemical conversion reactions such as carbon-carbon bond cleavage, covers the major processes of petroleum refining and petrochemicals, and is the main production route for hydrocarbon products. Hydrocarbon synthesis uses non-petroleum-based resources such as coal, natural gas, and biomass as carbon source, through chemical conversion such as carbon-carbon bond coupling and carbon chain growth. The hydrocarbon synthesis is a route that assemblies small molecules to target hydrocarbon products by bottom-up way. It covers the main processes of the new coal chemical industry and natural gas chemical industry, and is also an important component of the future biomass conversion and renewable energy industry. Hydrocarbon synthesis is an important supplement to current and future production of hydrocarbon. But, the shortage of oil resources is inevitable. The shale gas revolution has also brought new options to the global en-ergy economy. Facing the challenges of resource and environmental, traditional hydrocarbon production technology has been unable to meet the needs of economic development. The sustainable development of the energy and chemical industry is urgent, and the direction is clear. (1) To increase the efficiency of the use of petroleum resources to reduce energy consumption and carbon emissions. (2) The development of new hydrocarbon synthesis methods based on non-oil resources such as C1 platform reactions. Many new catalytic reaction processes and routes are involved in hydrocarbon processing and hydrocarbon synthe-sis. The catalytic conversion of hydrocarbons constitutes a complex reaction network, thus solving the C–C, C–H bond activation, shape-selectivity conversion, C–C bond coupling and chain growth control is an important problem in cata-lytic research. In particular, in order to realize the industrialization of catalytic technologies such as hydrocarbon pro-cessing and hydrocarbon synthesis, it is necessary to build a bridge from the laboratory (theory) to the industry (engi-neering). The key scientific issues that need to be solved can be summarized as: synergy between important elements such as “systematic vs. elementary”, and “apparent vs. intrinsic”.

Hydrogen applications and research activities in its production routes through catalytic hydrocarbon conversion

Abstract The statistical information on the share of hydrogen sector-wise consumption indicates that 95% of the total consumption is utilized in ammonia synthesis, petroleum refining processes and methanol production. We discuss how hydrogen is used in these processes and in several smaller-scale manufacturing industries. We also present the trend of hydrogen used as fuel, and as an energy carrier in fuel cells for generating electricity, powering hydrogen vehicles, as well as in aerospace applications. Natural gas caters for approximately half of the total hydrogen production resources. Therefore, the scope is emphasized on relatively recent developments in research activities related to the conventional catalytic hydrocarbon processing technologies for the production of hydrogen derived from natural gas (methane), which are steam methane reforming, partial oxidation of methane and autothermal reforming. Hydrocarbon decomposition is included due to its potential to be industrialized in the future, and its benefits of producing clean hydrogen without emissions of greenhouse gases and generating carbon nanofibers or nanotubes as by-products that have the potential in various emerging applications. Attention is given to the efforts toward achieving hydrocarbon conversion improvements, energy savings through thermally efficient operation and reduced operational costs through minimization or elimination of coke formation in the catalytic processes.

Development of an Analytical Design Tool for Monolithic Emission Control Catalysts and Application to Nano-Textured Substrate System

Abstract An analytical transport/reaction model was developed to simulate the catalytic performance of ZnO nanowires as a catalyst support. ZnO nanowires were chosen because they have easily characterized, controllable features and a spatially uniform morphology. The analytical model couples convection in the catalyst flow channel with reaction and diffusion in the porous substrate material; it was developed to show that a simple analytical model with physics-based mass transport and empirical kinetics can be used to capture the essential physics involved in catalytic conversion of hydrocarbons. The model was effective at predicting species conversion efficiency over a range of temperature and flow rate. The model clarifies the relationship between advection, bulk diffusion, pore diffusion, and kinetics. The model was used to optimize the geometry of the experimental catalyst for which it predicted that maximum species conversion density for fixed catalyst surface occurred at a channel height of 520 μm.

Nonconventional treatment of sewage sludge using cement kiln dust for reuse and catalytic conversion of hydrocarbons

Sewage sludge represents a critical environmental issue in Egypt. Large quantities of CKD are emitted from cement factories. It has negative impacts on humans, animals, plants, lands, water, and all remaining environment. It causes serious problems on the national level. Besides using CKD for sludge treatment and reuse as soil conditioner, a new scenario is to use it as catalytic convertor of some hydrocarbons. Results showed that CKD is used to separate the organic matters and suspended solids, reduce the organic micropollutants, scavenge heavy metals, and destruct viruses, parasites, and all pathogenic bacteria. The dehydrogenation of isopropanol to acetone and alcohol condensation of the produced acetone to give methyl isobutyl ketone over different catalyst samples was studied using a flow technique under normal pressure. Results revealed that treatment of raw sludge led to an increase in catalytic activity toward acetone formation by 50 % at 400 °C. A treatment system was proposed for continuous operation.

Direct Observation of Kinetically Competent Surface Intermediates upon Ethylene Hydroformylation over Rh/Al2O3 under Reaction Conditions by Time-Resolved Fourier Transform Infrared Spectroscopy

Time resolved Fourier transform infrared (FTIR) spectroscopy with millisecond resolution (rapid scan technique) has been employed to detect multiple kinetically relevant surface intermediates in heterogeneous catalytic hydroformylation of ethylene over alumina-supported Rh nanoparticles at 443 K (1 atm total pressure). While corresponding single component C2H4 hydrogenation over Rh/Al2O3 nanoparticle catalysts yields ethane, no hydrogenation of transient ethyl intermediate is observed in the presence of CO. Hence, complete product selectivity is observed with respect to branching between hydroformylation and direct ethylene hydrogenation to ethane. Surface ethyl intermediate (C2H5Rh: 2876, 2855, 1190 cm−1) is converted to propionyl intermediate (C2H5C(═O)Rh: 2869, 1675 cm−1) by reaction with CO with a time constant of 2.7 s. The spectral assignments of propionyl were confirmed by the observation of 13C shifts. Hydrogenation of propionyl to propionaldehyde with its characteristic C═O (1737 cm−1; 13C═O at 1696 cm−1) and aldehyde C−H absorption (2715 cm−1) is the rate -limiting step and proceeds with a time constant of 4.4 s. This is the first time-resolved observation of consecutive elementary steps of heterogeneous catalytic hydrocarbon conversion under reaction conditions.

Catalytic conversion of hydrocarbons in a heated tube at a nearly stoichiometric vapor to gas ratio

A method for the catalytic vapor and carbon dioxide conversion of hydrocarbons is suggested. The conversion was performed in heated tubes at a nearly stoichiometric vapor-to-gas ratio. The energy intensity of the process and the rate of oxidants (H2O and/or CO2) thus decreased, while the lifetime of the catalyst increases.

II. Electrical Properties of Ni/Silica Gel and Pt/γ-Alumina Catalysts in Relation to Catalytic Activity

The catalytic activity of silica gel and silica gel—supported nickel (2, 5, and 8 wt% Ni) and γ-alumina—supported platinum (0.3 and 0.6 wt% Pt) was studied for n-hexane or n-pentane cracking and cyclohexane dehydrogenation adopting pulse technique. The results showed that Pt/γ-alumina could be a selective catalyst for cyclohexane dehydrogenation reaction. Ni/silica gel catalyst was a good cracking catalyst, the activity of which increased by increasing the metal content up to 8% Ni. For cyclohexane, dehydrogenation over Ni/silica gel, the activity increased by increasing the metal loading. N2 sorption characterizations showed that both silica gel- and γ-alumina—supported catalyst samples exhibited mesoporous structures. Silica gel and silica gel—supported samples have ink-bottle type pores while γ-alumina and γ-alumina—supported platinum samples have platelike pores. BET surface area and total pore volume decreased by increasing metal loading for both catalyst samples. Electrical properties of pure γ-alumina and silica gel supports were functions of metal content and frequency of the applied field. The increase of conductivity is considered a good indicator of the decrease in the activation energy (increase of catalytic activity). The observed increase in conductivity with the increase of metal loading may be due to increase in the mobility of the free charge carriers (i.e., ions and free radicals taking part in the mechanism of catalytic conversion of hydrocarbons over the catalyst polarized active centers that increased by increasing metal loading). These charge carriers diffuse in the bulk of pores and reach electrodes where they discharge, giving rise to diffusion impedance (Warburg impedance).

Synthesis and characterization of hydroxy-chromium pillared bentonite

Chromium pillared clays, in particular, have attracted the researchers attention after being tested as catalyst in a wide range of reactions, like catalytic conversion of hydrocarbons, ester formation and elimination of water from alcohols. The chromium oligomers used for intercalation were prepared by addition of Na2CO3 to a chromium nitrate solution or chromium chlorite solution and the mixture is heated at 80°C for 36 h. The pillaring clay is obtained by heating intercalated bentonite at 360°C under vacuum. Several Techniques, X-ray diffraction, N2 adsorption-desorption isotherms and chemical analysis have been used to characterize and to compare the properties of the materials synthesized. Our study consists in determination of the influence of the intercalated OH-Cr group on the structure of Tunisian bentonite. The results showed that the interlamellar distances of pillared bentonite ranged from 17 to 21 A. In addition, the synthesized clays exhibit increased BET surface areas and higher micro pore volumes compared with unmodified clay. On the other hand, the micro pore surface area, the micro pore volume and the d (001) spacing after pillaring increased with the amount of chromium retentions.

Adsorption and catalytic conversion of hydrocarbons on nanosized gold particles immobilized on alumina

Gold and nickel particles immobilized on alumina were prepared by the metal vapor synthesis and anionic adsorption methods. The dispersion of metals was determined by X-ray diffraction and transmission electron microscopy. The activity of nanoparticles, tested in model catalytic reactions of CCl4 addition to multiple bonds and allyl isomerization of allylbenzene, changes in a wide range (from 1 to 3000 (mole of product) (mole of Au)−1 h−1) and is parallel to the chromatographically measured heats of adsorption of the corresponding unsaturated substrates. The heat of adsorption of unsaturated hydrocarbons can serve as a criterion for the efficiency of the gold-containing catalyst in olefin conversion.

Reforming Catalysts of the PR Family: Scientific Foundations and Technological Advancement

Results of investigations of the state of active sites in aluminoplatinum reforming catalysts (RCs) are summarized. Laws governing the formation and the role of platinum ionic species in the adsorption and catalytic conversion of hydrocarbons are presented. Strategies for the design of highly efficient catalysts, the development of catalyst manufacturing technologies, and operation in the production of motor fuels and aromatic hydrocarbons are formulated. Data are reported on the full-scale operation of catalyst PR-51/04 (PR-71), a new RC, and full-scale tests of the Biforming process, a new process for motor fuel production by coprocessing C3-C4 hydrocarbon gases and gasoline fractions.

Catalytic Conversion of Hydrocarbons in Zeolites from First Principles

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic conversion of hydrocarbons over zeolites from first principles

Conversion of hydrocarbons over zeolites is an important industrial process. In the presence of zeolites, hydrocarbons are converted either to smaller molecules (cracking), or they recombine to branched compounds (isomerization). The microscopic steps of the conversion, however, are still not fully understood. This work brings together our previously published as well as new data into a coherent picture of hydrocarbon catalysis. We perform static and molecular dynamics DFT calculations on gmelinite zeolite with adsorbed linear saturated and unsaturated hydrocarbon molecules. Our simulations indicate that the conversion of olefins can proceed through the chemisorption inside the zeolite because species chemisorbed at specific sites are more stable than physisorbed molecules. Desorption at increased temperatures (400–700 K) produces unstable protonated molecules. These are found to be relatively long-lived, being stabilized in the zeolite surroundings. The collapse of protonated molecules then produces branched isomers. Protonation of saturated molecules leads to cracking. The calculated activation energies of both isomerization and cracking are in reasonable agreement with experimental data.

Hydrocarbon hydrogenation and dehydrogenation reactions in microfabricated catalytic reactors

Analytical chips to lower the cost and increase the effectiveness of chemical analyses, well proven in biochemical and biomedical applications, have a bright future for organic and inorganic reaction analyses. We demonstrate the use of microfabricated catalytic reactors constructed with silicon wafer technology for catalytic hydrocarbon conversion. The details of fabricating the devices are presented, as is the configuration for using them to characterize a heterogeneous gas–solid catalytic reaction. We present the results of a study of the reaction of cyclohexene in the presence of hydrogen over a platinum thin-film catalyst. In this experiment, we determined what factors affect the selectivity of the conversion to either cylcohexane (hydrogenation) or benzene (dehydrogenation). A reactor model based on published rate law data corroborated the behavior of the reactors for operation below 120°C. We verified literature reports of the decline of activity with temperature and observed a simultaneous shift in selectivity. These experiments demonstrate the value of microreaction devices for acquiring data traditionally taken by bulkier, more costly, and less efficient, bench-scale reactors.

INVESTIGATION OF PROLONGED DEACTIVATION-REGENERATION REGIMES ON THE DEHYDROGENATION ACTIVITY OF PLATINUM/ALUMINA CATALYST

The various types of coke found deposited on a deactivated Pt/Al2O3 reforming catalyst are described. They are claSsified into major types: oxidiZable (primary) coke, reducible (secondary) coke and non oxidizable and non reducible (tertiary) coke. Primary coke is generally non toxic to catalytic hydrocarbon conversion as its removal restores initial catalyst activity. The secondary and tertiary forms are, however, toxic to this reaction. A methodology for the prolongation of reforming catalyst life is evident from these results. In the new method, secondary coke is also removed from the catalyst surface subsequent to primary coke removal. Results of the application of this methodology using accelerated aging of Pt/Al2O3 catalyst is presented. The overall catalyst life was extended for up to 52 deactivation-regeneration cycles from the 23 previously reported. Catalyst life was not correlated with the oxidizable and reducible coke content. These profiles were found to be aperiodic and exhibited a nonlinear dynamic behavior. In contrast, catalyst life per cycle of deactivation-regeneration correlate with the rate of oxidizable coke deposition. The model coking reaction investigated was the dehydrogenation of cyclohexane to benzene in nitrogen carrier at 430°C on a commercial Pt/Al2O3 catalyst using a Berty CSTR.

Chemistry of petroleum hydrocarbons. Directions in research

Research in petroleum chemistry has been the basic direction of scientific research in the Department of Organic Chemistry and Petroleum Chemistry since it was founded in 1927. Initiated by AcademicianS. S. Nametkin, this direction was continued and developed in the research of his students and followers:V. I. Isagulyants, A. V. Topchiev, N. S. Nametkin, and G. M. Egorova [1]. Many studies were conducted together with the Institute of Petrochemical Synthesis, Academy of Sciences of the USSR (formerly Petroleum Institute, Academy of Sciences of the USSR) and Institute of Geology and Processing of Fossil Fuels, Academy of Sciences of the USSR. They include studies of the composition of crude oils, synthesis of model hydrocarbons, and catalytic conversion of hydrocarbons. Such well-known scientists in our country and abroad asAl. A. Petrov andI. V. Kalechits participated in this research.

Kinetics of nickel-catalyzed purification of tarry fuel gases from gasification and pyrolysis of solid fuels

As a contribution to develop a process for the chemical upgrading of tarry fuel gases, the kinetics of the catalytic conversion of hydrocarbons on a commercial nickel-catalyst in the presence of H 2 and H 2O (Süd-Chemie, G 117) were studied. Besides single model hydrocarbons (naphthalene, benzene and methane) and their mixtures, a feed gas obtained by coal pyrolysis was catalytically converted. The experiments were performed in a tubular flow reactor at a total pressure of 160 kPa, a residence time with respect to the empty reactor up to 0.1 s and a particle diameter of 1.5 or 19 mm, varying with the temperature (450–1150°C) and concentrations of H 2, H 2O and the hydrocarbons. The influence of H 2S and NH 3 on the activity of the catalyst was also studied. The results indicate that the Ni-catalyst used is suitable to convert tarry fuel gases into a clean fuel or reduction gas, even if H 2S is present. Although the rate of chemical reaction of the hydrocarbons on the Ni-catalyst is substantially reduced by hydrogen sulphide, a rest activity still remains, and all higher hydrocarbons are completely converted to CO, H 2 and CO 2 at a temperature of about 1000°C (0.3 vol% H 2S; τ=0.1 s). In contrast to H 2S, NH 3 has no influence on the conversion of hydrocarbons on the Ni-catalyst, and is just converted to N 2 and H 2. In a reactor of industrial scale, the overall reaction rate of hydrocarbon conversion is significantly affected by gas film diffusion (particle diameter: 19 mm), and is therefore only slightly influenced by H 2S.

99/02894 CHP (cogeneration of heat and power) in the pulp industry using black liquor gasification: thermodynamic analysis

As a contribution to develop a process for the chemical upgrading of tarry fuel gases, the kinetics of the catalytic conversion of hydrocarbons on a commercial nickel-catalyst in the presence of H2 and H2O (Süd-Chemie, G 117) were studied. Besides single model hydrocarbons (naphthalene, benzene and methane) and their mixtures, a feed gas obtained by coal pyrolysis was catalytically converted. The experiments were performed in a tubular flow reactor at a total pressure of 160 kPa, a residence time with respect to the empty reactor up to 0.1 s and a particle diameter of 1.5 or 19 mm, varying with the temperature (450–1150°C) and concentrations of H2, H2O and the hydrocarbons. The influence of H2S and NH3 on the activity of the catalyst was also studied.The results indicate that the Ni-catalyst used is suitable to convert tarry fuel gases into a clean fuel or reduction gas, even if H2S is present. Although the rate of chemical reaction of the hydrocarbons on the Ni-catalyst is substantially reduced by hydrogen sulphide, a rest activity still remains, and all higher hydrocarbons are completely converted to CO, H2 and CO2 at a temperature of about 1000°C (0.3 vol% H2S; τ=0.1 s). In contrast to H2S, NH3 has no influence on the conversion of hydrocarbons on the Ni-catalyst, and is just converted to N2 and H2.In a reactor of industrial scale, the overall reaction rate of hydrocarbon conversion is significantly affected by gas film diffusion (particle diameter: 19 mm), and is therefore only slightly influenced by H2S.

99/01736 Implementation of a novel method for gasification of solid fuel and waste in SVZ Schwarze Pumpe center for waste recovery : Anon Elektr. Stn., 1998, (3), 57–62. (In Russian)

As a contribution to develop a process for the chemical upgrading of tarry fuel gases, the kinetics of the catalytic conversion of hydrocarbons on a commercial nickel-catalyst in the presence of H2 and H2O (Süd-Chemie, G 117) were studied. Besides single model hydrocarbons (naphthalene, benzene and methane) and their mixtures, a feed gas obtained by coal pyrolysis was catalytically converted. The experiments were performed in a tubular flow reactor at a total pressure of 160 kPa, a residence time with respect to the empty reactor up to 0.1 s and a particle diameter of 1.5 or 19 mm, varying with the temperature (450–1150°C) and concentrations of H2, H2O and the hydrocarbons. The influence of H2S and NH3 on the activity of the catalyst was also studied.The results indicate that the Ni-catalyst used is suitable to convert tarry fuel gases into a clean fuel or reduction gas, even if H2S is present. Although the rate of chemical reaction of the hydrocarbons on the Ni-catalyst is substantially reduced by hydrogen sulphide, a rest activity still remains, and all higher hydrocarbons are completely converted to CO, H2 and CO2 at a temperature of about 1000°C (0.3 vol% H2S; τ=0.1 s). In contrast to H2S, NH3 has no influence on the conversion of hydrocarbons on the Ni-catalyst, and is just converted to N2 and H2.In a reactor of industrial scale, the overall reaction rate of hydrocarbon conversion is significantly affected by gas film diffusion (particle diameter: 19 mm), and is therefore only slightly influenced by H2S.

Synthetic crystalline aluminosilicates for the catalytic conversion of hydrocarbons in petrochemical processes

Synthetic crystalline aluminosilicates for the catalytic conversion of hydrocarbons in petrochemical processes