Production Of Light Hydrocarbons Research Articles

Microwave-assisted pyrolysis of industrial biomass waste: Insights into kinetic, characteristics and intrinsic mechanisms

Microwave-assisted pyrolysis is the preferred technology for enhancing the production of fuels and valuable chemicals. Therefore, pyrolysis experiments of furfural residue (FR) were performed using microwave equipment without microwave-absorbing additives. Further, to explore the interactions and intrinsic mechanisms of biomass components, thermogravimetric (TG), kinetic calculation, Py-GC/MS and TG-MS were also employed. Results showed that the temperatures and catalysts both affect the yields and compositions of products. Moreover, kinetic calculations showed a high-level consistency between FR pyrolysis and P3 mechanism. The product analysis also helps in the resolution of pyrolysis mechanism. For example, crystal substances in biochar were mainly SiO2, K2SO4, KAlSi3O8, and K2SO4 enhanced the reaction degree of biomass. While for bio-oil, the yield reached maximum (∼25 wt%) at ∼550 °C. The pH of bio-oil was acidic (2-4.3), and the main product in bio-oil was phenols, which was found the highest (84.63%) at 700oC. Interestingly, the interaction of cellulose and lignin promoted light hydrocarbon production. This research unveils innovative perspectives on the intrinsic mechanisms underlying microwave-assisted pyrolysis of biomass, which provides guidance for optimization of the microwave-assisted pyrolysis technology.

Enhancement of light hydrocarbon production from polypropylene waste by HZSM-11-catalyzed pyrolysis

Herein, a mixture of real polypropylene (PP) waste was pyrolyzed with a HZSM-11 catalyst as a potential method to recover light hydrocarbons (C ≤ 12), the potential feedstock for value-added chemicals and fuels, from polyolefin plastic waste. Using the HZSM-11 in the PP waste mixture pyrolysis noticeably improved the yield of gas pyrolysate and oil in compensation for the yield of wax (i.e. hydrocarbons of C > 20) and solid residue particularly at a higher temperature. In addition, the selectivity of C3–C12 in the PP-waste mixture-derived pyrolysate was markedly increased by the HZSM-11. The highest yield of light hydrocarbons was ≈40 wt% (per mass of the feedstock) achieved at 700 °C with the HZSM-11 catalyst. Despite 7.9 wt% coke deposition on the HZSM-11 after its use in the pyrolysis of the PP waste mixture, the catalyst could be reusable for at least three times after regeneration. The experimental results demonstrate that HZSM-11 has the potential for being a promising catalyst to valorize polyolefin waste into value-added chemicals.

Characterization Product of Coconut Shell Gasification as Liquid Fuel Through Catalytic Cracking Process with Activated Natural Zeolite Catalyst

There are 3 types of general fuels widely used, namely solid, liquid and gaseous fuels. Liquid fuel is the most frequently used fuels because its the easiest to use and for transportation. Type of liquid fuel commonly used is gasoline and diesel. However, the amount of fossil fuels is dwindling, so that at this time a substitute fuel from biomass and its derivatives is needed. One of the commonly used natural resources is biomass. This biomass is used not only directly but can also be used indirectly. One of them is the gasification process. The gasification process produces 3 products, gas, solid and liquid. The liquid gasification product is rarely used because its considered a B3 waste. The liquid gasification product is tar. Tar is a substance composed of various long chain hydrocarbon compounds. Therefore, tar has the potential to be processed into fuel. Therefore, currently we process tar as a fuel by cracking the tar to obtain light hydrocarbon products which are equivalent to gasoline or diesel. This process uses a natural zeolite catalyst to break down these hydrocarbons. The natural zeolite used is zeolite originating from Padalarang, West Java. This natural zeolite has been processed to obtain a suitable Si/Al content for cracking. After the cracking process with catalyst, liquid fuel will be produced. GCMS test results for liquid products is component acetic acid with a concentration of 5.87.2%, phenol 5.55.9% and C8H10O2 and C8H10O3 9.110.5%. Based on these components, the resulting liquid fuel is equivalent to gasoline.

Catalytic hydropyrolysis of lignin: Insights into the effect of Ni catalyst and hydrogen using ReaxFF molecular dynamics simulation

Catalytic hydropyrolysis (CHP) of lignin as an emerging technology provides an efficient way of utilizing waste resources and promoting the production of alternative fuels and valuable bio-based products. The reinforcement of selective catalysts and hydrogen facilitates the overall conversion process but the mechanism remains difficult to clarify due to the complex nature of the system. This work employs a ReaxFF reactive molecular dynamics simulation method to explore the CHP of lignin dimer DMPD and the reaction mechanism at the molecular level. The results suggest that the hydropyrolysis (HP) system achieves a deoxygenation degree of 12.0 % for liquid products and the incorporation of hydrogen into pyrolysis suppresses the production of CO while promoting H2O and CH4 generation. The introduction of the Ni catalyst in the CHP system results in a liquid product yield of 68.9 wt % at 2000 K with a higher deoxygenation degree of 14.6 % due to the participation of a large amount of •H radicals species dissociated on the catalyst surface. The CHP reactions remarkably promote the production of phenols such as guaiacol and catechol and catechol is more likely to generate from the dynamic evolution of reaction intermediates. The integrated system also improves the production of H2O and light hydrocarbons like CH4 and C2H6. The first-order kinetic model reveals that the average activation energies of C-C, C-H, C-O bonds, and DMPD in the CHP system are significantly reduced to 113.12, 55.79, 59.99, and 132.17 kJ/mol in contrast to HP. The results indicate that the CHP system is more favorable for producing desirable liquid products with lower energy barriers.

Devolatilization of Polypropylene Particles in Fluidized Bed

Gasification of plastic waste is an emerging technology of particular interest to the scientific world given the production of a hydrogen-rich gas from waste material. Devolatilization is a first step thermochemical decomposition process which is crucial in determining the quality of the gas in the whole gasification process. The devolatilization of polypropylene (a key compound of plastic waste) has been investigated experimentally in a bench-scale fluidized bed reactor. Experimental tests were carried out by varying two key parameters of the process—the size of the polypropylene spheres (8–12 mm) and temperature (650–850 °C). Temperature shows the highest influence on the process. Greater molecular cracking results were more pronounced at higher temperatures, increasing the production of light hydrocarbons along with the formation of solid carbon residue and tar. The overall syngas output reduced, while the H2 content increased. Furthermore, a pseudo-first-order kinetic model was developed to describe the devolatilization process (Eapp = 11.8 kJ/mol, A1 = 0.55 s−1, ψ = 0.77).

Proposal and Investigation of a Novel Process Configuration for Heavy Fuel Oil Gasification and Light Hydrocarbon Production

Proposal and Investigation of a Novel Process Configuration for Heavy Fuel Oil Gasification and Light Hydrocarbon Production

The distribution and emission of CO2, CH4 and light hydrocarbons in an anticyclonic eddy of the Kuroshio extension

Mesoscale eddies are energetic and swirling circulations that frequently occur in the open ocean. The effects of mesoscale eddies on the biogeochemical cycling of climate-relevant gases remain poorly constrained. We investigated the distribution and air-sea fluxes of CO2, methane, and five non–methane hydrocarbons (NMHCs) in an anticyclone eddy of Kuroshio Extension during September 2019. Within eddy core, intense stratification hindered the replenishment of nutrients and favored the growth of small-size phytoplankton, such as Prochlorococcus. Seawater pCO2 decreased from 406.1 μatm at the eddy outside to 377.5 μatm at the eddy core, accompanied by a decrease in surface seawater temperature from 26.7 °C to 25.2 °C. The vertical distribution of methane (0.3-9.9 nmol L-1) was influenced by the eddy process, with a maximum at 80 m in the eddy core, which might be attributed to the degradation of phosphonates sustained by Prochlorococcus. The concentrations of five NMHCs (ethane, ethylene, propane, propylene, and isoprene) ranged from 17.2-126.2, 36.7-168.1, 7.5-29.2, 22.6-64.1, 54.5-172.1, 3.5-27.9 pmol L-1, respectively. Isoprene correlated well with Chl-a concentrations at the eddy core, while no significant correlation was observed at the eddy outside. Air-sea fluxes of CO2 and isoprene associated with the eddy core were higher than those of the eddy outside, while the maximum ventilation of methane and other NMHCs (ethane, ethylene, propane, and propylene) was found at the eddy outside. Collectively, physical processes such as eddies impact the production and distribution of light hydrocarbons in seawater and further influence their regional emissions to the atmosphere.

Thermodynamic analysis of bio-oil model compounds to light hydrocarbon

The present work uses the total Gibbs free energy minimization approach to analyze the thermodynamic equilibrium analysis of bio-oil model compounds to light hydrocarbons. A mixture of model compounds was subjected to co-cracking with methanol and ethanol, and at a range of temperatures (300–1200 °C) and pressures (1–50 bars), the equilibrium compositions were calculated as a function of the hydroxypropanone-acetic acid-ethyl acetate/methanol ratio (HAEM) and the hydroxypropanone-acetic acid-ethyl acetate/ethanol ratio (HAEE). Possible reactions were analyzed, revealing that methane is the predominant product, followed by hydrogen, carbon monoxide, carbon dioxide, and propionic acid. The production of light hydrocarbons, including ethylene, ethane, propylene, and propane, was minimal. Notably, the co-reactant ethanol (HAEE 1:12) in the co-cracking of bio-oil model compounds demonstrated a significant effect on the production of methane, ethylene, and propylene at 1 bar pressure and 300 °C (for methane production) and 1200 °C (for ethylene and propylene production).

Pyrolysis products from various types of plastics using TG-FTIR at different reaction temperatures

Pyrolysis products of low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and municipal plastic waste at different reaction temperatures were predicted in the current study using a newly developed thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) method. The experiments revealed that pyrolysis products of LDPE and PP at 500 °C were almost wax. Above 600 °C, wax formed from LDPE and PP almost disappeared, while the production of light hydrocarbons was enhanced. In the cases of LDPE and PP, the benzene and toluene formations were clearly observed above 800 and 700 °C, respectively. For PS, styrene was observed as the major component at 500–800 °C. With increasing temperature, the formations of alkenes, benzene, and toluene were enhanced at the expense of styrene. Different from other plastics, PET produced a pyrolysis vapor containing mainly CO2 and CO. FT-IR spectra of PET were almost unchanged despite increasing temperature above 600 °C. In the case of municipal plastic waste, the product distribution was similar to those of LDPE and PP. The new TG-FTIR method turned out to be an effective tool to predict pyrolysis products, especially gases products having low molecular weights.

Assessment of the chemical looping gasification of wheat straw pellets at the 20 kWth scale

In this work, the Biomass Chemical Looping Gasification (BCLG) process was evaluated for syngas production at the 20 kWth scale using wheat straw pellets as the fuel feedstock and ilmenite as the oxygen carrier. The effect of different operational variables –namely the fuel reactor temperature, the mean residence time of solids in the fuel reactor, the oxygen-to-biomass ratio (controlled by the oxygen fed into the air reactor) and the gas velocity in the carbon stripper– on the process performance and the syngas yield was analyzed. Interestingly, smooth operation of the CLG unit was observed and no agglomeration issues detected. In addition, char produced during devolatilization still retained its initial pellet shape and unconverted char pellets were elutriated from the fuel reactor mixed with the finer oxygen carrier particles. Both steady-state and transition periods were evaluated to have a complete overview of the process. Transition periods were characterized by a different oxygen transfer rate in the air and fuel reactors. Steady state was reached when the oxygen transference rate was the same in both reactors. In this sense, the oxygen transference rate in the fuel reactor was the main factor affecting the syngas yield and the cold gas efficiency. Also, the temperature and mean residence time of solids in the fuel reactor showed a considerable effect on the char conversion and, consequently, on the syngas yield. However, operating conditions hardly affected the production of light hydrocarbons (CH4 and C2-C3) and tar, which were maintained roughly constant throughout the experimental campaign.

Improved Light Hydrocarbon, Furans, and BTEX Production from the Catalytic Assisted Pyrolysis of Agave salmiana Bagasse over Silica Mesoporous Catalysts

The pyrolysis of the biomass Agave salmiana bagasse (10 K/min, ambient to 700 °C) was investigated in the absence and presence of Aerosil and MCM-41 catalysts. MCM-41 was synthetized using a typical hydrothermal method and characterized with XRD, SAXS, SEM, TEM, and nitrogen physisorption to confirm the presence of unidimensional 3.4 nm diameter pores. Pyrolysis products were monitored online with mass spectrometry (MS), analyzing the production of 29 different compounds, clustered in several groups, namely, olefins (ethene, 2-butene, 1,3-butadiene), oxygenated compounds (methanol, 2-methylbutanol, acetic acid), furan derivatives (furan, furfural, 2-methylfurane), and aromatic compounds (BTEX). Complete decomposition of the cellulose and hemicellulose content of the biomass was observed at temperatures below 400 °C. Lignin decomposition was completed by 550 °C. Catalyst-assisted pyrolysis showed reduced acetic acid and methanol formation with Aerosil and MCM-41. The use of Aerosil does not affect the overall production of olefins, yet increases benzene yield, while reducing the production of phenol, furan, and furan derivatives. With MCM-41, there is increased production of olefins, furan, furan derivatives, cyclohexanone and BTEX, yet phenol production is decreased. At temperatures below 400 °C, the product formation pattern is comparable to non-catalytic pyrolysis.

Thermochemical recycling of tall oil pitch in a dual fluidized bed

Crude tall oil is a by-product obtained from the manufacture of chemical wood pulp. The residue obtained after the distillation of this product is known as tall oil pitch (TOP). This complex fraction is a highly viscous liquid that consists mainly of free fatty acids, fatty acids derivatives, rosin acids and additives. Given its complex composition, it is commonly used as fuel for heat production. In this work, steam cracking is proposed as an alternative treatment for this residue. Steam cracking can convert TOP into a valuable product gas that can be used in different applications including the production of green chemicals, moving towards a carbon circular economy. The experimental tests were performed in the Chalmers pilot scale Dual Fluidized Bed, consisting of a steam cracker and a combustor. For these experiments, the thermochemical decomposition of 150–175 kg/h TOP was performed at the steam cracker at two different temperatures (775 and 825 °C) to evaluate the influence of this parameter on the obtained products. Wood pellets were also tested as reference material for the highest temperature. The distribution of the obtained products was analysed. Results show that TOP can be regarded as a by-product instead of a residue and used as feedstock for the recovery of chemical building blocks and syngas via thermochemical recycling. Between 40 and 50 % of the carbon present in the fuel is kept in the permanent gases, while about 20 % is in aromatic hydrocarbons. Compared to biomass, the aromatics yield obtained for TOP is much higher (190 g/kg for TOP and 13 g/kg for biomass). Among the species found, benzene, toluene and xylene, represent between 62 and 72 % of the total measured aromatics. Regarding the gas fraction, the production of valuable light hydrocarbons (such as ethylene and propylene) is more pronounced in the TOP residue than in the biomass. In addition, an energy balance over the system was estimated and showed that TOP thermochemical recycling can be self-sustained in a Dual Fluidized Bed if the non-valuable products are combusted. The results obtained in this work indicate that this TOP could be an appealing option to consider as a source of biorefinery revenue leading to the circular use of waste.

Characteristics of light hydrocarbons under the superimposed influence of biodegradation and subsequent thermal maturation

Recently, several large light oil and condensate reservoirs were discovered in the Tarim and Junggar basins (China). In these superimposed petroliferous basins, the early formed palaeo-oil reservoirs experienced complex tectonic movements, resulting in complex secondary alterations (e.g., biodegradation and water washing), known to alter the chemical composition of crude oils. Thus, crude oils previously modified by biodegradation exhibit significantly different generation potential, chemical composition, and timing of generation (in terms of light oils/condensates), during subsequent thermal alteration. To elucidate the influence of biodegradation on crude oil cracking (to form light hydrocarbons), we artificially matured four crude oils of the same origin (with varying degrees of biodegradation) to various maturity levels, using programmed-temperature gold tube closed-system pyrolysis. The yields, molecular parameters, and stable carbon isotope ratios of the light hydrocarbon products derived from the matured oils were analysed and compared. The preferential removal of n-alkanes and branched alkanes during biodegradation significantly reduced the generation potential of light hydrocarbons. Under the superimposed influence of biodegradation and subsequent thermal alteration, referred to as superimposed secondary alteration (SSA), a few hydrocarbon ratios used for oil–oil correlations were severely modified. Most maturity-related light hydrocarbon parameters of the pyrolysis products derived from the biodegraded oils achieved maximum values at a lower maturity (Easy%Ro) than that observed for non-biodegraded crude oil. At 0.5–1.4 Easy%Ro, SSA caused the depletion of 13C in most light hydrocarbons, due to an increased sourcing from the biodegradation-resistant fractions of the oil. Such carbon isotopic differences decreased with increasing maturity.

Synergetic effect of steam and activated tyre char on the selective production of levoglucosan-rich bio-oil from catalytic pyrolysis of wood chips

The catalysts used in the pyrolytic bio-oil upgrading process are either expensive or not efficient enough. This research aims to investigate and improve the catalytic capability of tyre char (TC), an otherwise low-value waste, as an effective catalyst for upgrading bio-oil derived from the pyrolysis of eucalyptus wood chips. Efforts were specifically made to tailor the TC properties to improve the selectivity of levoglucosan (LGA), a value-added bio-chemical in bio-oil. Experiments were carried out in a two-stage fixed-bed reactor in the absence and presence of steam (30 vol%) at different heating rates (10 °C/min and 110 °C/min). By using 3-Flex, SEM-EDX, XRD, XRF, CHNS, and synchrotron XAS analyses, it was found that zinc and sulphur added during the tyre manufacturing process were mainly present in the form of ZnS nanoparticles with a crystallite size less than 1 nm in the TC matrix. An overall deoxygenation extent of 31.7 wt% was achieved with original TC catalyst and slow heating rate of 10 °C/min. However, this number was increased to 49.2 wt% with steam activated TC and fast heating rate of 110 °C/min, and adding steam to the reactor at the optimum temperature of 500 °C. More specifically, the introduction of steam and activated TC to the pyrolysis reactor enhanced the transformation of heavy hydrocarbons to light species and value-added chemicals such as LGA and furfural, reaching 34.9 wt% and 11.3 wt% on the mass basis of bio-oil, respectively. The high catalytic performance can be attributed to the large porosity and better exposure of ZnS nanoparticles on the surface of the activated TC, and the influence of steam in shifting the reactions toward more selective production of light hydrocarbons.

Recovery material from a new designed surgical face mask: A complementary approach based on mechanical and thermo-chemical recycling

The usage of disposable face mask to control the spread of COVID-19 disease has led to the alarming generation of a huge amount of plastic waste in a short span of time. On other hand, face masks are made of high-quality thermoplastic polymers that could be recovered and converted into valuable products. The aim of this study is to investigate a complementary approach for the recycling of face mask in lab-scale plants: the mechanical recycling of the filter in polypropylene (PP) and the chemical recycling of the whole face mask. For this purpose, a new designed surgical face mask was chemically and physically characterized. The results shows that the face mask was composed of 92.3 wt% high grade PP (filter), very similar to virgin PP but with a high melt volume index (MVI, 385 cm3/10 min) due to its non-woven manufacturing. The PP from face mask was mixed with recycled virgin PP in order to obtain a MVI suitable for the extrusion process and recycled as filament for 3D printing. This filament was used to print a specimen with a very similar visual quality of that printed with a commercial PP filament. Simultaneously, the whole face mask underwent a pyrolysis process to produce new feedstocks or fuels. Low-cost catalysts derived from coal fly ash (CFA) were employed to enhance the production of light hydrocarbons. In particular, the synthetized acid X zeolite (HX/CFA) improved the yield of light fractions up to 91 wt% (79 wt% for thermal pyrolysis) and the quality of the light oil with the 85% of C6–C10 (55% for thermal pyrolysis). Furthermore, HX/CFA decreased the degradation temperature of PP to 384 °C versus 458 °C of thermal cracking.

Pyro-gas analysis of fixed bed reactor end of life tyres (ELTs) pyrolysis: A comparative study

Pyrolysis of end of life tyres (ELTs) present a promising alternative to their incineration or classical product recovery using mechanical means. It can produce light hydrocarbons (HCs) and other valuable chemicals as part of the pyro-gas stream it generates. In this work, two grades of tyres namely a fresh (virgin) one and a waste disposed ELTs, were used as a feedstock to analyse their pyro-gas constituents. There wasn't much difference in the maximum conversion rate between both tyre grades where the fresh tyres had an estimated 15.17% conversion and the ELTs was 13.45% conversion (both at 800 °C). The difference herein was attributed to release of free radicals prior to subjecting the samples to pyrolysis due to their history. The analysis of the pyro-gas samples showed a large make of light hydrocarbon (HC) products, namely methane (CH4/C1), ethane (C2H6/C2), ethylene (C2H4), propane (C3H8/C3), propylene (C3H6), n-butane (C4H10), butadiene compounds, carbon mono and dioxide (CO,CO2). Light HCs mimciking natural gas were more abundant in the case of ELTs were C1 was estimated as 14.53% at 500 °C and 16.73% at 800 °C. C2 was also estimated higher than the fresh tyres where a 11.78% at 500 °C was noted and 7.67% at 800 °C. It can be recommended that future integration plans in oil and gas ventures, namely refinery and petrochemical complexes, are to start taking responsible measures towards the environment by substituting part of their operations with sustainable feedstock such as ELTs.

Promoting multielectron CO2 reduction using a direct Z-scheme WO3/ZnS photocatalyst

In this study, the WO3/ZnS Z-scheme-heterojunction photocatalyst was evaluated for the photocatalytic reduction of CO2 in the presence of water vapor. The results demonstrated that the quantity of WO3 (5–20 wt%) significantly affects the growth of crystallite size of ZnS, the modulation of the conduction band (CB) potential, and ultimately, the production of light hydrocarbons. The influences of temperature, volumetric flow, and WO3 wt% in the heterostructured photocatalyst were analyzed in a continuous reaction system. The highest production rate of hydrocarbons at the lowest volumetric flow was achieved using a photocatalyst with 5 wt% WO3 with respect to ZnS (W5%Z), with propane (C3H8) and propylene (C3H6) as the main products. The observed effect was rationalized by the synergy between the crystallite size, CB potential, and formation of the heterojunction, which led to enhanced electron transfer on the active surface sites of the W5%Z photocatalyst than on those of either ZnS or WO3. The remarkable performance of W5%Z was attributed to the high production of charge carriers and their fast transfer from the direct Z-scheme photocatalyst surface to the reactants, which promoted the reduction of CO2 molecules into C1-C3 hydrocarbons. The results indicate that the WO3/ZnS system is a good candidate for the chemical transformation of CO2 into valuable products and must be considered for further studies.

Novel hierarchical core-shell BEA@NanoZSM-5 zeolite for improved cracking performance for 1,3,5-triisopropylbenzene and n-hexadecane

To overcome diffusional limitations associated with the catalytic cracking of large hydrocarbons, a novel core-shell hierarchical zeolite has been developed and evaluated. Large, branched hydrocarbons encounter diffusional limitations in micropores of zeolites for cracking reactions, a limitation overcome by improved textural properties of hierarchical zeolites, leading to enhanced cracking activity. This will result in an improvement in deactivation rate, cracking activity, and enhanced product selectivity towards light hydrocarbon products. The impact of chain length involving a long chain paraffin (hexadecane) and a highly branched aromatic (1,3,5-TIPB) was also investigated to study the influence of the presence of the micro-mesopore network in overcoming diffusion limitations. This paper investigates the use of hierarchical core-shell [email protected] in the catalytic cracking of 1,3,5 triisopropylbenzene (1,3,5-TIPB), and n-hexadecane (C16). The novel hierarchical composite was synthesized by preliminary seeding of the core BEA crystals and subsequent growth under hydrothermal conditions leading to the formation of an intergrown and distinctive nanocrystalline ZSM-5 shell zeolite. Evidence of the existence of a hierarchical structure was probed by Ar sorption utilising non-local density functional theory (NLDFT) pore size distribution analysis.

Production of light hydrocarbons at atmospheric pressure from CO2 hydrogenation using CexZr(1-x)O2 iron-based catalysts

Considering that the combination of ZrO2 and CeO2 have superior catalytic properties compared to the individual oxides, the present work investigates the production of light hydrocarbons by carbon dioxide hydrogenation at atmospheric pressure, using iron catalysts constituted of CexZr(1-x)O2 solid solutions (x = 0, 0.25, 0.5, 0.75, and 1). The aim was to determine the effect of the composition of the CexZr(1-x)O2 oxides on the reaction. The materials were characterized by XRF, XRD with Rietveld refinement, textural analysis, Raman spectroscopy, H2-TPR, H2-TPD, and CO2-TPD. The catalysts were tested in the CO2 hydrogenation reaction at 370 °C, under atmospheric pressure, using a molar ratio H2/CO2 = 3, for at least 5 h of time on stream. For the iron-based catalysts constituted of CeO2 and/or ZrO2, the CO2 conversion and selectivity towards the light olefins first increased as the Zr content increased, reaching the highest values with the iron catalyst supported on the material containing 50 % of Ce and 50 % of Zr (molar concentrations on an oxygen-free basis), and then decreased at higher Zr concentrations. The highest CO2 conversion achieved with this catalyst could be attributed to the quantity of basic sites. An appropriate balance between the amounts of adsorbed CO2 and H2 could provide a suitable surface C/H concentration ratio, leading to the best products distribution.

Development of a monolithic carbon xerogel-metal composite for crude oil removal from oil in-saltwater emulsions: Evaluation of reuse cycles

This study aims to evaluate the reuse capacity of carbon xerogels-Ce/Ni composite (XCeNi) during crude oil adsorption from O/W emulsions and subsequent regeneration through the oxidation process using air as an oxidant agent for six cycles. For the six cycles of evaluation, batch adsorption experiments were done at different temperatures and modeled using the solid-equilibrium model (SLE). In contrast, catalytic tests were performed under non-isothermal and isothermal heating. To estimate the change in the sample's surface composition, X-ray photoelectron spectroscopy (XPS) analysis was carried out during each regeneration cycle. According to batch adsorption experiments and SLE fitting, the XCeNi sample presents a high affinity for hydrocarbons and a similar maximum adsorption capacity during six regeneration cycles. Crude oil was also successfully decomposed under non-isothermal heating (100–800 °C), reducing the main decomposition peak from 250 to 150 °C for all the evaluated cycles. Under isothermal heating at 150, 200, and 250 °C, conversions of 100% were obtained for all cycles evaluated. At the first cycle the time required to decompose 100% of adsorbed crude oil at 60 min, whereas, after the 6 cycle, it is achieved at 120 min. The gaseous analysis of the products involved in the oxidation of the crude oil in each cycle was considered, finding an increase in the production of light hydrocarbons and reducing gas emissions such as CO2, NOX, and SOX during all reuses. The activation energy increases from 10.1 to 18.7 kJ mol−1 during the six cycles due to the reduction of the content of Ce3+. The Ce3+ concentration is reduced to 0 after each adsorption cycle. Apparently, the ability of the xerogel to decompose the adsorbed crude during all cycles may be associated with the increase in Ce3+ during the adsorption process, and then during the oxidation treatment is transformed to Ce(OH)22+. Also, the influence of Ni2+ on XCeNi is noted. Through the regeneration, the Ni2+/Ni3+ ratio varies, which shows the continuous redox processes that have taken place in this sample.