Amount Of Coke Research Articles

Coque de petróleo como controlador de filtrado en fluidos de perforación base aceite

La gran cantidad de coque de petróleo producido en Venezuela, conllevó a su uso como controlador de filtrado en fluidos base aceite. Inicialmente el coque se sometió a un proceso de extracción de aceite mediante el método Soxhlet y extracción de azufre mediante microondas. Seguidamente se le realizó una Espectroscopia de Infrarrojo (IR) y se comparó con otra espectroscopia del coque de petróleo natural, donde quedó evidenciado la efectividad del proceso aplicado. Se formularon cuatro (4) fluidos de perforación (12 lpg) con coque como controlador de filtrado, variando su concentración en 6, 8, 10 y 12 lb/bl y después de un envejecimiento dinámico (300°F, 100 lpcm) se estudiaron las propiedades físicas de viscosidad plástica, punto cedente, gel 10 s, gel 10 min y filtrado, obteniéndose rango de valores de 25,3-26,3; 5,7-6,3; 4-5; 7-10 y 10,3-10,9 respectivamente. Un estudio estadístico de parcelas divididas demostró que existieron diferencias estadísticas significativas entre las propiedades físicas de los fluidos formulados y las propiedades físicas de un fluido patrón con lignito como controlador de filtrado. Se concluyó que a pesar de las diferencias estadísticas presentadas es posible el uso de coque de petróleo como controlador de filtrado para las condiciones en estudio.

Effect of Next-Nearest-Neighbor Aluminum Atoms in the HZSM-5 Framework Synthesized with Various Aluminum Sources on Liquefied Petroleum Gas Transformation to Light Olefins

HZSM-5 catalysts with various aluminum distributions in their frameworks and different Si/Algel ratios were synthesized to investigate the product distribution in liquefied petroleum gas cracking. The characterization of synthesized zeolites was performed by X-ray diffraction (XRD), Brunauer, Emmett, and Teller (BET) method, (scanning electron microscopy) SEM, NH3-TPD, X-ray fluorescence (XRF), and direct reflectance (DR) UV–visible, and 27Al MAS NMR analyses. The maximum proportion of 0NNN aluminum atoms (90.6–92.6%) were found in HZSM-5 synthesized with aluminum nitrate. The higher 0NNN aluminum atoms in the zeolite framework and lower content of aluminum at channel intersections enhanced the olefin yield and decreased the C5+ yield. The amount of coke increased with increase of the 1NNN Al atoms. The optimum olefin yields for HZSM-5 synthesized with aluminum nitrate, aluminum chloride and aluminum hydroxide were found to be 47.22% with Si/Algel 50, 45.47% with Si/Algel 30, and 44.32% with Si/Algel 30, ...

INFLUENCE OF THE METHOD OF NATURAL GAS SUPPLYING ON GAS DYNAMICS AND HEAT TRANSFER IN AIR TUYERE OF BLAST FURNACE

The use of natural gas reduces the amount of coke to produce pig iron. The flow of hot blast pushes natural gas to the surface of blowing channel in the conventional tuyere. Natural gas is poorly mixed with natural gas. This causes incomplete natural gas combustion and pyrolysis. Therefore, the problem of the completeness of combustion of natural gas is relevant. One way to improve the mixing of natural gas and hot blast is the gas pipe in the blow channel. However, dynamics and change of the thermal state of the tuyere are understudied for this option. The possibility of ignition of natural gas inside tuyeres must also be taken into account. The authors have investigated the inf­luence of the method of natural gas supplying on gas dynamics and heat transfer in air tuyere of a blast furnace with the help of modeling in ANSYS Fluent 15.0.7. Simplifying assumptions were adopted. Only fluid inside the blowing channel is considered as the modeling zone, and the processes of heat transfer to the water of cooling system are considered in the extended boundary conditions. A simplified diagram of the computational domain was created in DesignModeler and a computational mesh – in AnsysMeshing. The boundary conditions were set for blowing, natural gas, and also for the border of the fluid with copper walls. The calculations were carried out for half of the tuyere. It is shown that under the given conditions of flow of air and natural gas, combustion inside tuyere with extended to mid-channel gas blowing nozzle does not occur, and natural gas is mixed with the hot air. Improving the mixing of natural gas and hot air, one side, reduces heat flow at the exit of the blowing channel and the average temperature of the gas mixture, on the other side, creates conditions for complete combustion of natural gas outside the tuyere.

Influence of Fe based ZSM-5 catalysts on the vapor intermediates from the pyrolysis of brominated acrylonitrile-butadiene-styrene copolymer (Br-ABS)

The catalytic upgrading of the vapor intermediates from the pyrolysis of brominated acrylonitrile-butadiene-styrene (Br-ABS) was investigated over the Fe/ZSM-5 catalysts in a two-stage fixed bed reactor. Results showed that HZSM-5 and Fe/ZSM-5 catalysts exhibited high catalytic cracking activities, resulting in the increased yield of oil from 62.8 wt% to 64.3 wt% and 66.7 wt%, respectively. When the higher amounts of Fe/ZSM-5 catalysts were applied, the oil yield decreased to 59–61.6 wt%, whereas high amounts of coke were deposited on the catalysts. On the other hand, the higher percentages of the single ring and 2 ring aromatic compounds in the oils was obtained by the Fe/ZSM-5 catalysts, compared to the thermal pyrolysis and the catalytic upgrading by the parent HZSM-5 catalyst. The Fe/ZSM-5 catalysts significantly promoted the formation of styrene monomer and dimer derivatives. It could be proposed that the Fe based materials was in favor of the depolymerization of the polymer matrix, providing the styrene sources for the secondary oligomerization over the parent HZSM-5 catalyst. In addition, the Fe/ZSM-5 catalyst exhibited effective debromination performance, by means of cracking the organobromine compounds and capturing the inorganic bromine in the catalyst. The possible catalytic cracking mechanism over the Fe/ZSM-5 catalyst was discussed.

Renewable hydrogen production by ethylene glycol steam reforming over Al2O3 supported Ni-Pt bimetallic nano-catalysts

Abstract The steam reforming of ethylene glycol, a simple model compound for biomass-derived liquids, is considered to be an environmentally green process for producing renewable hydrogen. Both Pt and Ni species are known for their catalytic activity under steam reforming reaction conditions. In this investigation, alumina supported Ni-Pt bimetallic catalysts (X wt% Ni-Y wt% Pt/Al2O3 named XNi-YPt) were employed for steam reforming of ethylene glycol. The prepared catalysts were characterized by XRD, BET, H2-TPR, H₂-Chemisorption, and TEM. It was observed that Ni/Pt ratio strongly affected the redox behavior, BET surface area, and particle size of the samples that in turn affected their catalytic performance. The optimum catalyst sample was 3.75Ni-1.25 Pt which resulted in the highest ethylene glycol conversion (60%), highest H2 selectivity (45%) and yield (27%), and a minimum of 20 h of stability due to the lowest amount of coke formed the catalyst surface. The overall order of the catalytic performance of the samples was as follows: 3.75Ni-1.25 Pt > 2.5Ni-2.5 Pt > 1.25Ni-3.75 Pt > 0Ni-5Pt > 5Ni-0Pt. A kinetic model for the steam reforming of ethylene glycol in a packed bed reactor containing the 3.75Ni-1.25 Pt catalyst was employed indicating a good agreement between experimental and predicted H2 selectivity and yield. Intrinsic reaction rate data in the absence of the heat and mass transfer limitations were obtained in parametric studies (Temperature range of 823–893 K, ethylene glycol mole fraction range of 0.056–0.116 and bed density of 18–26 kg m−3). Higher temperature and bed density and lower ethylene glycol mole fraction enhanced the reactivity. The maximum ethylene glycol conversion (70%), H2 yield (36.5%) and H2 selectivity (52%) was observed for conditions of 893 K, bed density of 24 kg m−3 and ethylene glycol mole fraction of 0.056.

Dehydrogenation of Propane to Propylene with Highly Stable Catalysts of Pt-Sn Supported Over Mesoporous Silica KIT-6

Abstract During several reactions, similar to dehydrogenation of propane to propylene, coke is one of the main reasons for the catalyst deactivation. The coke formation and further deactivation of the catalyst are strongly dependent to the active site in the catalyst and/or the properties of the support. KIT-6 with interconnected porous and high surface area can handle with the coke formation, and can disperse easily the deposited Pt nanoparticles. In this sense, a series of Pt-Sn/KIT-6 catalysts were synthesized with distinct Sn loadings and used in the dehydrogenation of propane. The performance of these catalysts during reaction varied with the Sn loading. The specific activities for propylene formation obtained with the catalysts were comparable to the best result reported in the literature. The nanoparticles present in the catalyst through pretreatment and reaction condition was the Pt-Sn alloy (1:1 atomic ratio), and that alloy is suggested to be the active phase. This Pt-Sn alloy was stable during the entire reaction time, that even in two catalysts containing a considerable amount of coke, deactivation was not observed. Also, the support (KIT-6) with high connectivity helped to avoid deactivation by coke.

Catalytic activities of nickel, dolomite, and olivine for tar removal and H2-enriched gas production in biomass gasification process

Tar content in gasification products is a serious problem for fuel gas utilization in downstream applications. Catalytic steam reforming of tar to syngas is a promising way for the removal of tar from the gas products. Nickel-based catalysts, dolomite, and olivine have been widely investigated for tar cracking and reforming by various researchers. This paper presents a review of biomass gasification, tar composition, and its elimination process by using the above three catalysts. This paper summarizes the knowledge in the published literature associated with tar elimination during the biomass gasification including discussion on the effects of different support, promoter on the catalytic performance. The aim of this paper is to collect information on the performance of above catalysts to make them accessible to readers within one paper. Comparative studies on these catalysts carried out by some researchers have also been presented here which show that the nickel-based catalyst is much more active than dolomite and olivine, but they are more expensive and can be also deactivated. Compared to olivine, the dolomite shows better catalytic performance with much higher gas yield and H2. Calcination of these catalysts improves the catalytic activities but the amount of coke deposited on the surface of the dolomite is reported higher than that of the olivine, which may be resulted from the different Fe amount of the catalyst.

The Effect of Sn Content in a Pt/KIT-6 Catalyst Over its Performance in the Dehydrogenation of Propane

Abstract Propylene is one of the most important commodity chemicals. Its future demand is expected to exceed its production. Alternative routes to obtain this product need to be implemented. Dehydrogenation of propane assisted with catalyst is a promising route to meet demands. The Pt and Cr supported catalysts are amongst the most effective possibilities. However, Pt catalysts are preferred over Cr due to the toxic nature of Cr species. Despite the high performance of the Pt catalysts, they deactivate during reaction, mainly due to coke deposits blocking the active site and/or pores. This effect can be reduced with a support having high connectivity and surface area, like KIT-6. In this work the mesoporous silica KIT-6 was employed as support in a series of Pt-Sn catalysts. The influence of adding or increasing the weight % of Sn to Pt catalyst was studied. There were species of SnO2 and metallic Pt in the fresh catalysts. After reaction, it was found that in the catalysts with the lowest wt % of Sn (0.5), there were metallic Pt and a Pt-Sn alloy. In the rest of the used catalysts (containing 1.0, 1.5 and 2.0 wt % of Sn) the only detected specie was the Pt-Sn alloy. In the two most active catalysts (having 0.5 and 1.5 wt % of Sn), it was observed a difference of three times the quantity of coke deposited on the surface. The catalysts containing the highest coke deposits maintained its activity due to the high connectivity of the support.

The role of Zr in NiZrAl oxides catalyst and the evaluation on steam reforming of glycerol for hydrogen product

The NiZrAl mixed metal oxides catalysts with varied Zr/Al ratio were derived from the layered double hydroxides (LDH) through the thermal decomposition. The different techniques such as TG, XRD, N2 adsorption/desorption, XPS, TPR, H2 chemisorption, SEM and TEM etc. were applied to study the thermal decomposition behaviors of the corresponding LDH, crystalline phases changes before and after reaction, the porous structure, chemical state of surface element, reducibility, properties of active phase metallic Ni and the morphology. The results showed that the LDH structure could be kept during the experimental range from 0.1 to 1.0, although high Zr/Al ratio made the structure feature weaken. The porous structure of the calcined catalysts exhibited an significant change when Zr/Al ratio reached 0.5. Both Ni dispersion and surface increased linearly with the increased Zr/Al, however, more amount of surface Ni was reduced and less amount of coke was formed over the sample NiZr0.5Al. It consequently gave the best conversion to gaseous products and the highest selectivity of hydrogen by promoting the water gas shift reaction and suppressing the CO methanation reaction.

Coking Tendency of 25Cr-35Ni Alloys: Influence of Temperature, Sulfur Addition, and Cyclic Aging

25Cr-35Ni base alloys are the most frequently used materials for steam cracking reactors. The influence of cyclic aging, reactor temperature, and adding sulfur containing compounds before or during cracking on the rate of coke deposition on a classical 25Cr-35Ni alloy is evaluated using a jet stirred reactor equipped with an electrobalance. As expected, the initial and asymptotic coking rate increased with increasing reactor temperature. Scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX) analysis indicated that more Ni and Fe is present on the surface at higher cracking temperatures. Presulfidation led to increased coke deposition and decreased CO yields compared to the reference. When a sulfur containing compound was added continuously, coke deposition increased significantly but carbon oxide formation was suppressed. A pronounced amount of coke was measured in the reactor, followed by suppressed generated amounts of carbon oxides downstream. When combined with the continuous add...

Synthesis of SAPO-34 catalysts via sonochemically prepared method and its catalytic performance in methanol conversion to light olefins

Methanol-to-olefin (MTO) reaction was investigated over sonochemically (SAPO-34-U40, SAPO-34-U70, SAPO-34-U100) and hydrothermally (SAPO-34-HT) prepared nanocatalysts. The catalytic performance of prepared samples was investigated over all samples at 450 °C and over SAPO-34-U40 at 350–450 °C temperature range. The higher yield ~ 97 wt% (31.4 wt% C2=, 49.4 wt% C3= and 16.1 wt% sumC4=) of light olefins was obtained at 375 °C on SAPO-34-U40. Physico-chemical properties of catalysts were characterized by XRD, SEM, BET, ICP techniques. XRD analysis showed suitable crystalline structure and SEM images confirmed perfect crystallinity of sonochemically prepared samples. BET analysis indicated remarkable surface area of SAPO-34-U40. The amount of carbon deposits and character of coke was determined by TPO analysis. The higher amount of coke was determined over SAPO-34-HT in comparison to another’s at 450 °C. The character of coke deposited over SAPO-34-U40 was similar for 375–425 °C temperatures.

Ceria-promoted Ni@Al2O3 core-shell catalyst for steam reforming of acetic acid with enhanced activity and coke resistance

A series of Ni@Al2O3 core-shell catalysts with ceria added to the surface of Ni nanoparticles or inside the alumina shell were prepared, and the effect of ceria addition on the performance of the catalyst in the steam reforming of acetic acid was investigated. The prepared catalysts were characterized by BET, XRD, HRTEM, H2-TPR and DTG. The addition of ceria to the surface of nickel nanoparticles greatly enhanced the activity of catalyst owing to the presence of the mobile oxygen, which migrated from the ceria lattice. Among the prepared catalysts, the Ni@Al10Ce catalyst showed the highest activity with a conversion of acetic acid up to 97.0% even at a low temperature (650 °C). The molar ratio of CO2/CO was also improved due to the oxidation of CO by the mobile oxygen into CO2. The coke formation on the core-shell catalysts was significantly inhibited by the addition of ceria to the surface of nickel nanoparticles due to the oxidation of carbon species by the mobile oxygen in the ceria lattice. However, the Ni@Al10Ce-a catalyst with ceria added to the alumina shell showed a low activity and the formation of a large amount of coke. It is suggested that only the ceria in close to the Ni surface has the promoting effect on the catalytic performance of the Ni@Al2O3 catalyst in the steam reforming of acetic acid.

Relationship between Coking Behavior in Hydrocarbon Fuel Pyrolysis and Surface Roughness

The pyrolysis of hydrocarbon fuels can give rise to the formation of coke on metal substrate surfaces. Until now, there are few research reports about how the nature of these surfaces affects the formation of coke, especially the effect of surface roughness. A series of samples of different surface roughnesses was obtained by mechanical polishing, and the coking property with changed surface roughness was evaluated by cyclohexane cracking under 1 atm at 730–810 °C. The coke obtained was then analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and temperature-programmed oxidation (TPO). The results showed that reducing the surface roughness can effectively decrease the amount of coke in different ranges of cracking temperatures and cracking times, especially in high-temperature ranges (above 770 °C). The polishing process reduced the metal catalytic activity of coking to inhibit coke formation without changing the mechanism of cyclohexane cracking. Su...

Dehydrogenation of n-Butane to Butenes and 1,3-Butadiene over PtAg/Al<sub>2</sub>O<sub>3</sub> Catalysts in the Presence of H<sub>2</sub>

The Al2O3-supported PtAg catalysts were prepared and evaluated for the dehydrogenation of n-butane at 550°C in the presence of H2. The PtAg/Al2O3 catalyst prepared by an impregnation method using the Cl- removing Pt/Al2O3 and AgNO3 showed a higher activity and selectivity to butenes and 1,3-butadiene compared to the Pt/Al2O3 catalyst, but a large amount of coke (about 30 wt% versus the catalyst weight) was formed during the dehydrogenation. The free Ag metal on the prepared catalyst dramatically promoted the coke formation, because the dehydrogenation of 1-butene over the Ag/Al2O3 catalyst produced a large amount of coke. The Cl- addition to the Cl- free Pt/Al2O3 catalyst decreased the coke formation by the reaction of the free Ag particles and Cl to form AgCl which was inactive for the coke formation. The highest initial conversion (50.3%) was obtained with the selectivity to butenes and 1,3-butadiene (butenes = 80.2% and 1,3-butadiene = 5.9%) when the PtAg/Al2O3 catalyst modified with Cl- was used.

Effect of CeO<SUB align="right">2 morphology on performance of NiO/CeO<SUB align="right">2 catalyst in combined steam and CO<SUB align="right">2 reforming of CH<SUB align="right">4

Nanorods (NR), nanoparticles (NP), and nanocubes (NC) of ceria were prepared by hydrothermal method and used as supports for NiO catalysts for bireforming of CH4 in this investigation. Effects of NiO contents (5-20 wt.%), quantities of reagents, and calcination duration (1-3 h) at 800°C were investigated. Several techniques, including N2 physisorption measurements, X-ray powder diffraction, hydrogen temperature-programmed reduction, scanning electron microscope (SEM), and transmission electron microscopy (TEM) were used to investigate the physico-chemical properties of catalysts. The catalytic performance of the Ni/CeO2 catalysts in combined steam and CO2 reforming of CH4 (bi-reforming) was assessed in the temperature range of 550-800°C. The results revealed that a better duration for calcination is 2 h. After reduction at 800°C for 2 h, catalyst 10 wt% NiO/CeO2-NR was more active and exhibited much higher activity at lower reaction temperature range than others. The high surface area and better reducibility were responsible for improving performance of this catalyst. Moreover, strong metal support interaction (SMSI) was attributed to the better anti-sintering ability leading to a higher stability with time on stream (TOS) of this catalyst. Besides, this improvement of anti-carbon deposition for 10 wt% NiO/CeO2-NR catalyst also owned to CeO2 nature of oxygen capacity. At reaction temperature of 700°C, its catalytic performance could remain over 30 h until deactivation initiated. Coke amount formed after 30 h of TOS was found to be as low as 1.84 mgC/gcat by using temperature programmed oxidation technique.

Conversion of methanol to light olefins over nanosized [Fe,Al]ZSM-5 zeolites: Influence of Fe incorporated into the framework on the acidity and catalytic performance

Nanosized ZSM-5 zeolites (NZ5(x) series) with different SiO2/Al2O3 ratios as well as samples isomorphously substituted by Fe ([Fe,Al]NZ5(x) series) with various SiO2/(Al2O3+Fe2O3) ratios were synthesized by an in situ seed-induced hydrothermal method. The structure, morphology, textural and acidity of catalysts were characterized via XRD, SEM, 27Al and 29Si MAS NMR, UV–vis spectroscopy, XPS, N2 physical adsorption, NH3-TPD and Py-IR. The catalytic performance was assessed by methanol-to-olefins (MTO) reaction and the effect of the textural and acidity of the two series of samples on the catalytic performance was also investigated. The results showed that the catalyst acidity is closely related to the product selectivity in the MTO reaction. Compared with NZ5(x), the [Fe,Al]NZ5(x) samples with smaller particle size, weaker acid strength and fewer Brønsted acid sites displayed a higher selectivity towards C2∼C4 light olefins. Highest selectivity of 82.7% for C2∼C4 light olefins and lowest coke amount of 0.71% after reaction for 50 h was obtained for the [Fe,Al]NZ5(300) catalyst due to the appropriate acidity and improved diffusion properties.

Honeycomb-shaped PtSnNa/γ-Al2O3/cordierite monolithic catalyst with improved stability and selectivity for propane dehydrogenation

A novel honeycomb-shaped PtSnNa/γ-Al2O3/cordierite monolithic catalyst (Pt 0.5%, Sn 0.9%, Na 1.0%, relative to Al2O3 weight) was developed and its catalytic performances in propane dehydrogenation were tested and compared with the classical granule catalyst with same Pt, Sn and Na contents under the conditions of 0.1MPa, 590°C,C3H8/H2 at 3/1 (molar ratio) and gas hourly space velocity (GHSV) at 155h−1. Interestingly, despite the generated coke amount and exposed Pt fraction, the honey comb-shaped structure of monolithic catalyst exerted important influences on its catalytic activities and led to the advanced catalytic performances over the granule catalyst.

Hydrogen production by crude glycerol steam reforming over Ni–La–Ti mixed oxide catalysts

The production of H2-rich gaseous mixtures from steam reforming of crude glycerol was investigated on ternary Ni–La–Ti catalysts. Ni–La–Ti mixed oxides containing 15 wt% of Ni and a La/Ti atomic ratio of 1 were prepared by a coprecipitation method and characterized by a variety of physical and spectroscopic techniques. Samples were calcined in air at 700 °C or 850 °C for 2 h. Ni–La–Ti samples calcined at 700 °C (NiLaTi700) showed a well-defined NiO phase and an amorphous La–Ti mixed oxide, while those calcined at 850 °C (NiLaTi850), exhibited two well defined phases of NiO and LaTiO3 perovskite, respectively. NiO was completely reduced to metallic Ni on both solids under pure H2 at 650 °C and the resulting Ni0 phase remained as a separate phase under the steam reforming conditions. Standard catalytic tests for the steam reforming of glycerol were performed at 500 °C or 650 °C by feeding the fixed-bed tubular reactor with a crude glycerol:water solution containing 30 wt% glycerol. The best results were achieved on NiLaTi700 at 650 °C, obtaining H2 yields and H2/CO2 molar ratios close to the theoretical values predicted by the steam reforming reaction stoichiometry. A slight activity decay was observed on NiLaTi700 with the progress of the reaction, probably reflecting the formation of small amounts of coke.

Controlled regeneration of ZSM-5 catalysts in the combined oxygen and steam atmosphere used for catalytic pyrolysis of biomass-derivates

Catalyst deactivation by coke deposition was the main barrier in the catalytic pyrolysis of biomass for hydrocarbons, thus deactivated catalysts should be regenerated timely. In this study, several measures were applied in the regeneration process to obtain higher yield of hydrocarbons in the catalytic conversion of biomass-derivates. The effect of oxygen concentration in the regeneration atmosphere on catalytic performance was firstly investigated, and then steam was introduced on the basis of the optimal oxygen concentration to further decrease the internal temperature of catalyst particle. Finally the deactivated catalysts were partially regenerated by retaining some coke. The results showed that 15% was the optimal oxygen concentration, at which the catalysts still showed steady production of olefins and aromatics after 30 cycles of catalysis-regeneration. When 15% oxygen and 5% steam was combined in the regeneration atmosphere, the temperature of catalyst bed was reduced efficiently. The stable yield of hydrocarbons by combined regeneration method was boosted by 31.3% compared with pure 15% oxygen. At retaining coke amount of 2.18%, yield of hydrocarbons was promoted by 27.4% compared with completely regenerated. With the combined oxygen/steam atmosphere and controlled regeneration, the temperature of catalyst particles was well regulated and stable catalysis-regeneration process to produce hydrocarbons via thermochemical utilization of biomass can be realized.

A Straightforward Descriptor for the Deactivation of Zeolite Catalyst H-ZSM-5

ZSM-5 is a widely used zeolite catalyst and is employed industrially for the methanol to gasoline (MTG) process. Even so, deactivation of ZSM-5 by coke formation constitutes a major technical and also fundamental challenge. We investigate the deactivation of a range of ZSM-5 catalysts through catalytic testing, physicochemical characterization, and powder X-ray diffraction (XRD). It is demonstrated that the unit cell changes upon deactivation. Periodic density functional theory is used to show that the change is induced by certain methyl substituted benzenes in the channel intersection in ZSM-5. This finding is corroborated by Rietveld refinement of XRD data obtained for deactivated catalysts. We are able to establish a direct correlation between the difference in the length of the a- and b-unit cell vectors and the total amount of coke, the remaining acidity, and the remaining surface area of the catalysts. This a- minus b-parameter is a straightforward descriptor that carries the essential information r...