Activated Carbon Catalyst Research Articles

Biodiesel Production from Waste Frying Oils by Potassium Methoxide Supported on Activated Carbon Catalysts from Lignocellulosic Biomass

Abstract Various carbon-rich solid catalysts are evaluated for the synthesis of biodiesel from waste frying oil. The study results showed that the use of activated carbon made of corn stalk could increase the biodiesel yield by 7%. The heterogeneous carbon-based catalysts made of lignocellulosic residues could successfully improve the quality of biodiesel properties. The results obtained revealed that the biodiesel properties, including relative density (852–900 kg·m−3) and kinematic viscosity (2.4–3.9 mm2·s−1), are in compliance with the standard limits of ASTM and the European Biodiesel Standard, suggesting that the biodiesel produced would be decent as a diesel fuel that potentially can minimize the serious damage of engine parts, and prolong the engine life.

Waste straw derived Mn-doped carbon/mesoporous silica catalyst for enhanced low-temperature SCR of NO

This work proposed a new strategy for the high value utilization of waste straw, in which a Mn-doped carbon/mesoporous silica composite catalyst was prepared by simultaneous utilization of carbon and silicon source from straw for low-temperature denitration. The results showed that the NO conversion rate reached 93% at 180℃ for the composite catalyst with Si/C mass ratio of 35% (Mn/ACMS (35%)). This was significantly higher than those of the activated carbon catalyst (Mn/AC) and mesoporous silica catalyst (Mn/MS), i.e., 58% and 50%, respectively. The SEM images showed that mesoporous silica nanoparticles were dispersed evenly on the carbon surface to form composite materials. XPS results indicated that Mn/ACMS (35%) catalyst showed higher content of chemically adsorbed oxygen (Oα) and Mn4+ (54.67% and 46.81%) than Mn/AC catalyst (34.38% and 17.49%) and Mn/MS catalyst (32.71% and 30.18%), which was responsible for the improved catalytic activity. Moreover, NH3-TPD results revealed that Mn/ACMS (35%) had high surface acidity of 6.47mmol·g-1, significantly higher than Mn/AC catalyst of 1.51mmol·g-1, which was beneficial for adsorbing NH3. H2-TPR results suggested that Mn/ACMS (35%) catalyst had much higher H2 consumption of 1.32mmol·g-1 than Mn/AC and Mn/MS catalyst, suggesting better redox performance. The results demonstrated that the straw derived Mn-doped carbon/mesoporous silica composite catalyst can be a potential material for low-temperature denitration.

Characterization of Coconut Shell Activated Carbon Catalyst for the Pyrolysis of Waste Sac Bags into Liquid Hydrocarbon Fuels

Aim: The use of synthetic catalysts in pyrolysis of waste plastics into hydrocarbon fuels is the common practice, these synthetic/ commercial catalysts are not readily available in Nigeria. The aim of this research paper is to prepare and characterize and test the catalytic performance of a locally made catalyst for waste plastic to hydrocarbon fuel pyrolysis.
 Study Design: locally made catalyst was prepared from coconut shells, its elemental composition, structural morphology and pore properties investigated using appropriate instruments and methods.
 Place and Duration: The experiments were carried out at the Petroleum Development Laboratory, situated at the Gas Engineering building, University of Port-Harcourt Nigeria. It took about 18 months to complete this study.
 Methodology: Thermal and chemical activation methods were used to prepare the local catalyst from coconut shells. Scanning electron microscopy method was used to investigate the morphology and texture of the coconut shell activated carbon catalyst. Response Surface Method (RSM) in design expert software 12.0 was used to design the experiment, and investigate the effect of operating parameters on the response variable.
 Results: The assessment of coconut shell activated carbon shows it can be used as an alternate to synthetic catalysts. This is because more than 60 % fuel oil was recovered when it was used in the pyrolysis of waste sac bags
 Conclusion: Coconut shell activated carbon is effective in the conversion of waste sac bags high purity hydrocarbon fuels such as aviation kerosene.

One Pot Synthesis of Bio-Ethylene Glycol from Cellulose

In this study, various composite Ni-W2C/active carbon catalysts were synthesized. W2C was prepared by carbothermal hydrogen reduction. The metal loading of W2C in catalyst was 30 wt.%. Carbon was impregnated with metatungstate. It was dried at 120?C for 12 h. Carbon was then carburized in H2 flow, the temperature was increased from 25?C to 450?C, and then to 800?C and stayed for 4 h. The W2C/active carbon was treated with H2SO4 to create more function groups on the surface. Ni-W2C/active carbon was prepared by incipient-wetness impregnation method. After calcination and reduction processes in H2 flow, Ni-W2C/active carbon catalyst was obtained. The reaction of cellulose to ethylene glycol in one step was carried out in a batch reactor under the following condition: 1 g cellulose, 0.3 g catalyst, 100 ml H2O, 4 - 6 MPa H2, 220?C - 280?C, and 400 rpm. The reaction between cellulose and catalyst is a solid-solid reaction; therefore, the contact between these two solid materials is important. Long ball milling time would increase the contact between these two solids. The ball milling time and the functional groups on active carbon play important roles in this reaction. The results demonstrated that one pot synthesis of EG from cellulose is economically and technically feasible.

Bifunctional biomass-based catalyst for biodiesel production via hydrothermal carbonization (HTC) pretreatment – Synthesis, characterization and optimization

The hydrothermal carbonization (HTC) technique is known for its advantages in producing hydrochar from biomass samples with high water content compared to conventional pyrolysis techniques. This study utilized HTC to produce an activated carbon catalyst from renewable mesocarp fiber derived from palm oil processing. The introduction of K2CO3 and Cu(NO3)2 produced a bifunctional catalyst suitable for conversion of used cooking oil to biodiesel. The catalyst possessed a mesoporous structure with a BET surface area of 3909.33 m2/g. An optimum treatment ratio of 4:1 (K2CO3: Cu(NO3)2) provided elevated basic (5.52 mmol/g) and acidic (1.68 mmol/g) concentrations on the catalytic surface, which promoted esterification and transesterification reactions. Maximum yield (96.4%) of biodiesel was obtained at 70 °C for 2 h with 5 wt% catalyst and a 12:1 molar ratio of methanol to oil. The catalyst endured up to 5 reaction cycles while maintaining biodiesel yields of more than 80%. These findings indicated that HTC pretreatment yielded a high-quality bifunctional catalyst for conversion of low-quality used cooking oil for production of biodiesel.

Structure-Performance Evolution of Cobalt-Ammonia Activated Carbon Catalyst for Ethylene Oligomerization

Structure-Performance Evolution of Cobalt-Ammonia Activated Carbon Catalyst for Ethylene Oligomerization

Synergistic effect and mechanism of FeOx and CeOx co-doping on the superior catalytic performance and SO2 tolerance of Mn-Fe-Ce/ACN catalyst in low-temperature NH3-SCR of NOx

Developing alternative NH3-SCR catalysts with high SO2 tolerance is of great significance for NOx emission control at low temperature. For further improving the catalytic performance and SO2 tolerance of nitric acid modified activated carbon (ACN) loaded MnOx catalyst (Mn/ACN), FeOx and CeOx were co-doped by impregnation. FeOx and CeOx co-doped Mn-Fe(0.4)-Ce(0.4)/ACN exhibited improved catalytic activity, N2 selectivity, and SO2 tolerance. The NOx conversion of Mn-Fe(0.4)-Ce(0.4)/ACN was higher than 95% in 100–250 °C and remained around 91% after 32 h reaction under 100 ppm SO2 and 10 vol% H2O at 175 °C. Co-doping FeOx and CeOx greatly enhanced the surface acidity, redox properties, and surface chemisorbed oxygen of Mn-Fe(0.4)-Ce(0.4)/ACN through the interaction among Mnn+, Fen+, and Cen+, resulting in significantly promoted NH3-SCR performance. The stronger surface acidity and promoted catalytic activity effectively inhibited the adsorption of SO2 and the reaction between SO2 and adsorbed NH3, respectively. Meanwhile, the adsorbed SO2 was preferentially induced to react with CeOx, preventing MnOx and FeOx from being sulfated. Finally, the synergistic mechanism of FeOx and CeOx co-doping on better SO2 tolerance for Mn-Fe(0.4)-Ce(0.4)/ACN catalyst was proposed.

Regulation of functional groups on graphene quantum dots directs selective CO2 to CH4 conversion

A catalyst system with dedicated selectivity toward a single hydrocarbon or oxygenate product is essential to enable the industrial application of electrochemical conversion of CO2 to high-value chemicals. Cu is the only known metal catalyst that can convert CO2 to high-order hydrocarbons and oxygenates. However, the Cu-based catalysts suffer from diverse selectivity. Here, we report that the functionalized graphene quantum dots can direct CO2 to CH4 conversion with simultaneous high selectivity and production rate. The electron-donating groups facilitate the yield of CH4 from CO2 electro-reduction while electron-withdrawing groups suppress CO2 electro-reduction. The yield of CH4 on electron-donating group functionalized graphene quantum dots is positively correlated to the electron-donating ability and content of electron-donating group. The graphene quantum dots functionalized by either –OH or –NH2 functional group could achieve Faradaic efficiency of 70.0% for CH4 at −200 mA cm−2 partial current density of CH4. The superior yield of CH4 on electron-donating group- over the electron-withdrawing group-functionalized graphene quantum dots possibly originates from the maintenance of higher charge density of potential active sites (neighboring C or N) and the interaction between the electron-donating group and key intermediates. This work provides insight into the design of active carbon catalysts at the molecular scale for the CO2 electro-reduction.

Composite Carbon Foams as an Alternative to the Conventional Biomass-Derived Activated Carbon in Catalytic Application.

The suitability of a new type of polyurethane-based composite carbon foam for several possible usages is evaluated and reported. A comparison of the properties of the as-prepared carbon foams was performed with widely available commercial biomass-derived activated carbon. Carbon foams were synthesized from polyurethane foams with different graphite contents through one-step activation using CO2. In this work, a carbon catalyst was synthesized with a moderately active surface (SBET = 554 m2/g), a thermal conductivity of 0.09 W/mK, and a minimum metal ion content of 0.2 wt%, which can be recommended for phosgene production. The composite carbon foams exhibited better thermal stability, as there is a very little weight loss at temperatures below 500 °C, and weight loss is slower at temperatures above 500 °C (phosgene synthesis: 550–700 °C). Owing to the good surface and thermal properties and the negligible metallic impurities, composite carbon foam produced from polyurethane foams are the best alternative to the conventional coconut-based activated carbon catalyst used in phosgene gas production.

Role of microwave during microwave-assisted catalytic reforming of guaiacol, syringolbio-oil as model compounds

To better understand the role of microwave and the mechanisms of thermal cracking and catalytic reforming of lignocellulosic bio-oils, this study compares the difference in the reaction characteristics between microwave-assisted and conventional heating of representative bio-oil model compounds. Syringol and guaiacol were selected as bio-oil model compounds. The effects of the heating method on the conversion of the model compound and the yield and composition of products were systematically investigated in the temperature range of 600–700 °C. The results showed that high reaction temperature and microwave-assisted heating favoured the conversion of model compounds, and the conversions of syringol were generally higher than those of guaiacol under the same conditions (temperature, heating method). The heating method was found to greatly influence the yield and composition of products. The bio-oil obtained from conventional thermal cracking of model compounds contained phenolics, aromatic hydrocarbons, aryl alkyl ethers, and oxygen-containing heterocyclic compounds. In contrast, microwave-induced polarisation of poorly stable methoxy groups promotes the formation of phenolics, the concentration of the phenolic in the guaiacol and syringol bio-oil reached 62.5–66.17 area% and 85.18–87.65 area%, respectively, in the temperature range of 600–700 °C. Catalytic reforming of model compounds showed that activated carbon catalyst drastically promoted the phenol formation, particularly under microwave-assisted heating, the phenol concentration reached 93.9–97.97 area% in bio-oil during catalytic reforming of guaiacol. The formation of electron-hole pairs on the active metal sites induced by microwave radiation possibly enhanced the demethoxylation to selectively generate phenol due to the strong electron-donating ability of the methoxyl group. Microwave-assisted catalytic reforming of the model compounds was also beneficial for H2 formation because of the direct dehydrogenation of methyl radicals and the gas-phase reactions. The H2 concentrations of 81.07–82.41 vol.% and 75.2–79.16 vol.% were obtained during microwave-assisted catalytic reforming of guaiacol and syringol, respectively.

Pyrolytic oil with aromatic-rich hydrocarbons via microwave-induced in-situ catalytic co-pyrolysis of empty fruit bunches with a waste truck tire

Microwave-induced in-situ catalytic co-pyrolysis of empty fruit bunch (EFB) with truck tire (TT) using a low-cost heterogeneous catalyst to produce aromatic-rich pyrolytic oil is proposed. In this study, the effect of catalyst type and catalyst-to-feedstock ratio were investigated. Three types of catalysts were used, namely activated carbon (AC), clay (CL) and calcium oxide (CaO), while the catalyst-to-feedstock ratios of 1:5, 2:5, 3:5 were investigated. Although the catalytic co-pyrolysis significantly reduced the yield, high monoaromatic hydrocarbon fraction and BTEX (benzene, toluene, ethylbenzene, xylene) selectivity were observed in the pyrolytic oil. The study showed that the AC-to-feedstock ratio of 2:5 (AC-0.4) contained a high fraction of monoaromatic hydrocarbon (54.32%) with high selectivity of BTEX (30.42%). The elemental analysis also found the AC catalyst produced hydrogen-rich pyrolytic oil with lower undesirable compounds, mainly from oxygenates (ketone group), nitrogen and sulphur compounds. Moreover, the catalytic co-pyrolysis using AC reduces pyrolytic oil's pH value from 4.7 (un-Cat) to pH 5.02 (AC-0.4). However, the AC catalyst had little effect in increasing the higher heating value (HHV) of pyrolytic oil from 42.29 (un-Cat) to 42.47 MJkg−1 (AC-0.4) with a slightly decreased energy recovery from 62.0% (un-Cat) to 56.5% (AC-0.4). The residual gas analysis determined that the dominant gaseous produced from catalytic cracking using AC were CO2 and CH4. A reaction mechanism between the volatiles of EFB and TT is proposed. Overall, the study has successfully demonstrated an approach for producing pyrolytic oil with high monoaromatic fraction and high selectivity of BTEX from in-situ catalytic co-pyrolysis of EFB with TT using low-cost heterogeneous catalyst.

Efficiently Selective Oxidation of H2S to Elemental Sulfur over Covalent Triazine Framework Catalysts.

As a highly toxic and corrosive waste gas in the industry, hydrogen sulfide (H2S) usually originates from the utilization of coal, petroleum, and natural gas. The selective catalytic elimination of H2S shows great significance to ensure the safety of industrial processes and health of human beings. Herein, we report efficiently selective oxidation of H2S to elemental sulfur over covalent triazine framework (CTF-1-x, x = 400, 500, 600, 400-600 °C) catalysts. CTF-1-x samples were prepared from polymerization of 1,4-dicyanobenzene to form polyaryl triazine networks under ion solidothermal conditions in the presence of ZnCl2, which acts as both an initiator and a porogen. The resultant CTF-1-x samples possess abundant micro-mesoporosity, large Brunauer-Emmett-Teller (BET) surface areas, and tunable structural base sites with edge amine and graphitic nitrogen characteristics, which were homogeneously decorated onto their frameworks. As a result, CTF-1-x samples act as efficient and long-lived catalysts in selective oxidation of H2S to sulfur under ambient conditions (100% H2S conversion, 100% sulfur selectivity at 180 °C, 12 000 mL/(g·h)), and their activities were superior to those of commercial Fe2O3 and g-C3N4 desulfurization catalysts. Abundant nitrogen structural base sites of CTF-1-x effectively activate the reactants, and abundant micro-mesoporosity facilitates mass transfer in and out of CTF-1-x. The improved design of the nitrogen-doped carbon material for H2S activation and conversion could enhance the development of more active and robust nitrogen-doped carbon catalysts.

Photocatalytic oxidation and catalytic wet air oxidation of real pharmaceutical wastewater in the presence of Fe and LaFeO3 doped activated carbon catalysts

Real pharmaceutical wastewater was treated by photocatalytic oxidation and catalytic wet air oxidation (CWAO) processes. The catalytic performance of Fe/AC and LaFeO3/AC (AC: Commercial activated carbon) was compared in the advanced oxidation processes. The influences of the reaction parameters were determined by using Box–Behnken design. Fe/AC catalyst was more effective in both of the photocatalytic oxidation and catalytic wet air oxidation processes. In the photocatalytic oxidation process, 72.7% COD removal was achieved at pH = 4.5, 2.0 g/L, and [H2O2]o = 0.32 mM. Under the optimum conditions of the CWAO, which were determined as 3 g/L of catalyst loading, pH = 3, and 50℃, 83.1% COD removal efficiency was obtained. CWAO method was determined as more suitable since a higher COD removal efficiency was achieved in a shorter reaction time. The toxicity in terms of L. sativum growth inhibition was evaluated as 4.82% after the CWAO treatment. A two-step first-order reaction kinetics provided the best fit of the CWAO experimental data. The activation energies of the fast and the slow steps were 25,661.16 and 28,327.46 J/mole, respectively.

Coke formation on activated carbon during catalytic upgrading of coal pyrolysis volatiles

The content of heavy pitch in tar generated from coal pyrolysis is high. To improve the quality of tar, catalysts are applied for adjusting the reaction of volatiles during coal pyrolysis. However, catalysts are easy to deactivate due to coke deposition. In this study, coke amount on activated carbon catalysts during catalytic upgrading of coal pyrolysis volatiles was investigated in the downer-bed reactor. The process of coke formation was studied at different feed time (30, 60 and 100 min) of coal. Results show that a great amount of coke is generated on the activated carbons. With the increase of feed time, the amount of coke on activated carbon increases, while the rate of coke formation decreases, thus decreasing the coke yield based on dry coal. The specific surface area and catalytic cracking activity of the activated carbon decrease with the increase of coke amount. Hence, the yields of tar and pitch increase with the increase of feed time. The relative content of oxygen-containing compounds in the tar increases with the increase of feed time, which indicates that the cleavage of weak chemical bond C–O is suppressed. That may result in a decrease in the rate of coke formation.

Mechanism of improving the stability of activated carbon catalyst by trace H2S impurities in natural gas for hydrogen production from methane decomposition

Direct methane decomposition for hydrogen production is considered a clean technology with limited CO2 emission. However, catalysts usually suffer from deactivation due to carbon deposition. This study reported a method of improving the catalyst stability by using a trace amount of H2S which naturally exists in natural gas, and the action mechanism of H2S was discussed. Coconut shell activated carbon (AC) was used as the catalyst, the pure methane was mixed with 100, 200, and 300 ppm H2S and decomposed at high temperature. Results show that adding different concentrations of H2S can increase the methane conversion and delay the deactivation time of the AC catalyst. Through scanning electron microscopy characterization and Brunauer-Emmet-Teller analysis, it was found that the positive effect of H2S is achieved by changing the carbon deposition morphology which in turn changes the AC pore width distribution and the specific surface area. Under the action of H2S, AC has a relatively large number of micropores during the reaction, promoting the adsorption of methane molecules on AC. First-principles calculations show that H2S changes the reaction pathway of methane dehydrogenation and promotes methane decomposition.

Phosphorus-doped activated carbon catalyst for n-hexane dehydroaromatization reaction

Phosphorus-doped activated carbon (P@AC), prepared by wet impregnation method, can serve as efficient metal-free catalyst for the dehydroaromatization of n-hexane to benzene under mild conditions. The effect of phosphorus amount and phosphorus sources including phenylphosphonic acid (PPOA), phosphorus acid (H3PO4), triphenylphosphine (TPP), and tributylphosphine (TBP) on catalytic performance of P@AC were investigated. Combining with characterization analysis, functional groups containing -P(O)(OH) on the carbon surface are believed to be the active sites for dehydroaromatization catalysis.

Nitrogen-doped carbon spheres-decorated graphite felt as a high-performance electrode for Fe based redox flow batteries

In this paper, the performance of Fe-based redox flow batteries (IRFBs) was dramatically improved by coating N-doped carbon spheres (NDCS) on the graphite felt electrodes. NDCS was synthesized by the single-step hydrothermal method using dextrose and ammonia as a precursor and coated over graphite felt electrodes by electrostatic spraying. The weight of NDCS required for the modification of the electrode to achieve the effective performance of the battery was studied using electrochemical techniques. Cyclic voltammetry (CV) and potentiodynamic polarization study was used to evaluate the kinetic reversibility and linear polarization resistance offered by the electrode towards electrolyte. The characterizing features of the NDCS, untreated graphite felt (UGF) electrode and optimized modified graphite felt (MGF) electrode were analyzed using SEM, EDAX, XRD, and Raman spectroscopy. The charge-discharge studies were performed for the 132 cm2 IRFB using a 2 mg/cm2 MGF electrode as a positive electrode by varying the current densities from 20 to 60 mA/cm2. The cell resulted in an average coulombic efficiency (CE) of 93%, voltaic efficiency (VE) of 72%, and energy efficiency (EE) of 68% for 15 cycles at the current density of 30 mA/cm2. The improvement in the performance of the IRFB is due to the presence of electrochemically active nitrogen-bearing carbon catalysts. In this paper, the pioneering effort has been made to improve the efficiency of the IRFB with an active area of 132 cm2 using glycine as the ligand.

Potential of ammonium chloride-activated carbon for decomposition of penicillin G by catalytic ozonation process (COP)

Pharmaceutical compounds that enter the aqueous solution are classified as emerging pollutants. The aim of this study was to use a single adsorption process (adsorption/AC), single ozonation process (SOP), and catalytic ozonation processes (COPs) with activated carbon obtained from Calligonum comosum as novel advanced oxidation processes to decomposition and mineralization of penicillin G from pollutant waters. The influence of important parameters including solution pH (2, 4, 6, 8, and 10), contact time (5, 10, 15, 20, 25, 30, 35, and 40 min), catalyst dosage (0.025–0.1 g/L), and initial PG concentration (25–100 mg/L) was examined on the efficiency of COP in degradation and mineralization of penicillin G in aqueous solution. The BET results indicated that the surface area of the activated carbon catalyst was1473 m2/g. The efficiency of adsorption/AC, SOP, and COP/AC in penicillin G decomposition at a pH of 10 was 11.17%, 33.6%, and 85%, respectively. The efficiency of COP/AC increased to 100% with the increase in catalyst concentration up to 75 mg/L. The highest synergistic rate of the catalyst at this concentration and a pH of 10 was 46.6%. A maximum reduction of 100% of PG was achieved at a pH of 10, a concentration of 50 mg/L in 40 min. The results also indicated that the mineralization rate in COP/AC was 52%. Also, the results showed that the catalytic ozonation process can be used as an effective method for the oxidation of penicillin G from contaminated water.

Exploring the relationship between the physical properties of activated carbon catalysts and their efficiency in catalyzing hydrogen iodide decomposition to produce hydrogen

Using simple and efficient methods to synthesize biological activated carbon catalysts (ACCs) with the decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle as a typical reaction is urgently needed for the commercialization of hydrogen energy production and development. In this study, a series of ACCs with different specific surface areas (SSAs) and pore structures are prepared by comparing and controlling the changes in carbonization and activation methods of activated carbon (AC) preparation process. Hierarchical porous AC with larger SSA has higher HI decomposition efficiency. The representative samples H240H1h and H240C4h are hierarchical porous ACCs with 48.96% and 46.88% micropores, respectively, and have the highest catalytic activity in the entire series. The nitrogen adsorption and desorption curve is combined with pore size distribution data and analyzed using the capillary aggregation (Kelvin) and monolayer adsorption (Langmuir) theories. And ACC pore grading coefficient—which can improve data visualization—is introduced.

Search for the Microwave Nonthermal Effect in Microwave Chemistry: Synthesis of the Heptyl Butanoate Ester with Microwave Selective Heating of a Sulfonated Activated Carbon Catalyst

The heptyl butanoate ester was synthesized from butanoic acid and heptanol in a heterogeneous medium in the presence of sulfonated activated carbon (AC-SO3H) catalyst particles subjected to microwave irradiation, which led to higher conversion yields (greater product yields) than conventional heating with an oil bath. The advantage of the microwaves appeared only when the moisture content in the butanoic acid batch(es) was high, suggesting that, unlike conventional heating, the reverse reaction caused by the moisture content and/or by the byproduct water was suppressed by the microwaves. This contrasted with the results that were found when carrying out the reaction in a homogeneous medium in the presence of the 2,4,6-trimethylpyridinium-p-toluene sulfonate (TMP-PTS) catalyst, as product yields were not improved by microwave heating relative to conventional heating. The removal of moisture/water content in the reaction solution was more pronounced when the reactor was cooled, as the reaction yields were enhanced via selective heating of the heterogeneous catalyst. A coupled electromagnetic field/heat transfer analysis gave credence to the selective heating of the AC-SO3H catalyst, which was further enhanced by cooling the reactor. It was deduced that unforeseen impurities and local high-temperature fields generated on the surface of small fine catalyst particles may have had an effect on the microwave chemistry such that the associated phenomena could be mistaken as originating from a nonthermal effect of the microwaves. Accordingly, it is highly recommended that impurities and selective heating be taken into consideration when examining and concluding the occurrence of a microwave nonthermal effect.