Reactor Feed Research Articles

Kinetic parameter estimation for methanol dehydration to dimethyl ether over sulfonic and polymeric acid catalysts

AbstractBACKGROUNDThe methanol dehydration to dimethyl ether (DME) has received considerable attention in the literature, because of its potential use as a multipurpose fuel. A wide literature of kinetic studies is available for γ‐Al2O3, reference commercial catalyst but only a few authors report a kinetic analysis of attractive and alternative catalysts to γ‐Al2O3 in DME production. The aim of this work was to contribute in this direction, by performing a catalytic test focused on the determination of kinetic parameters for methanol dehydration over sulfonic acid catalysts and polymeric materials.RESULTSThe catalytic and kinetic behavior of these materials for the methanol to DME dehydration reaction has been investigated using a fixed bed reactor at total pressure of 1 bar within a temperature range of 50 to 450 °C. The sulfonated fluoropolymer (Aquivion) exhibited the highest activity and stability for the dehydration reaction at relatively low temperatures at which the γ‐Al2O3 did not display any dehydration activity. The tested catalysts showed good time stability when both methanol and methanol/water mixtures were used as feed reactants. Good agreement was achieved between experimental data and the proposed model.CONCLUSIONThe ‐SO3H groups enhanced the surface acidity and the catalytic performances. The sulfonated perfluorinated polymer (Aquivion) was able to catalyze the methanol/DME conversion at temperatures as low as 90 °C. The selectivity to DME at lower temperatures was 100%. Apparent activation energy for this reaction was experimentally evaluated to 110 KJ/mol and theoretical calculated to 96 KJ/mol: there was a comparable and good agreement with the experimental data. © 2020 Society of Chemical Industry

Efficient nitrate removal from synthetic groundwater via in situ utilization of short-chain fatty acids from methane bioconversion

Abstract Nitrate (NO3−) removal from groundwater is of great importance since it has posed a major risk to human health. Although methane-based denitrification processes have been developed, the practical application of methane as a carbon source for denitrification is constrained by either a long start-up time or a relatively low nitrate removal rate. This study investigated nitrate removal capacity by using a methane-based membrane biofilm reactor (MBfR) feeding with synthetic groundwater. A high nitrate removal rate of 706 mg-N L−1 d−1 was achieved, which is by far the highest rate reported for methane-based denitrification reactors. Short-chain fatty acids (SCFAs) were detected as products of methane bioconversion, with concentrations of acetic and propionic acid up to 168.8 mg L−1 and 50.2 mg L−1, respectively. Long-term operation and batch test results revealed that the SCFAs generated from methane bioconversion were in situ utilized for supporting nitrate removal as carbon and electron sources, thus leading to a practically useful removal rate. The findings suggest that it is promising to apply the methane-based MBfR to remove nitrate from nitrate contaminated groundwater.

Use of turbidimeter for measurement of solid catalyst system component in a reactor feed

We present a multi-region extension of power law background subtraction for core-level EEL spectra to improve the robustness of background removal. This method takes advantage of the post-edge shape of core-loss EEL edges to enable simultaneous fitting of pre- and post-edge background regions. This method also produces simultaneous and consistent background removal from multiple edges in a single EEL spectrum. The stability of this method with respect to the fitting energy window and the EELS signal to noise ratio is also discussed.

Mainstream-sidestream wastewater switching promotes anammox nitrogen removal rate in organic-rich, low-temperature streams

ABSTRACT The main issues with mainstream anammox application are loss of bacterial activity by low temperatures and by a high organic content of wastewater. We demonstrate a novel switching method between sidestream and mainstream wastewater. The wastewater flow was switched between sidestream (reject water at >22°C) and mainstream (municipal wastewater at 16.5°C), so that the anammox biomass activity and biomass growth could benefit from sidestream conditions. Real sidestream wastewater (biogas plant effluent) (≈1000 mg NH+ 4-N L−1) and synthetic mainstream (municipal wastewater-like source) (≈100 mg NH+ 4-N) wastewater were used for 20 L biofilm reactor feeding. The highest total nitrogen removal rate (TNRR) of 527 g N m−3 d−1 (average TNRR 180 (±140) g N m−3 d−1) was achieved with sidestream wastewater at a low chemical oxygen demand (COD)/TN ratio of 1.1/1. For reactor feeding with mainstream, the highest TNRR achieved was 61 g N m−3 d−1. Average TNRR for mainstream of 20 (±15) g N m−3 d−1 was low due to a higher COD/N ratio of 3.2/1. The highest TNRR in a batch test was achieved at the COD concentration of 480 mg L−1, reflecting a TNRR of ≈5 mg N g−1 TSS h−1. With a high COD concentration of 2600 mg L−1 (TOC/TN = 8/1), TNRR decreased similarly in both feeds to 1.6 mg N g−1 TSS h−1. The anammox microorganism's genus Candidatus Brocadia enrichment in deammonification biofilm reactor was higher in the mainstream operation (7.6% of all bacteria) than in sidestream operation period (<0.7% of all bacteria).

Selective Reduction of Oxygen on Non‐Noble Metal Copper Nanocatalysts

Efficient removal of molecular oxygen (O2) from flue gas is necessary to capture and utilize carbon dioxide (CO2) from fossil‐fuel sources. Herein, the catalytic reduction of O2 in simulated flue gases using alumina‐supported copper (Cu) nanostructures is presented. The Cu catalyst outperformed conventional palladium systems for the selectivity toward CO2 over carbon monoxide (CO). Varying the reactant feed ratio can lead to structural rearrangements at the surface of Cu nanoparticles, resulting in significant differences in catalytic activity. Under optimal conditions, a favorable Cu@CuOx core‐shell structure is observed to exhibit both excellent activity and selectivity to CO2. The simulated flue gas is purified from 85% to &gt;99.9% (v/v) CO2 after passing the catalytic system. The catalyst also exhibits high stability, showing only ≈0.1% drop in CO2 after 10 h on stream. This design marks progress toward the sequestration of CO2 and the development of non‐noble catalysts by tuning their dynamic nanostructures under controllable reaction conditions.

Promoting effects of water on the NH3-SCR reaction over Cu-SAPO-34 catalysts: transient and permanent influences on Cu species.

Cu-SAPO-34 catalysts with varied Cu loadings were synthesized through ion exchange to study the influence of water on the NH3-SCR reaction. The catalytic activities were evaluated by selective catalytic reduction of NO under a reactant feed in the presence/absence of water. Transient experiments were designed to study the response of NO conversion to the presence of water. H2-TPR and DFT calculations were performed to study the reducibility of Cu species. NH3-TPD and XPS were conducted to reveal the migration of Cu species. The results show that water could remarkably improve NO reduction activities and the promoting effect is more significant on the catalyst with low Cu loading. Both transient and permanent influences were found in this promoting phenomenon. For the transient influence, water has been proved to accelerate the re-oxidation half-cycle. Moreover, water can enhance the promoting effect of the SCR feed on the migration of Cu species. These unanchored Cu ions migrate to defect sites to form active sites, which lead to a permanent influence of water.

Influence of the multi-component electrical feed of air-core industrial reactors on their sound radiation

High voltage devices such as dry-type air-core reactors are subjected to environmental noise standards. Their excitation is due to Lorentz forces originated from the magnetic field, created by the coil itself, combined with the feed current. The objective of this paper is to show how spectral components present in the supply current of industrial dry-type air-core reactors is likely to produce a significant acoustic radiation. First, the multi-component distribution of the Lorentz forces is established. Then, the multi-physics computation process allowing to determine the acoustic pressure induced by each force component is presented. Finally, two industrial reactors are studied: a single and a multi-layer coil. It is pointed out that significant acoustic emergence can be induced by the interaction between small current spectral components with the fundamental or with each other.

Dry reforming of CH4 over stabilized Ni-La@KCC-1 catalyst: Effects of La promoter and optimization studies using RSM

A bimetallic Ni-La catalyst supported on fibrous silica KCC-1 (KAUST Catalysis Centre 1) was prepared by in situ one-pot hydrothermal method. The catalyst was characterized by XRD, BET, FESEM-EDX, TEM, H2-TPR, FTIR-pyrrole, O2-TPO and XPS. The H2-TPR result revealed that the addition of La2O3 enhanced the reducibility of Ni2+, as observed by the 25.1 % increase in H2 consumption. This is an evidence of improved dispersion as also indicated in the TEM images. Extra affinity for CO2 chemisorption and activation was provided by the La promoted catalyst with strong and intense basic sites to improve product selectivity. Therefore, the activity of catalyst was improved with significant enhancement in CO2 conversion and H2/CO selectivity. As a result, the activation energy for CO2 and CH4 conversions were reduced by a margin of 10.4 kJ/mol and 2.2 kJ/mol respectively. Ni-La@KCC-1 catalyst showed no sign of deactivation throughout the 22 h time on stream while Ni@KCC-1 deactivated after 15 h at a higher reactant feed composition. From ANOVA analysis, the reaction temperature is the most significant variable that influence CH4 conversion. The reaction operating condition was obtained that gives the optimum CH4 conversion. The model predicted response was 98.2 % fitted to the observed experimental values.

Analysis of the performance of an L-valve feeding spent coffee ground powders into a circulating fluidized bed

Waste biomass powders are appealing to generate renewable energy and to reduce the dependence on fossil fuels, however, feeding reactors in processing is still a challenge. This paper examines the performance of a non-mechanical L-valve to feed dry and moist Spent Coffee Ground (SCG) powders into a circulating fluidized bed under a broad range of conveying and aeration flowrates. The L-valve performed as a robust feeder, providing stable solids circulation rate (WS) for most of the tested conditions. Solid mass flowrates were not affected by fluctuations in the riser air flowrate up to ±15%. We verified that the L-valve performance is limited by a deterioration of powders' flowability. Lower values of WS and narrower operating ranges were observed when feeding dry SCGs powders and samples containing fine particles. Nevertheless, the feeder can be considered a good option to handle SCGs with moisture content close to 30% w.b. and a mean particle size of 400 μm. This is an appealing result since the moisture content of SCGs burned in the soluble coffee industry ranges from 25 to 50%. Solids feeding was stable and operation was smooth in a range of 1.2 < WS < 10.0 g/s. Finally, a correlation to predict Ws from the pressure drop in the L-valve is proposed, which fitted our data better than other equations available in the literature.

Comparison of the improved processes for amyl acetate synthesis by reactive distillation in different operating modes

AbstractThe application of heat integrated technology can decrease the energy consumption of the reactive distillation process but also increase the coupling degree, which means that the trouble of control is increased. As the improved process of the conventional reactive distillation (CRD) process with excess reactant feed, the design and control of a reactive dividing‐wall column (RDWC) process are explored for synthesizing amyl acetate. The results indicate that the TAC exhibits 12.15% savings compared with the CRD process and robust control is implemented in control schemes CS2 and CS3. In the analysis of the dynamic response results, a novel analytical method is applied, which includes a comprehensive analysis of the vapour flow rate and conversion rate. In addition, the economics and controllability of the two improved processes for synthesizing amyl acetate are compared that involve the different pressure thermally coupled reactive distillation (DPT‐RD) and RDWC processes. The comparison results indicate that the steady‐state economics of the RDWC process are less than those of the DPT‐RD process, but the RDWC process is more applicable industrially in terms of controllability, in which only the tray temperature control is required.

Microaerated UASB reactor treating textile wastewater: The core microbiome and removal of azo dye Direct Black 22.

Sequential anaerobic and aerobic processes have been recommended to treat textile wastewater reliably. In this work, the focus was on finding an energetically more competitive system to remove tetra-azo dye Direct Black 22 (DB22). We operated two upflow anaerobic sludge blanket (UASB) reactors (R1 and R2) in three phases (PI, PII, and PIII). R1 was operated as a conventional UASB, while R2 was microaerated in the upper part (0.18 ± 0.05 mg O2. L-1), aiming to remove DB22 simultaneously with the aromatic amine byproducts. PI consisted of feeding reactors with synthetic textile wastewater (STW), PII had higher salinity in the STW, and PIII was the same as PII, plus sulfate. The results showed that color and COD removal efficiencies were similar for both reactors (67-72% for R1 and 59-78% for R2) without a substantial influence of oxygen in R2. However, microaeration played a crucial role in R2 by removing the anaerobically formed aromatic amines; during PIII, the effluent was 16 times less toxic than that of R1. The microbial community that developed in the sludge bed of both reactors was quite similar, with the core microbiome represented by Trichococcus, Syntrophus and Methanosaeta genera. The increase in salinity in PII and PIII promoted a shift in the microbial community, excluding salty-sensitive genera from the core microbiome. The putative genera Brevundimonas and Ornatilinea were associated to aromatic amine microaerobic removal. Therefore, there is a potential application of a compact microaerated anaerobic system for textile wastewater treatment.

Aggregation of immobilized enzyme during transesterification of triolein and methanol, and the effect of two types of aggregates on reaction yield

During the transesterification of triglycerides with methanol catalyzed by immobilized lipase resin (Novozym 435 (N435)) in a glass vial, two types of aggregate of N435 particles were observed: a thin-layer aggregate on the glass surface inside the vial, and bulky aggregates. This prompted us to investigate the conditions under which only one type of aggregate could be formed, by changing the material from which the reaction vial was made and the feed ratio of N435 to the cross section of the reaction glass vial. When a polypropylene vial was used, only the bulky aggregates were formed, and reducing the feed ratio led to only the thin-layer aggregate being formed. We also examined the influence of morphological variation of the aggregates on the reaction yield. The thin-layer aggregate showed high activity, with a reaction yield of 0.932. In contrast, the bulky aggregate grew as the reaction time elapsed, resulting in a reduction in the surface area of the enzyme resin, consequently giving not only a reaction yield of about 0.454 but also low repeatability. These results show that the reactor material and feed ratio strongly affect the reaction yield as well as the aggregation form of enzyme resin. Finally, the durability of the thin-layer aggregate and the effect of accumulation of glycerin were investigated.

Selective Oxidative Cracking of n-Butane to Light Olefins over Hexagonal Boron Nitride with Limited Formation of COx.

In recent years, hexagonal boron nitride (hBN) has emerged as an unexpected catalyst for the oxidative dehydrogenation of alkanes. Here, the versatility of hBN was extended to alkane oxidative cracking chemistry by investigating the production of ethylene and propylene from n-butane. Cracking selectivity was primarily controlled by the ratio of n-butane to O2 within the reactant feed. Under O2 -lean conditions, increasing temperature led to increased selectivity to ethylene and propylene and decreased selectivity to COx . In addition to surface-mediated chemistry, homogeneous gas-phase reactions likely contributed to the observed product distribution, and a reaction mechanism was proposed based on these observations. The catalyst showed good stability under oxidative cracking conditions for 100 h time-on-stream while maintaining high selectivity to ethylene and propylene.

Bio-oil and Fuel Gas Production from Agricultural Waste via Pyrolysis: A Comparative Study of Oil Palm Empty Fruit Bunches (OPEFB) and Rice Husk

Biomass-based energy from agricultural wastes is a promising alternative energy source since its abundant supply and renewable. Biomass is converted into gas and liquid fuel through biochemical or thermochemical treatments. In this work, oil palm empty fruit bunches (OPEFB) and rice husk are pyrolyzed to produce gas and liquid fuel. The reactor temperature and feed mass are varied to obtain the best operating condition in a semi-batch pyrolysis reactor. The experimental results showed that the best operating temperature in pyrolysis process to produce bio-oils from OPEFB and rice husk was at 500 °C with 4.3 % (w/w) and 2.6 % (w/w) of bio-oil yields, respectively. The pyrolysis product distribution and their chemical composition are strongly affected by operating condition and the types of biomass. The GC-MS analysis results showed that the primary pyrolysis products components consist of hydrocarbons and oxygenated compounds such as carboxylic acids, phenols, ketones and aldehydes. Thermodynamic properties such as thermal conductivity of the biomass also influenced the product distribution of the biomass pyrolysis.

Influence of acidity on the performance of silica supported tungsten oxide catalysts assessed by in situ and Operando DRIFTS

The types of acidity on WOx/SiO2 catalysts prepared with different tungsten loadings (5 and 9 wt.% W) and pretreatment atmospheres (N2 and H2) were clarified by using the in situ diffuse reflectance infrared Fourier transform spectroscopy with temperature-programmed desorption (in situ DRIFTS-TPD) technique. Ammonia (NH3) acted as probe molecules that could block Lewis acid site type II (1620 cm−1) on the studied catalysts. The reactant feed containing 2% trans-2-butene or mixed feed of 2% trans-2-butene and 4% ethylene were used to investigate the reaction pathway on the WOx/SiO2 catalysts. Combining the Operando DRIFTS with gas chromatography-flame ionization detector (Operando DRIFTS-GC-FID) technique and in situ DRIFTS-TPD led to more deeply understanding of the correlation of acid sites and the primary cross metathesis reaction as the main reaction with isomerization of trans-2-butene as the side reaction. The adsorption energy of pulse chemisorption of 1-butene on catalyst by in situ DSC, confirmed the presence of the Lewis acid site type II related to the opportunity of 1-butene adsorption. The results confirmed that the Lewis acid site at 1620 cm−1 was crucial for the secondary metathesis reaction of 1-butene.

The performance evaluation of an industrial membrane reformer with catalyst-deactivation for a domestic methanol production plant

Methane reforming is the most important and economical process for hydrogen and syngas generation. In this work, the dynamic simulation of methane steam reforming in an industrial membrane reformer for synthesis gas production is developed. A novel deactivation model for commercial Ni-based catalysts is proposed and the monthly collected data from an existing reformer in a domestic methanol plant is used to optimize the model parameters. The plant data is also employed to check the model accuracy. It was observed that the membrane reformer could compensate for the catalyst deactivating effect.In order to assure the long membrane lifetime and decrease the unit price, the membrane reformer with 5 μm thick Pd on stainless steel supports is modeled at the temperature below the maximum operating temperature of Pd based membranes (around 600 °C). The dynamic modeling showed that the methane conversion of 76% could be achieved at a moderate temperature of 600 °C for an industrial membrane reformer. The cost-effective generation of syngas with an appropriate H2/CO ratio of 2.6 could be obtained by membrane reformer. This is while the conventional reformer exhibits a maximum conversation of 64 at 1200 °C challenging due to its high syngas ratio (3.7). On the other hand, the pure hydrogen from membrane reformer can supply part of the ammonia reactor feed in an adjacent ammonia plant.

Continuous-feed carbonation of waste incinerator bottom ash in a rotating drum reactor

Carbonation is a key process in the aging of waste incinerator bottom ash (BA). The reaction with CO2 decreases the BA alkalinity and lowers the leachability of amphoteric trace metals. Passive ageing over several months is usually performed in intermittently mixed BA heaps. Here we aimed at accelerating the process in a rotating drum reactor continuously fed with the BA and the reactant gas (10 vol-% CO2, volumetric flow rate 60 L/min). In one test, the gas was heated and humidified. Since carbonation depends on the specific CO2-supply, experiments were conducted at varied BA residence time (60, 80, and 100 min). Residence time was calculated by mass balancing and confirmed by the breakthrough time of two tracers. Leachates and solid phase properties of the treated BA served to evaluate the carbonation performance. The residence time of BA could be adequately controlled by the reactor loading and feed rate. A residence time of 80 min was sufficient to reduce the BA leachability such as to comply with the German regulatory standards for non-hazardous waste, whereas the untreated BA was hazardous waste. Decreased alkalinity was indicated by lower leachate pH and Ca(OH)2 contents of the BA as compared to the input. Leachate concentrations of amphoteric trace metals (Pb, Zn, Cu) decreased by at least one order of magnitude while oxyanions became slightly more mobile upon carbonation. In view of relatively short residence times and stable process performance, the rotating drum reactor seems promising for a full-scale implementation of BA carbonation.

Mapping the operating performance of a novel internally circulating fluidized bed reactor applied to chemical looping combustion

Chemical looping combustion is a promising technology for minimizing the energy penalty of CO2 capture. To accelerate the scale-up and commercialization of this technology for pressurized operation, the internally circulating reactor (ICR) was recently proposed. ICR integrates the two reactors, cyclones, loop seals and solids transport lines of the conventional chemical looping configuration into a single unit that simplifies design and operation. This work reports the ICR operating performance over a range of operating parameters applied to chemical looping combustion (CLC). The concept proved relatively simple to operate, allowing the oxygen-carrier circulation rate to be controlled over a wide range by varying the bed loading and the air reactor feed rate. Fully autothermal CLC operation was demonstrated as an illustration of the ease of ICR operation. Gas leakage between the two reactor chambers decreased strongly with decreasing solids loading, resulting in CO2 capture and purity up to 94% for the lowest bed loading. The data showed that significant room for further optimization of the solids transport ports in the reactor exists, which will further increase the CO2 separation performance. These results demonstrate the promise of ICR concept and provide valuable insights for the design of larger-scale units in future work.

Effect of oxygen addition, reaction temperature and thermal treatments on syngas production from biogas combined reforming using Rh/alumina catalysts

Dry reforming and partial oxidation of biogas were studied using 0.5wt.% Rh/Al2O3 catalysts, both in-house prepared and commercial. The effects of O2 addition on syngas yield and biogas conversion were studied at 700°C using different O2/CH4 ratios in the gas feeding stream: 0 (dry reforming), 0.12, 0.25, 0.45 and 0.50. The highest CH4 conversion, H2 yield and H2/CO molar ratio were obtained with an O2/CH4 ratio of 0.45, even though simultaneous valorization of both CH4 and CO2 could be best attained when the O2/CH4 ratio was 0.12. Increased biogas conversions and syngas yields were obtained by increasing reaction temperatures between 650 and 750°C. A detrimental influence on catalytic activity could be observed when the catalyst was subjected to calcination. Increasing the hold time of the thermal conditioning of the catalyst under inert flow altered Rh dispersion, though had no significant impact on catalyst performance in the dry reforming of methane at 700°C and 150N L CH4/(gcath). Characterization of spent samples after reaction by Raman spectroscopy revealed the presence of carbonaceous deposits of different nature, especially on the commercial (named as Rh com) and calcined (Rh calc) catalysts, though oxygen addition in the biogas feed significantly reduced the amount of these deposits. The Rh catalysts that had not been calcined after impregnation (Rh prep) did not present any noticeable characteristic peaks in the G and D bands. In particular, scanning transmission electron microscopy (STEM) images of the spent Rh prep sample revealed the presence of very highly dispersed Rh nanoparticles after reaction, of particle sizes of about 1nm, and no noticeable C deposits. Combined oxy-CO2 reforming of biogas using highly dispersed and low metal-loading Rh/Al2O3 catalysts with low O2 dosage in the reactor feed can be used to effectively transform biogas into syngas.

Simulated Heat Integration Study of Reactive Distillation Column for Ethanol Synthesis

Ethanol is largely used as a solvent in the synthesis of varnishes and perfumes. It is also used as a preservative for biological products, fuel, and gasoline additives. Anethanol-water mixture, normally obtained by fractional distillation yields an azeotropic solution consisting of approximately 95 w% of ethanol. The synthesis of ethanol in a reactive distillation column with the azeotropic feed at 20oC with ethylene oxide as another reactant feed for the reaction with water to produce ethylene glycol was simulated in Aspenplus. Simulated results show 98.82 mol% purity of ethanol in the reactive distillation column. In order to reduce the energy consumption in reactive distillation, a Reactive Heat Integrated Distillation Column (R-HIDiC) is proposed for the same purity of ethanol product. From the simulated results, it has been found that the overall energy utilization in the proposed distillation column is reduced by 65% as compared to the conventional reactive distillation column. The pressure profile, temperature profile, and concentration profile of the reactive distillation column and the column proposed are also compared.