Enhanced mono-aromatics production by the CH4-assisted pyrolysis of microalgae using Zn-based HZSM-5 catalysts.

This study presents the catalytic pyrolysis of microalgae, Chlorella vulgaris (C. vulgaris), using pure CH4 and H2-rich gas evolved from CH4 decomposition on three different HZSM-5 catalysts loaded with Zn, Ga, and Pt, aimed specifically at producing high-value mono-aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEX). In comparison with that for the typical inert N2 environment, a pure CH4 environment increased the bio-oil yield from 32.4 wt% to 37.4 wt% probably due to hydrogen and methyl radical insertion in the bio-oil components. Furthermore, the addition of bimetals further increased bio-oil yield. For example, ZnPtHZ led to a bio-oil yield of 47.7 wt% in pure CH4. ZnGaHZ resulted in the maximum BTEX yield (6.68 wt%), which could be explained by CH4 activation, co-aromatization, and hydrodeoxygenation. The BTEX yield could be further increased to 7.62 wt% when pyrolysis was conducted in H2-rich gas evolved from CH4 decomposition over ZnGaHZ, as rates of aromatization and hydrodeoxygenation were relatively high under this condition. This study experimentally validated that the combination of ZnGaHZ and CH4 decomposition synergistically increases BTEX production using C. vulgaris.

Impact of Duration of Catheterization on the Success Rate of Trial Without Catheter in Acute Urinary Retention Due to Benign Prostatic Enlargement.

BACKGROUND: The most common cause of acute urinary retention in men over 50 is benign prostate enlargement (BPE). Following the urethral catheterization, a trial without a catheter (TWOC) under the cover of alpha-blockers is given. The timing of TWOC varies from Day 3 to Day 7 of the retention episode. There is a need to study the improvement in the success rate of TWOC with the increasing number of days of catheterization. OBJECTIVE: To measure the success rate of TWOC in acute urinary retention due to benign prostatic enlargement with increasing days of catheterization. METHOD: The study was conducted in Social Security Teaching Hospital Lahore. Patients who presented with acute urinary retention due to benign prostatic enlargement were catheterized and given alpha-blockers. The patients were divided into two groups, one group having TWOC after three days and the other having TWOC after seven days. The success rate of TWOC was calculated and compared in the two groups. All patients included in the study had the first episode of acute retention with a moderately enlarged prostate and no element of second pathology or neurological deficit. RESULTS: A total of 48 patients were included in the study, divided into two groups of 24 patients each. In the first group who underwent TWOC after seven days of catheterization, 15 out of 24 patients had successful TWOC with a success rate of 62.5%. In the second group of 24 patients, who had TWOC after three days of catheterization, only 11 patients had successful TWOC with a success rate of 45.8%. CONCLUSION: There was a marked improvement in the success rate of TWOC with increasing days of catheterization after an acute retention episode, secondary to BPE.

Sewage sludge steam gasification over bimetallic mesoporous Al-MCM48 catalysts for efficient hydrogen generation.

This study explored the potential of steam gasification of sewage sludge over different temperatures (non-catalytic) and bimetallic (Ni-Fe and Ni-Co) mesoporous Al-MCM48 (3-5% Al basis). The higher temperature (800 °C) resulted in higher gas yield (36.74 wt%) and syngas (H2 and CO) selectivity (35.30 vol% and 11.66 vol%). Moreover, catalytic approach displayed that the Al-MCM48 was effective support because the incorporation of nickel increased the efficiency of gasification reactions compared to HZSM-5 (30). It mainly comes from the presence of mesopores and higher surface area (710.05 m2/g) providing more reaction sites and higher stability (less coke formation). Furthermore, the addition of promoters such as Co and Fe allowed the formation of Ni-Fe and Ni-Co alloys, resulting in even higher gas yield and overall H2 and CO selectivity due to the promotion of related reactions such as tar cracking, Boudouard, water gas shift and reforming and so on. Ni-Co alloy catalyst (10% Ni-5% Co/Al-MCM48) resulted in the highest H2 (∼52 vol%) selectivity due to the enhanced Ni dispersion and synergy effect between Ni and Co. Moreover, the application of bi-metal alloy on Al-MCM48 showed no coke formation and significantly reduced CO2 and hydrocarbon selectivity in the product gas. Overall, this study presented a promising solution for sewage sludge disposal in terms of clean H2 generation, reduction in CO2 and higher stability of metal based catalysts at the same time.

Microalgae gasification over Ni loaded perovskites for enhanced biohydrogen generation.

Steam gasification of microalgae upon perovskite oxide-supported nickel (Ni) catalysts was carried out for H2-rich gas production. Ni-perovskite oxide catalysts with partial substitution of B in perovskite structures (Ni/CaZrO3, Ni/Ca(Zr0.8Ti0.2)O3, and Ni/Ca(Zr0.6Ti0.4)O3) were synthesized and compared with those of the Ni/Al2O3 catalyst. The perovskite oxide supports improved Ni dispersion by reducing the particle size and strengthening the Ni-support interaction. Higher gas yields and H2 selectivity were obtained using Ni-perovskite oxide catalysts rather than Ni/Al2O3. In particular, Ni/Ca(Zr0.8Ti0.2)O3 showed the highest activity and selectivity for H2 production because of the synergetic effect of metallic Ni and elements present in the perovskite structures caused by high catalytic activity coupled with enhanced oxygen mobility. Moreover, increasing the temperature promoted the yield of gas and H2 content. Overall, considering the outstanding advantages of perovskite oxides as supports for Ni catalysts is a promising prospect for H2 production via gasification technology.

H2 generation from steam gasification of swine manure over nickel-loaded perovskite oxides catalysts.

In this study, nickel-loaded perovskite oxides catalysts were synthesized via the impregnation of 10%Ni on XTiO3 (X = Ce, Sr, La, Ba, Ca, and Fe) supports and employed in the catalytic steam gasification of swine manure to produce H2-rich syngas for the first time. The synthesized catalysts were characterized using BET, H2-TPR, XRD, HR-TEM, and EDX analysis. Briefly, using perovskite supports resulted in the production of ultrafine catalyst nanoparticles with a uniform dispersion of Ni particles. According to the catalytic activity test, the gas yield showed the increment as 10% Ni/LaTiO3 < 10% Ni/FeTiO3 < 10% Ni/CeTiO3 < 10% Ni/BaTiO3 < 10% Ni/SrTiO3 < 10% Ni/CaTiO3. Meanwhile, zero coke formation was achieved due to the oxygen mobility of prepared catalysts. Also, the increase in the H2 production for the applied catalysts was in the sequence as 10% Ni/CeTiO3 < 10% Ni/FeTiO3 < 10% Ni/LaTiO3 < 10% Ni/BaTiO3 < 10% Ni/SrTiO3 < 10% Ni/CaTiO3. The maximum H2 selectivity (∼48 vol%) obtained by10% Ni/CaTiO3 was probably due to the synergistic effect of Ni and Ti on enhancing the water-gas shift reaction, and Ca on creating the maximum oxygen mobility compared to other alkaline earth metals doped at the A place of perovskite. Overall, this study provides a suitable solution for enhanced H2 production through steam gasification of swine manure along with suggesting the appropriate supports to prevent Ni deactivation by lowering coke formation at the same time.

Valorization of biomass through gasification for green hydrogen generation: A comprehensive review.

Green and sustainable hydrogen from biomass gasification processes is one of the promising ways to alternate fossil fuels-based hydrogen production. First off, an overview of green hydrogen generation from biomass gasification processes is presented and the corresponding possible gasification reactions and the effect of respective experimental criteria are explained in detail. In addition, a comprehensive explanation of the catalytic effect on tar reduction and hydrogen generation via catalytic gasification is presented regarding the functional mechanisms of various types of catalysts. Furthermore, the commercialization aspects, the associated technical challenges and barriers, and the prospects of a biomass gasification process for green hydrogen generation are discussed. Finally, this comprehensive review provides the related advancements, challenges, and great insight of biomass gasification for the green hydrogen generation to realize a sustainable hydrogen society via biomass valorization.

Technical benefits of using methane as a pyrolysis medium for catalytic pyrolysis of Kraft lignin.

Catalytic fast pyrolysis of low sulfonated Kraft lignin was performed under different atmospheric environments such as N2, CH4, and the gas derived from CH4 decomposition (CH4-D). The use of Zn- or Mo-loaded HZSM-5 as catalyst led to a higher pyrolytic oil yield compared to parent HZSM-5 in CH4 and CH4-D atmospheres. The yields of benzene, toluene, and xylenes were increased by the synergistic effects from metal loading, higher H/Ceff ratio, higher acidity, and CH4 activation. The enhanced CH4 activation via metal loading resulted in higher methylation of alkyl moieties and 33% increase in the total yield of benzene, toluene, and xylenes in comparison to parent HZSM-5. A higher H/Ceff ratio of 6 via CH4 decomposition led to the formation of a hydro-pyrolysis environment. Moreover, the CH4-D environment showed H2/CH4 ratio of 0.36 in the product gas which warranted the presence of more H2 under the CH4-D pyrolysis environment.

Valorization of hazardous COVID-19 mask waste while minimizing hazardous byproducts using catalytic gasification.

This study proposes a method to valorize hazardous waste such as used COVID-19 face mask via catalytic gasification over Ni-loaded ZSM-5 type zeolites. The 25% Ni was found as an optimal loading on ZSM-5 in terms of H2 production. Among different zeolites (ZSM-5(30), ZSM-5(80), ZSM-5(280), mesoporous (m)-ZSM-5(30), and HY(30)), 25% Ni/m-ZSM-5(30) led to the highest H2 selectivity (45.04 vol%), most likely because of the highest Ni dispersion on the m-ZSM-5(30) surface, high porosity, and acid site density of the m-ZSM-5(30). The content of N-containing species (e.g., caprolactum and nitriles) in the gasification product was also reduced, when steam was used as gasifying agent, which is the source of potentially hazardous air pollutants (e.g., NOx). The increase in the SiO2/Al2O3 ratio resulted in lower tar conversion and lower H2 generation. At comparable conditions, steam gasification of the mask led to ~15 vol% higher H2 selectivity than air gasification. Overall, the Ni-loaded zeolite catalyst can not only suppress the formation of hazardous substances but also enhance the production of hydrogen from the hazardous waste material such as COVID-19 mask waste.

Waste furniture gasification using rice husk based char catalysts for enhanced hydrogen generation.

Present study provides biohydrogen production methods from waste furniture via catalytic steam gasification with bio-char catalysts (raw char, KOH-activated char and steam-activated char). Total gas yield for the prepared chars was in the order of KOH-activated char > steam-activated char > raw char, whereas, H2 selectivity was in the sequence of raw char > steam-activated char > KOH-activated char. Though KOH-activated char showed the highest gas yield, highest H2 selectivity was obtained at the gasification experiment with raw char due to the large amount of Ca and K and its reasonable surface area (146.89 m2/g). Although the activation of raw biochar results in the increase of gas yield, it has the negative effect on H2 generation due to the removal of alkali and alkaline earth metals for the KOH activated char and steam-activated char. This study shows that raw bio-char could be a potential solution for eco-friendly hydrogen production.

Catalytic steam gasification of food waste using Ni-loaded rice husk derived biochar for hydrogen production.

The disposal of food waste (FW) is a major cause of environmental contamination. This study reports an environmentally friendly FW disposal method in the form of catalytic steam gasification using various types of Ni-loaded chars (untreated char, steam-treated char, and ZnCl2-treated char). The results were also compared with the gasification results from the Ni catalysts supported on commercial α-alumina (Ni/α-Al2O3). The Ni/steam-treated char showed the maximum hydrogen generation (0.471 mol/(g feedstock•g cat)) because of the high reducibility, high nickel dispersion, large amount of inherent K and Ca, and moderate surface area. The overall gas and H2 yield were observed in the following order: Ni/steam-treated char > Ni/ZnCl2 treated char > Ni/untreated char > Ni/α-Al2O3. Brunauer-Emmett-Teller analysis of various catalysts showed that the treated chars have a mesoporous structure, and the X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy - energy dispersive spectroscopy showed that the presence of silica in the chars providing the stable support for the Ni loading and prevented coke formation. The chars obtained from biomass pretreatment could be a potential solution for preventing coke formation at high temperatures, thereby increasing the gas yield and enhancing hydrogen generation.

Catalytic Oxidation of Toluene with Ozone Over the Ru-Mn/Desilicated Nanoporous H-Zeolite Socony Mobil-5 at Room Temperature.

In this study, the effect of Ru-Mn bimetallic catalysts in combination with a zeolite support on the removal of toluene in the presence of ozone at room temperature was investigated. Desili-cated HZSM-5 (DZSM) was fabricated and applied as a Ru-Mn support for the removal of toluene (100 ppm) in the presence of ozone (1000 ppm) at room temperature. The surface area, pore volume, and average pore size of Ru-Mn with a DZSM support (RuMn/DZSM) were measured and compared with those of Ru-Mn/HZSM-5 (RuMn/HZSM). The pore size of RuMn/DZSM (69 Å) was much larger than that of RuMn/HZSM-5 (5.5 Å). In addition, the pore volumes of RuMn/DZSM and RuMn/HZSM were 0.64 and 0.25 cm³/g, respectively. Furthermore, the ratios of Mn³+/Mn4+ and Ovacancy/Olattice of RuMn/DZSM were larger than those of RuMn/HZSM-5. The removal efficiency of toluene of RuMn/DZSM was higher than that of RuMn/HZSM due to its larger pore volume, pore size, and the increased ratios of Mn³+/Mn4+ and Ovacancy/Olattice.

Emulsification of Catalytic Pyrolysis Oil from Nanoporous Zeolite Socony Mobil-5 with Diesel Using a Range of Emulsifiers in an Ultrasonicator.

Catalytic pyrolysis oil (CPO) was produced from lignin using the ex-situ mechanism and nanoporous HZSM-5 (SiO2/Al2O3 = 50) as a catalyst. The oil contained phenolics, esters, acids, and benzene derivatives as the major constituents. The emulsification of CPO in diesel was tested with several emulsifier combinations such as Span 80 and Tween 60, Span 80 and Atlox 4916, and Atlox 4916 and Zephrym PD3315 in the HLB range of 5.8-7.3. The HLB value of 5.8 using the combination of Span 80 and Atlox 4916 and the CPO:emulsifier:diesel ratio of 5:2:93 (wt%), provided a stable emulsion for 10 days. The physiochemical properties of that emulsion were comparable to diesel. Hence, emulsions of CPO and diesel can potentially be used as a diesel engine fuel.

Catalytic upgrading of Quercus Mongolica under methane environment to obtain high yield of bioaromatics.

This work investigated the impact of pyrolysis medium and catalyst on the production of bio-BTX (benzene, toluene, and xylene) from Quercus Mongolica (Q. Mongolica) via catalytic pyrolysis. Two different pyrolysis media (N2 and CH4) and five different zeolite catalysts (HY, HBeta, HZSM-5, 1 wt% Ni/HZSM-5, and 1 wt% Ga/HZSM-5) were considered for the Q. Mongolica pyrolysis. The HZSM-5 yielded more BTX than the HY and HBeta due to its strong acidity. The employment of CH4 as the pyrolysis medium improved the BTX yield (e.g., 2.7 times higher total BTX yield in CH4 than in N2) and resulted in low coke yield (e.g., 5.27% for N2-pyrolysis and 2.57% for CH4-pyrolysis) because the CH4-drived hydrogen simulated a hydropyrolysis condition and facilitated dehydroaromatization reaction. CH4 also led to direct coupling, Diels-Alder, and co-aromatization reactions during the pyrolysis, contributing to enhancing the BTX yield. The addition of Ga to the HZSM-5 could further increase the BTX yield by means of facilitating hydrocracking/demethylation and methyl radical formation from CH4 assisting the generation of >C2 alkenes that could be further converted into BTX on acid sites of the HZSM-5.

Biohydrogen production from catalytic conversion of food waste via steam and air gasification using eggshell- and homo-type Ni/Al2O3 catalysts.

Steam and air gasification with 5 wt% Ni/Al2O3 eggshell (Ni-EG) and homo (Ni-H) catalysts were performed for the first time to produce biohydrogen from food waste. The steam gasification produced comparably higher gas yield than air gasification. In non-catalytic experiments, steam gasification generated a higher volume percent of H2, whereas more CO, CO2, CH4, and C2-C4 were produced in air gasification. Ni-EG demonstrated higher potential to obtain H2-rich gases with a low C2-C4 content compared to that obtained by Ni-H, particularly in steam gasification at 800 °C, which produced gaseous products with 59.48 vol% H2. The long-term activity of both catalysts in steam gasification was evaluated, and Ni-EG exhibited higher stability than Ni-H. The ideal distribution of Ni species on the outer region of γ-Al2O3 pellets in Ni-EG resulted in higher activity, stability, and selectivity than Ni-H in both steam and air gasification.

Direct conversion of NO and SO2 in flue gas into fertilizer using ammonia and ozone.

This study focused on the simultaneous removal of NO and SO2 from an industrial flue gas stream. To evaluate the removal efficiency of NO and SO2 using O3 and NH3, the consumption of two reactants (O3 and NH3) in line with the conversion of NO and SO2 was quantified experimentally. In addition, NO and SO2 were converted to valuable fertilizers, NH4NO3 and (NH4)2SO4. To identify a principle strategy to enhance the generation of fertilizer, Fourier transform infrared spectroscopy was used to examine the reaction mechanisms for the formation of NH4NO3 and (NH4)2SO4. Acceleration of SO2 oxidation could be achieved effectively by adding NO to a gas mixture of SO2, NH3, and O3. The formation of HNO3 might be enhanced by the simultaneous feeding of NO and SO2. Particle generation was also 10 times higher for NH3/(NO + SO2) than for NH3/NO and for NH3/SO2, which is a prominent feature of this study. Moreover, the introduction of steam had a positive influence on particle generation. This method offers dual applications for NO and SO2 removal from a flue gas stream and direct fertilizer generation.

Yellow Poplar Gasification Over Ni Silicate and Ni/Silica.

The activity of Ni silicates having different Ni/Si molar ratio (0.5 and 1) and Ni/silica were tested on biomass gasification. Ni silicate (Ni/Si= 0.5) and Ni/silica produced the higher gas yield than Ni silicate (Ni/Si = 1.0). The larger amount of H2 and CO were produced over Ni silicate (Ni/Si = 0.5) and Ni/silica compared those over Ni silicate (Ni/Si = 1.0). The catalysts were characterized using BET and XRD analysis. Ni silicate (Ni/Si = 0.5) showed promising activity for the production of syngas at higher temperature and can be employed in gasification.

Emulsification characteristics of ether extracted pyrolysis-oil in diesel using various combinations of emulsifiers (Span 80, Atlox 4916 and Zephrym PD3315) in double reactor system.

Emulsification is a cost effective and simple method to use pyrolysis oil (or bio-oil) along with diesel as an emulsified fuel. Several combinations of emulsifiers, such as Span 80 and Atlox 4916, Span 80 and Zephrym PD3315, and Atlox 4916 and Zephrym PD3315, were tested to obtain stable emulsions. Two set of reactors (ultrasonicator and agitator-based mechanical reactor system) were used for the process. The ether-extracted pyrolysis oil (EEO), emulsifier, and diesel content of 10%-15%, 3%, and 82-87% were exposed to an ultrasonic power of 40% and with an agitation rate of 900 rpm. The emulsions obtained using Span 80 and Zephrym PD3315 showed stratification within 10 min. The emulsions for Span 80 and Atlox 4916 with a ratio of 3/15/82 for Emulsifer/EEO/Diesel, and for Atlox 4916 and Zephrym PD3315 emulsifiers with a ratio of 3/10/87 for Emulsifer/EEO/Diesel remained stable for more than 15 days. The functional groups analysis showed the stability of the emulsion for Span 80 and Atlox 4916, whereas a change in the absorbance intensity was observed when Atlox 4916 and Zephrym PD3315 were used, indicating stratification.

Enhanced bioaromatics synthesis via catalytic co-pyrolysis of cellulose and spent coffee ground over microporous HZSM-5 and HY.

Catalytic co-pyrolysis (CCP) of spent coffee ground (SCG) and cellulose over HZSM-5 and HY was characterized thermogravimetrically, and a catalytic pyrolysis of two samples was conducted using a tandem micro reactor that directly connected with gas chromatography-mass spectrometry. To access the more fundamental investigations on CCP, the effects of the zeolite pore structure, reaction temperature, in-situ/ex-situ reaction mode, catalyst to feedstock ratio, and the SCG and cellulose mixing ratio were experimentally evaluated. The temperature showing the highest thermal degradation rate of cellulose with SCG slightly delayed due to the interactions during the thermolysis of two samples. HZSM-5 in reference to HY produced more aromatic hydrocarbons from CCP. With respect to the reaction temperature, the formation of aromatic hydrocarbons increased with the pyrolytic temperature. Moreover, the in-situ/ex-situ reaction mode, catalyst/feedstock, and cellulose/SCG ratio were optimized to improve the aromatic hydrocarbon yield.

An evaluation of thermal characteristics of bacterium Actinobacillus succinogenes for energy use and circular bioeconomy.

The thermal characteristics of Actinobacillus succinogenes (AS) from pyrolysis, torrefaction, and combustion are analyzed to evaluate the potential of this biomass as a renewable fuel. AS pyrolysis can be classified into four stages, and its main decomposition zone is at 200-500 °C. The solid yield of AS after 60 min torrefaction is over 60 wt%, and the torrefaction severity index map indicates that a high torrefaction temperature with a short duration has a more profound influence on its decomposition. The Py-GC/MS analysis of AS suggests that the volatile products from 500 °C pyrolysis are similar to microalgae-derived pyrolysis bio-oils. The combustibility index (S) of AS is 4.07 × 10-7 which is much higher than that of lignite coal (0.39 × 10-7) and bituminous coal (0.18 × 10-7), and close to those of biochar and bio-oil. The obtained results are conducive to the development of microorganisms as fuel to achieve a circular bioeconomy.

Acetaldehyde removal and increased H2/CO gas yield from biomass gasification over metal-loaded Kraft lignin char catalyst.

Acetaldehyde removal tests were performed to compare the catalytic activity of the Kraft lignin char (KC), KOH-treated Kraft lignin char (KKC), and activated carbon (AC) along with their impregnation with Mn in a plasma reactor. The gasification characteristics (syngas content, and H2/CO ratio) of yellow poplar were investigated using nickel catalysts supported on KC, KKC, AC, and γ-Al2O3 in a U-type quartz reactor. KKC and Mn/KKC improved significantly the surface area and contents of O and N functional groups over the raw char. In particular, Mn/KKC showed the highest acetaldehyde-removal efficiency. The catalytic activity of Ni-impregnated KC, KKC, AC, and γ-Al2O3 decreased in the order of Ni/KKC > Ni/AC > Ni/KC > Ni/γ-Al2O3 for the gas yield and Ni/γ-Al2O3 >Ni/KC > Ni/AC >Ni/KKC for the oil yield, respectively. The Ni/KKC provides a more conducive environment for gasification, resulting in larger amounts of syngas (H2 and CO) in the product gases. Moreover, Ni impregnated with char may be the most inexpensive and effective solution for achieving maximum tar reduction and syngas generation.