Highly Selective Syngas/H2 Production via Partial Oxidation of CH4 Using (Ni, Co and Ni–Co)/ZrO2–Al2O3 Catalysts: Influence of Calcination Temperature

In this study, Ni, Co and Ni–Co catalysts supported on binary oxide ZrO2–Al2O3 were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic system was then tested for syngas respective H2 production via partial oxidation of methane at 700 °C and 800 °C. The influence of calcination temperatures was studied and their impact on catalytic activity and stability was evaluated. It was observed that increasing the calcination temperature from 550 °C to 800 °C and addition of ZrO2 to Al2O3 enhances Ni metal-support interaction. This increases the catalytic activity and sintering resistance. Furthermore, ZrO2 provides higher oxygen storage capacity and stronger Lewis basicity which contributed to coke suppression, eventually leading to a more stable catalyst. It was also observed that, contrary to bimetallic catalysts, monometallic catalysts exhibit higher activity with higher calcination temperature. At the same time, Co and Ni–Co-based catalysts exhibit higher activity than Ni-based catalysts which was not expected. The Co-based catalyst calcined at 800 °C demonstrated excellent stability over 24 h on stream. In general, all catalysts demonstrated high CH4 conversion and exceptionally high selectivity to H2 (~98%) at 700 °C

Machine learning and computational chemistry to improve biochar fertilizers : a review

Traditional fertilizers are highly inefficient, with a major loss of nutrients and associated pollution. Alternatively, biochar loaded with phosphorous is a sustainable fertilizer that improves soil structure, stores carbon in soils, and provides plant nutrients in the long run, yet most biochars are not optimal because mechanisms ruling biochar properties are poorly known. This issue can be solved by recent developments in machine learning and computational chemistry. Here we review phosphorus-loaded biochar with emphasis on computational chemistry, machine learning, organic acids, drawbacks of classical fertilizers, biochar production, phosphorus loading, and mechanisms of phosphorous release. Modeling techniques allow for deciphering the influence of individual variables on biochar, employing various supervised learning models tailored to different biochar types. Computational chemistry provides knowledge on factors that control phosphorus binding, e.g., the type of phosphorus compound, soil constituents, mineral surfaces, binding motifs, water, solution pH, and redox potential. Phosphorus release from biochar is controlled by coexisting anions, pH, adsorbent dosage, initial phosphorus concentration, and temperature. Pyrolysis temperatures below 600 °C enhance functional group retention, while temperatures below 450 °C increase plant-available phosphorus. Lower pH values promote phosphorus release, while higher pH values hinder it. Physical modifications, such as increasing surface area and pore volume, can maximize the adsorption capacity of phosphorus-loaded biochar. Furthermore, the type of organic acid affects phosphorus release, with low molecular weight organic acids being advantageous for soil utilization. Lastly, biochar-based fertilizers release nutrients 2–4 times slower than conventional fertilizers

Toxic levels of aluminum and manganese and variation of nitrogen content in grape leaves.

Field and greenhouse studies were carried out to determine the effects of Al and Mn individually or collectively on the growth and elemental composition of various grape cultivars. Soil and plant tissue analyses were evaluated in two vineyard locations on which several grape varieties were established on a White House soil series. Soils at both locations were treated with soil amendments and N fertilizers. The results show that both soils are acidic at the top 30 cm surface and have a high extractable Al, Fe and in some cases Mn content. The field results further indicate that grape varieties respond differently to soil acidity in terms of their mineral composition. High soil Al, Fe and Mn resulted in a higher accumulation of these elements in grape leaves whereas the cation uptake especially P, Ca, Zn, and Cu were reduced. Field plants exhibiting P deficiency symptoms resulting from high soil Al and Fe had a 950 Mg kg⁻¹ Al and 400 mg kg⁻¹ Mn in their leaves. Furthermore, these plants had a deficient range of P, K, Ca and Zn. The Al treatments reduced shoot growth and decreased number of leaves. The growth reduction resulted from higher Al, Mn and Fe content of plant leaves and lower P, Ca and Cu. Furthermore high Al treatments of 30 mg 1⁻¹ and more in the nutrient solution resulted in lower accumulation of P, Ca, K, Mg, Fe and Cu. The different parameters were affected by Al levels to different degrees and were more pronounced at a later stage of growth than the earlier stage of growth. The concentration of Al in plant tops at which Al toxicity symptoms appeared was 800 mg kg⁻¹ Al or more. Mn treatments reduced plant growth, decreased number of leaves and induced toxicity symptoms. The percent reduction of growth parameters was greatest at highest Mn levels. The reduced growth resulted from the deficiency of several mineral elements such as Ca, Fe, Zn and Cu and higher accumulation of Mn in plant tissue. The effect of Mn levels on the elemental composition especially Fe, Zn, Cu, Ca and P increased progressively as plant growth progressed. The 10% reduction in growth occurred when plant had accumulated 400 mg kg⁻¹ Mn in their tops. The accumulation of elements in plant leaves was varied at various stages of growth as a function of time and Mn and/or Al concentration in the nutrient solution. The growth reduction and the severity of toxicity symptoms were proportional to either Al, Mn or Al + Mn concentrations in the nutrient solution as well as their accumulation in plant tops

Suppression of carbon formation in CH4–CO2 reforming by addition of Sr into bimetallic Ni–Co/γ-Al2O3 catalyst

Bimetallic catalysts, containing 5 wt% Ni + 5 wt% Co supported on γ-Al2O3 combined with different amounts of Sr promoter ranging from 0 to 1 wt%, for dry reforming reaction were prepared by the impregnation method. The dry reforming reaction was carried out at atmospheric pressure using CO2/CH4/N2 feed ratio of 17/17/2, F/W = 60 mL/min gcat and reaction temperature range of 500–700 °C. The performance of the developed catalyst was evaluated by estimating the CH4 and CO2 conversions, and by performing a long run stability test. The fresh and spent catalysts were characterized by BET, TGA, TPD, TPR, and TPO. The bimetallic catalysts provided higher activity than the monometallic-catalysts. When the bimetallic was promoted with Sr, the activity decreased slightly however, the stability enhanced. The best stability, estimated by the deactivation factor, and less carbon deposition, measured by TGA, were obtained when 5Ni5CoSr0.75 catalyst was used

Effect of Calcination Temperature on Hydrogen Production via Ethanol Dry Reforming Over Ni/Al2O3 Catalyst

Ni/Al2O3 catalysts were prepared by the wet-impregnation method and calcined at different temperatures (500°C, 600°C and 700°C) to obtain NiAl-1, NiAl-2 and NiAl-3 respectively. NiAl-1, NiAl-2, NiAl-3 represent catalysts calcined at 500°C, 600°C and 700°C respectively. The catalysts were characterized using different techniques, XRD, BET and TGA. XRD results revealed the presence of NiO phase on all the catalysts during calcination, however, the presence of spinel, NiAl2O4, was more pronounced on the catalyst calcined at 600°C (i.e. NiAl-2), indicating the existence of strong metal-support interaction. BET results showed that NiAl-1 has the highest surface area of about 190cm2/g.  All the catalysts were tested for ethanol dry reforming in a tubular stainless steel fixed-bed reactor at 700°C and CO2/ethanol ratio of 3 under atmospheric pressure and were evaluated in terms of reactants conversion and selectivity of H2 to see the effect of the different calcination temperatures on the catalysts’ activities. Ethanol conversion was 100% for all the three catalysts and NiAl-2 has the highest CO2 conversion with an average value of about 57%. The three catalysts have almost the same performance in terms of H2 selectivity. The presence of multi-walled carbon nanofibers (MWCNFs) were confirmed on all the catalysts as revealed by the TGA result. The catalyst calcined at 600°C (i.e. NiAl-2) displayed the best relative catalytic activit

Effect of Calcination Temperature on Morphological and Topography of Nickel-Alumina Thin Film

Dip coating process promises good potential of nickel-alumina catalyst deposition on metal substrate for various applications especially in gas conversion reaction. This study was conducted to investigate the effect of different calcination temperature on nickel-alumina catalysts thin film formation. Four different calcination temperature were used, which are 300°C, 400°C, 500°C and 600°C. The calculation process was conducted for a duration of 90 minutes. The deposited thin films were characterized using Atomic Force Microscopy (AFM) and X-ray diffraction (XRD) equipment. The AFM result showed that the surface roughness of the nickel-alumina increase proportionally from 56 to 275 nm when the calcination temperature increased from 300 to 600°C. From an observation at high calcination temperature, the atom of grains assisted diffusion at the crystallite point causing grain with lower surface energy become larger. As the calcination temperature increase, the surface profile becomes rough and uneven representing high surface roughness. Thus, the effect of calcination temperature greatly influences the surface roughness of the nickel-alumina thin film

Temperature-induced modifications in natural zeolite clinoptilolite: effects on acidity and catalytic acetalization

This study delves into the acid modification of natural zeolite clinoptilolite, focusing on the identification of acid site types and their catalytic activity in the Brønsted acid-catalyzed acetalization of benzaldehyde with 1,3-butanediol. Following calcination, the samples underwent acidification via ammonium-ion exchange, resulting in approximately 45 % of the clinoptilolite cations being exchanged with ammonium ions. The investigation evaluates the structural, morphological, and textural alterations induced by this modification using XRD, FTIR, and nitrogen adsorption-desorption measurements. Ammonia-temperature-programmed desorption (NH3-TPD) analysis confirms the presence of medium to strong acidic protons, highlighting the acidity of the modified samples. Employing 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy elucidated changes in the state and coordination of aluminum post-sample activation. Specifically, the 27Al MAS NMR spectra indicate a partial dealumination, evidenced by the emergence of 5 and 6-fold coordinated aluminum. Moreover, 29Si MAS NMR measurements tracked variations in the Si/Al ratio. The study probes the nature of these sites, their influence on catalytic activity, and the synergistic interplay between Brønsted acid sites and 5-fold coordinated aluminum. The results showcase that the prepared acidic natural clinoptilolite catalysts augment acidity and porosity, fostering promising implications for catalytic applications.<br/