• Energy Research
• natural sciences close

In this study, biochar was prepared via hybrid doping of N, O, and S by applying one-pot pyrolysis of poplar wood and S-containing urea formaldehyde at 900 °C. Different doping ratios were adopted, and the contents of O, N, and S were in the ranges of 2.78–5.56%, 2.16–4.92%, and 1.42–4.98%, respectively. This hybrid doping significantly enhanced the efficiency of the removal of tetracycline (40 mg/L) from wastewater to 71.84% in comparison with that attained by using normal poplar biochar (29.45%). The adsorption kinetics and isotherms indicated that the adsorption process was favorable and was dominated by chemisorption instead of physisorption; the dominant adsorption process may be justified by the existence of abundant functional groups. The adsorption capacity was barely related to the surface area (R2 = 0.478), while it was closely related to the concentration of graphitic N (R2 = 0.985) because graphitic N enhanced the π–π interactions. The adsorption capacity was also highly related to the proportion of oxidized N and oxidized S owing to hydrogen bonding, which may have overlapped with the contribution of O-containing functional groups. This study presents a simple hybrid doping method for biochar modification and provides fundamental insights into the specific effects of O-, N- and S-containing functional groups on the performance of biochar for tetracycline removal.

Distinct crystal phases of an oxide affect the configuration of surface atoms, which might further affect coordination with sulfate during sulfonation for the preparation of SO42−/MxOy type of acid catalyst. Herein, such an effect is investigated with zirconia of the tetragonal or monoclinic phase as the model catalysts. The results show that sulfonation inhibits the transformation of zirconia from the tetragonal phase to the monoclinic phase, whereas the varied phase of zirconia also affects the bonding patterns of sulfate species with zirconia in sulfonation. The sulfated zirconia of monoclinic phase contains more abundant acidic sites and more Brønsted acid sites than that of sulfated zirconia of tetragonal phase. Consequently, the sulfated zirconia of monoclinic phase is more active than the sulfated zirconia of tetragonal phase for the conversion of furfuryl alcohol in ethanol and conversion of fructose in dimethyl sulfoxide, achieving the yield of ethyl levulinate of 96.4% and a high yield of 5‐hydroxymethylfurfural. The sulfated zirconia is not stable in protic solvent due to the leaching of sulfur species and the change in configurations of the sulfate species and the zirconium species, but in the aprotic solvent, they show good stability and recyclability.

Abstract The impregnation of sulfuric acid aqueous solution to silica is a traditional method to prepare the solid acid catalyst (SO42−/SiO2) via bonding of the SO42− with surface atoms of silica to generate Bronsted acidic sites and Lewis acidic sites. The results in this study indicated the introduction of sulfuric acid could also impact the interaction between silica and subsequently loaded nickel species. The impregnation of sulfuric acid (i.e. 0.5 M) to Ni/SiO2 catalyst could enhance the dispersion of nickel via reducing nickel particle size, suppress sintering of nickel and increase abundance of the acidic sites with strong strength, which significantly enhanced the catalytic activity, stability and resistivity towards coking in steam reforming of guaiacol. The acidic sites with the strong strength aided the cracking of guaiacol to facilitate the subsequent reforming over metallic nickel sites. After impregnation of appropriate amount of sulfuric acid (i.e. 0.1 M or 0.5 M), the coke formed in amorphous form with low thermal stability was transformed into the coke in form of carbon nanotube with high thermal stability. The former type of coke induced rapid deactivation of the catalyst, while the latter type of coke did not.

It has been reported that a deoxygenated bio-oil (ca. 0.12 kg kg−1 O on bio-oil basis) can be obtained simply by recycling the non-condensable gases (NCG) of biomass fast pyrolysis to a fluidized-bed reactor operated at atmospheric pressure [Mullen et al., 2013, Energy Fuels, 27, 3867–3874]. Such an unprecedented effect would (i) complicate the use of lab-scale research results obtained typically under inert gas (N2, He, Ar) atmosphere for the design of commercial scale pyrolysis units projected to utilize a recycle gas atmosphere (ii) obviate the need for catalytic pyrolysis or mild hydrotreatment processes. Considering these implications, further validation or refutation of the claimed deoxygenation effect of recycle gas atmosphere is needed. Therefore, fast pyrolysis experiments with pine wood were performed in a bench-scale fluidized bed reactor under N2 atmosphere, recycle gas atmospheres (75 % and 90 % recycle gas volume fraction) at reactor temperatures of 430 °C and 500 °C. Mass balances were obtained and the bio-oils were analyzed using GC/MS, GPC, elemental analysis and Karl Fischer titration. No significant differences were observed in product yield and bio-oil composition (e.g. oxygen content) when going from a nitrogen gas atmosphere to a recycle gas atmosphere for both pyrolysis temperatures.

Ultrasmall Ru nanoparticles is expected as a potential alternative to Pt for efficient hydrazine oxidation (HzOR). However, preparation of ultrasmall and well-distributed Ru nanoparticles usually suffered from the steps of modification of supports, coordination, reduction with strong reducing reagents (e.g., NaBH4) or pyrolysis, imposing the complexity. Based on the self-reducibility of C-OH group and physical adsorption ability of commercial Ketjen black (KB), we developed an efficient, stable and robust Ru-based electrocatalyst (A-Ru-KB) by coupling impregnation of KB in RuCl3 solution and simple in situ electrochemical activation strategy, which endowed the formation of ultrasmall and well-distributed Ru nanoparticles. Benefiting from an enhanced exposure of Ru sites and the faster mass transport, A-Ru-KB achieved 63.4 and 3.9-fold enhancements of mass activity compared with Pt/C and Ru/C, respectively, accompanied by a ∼144 mV lower onset potential and faster catalytic kinetics than Pt/C. In the hydrazine fuel cell, the open-circuit voltage and maximal mass power density of A-Ru-KB was 130 mV and ∼3.8-fold higher than those of Pt/C, respectively, together with the long-term stability. This work would provide a facile and sustainable approach for large-scale production of other robust metal (electro)catalysts with ultrasmall nanosize for various energy conversion and electrochemical organic synthesis.

Avec le développement et la prospérité de l'économie mondiale, les émissions de dioxyde de carbone (CO2) sont devenues une préoccupation croissante. Son effet de serre causera de graves problèmes environnementaux, tels que le réchauffement climatique et le changement climatique. Par conséquent, les scientifiques du monde entier ont consacré de grands efforts à contrôler les émissions de CO2 par le biais de diverses stratégies, telles que le captage, l'utilisation des ressources, la séquestration, etc. Parmi ceux-ci, la conversion catalytique du CO2 en méthane est considérée comme l'une des voies les plus efficaces pour l'utilisation des ressources en CO2 en raison des conditions de réaction douces et du dispositif de réaction simple. Des études thermodynamiques pionnières ont révélé qu'une faible température de réaction est bénéfique pour l'activité catalytique élevée et la sélectivité en CH4. Cependant, la basse température sera défavorable à l'augmentation de la vitesse de réaction due à la barrière cinétique pour l'activation du CO2. Par conséquent, l'invention de catalyseurs très efficaces avec des activités à basse température prometteuses pour la réaction de méthanation du CO2 est la solution clé. Les catalyseurs à base de Ni ont été largement étudiés en tant que catalyseurs de méthanation du CO2 en raison de leur faible coût et de leurs excellentes performances catalytiques. Cependant, les catalyseurs à base de Ni effectuent généralement des activités et des stabilités à basse température médiocres. Par conséquent, le développement de catalyseurs à base de Ni très efficaces avec d'excellentes performances catalytiques à basse température est devenu l'objectif de recherche ainsi que le défi dans ce domaine. Par conséquent, nous avons résumé les progrès de la recherche récente sur la construction de catalyseurs à base de Ni très efficaces pour la méthanation du CO2 dans cette revue. Plus précisément, les stratégies sur la façon d'améliorer les performances catalytiques des catalyseurs à base de Ni ont été soigneusement examinées, qui comprennent divers facteurs d'influence, tels que les supports catalytiques, les auxiliaires catalytiques et les dopants, les méthodes de fabrication, les conditions de réaction, etc. Enfin, la tendance future du développement des catalyseurs à base de Ni est également prospectée, ce qui sera utile pour la conception et la fabrication des catalyseurs Ni avec une grande efficacité vers le processus de méthanation du CO2. Con el desarrollo y la prosperidad de la economía mundial, la emisión de dióxido de carbono (CO2) se ha convertido en una preocupación creciente. Su efecto invernadero causará graves problemas ambientales, como el calentamiento global y el cambio climático. Por lo tanto, los científicos de todo el mundo han dedicado grandes esfuerzos a controlar las emisiones de CO2 a través de diversas estrategias, como la captura, la utilización de recursos, el secuestro, etc. Entre estos, la conversión catalítica de CO2 en metano se considera una de las rutas más eficientes para la utilización de recursos de CO2 debido a las condiciones de reacción suaves y el dispositivo de reacción simple. Los estudios termodinámicos pioneros han revelado que la baja temperatura de reacción es beneficiosa para la alta actividad catalítica y la selectividad de CH4. Sin embargo, la baja temperatura será adversa a la mejora de la velocidad de reacción debido a la barrera cinética para la activación de CO2. Por lo tanto, la invención de catalizadores altamente eficientes con actividades prometedoras a baja temperatura hacia la reacción de metanización de CO2 es la solución clave. Los catalizadores a base de Ni han sido ampliamente investigados como catalizadores hacia la metanización de CO2 debido a su bajo coste y excelentes rendimientos catalíticos. Sin embargo, los catalizadores a base de Ni generalmente realizan actividades y estabilidades deficientes a baja temperatura. Por lo tanto, el desarrollo de catalizadores a base de Ni altamente eficientes con excelentes rendimientos catalíticos a baja temperatura se ha convertido en el foco de investigación, así como en un desafío en este campo. Por lo tanto, resumimos los avances recientes en la investigación de la construcción de catalizadores a base de Ni altamente eficientes hacia la metanización de CO2 en esta revisión. Específicamente, se han revisado cuidadosamente las estrategias sobre cómo mejorar los rendimientos catalíticos de los catalizadores a base de Ni, que incluyen diversos factores de influencia, como soportes catalíticos, auxiliares catalíticos y dopantes, los métodos de fabricación, las condiciones de reacción, etc. Finalmente, también se prosigue la tendencia de desarrollo futuro de los catalizadores a base de Ni, lo que será útil para el diseño y la fabricación de los catalizadores de Ni con alta eficiencia hacia el proceso de metanización de CO2. With the development and prosperity of the global economy, the emission of carbon dioxide (CO2) has become an increasing concern. Its greenhouse effect will cause serious environmental problems, such as the global warming and climate change. Therefore, the worldwide scientists have devoted great efforts to control CO2 emissions through various strategies, such as capture, resource utilization, sequestration, etc. Among these, the catalytic conversion of CO2 to methane is considered as one of the most efficient routes for resource utilization of CO2 owing to the mild reaction conditions and simple reaction device. Pioneer thermodynamic studies have revealed that low reaction temperature is beneficial to the high catalytic activity and CH4 selectivity. However, the low temperature will be adverse to the enhancement of the reaction rate due to kinetic barrier for the activation of CO2. Therefore, the invention of highly efficient catalysts with promising low temperature activities toward CO2 methanation reaction is the key solution. The Ni based catalysts have been widely investigated as the catalysts toward CO2 methanation due to their low cost and excellent catalytic performances. However, the Ni based catalysts usually perform poor low-temperature activities and stabilities. Therefore, the development of highly efficient Ni based catalysts with excellent low-temperature catalytic performances has become the research focus as well as challenge in this field. Therefore, we summarized the recent research progresses of constructing highly efficient Ni based catalysts toward CO2 methanation in this review. Specifically, the strategies on how to enhance the catalytic performances of the Ni based catalysts have been carefully reviewed, which include various influencing factors, such as catalytic supports, catalytic auxiliaries and dopants, the fabrication methods, reaction conditions, etc. Finally, the future development trend of the Ni based catalysts is also prospected, which will be helpful to the design and fabrication of the Ni catalysts with high efficiency toward CO2 methanation process. مع تطور الاقتصاد العالمي وازدهاره، أصبح انبعاث ثاني أكسيد الكربون (CO2) مصدر قلق متزايد. سيؤدي تأثير الاحتباس الحراري إلى مشاكل بيئية خطيرة، مثل الاحترار العالمي وتغير المناخ. لذلك، كرس العلماء في جميع أنحاء العالم جهودًا كبيرة للتحكم في انبعاثات ثاني أكسيد الكربون من خلال استراتيجيات مختلفة، مثل الالتقاط واستخدام الموارد والاحتجاز وما إلى ذلك. من بين هذه الطرق، يعتبر التحويل الحفاز لثاني أكسيد الكربون إلى الميثان أحد أكثر الطرق كفاءة لاستخدام الموارد لثاني أكسيد الكربون بسبب ظروف التفاعل المعتدل وجهاز التفاعل البسيط. كشفت الدراسات الديناميكية الحرارية الرائدة أن درجة حرارة التفاعل المنخفضة مفيدة للنشاط التحفيزي العالي وانتقائية الميثان. ومع ذلك، فإن درجة الحرارة المنخفضة ستكون ضارة بتعزيز معدل التفاعل بسبب الحاجز الحركي لتنشيط ثاني أكسيد الكربون. لذلك، فإن اختراع محفزات عالية الكفاءة مع أنشطة واعدة في درجات الحرارة المنخفضة تجاه تفاعل ميثان ثاني أكسيد الكربون هو الحل الرئيسي. تم التحقيق على نطاق واسع في المحفزات القائمة على النيكل كمحفزات نحو ميثنة ثاني أكسيد الكربون بسبب تكلفتها المنخفضة وأدائها التحفيزي الممتاز. ومع ذلك، عادة ما تؤدي المحفزات القائمة على النيكل أنشطة وثباتات ضعيفة في درجات الحرارة المنخفضة. لذلك، أصبح تطوير محفزات عالية الكفاءة تعتمد على النيكل مع أداء تحفيزي ممتاز في درجات الحرارة المنخفضة محور البحث بالإضافة إلى التحدي في هذا المجال. لذلك، قمنا بتلخيص التقدم البحثي الأخير لبناء محفزات عالية الكفاءة قائمة على النيكل نحو ميثان ثاني أكسيد الكربون في هذه المراجعة. على وجه التحديد، تمت مراجعة الاستراتيجيات المتعلقة بكيفية تعزيز الأداء التحفيزي للمحفزات القائمة على النيكل بعناية، والتي تشمل عوامل مؤثرة مختلفة، مثل الدعامات الحفازة، والمساعدات الحفازة والمنشطات، وطرق التصنيع، وظروف التفاعل، وما إلى ذلك. أخيرًا، من المتوقع أيضًا اتجاه التطوير المستقبلي للمحفزات القائمة على النيكل، والذي سيكون مفيدًا لتصميم وتصنيع محفزات النيكل بكفاءة عالية نحو عملية ميثان ثاني أكسيد الكربون.

Characterization of organic compounds leached from biochars is essential in assessing the possible toxicity of the biochar to the soils' biota. In this study the nature of the leached organic compounds from Mallee biochars, produced from pyrolysis of Mallee leaf and bark in a fluidised-bed pyrolyser at 400 and 580°C was investigated. Light bio-oil compounds and aromatic organic compounds were investigated. The 'bio-oil like' light compounds from leaf and bark biochars 'surfaces were obtained after leaching the chars with a solvent, suitable to dissolve the respective bio-oils. GC/MS was implemented to investigate the leachates. Phenolics, which are potentially harmful toxins, were detected and their concentration shown to be dependent on the char's origin and the char production temperature. Further, to simulate biochars amendment to soils, the chars were leached with water. The water-leached aromatic compounds from leaf and bark biochars were characterized using UV-fluorescence spectroscopy. Those results suggested that biochars contain leachable compounds of which the nature and amount is dependent on the biomass feedstock, pyrolysis temperature and leaching time.