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Selectively cleaving the C O bonds in lignin to produce aromatic products are challenging problems. Currently, catalytic hydrogenolysis of C O bonds in lignin requires harsh conditions. Herein, selectively cleaving C O bond of benzyl phenyl ether (BPE) was studied over Pd/AC, Ru/AC and Ni/AC. Among these catalysts, Pd/AC efficiently cleaved C O bond in BPE under super mild conditions (25 °C, 2 h and 0.1 MPa H2). The products were toluene and phenol without hydrogenation of the aromatic ring. The main competitive step of hydrogenolysis and hydrogenation is sensitive to reaction temperature over Pd catalyst. A mild temperature is preferred for hydrogenolysis, since the H species nearby the oxygen atom are more strongly adsorbed than nearby the benzene rings. With the different H-donor solvents, the highest conversion of BPE was obtained in isopropanol. Based on the experiments, the reactions occurred via cleavage of the Caliphatic-O bond in BPE and the synergetic effects between the H from absorbed H2 on the surface of the Pd and the intermediates radicals of benzyl and phenoxy should be the key points to such an optimum result.

Waste sugar solution is harmful to the environment and abundant in organic waste, and waste sugar residue (WSR) was obtained by drying waste sugar solution. In order to efficiently solve this issue and created values, activated carbon was prepared by WSR with KOH as activation agent. Carbonization temperature, activation temperature, activation ratio and activation time were investigated, based on the effects of preparation conditions on the electrochemical performance of activated carbon. The electrode material shows superior electrochemical performance, especially when the activated carbon was prepared at the carbonization temperature of 600 °C, activation temperature of 700 °C, activation ratio of 3:1 (KOH:char) and activation time of 2.5 h. It possesses the optimal electrochemical performance with a specific capacitance of 273.31 F g − 1 and a specific surface area of 1953 m 2 g − 1 . In order to determine the electrochemical stability of activated carbon electrodes, the cycle lifetime was performed at a current density of 1.5 A g − 1 . After 5000 cycles, the capacitance retention rate of 90.1% could be obtained. Additionally, the energy density was relatively high at 1.5 A g − 1 (up to 5.09 Wh kg − 1 ). This study provides a value-added approach for WSR treatment and a potential feedstock for low cost-high performance activated carbons for electric double-layer capacitor.

This work is aimed to study in situ upgrading of Shengli lignite pyrolysis vapors over different metal-loaded HZSM-5 in a drop tube reactor. Co/HZSM-5, Mo/HZSM-5 and Ni/HZSM-5 (5.0 wt%) were prepared by wet impregnation and characterized by N 2 adsorption-desorption analyzer, X-ray diffraction, transmission electron microscope, Fourier transform infrared spectrometer and temperature programmed desorption of ammonia. The effects of temperature and catalyst on product yields and tar properties were investigated. The results show that the optimal temperature for liquid product was 600 °C and aromatics can be directly produced from solid lignite by catalytic fast pyrolysis over metal-loaded HZSM-5 under such mild condition. Due to the participation of metal and acid sites, the bifunctional metal-loaded HZSM-5 showed comparable catalytic activity for deoxygenation reaction in the valorization of oxygen content below 7.1%. The introduction of metal causes the increase of aromatics and the decrease of organic oxygen species in upgraded tar remarkably. Among the catalysts, Ni/HZSM-5 exhibited the best performance for production of high quality tars with highest aromatics content of 94.2% (area%), which can be used as a potential candidate for catalytic upgrading of pyrolysis oil.

Ni-encapsulated (Ni@HZ5) and Ni-incorporated (xNi/HZ5) zeolites were prepared via one-pot hydrothermal synthesis and impregnation method, respectively, and further employed for hydroconversion of pyrolytic volatiles of spent coffee grounds into benzene, toluene, ethylbenzene, xylene, naphthalene (BTEXN) in a drop tube reactor under H2 atmosphere. The properties of metallic Ni species on Ni@HZ5, xNi/HZ5 and Ni/Al2O3 were comparably characterized. Ni@HZ5 displayed superior selectivity for BTEXN production among those catalysts, especially for B and T. Metallic Ni species encapsulated MFI-type framework plays crucial roles in enhancing aromatics selectivity, promoting oligomerization, cyclization and aromatization of small molecular hydrocarbons in channels. On the contrary, Ni species presented on the external zeolite surface is in favor of hydrocracking and hydrogenolysis of macromolecular pyrolytic fragments. It also exhibited high coke content containing “soft” and “hard” coke, which was mainly caused by metallic particles sintering. An important difference was proposed in the effect of Ni species on reaction pathway for catalytic upgrading of volatiles to BTEXN. The configured Ni@HZ5 inhibits sintering and has potential of enhancing BTEXN by catalytic hydropyrolysis of biomass.

In the last few decades, the production of value-added chemicals from biomass has become a key research focus. Biomass gasification into syngas and further for methane, methanol, and C2+ alcohols production has already proved to be promising for utilization of renewable energy. Therefore, heterogeneous catalyst design and optimization are extremely significant for solving the issues of tar formation during biomass gasification. Apart from alkali metals, natural minerals, and synthetic catalysts, char and char supported catalysts prepared from residual biomass or coal have been already proved to be effective for tar reforming due to their relative chemical inertness, cheap price, excellent pore structures, etc. Advantageously, bio−/coal char could be modified and/or functionalized with heteroatoms doping and metal addition to improve activity in tar reforming. In this review, we systematically discussed the preparation, modification, and application of char catalysts in the reforming of biomass tar and tar model compounds. After that, we reviewed and compared the activity of char catalysts in tar reforming, and then we gave corresponding reactions and deactivation mechanisms over char catalysts in biomass tar reforming. Finally, we proposed existed challenges and shared our perspectives regarding future needs in char catalysts design for accelerating fuel sustainability and green development.

A novel catalyst was prepared by loading nickel on Shenli lignite char via ion-exchange. The results show that the nickel crystallite size (NCS) and specific surface area (SSA) of the catalyst significantly depended on solution pH and carbonization temperature. The catalyst prepared in pH 11 at 650 °C reached the maximum SSA of 236.3 m2/g and the nickel particles dispersed quite well in the catalyst with a NCS of 5.6 nm. The catalyst was used for corncob volatiles reforming in a two-stage fixed-bed reactor to study the effects of temperature, steam, and space velocity on gas yields and carbon distributions. It effectively improved tar decomposition at 650 °C under inert atmosphere and produced a tar-free syngas in a yield of 43.9 mmol/g, which is higher than that over a commercial Ni/Al2O3. The increase of the NCS during catalytic reforming above 650 °C leads to the catalyst deactivation for tar decomposition. The study revealed the possibility of using Ni/char as a potential catalyst for low-temperature gasification of biomass.

Electrical double layer capacitors (EDLCs) with HyperCoal-derived activated carbons (ACs) as electrodes are reported in this work. The ACs were prepared by the carbonization of HyperCoal at 600 °C followed by the activation with KOH and NaOH for 2 h between 500 and 800 °C to achieve high total pore volume (TPV) and specific surface area (SSA). The porosity of the ACs was characterized with N 2 adsorption at 77 K. The results show that the ACs prepared with KOH and NaOH activations at 700 °C have a SSA of 2594 and 3010 m 2 g − 1 and a TPV of 1.36 and 1.77 cm 3 g − 1 , respectively, leading to the highest specific capacitance of 43.1 and 43.9 F g − 1 , respectively, in a two-electrode EDLC cell with 0.5 M tetraethylammonium tetrafluoroborate/propylene carbonate (TEABF 4 /PC) electrolyte. Activations with CaCO 3 and KOH/CaCO 3 mixture were also investigated to understand the effect of CaCO 3 on the properties of the ACs. CaCO 3 significantly inhibited the porosity development during KOH activation and gave ACs with quite low SSA and specific capacitance. The results demonstrated that the alkaline hydroxide activation is an efficient approach to the preparation of ACs from HyperCoal with high-performance for EDLCs.

Low-temperature catalytic reforming of volatiles and nitrogen compounds from sewage sludge (SS) pyrolysis was performed in a two-stage fixed-bed reactor over Ni/Al2O3 under inert and steam-reforming conditions. The results show that the reforming of SS volatiles significantly depended on temperature, space velocity, steam partial pressure, and feedstock type. Catalytic cracking of SS volatiles at 650 °C under inert atmosphere produced a tar-free synthetic gas with a H2/CO ratio of 2:1 in a high yield, which is preferred for maximum conversion efficiency for methanol synthesis. Steam as the gasifying agent gave a H2-rich gas (H2 content 68.0 vol.%) with a high yield of 82.5 mmol · g-1 (daf) at 650 °C, while the H2 yield is twice as that from non-steam gasification. Ni/Al2O3 effectively improved tar reforming and showed great resistance to coke deposition in the presence of steam. NH3, HCN, and nitrogen in tar are the main volatile nitrogen species in SS pyrolysis. Almost all the NOx precursors were converted to N2 by catalytic reforming at 650 °C both in the presence and absence of steam. Such an approach may lead to the development of a clean SS utilization technology and also H2/synthetic gas production technology from SS.

The synergistic catalysis in the catalytic hydrogenolysis (CH) of lignin and its model compounds over a Ni-Ru/AC bimetallic surface was well established. The Ni-Ru/AC exhibits excellent activity and stability for catalytic hydrogenolysis of lignin and its model compound. The additions of Ru into supported Ni/AC can not only improve the overall reactants conversion, but also modify the product distribution. The apparent activation energy (Ea) of BPE hydrogenolysis over Ni-Ru/AC is measured approximately to be 18.3 kJ/mol. This value is considerably lower than the values measured for monometallic Ni/AC (42.4 kJ/mol). Additionally, the turnover frequency (TOF) of Ni-Ru/AC (62.7 h−1) was much higher than that of Ni/AC (5.1 h−1). In case of CH of lignin, Ni-Ru/AC gave better total liquid yield and higher relative content of main aromatic monomers. The enhancement in the overall hydrogenolysis activity of reactants over bimetallic Ni-Ru/AC is related to the synergistic effect of Ni and Ru. Various characterization methods (XRD, XPS, TEM-EDS, SEM-EDX and BET) are performed to elucidate the formation of synergistic effect. This synergistic effect could originate from the generation of additional surface active sites, small size of metal particles and high dispersion of metal particles.

Catalytic hydrodenitrogenation (HDN) of isoquinoline (IQ) over Ni or Pd/C was studied at 200 °C and 300 °C under pressurized hydrogen. Two pathways of the HDN of IQ over Ni or Pd/C at 200 °C were found: one from saturated derivatives to ring-opened products (ROPs) and another from hydroaromatic derivatives to ROPs. Thirty five kinds of addition products (APs) were identified in the reaction mixtures and most of the APs seemed to be substituted on nitrogen atom. Compared to Ni, Pd/C-catalyzed reactions of IQ yielded more APs, especially at 300 °C.