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Ammonia made with hydrogen from sustainable wind energy can be separated from unreacted hydrogen and nitrogen by absorption in magnesium chloride. The absorption is rapid, but desorption can be slo...

Metal halide salts such as magnesium chloride have been demonstrated to be promising candidates for ammonia storage materials for energy storage and agriculture applications due to their ability to...

Inteins are auto-processing domains that implement a multi-step biochemical reaction termed protein splicing, marked by cleavage and formation of peptide bonds. They excise from a precursor protein, generating a functional protein via covalent bonding of flanking exteins. We report the kinetic study of splicing and cleavage reaction in [Fe-S] cluster assembly protein SufB from Mycobacterium tuberculosis. Although it follows a canonical intein splicing pathway, distinct features are added by extein residues present in the active site. Sequence analysis identified two conserved histidines in the N-extein region; His-5 and His-38. Kinetic analyses of His-5Ala and His-38Ala SufB mutants exhibited significant reductions in splicing and cleavage rates relative to the SufB wild-type precursor protein. Structural analysis and molecular dynamics simulations suggested that Mtu SufB displays a unique mechanism where two remote histidines work concurrently to facilitate N-terminal cleavage reaction. His-38 is stabilized by the solvent-exposed His-5, and can impact N-S acyl shift by direct interaction with the catalytic Cys1. Development of inteins as biotechnological tools or as pathogen specific novel antimicrobial targets requires a more complete understanding of such unexpected roles of conserved extein residues in protein splicing.

Ammonia is made by combining nitrogen and hydrogen at high pressure. In the conventional process on the left, these gases are partially reacted at about 400 °C, and ammonia is recovered by condensa...

Biomass briquettes are expanding its reach from domestic stoves to giant power plants. This study aims to evaluate the effect of compositional heterogeneity of bagasse and groundnut shell briquettes on slow pyrolysis kinetics, fast pyrolysis product distribution and time evolution of pyrolysates. The average apparent activation energy of pyrolysis was low for 0.71–1.4 mm particles of bagasse (175.5 kJ mol−1) and 1.4–2 mm particles of groundnut shell (169.3 kJ mol−1). The production of phenolics, furan derivatives, monoaromatics and condensed ring aromatics exhibited marked changes with respect to particle size of biomass and temperature. The phenolic selectivity was more from large biomass particles. The production of aromatic hydrocarbons is correlated with the particle size of biomass, and the extent of secondary reactions is shown to be coupled with heat and mass transport of pyrolysates within the confined pores of the sample. The evolution rate of pyrolysis vapors increased with increasing temperature.

Lignocellulosic biomass and waste plastics are promising feedstocks for the production of liquid fuels via pyrolysis, which is a promising thermochemical conversion technique. The direct use of liquid bio-oil produced from biomass is restricted as it has high oxygen (28%–40%) and moisture (15%–30%) contents, is unstable due to its acidity (~ pH of 2.0–4.0), and possesses low calorific value (~ 20 MJ kg − 1 ). Copyrolysis of biomass with plastics is a potential technique to improve the quality of the bio-oil. Owing to the presence of hydrogen-rich polymers like polyethylene and polypropylene and aromatic polymers like polystyrene, significant interactions between biomass pyrolysis intermediates and polymer free radicals are expected. This promotes the quality of bio-oil in terms of better hydrogen-to-carbon and hydrogen-to-oxygen ratios, stability, and heating value. This chapter addresses the fundamentals of copyrolysis of lignocellulosic biomass and polymers by giving due importance to the recent literature on quality of copyrolysis bio-oil, optimum reaction conditions, role of catalysts, and product formation mechanisms.

In this study, the production of high quality biofuel intermediates via fast co-pyrolysis of cellulose and polypropylene (PP) is investigated. Fast co-pyrolysis experiments were performed in a Pyroprobe� reactor and the generated vapors were analyzed using a gas chromatograph-mass spectrometer for the composition of pyrolysates, and Fourier transform infrared spectrometer for the time evolution of the key functional groups. The effects of cellulose: PP mass ratio (100 : 0, 75 : 25, 50 : 50, 25 : 75, 0 : 100) and temperature (500-800 �C) on bio-oil composition, carbon number distribution of the products, higher heating value of the products, and temporal evolution of O-H, C-O, -CH2-, CO2 and C=O groups were evaluated. Formation of long chain alcohols in the carbon number range of C8-C20 was observed as a result of the interaction of cellulose and PP. Feed composition played a decisive role in the formation of alcohols and hydrocarbons. A maximum of ca. 36% alcohols and 45% hydrocarbons were obtained from PP-rich mixture at 600 �C. The yield of char decreased and that of the aromatic hydrocarbons increased with pyrolysis temperature. Significant improvement in the heating value of the products was observed when PP was blended with cellulose. Importantly, the calculated heating values correlated well with the cumulative content of alcohols, aliphatic and aromatic hydrocarbons. The addition of PP to cellulose significantly decreased the time taken for completion of pyrolysis. Based on the product distribution, hydroxyl, hydrogen and methyl abstraction were found to be the dominant reactions involved in the transformations. � The Royal Society of Chemistry.

In this study, the apparent kinetics of fast pyrolysis of alkali lignin was evaluated by obtaining isothermal mass loss data in the timescale of 2-30s at 400-700°C in an analytical pyrolyzer. The data were analyzed using different reaction models to determine the rate constants and apparent rate parameters. First order and one dimensional diffusion models resulted in good fits with experimental data with apparent activation energy of 23kJmol-1. Kinetic compensation effect was established using a large number of kinetic parameters reported in the literature for pyrolysis of different lignins. The time evolution of the major functional groups in the pyrolysate was analyzed using in situ Fourier transform infrared spectroscopy. Maximum production of the volatiles occurred around 10-12s. A clear transformation of guaiacols to phenol, catechol and their derivatives, and aromatic hydrocarbons was observed with increasing temperature. The plausible reaction steps involved in various transformations are discussed.

The present research work focuses on understanding the kinetics and mechanism of co-pyrolysis of cellulose, a major constituent of biomass, and polypropylene (PP) that is abundantly present in waste plastics. Co-pyrolysis of cellulose and PP of different compositions, viz., 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 (mass%/mass%), was carried out in a thermogravimetric analyzer at various heating rates from 5 to 180 K min−1. The kinetics of slow to medium heating rate pyrolysis was analyzed using first Kissinger and Kissinger–Akahira–Sunose techniques. Cellulose and PP decomposition occurred in two distinct temperature regimes, viz., 575–650 and 675–775 K, respectively. However, apparent activation energies of thermal decomposition of the mixtures clearly indicated the presence of interaction between cellulose and PP. The presence of cellulose in the mixture decreased the apparent activation energy of PP decomposition from 210 to 120 kJ mol−1, while the presence of PP did not affect the apparent activation energy of cellulose decomposition (E a = 158 ± 3 kJ mol−1). A significant decrease in apparent activation energy was observed in the conversion regime corresponding to the completion of cellulose pyrolysis and beginning of PP pyrolysis. Differential scanning calorimetry data clearly showed the shift of exothermic char formation to higher temperatures with PP incorporation in the mixture. The presence of PP also resulted in reduction of final char content. Based on the above analyses, a new interaction step that involves a bimolecular reaction of activated PP with volatiles from cellulose pyrolysis to form interaction products and char is proposed, and the rate limiting steps for char formation are clearly identified.

Pyrolysis is a promising thermochemical conversion technique to recover valuable building blocks and chemicals from waste polymers. After outlining the need for recycling and comparing the various strategies for recycling polymer wastes, this article evaluates noncatalytic and catalytic pyrolysis of a number of common polymers by giving due emphasis to pyrolysis products and product formation pathways. Free radical, concerted, and acid-catalyzed mechanisms involved in noncatalytic and catalytic pyrolysis of vinyl polymers are discussed. The different types of analytic pyrolyzers and their applications are outlined. Polymer pyrolysis via microwave-assisted heating is evaluated for tuning of product yields and selectivities.

This study focuses on selective production of valuable chemicals from polystyrene (PS) via catalytic fast pyrolysis using micropyrolyzer-GC/MS set-up. Catalytic fast pyrolysis of PS was performed using eight different zeolites belonging to ZSM-5, zeolite-?, and zeolite-Y families. The catalysts were characterized for the strength of Br�nsted acid sites and pore size distribution. The composition of PS:catalyst was optimized at 1:2.3 � 0.2 wt./wt. to enhance the yield of benzene, at the same time reduce the yield of condensed ring fragments like indene and indane derivatives. The yields of various products correlated well with specific properties of zeolites like relative strength of Br�nsted acid sites, specific surface area, and pore volume. Importantly, the yield of benzene increased, while that of styrene, ?-methyl styrene, and dimers decreased with Br�nsted acidity. Zeolite-? hydrogen and zeolite-Y ammonia catalysts resulted in the formation of up to 50 wt.% of benzene. High temperatures led to a reduction in benzene yield and promoted the formation of styrene, ?-methyl styrene, and ethyl benzene. The observed product distribution with different zeolites and at different temperatures was corroborated using the relative importance of the primary protonation pathways involved in catalytic fast pyrolysis of PS. � 2015 Elsevier B.V.

Aged automobile engine oils contain highly oxidized and hazardous organic compounds, and their disposal adversely affects the environment, underground, and surface waters. Therefore, it is imperative to develop innovative strategies to solve the problem of disposal of waste engine oils. One way is to recover value added chemicals and intermediates from it. This study focuses on recovery of useful hydrocarbons from highly oxidized, waste motorbike engine oils via catalytic fast pyrolysis using zeolites belonging to ZSM-5, Zeolite-? and Zeolite-Y (ZY) families. Pyrolysis experiments were conducted in a micropyrolyzer connected to a gas chromatograph-mass spectrometer. Initially, non-catalytic fast pyrolysis was performed at temperatures from 300 to 800 �C, and it was found that high temperatures led to the formation of C3-10 alkenes, while low temperatures resulted in high yields of heavy fractions like C31-60 alkanes and oxidized aromatics. In order to selectively improve the production of C6-15 alkanes that are valuable as fuel molecules, catalytic fast pyrolysis was performed at 400 �C using 1:1 wt./wt. of oil:zeolites. Hydrogen form of ZY resulted in c.a. 65% of C6-15 linear, branched, and cyclic alkanes, while other catalysts promoted the formation of alkenes. The yields of C6-15 linear and cyclic alkanes increased with micropore area, pore volume, and surface acidity of the zeolites. An increase in catalyst quantity significantly increased the yield of C6-10 alkanes, while reducing the C11-15 alkane yield and promoting the formation of C3-5 alkanes. High temperatures led to a significant drop in the production of linear and branched alkanes, but promoted the formation of alkenes and cyclic hydrocarbons. This work has demonstrated that catalytic fast pyrolysis using zeolites is a potential technique to selectively recover value added hydrocarbons from highly oxidized engine oils. � 2015 Elsevier B.V. All rights reserved.