Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

http://ucce.ucdavis.edu/files/datastore/234-1388.pdf

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

Production of bioethanol from lignocellulosic materials via the biochemical pathway: a review.

We present a scalable wet chemical synthesis for a catalytically active nanostructured amorphous molybdenum sulfide material. The catalyst film is one of the most active nonprecious metal materials for electrochemical hydrogen evolution, drawing 10 mA/cm2 at ∼200 mV overpotential. To identify the active phase of the material, we perform X-ray photoelectron spectroscopy after testing under a variety of conditions. As deposited, the catalyst resembles amorphous MoS3, but domains resembling MoS2 in composition and chemical state are created under reaction conditions and may contribute to this material’s high electrochemical activity. The activity scales with electrochemically active surface area, suggesting that the rough, nanostructured catalyst morphology also contributes substantially to the film’s high activity. Electrochemical stability tests indicate that the catalyst remains highly active throughout prolonged operation. The overpotential required to attain a current density of 10 mA/cm2 increases by o...

Amorphous Molybdenum Sulfide Catalysts for Electrochemical Hydrogen Production: Insights into the Origin of their Catalytic Activity

Alternatives for detoxification of diluted-acid lignocellulosic hydrolyzates for use in fermentative processes: a review

Alternatives to petroleum-derived fuels and chemicals are being sought in an effort to improve air quality and increase energy security through development of novel technologies for the production of synthetic fuels and chemicals using renewable energy sources such as biomass. In this context, ethanol is being considered as a potential alternative synthetic fuel to be used in automobiles or as a potential source of hydrogen for fuel cells as it can be produced from biomass. Renewable ethanol can also serve as a feedstock for the synthesis of a variety of industrial chemicals and polymers. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, especially those containing six carbons, whereas 5-carbon sugars and lignin, which are also present in the biomass, remain unusable. Gasification of biomass to syngas (CO + H2), followed by catalytic conversion of syngas, could produce ethanol in large quantities. However, the catalytic conversion of syngas to ethanol remains challenging,...

A Review of Recent Literature to Search for an Efficient Catalytic Process for the Conversion of Syngas to Ethanol

Ethanol can be produced from renewable lignocellulosic materials such as various types of natural woods. The cellulose contents of wood can be converted to ethanol in a two-step process where acid-hydrolysis converts cellulose to glucose sugars by hydrolysis (saccharification) and the resulting sugars can be converted to ethanol by fermentation. The main challenge of producing fuel ethanol from renewable lignocellulosic biomass through acid-hydrolysis and fermentation is overcoming the cost-limiting factors associated with various stages of this technology. In this study, sugar recovery rates from a mixture of wood chips were investigated through three sets of acid-hydrolysis experiments. Wood chips were sorted to include equal ratios (by weight) of softwood and hardwood. Acid concentration and the heating period were the two main factors affecting dextrose yields. It was found that with the use of 26% by weight sulfuric acid, highest dextrose yields could be reached within 2 h of heating time. This corresponds to overall conversion efficiency of mixed wood chip cellulose to dextrose in the range of 78–82% based on theoretical values.

Optimizing acid-hydrolysis: a critical step for production of ethanol from mixed wood chips

Coastal management in the Persian Gulf region within the framework of the ROPME programme of action

Supported K2CO3/Co–MoS2 on activated carbon was prepared by a co-impregnation technique and has been characterized by X-ray diffraction (XRD) and BET. Active ingredients ranged from 39 to 66% and included molysulfide and cobalt sulfide. XRD analysis indicates that cobalt and molybdenum sulfides are found in the Co3S4 and Co9S8 phases. These catalysts were performance tested in a fixed-bed reactor under higher alcohol synthesis conditions, 2000–2400 psig and 270–330 °C. Active chemicals on the carbon extrudates decreased the surface area dramatically, as measured by BET. Surprisingly, at the high level of active chemicals, alcohol productivity and selectivity were decreased. An increase in the reaction temperature led to a decrease in the selectivity of methanol and an increase in selectivity of hydrocarbons. Total alcohol productivity was also increased as gas hourly space velocity (GHSV) was increased. Co9S8 may play a role in the catalyst aging process. In prolonged reaction periods (140 h), sulfur is lost from the surface, possibly as H2S. The quantity of Co9S8 on the surface appears to increase as the catalyst ages.

Alcohol synthesis from syngas over K2CO3/CoS/MoS2 on activated carbon

Amorphous MoS3 (air-dried precipitate), crystalline MoS2 (made in the laboratory under nitrogenous atmosphere), and commercial molybdenum disulfide catalysts have been investigated by X-ray photoelectron spectroscopy (XPS). The chemical species present on the surface and the S/Mo atomic ratios of laboratory catalysts were compared to those present on a commercial molybdenum disulfide catalyst before and after treatment with CO and H2. Pretreatment of MoS2 with CO followed by H2 showed that CO was adsorbed on the surface with no change in the chemical oxidation state of Mo and S. However, the results indicated that CO was not adsorbed when the sequence of gas exposures was reversed.

Jamshid Iranmahboob

Papers

Optimizing acid-hydrolysis: a critical step for production of ethanol from mixed wood chips

Coastal management in the Persian Gulf region within the framework of the ROPME programme of action

Alcohol synthesis from syngas over K2CO3/CoS/MoS2 on activated carbon

XPS study of molybdenum sulfide catalyst exposed to CO and H2

The influence of clay on K2CO3/Co-MoS2 catalyst in the production of higher alcohol fuel