Veena Bansal

Evaluation of recalcitrant features impacting enzymatic saccharification of diverse agricultural residues treated by steam explosion and dilute acid

Exploring agricultural biomass for biofuel production necessitates pretreatment as a prerequisite step. However, due the variability in recalcitrance among biomasses, choosing an optimum pretreatment methodology suitable for multiple feedstocks is challenging. To assess which parameters of pretreated biomass may serve as useful indicators of potential subsequent enzymatic saccharification, an insight into the structural alteration during pretreatment and its impact on the downstream process is essential. In this study, two pretreatment methods, dilute acid (DA) and steam explosion (SE) have been employed on three different biomasses viz. rice straw (RS), cotton stalk (CS) and mustard stalk (MS). The alteration in recalcitrant features of the pretreated residues was measured by chemical analysis, XRD, BET and FT-IR. FT-IR proved useful to measure the cellulose related properties viz. lateral order index (LOI) and hydrogen bond index (HBI) besides lignin related features, i.e. cross-linked lignin (CLL), lignin/cellulose (L/C) and syringyl/guaiacyl (S/G) ratio. The results show that S/G ratio, specific surface area and HBI of the pretreated residues had a positive correlation with enzymatic saccharification across different biomasses and pretreatment methodologies employed. On the other hand, lignin content, CLL, L/C ratio and LOI showed a negative correlation. However, the extent of xylan removal showed a positive correlation with the enzymatic saccharification only when a single pretreatment method was applied to different biomasses. The structure-activity correlation presented here would help to assess and predict the enzymatic saccharification while applying DA or SE pretreatment methods on different biomasses. This correlation could provide assistance in designing an optimum technology.

Structural Aspects of Crude Oil Derived Asphaltenes by NMR and XRD and Spectroscopic Techniques

Abstract Asphaltene samples obtained from crude processed at two Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (NMR), X-ray diffractometry (XRD), fluorescence spectroscopic techniques, and chromatographic (column and GPC) techniques. Estimation of NMR average structural parameters were obtained by combined 1H, NMR 13C, NMR DEPT-45, and QUAT pulse sequence spectral editing techniques. The macrostructure and crystalline parameters of these samples were obtained by XRD. The nature of the functional groups have been obtained by IR technique. A combined NMR and XRD parameters were used to estimate the size of average aromatic structural units. Asphaltenes from one of the crudes (ASP-A) was found to be highly pericondensed, highly substituted, and higher molecular size compared to ASP-B asphaltene molecules. The number of aromatic sheets per unit sheets are 3.7 and 2.5 in the sample ASP-A and ASP-B, respectively. Both the asphaltene molecules in the samples have periodically and systematic arrangement of aromatic sheets in the unit sheet. The number of aromatic rings per unit sheet in ASP-A and ASP-B are 6.0 and 5.0, respectively. The fluorescence spectral studies has also exhibited λ max (the wavelength of maximum intensity) at 505 and 509 nm confirming to pericondensed higher polycondensed aromatic ring system in both the samples. The analysis of liquid chromatographic fractions of these samples show that each sample is composed of several polycondensed aromatic systems where unit sheet of ring sizes vary from 1.8 to 6.3 with varying molecular sizes. These structural parameters allowed a model structure of the asphaltenes to be constructed.

A 1H NMR method for the estimation of hydrogen content for all petroleum products

AbstractBackgroundHydrogen content is an important parameter for all petroleum products, because the performance of the products for specific application depends on the concentration of hydrogen in it. Further, hydrogen content can be used as a measure for quality control during the production process and assess the quality of the products, which is governed by the catalyst used. Therefore, to get the desired petroleum products like MS and HSD, pilot scale evaluation of different catalysts plays an important role in problem solving during troubleshooting in refineries. During evaluation studies the performance of catalyst depends upon the hydrogen consumption and mass balance in any catalytic process. In order to calculate total hydrogen consumption during production of different petroleum products an effort has been made to develop a universal method based on nuclear magnetic resonance (NMR) technique, that allows estimating hydrogen content in all petroleum fractions, ranging from IBP to 530+ °C.MethodsThe method uses hexamethyldisiloxane (HMDSO) for the first time as a quantitative reference standard respect to which the H content of unknown samples has been estimated. The newly developed method can also determine H/C and O/C ratio of ethanol blended fuel in a given sample without any additional experimentation.ResultsHydrogen content for twenty five model compounds was determined along with nearly hundred petroleum fractions. There has been found to be good correlation between the existing ASTM D5291 and developed NMR spectroscopic based methods. For low boiling petroleum fractions, where ASTM D5291 is not suitable, there is no direct way to correlate the data. However, as the hydrogen content estimated for some model compounds shows a high degree of correlation R2 = 0.998, between theoretical values and estimated values, indirectly validate the developed method.ConclusionsA universal NMR based method for the estimation of hydrogen content in all sort of petroleum products irrespective of their origin, composition, boiling range has been developed. Graphical AbstractH-Content of petroleum products:1H NMR vs. ASTD D5291 combustion method.

Molecular Dynamics of Synthetic-Based Lubricant System by Spectroscopic Techniques—Part 1

This article describes the structure–property relationships of synthetic pentaerythritol polyol esters (PEE) and polyalphaolefins (PAO) as established by the diffusion and mobility measurement and tilt angle results obtained by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic techniques, respectively. The diffusion coefficients (D) were found to be dependent on the molecular structure, alkyl chain length, shape and size, hydrodynamic volume, and alignment of the molecules in a lubricant system constituting these base stocks. The viscosity–temperature and viscosity–pressure properties such as viscosity index (VI), pour point (PP), elastohydrodynamic (EHD) film thickness, pressure–viscosity coefficient (α), hydrodynamic volume, and radius are explained on the basis of the variation in D with temperature and tilt angle on the smooth surfaces. The study has enabled us to propose a molecular structure of a synthetic molecule that can be molecularly engineered to have high-performance physicochemical properties.

Detailed characterization of bio-oil from pyrolysis of non-edible seed-cakes by Fourier Transform Infrared Spectroscopy (FTIR) and gas chromatography mass spectrometry (GC–MS) techniques

Bio-oil obtained from pyrolysis is highly complicated mixture with valued chemicals. In order to reduce the complexity for unambiguous characterization of components present in bio-oil, solvent extractions using different solvents with increasing polarity have been adopted. The fractions have been analyzed by Fourier transform infrared (FTIR) spectroscopy for identifying the functional groups and Gas chromatography-mass spectrometry (GC-MS), for detailed characterization of components present in various fractions, thereby providing in-depth information at molecular level of various components in bio-oil. This paper reveals the potential of the analytical techniques in identification and brings out the similarities as well as differences in the components present in the bio-oil obtained from two non-edible oil seed-cakes, viz., Jatropha and Karanjia.

Quality Control Aspects: A Simple Method for Estimation of Ethyl Alcohol in Oxy Diesel by NMR Spectroscopy

A direct and rapid method for the estimation of ethyl alcohol in oxy diesel based on NMR (1H, 13C) spectroscopic techniques has been developed. The estimation has been carried out by the methods (a) based on the determination of average group molecular weight (GMW) of the diesel and alcohol and (b) with precalibration of quantitative alcohol-diesel blends. Both the methods are independent of source, type, and nature of diesel (conventional, hydrocracked, hydrodesulfurization) produced by any of refinery processes. The precalibration method requires the use of standards for calibration, where as the GMW method does not require any. The methods have been tried on alcohol-diesel blends in the range of 1.0–10.0% w/w and will be applicable for quality control purposes in blending plant. The statistical treatment of theoretical and estimated values have shown excellent correlation (R 2 = .99). The effects of the spectral interference of emulsifier and coupler, which are added to emulsify the blends, on the chemical shift of alcohol signals in the 1H/13C-NMR spectra have also been studied.