Showing papers by "Umer Rashid published in 2023"

Sulphonated cellulose-based carbon as a green heterogeneous catalyst for biodiesel production: Process optimization and kinetic studies

Abstract: We report, the catalytic application of sulphonated cellulose based solid carbon catalyst for conversion of oleic acid to methyl oleate-biodiesel production under microwave irradiation. Oleic acid, being one of the most widely found fatty acids in plant oils and animal fats; it was utilized as a model substrate to produce biodiesel in this study. The effect and interaction of four independent factors such as methanol to oleic acid molar ratio (MOMR), time, catalyst loading, and temperature were investigated using response surface methodology (RSM). After doing the thirty experiments given by the central composite design (CCD), the optimized reaction condition using RSM was found to be MOMR of 21:1, 60 min, 8 wt % catalyst loading, and temperature of 80 °C that predicted 96.77% biodiesel yield under microwave irradiation, whereas, 97.6 ± 0.2% yield was observed experimentally. The kinetic study of the esterification reaction showed that it followed a pseudo first order reaction. The activation energy of the esterification was found to be relatively low at 49.19 kJ mol−1. The catalyst showed good recyclability when explored up to the 5th reaction cycle. The SEM analysis of the recycled catalyst showed its stability for at least 5 reaction cycles. Therefore, it can be promoted for sustainable production of biodiesel due to its moderate preparation method, good catalytic efficiency, and excellent recyclability.

Selective Synthesis of Renewable Bio-Jet Fuel Precursors from Furfural and 2-Butanone via Heterogeneously Catalyzed Aldol Condensation

Abstract: This study aims to synthesize α,β-unsaturated carbonyl compounds with branched structures via aldol condensation of furfural and 2-butanone using magnesium–aluminum (MgAl) mixed oxides as heterogeneous acid–base catalysts. Regarding the molecular structure of 2-butanone, there are two possible enolate ions generated by subtracting the α-hydrogen atoms at the methyl or methylene groups of 2-butanone. The branched-chain C9 products, derived from the methylene enolate ion, can be applied as bio-jet fuel precursors. The most suitable catalyst, contributing the highest furfural conversion (63%) and selectivity of the branched-chain C9 products (77%), is LDO3, the mixed oxides with 3:1 Mg:Al atomic ratio, with a high surface area and a large number of medium basic sites. The suitable reaction conditions to produce the branched-chain C9 ketones are 1:5 furfural:2-butanone molar ratio, 5 wt.% catalyst loading, 120 °C reaction temperature, and 8 h reaction time. Additionally, this study investigates the adsorption of 2-butanone onto a mixed oxide using in situ Fourier transform infrared spectroscopy; the results of which suggest that the methylene enolate of 2-butanone is the likely dominant surface intermediate at elevated temperatures. Accordingly, the calculation, based on density functional theory, indicates that the methylene enolate ion of 2-butanone is the kinetically favorable intermediate on an MgO(100) as a model oxide surface.

Extraordinary Electrical Conductance of Non-conducting Polymers Under Vibrational Strong Coupling

Abstract: Achieving vibrational mode selectivity to control molecular properties is a challenging task that has become greatly facilitated by vibrational strong coupling. Here we show that strongly coupling the vibrational transitions of polystyrene (PS) and poly (benzyl-methacrylate) (PBMA) to the vacuum electromagnetic field of the cavity enhances the electrical conductance by several orders of magnitude. Remarkably, the extraordinary enhancement of electrical conductance in PS is mode-selective to the vibrational strong coupling (VSC) of the aromatic ring out-of-plane bending transitions corresponding to B2 symmetry. The delocalized hybrid light-matter states formed under VSC could promote extended vibronic coherence, enhancing the electrical conductance. These experiments are done without any light excitation, demonstrating the role of electromagnetic vacuum fluctuations in controlling the long-range coherent transport in molecular materials.

Mild Dealumination of H-ZSM-5 Zeolite for Enhanced Conversion of Glucose into 5-Hydroxymethylfurfural in a Biphasic Solvent System

Abstract: Transformation of lignocellulosic biomass into high-value chemicals is a viable strategy for sustainable development of a bio-based economy. 5-Hydroxymethylfurfural (HMF) is one of potential platform bio-chemicals for the manufacture of various renewable products. In this work, a commercial H-ZSM-5 zeolite was used as a starting material for preparing a series of acid catalysts with bifunctionality for direct dehydration of glucose to HMF in a biphasic water/tetrahydrofuran system. The pristine H-ZSM-5 was mildly dealuminated by refluxing with dilute nitric acid solutions to adjust its acid properties. Although the acid treatment slightly altered the elemental composition, textural properties, and morphology of zeolite, the total acidity and distribution of acid sites were significantly modified. Some non-framework aluminum (Al) oxide clusters were removed from the parent H-ZSM-5 simultaneously with a partial hydrolysis of zeolitic framework. An increased fraction of coordinatively unsaturated framework Al species enhanced the number of Lewis acid sites. Using 0.1 M solution in the treatment provided the suitable catalyst (0.1DeAl.H-ZSM-5), giving a glucose conversion and HMF yield of >99% and 64.7%, respectively, and a good reusability under the optimized reaction conditions. These results show the industrial potential of the proposed method for simple but efficient preparation of H-ZSM-5 catalysts for producing HMF via the catalytic dehydration of glucose.

Characterization of Ash from Sugar Palm [Arenga Pinnata (Wrumb) Merr.] Fiber for Industrial Application

Abstract: ABSTRACT Sugar palm (Arenga Pinnata) fiber is abundant in Malaysia which necessitates its utilization as a source of agricultural waste for industrial development. This paper aims at characterizing the sugar palm fiber to explore its silica content as a potential renewable material. The sugar palm fiber was carbonized, and the ash obtained was characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) and field emission scanning electron microscope (FESESM). The presence of amorphous silica (SiO2) with an average particle size of 41.25 nm was revealed by X-ray diffraction. Fourier transform infrared spectroscopy indicated the presence of functional groups such as silane and siloxane groups, and thermogravimetric analysis and differential scanning calorimetry identified the main degradation stages of the sugar palm fiber ash, and the decomposition of hemicellulose, lignin, cellulose, and carbonate to other oxides. The energy dispersive spectroscopy of the sugar palm fiber ash confirmed silica to be of the highest amount than other elements. Sugar palm fiber ash has been found as a possible silica substitute and a prospective industrial resource.

Dithienylethene-Based Single Molecular Photothermal Linear Actuator.

Abstract: By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, Open form (compressed, UV OFF) and Closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.