Catalytic Conversion of Biomass-derived C1- C3 Compounds to Value-added Chemicals

Abstract

With the demand for energy-efficient and environmentally friendly processes, chemical industries are moving towards the production of bulk and fine chemicals from renewable resources such as biomass. The transition from fossil to renewable resources is necessary to meet the growing demand for clean energy and chemicals while reducing the CO2 emission. This thesis aims to investigate and develop new efficient methods to convert biomass-derived compounds to value-added chemicals using heterogeneous catalysts comprising highly active, selective and stable nanostructured materials. Chapter 1 gives a short description of the challenges with the production of chemicals from non-sustainable sources and introduces biomass-derived chemicals. Furthermore, the chapter presents three biomass-derived platform chemicals, i.e. formic acid, ethanol and acetone, and their potential for production of value-added chemicals. The chapter then addresses the basic concept of heterogeneous catalysis with focus on supported nanoparticles. Furthermore, the chapter highlights how detailed understanding of size, shape and structure can help in the development of new and more efficient heterogeneous catalysts. Chapter 2 deals with the different porous support used in this thesis. The chapter gives a short introduction to zeolites and ordered mesoporous carbon and describes briefly general strategies to improve the efficiency in heterogeneous catalysis. Furthermore, the chapter describes the synthesis methodology of various porous support used in this work. Chapter 3 deals with the major analytical techniques used to characterise catalytic materials. The techniques include: X-ray powder diffraction, nitrogen physisorption, electron microscopy, temperature-programmed desorption, elemental analysis, X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transformation spectroscopy and thermo-gravimetric analysis. Hydrogen holds great promise for resolving the storage of intermittent and highly weather-dependent renewable energy. Chapter 4 describes a novel heterogeneous catalytic system for the continuous production of hydrogen through the decomposition of formic acid. The reaction occurs over a heterogeneous bimetallic catalyst comprising Pd-Au metal nanoparticles encapsulated in zeolite silicalite-1. The chapter describes different methods to support gold on silicalite-1 and identifies an optimum catalyst for the efficient production of hydrogen via decomposition of formic acid. Acetaldehyde is an organic intermediate used commercially as a food preservative and an ingredient in fuels, glues, and caulking compounds. Chapter 5 describes an efficient synthesis of acetaldehyde from the dehydrogenation of ethanol. The reaction occurs over a heterogeneous catalyst comprised of Cu nanoparticles supported on nitrogen-doped ordered mesoporous carbon. The chapter studies the effect of nitrogen doping on the mesoporous carbon support and identifies the optimum catalyst for the synthesis of acetaldehyde. The chapter also investigates the catalytic effect of important synthetic parameters, such as polymerisation and calcination temperature. 1,3-Butadiene is an important chemical intermediate used in synthetic rubber and polymers. Chapter 6 describes a method to synthesise 1,3-butadiene from ethanol using a heterogeneous catalyst comprised of Zn containing zeolite. The chapter describes the effect of the zeolite morphology on butadiene selectivity and ethanol conversion and identifies the optimum catalyst for ethanol to butadiene conversion. Methyl isobutyl ketone (MIBK) is an organic solvent used for the production of gums, paints and varnishes. Chapter 7 describes a novel one-step synthesis of MIBK from acetone at 150 °C and atmospheric pressure in a fixed bed continuous flow set-up. The reaction occurs over a heterogeneous bifunctional catalyst comprised of Pd nanoparticles supported on HZSM-5 zeolite. The chapter describes incipient wetness impregnation and in-situ encapsulation methods to support Pd nanoparticles in conventional and mesoporous zeolite and identifies the optimum catalyst for MIBK synthesis.