C1 Chemistry

Principles and Processes

Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda

• Publisher: CRC Press
• Year: 2022
• Print ISBN: 9781032245621
• eBook ISBN: 9781000593679
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemical & Biochemical Engineering

Volatility of crude oil prices, depleting reservoirs and environmental concerns have stimulated worldwide research for alternative and sustainable sources of raw materials for chemicals and fuels. The idea of using single-carbon atom molecules as chemical building blocks is not new, and many such compounds have been techno-economically studied as raw materials for fuels. Nevertheless, unifying the scientific and technical issues under the topic of C1 chemistry is not as easy as it may appear. C1 Chemistry: Principles and Processes provides a comprehensive understanding of the chemical transformation from molecular to commercial plant scales and reviews the sources of C1 molecules, their conversion processes and the most recent achievements and research needs.

This book:

• 
  
  

• Describes the latest processes developments and introduces commercial technologies

• 
  
  

• Covers a wide range of feedstocks, including greenhouse gases and organic wastes

• 
  
  

• Details chemistry, thermodynamics, catalysis, kinetics and reactors for respective conversions

• 
  
  

• Includes preparation and purification of C1 feedstocks, C1 molecule coupling reactions and process technologies for each C1 conversion reaction

• 
  
  

• Considers environmental impacts and sustainability

This book will be of interest to a wide range of researchers, academics, professionals and advanced students working in the chemical, environmental and energy sectors and offers readers insights into the challenges and opportunities in the active field of C1 chemistry.

1 C₁ Chemistry: An Overview

DOI: 10.1201/​9781003279280-1

1.1 Introduction

Traditionally, the source of organic chemicals and automotive fuels has been petroleum. The related technologies have been developed and optimized in the past century and most of them are demonstrated and approached to the theoretical yields specially in refining. There are, however, concerns regarding the sustainability of these processes.

The first factor is the limited petroleum sources despite discovering new oil reservoirs and improved recovering technologies and economic availability of shale oil. The oil price is highly fluctuating. To attain a profit margin, integration of refining-petrochemical plants has been considered as a solution.

The available crude oils are also becoming increasingly heavier with more heteroatoms (sulfur, nitrogen, metals and oxygen). Their inclusion (or their fractions) in the refinery diet brings about deep conversion challenges (Ramírez-Corredores, 2000). The emission regulations are becoming more stringent for the emission of sulfur and nitrogen compounds. Furthermore, treating of low-quality oil necessitates more advanced and sophisticated technologies in refining.

Another problem is global warming as a result of increased use of fossil fuels in energy production in household and transportation sectors. International efforts (e.g., Kyoto Protocol and Paris Agreement) are underway to reduce greenhouse gas emissions (e.g., CO₂ and CH₄) worldwide. Paris Agreement (end of 2015) goal is limiting global temperature rise well below 2°C above the pre-industrial level. The carbon footprint and lifecycle analysis are, therefore, becoming additional criteria for evaluating the processes, and carbon taxes may impact the economic viability of many conventional processes in the future.

As a consequence, the use of alternative carbon sources for sustainable chemical industry has received much attention.

Biomass-based chemicals and fuels are an alternative. The ultimate source of carbon in biomass is the nature carbon cycle from CO₂ via photosynthesis. A main criterion here is that it should not compete with human food chain directly. Thus, non-edible lignocellulosic (e.g., second-generation biofuels) and wastes should be considered. This will avoid deforestation and use of fresh water for supplying biomass. The main problems with biomass conversion are limited supply, low energy content and difficulties in treatment of the primary products. The development of active catalysts and effective processes is an active research field.

Another approach could be using small carbon-containing molecules as building block for constructing larger molecules. Compared to conventional methods from petroleum which are cracking-based (less selective), this approach provides the opportunity of higher selectivities. The increasing share of natural gas (methane) as a feedstock has been already underway in refining and petrochemical industries.

These small molecules are potentially much more abundant than petroleum and can be produced from a wide variety of sources. Therefore, they offer higher potentials for being used as chemical feedstocks in the future.

1.2 Definition

C₁ chemistry is the chemistry of single-carbon-bearing molecules and their conversion to more valuable intermediate feedstocks, chemicals and clean fuels. This definition could be extended to include certain other small molecules such as dimethyl ether and methyl formate despite having two carbon atoms per molecule (Lee et al., 1990). These compounds lack a C−C bond in their molecules and could be viewed as “condensed” C₁ molecules.

The main source of C₁ molecules is currently natural gas but they can be obtained also from a variety of sources including biomass, organic wastes and coal or even captured carbon dioxide (Roberts and Elbashir, 2003).

An inherent advantage of C₁ feedstocks is that they could be easily purified by conventional methods and that their conversion is source-independent. Methane contains a high ratio of hydrogen; however, carbon oxides (especially CO₂) need a source of (renewable) hydrogen which is a drawback for their use as chemical feedstock.

Successful and sustainable utilization of C₁ molecules as feedstock is a great task in green and sustainable chemistry (Anastas and Zimmerman, 2019).

1.3 C₁ Chemistry Developments and Drivers

Research in C₁ chemistry is a very active and rapidly growing field as illustrated by number of publications for individual processes. Within an interval of about 20 years, the number of publications with subject of chemistry and catalysis of methane, CO and CO₂ shows a fourfold increase from about 3,000 in 1996 to about 12,000 in 2017 according to a Sci-Finder search (Cui et al., 2019).

The quest for national energy independence and the need for carbon-neutral renewable fuels free of S and N have resulted in increased attention to C₁-chemistry-based processes. The development of technologies for the capture and storage of anthropogenic CO₂ and the advent of shale gas renewed attention to C₁ conversions (Galadima and Muraza, 2016). Other non-conventional gas reserves such as vast methane hydrates increase the potential of these processes.

The catalytic conversion of C₁ molecules to useful products is still a challenging task. Many potentially attractive conversion processes including direct conversions of methane and CO₂ to chemicals are still far from scale-up and need further research and development efforts. The principal research areas in C₁ chemistry can be divided into new reactions in C₁ chemistry, development of novel and efficient catalysts and scale-up and process development (Fierro, 1993).

An important step in C₁ chemistry is the formation of carbon backbone of the target molecule. Thus, the mechanism of the formation of the first C−C bond in the process is often an important research topic and still is not well understood in many transformations (Olah et al., 2018). Nevertheless, development of advanced and in-situ characterization techniques (e.g., low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and extended X-ray absorption fine structure (EXAFS) spectroscopy) and theoretical studies (e.g., density functional theory (DFT) calculations) helped to gain better understanding on reaction mechanism and reaction pathways.

Because the formation of a complex molecule from a simple molecule may involve several transformations, many of the catalysts examined for single-step conversion of C₁ molecules are bifunctional or multifunctional catalysts, providing the specific active sites for different individual reactions. This approach promotes the tandem reactions when the initial steps are equilibrium limited. The main challenge here is how to integrate different functionalities within a single catalyst during catalyst preparation. Furthermore, the reactions should need similar operating conditions (e.g., temperature) to achieve acceptable synergies.

Thermodynamic and kinetic coupling of the tandem ...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Dedication Page
• Contents
• Preface
• Authors
• Chapter 1 C1 Chemistry: An Overview
• Chapter 2 C1 Sources
• Chapter 3 C1 Interconversions
• Chapter 4 Methane Conversions
• Chapter 5 Synthesis Gas Chemistry
• Chapter 6 Carbon Dioxide Conversions
• Chapter 7 Methanol Conversions
• Chapter 8 Methane Derivative Routes
• Chapter 9 Outlook and Perspective
• Index