Advances in CO₂ capture technology: A patent review

Abstract

Carbon dioxide (CO₂) emissions are believed to be a major contributor to global warming. As a consequence, large anthropogenic CO₂ sources worldwide will eventually be required to implement CO₂ capture and storage technologies to control CO₂ emissions. In order to guide the establishment of policies for CO₂ removal, we reviewed the current status of CO₂ capture patents and technologies based on the Espacenet patent database and found that more than 1000 patents have been published on sorbent, solvent, and membrane. More than 60% of these patents were published since the year 2000, and a sharp increase in patent numbers was seen in the last several years; ∼25% patents were published in the last 2 years. Substantially more patents on CO₂ removal and separation technologies are expected in the coming years. Meanwhile, the top four major types of patents, which consist of more than 2/3 of these patents, were patents granted by Japan (JP), United States (US), World Intellectual Property Organization (WO), and China (CN), and approximately half of the patents were JP and US patents. Unfortunately, no current technologies for removing CO₂ from large sources like coal-based power plants exist which satisfy the needs of safety, efficiency, and economy; further enhancement and innovation are much needed.

Introduction

With the rapid development of modern civilization, carbon dioxide (CO₂) is produced in large quantities in industry, for instance, by the combustion of coal, coke, and natural gas, in the fermentation of carbohydrate materials and sugars, in the manufacture of cement and lime, and etc. Indeed, more than 30 billion tons of CO₂ are added to the atmosphere each year. However, the emission of CO₂, one of the major greenhouse gases, has raised great concerns about the relationship between anthropogenic CO₂ and global warming; the emission of CO₂ may have contributed to urban smog, acid rain, and health problems [1], [2]. In another scenario (e.g., a space capsule, a submarine, a subterranean mining environment, or a closed-circuit respiratory apparatus), CO₂ produced by the occupants of a closed ecological system must be removed from air. Therefore, CO₂ removal is of importance. As a result, a variety of methods have been studied and patented for the removal and separation of CO₂ from industrial waste and mine gases, from the air, and from gases produced by animal metabolism, such as human respiration.

Many technical challenges, however, are facing potential large-scale implementation of CO₂ capture in power plants [3]. Fig. 1 presents the simplified pathways of CO₂ production, capture or separation, and storage or re-utilization. Among them, CO₂ capture is the key step economically and has two technology routes: (1) pre-combustion: capture from the reformed synthesis gas of an upstream gasification unit; and (2) post-combustion: capture CO₂ from the flue gas stream after combustion. Upon capture, CO₂ can be stored underground, used for enhancing oil recovery, and as carbon resources to be converted into other useful compounds [4], [5] (Fig. 1). The current technologies for CO₂ capture and separation mainly include solvent, sorbent, and membrane, and the mechanisms for CO₂ capture depend on the chemistry of the capturing approaches or materials. For instance, in the monoethanolamine (MEA) approach, CO₂ is captured based on its interaction with amines to form bicarbonates or carbamates.

During the past few decades, much effort has been devoted to developing new technologies for CO₂ capture, storage, and utilization. Many reviews on this topic are already published in the literature [3], [4], [5], [6], [7]. However, to our knowledge, there is no report on patented innovations on CO₂ capture technology. In order to address the importance of patented innovations, in this article, the current status of patents on CO₂ capture is reviewed. It is noteworthy to mention that clean energy technologies (e.g. solar, wind, nuclear, and proton exchange membrane fuel cell, and hydrogen-based power generation) that can lower CO₂ emission are not discussed here but are very important.