Carbon black grades, production processes

The furnace black process is currently the most important production process. It accounts for more than 95 % of the total worldwide production. The advantages of the furnace black process are its great flexibility in manufacturing various grades of carbon black and its better economy compared to elder processes. The following comparison makes this apparent for similar grades of carbon black, the production rate of one flame is ca. 0.002 kg/h for channel black, ca. 0.2 kg/h for gas black, and ca. 2000 kg/h for a modern furnace black reactor. However, in spite of the more advantageous furnace black process, the production processes listed in Table 27 (except for the channel black process) are still in use for the production of special carbon blacks which cannot be obtained via the furnace black process. 

Table 6.4 Grades, production processes, selected properties and uses of carbon black.

A number of processes have been used to produce carbon black including the oil-furnace, impingement (channel), lampblack, and the thermal decomposition of natural gas and acetjiene (3). These processes produce different grades of carbon and are referred to by the process by which they are made, eg, oil-furnace black, lampblack, thermal black, acetylene black, and channel-type impingement black. A small amount of by-product carbon from the manufacture of synthesis gas from Hquid hydrocarbons has found appHcations in electrically conductive compositions. The different grades from the various processes have certain unique characteristics, but it is now possible to produce reasonable approximations of most of these grades by the od-fumace process. Since over 95% of the total output of carbon black is produced by the od-fumace process, this article emphasizes this process. 

Erom World War I to World War II the channel black process made most of the carbon black used worldwide for mbber and pigment appHcations. The last channel black plant in the United States was closed in 1976. Operations stiU exist and are even being expanded in Europe. The demise of channel black was caused by environmental problems, cost, smoke pollution, and the rapid development of od-fumace process grades that were equal or superior to channel black products particularly for use in synthetic mbber tires. 

Table 11 Hsts the types and appHcations of special pigment-grade carbon blacks. Included in this Hst are thermal black and lampblack. Over 40 special black grades have been developed based on the furnace process having a broad range of surface areas, from 20 m /g to over 1500 m /g. The lower surface area products are used in printing inks and tinting. The high area, more expensive products find use in high color enamels and lacquers.

Both types of surface oxides are found on technical products. Rubber grade carbon blacks are produced in different processes. Channel blacks are made by cooling a flame on iron plates, the so-called channels. The resulting carbon blacks are acidic in character because an excess of air is present (25). In the production of furnace blacks, the fuel, mostly oil or natural gas, is burned with a limited supply of air. Thermal blacks are obtained by thermal cracking of the gas, which sometimes is diluted with hydrogen. In consequence, both types show weakly basic reaction in aqueous suspension. 

The increasing demand led to new production processes. The most important process today is the furnace black process. It was developed in the United States in the 1930s and substantially improved after World War II. It is a continuous process, which allows the production of a variety of carbon black types under carefully controlled conditions. Nearly all rubber grades and a significant part of pigment-grade carbon blacks are now manufactured by the furnace black process. Nevertheless, other production processes, such as gas black, lamp black, thermal black, and acetylene black processes, are still used for the production of specialties. 

Electrical Conductivity. The electrical conductivity of carbon blacks is inferior to that of graphite, and is dependent on the type of production process, as well as on the specific surface area and structure. Since the limiting factor in electrical conductivity is generally the transition resistance between neighboring particles, compression or concentration of pure or dispersed carbon black, respectively, plays an important role. Special grades of carbon black are used to donate to polymers antistatic or electrically conductive properties. Carbon blacks with a high conductivity and high adsorption capacity for electrolyte solutions are used in dry-cell batteries. 

In the past decades the rapidly expanding automobile industry required increasing numbers of tires with various characteristics. This led not only to the development of new rubber grades, but also to the development of new carbon blacks required by the increasingly refined application processes and to the development of a new and better manufacturing process, the furnace black process. Unlike the old channel black process, this process allows the production of nearly all types of carbon black required by the rubber industry. It also meets the high economic and ecological requirements of our times. 

Battery grade carbon blacks produced by a specially designed partial combustion process include the ENSACO/SUPER P carbon black and the by-products of the Shell gasification process, known as Ketjen Black.74 78... 

In 1968 Mantell (28) described several processes for the production of carbon black. He also lists 24 distinct grades of blacks identified by their respective particle diameters (average), surface area and oil absorption (structure). These include the then common grades of channel black, gas furnace blacks, oil furnace blacks, thermal blacks, lampblack, and acetylene blacks, in language sufficient for the manufacturer to identify each grade by these three variables. 

The Oil-Fumace Process has superior efficiency and economy. It is also the most versatile process, allowing production of most grades important for industry. Table 2.1 outlines differences between carbon blacks manufactured in five processes. 

Most processes in the fine chemical industry are typically carried out in batch mode, where the powdered catalyst is suspended in the reaction medium. For the production of bulk chemicals extruded or granulated carbon-supported catalysts are used in fixed-bed reactors. To date, the most important carbon supports from an industrial point of view is activated carbon and carbon black. The main reason for the success of those materials is their commercial availability and variety of different grades, so that the final calalyst can be lailored to the end user s requirements. On a worldwide basis, 908,000 metric tons of activated carbon was produced in 2005 [5], Only a small fraction of that is used as catalyst support. Other carbon supports, such as carbon aerogels and carbon nanotubes, are in the focus of modem catalytic research but so far have not been used in commercial processes. Since there are various scientific pubhcations in the field of carbon and its use as catalyst support, the focus of this contribution is on the industrial importance of carbon supports for precious metal powder catalysts, their requirements, properties, manufacturing, and industrial applications. 

Carbon black might be described as an ideal universal additive it can provide pigmentation, reinforcement, ultraviolet shielding, and anti-static properties -but always provided that the final colour is black. It is used in several different forms, produced by different production processes for its various applications. There are about 100 different grades today, each of which Is matched to an individual application. In thermosetting resins, most carbon blacks tend to inhibit cure and should be avoided. 

The furnace process involves spray injection of a low end fraction of crude oil into a heated chamber. The temperature, shape of the iujectors of the oil, rate of injection, shape of the reactor, and other factors are controlled to produce carbon black fillers of different particle sizes and structures. The particle size and structure control and the reinforcing character of carbon black are the bases of their classification system (Table 8). There are approximately 30 common grades of carbon black used iu the rubber iudustiy. There are also numerous specialty grades produced for use in plastics, conductive applications, and proprietary grades produced for use in tires and other special-purpose products (14). 

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