Homework No.1
The synthesis gas, after cleanup, can be more efficiently and cleanly burned in a downstream process. Alternatively, the cleaned-up synthesis gas can be used to manufacture a number of different chemicals. After cleanup, the synthesis gas can either be used for power generation or for the production of chemical products such as ammonia, methanol, DME, liquid fuels, and others. A similar technology to CTL (coal to liquids) is the conversion of natural gas-to-liquid fuels (“gas to liquids” or GTL). This also involves the production of fuel from synthesis gas, though in this case, the source of the synthesis gas is partial combustion of natural gas. Typically, the gas comes from “stranded gas” locations, where it cannot be easily utilized or transported by conventional methods. Estimates of known natural gas reserves are increasing as the rate of new discovery of unconventional gas reserves increases.


From the previous discussion, it is clear that synthesis gas can play an important role in the utilization of coal or remote natural gas reserves. Methanol is a key intermediate in this conversion. The overall reaction from methane to synthesis gas to methanol can be represented as:
CH4 + 1⁄2 O2 = CO + 2 H2 -> CH3OH
Synthesis gas is processed over a fixed bed of catalyst forming methanol and water. Two reactor types are most popular: an adiabatic reactor with multiple quenches of cold stream (ICI system) or a multi-tubular reactor with internal heat exchange (Lurgi system). Both types are operated at a temperature range of 200–280°C and low pressure of 5–7 MPa using Cu/ZnO/Al2O3 catalyst.
Methanol Derivatives contains Acetic Acid, Formaldehyde and Olefins. Formaldehyde is an intermediate used in themanufacture of a wide range of products. More than 60 % of it is used in the production of resins, such as urea-formaldehyde, phenol-formaldehyde, and melamine-formaldehyde. Other applications include 1,4-butanediol and polyacetal resins. Formaldehyde is produced by partial oxidation and dehydrogenation of methanol using either silver catalysts (Reuss et al. 2003) or molybdenum oxide catalysts.


Before we discuss ethylene and propylene production from methanol, we must understand the current technologies and the market. Ethylene and propylene are two of the largest volume chemicals produced for the petrochemical industry. Light olefin demand is primarily driven by polyolefin production, but other olefin derivatives such as ethylene oxide, ethylene dichloride, propylene oxide, acrylonitrile, and others consume about 40 % of the light olefins produced today. The majority of the light olefins used for petrochemical applications are produced by the steam cracking of ethane, naphtha, or other gas liquids as shown in the Table 8.


Methanol to Olefins Process contains 2 major process: Lurgi MTP Process and UOP/HYDRO MTO Process.
Lurgi MTP Process


The Lurgi MTP process uses a fixed-bed catalyst manufactured commercially by S€ud-Chemie AG (Lurgi – Generic MTP2003; Wurzel 2006). It provides high propylene selectivity, low coking tendency, low propane yield, and limited by-product formation. Methanol, both fresh and recycle (as recovered from aqueous streams), is the feed to the MTP unit. The methanol is vaporized, superheated, and fed to a DME reactor. The DME reactor is a single-stage adiabatic reactor where most of the methanol is converted to dimethyl ether (DME) on an alumina catalyst. The reaction is exothermic and achieves almost thermodynamic equilibrium.
The product of the DME reactor is sent to three MTP reactors in parallel: two of the reactors are in operation, while a third one is in regeneration or on standby. For the purposes of reaction control, each MTP reactor features six zeolite-based catalyst beds over which the methanol/DME mixture is converted to a mixture of olefins, typically from ethylene to octenes, but such that the carbon distribution peaks at propylene, at an operating temperature of about 450°C and an operating pressure of 0.15 MPa (about 20 psia). Side products from the reaction include naphthenes, paraffins, aromatics, and light ends. The oxygen chemically bound in the methanol results in process water.
UOP/HYDRO MTO Process
The UOP/HYDRO MTO Process can use “crude” methanol, “fuel-grade” methanol, Grade AA methanol, or even DME as feed. The choice of feedstock generally depends on project-specific situations. Figure.1 illustrates a simple flow diagram for the UOP/HYDRO MTOProcess.


The MTO process utilizes a circulating fluidized bed reactor that offers a number of advantages over both fixed-bed reactors and other types of fluidized bed reactors. The circulating fluidized bed reactor provides better mass transfer than bubbling bed fluidized bed reactors as well as better temperature control than riser and fixed-bed reactors, especially given the highly exothermic nature of the methanol-to-olefins reactions. This type of reactor has been widely used in the fluid catalytic cracking (FCC) process units in petroleum refineries.
Constant catalyst activity and product composition can be maintained via continuous regeneration of a portion of used catalyst by coke burning with