Why are high pressures expensive

Catalysts do not change the equilibrium concentrations of reacting substances in reversible reactions. However, they do reduce the time taken to reach equilibrium. Iron is a cheap catalyst used in the Haber process. It helps to achieve an acceptable yield in an acceptable time.

State three reaction conditions that are controlled in industrial reactions. Temperature, pressure, and the use of a catalyst. The Contact process is one of the stages involved in the manufacture of sulfuric acid. Sulfur dioxide reacts with oxygen to make sulfur trioxide:. This means it moves to the left in the Contact process.

Due to the Haber process being a reversible reaction, the yield of ammonia can be changed by changing the pressure or temperature of the reaction. When choosing the conditions for the Haber process, it is important to consider all the factors that affect the yield of the ammonia along with the rate of reaction and the overall cost of production.

You must be able to explain why the following reaction conditions were chosen. The iron catalyst that is used to increase the rate of reaction will eventually stop working effectively. However, a comparison of electrolyser efficiency does not capture the additional process requirements for each electrolyser, such as a bank of batteries to keep electrolysers operating continuously with intermittent renewable energy. Other technologies still in the earlier stages of development TRL 1—4 for the production of hydrogen from renewable sources include biomass gasification, biological fermentation and photolysis , photoelectrochemical, and thermochemical.

Gasification is a mature process adopted widely with coal as a feedstock and fermentation is a well-known biological process, but the process requirements to implement each technique on a commercial scale — particularly with CO 2 capture — are not fully developed.

Photoelectrochemical, biological photolysis, and thermochemical approaches split water to produce H 2 and O 2 with either light exciting a semiconductor in contact with a catalyst, light exciting natural photosynthetic pathways, or high temperatures with assisting reagents, respectively.

All of these techniques are still in the early development stages to overcome low energy efficiencies and process engineering. Due to the immediate availability of alkaline and PEM electrolysers as compared to other hydrogen production technologies, electrolysers will be the only hydrogen technology considered in the remainder of the analysis concerning innovations to the HB loop. However, in the future one should consider their associated environmental impacts such as metal extraction for the catalysts and water usage.

The configuration of the Haber Bosch ammonia synthesis loop has been practically unchanged for the past years in terms of reactor, separation and recycle. Fritz Haber laid the foundation for high pressure catalytic ammonia synthesis and passed the concept to Carl Bosch after partnering with BASF, where his assistant at the time, Alwin Mittasch, discovered the multiply-promoted iron catalyst very similar to those used today.

Instead, most process improvements have resulted from technological enhancements of the unit operations or changes in feedstocks as shown in Fig. While the discovery of wustite iron catalyst as a replacement for magnetite iron catalyst has allowed for reaction pressures down to bar, its associated recycle and feed compression costs are still considerably high.

A number of efforts have been reported on decreasing the pressure of the NH 3 synthesis reactor. While running the NH 3 synthesis reactor at moderate pressures 20—30 bar would resolved this separation issue, the overall energy and capital costs would be considerably higher than in the conventional high pressure system both methane-fed or electrically driven as shown in Fig. The high non-linearity of compression energy with pressure ratio makes favourable the high pressure system where a higher single-pass conversion is achieved, subsequently decreasing the recycle size and refrigeration duty.

A completely new way of approaching this challenge is to replace the separation of ammonia by condensation with absorption in crystalline salts e.

However, the use of absorption for ammonia separation has opened the door to moderate pressure 20—30 bar HB synthesis loop, 58 where condensation currently fails, as well as a wider use of more active catalysts e.

On the other hand, the overall capital costs are even lower than the HB systems using condensation both methane-fed and electrically driven. By increasing the pressure to bar, the capital cost increases due to the additional compressors required, but the energy loss decreases because the temperature change for regeneration decreases as the reaction equilibrium pressure of ammonia increases. On the other hand, decreasing the pressure to 1.

For this reason, no development has been done at such low absorption pressures. Based on this, we can conclude that the current HB loop process is limited by the ammonia separation process and future innovation should focus on the replacement of condensation by absorption for the ammonia separation in the synthesis HB loop. Absorber development is still in early development and optimisation of the conditions of absorption, regeneration and stability should concentrate the attention in the near future.

High temperature ammonia absorption would enable an even more exciting opportunity by the integration of the ammonia synthesis and separation in a single-stage, although the technology is still in its early development.

The first case has lower capital costs but requires more energy for heating, while the second case requires more capital for compressors but uses less energy, as shown in Fig. Nevertheless, both cases require significantly less capital than the high pressure electric HB process because in situ separation removes equilibrium limitations eliminating the need for recycle and allowing low pressure synthesis, while a heater for regenerating the absorbent is of negligible capital.

These benefits will trigger new research avenues in the catalysis field severely diminished during the last decade , reactor design and process engineering. The main novelty of this recently proposed technology , low TRLs stems from simply combining two processes catalytic reaction and absorption that are technologies known to work independently. In addition to the capital cost estimates for some of the major process equipment shown in Fig. In general, processes with chains of high pressure compressors, extensive heat integration, and sensitive catalysts are unable to operate outside steady-state and will require a large storage of hydrogen and electricity.

Therefore, it is expected that the low-pressure 20 bar process with absorption and the in situ separation 3 bar process will significantly decrease the necessary temporary hydrogen storage through fewer compressors and less heat integration. Indeed, new catalyst implementation in a low pressure process may also result in less catalyst sensitivity compared to the current iron-based catalysts.

Therefore, in addition to simplifying the equipment directly related to the HB process, modifications to the HB process are expected to decrease the equipment required to interface the process with renewable energy. The directions to optimise and enable distributed Haber—Bosch ammonia production systems identified in Fig. Direct electrochemical synthesis of ammonia from H 2 O and N 2 is often presented as an attractive alternative due to its low-temperature and low-pressure conditions, and has even begun to have a market presence, 69 but has significant difficulties with selectivity and throughput that need more research and development TRL 3—6.

Other technologies for ammonia synthesis include non-thermal plasma TRL 1—3. In this case, even though the theoretical minimum energy consumption is half that of the HB process, 88 studies to date require energy consumptions around times higher than the conventional methane-fed HB process 87 making it unfeasible for larger scale applications.

Another alternative is based on using the pre-existing efficiencies of the nitrogenase enzyme in microbes, which requires energy consumption in the form of ATP approximately two-thirds that of the conventional methane-driven HB process. Nevertheless, replicating the chemical conditions of the nitrogenase enzyme through metallocomplexes TRL 1—3 to stimulate nitrogen fixation under ambient conditions has emerged as another avenue.

Still, the current energy requirements to synthesize the reducing agents and proton sources are an order of magnitude higher than the HB process in addition to the substantial amounts of organic solvent based waste produced similar order of magnitude than pharmaceuticals, E -factor: 25— Fertilizers, of which ammonia is a major component, have been the cornerstone of increased agricultural yields in developed countries and has prompted the development of an ammonia infrastructure that is suboptimal under certain conditions.

Note: This is a bit of a simplification! When the gases from the reactor are cooled, then excess steam will condense as well as the ethanol. The ethanol will have to be separated from the water by fractional distillation. All the sources I have looked at gloss over this, so I don't have any details. I assume it is a normal fractional distillation of an ethanol-water mixture. The equation shows that the ethene and steam react 1 : 1. In order to get this ratio, you would have to use equal volumes of the two gases.

Because water is cheap, it would seem sensible to use an excess of steam in order to move the position of equilibrium to the right according to Le Chatelier's Principle. In practice, an excess of ethene is used. This is very surprising at first sight. Even if the reaction was one-way, you couldn't possibly convert all the ethene into ethanol. There isn't enough steam to react with it.

The reason for this oddity lies with the nature of the catalyst. The catalyst is phosphoric V acid coated onto a solid silicon dioxide support. If you use too much steam, it dilutes the catalyst and can even wash it off the support, making it useless.