Reaktor Membran untuk Reforming Metanol

Sumber : Majari

Reaktor membran adalah sistem reaktor baru yang mengkombinasikan pemisahan dengan membran dan reaksi kimia. Reaktor membran memiliki dua tipe, yaitu reaktor membran packed-bed dan reaktor membran katalitik. Reaktor membran dengan katalis packed-bed memiliki area pemisahan yang terpisah dari area reaksi, sedangkan pada reaktor membran katalitik, reaksi dan pemisahan terjadi secara simultan. Membran dalam reaktor ini merupakan penghalang yang hanya dapat melewatkan komponen tertentu. Selektivitas pada membran ini dikontrol oleh ukuran diameter pori membran.


Membran Reaktor

Pada reaktor membran, kombinasi reaksi dan pemisahan dilakukan untuk meningkatkan konversi. Salah satu produk hasil reaksi dipisahkan dari reaktor melalui membran. Hal ini akan menyebabkan kesetimbangan reaksi bergerak ke kanan (menurut Prinsip Le Chatelier), sehingga produk yang dihasilkan semakin banyak.

Membran reaktor banyak digunakan pada reaksi dehidrogenasi (misalnya reaksi dehidrogenasi etana). Pada reaksi ini, hanya salah satu produk, yaitu hidrogen, yang cukup kecil sehingga dapat melewati membran. Hasilnya, desain yang lebih padat dan konversi yang semakin tinggi membuat reaktor tipe ini menunjukkan proses yang lebih efisien. Pemisahan produk akan meningkatkan waktu tinggal untuk volume reaktor yang digunakan sehingga membawa reaksi yang terbatas pada kesetimbangan semakin mendekati penyelesaian reaksi.

Keuntungan yang lebih jauh lagi, reaktor membran dapat meningkatkan rentang temperatur dan tekanan yang diperbolehkan untuk reaksi. Reaktor membran secara fundamental mengubah ketergantungan konversi reaksi dekomposisi fasa gas terhadap tekanan sehingga reaksi lebih disukai jika dilakukan pada tekanan tinggi daripada tekanan rendah. Kondisi tekanan tinggi akan membutuhkan ukuran reaktor yang lebih kecil dan pemurnian yang lebih efisien. Reaktor membran juga berguna bagi reaksi endotermik dan eksotermik yang berurut, dengan menggunakan ekstraksi produk untuk meningkatkan perpindahan panas. Hasilnya adalah reaktor yang lebih kecil, biaya yang lebih rendah, dan reaksi samping yang lebih sedikit.

Salah satu penerapan reaktor membran adalah reaksi reforming metanol yang dapat digunakan sebagai sumber hidrogen untuk fuel cell. Reaksi yang terjadi adalah:


CH3OH + H2O –>3H2 + CO2 (1)

Reaksi ini dapat dimodelkan oleh dua tahap reaksi: reaksi perengkahan endotermik irreversible, dimana satu mol metanol dikonversi menjadi tiga mol produk:


CH3OH –>2H2 + CO (2)

dan diikuti oleh water gas shift reaction,


CO + H2O –> H2 + CO2 (3)

yang merupakan reaksi eksotermik dan terbatas pada kesetimbangan.

Kedua reaksi ini biasanya dilakukan pada reaktor aliran sumbat menggunakan katalis tembaga-seng oksida dan diikuti oleh reaksi pemurnian, yaitu oksidasi parsial untuk memisahkan CO yang tak bereaksi. Tanpa reaktor membran, persyaratan kondisi pemanasan dan tekanan pada proses ini menjadi sulit, karena memerlukan reaktor yang besar dan daerah pemanasan yang signifikan. Jika mungkin, reaksi 2 akan berlangsung pada tekanan dan temperatur tinggi untuk mempercepat reaksi dan meningkatkan penggunaan katalis. Selain itu, karena reaksi ini sangat endotermik, temperatur yang digunakan harus sangat tinggi dan panas harus diberikan sepanjang reaktor.


Reaktor Membran untuk Konversi Methanol

Secara kontras, temperatur dan tekanan yang rendah justru dibutuhkan untuk menjalankan reaksi 3 karena reaksi ini bersifat eksotermik. Panas harus dihilangkan antara tahap ini dan tahap akhir, atau di sepanjang reaktor pada bagian reaksi ini. Reaksi seperti ini umumnya menggunakan pemanas internal untuk reaksi 2 dan tiga alat penukar panas eksternal yang memanaskan umpan dan menghasilkan pendinginan antar tahap pada reaksi 3. Tekanan rendah yang digunakan untuk menjalankan reaksi 3 menyebabkan kedua reaksi harus dilaksanakan pada tekanan rendah, di bawah 100 psi. Akibatnya, reaktor yang digunakan menjadi lebih besar daripada reaktor pada kondisi tekanan tinggi. Secara otomatis, biaya peralatan pun meningkat.

Salah satu reaktor membran yang sedang diteliti untuk digunakan pada reaksi konversi metanol ditunjukkan oleh gambar di samping kanan ini. Metanol dan air masuk melalui bagian bawah annulus luar dan diuapkan menggunakan panas yang didapat dari pendinginan produk hidrogen dan shift reaction. Uap ini akan bergerak ke bagian atas. Pemanasan lebih lanjut pada reformer dilakukan dengan pembakaran gas rafinat.

Beberapa inci pertama dalam reaktor tersebut merupakan area dekomposisi, yaitu area saat metanol dikonversi menjadi CO dan H2 dengan reaksi 2. Reaksi ini diikuti oleh daerah tempat terjadinya reaksi water-gas shift. Seperti yang sudah disebutkan, pemisahan hidrogen membantu melaksanakan reaksi pada tekanan tinggi dengan menjaga tekanan parsial hidrogen di bawah tekanan parsial karbon monoksida dan air. Pembakaran gas buangan juga meningkatkan efisiensi keseluruhan saat memisahkan sisa CO. Dengan membran yang sesuai, unit ini akan menghasilkan hidrogen yang lebih murni daripada hidrogen yang dihasilkan oleh oksidasi parsial.


Sumber:
1. Robert Buxbaum: Membrane Reactors, Fundamental and Commercial Advantages, e.g For Methanol Reforming.
2. Tatang H. Soerawidjaja: Slide kuliah Sel Tunam
3. http://www.engin.umich.edu

Newly Discovered Microbe Allows Treatment of Toxic Melamine Waste

Japan's National Institute for Agro-Environment Sciences (NIAES) and Kowa Co., a major Japanese pharmaceutical company, announced on March 27, 2009, that they had discovered a new soil microorganism that efficiently decomposes melamine. While it is a widely used industrial chemical mass-produced to make resins and finishes, it is feared that exposure to melamine may cause serious health problems.

In recent years, recycling of industrial waste from factories has been promoted to establish a recycling-oriented society. In industrial waste containing paint, however, a lot of melamine still remains, so it is essential to completely decompose the hazardous melamine and cyanuric acid, a byproduct of the hydrolysis of melamine, in order to neutralize and recycle the waste.

The newly discovered bacterium decomposes melamine into cyanuric acid, which is then completely decomposed using a simazine-degrading bacterium possessed by NIAES.

The combination of these two steps is expected to underlie the development of technologies to decontaminate and bioremediate the environment if polluted by melamine and cyanuric acid, and to promote the recycling of industrial waste containing melamine.

National Institute for Agro-Environment Sciences official website
http://www.niaes.affrc.go.jp/index_e.html

Lubricant Oil from Waste Plastic

Do you know if a later time used plastic bottles can be used as a raw material for making lubricant for motor vehicles? If not, check it at the Stephen J. Miller, Ph.D., a scientist and senior research consultant at Chevron. Together with colleagues in the Center research Chevron Energy Technology Company, Richmond, California, United States and the University of Kentucky, he succeeded in changing waste plastic into oil lubricants. How?

Most of the population in the world using the plastic in the running activities. According to Environmental Protection Agency (EPA) United States, in 2001, the United States use at least 25 million tons of plastic each year. Not yet added user plastic in other countries. Not a surprise if a lot of plastic used. Plastics have many advantages compared to other materials. In general, the plastic has a low density, is isolation of the electrical, mechanical strength is varied, limited temperature resistance, and durability of chemicals that vary. In addition, the plastic is also lightweight, easily in the design, and cost of making cheaper.

Unfortunately, behind all the benefits, waste plastic cause problems for the environment. The nature of plastic is not another that can not be described in the land. To overcome this problem, environmental experts and scientists from various disciplines have conducted various research and action. One way to recycle plastic waste. However, this is not too effective. Only about 4%, which can be recycled, the rest in the shelter menggunung waste. Can piles of plastic waste can be converted into lubricant? Problems that underlie Miller and colleagues conducted this research.

Most people use a plastic type of plastic is polietilena. There are two types of polietilena, namely high density polyethylene (HDPE) and low density polyethylene (LDPE). HDPE is used more as plastic beverage bottles, while for LDPE plastic bags. In research to be published in the Journal of the American Chemical Society Fuel and Energy (Energy and Fuel) edition of July 20, 2005, Miller polietilena heating method using pirolisis, and investigate the results of heating the substance. In fact, when heated will polietilena a compound liquid hydrocarbons. Compound has a similar form of wax (wax).

A large plastic straggling is about 60%, a number of the quite a lot. Chemical structure of the compound liquid hydrocarbons similar wax allow this to be processed into high-quality lubricant. Just enough information, the lubricant that is currently circulating in the market derived from processing petroleum. Crude oil (crude oil) of oil drilling in the bottom of the earth compound contains various hydrocarbons with boiling point is different. Then, various compound hydrocarbons in the crude oil is separated using a multistage distillation techniques (distillation) based on the difference didihnya point.

Besides fuel, like gasoline, diesel, and kerosene, crude oil distillation also produces oil lubricants. Nature of chemical compound from the liquid hydrocarbons heating waste plastic compound similar to hydrocarbons in the crude oil so that it can be processed into oil lubricants. Changing the liquid hydrocarbons pirolisis plastic waste into oil using a method hidroisomerisasi lubricants. Miller hopes this artificial lubricant can be used for vehicles with the same quality with the distillation of petroleum crude oil, environmentally friendly, and economical. In fact, the oil business of making synthetic liquid hydrocarbons from the compound, this is not a new thing.

In the early 1990s, the company Chevron has been trying to change the compound liquid hydrocarbons into synthetic fuel for commercial purposes. The only raw material used to produce a compound liquid hydrocarbons derived from natural gas (generally gas metana) katalitik through a process known as the Fischer-Tropsch process. In the Fischer-Tropsch process, the gas metana converted into synthesis gas (syngas), which is a mixture of hydrogen gas and carbon monoxide, with the help of iron or cobalt as catalyst. Furthermore, the syngas is converted into liquid hydrocarbons compound, and then processed using hydrocracking process into fuel and other petroleum products, including the lubricant. Compound liquid hydrocarbons from syngas conversion results have the same chemical nature of the polietilena. Natural gas used came from the United States. Later, the sea area offshore the Middle East are a source of natural gas because the price of natural gas there is cheaper. Lubricant oil from natural gas for a while this can be an alternative lubricant to petroleum processing results. In the future, natural gas reserves in the world will soon diminish. On the other hand, the need for the higher lubricant.

Now, with the discovery of this, the making of lubricant does not appear to need more natural gas. Simply use the waste plastic bottles, the oil lubricant. Interested in trying?

Source: http://acswebapplications.acs.org Ket: Both writers are alumni of Department of Chemistry FMIPA Padjadjaran University and Community pegiat in Alchemist.

Domestic Waste Water Processing Using Enceng Gondok

The process that occurs in the system wet land made for domestic waste water treatment is the process of physics, chemistry and biology due to the interaction between microorganisms, plants and substrate.

Which plays an important role in this process is the process of respiration and photosynthesis performed by plants, water. This plant is able to suck oxygen from the air through the leaves, stem, root and rhizomanya who then released again. Plants that are used to process domestic waste water in this research is the water hyacinth.

Plants planted this half of the broad area of surface reactor. Waste water is treated domestic waste water is channeled from the channel domestic waste water disposal in the Village Tlogomas Municipality of Malang in East Java. Berdiameter the gravel between 3 - 4 mm placed in a reactor with a height of three-quarters of the reactor depth. All walls and dibeton bed reactor with 20 cm thickness. Domestic waste water channeled from the channel domestic waste water disposal to the Inlet reactor continuously, and after the processing in the reactor is filled with sand and planted with water hyacinth, and exit from the outlet. Debit bait waste water = 9.29 m3/hari, Volume = 58.824 m3 reactor, Volume = 29.412 m3 liquids, stay time = 3.17 days.

Sampling is done at the Inlet and outlet reactor. Parameter analysis is performed:

1. T-N (spektrofotometri method),
2. T-P (spektrofotometri method),
3. COD (closed reflux method),
4. TSS (gravimetri method) and pH (pH meter).
5. TSS value outlet average 180 mg / l, is below the required standard of quality that is 200 mg / l.
6. Average efficiency of 31.7% TSS. Total P-value outlet average 0.8 mg / l, still above the required standard of quality that is 0.1 mg / l.
7. Average efficiency of Total-P 42.64%.
8. Total Value-N outlets average 32.5 mg / l, still above the standard quality required is 20 mg / l.
9. Average efficiency of Total-N 52.13%. Outlet COD values average 225 mg / l, still above the value of the required quality standard is 100 mg / l.
10. The average value of COD treatment efficiency of 42.1%.
11. PH value of waste water does not mean that changes in the value ranges between 6 and 8.
12. Time of harvesting crops should be done once a month.

Carbon Dioxid Tranformed Into Methanol

Scientists at Singapore's Institute of Bioengineering and Nanotechnology (IBN) have succeeded in unlocking the potential of carbon dioxide – a common greenhouse gas – by converting it into a more useful product.

In the international chemistry journal Angewandte Chemie, the IBN researchers report that by using organocatalysts, they activated carbon dioxide in a mild and non-toxic process to produce methanol, a widely used industrial feedstock and clean-burning biofuel.

Organocatalysts are catalysts that are comprised of non-metallic elements found in organic compounds. NHCs such as IMes (1,3-bis-(2,4,6 trimethylphenyl)imidazolylidene) are a form of organocatalysts that are stable and easily stored. They do not contain toxic heavy metals and can be produced easily without high costs.

The scientists made carbon dioxide react by using N-heterocyclic carbenes (NHCs), a novel organocatalyst. In contrast to heavy metal catalysts that contain toxic and unstable components, NHCs are stable, even in the presence of oxygen. Hence, the reaction with NHCs and carbon dioxide can take place under mild conditions in dry air.

The IBN scientists showed that only a small amount of NHC is required to induce carbon dioxide activity in a reaction. "NHCs have shown tremendous potential for activating and fixing carbon dioxide. Our work can contribute towards transforming excess carbon dioxide in the environment into useful products such as methanol," said Siti Nurhanna Riduan, IBN Senior Lab Officer, who is also pursuing her Ph.D. under the Scientific Staff Development Award at IBN, one of the research institutes of Singapore's A*STAR (Agency for Science, Technology and Research).

Hydrosilane, a combination of silica and hydrogen, is added to the NHC-activated carbon dioxide, and the product of this reaction is transformed into methanol by adding water through hydrolysis.

Yugen Zhang, Ph.D., IBN Team Leader and Principal Research Scientist, explained, "Hydrosilane provides hydrogen, which bonds with carbon dioxide in a reduction reaction. This carbon dioxide reduction is efficiently catalyzed by NHCs even at room temperature. Methanol can be easily obtained from the product of the carbon dioxide reaction. Our previous research on NHCs has demonstrated their multiple applications as powerful antioxidants to fight degenerative diseases, and as effective catalysts to transform sugars into an alternative energy source. We have now shown that NHCs can also be applied successfully to the conversion of carbon dioxide into methanol, helping to unleash the potential of this highly abundant gas."

Previous attempts to reduce carbon dioxide to more useful products have required more energy input and a much longer reaction time. They also require transition metal catalysts, which are both unstable in oxygen and expensive. Ongoing research at IBN aims to find cheap alternatives for the hydrosilane reagent so that the production of methanol can be even more cost-effective for mass industrial production.

"At IBN, we are innovating effective methods of generating clean energy using green chemistry and nanotechnology. In the face of environmental pollution, global warming and increasing demands on diminishing fossil fuel resources, we hope to provide a viable alternative energy option for industry, and effective sequestration and conversion of carbon dioxide," said IBN Executive Director. Jackie Y. Ying, Ph.D.

Wastewater Treatment Technology Tutorial

Introduction

Earthpace has developed this tutorial to guide users through the wastewater treatment process and to introduce users to current and emerging technologies for wastewater management.

Begin the tutorial by reading the introduction or by clicking on one of the blue titles in the image below to learn more about each wastewater treatment method. You may also use the links to the right to navigate.

Wastewater treatment refers to the process of removing pollutants from water previously employed for industrial, agricultural, or municipal uses. The techniques used to remove the pollutants present in wastewater can be broken into biological, chemical, physical, and energetic. These different techniques are applied through the many stages of wastewater treatment.

Primary treatment usually includes the removal of large solids from the wastewater via physical settling or filtration. The first step in primary treatment is screening.

Secondary treatment typically removes the smaller solids and particles remaining in the wastewater through fine filtration aided by the use of membranes or through the use of microbes, which utilize organics as an energy source. Energetic techniques may also be employed in tandem with biological techniques in the secondary phase to break up the size of particles thus increasing their surface area and rate of consumption by the microbes present. A common first step in the secondary treatment process is to send the waste to an aeration tank.

Tertiary treatment involves the disinfection of the wastewater through chemical or energetic means. Increasing the number of steps in a wastewater treatment process may insure higher quality of effluent; however employing additional technologies may incur increased costs of construction, operation, and maintenance.