Catalytic Reforming also produces high purity hydrogen for hydrotreating processes.pptx

To convert low-octane naphtha(C7–C10) into a high-octane reformate for gasoline blending (middle severity mode 70% aromatics content) and/or high severity mode to produce mainly aromatics (80–90 vol% (benzene, toluene, and xylene) for petrochemical plants.
- Reforming also produces high purity hydrogen for hydrotreating processes.

1. Catalytic Reforming Process

2. INTRODUCTION

3. Process Objective: - To convert low-octane naphtha(C7–C10) into a high-octane reformate for gasoline blending (middle severity mode 70 % aromatics content) and/or high severity mode to produce mainly aromatics (80–90 vol % (benzene, toluene, and xylene) for petrochemical plants . - Reforming also produces high purity hydrogen for hydrotreating processes. Primary Process Technique: – Reforming reactions occur in chloride promoted fixed catalyst beds. Desired reactions include : dehydrogenation of naphthenes to form aromatics; isomerization of naphthenes ; dehydrocyclization of paraffins to form aromatics; and isomerization of paraffins . Hydrocracking of paraffins is undesirable due to increased light-ends make. polymerization , and isomerization taking place at the same time. Catalytic Reforming Process

4. Process steps: Naphtha feed and recycle hydrogen are mixed, heated and sent through successive reactor beds. Each pass requires heat input to drive the reactions Final pass effluent is separated with the hydrogen being recycled or purged for hydrotreating . Reformate product can be further processed to separate aromatic components or be used for gasoline blending . Typical Yields and Dispositions

5. The typical feed stocks to catalytic reformers are: 1 . Heavy straight-run (HSR) gasolines 2 . Naphthas 82–190°C 3 . heavy hydrocracker naphthas • These are composed of the four major hydrocarbon groups : paraffins , olefins, naphthenes , and aromatics (PONA). • Typical feed stocks and reformer products have the following PONA analyses ( vol %) Feedstocks of catalytic reformers

6. Process description :- 82 -190 C

7. Continuous catalytic reforming(CCR)

8. Desirable reactions in a catalytic reformer all lead to the formation of aromatics and isoparaffins as follows: 1. Paraffins are isomerized and to some extent converted to naphthenes . The naphthenes are subsequently converted to aromatics. 2. Olefins are saturated to form paraffins which then react as in . 3. Naphthenes are converted to aromatics. 4. Aromatics are left essentially unchanged . Reactions leading to the formation of undesirable products include: 1. Dealkylation of side chains on naphthenes and aromatics to form butane and lighter paraffins . 2. Cracking of paraffins and naphthenes to form butane and lighter paraffins . Catalytic Reforming Reactions

9. There are four major reactions that take place during reforming. They are : (1) Dehydrogenation of naphthenes to aromatics (2) Dehydrocyclization of paraffins to aromatics (3) Isomerization ( 4) Hydrocracking The dehydrogenation reactions are highly endothermic and cause a decrease in temperature as the reaction progresses. • The dehydrogenation reactions have the highest reaction rates of the reforming reactions which requires the use of the inter-heaters between catalyst beds to keep the mixture at sufficiently high temperatures for the reactions to proceed at practical rates.

10. Hydrocracking Reactions: Hydrocracking reactions are the main sources of C4 hydrocarbons (C1, C2,C3 and C4). The reactions are highly exothermic and consume high amounts of hydrogen. Cracking results in the loss of the reformate yield. Paraffin hydrocracking:

11. Favorable Conditions for Different Reforming Reactions The dehydrogenation reactions are the main source of reformate product and are considered to be the most important reactions in reforming . These are highly endothermic reactions and require a great amount of heat to keep the reaction going. For this reason three reactors are usually used in the reforming process with heating the product from each reactor before entering the other. The dehydrogenation reactions are reversible and equilibrium is established based on temperature and pressure. In reforming, a high temperature around 500 C (932F) and a low hydrogen pressure are required. The minimum partial pressure of hydrogen is determined by the amount of the desired aromatics conversion .

12. Catalysts of Catalytic Reforming process Most processes use platinum as the active catalyst. Sometimes platinum is combined with a second catalyst (bimetallic catalyst) such as rhenium or another noble metal. Monometallic : ( Pt ), Bimetallic: ( Pt , Rhenium) Acid Activity: Halogens/silica incorporated in alumina base. Metallic Function: It promote dehydrogenation and hydrogenation. It also contribute to dehydrocyclisation and isomerisation . Acid Function: It promotes isomerisation , the initial step in hydrocracking, participate in paraffin dehydrocyclisation .